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Papers on global warming detection from global temperature series

Posted by Ari Jokimäki on May 25, 2012

This is a list of papers on global warming detection from global temperature series (i.e. papers that estimate if global warming signal can be statistically significantly distinguished from random noise). The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

UPDATE (July 24, 2013): Foster & Rahmstorf (2011) added.

A Bayesian approach to detecting change points in climatic records – Ruggieri (2012) “Given distinct climatic periods in the various facets of the Earth’s climate system, many attempts have been made to determine the exact timing of ‘change points’ or regime boundaries. However, identification of change points is not always a simple task. A time series containing N data points has approximately Nk distinct placements of k change points, rendering brute force enumeration futile as the length of the time series increases. Moreover, how certain are we that any one placement of change points is superior to the rest? This paper introduces a Bayesian Change Point algorithm which provides uncertainty estimates both in the number and location of change points through an efficient probabilistic solution to the multiple change point problem. To illustrate its versatility, the Bayesian Change Point algorithm is used to analyse both the NOAA/NCDC annual global surface temperature anomalies time series and the much longer δ18O record of the Plio-Pleistocene.” Eric Ruggieri, International Journal of Climatology, DOI: 10.1002/joc.3447.

Global temperature evolution 1979–2010 – Foster & Rahmstorf (2011) “We analyze five prominent time series of global temperature (over land and ocean) for their common time interval since 1979: three surface temperature records (from NASA/GISS, NOAA/NCDC and HadCRU) and two lower-troposphere (LT) temperature records based on satellite microwave sensors (from RSS and UAH). All five series show consistent global warming trends ranging from 0.014 to 0.018 K yr−1. When the data are adjusted to remove the estimated impact of known factors on short-term temperature variations (El Niño/southern oscillation, volcanic aerosols and solar variability), the global warming signal becomes even more evident as noise is reduced. Lower-troposphere temperature responds more strongly to El Niño/southern oscillation and to volcanic forcing than surface temperature data. The adjusted data show warming at very similar rates to the unadjusted data, with smaller probable errors, and the warming rate is steady over the whole time interval. In all adjusted series, the two hottest years are 2009 and 2010.” Grant Foster and Stefan Rahmstorf 2011 Environ. Res. Lett. 6 044022 doi:10.1088/1748-9326/6/4/044022. [Full text]

Detecting abrupt climate changes on different time scales – Matyasovszky (2011) “Two concepts are introduced for detecting abrupt climate changes. In the first case, the sampling frequency of climate data is high as compared to the frequency of climate events examined. The method is based on a separation of trend and noise in the data and is applicable to any dataset that satisfies some mild smoothness and statistical dependence conditions for the trend and the noise, respectively. We say that an abrupt change occurs when the first derivative of the trend function has a discontinuity and the task is to identify such points. The technique is applied to Northern Hemisphere temperature data from 1850 to 2009, Northern Hemisphere temperature data from proxy data, a.d. 200–1995 and Holocene δ18O values going back to 11,700 years BP. Several abrupt changes are detected that are, among other things, beneficial for determining the Medieval Warm Period, Little Ice Age and Holocene Climate Optimum. In the second case, the sampling frequency is low relative to the frequency of climate events studied. A typical example includes Dansgaard–Oeschger events. The methodology used here is based on a refinement of autoregressive conditional heteroscedastic models. The key element of this approach is the volatility that characterises the time-varying variance, and abrupt changes are defined by high volatilities. The technique applied to δ18O values going back to 122,950 years BP is suitable for identifying DO events. These two approaches for the two cases are closely related despite the fact that at first glance, they seem quite different.” István Matyasovszky, Theoretical and Applied Climatology, Volume 105, Numbers 3-4 (2011), 445-454, DOI: 10.1007/s00704-011-0401-4.

Testing for Deterministic Trends in Global Sea Surface Temperature – Barbosa (2011) “Long-term variability in global sea surface temperature (SST) is often quantified by the slope from a linear regression fit. Attention is then focused on assessing the statistical significance of the derived slope parameter, but the adequacy of the linear model itself, and the inherent assumption of a deterministic linear trend, is seldom tested. Here, a parametric statistical test is applied to test the hypothesis of a linear deterministic trend in global sea surface temperature. The results show that a linear slope is not adequate for describing the long-term variability of sea surface temperature over most of the earth’s surface. This does not mean that sea surface temperature is not increasing, rather that the increase should not be characterized by the slope from a linear fit. Therefore, describing the long-term variability of sea surface temperature by implicitly assuming a deterministic linear trend can give misleading results, particularly in terms of uncertainty, since the actual increase could be considerably larger than the one predicted by a deterministic linear model.” Barbosa, Susana M., 2011: Testing for Deterministic Trends in Global Sea Surface Temperature. J. Climate, 24, 2516–2522. doi: http://dx.doi.org/10.1175/2010JCLI3877.1.

1963: The break point of the Northern Hemisphere temperature trend during the twentieth century – Ivanov & Evtimov (2010) “Besides gradually, climate can also change abruptly. The global surface temperature series is a major indicator of such changes. Using rigorous statistical tools, we show that during the twentieth century the time series of annual Northern Hemisphere surface temperature is well described by a trend-stationary process, but the trend line breaks in 1963. After six transitory years, in 1970, the temperature course locks up into a new regime with a triple linear warming rate. For the emergence and abruptness of the break we reveal the key roles of the Mount Agung eruption and the interannual to interdecadal changes of the major modes and patterns of climate variability. We offer an abrupt climate shift scenario based on the adaptivity of climatic regimes against instant external forcings.” Martin A. Ivanov, Stilian N. Evtimov, International Journal of Climatology, Volume 30, Issue 11, pages 1738–1746, September 2010, DOI: 10.1002/joc.2002.

Warming Break Trends and Fractional Integration in the Northern, Southern, and Global Temperature Anomaly Series – Gil-Alana (2008) “This paper deals with the estimation of time trends in temperature anomaly series. However, instead of imposing that the estimated residuals from the time trends are covariance stationary processes with spectral density that is positive and finite at the zero frequency [I(0)], the author allows them to be fractionally integrated. In this context, a new procedure for testing fractional integration with segmented trends is applied to the northern, southern, and global temperature anomaly series. The results show that the three series are fractionally integrated, and the warming effects are substantially higher after the break in all cases.” Gil-Alana, Luis A., 2008: Warming Break Trends and Fractional Integration in the Northern, Southern, and Global Temperature Anomaly Series. J. Atmos. Oceanic Technol., 25, 570–578. doi: http://dx.doi.org/10.1175/2007JTECHA1025.1. [Full text]

Semiparametric estimation and testing of the trend of temperature series – Gao & Hawthorne (2006) “The application of a partially linear model to global and hemispheric temperature series is proposed. Partially linear modelling allows the trend to take a very general form rather than imposing the restriction of linearity seen in existing studies. The removal of the linearity restriction is based on the fact that it is well accepted that a significant trend is present in global temperature series. The model will allow for the data to ‘speak for themselves’ with regard to the form of the trend. The results initially reveal that a linear trend does not approximate well the behaviour of global or hemispheric temperature series. This is further confirmed through a formal testing procedure. The results suggest that little faith should be instilled in long-term forecasts of temperatures in which the trend of global and hemispheric series is assumed to be linear. All the current evidence suggest that temperatures will continue to rise in an unknown and probably nonlinear fashion.” Jiti Gao, Kim Hawthorne, The Econometrics Journal, Volume 9, Issue 2, pages 332–355, July 2006, DOI: 10.1111/j.1368-423X.2006.00188.x.

Are winters getting warmer? – Vogelsang & Franses (2006) “We examine whether any trends in monthly temperatures are the same through-out the year for various lengthy series. The data concern the world, the northern and southern hemispheres, and about three centuries of data for the United Kingdom and the Netherlands. For the empirical exercise, we rely on new and accurate tests which have been recently developed. These tests do not have standard distributions, so that critical values have to be tabulated. The empirical findings include significant worldwide temperature increases, differences across months for the northern hemisphere, and warming winters for the UK and the Netherlands.” Timothy J. Vogelsang, Philip Hans Franses, Environmental Modelling & Software, Volume 20, Issue 11, November 2005, Pages 1449–1455, http://dx.doi.org/10.1016/j.envsoft.2004.09.016.

Tests of common deterministic trend slopes applied to quarterly global temperature data – Fomby & Vogelsang (2003) “We examine the global warming temperature data sets of Jones et al. (1999) and Vinnikov et al. (1994) in the context of the multivariate deterministic trend-testing framework of Franses and Vogelsang (2002). We find that, across all seasons, global warming seems to be present for the globe and for the northern and southern hemispheres. Globally and within hemispheres, it appears that seasons are not warming equally fast. In particular, winters appear to be warming faster than summers. Across hemispheres, it appears that the winters in the northern and southern hemispheres are warming equally fast whereas the remaining seasons appear to have unequal warming rates. The results obtained here seem to coincide with the findings of Kaufmann and Stern (2002) who use cointegration analysis and find that the hemispheres are warming at different rates.” Thomas B. Fomby, Timothy J. Vogelsang, (2003) “TESTS OF COMMON DETERMINISTIC TREND SLOPES APPLIED TO QUARTERLY GLOBAL TEMPERATURE DATA”, , Vol. Iss: 17, pp.29 – 43, doi: 10.1016/S0731-9053(03)17002-8.

The Application of Size-Robust Trend Statistics to Global-Warming Temperature Series – Fomby & Vogelsang (2002) “In this note, new evidence is provided confirming that global temperature series spanning back to the mid-1800s have statistically significant positive trends. Although there is a growing consensus that global temperatures are on the rise systematically, some recent studies have pointed out that strong serial correlation (or a unit root) in global temperature data could, in theory, generate spurious evidence of a significant positive trend. In other words, strong serially correlated data can mimic trending behavior over fixed periods of time. A serial-correlation–robust trend test recently was proposed that controls for the possibility of spurious evidence due to strong serial correlation. This new test is valid whether the errors are stationary or have a unit root (strong serial correlation). This test also has the attractive feature that it does not require estimates of serial correlation nuisance parameters. The test is applied to six annual global temperature series, and it provides strong evidence that global temperature series have positive trends that are statistically significant even when controlling for the possibility of strong serial correlation. The point estimates of the rate of increase in the trend suggest that temperatures have risen about 0.5°C (1.0°F) 100 yr−1. If the analysis is restricted to twentieth-century data, many of the point estimates are closer to 0.6°C.” Fomby, Thomas B., Timothy J. Vogelsang, 2002: The Application of Size-Robust Trend Statistics to Global-Warming Temperature Series. J. Climate, 15, 117–123, doi: http://dx.doi.org/10.1175/1520-0442(2002)0152.0.CO;2. [Full text]

Structural Time Series Models and Trend Detection in Global and Regional Temperature Series – Zheng & Basher (1999) “A unified statistical approach to identify suitable structural time series models for annual mean temperature is proposed. This includes a generalized model that can represent all the commonly used structural time series models for trend detection, the use of differenced series (successive year-to-year differences), and explicit methods for comparing the validity of no-trend nonstationary residuals models relative to trend models. Its application to Intergovernmental Panel on Climate Change global and latitude-belt temperature series reveals that a linear trend model (starting in 1890, with Southern Oscillation index signal removal and a red noise residuals process) is the optimal model for much of the globe, from the Northern Hemisphere Tropics to the Southern Hemisphere midlatitudes, but that a random stationary increment process (with no deterministic trend) is preferred for the northern part of the Northern Hemisphere. The result for the higher northern latitudes appears to be related to the greater climate variability there and does not exclude the possibility of a trend being present. The hemispheric and global series will contain a mixture of the two processes but are dominated by and best represented by the linear trend model. The latitudinal detectability of trends is oppositely matched to where GCMs indicate greatest anthropogenic trend, that is, it is best for the Tropics rather than for the high latitudes. The results reinforce the view that the global temperatures are affected by a long-term trend that is not of natural origin.” Zheng, Xiaogu, Reid E. Basher, 1999: Structural Time Series Models and Trend Detection in Global and Regional Temperature Series. J. Climate, 12, 2347–2358, doi: http://dx.doi.org/10.1175/1520-0442(1999)0122.0.CO;2. [Full text]

Trend Estimation and Regression Analysis in Climatological Time Series: An Application of Structural Time Series Models and the Kalman Filter – Visser & Molenaar (1995) “The detection of trends in climatological data has become central to the discussion on climate change due to the enhanced greenhouse effect. To prove detection, a method is needed (i) to make inferences on significant rises or declines in trends, (ii) to take into account natural variability in climate series, and (iii) to compare output from GCMs with the trends in observed climate data. To meet these requirements, flexible mathematical tools are needed. A structural time series model is proposed with which a stochastic trend, a deterministic trend, and regression coefficients can be estimated simultaneously. The stochastic trend component is described using the class of ARIMA models. The regression component is assumed to be linear. However, the regression coefficients corresponding with the explanatory variables may be time dependent to validate this assumption. The mathematical technique used to estimate this trend-regression model is the Kaiman filter. The main features of the filter are discussed. Examples of trend estimation are given using annual mean temperatures at a single station in the Netherlands (1706–1990) and annual mean temperatures at Northern Hemisphere land stations (1851–1990). The inclusion of explanatory variables is shown by regressing the latter temperature series on four variables: Southern Oscillation index (SOI), volcanic dust index (VDI), sunspot numbers (SSN), and a simulated temperature signal, induced by increasing greenhouse gases (GHG). In all analyses, the influence of SSN on global temperatures is found to be negligible. The correlations between temperatures and SOI and VDI appear to be negative. For SOI, this correlation is significant, but for VDI it is not, probably because of a lack of volcanic eruptions during the sample period. The relation between temperatures and GHG is positive, which is in agreement with the hypothesis of a warming climate because of increasing levels of greenhouse gases. The prediction performance of the model is rather poor, and possible explanations are discussed.” Visser, H., J. Molenaar, 1995: Trend Estimation and Regression Analysis in Climatological Time Series: An Application of Structural Time Series Models and the Kalman Filter. J. Climate, 8, 969–979, doi: http://dx.doi.org/10.1175/1520-0442(1995)0082.0.CO;2. [Full text]

Selecting a Model for Detecting the Presence of a Trend – Woodward & Gray (1995) “The authors consider the problem of determining whether the upward trending behavior in the global temperature anomaly series should be forecast to continue. To address this question, the generic problem of determining whether an observed trend in a time series realization is a random (i.e., short-term) trend or a deterministic (i.e., permanent) trend is considered. The importance of making this determination is that forecasts based on these two scenarios are dramatically different. Forecasts based on a series with random trends will not predict the observed trend to continue, while forecasts based on a model with deterministic trend will forecast the trend to continue into the future. In this paper, the authors consider an autoregressive integrated moving average (ARIMA) model and a “deterministic forcing function + autoregressive (AR) noise” model as possible random trend and deterministic trend models, respectively, for realizations displaying trending behavior. A bootstrap-based classification procedure for classifying an observed time series realization as ARIMA or “function + AR” using linear and quadratic forcing functions is introduced. A simulation study demonstrates that the procedure is useful in distinguishing between realizations from these two models. A unit-root test is also examined in an effort to distinguish between these two types of models. Using the techniques developed here, the temperature anomaly series are classified as ARIMA (i.e., having random trends).” Woodward, Wayne A., H. L. Gray, 1995: Selecting a Model for Detecting the Presence of a Trend. J. Climate, 8, 1929–1937, doi: http://dx.doi.org/10.1175/1520-0442(1995)0082.0.CO;2. [Full text]

Global Warming and the Problem of Testing for Trend in Time Series Data – Woodward & Gray (1993)“In recent years a number of statistical tests have been proposed for testing the hypothesis that global warming is occurring. The standard approach is to examine one or two of the more prominent global temperature datasets by letting Yt = a + bt + Et, where Yt represents the temperature at time t and Et represents error from the trend line, and to test the hypothesis that b = 0. Several authors have applied these tests for trend to determine whether or not a significant long-term or deterministic trend exists, and have generally concluded that there is a significant deterministic trend in the data. However, we show that certain autoregressive-moving average (ARMA) models may also be very reasonable models for these data due to the random trends present in their realizations. In this paper, we provide simulation evidence to show that the tests for trend detect a deterministic trend in a relatively high percentage of realizations from a wide range of ARMA models, including those obtained for the temperature series, for which it is improper to forecast a trend to continue over more than a very short time period. Thus, we demonstrate that trend tests based on models such as Yt = a + bt + Et, where Yt for the purpose of prediction or inference concerning future behavior should be used with caution. Of course, the projections that the warming trend will extend into the future are largely based on such factors as the buildup of atmospheric greenhouse gases. We have shown here, however, that based solely on the available temperature anomaly series, it is difficult to conclude that the trend will continue over any extended length of time.” Woodward, Wayne A., H. L. Gray, 1993: Global Warming and the Problem of Testing for Trend in Time Series Data. J. Climate, 6, 953–962, doi: http://dx.doi.org/10.1175/1520-0442(1993)0062.0.CO;2. [Full text]

Climate spectra and detecting climate change – Bloomfield & Nychka (1992) “Part of the debate over possible climate changes centers on the possibility that the changes observed over the previous century are natural in origin. This raises the question of how large a change could be expected as a result of natural variability. If the climate measurement of interest is modelled as a stationary (or related) Gaussian time series, this question can be answered in terms of (a) the way in which change is estimated, and (b) the spectrum of the time series. These computations are illustrated for 128 years of global temperature data using some simple measures of change and for a variety of possible temperature spectra. The results highlight the time scales on which it is important to know the magnitude of natural variability. The uncertainties in estimates of trend are most sensitive to fluctuations in the temperature series with periods from approximately 50 to 500 years. For some of the temperature spectra, it was found that the standard error of the least squares trend estimate was 3 times the standard error derived under the naïve assumption that the temperature series was uncorrelated. The observed trend differs from zero by more than 3 times the largest of the calculated standard errors, however, and is therefore highly significant.” Peter Bloomfield and Douglas Nychka, Climatic Change, Volume 21, Number 3 (1992), 275-287, DOI: 10.1007/BF00139727.

Trends in global temperature – Bloomfield (1992) “Statistical models consisting of a trend plus serially correlated noise may be fitted to observed climate data such as global surface temperature, the trend and noise representing systematic change and other variations, respectively. When such a model is fitted, the estimated character of the noise determines the precision of the estimated trend, and hence the precision of the estimate of the magnitude of the systematic change in the variable considered. The results of fitting such models to global temperature imply that there is uncertainty in the amount of temperature change over the past century of up to ± 0.2 °C, but that the change of around one half of a degree Celsius is significantly different from zero. The statistical models for climate variability also imply that the observed temperature data provide only imprecise information about the climate sensitivity. This is defined here as the equilibrium response of global temperature to a doubling of the atmospheric concentration of carbon dioxide. The temperature changes observed to date are compatible with a wide range of climate sensitivities, from 0.7 °C to 2.2 °C. When data uncertainties are taken into account, the interval widens even further.” Peter Bloomfield, Climatic Change, Volume 21, Number 1 (1992), 1-16, DOI: 10.1007/BF00143250.

Inference about trends in global temperature data – Galbraith & Green (1992) “Interpretation of the effects of increasing atmospheric carbon dioxide on temperature is made more difficult by the fact that it is unclear whether sufficient global warming has taken place to allow a statistically significant finding of any upward trend in the temperature series. We add to the few existing statistical results by reporting tests for both deterministic and stochastic non-stationarity (trends) in time series of global average temperature. We conclude that the statistical evidence is sufficient to reject the hypothesis of a stochastic trend; however, there is evidence of a trend which could be approximated by a deterministic linear model.” John W. Galbraith and Christopher Green, Climatic Change, Volume 22, Number 3 (1992), 209-221, DOI: 10.1007/BF00143028.

Interdecadal oscillations and the warming trend in global temperature time series – Ghil & Vautard (1991) “THE ability to distinguish a warming trend from natural variability is critical for an understanding of the climatic response to increasing greenhouse-gas concentrations. Here we use singular spectrum analysis1 to analyse the time series of global surface air tem-peratures for the past 135 years, allowing a secular warming trend and a small number of oscillatory modes to be separated from the noise. The trend is flat until 1910, with an increase of 0.4 °C since then. The oscillations exhibit interdecadal periods of 21 and 16 years, and interannual periods of 6 and 5 years. The interannual oscillations are probably related to global aspects of the El Niño-Southern Oscillation (ENSO) phenomenon. The interdecadal oscillations could be associated with changes in the extratropical ocean circulation. The oscillatory components have combined (peak-to-peak) amplitudes of >0.2 °C, and therefore limit our ability to predict whether the inferred secular warming trend of 0.005 °Cyr−1 will continue. This could postpone incontrovertible detection of the greenhouse warming signal for one or two decades.” M. Ghil & R. Vautard, Nature 350, 324 – 327 (28 March 1991); doi:10.1038/350324a0. [Full text]

Global Warming as a Manifestation of a Random Walk – Gordon (1991) “Global and hemispheric series of surface temperature anomalies are examined in an attempt to isolate any specific features of the structure of the series that might contribute to the global warming of about 0.5°C which has been observed over the past 100 years. It is found that there are no significant differences between the means of the positive and negative values of the changes in temperature from one year to the next; neither do the relative frequencies of the positive and negative values differ from the frequencies that would be expected by chance with a probability near 0.5. If the interannual changes are regarded as changes of unit magnitude and plotted in a Cartesian frame of reference with time measured along the x axis and yearly temperature differences along the y axis, the resulting path closely resembles the kind of random walk that occurs during a coin-tossing game. We hypothesize that the global and hemispheric temperature series are the result of a Markov process. The climate system is subjected to various forms of random impulses. It is argued that the system fails to return to its former state after reacting to an impulse but tends to adjust to a new state of equilibrium as prescribed by the shock. This happens because a net positive feedback accompanies each shock and slightly alters the environmental state.” Gordon, A. H., 1991: Global Warming as a Manifestation of a Random Walk. J. Climate, 4, 589–597, doi: http://dx.doi.org/10.1175/1520-0442(1991)0042.0.CO;2. [Full text]

Detecting CO2-induced climatic change – Wigley & Jones (1981) “Although it is widely believed that increasing atmospheric CO2 levels will cause noticeable global warming, the effects are not yet detectable, possibly because of the ‘noise’ of natural climatic variability. An examination of the spatial and seasonal distribution of signal-to-noise ratio shows that the highest values occur in summer and annual mean surface temperatures averaged over the Northern Hemisphere or over mid-latitudes. The spatial and seasonal characteristics of the early twentieth century warming were similar to those expected from increasing CO2 based on an equilibrium response model. This similarity may hinder the early detection of CO2 effects on climate.” T. M. L. Wigley & P. D. Jones, Nature 292, 205 – 208 (16 July 1981); doi:10.1038/292205a0.

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Papers on carbon dioxide and water vapor overlap

Posted by Ari Jokimäki on October 19, 2011

This is a list of papers on the overlap of the the absorption bands of carbon dioxide and water vapor. See also my article on the history of this issue including additional references. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

An improved treatment of overlapping absorption bands based on the correlated k distribution model for thermal infrared radiative transfer calculations – Xu et al. (2009) “This paper discusses several schemes for handling gaseous overlapping bands in the context of the correlated k distribution model (CKD). Commonly used methods are generally based on certain spectral correlation assumptions; thus they are either less accurate or less efficient and rarely apply to all overlapping bands. We propose a new treatment, which we developed from the traditional absorber amount weighted scheme and improved for application to various bands. This approach is quite efficient for treating the gaseous mixture as if it were a “single gas.” Numerical experiments demonstrate that the new scheme achieves high accuracy with a fast operating speed. To validate the new scheme, we conducted spectrally integrated calculations and sensitivity experiments in the thermal infrared region. Compared to line-by-line integration results, errors in cooling rates were less than 0.2 K/day below 70 Km and rose to 1 K/day from above 70 Km up to 100 Km; flux differences did not exceed 0.8 W/m2 at any altitude. Changes in CO2 and H2O concentrations slightly influenced the accuracy of the results.” Guangyu Shi, Na Xu, Biao Wang, Tie Dai, Jianqi Zhao, Journal of Quantitative Spectroscopy and Radiative Transfer, Volume 110, Issue 8, May 2009, Pages 435-451, doi:10.1016/j.jqsrt.2009.01.008.

A Mechanism of Tropical Precipitation Change due to CO2 Increase – Sugi & Yoshimura (2004) “A recent GCM study indicates that a weakening of tropical circulation associated with a slight increase in tropical precipitation may occur when atmospheric CO2 is increased. To further understand the mechanism of atmospheric temperature and precipitation changes associated with the greenhouse gas increase, a numerical experiment was conducted using an atmospheric general circulation model to investigate the separate effects of CO2 increase and sea surface temperature (SST) increase. It has been shown that the effect of CO2 increase is a reduction of radiative cooling in the lower troposphere, leading to a reduction of tropical precipitation. When atmospheric CO2 concentration is doubled (quadrupled) without changing the SST, the tropical precipitation is reduced by about 3% (6%) in the model. The reduction of radiative cooling is a result of the overlap effect of the CO2 15-μm and water vapor absorption bands. On the other hand, the effect of SST increase is the increase in atmospheric temperature and water vapor, leading to increases in radiative cooling and tropical precipitation. When SST is uniformly raised 2°C without changing the atmospheric CO2 concentration, the tropical precipitation is increased by about 6%.” Sugi, Masato, Jun Yoshimura, 2004, J. Climate, 17, 238–243, doi: 10.1175/1520-0442(2004)0172.0.CO;2. [Full text]

An optimal approach to overlapping bands with correlated k distribution method and its application to radiative calculations – Zhang et al. (2003) “It is found that the possibly achieved higher accuracy cannot be obtained for all overlapping bands if only one scheme is used to treat them in atmospheric absorption calculations. The commonly used multiplication transmittance scheme is not acceptable when correlation existing in the practical absorption spectra becomes strong. Therefore an optimized scheme to obtain k distribution parameters for overlapping bands is developed in this paper based on the completely uncorrelated, perfectly correlated, and partly correlated schemes. Two partial correlation formulae are given in the paper. Calculations of radiative flux and atmospheric heating (or cooling) rate are validated in detail using a line-by-line model described in the paper for six model atmospheres. The optimized scheme developed here has an accuracy in longwave clear skies of 0.07 K d−1 in the entire troposphere and 0.35 K d−1 above the tropopause; the accuracy of upward, downward, and net fluxes is 0.76 W m−2 at all altitudes. In shortwave region, the absolute errors of the heating rate are less than 0.05 K d−1 in the troposphere and less than 0.25 K d−1 above the tropopause; net flux errors are less than 0.9 W m−2 at all altitudes. For an ensemble of 42 diverse atmospheres, the new scheme guarantees an average maximum error of longwave heating rate of 0.068 K d−1 in troposphere, 0.22 K d−1 above tropopause, and an accuracy of 1.1 W m−2 of radiative net flux for all the levels. For a case of doubled CO2 concentration, radiative forcing calculations have an accuracy of 0.04 W m−2.” Zhang, H., T. Nakajima, G. Shi, T. Suzuki, and R. Imasu (2003), J. Geophys. Res., 108(D20), 4641, doi:10.1029/2002JD003358.

Feedback effects of atmospheric CO2-induced warming – Adem & Garduño (1998) “Using a thermodynamic climate model, temperature and precipitation changes due to a doubling of atmospheric CO2 content, including the corresponding feedback temperature increases of water vapor, snow-ice, and cloudiness, are evaluated. The feedback factors of the thermodynamic model are similar to those of Hansen et al. (1984) and Schlesinger (1986). The feedback factor of all three mechanisms combined is 4.0. The results depend mainly on the content of water vapor in the CO2 band (12-19μ). The temperature increase due to a doubling of CO2 is 1.2° C when there is water vapor in the band, and 3.5° C when there is no water vapor. Therefore, a possible cause of the strong differences in the solutions obtained by different models is the discrepancy in the amount and distribution of water vapor in the atmosphere, and in the treatment of its effect in the CO2 band.” Julián Adem, René Garduño, Geofísica Internacional, 1998, Volume 37, Issue 2, pages 55-70. [Full text]

Earth’s Annual Global Mean Energy Budget – Kiehl & Trenberth (1997) A quote from the article: “It is also important to note that different gases can absorb radiation at the same wavelengths; this is called the overlap effect. … Of this 125 W m-2 clear sky greenhouse effect, we can ask, what is the relative contribution of each atmospheric absorber? A detailed answer to this question is complicated by the overlap among individual gaseous absorption features. We calculate the longwave radiative forcing of a given gas by sequentially removing atmospheric absorbers from the radiation model. We perform these calculations for clear and cloudy sky conditions to illustrate the role of clouds to a given absorber for the total radiative forcing. Table 3 lists the individual contribution of each absorber to the total clear sky radiative forcing.” Kiehl, J. T., Kevin E. Trenberth, 1997: Earth’s Annual Global Mean Energy Budget. Bull. Amer. Meteor. Soc., 78, 197–208, doi: 10.1175/1520-0477(1997)0782.0.CO;2. [Full text]

Uncertainties in Carbon Dioxide Radiative Forcing in Atmospheric General Circulation Models – Cess et al. (1993) A quote from the article: “Fig. 3. (A) Scatter plot of LW clear (clear sky) radiative forcing, as generated by the GCMs, with and without overlap of the C02 absorption bands by water vapor absorption.” R. D. Cess, M.-H. Zhang, G. L. Potter, H. W. Barker, R. A. Colman, D. A. Dazlich, A. D. Del Genio, M. Esch, J. R. Fraser, V. Galin, W. L. Gates, J. J. Hack, W. J. Ingram, J. T. Kiehl, A. A. Lacis, H. Le Treut, Z.-X. Li, X.-Z. Liang, J.-F. Mahfouf, B. J. McAvaney, V. P. Meleshko, J.-J. Morcrette, D. A. Randall, E. Roeckner, J.-F. Royer, A. P. Sokolov, P. V. Sporyshev, K. E. Taylor, W.-C. Wang and R. T. Wetherald, Science 19 November 1993: Vol. 262 no. 5137 pp. 1252-1255, DOI: 10.1126/science.262.5137.1252.

The Intercomparison of Radiation Codes Used in Climate Models: Long Wave Results – Ellingson et al. (1991) A quote from the article: “One of the more overlooked problems in atmospheric absorption is the simultaneous absorption by two or more constituents across the same spectral interval (i.e., overlapping absorption). This is a particularly important problem for H2O and CO2 absorption in the 10- and 15-µm regions; … The issue of overlapping absorption is important to climate assessment particularly when one or both of the overlapping bands have strong absorption lines as is the case between the 15-µm bands of CO2 and the rotational band of H20 in the 12-18 µ m spectral region. Kiehl and Ramanathan [1982] studied the effect of this overlap on the radiative heating resulting from increased CO2, and they showed that there is a substantial reduction in the magnitude of increase in downward flux to the surface when the overlap is included. The greatest difference occurs at tropical H20 latitudes where there is a larger amount of H20. When the overlap with the continuum in the 12-18 µ m region is added, there is very little increase in downward flux to the surface in the tropics from doubled CO2 because the lower tropical atmosphere is already essentially opaque. When band overlap is included, there is a substantial increase in the tropospheric heating rates, which tends to compensate for the reduction in downward flux at the surface. Thus the degree of overlap in this spectral region affects the way the net warming is partitioned between the surface and the troposphere, but has only a weak effect on the total heating of the troposphere.” Ellingson, R. G., J. Ellis, and S. Fels (1991), J. Geophys. Res., 96(D5), 8929–8953, doi:10.1029/90JD01450. [Full text]

Overlapping effect of atmospheric H2O, CO2 and O3 on the CO2 radiative effect – Wang & Ryan (1983)“The effect of overlapping of atmospheric H2O, CO2 and O3 absorption bands on the radiation budget perturbation caused by CO2 doubling is investigated. Since the effect depends on the amount of gases in the atmosphere as well as on the strength of the absorption bands, we examine the effect associated with the variation of gas abundance using a narrow band representation for the absorption bands. This band representation allows for the absorption band structure and thus accounts for the correlation of the spectral feature of the absorbing gases. It is found that the presence of H2O and O3 has a relatively small influence on the CO2-induced perturbation of both solar and thermal radiation in the stratosphere. However, in troposphere and surface, the overlapping effect appears to be quite significant and changes the vertical distribution of the CO2-induced radiation energy perturbation. For example, in the infrared, the effect is to reduce the effectiveness for CO2 to emit and in the mean time increases the tropospheric absorption of downward thermal flux from the stratosphere due to CO2 increase; the net effect of the overlapping of gases is to increase the tropospheric warming and decrease the surface warming caused by CO2 increase. It is also found that the overlapping effect exhibits strong seasonal and latitudinal variations due primarily to variations in atmospheric H2O.” Wei-Chyung Wang, P. Barry Ryan, Tellus B, Volume 35B, Issue 2, pages 81–91, April 1983.

Radiative Heating Due to Increased CO2: The Role of H2O Continuum Absorption in the 12–18 μm Region – Kiehl & Ramanathan (1982)“In the 12–18 μm spectral region, the CO2 bands are overlapped by the H2O pure rotational band and the H2O continuum band. The 12–18 μm H2O continuum absorption is neglected in most studies concerned with the climatic effects of increased CO2. In this study, we examine the role of H2O–CO2 overlap in detail. Specifically, the effect of the water vapor continuum in the 12–18 μm region on the radiative heating due to increased CO2 is investigated. It is found that although the longwave surface radiative heating due to increased CO2 is considerably reduced at low latitudes by H2O continuum absorption, where water vapor partial pressures are high, the radiative heating of the surface/troposphere system as a whole is minimally altered.” Kiehl, J. T., V. Ramanathan, 1982, J. Atmos. Sci., 39, 2923–2926, doi: 10.1175/1520-0469(1982)0392.0.CO;2. [Full text]

Spectral and total emissivity of water vapor and carbon dioxide – Leckner (1972) A quote from abstract: “Total emissivity charts, pressure and overlap corrections based on calculations with spectral data are presented.” B. Leckner, Combustion and Flame, Volume 19, Issue 1, August 1972, Pages 33-48, doi:10.1016/S0010-2180(72)80084-1.

Infrared Absorption by Overlapping Bands of Atmospheric Gases – Hoover et al. (1967) “The spectral transmission of carbon monoxide, nitrous oxide, and mixtures of the two has been studied in the 2200-cm-1 region, where overlapping absorption bands occur. With spectral slit widths sufficiently large to include several absorption lines, it was found that the observed spectral transmittance of a mixture is equal to the product of the transmittances of the components measured separately, provided that sufficient nitrogen is added to give the same total pressure for all samples. This result was also obtained for overlapping bands of nitrous oxide and methane in the 1300-cm-1 region. The present work confirms Burch’s earlier studies of overlapping bands of CO2 and water vapor. An investigation of the possible breakdown of the multiplicative property of transmission for narrow spectral slit widths was inconclusive.” D. E. Burch, J. N. Howard, and Dudley Williams, J. Opt. Soc. Am., Vol. 46, Issue 6, pp. 452-455 (1956), doi:10.1364/JOSA.46.000452.

Further Studies of Overlapping Absorption Bands – Tubbs et al. (1967) No abstract. D. E. Burch, J. N. Howard, and Dudley Williams, J. Opt. Soc. Am., Vol. 46, Issue 6, pp. 452-455 (1956), doi:10.1364/JOSA.46.000452.

Infrared Transmission of Synthetic Atmospheres. V. Absorption Laws for Overlapping Bands – Burch et al. (1956)“Although Lambert’s law Tv=ekvω presumably applies to the absorption of gases in the infrared, the experimentally observed transmission Tv′ cannot be expressed by a simple relation of this type. It is observed, however, that in regions where the atmospheric carbon dioxide and water vapor absorption bands overlap Tv′(CO2+H2O)= Tv′(CO2Tv′(H2O) provided the total pressure P is constant. It is found that the total absorption ƒ Avdv for a synthetic atmospheric sample containing water vapor, carbon dioxide, and nitrogen can be expressed as ƒ AvdV= ƒ Av(H2O)dv+εƒ Av(CO2)dv, where ƒ Av(H2O)dv and ƒ Av(CO2)dv are given by the empirical relations obtained in earlier studies in the present series and ε is a fraction, which can be expressed in terms of the total absorption by water vapor.” D. E. Burch, J. N. Howard, and Dudley Williams, J. Opt. Soc. Am., Vol. 46, Issue 6, pp. 452-455 (1956), doi:10.1364/JOSA.46.000452.

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Papers on climate impact on world food supply

Posted by Ari Jokimäki on October 16, 2011

This is a list of papers on climate impact on world food supply. Emphasis is on global analysis. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

I am proud to be taking part in Blog Action Day OCT 16 2011 www.blogactionday.org

Climate change, plant diseases and food security: an overview – Chakraborty & Newton (2011) “Global food production must increase by 50% to meet the projected demand of the world’s population by 2050. Meeting this difficult challenge will be made even harder if climate change melts portions of the Himalayan glaciers to affect 25% of world cereal production in Asia by influencing water availability. Pest and disease management has played its role in doubling food production in the last 40 years, but pathogens still claim 10–16% of the global harvest. We consider the effect of climate change on the many complex biological interactions affecting pests and pathogen impacts and how they might be manipulated to mitigate these effects. Integrated solutions and international co-ordination in their implementation are considered essential. Providing a background on key constraints to food security, this overview uses fusarium head blight as a case study to illustrate key influences of climate change on production and quality of wheat, outlines key links between plant diseases, climate change and food security, and highlights key disease management issues to be addressed in improving food security in a changing climate.” S. Chakraborty, A. C. Newton, Plant Pathology, Special Issue: Climate Change and Plant Diseases, Volume 60, Issue 1, pages 2–14, February 2011. [Full text]

Food Security: The Challenge of Feeding 9 Billion People – Godfray et al. (2010) “Continuing population and consumption growth will mean that the global demand for food will increase for at least another 40 years. Growing competition for land, water, and energy, in addition to the overexploitation of fisheries, will affect our ability to produce food, as will the urgent requirement to reduce the impact of the food system on the environment. The effects of climate change are a further threat. But the world can produce more food and can ensure that it is used more efficiently and equitably. A multifaceted and linked global strategy is needed to ensure sustainable and equitable food security, different components of which are explored here.” H. Charles J. Godfray, John R. Beddington, Ian R. Crute, Lawrence Haddad, David Lawrence, James F. Muir, Jules Pretty, Sherman Robinson, Sandy M. Thomas and Camilla Toulmin, Science 12 February 2010: Vol. 327 no. 5967 pp. 812-818, DOI: 10.1126/science.1185383. [Full text]

Food security and global environmental change: emerging challenges – Ericksen et al. (2009) “Most research linking global environmental change and food security focuses solely on agriculture: either the impact of climate change on agricultural production, or the impact of agriculture on the environment, e.g. on land use, greenhouse gas emissions, pollution and/or biodiversity. Important though food production is, many other factors also need to be considered to understand food security. A recent international conference on “Environmental Change and Food Security: Bridging Science, Policy and Development for Adaptation” included a range of papers that embraced the multiple dimensions of the food systems that underpin food security. The major conclusion from the conference was that technical fixes alone will not solve the food security challenge. Adapting to the additional threats to food security arising from major environmental changes requires an integrated food system approach, not just a focus on agricultural practices. Six key issues emerged for future research: (i) adapting food systems to global environmental change requires more than just technological solutions to increase agricultural yields; (ii) tradeoffs across multiple scales among food system outcomes are a pervasive feature of globalized food systems; (iii) within food systems, there are some key underexplored areas that are both sensitive to environmental change but also crucial to understanding its implications for food security and adaptation strategies; (iv) scenarios specifically designed to investigate the wider issues that underpin food security and the environmental consequences of different adaptation options are lacking; (v) price variability and volatility often threaten food security; and (vi) more attention needs to be paid to the governance of food systems.” Polly J. Ericksen, John S.I. Ingram, Diana M. Liverman, Environmental Science & Policy, Volume 12, Issue 4, June 2009, Pages 373-377, doi:10.1016/j.envsci.2009.04.007.

Historical Warnings of Future Food Insecurity with Unprecedented Seasonal Heat – Battisti & Naylor (2009) “Higher growing season temperatures can have dramatic impacts on agricultural productivity, farm incomes, and food security. We used observational data and output from 23 global climate models to show a high probability (>90%) that growing season temperatures in the tropics and subtropics by the end of the 21st century will exceed the most extreme seasonal temperatures recorded from 1900 to 2006. In temperate regions, the hottest seasons on record will represent the future norm in many locations. We used historical examples to illustrate the magnitude of damage to food systems caused by extreme seasonal heat and show that these short-run events could become long-term trends without sufficient investments in adaptation.” David. S. Battisti and Rosamond L. Naylor, Science 9 January 2009: Vol. 323 no. 5911 pp. 240-244, DOI: 10.1126/science.1164363.

Prioritizing Climate Change Adaptation Needs for Food Security in 2030 – Lobell et al. (2008) “Investments aimed at improving agricultural adaptation to climate change inevitably favor some crops and regions over others. An analysis of climate risks for crops in 12 food-insecure regions was conducted to identify adaptation priorities, based on statistical crop models and climate projections for 2030 from 20 general circulation models. Results indicate South Asia and Southern Africa as two regions that, without sufficient adaptation measures, will likely suffer negative impacts on several crops that are important to large food-insecure human populations. We also find that uncertainties vary widely by crop, and therefore priorities will depend on the risk attitudes of investment institutions.” David B. Lobell, Marshall B. Burke, Claudia Tebaldi, Michael D. Mastrandrea, Walter P. Falcon and Rosamond L. Naylor, Science 1 February 2008: Vol. 319 no. 5863 pp. 607-610, DOI: 10.1126/science.1152339. [Full text]

Food Security Under Climate Change – Brown & Funk (2008) “Food insecurity is likely to increase under climate change, unless early warning systems and development programs are used more effectively.” Molly E. Brown and Christopher C. Funk, Science 1 February 2008: Vol. 319 no. 5863 pp. 580-581, DOI: 10.1126/science.1154102.

Global food security under climate change – Schmidhuber & Tubiello (2007) “This article reviews the potential impacts of climate change on food security. It is found that of the four main elements of food security, i.e., availability, stability, utilization, and access, only the first is routinely addressed in simulation studies. To this end, published results indicate that the impacts of climate change are significant, however, with a wide projected range (between 5 million and 170 million additional people at risk of hunger by 2080) strongly depending on assumed socio-economic development. The likely impacts of climate change on the other important dimensions of food security are discussed qualitatively, indicating the potential for further negative impacts beyond those currently assessed with models. Finally, strengths and weaknesses of current assessment studies are discussed, suggesting improvements and proposing avenues for new analyses.” Josef Schmidhuber and Francesco N. Tubiello, PNAS December 11, 2007 vol. 104 no. 50 19703-19708, doi: 10.1073/pnas.0701976104. [Full text]

Climate change and food security – Gregory et al. (2005) “Dynamic interactions between and within the biogeophysical and human environments lead to the production, processing, distribution, preparation and consumption of food, resulting in food systems that underpin food security. Food systems encompass food availability (production, distribution and exchange), food access (affordability, allocation and preference) and food utilization (nutritional and societal values and safety), so that food security is, therefore, diminished when food systems are stressed. Such stresses may be induced by a range of factors in addition to climate change and/or other agents of environmental change (e.g. conflict, HIV/AIDS) and may be particularly severe when these factors act in combination. Urbanization and globalization are causing rapid changes to food systems. Climate change may affect food systems in several ways ranging from direct effects on crop production (e.g. changes in rainfall leading to drought or flooding, or warmer or cooler temperatures leading to changes in the length of growing season), to changes in markets, food prices and supply chain infrastructure. The relative importance of climate change for food security differs between regions. For example, in southern Africa, climate is among the most frequently cited drivers of food insecurity because it acts both as an underlying, ongoing issue and as a short-lived shock. The low ability to cope with shocks and to mitigate long-term stresses means that coping strategies that might be available in other regions are unavailable or inappropriate. In other regions, though, such as parts of the Indo-Gangetic Plain of India, other drivers, such as labour issues and the availability and quality of ground water for irrigation, rank higher than the direct effects of climate change as factors influencing food security. Because of the multiple socio-economic and bio-physical factors affecting food systems and hence food security, the capacity to adapt food systems to reduce their vulnerability to climate change is not uniform. Improved systems of food production, food distribution and economic access may all contribute to food systems adapted to cope with climate change, but in adopting such changes it will be important to ensure that they contribute to sustainability. Agriculture is a major contributor of the greenhouse gases methane (CH4) and nitrous oxide (N2O), so that regionally derived policies promoting adapted food systems need to mitigate further climate change.” P.J Gregory, J.S.I Ingram and M Brklacich, Phil. Trans. R. Soc. B 29 November 2005 vol. 360 no. 1463 2139-2148, doi: 10.1098/rstb.2005.1745. [Full text]

Climate change, global food supply and risk of hunger – Parry et al. (2005) “This paper reports the results of a series of research projects which have aimed to evaluate the implications of climate change for food production and risk of hunger. There are three sets of results: (a) for IS92a (previously described as a ‘business-as-usual’ climate scenario); (b) for stabilization scenarios at 550 and 750 ppm and (c) for Special Report on Emissions Scenarios (SRES). The main conclusions are: (i) the region of greatest risk is Africa; (ii) stabilization at 750 ppm avoids some but not most of the risk, while stabilization at 550 ppm avoids most of the risk and (iii) the impact of climate change on risk of hunger is influenced greatly by pathways of development. For example, a SRES B2 development pathway is characterized by much lower levels of risk than A2; and this is largely explained by differing levels of income and technology not by differing amounts of climate forcing.” Martin Parry, Cynthia Rosenzweig and Matthew Livermore, Phil. Trans. R. Soc. B 29 November 2005 vol. 360 no. 1463 2125-2138, doi: 10.1098/rstb.2005.1751. [Full text]

In addition to the 2 papers above, see also other papers in Philosophical Transactions B Discussion Meeting Issue ‘Food crops in a changing climate’

Effects of climate change on global food production under SRES emissions and socio-economic scenarios – Parry et al. (2004) “This paper analyses the global consequences to crop yields, production, and risk of hunger of linked socio-economic and climate scenarios. Potential impacts of climate change are estimated for climate change scenarios developed from the HadCM3 global climate model under the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (SRES) A1FI, A2, B1, and B2. Projected changes in yield are calculated using transfer functions derived from crop model simulations with observed climate data and projected climate change scenarios. The basic linked system (BLS) is used to evaluate consequent changes in global cereal production, cereal prices and the number of people at risk from hunger. The crop yield results elucidate the complex regional patterns of projected climate variables, CO2 effects, and agricultural systems that contribute to aggregations of global crop production. The A1FI scenario, as expected with its large increase in global temperatures, exhibits the greatest decreases both regionally and globally in yields, especially by the 2080s. The contrast between the yield change in developed and developing countries is largest under the A2a–c scenarios. Under the B1 and B2 scenarios, developed and developing countries exhibit less contrast in crop yield changes, with the B2 future crop yield changes being slightly more favourable than those of the B1 scenario. When crop yield results are introduced to the BLS world food trade system model, the combined model and scenario experiments demonstrate that the world, for the most part, appears to be able to continue to feed itself under the SRES scenarios during the rest of this century. However, this outcome is achieved through production in the developed countries (which mostly benefit from climate change) compensating for declines projected, for the most part, for developing nations. While global production appears stable, regional differences in crop production are likely to grow stronger through time, leading to a significant polarisation of effects, with substantial increases in prices and risk of hunger amongst the poorer nations, especially under scenarios of greater inequality (A1FI and A2). The use of the SRES scenarios highlights several non-linearities in the world food supply system, both in the biophysical sense, where the levels of atmospheric CO2 tested reach new levels, and the socio-economic sense, where changes in population dynamics and economic and political structures complicate the translation of biophysical climate change impacts into social indices, such as the number of people at risk of hunger.” M.L Parry, C Rosenzweig, A Iglesias, M Livermore, G Fischer, Global Environmental Change, Volume 14, Issue 1, April 2004, Pages 53-67, doi:10.1016/j.gloenvcha.2003.10.008. [Full text]

Climate change and world food security: a new assessment – Parry et al. (1999) “Building on previous work quantitative estimates of climate change impacts on global food production have been made for the UK Hadley Centre’s HadCM2 greenhouse gas only ensemble experiment and the more recent HadCM3 experiment (Hulme et al., 1999). The consequences for world food prices and the number of people at risk of hunger as defined by the Food and Agriculture Organisation (FAO, 1988) have also been assessed. Climate change is expected to increase yields at high and mid-latitudes, and lead to decreases at lower latitudes. This pattern becomes more pronounced as time progresses. The food system may be expected to accommodate such regional variations at the global level, with production, prices and the risk of hunger being relatively unaffected by the additional stress of climate change. By the 2080s the additional number of people at risk of hunger due to climate change is about 80 million people (±10 million depending on which of the four HadCM2 ensemble members is selected). However, some regions (particularly the arid and sub-humid tropics) will be adversely affected. A particular example is Africa, which is expected to experience marked reductions in yield, decreases in production, and increases in the risk of hunger as a result of climate change. The continent can expect to have between 55 and 65 million extra people at risk of hunger by the 2080s under the HadCM2 climate scenario. Under the HadCM3 climate scenario the effect is even more severe, producing an estimated additional 70+ million people at risk of hunger in Africa.” Martin Parry, Cynthia Rosenzweig, Ana Iglesias, Günther Fischer, Matthew Livermore, Global Environmental Change, Volume 9, Supplement 1, October 1999, Pages S51-S67, doi:10.1016/S0959-3780(99)00018-7.

Potential impact of climate change on world food supply – Rosenzweig & Parry (1994) “A global assessment of the potential impact of climate change on world food supply suggests that doubling of the atmospheric carbon dioxide concentration will lead to only a small decrease in global crop production. But developing countries are likely to bear the brunt of the problem, and simulations of the effect of adaptive measures by farmers imply that these will do little to reduce the disparity between developed and developing countries.” Cynthia Rosenzweig & Martin L. Parry, Nature 367, 133 – 138 (13 January 1994); doi:10.1038/367133a0. [Full text]

Climate change and world food supply, demand and trade: Who benefits, who loses? – Fischer et al. (1994) “This paper summarizes the findings of a major interdisciplinary research effort by scientists in 25 countries. The study examined the potential biophysical responses of major food crops to changing atmospheric composition and climate, and projected potential socioeconomic consequences. In a first step crop models were used to estimate how changing climatic conditions might alter yields of major crops at a number of sites representing both major production areas and vulnerable regions at low, mid and high latitudes. Then a dynamic recursive national-level model of the world food system was used to assess socio-economic impacts for the period 1990 up to year 2060.” G. Fischer, K. Frohberg, M.L. Parry, C. Rosenzweig, Global Environmental Change, Volume 4, Issue 1, March 1994, Pages 7-23, doi:10.1016/0959-3780(94)90018-3.

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Papers on atmospheric CO2 from proxies

Posted by Ari Jokimäki on July 6, 2011

This is a list of papers on atmospheric carbon dioxide contents determined from proxies. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (June 3, 2012): Hönisch et al. (2009) added. Thank to Nick for pointing it out.
UPDATE (April 18, 2012): Breecker et al. (2010) added. Thanks to Barry for pointing it out.

Atmospheric paleo-CO2 estimates based on Taxodium distichum (Cupressaceae) fossils from the Miocene and Pliocene of Eastern North America – Stults et al. (2011) “Neogene atmospheric paleo-CO2 estimates based on fossils of the extant cupressaceous conifer species Taxodium distichum from the Brandywine Formation of Maryland and the Citronelle Formation of southern Alabama are presented. These are important as the first such estimates from eastern North American paleofloras, and provide new evidence from a time for which the role of CO2 in climate change is controversial. Comparisons of the stomatal density (SD) of the fossil leaf cuticles to a calibration curve constructed from modern leaves of the same species collected over the last century of anthropogenic CO2 increase produces Miocene and Pliocene atmospheric paleo-CO2 mean estimates of 360 and 351 ppmv, respectively. Although the temporal resolution of the fossil sites is low, these results are in agreement with multiple independent proxies that indicate near modern CO2 levels during this interval, and demonstrate the utility of T. distichum leaves as instruments for stomatal frequency analysis.” Debra Z. Stults, Friederike Wagner-Cremer and Brian J. Axsmith, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.06.017.

Transient Middle Eocene Atmospheric CO2 and Temperature Variations – Bijl et al. (2010) “The long-term warmth of the Eocene (~56 to 34 million years ago) is commonly associated with elevated partial pressure of atmospheric carbon dioxide (pCO2). However, a direct relationship between the two has not been established for short-term climate perturbations. We reconstructed changes in both pCO2 and temperature over an episode of transient global warming called the Middle Eocene Climatic Optimum (MECO; ~40 million years ago). Organic molecular paleothermometry indicates a warming of southwest Pacific sea surface temperatures (SSTs) by 3° to 6°C. Reconstructions of pCO2 indicate a concomitant increase by a factor of 2 to 3. The marked consistency between SST and pCO2 trends during the MECO suggests that elevated pCO2 played a major role in global warming during the MECO.” Peter K. Bijl, Alexander J. P. Houben, Stefan Schouten, Steven M. Bohaty, Appy Sluijs, Gert-Jan Reichart, Jaap S. Sinninghe Damsté and Henk Brinkhuis, Science 5 November 2010: Vol. 330 no. 6005 pp. 819-821, DOI: 10.1126/science.1193654. [Full text]

Alkenone and boron-based Pliocene pCO2 records – Seki et al. (2010) “The Pliocene period is the most recent time when the Earth was globally significantly ( 3 °C) warmer than today. However, the existing pCO2 data for the Pliocene are sparse and there is little agreement between the various techniques used to reconstruct palaeo-pCO2. This disagreement, coupled with the general low temporal resolution of the published records, does not allow a robust assessment of the role of declining pCO2 in the intensification of the Northern Hemisphere Glaciation (INHG) and a direct comparison to other proxy records are lacking. For the first time, we use a combination of foraminiferal (δ11B) and organic biomarker (alkenone-derived carbon isotopes) proxies to determine the concentration of atmospheric CO2 over the past 5 Ma. Both proxy records show that during the warm Pliocene pCO2 was between 330 and 400 ppm, i.e. similar to today. The decrease to values similar to pre-industrial times (275–285 ppm) occurred between 3.2 Ma and 2.8 Ma — coincident with the INHG and affirming the link between global climate, the cryosphere and pCO2.” Osamu Seki, Gavin L. Foster, Daniela N. Schmidt, Andreas Mackensen, Kimitaka Kawamura and Richard D. Pancost, Earth and Planetary Science Letters, Volume 292, Issues 1-2, 15 March 2010, Pages 201-211, doi:10.1016/j.epsl.2010.01.037. [Full text]

A benthic δ13C-based proxy for atmospheric pCO2 over the last 1.5 Myr – Lisiecki (2010) “A high-resolution marine proxy for atmospheric pCO2 is needed to clarify the phase lag between pCO2 and marine climate proxies and to provide a record of orbital-scale pCO2 variations before the oldest ice core measurement at 800 ka. Benthic δ13C data should record deep ocean carbon storage and, thus, atmospheric pCO2. This study finds that a modified δ13C gradient between the deep Pacific and intermediate North Atlantic (Δδ13CP-NA/2) correlates well with pCO2. Δδ13CP-NA/2 reproduces characteristic differences between pCO2 and ice volume during Late Pleistocene glaciations and indicates that pCO2 usually leads terminations by 0.2–3.7 kyr but lags by 3–10 kyr during two “failed” terminations at 535 and 745 ka. Δδ13CP-NA/2 gradually transitions from 41- to 100-kyr cyclicity from 1.3–0.7 Ma but has no secular trend in mean or amplitude since 1.5 Ma. The minimum pCO2 of the last 1.5 Myr is estimated to be 155 ppm at ∼920 ka.” Lisiecki, L. E. (2010), Geophys. Res. Lett., 37, L21708, doi:10.1029/2010GL045109. [Full text]

Atmospheric CO2 concentrations during ancient greenhouse climates were similar to those predicted for A.D. 2100 – Breecker et al. (2010) “Quantifying atmospheric CO2 concentrations ([CO2]atm) during Earth’s ancient greenhouse episodes is essential for accurately predicting the response of future climate to elevated CO2 levels. Empirical estimates of [CO2]atm during Paleozoic and Mesozoic greenhouse climates are based primarily on the carbon isotope composition of calcium carbonate in fossil soils. We report that greenhouse [CO2]atm have been significantly overestimated because previously assumed soil CO2 concentrations during carbonate formation are too high. More accurate [CO2]atm, resulting from better constraints on soil CO2, indicate that large (1,000s of ppmV) fluctuations in [CO2]atm did not characterize ancient climates and that past greenhouse climates were accompanied by concentrations similar to those projected for A.D. 2100..” D. O. Breecker, Z. D. Sharp, and L. D. McFadden, PNAS January 12, 2010 vol. 107 no. 2 576-580, doi: 10.1073/pnas.0902323106. [Full text]

Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years – Tripati et al. (2009) “The carbon dioxide (CO2) content of the atmosphere has varied cyclically between ~180 and ~280 parts per million by volume over the past 800,000 years, closely coupled with temperature and sea level. For earlier periods in Earth’s history, the partial pressure of CO2 (pCO2) is much less certain, and the relation between pCO2 and climate remains poorly constrained. We use boron/calcium ratios in foraminifera to estimate pCO2 during major climate transitions of the past 20 million years. During the Middle Miocene, when temperatures were ~3° to 6°C warmer and sea level was 25 to 40 meters higher than at present, pCO2 appears to have been similar to modern levels. Decreases in pCO2 were apparently synchronous with major episodes of glacial expansion during the Middle Miocene (~14 to 10 million years ago) and Late Pliocene (~3.3 to 2.4 million years ago).” Aradhna K. Tripati, Christopher D. Roberts and Robert A. Eagle, Science 4 December 2009: Vol. 326 no. 5958 pp. 1394-1397, DOI: 10.1126/science.1178296. [Full text]

Atmospheric Carbon Dioxide Concentration Across the Mid-Pleistocene Transition – Hönisch et al. (2009) “The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of CO2 (Pco2), based on boron isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of CO2 (pco2) was relatively stable before the mid-Pleistocene climate transition. Glacial Pco2 was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial Pco2 was similar to that of late Pleistocene interglacial cycles (<450,000 years ago). These estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate, but the lack of a gradual decrease in interglacial Pco2 does not support the suggestion that a long-term drawdown of atmospheric CO2 was the main cause of the climate transition.” Bärbel Hönisch, N. Gary Hemming, David Archer, Mark Siddall and Jerry F. McManus, Science 19 June 2009: Vol. 324 no. 5934 pp. 1551-1554, DOI: 10.1126/science.1171477.

CO2-forced climate thresholds during the Phanerozoic – Royer (2006) “The correspondence between atmospheric CO2 concentrations and globally averaged surface temperatures in the recent past suggests that this coupling may be of great antiquity. Here, I compare 490 published proxy records of CO2 spanning the Ordovician to Neogene with records of global cool events to evaluate the strength of CO2-temperature coupling over the Phanerozoic (last 542 my). For periods with sufficient CO2 coverage, all cool events are associated with CO2 levels below 1000 ppm. A CO2 threshold of below 500 ppm is suggested for the initiation of widespread, continental glaciations, although this threshold was likely higher during the Paleozoic due to a lower solar luminosity at that time. Also, based on data from the Jurassic and Cretaceous, a CO2 threshold of below 1000 ppm is proposed for the initiation of cool non-glacial conditions. A pervasive, tight correlation between CO2 and temperature is found both at coarse (10 my timescales) and fine resolutions up to the temporal limits of the data set (million-year timescales), indicating that CO2, operating in combination with many other factors such as solar luminosity and paleogeography, has imparted strong control over global temperatures for much of the Phanerozoic.” Dana L. Royer, Geochimica et Cosmochimica Acta, Volume 70, Issue 23, 1 December 2006, Pages 5665-5675, doi:10.1016/j.gca.2005.11.031. [Full text]

Changes in carbon dioxide during an oceanic anoxic event linked to intrusion into Gondwana coals – McElwain et al. (2005) “The marine sedimentary record exhibits evidence for episodes of enhanced organic carbon burial known as ‘oceanic anoxic events’ (OAEs). They are characterized by carbon-isotope excursions in marine and terrestrial reservoirs and mass extinction of marine faunas. Causal mechanisms for the enhancement of organic carbon burial during OAEs are still debated, but it is thought that such events should draw down significant quantities of atmospheric carbon dioxide. In the case of the Toarcian OAE (183 million years ago), a short-lived negative carbon-isotope excursion in oceanic and terrestrial reservoirs has been interpreted to indicate raised atmospheric carbon dioxide caused by oxidation of methane catastrophically released from either marine gas hydrates or magma-intruded organic-rich rocks. Here we test these two leading hypotheses for a negative carbon isotopic excursion marking the initiation of the Toarcian OAE using a high-resolution atmospheric carbon dioxide record obtained from fossil leaf stomatal frequency. We find that coincident with the negative carbon-isotope excursion carbon dioxide is first drawn down by 350 +/- 100 p.p.m.v. and then abruptly elevated by 1,200 +/- 400 p.p.m.v, and infer a global cooling and greenhouse warming of 2.5 +/- 0.1 °C and 6.5 +/- 1 °C, respectively. The pattern and magnitude of carbon dioxide change are difficult to reconcile with catastrophic input of isotopically light methane from hydrates5 as the cause of the negative isotopic signal. Our carbon dioxide record better supports a magma-intrusion hypothesis, and suggests that injection of isotopically light carbon from the release of thermogenic methane occurred owing to the intrusion of Gondwana coals by Toarcian-aged Karoo-Ferrar dolerites.” Jennifer C. McElwain, Jessica Wade-Murphy & Stephen P. Hesselbo, Nature 435, 479-482 (26 May 2005), doi:10.1038/nature03618

Mid-Cretaceous pCO2 based on stomata of the extinct conifer Pseudofrenelopsis (Cheirolepidiaceae) – Haworth et al. (2005) “Stomatal characteristics of an extinct Cretaceous conifer, Pseudofrenelopsis parceramosa (Fontaine) Watson, are used to reconstruct atmospheric carbon dioxide (pCO2) over a time previously inferred to exhibit major fluctuations in this greenhouse gas. Samples are from nonmarine to marine strata of the Wealden and Lower Greensand Groups of England and the Potomac Group of the eastern United States, of Hauterivian to Albian age (136–100 Ma). Atmospheric pCO2 is estimated from the ratios between stomatal indices of fossil cuticles and those from four modern analogs (nearest living equivalent plants). Using this approach, and two calibration methods to explore ranges, results show relatively low and only slightly varying pCO2 over the Hauterivian–Albian interval: a low of ∼560–960 ppm in the early Barremian and a high of ∼620–1200 ppm in the Albian. Data from the Barremian Wealden Group yield pCO2 values indistinguishable from a soil-carbonate–based estimate from the same beds. The new pCO2 estimates are compatible with sedimentological and oxygen-isotope evidence for relatively cool mid-Cretaceous climates.” Matthew Haworth, Stephen P. Hesselbo, Jennifer C. McElwain, Stuart A. Robinson and James W. Brunt, Geology, v. 33 no. 9 p. 749-752, doi: 10.1130/G21736.1.

Marked Decline in Atmospheric Carbon Dioxide Concentrations During the Paleogene – Pagani et al. (2005) “The relation between the partial pressure of atmospheric carbon dioxide (pCO2) and Paleogene climate is poorly resolved. We used stable carbon isotopic values of di-unsaturated alkenones extracted from deep sea cores to reconstruct pCO2 fromthe middle Eocene to the late Oligocene (∼45 to 25 million years ago). Our results demonstrate that pCO2 ranged between 1000 to 1500 parts per million by volume in the middle to late Eocene, then decreased in several steps during the Oligocene, and reached modern levels by the latest Oligocene. The fall in pCO2 likely allowed for a critical expansion of ice sheets on Antarctica and promoted conditions that forced the onset of terrestrial C4 photosynthesis.” Mark Pagani, James C. Zachos, Katherine H. Freeman, Brett Tipple and Stephen Bohaty, Science 22 July 2005: Vol. 309 no. 5734 pp. 600-603, DOI: 10.1126/science.1110063. [Full text]

Atmospheric CO2 During the Late Paleozoic and Mesozoic: Estimates from Indian Soils – Ghosh et al. (2005) No abstract. Prosenjit Ghosh, S.K. Bhattacharya and Parthasarathi Ghosh, A History of Atmospheric CO2 and Its Effects on Plants, Animals, and Ecosystems, Ecological Studies, 2005, Volume 177, Part 1., 8-34, DOI: 10.1007/0-387-27048-5_2. [Full text]

Fossil bryophytes as recorders of ancient CO2 levels: Experimental evidence and a Cretaceous case study – Fletcher et al. (2005) “Biological and geochemical CO2 proxies provide critical constraints on understanding the role of atmospheric CO2 in driving climate change during Earth history. As no single existing CO2 proxy is without its limitations, there is a clear need for new approaches to reconstructing past CO2 concentrations. Here we develop a new pre-Quaternary CO2 proxy based on the stable carbon isotope composition (δ13C) of astomatous land plants. In a series of CO2-controlled laboratory experiments, we show that the carbon isotope discrimination (Δ13C) of a range of bryophyte (liverwort and moss) species increases with atmospheric CO2 across the range 375 to 6000 ppm. Separate experiments establish that variations in growth temperature, water content and substrate type have minor impacts on the Δ13C of liverworts but not mosses, indicating the greater potential of liverworts to faithfully record past variations in CO2. A mechanistic model for calculating past CO2 concentrations from bryophyte Δ13C (White et al., 1994) is extended and calibrated using our experimental results. The potential for fossil liverworts to record past CO2 changes is investigated by analyzing the δ13C of specimens collected from Alexander Island, Antarctica dating to the “greenhouse” world of the mid-Cretaceous. Our analysis and isotopic model yield mid-Cretaceous CO2 concentrations of 1000–1400 ppm, in general agreement with independent proxy data and long-term carbon cycle models. The exceptionally long evolutionary history of bryophytes offers the possibility of reconstructing CO2 concentrations back to the mid-Ordovician, pre-dating all currently used quantitative CO2 proxies.” Fletcher, B. J., D. J. Beerling, S. J. Brentnall, and D. L. Royer (2005), Global Biogeochem. Cycles, 19, GB3012, doi:10.1029/2005GB002495. [Full text]

Fe(CO3)OH in goethite from a mid-latitude North American Oxisol: estimate of atmospheric CO2 concentration in the Early Eocene “climatic optimum” – Yapp (2004) “Measured mole fractions (X) and δ13C values of the Fe(CO3)OH component in pedogenic goethite from a mid-latitude Oxisol of Early Eocene age (≈52 Ma B.P.) range from 0.0014 to 0.0064 and −20.1 to −15.4‰, respectively. These values of X imply that concentrations of CO2 gas in the paleosol were ≈7400 to ≈34,000 ppm. δ13C and 1/X are correlated and define a linear, soil-CO2 diffusive mixing line with a positive slope. Such positive slopes are characteristic of mixing of two isotopically distinct CO2 endmembers (atmospheric CO2 and CO2 from oxidation of soil organic matter). From the intercept of the mixing line, it is calculated that the δ 13C value of organic matter in the ancient soil was ≈−28.0‰. The magnitude of the slope implies an Early Eocene atmospheric CO2 concentration of ≈2700 ppm. A simple model for forest soils suggests that a “canopy effect” may cause atmospheric CO2 concentrations deduced from pedogenic minerals to underestimate the actual concentrations of atmospheric CO2. If a significant forest canopy were present at the time of formation of pedogenic goethite in the Ione Fm, the concentration of 2700 ppm calculated for atmospheric CO2 could be slightly low, but the underestimate is expected to be < ≈300 ppm (i.e., less than the analytical uncertainty). The relatively high concentration of 2700 ppm inferred for atmospheric CO2 at ≈52 Ma B.P. would have been coincident with the Early Eocene climatic optimum. This result seems to support the case for an important role for variations of atmospheric CO2 in the modification of global paleoclimate.” Crayton J. Yapp, Geochimica et Cosmochimica Acta, Volume 68, Issue 5, 1 March 2004, Pages 935-947, doi:10.1016/j.gca.2003.09.002.

Goethite, calcite, and organic matter from Permian and Triassic soils: carbon isotopes and CO2 concentrations – Tabor et al. (2004) “Pedogenic goethites in each of two Early Permian paleosols appear to record mixing of two isotopically distinct CO2 components—atmospheric CO2 and CO2 from in situ oxidation of organic matter. The δ13C values measured for the Fe(CO3)OH component in solid solution in these Permian goethites are −13.5‰ for the Lower Leonardian (283 Ma BP) paleosol (MCGoeth) and −13.9‰ for the Upper Leonardian (270 Ma BP) paleosol (SAP). These goethites contain the most 13C-rich Fe(CO3)OH measured to date for pedogenic goethites crystallized in soils exhibiting mixing of the two aforementioned CO2 components. δ13C measured for 43 organic matter samples in the Lower Leonardian (Waggoner Ranch Fm.) has an average value of −20.3 ± 1.1‰ (1s). The average value yields a calculated Early Permian atmospheric Pco2 value of about 1 × PAL, but the scatter in the measured δ13C values of organic matter permits a calculated maximum Pco2 of 11 × PAL (PAL = present atmospheric level). Measured values of the mole fraction of Fe(CO3)OH in MCGoeth and SAP correspond to soil CO2 concentrations in the Early Permian paleosol profiles of 54,000 and 50,000 ppmV, respectively. Such high soil CO2 concentrations are similar to modern soils in warm, wet environments. The average δ13C values of pedogenic calcite from 9 paleosol profiles stratigraphically associated with MCGoeth (Waggoner Ranch Fm.) range from −6.5‰ to −4.4‰, with a mean δ13C value for all profiles of −5.4‰. Thus, the value of Δ13C between the pedogenic calcite data set and MCGoeth is 8.1 (±0.9)‰, which is in reasonable accord with the value of 7.7‰ expected if atmospheric Pco2 and organic matter δ13C values were the same for both paleosol types. Furthermore, the atmospheric Pco2 calculated for the Early Permian from the average measured carbon isotopic compositions of the paleosol calcite and organic matter is also analytically indistinguishable from 1 × PAL, with a maximum calculated atmospheric Pco2 (permitted by one standard deviation of the organic matter δ13C value) of 5 × PAL. If, however, measured average δ13C values of the plant organic matter are more positive than the original soil organic matter as a result of diagenetic loss of 13C-depleted, labile organic compounds, calculated Permian atmospheric Pco2 using these 13C-enriched organic values would underestimate the actual atmospheric Pco2 using either goethite or calcite. This is the first stratigraphically constrained, intrabasinal study to compare ancient atmospheric CO2 concentrations calculated from pedogenic goethite and calcite. These results demonstrate that the two different proxies record the same information about atmospheric CO2. The Fe(CO3)OH component in pedogenic goethite from a Triassic paleosol in Utah is significantly enriched in 13C relative to Fe(CO3)OH in goethites from soils in which there are mixtures of two isotopic CO2 components. Field-relationships and the δ13C value (−1.9‰) of the Triassic goethite indicate that this ancient paleosol profile experienced mixing of three isotopically distinct CO2 components at the time of goethite crystallization. The three components were probably atmospheric CO2, CO2 from in situ oxidation of organic matter and CO2 from in situ dissolution of preexisting calcite. Although mixing of three isotopically distinct CO2 components, as recorded by Fe(CO3)OH in goethite, has been described in modern soil, this is the first example from a documented paleosol. Its preservation affirms the need for careful, case-by-case assessment of ancient paleosols to establish that goethite in any particular soil is likely to be a valid proxy of atmospheric Pco2.” Neil J. Tabor, Crayton J. Yapp and Isabel P. Montañez, Geochimica et Cosmochimica Acta, Volume 68, Issue 7, 1 April 2004, Pages 1503-1517, doi:10.1016/S0016-7037(03)00497-6.

Terrestrial Evidence for Two Greenhouse Events in the Latest Cretaceous – Nordt (2003) “We present a terrestrial record of stable carbon and oxygen isotopes from paleosol carbonate for climate interpretations between ca. 71.0 and 63.6 Ma. Isotopic ratios point to covarying and elevated atmospheric CO2 pressures and temperatures between ca. 70.0 and 69.0 Ma and ca. 65.5 and 65.0 Ma. These two greenhouse episodes were characterized by atmospheric CO2 levels between 1000 and 1400 ppmV (V = volume) and by mean annual temperatures in west Texas between 21 and 23 {degrees}C (~35{degrees}N paleo-latitude). Atmospheric CO2 and temperature relations indicate that a doubling of pCO2 was accompanied by an ~0.6 {degrees}C increase in temperature. A temperature gradient of ~0.4 {degrees}C per degree of latitude is proposed for North America across the Cretaceous-Tertiary boundary when comparing temperature proxies from west Texas with paleobotanical work in North Dakota. Our data demonstrate strong coupling between terrestrial climates and ocean temperatures that were possibly forced by Deccan trap volcanic degassing, leading to dramatic global climate changes.” Lee Nordt, Stacy Atchley, and Steve Dworkin, GSA Today, v. 13(12), p. 4-9. [Full text]

Leaf stomatal frequency in the Australian tropical rainforest tree Neolitsea dealbata (Lauraceae) as a proxy measure of atmospheric pCO2 – Greenwood et al. (2003) “A putative relationship has been demonstrated for European and North American woody dicots and gymnosperms between leaf stomatal frequency and historical levels of atmospheric CO2. However, hitherto no such study has been presented for Australian tropical broadleaved evergreen trees. In this study, variation of stomatal index (SI) along environmental gradients is examined for the broadleaved evergreen tropical rainforest tree Neolitsea dealbata (Lauraceae). Historical herbarium samples from natural populations in northeastern and southeastern Queensland were analysed. Leaf SI for Neolitsea dealbata is shown to be insensitive to mean annual rainfall or seasonal totals, or to temperature variables, indicating the climatic factors that influence the water budget of the plants were not a factor controlling SI. Contrary to the pattern most commonly observed in temperate areas, SI decreased with elevation for collections within a single year for 3 out of 4 years surveyed, a pattern consistent with environmental factors other than pCO2 acting as the control over SI. However, an overall decrease in SI was recorded for samples collected in Queensland (30°–17°S) over the period 1899–1988, corresponding to a Southern Hemisphere increase in pCO2 from 295 to 350 ppm. Restricting the analysis to sites within an altitudinal band of 640–1120 m demonstrated a significant relationship between SI and pCO2 (r2=0.8942, F11=84.5, P<0.001). This data set was used to estimate atmospheric pCO2 from fossil leaf cuticle for the closely related genus Litsea, giving pCO2 values comparable to those estimated using Ginkgo from Northern Hemisphere fossil sites.” David R. Greenwood, Mark J. Scarr and David C. Christophel, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 196, Issues 3-4, 1 August 2003, Pages 375-393, doi:10.1016/S0031-0182(03)00465-6. [Full text]

Atmospheric pCO2 since 60 Ma from records of seawater pH, calcium, and primary carbonate mineralogy – Demicco et al. (2003) “A 60 m.y. record of atmospheric pCO2 has been refined from knowledge of (1) secular changes in the major ion composition of seawater (particularly Ca and Mg) and (2) oscillations in the mineralogy of primary oceanic carbonate sediments. Both factors have had a significant impact on the chemistry of the ocean carbonate buffer system. Calculated atmospheric pCO2 oscillated between values of 100–300 ppm and to maxima of 1200–2500 ppm from 60 to 40 Ma and varied between 100 and 300 ppm from 25 Ma to the present. The refined pCO2 values are significantly lower than previous estimates made from seawater pH data where total dissolved inorganic carbon was assumed constant and more in line with modeling and stomatal index estimations of atmospheric pCO2 for the Tertiary.” Robert V. Demicco, Tim K. Lowenstein and Lawrence A. Hardie, Geology, v. 31 no. 9 p. 793-796, doi: 10.1130/G19727.1. [Full text]

Atmospheric pCO2 and depositional environment from stable-isotope geochemistry of calcrete nodules (Barremian, Lower Cretaceous, Wealden Beds, England) – Robinson et al. (2002) “Nodular soil carbonates (calcretes) are present in overbank facies of Lower Cretaceous, non-marine Wealden Beds (Wessex Formation) of southern England. Field evidence suggests that these calcretes formed mostly under semi-arid Mediterranean-type climatic conditions. Typical calcrete fabrics, identified petrographically, include floating detrital grains, corroded grain margins and circumgranular cracks defining peds. Localized alteration of primary micrites is mainly associated with large cracks where early non-ferroan diagenetic cementation and neomorphism was focused. Diagenetic ferroan calcites occur as void fills and yield relatively light carbon-isotope and oxygen-isotope compositions (δ13C= –15.0‰; δ18O= –6.3‰) compared to well-preserved micrite (δ13C= –10.2‰; δ18O= –4.0‰). Precise definition of δ13C values for well-preserved micrites allow estimation of partial pressure of atmospheric CO2 (pCO2) for the early Barremian of 560 ppmV using a published diffusion-reaction model. The data suggest that atmospheric CO2 was low during the mid-Early Cretaceous before rising to a previously defined mid-Cretaceous high. Data from calcretes in the Weald Clay highlight the need for selection of appropriate material and careful evaluation before pCO2 calculations are attempted. The Weald Clay samples come from marshy palaeoenvironments where ingress of atmospheric CO2 into the soil-zone was either reduced or prevented.” Stuart A. Robinson, Julian E. Andrews, Stephen P. Hesselbo, Jonathan D. Radley, Paul F. Dennis, Ian C. Harding & Perce Allen, Journal of the Geological Society; 2002; v. 159; issue.2; p. 215-224; DOI: 10.1144/0016-764901-015. [Full text]

Paleosol barometer indicates extreme fluctuations in atmospheric CO2 across the Cretaceous-Tertiary boundary – Nordt et al. (2002) “We present an atmospheric pCO2 (p is partial pressure) curve showing extreme fluctuations for the interval between ca. 77 and 63 Ma in southern Alberta, Canada, using a paleosol barometer. Paleosol carbonate nodules (micrite) were collected from 40 Bk horizons among 6 stratigraphic sections for stable carbon isotope analysis. Based on results from the study area, declining atmospheric pCO2 from 1200 ppmV (V is volume) in the Campanian to 780 ppmV in the Maastrichtian correlates with Late Cretaceous climate cooling and falling sea level as documented in global records. The remarkable rise in atmospheric pCO2 near 65.5 Ma (1440 ppmV) correlates with volcanic activity associated with the Deccan Traps, rising sea level, and warmer global climates. The decline in atmospheric pCO2 (760 ppmV) at the Cretaceous-Tertiary boundary and subsequent sharp rise into the Danian (1000 ppmV) occurred during static terrestrial temperatures and sea level. This work provides compelling evidence that atmospheric pCO2 curves modeled for the Phanerozoic do not offer the resolution needed to understand environmental conditions during catastrophic events in Earth’s history.” Lee Nordt, Stacy Atchley and S.I. Dworkin, Geology, v. 30 no. 8 p. 703-706, doi: 10.1130/0091-7613(2002).

Fossil plants as indicators of the Phanerozoic global carbon cycle – Beerling & Royer (2002) “Developments in plant physiology since the 1980s have led to the realization that fossil plants archive both the isotopic composition of atmospheric CO2 and its concentration, both critical integrators of carbon cycle processes through geologic time. These two carbon cycle signals can be read by analyzing the stable carbon isotope composition (δ13C) of fossilized terrestrial organic matter and by determining the stomatal characters of well-preserved fossil leaves, respectively. We critically evaluate the use of fossil plants in this way at abrupt climatic boundaries associated with mass extinctions and during times of extreme global warmth. Particular emphasis is placed on evaluating the potential to extract a quantitative estimate of the δ13C of atmospheric CO2 because of the key role it plays in understanding the carbon cycle. We critically discuss the use of stomatal index and stomatal ratios for reconstructing atmospheric CO2 levels, especially the need for adequate replication, and present a newly derived CO2 record for the Mesozoic that supports levels calculated from geochemical modeling of the long-term carbon cycle. Several suggestions for future research using stable carbon isotope analyses of fossil terrestrial organic matter and stomatal measurements are highlighted.” D.J. Beerling and D.L. Royer, Annual Review of Earth and Planetary Sciences, Vol. 30: 527-556 (Volume publication date May 2002), DOI: 10.1146/annurev.earth.30.091201.141413. [Full text]

An atmospheric pCO2 reconstruction across the Cretaceous-Tertiary boundary from leaf megafossils – Beerling et al. (2002) “The end-Cretaceous mass extinctions, 65 million years ago, profoundly influenced the course of biotic evolution. These extinctions coincided with a major extraterrestrial impact event and massive volcanism in India. Determining the relative importance of each event as a driver of environmental and biotic change across the Cretaceous-Tertiary boundary (KTB) crucially depends on constraining the mass of CO2 injected into the atmospheric carbon reservoir. Using the inverse relationship between atmospheric CO2 and the stomatal index of land plant leaves, we reconstruct Late Cretaceous-Early Tertiary atmospheric CO2 concentration (pCO2) levels with special emphasis on providing a pCO2 estimate directly above the KTB. Our record shows stable Late Cretaceous/Early Tertiary background pCO2 levels of 350–500 ppm by volume, but with a marked increase to at least 2,300 ppm by volume within 10,000 years of the KTB. Numerical simulations with a global biogeochemical carbon cycle model indicate that CO2 outgassing during the eruption of the Deccan Trap basalts fails to fully account for the inferred pCO2 increase. Instead, we calculate that the postboundary pCO2 rise is most consistent with the instantaneous transfer of ≈4,600 Gt C from the lithic to the atmospheric reservoir by a large extraterrestrial bolide impact. A resultant climatic forcing of +12 W m−2 would have been sufficient to warm the Earth’s surface by ≈7.5°C, in the absence of counter forcing by sulfate aerosols. This finding reinforces previous evidence for major climatic warming after the KTB impact and implies that severe and abrupt global warming during the earliest Paleocene was an important factor in biotic extinction at the KTB.” D. J. Beerling, B. H. Lomax, D. L. Royer, G. R. Upchurch, Jr., and L. R. Kump, PNAS June 11, 2002 vol. 99 no. 12 7836-7840, doi: 10.1073/pnas.122573099. [Full text]

Low atmospheric CO2 levels during the Permo- Carboniferous glaciation inferred from fossil lycopsids – Beerling (2002) “Earth history was punctuated during the Permo-Carboniferous [300–250 million years (Myr) ago] by the longest and most severe glaciation of the entire Phanerozoic Eon. But significant uncertainty surrounds the concentration of CO2 in the atmosphere through this time interval and therefore its role in the evolution of this major prePleistocene glaciation. Here, I derive 24 Late Paleozoic CO2 estimates from the fossil cuticle record of arborsecent lycopsids of the equatorial Carboniferous and Permian swamp communities. Quantitative calibration of Late Carboniferous (330–300 Myr ago) and Permian (270–260 Myr ago) lycopsid stomatal indices yield average atmospheric CO2 concentrations of 344 ppm and 313 ppm, respectively. The reconstructions show a high degree of self-consistency and a degree of precision an order of magnitude greater than other approaches. Low CO2 levels during the Permo-Carboniferous glaciation are in agreement with glaciological evidence for the presence of continental ice and coupled models of climate and ice-sheet growth on Pangea. Moreover, the Permian data indicate atmospheric CO2 levels were low 260 Myr ago, by which time continental deglaciation was already underway. Positive biotic feedbacks on climate, and geotectonic events, therefore are implicated as mechanisms underlying deglaciation.” D. J. Beerling, PNAS October 1, 2002 vol. 99 no. 20 12567-12571, doi: 10.1073/pnas.202304999 . [Full text]

Stability of atmospheric CO2 levels across the Triassic/Jurassic boundary – Tanner et al. (2001) “The Triassic/Jurassic boundary, 208 million years ago, is associated with widespread extinctions in both the marine and terrestrial biota. The cause of these extinctions has been widely attributed to the eruption of flood basalts of the Central Atlantic Magmatic Province. This volcanic event is thought to have released significant amounts of CO2 into the atmosphere, which could have led to catastrophic greenhouse warming, but the evidence for CO2-induced extinction remains equivocal. Here we present the carbon isotope compositions of pedogenic calcite from palaeosol formations, spanning a 20-Myr period across the Triassic/Jurassic boundary. Using a standard diffusion model, we interpret these isotopic data to represent a rise in atmospheric CO2 concentrations of about 250 p.p.m. across the boundary, as compared with previous estimates of a 2,000–4,000 p.p.m. increase. The relative stability of atmospheric CO2 across this boundary suggests that environmental degradation and extinctions during the Early Jurassic were not caused by volcanic outgassing of CO2. Other volcanic effects—such as the release of atmospheric aerosols or tectonically driven sea-level change—may have been responsible for this event.” Lawrence H. Tanner, John F. Hubert, Brian P. Coffey & Dennis P. McInerney, Nature 411, 675-677 (7 June 2001) | doi:10.1038/35079548.

A 300-million-year record of atmospheric carbon dioxide from fossil plant cuticles – Retallack (2001) “To understand better the link between atmospheric CO2 concentrations and climate over geological time, records of past CO2 are reconstructed from geochemical proxies. Although these records have provided us with a broad picture of CO2 variation throughout the Phanerozoic eon (the past 544 Myr), inconsistencies and gaps remain that still need to be resolved. Here I present a continuous 300-Myr record of stomatal abundance from fossil leaves of four genera of plants that are closely related to the present-day Ginkgo tree. Using the known relationship between leaf stomatal abundance and growing season CO2 concentrations I reconstruct past atmospheric CO2 concentrations. For the past 300 Myr, only two intervals of low CO2 (<1,000 p.p.m.v.) are inferred, both of which coincide with known ice ages in Neogene (1–8 Myr) and early Permian (275–290 Myr) times. But for most of the Mesozoic era (65–250 Myr), CO2 levels were high (1,000–2,000 p.p.m.v.), with transient excursions to even higher CO2 (>2,000 p.p.m.v.) concentrations. These results are consistent with some reconstructions of past CO2 (refs 1, 2) and palaeotemperature records, but suggest that CO2 reconstructions based on carbon isotope proxies may be compromised by episodic outbursts of isotopically light methane. These results support the role of water vapour, methane and CO2 in greenhouse climate warming over the past 300 Myr.” Gregory J. Retallack, Nature 411, 287-290 (17 May 2001) | doi:10.1038/35077041. [Full text]

CO2 levels in the Late Palaeozoic and Mesozoic atmosphere from soil carbonate and organic matter, Satpura basin, Central India – Ghosh et al. (2001) “A number of calcic palaeosols have been identified within the fluvial deposits of the Motur (Permian), the Denwa (Triassic), the Bagra (Jurassic) and the Lameta (Cretaceous) Formations of the Satpura sedimentary succession, Central India. These palaeosols show accumulation of pedogenic carbonates in rhizocretions and glaebules. The carbon isotopic compositions of these carbonates and the coexisting soil organic matters are used to determine the isotopic composition and the partial pressure of atmospheric CO2 using the CO2 palaeobarometer developed by Cerling [Am. J. Sci., 291 (1991) 377]. It is seen that the atmospheric CO2 level increased by a factor of 8 from the Permian to the Jurassic and declined again during the Cretaceous. The nature of the changes agrees with the result of the CO2 evolution model of Berner (GEOCARB II) but the magnitude of the CO2 increase in the Middle Jurassic and the Late Cretaceous was higher than the predicted value. Degassing of Earth’s interior due to rapid break-up of the Gondwana landmass during the Triassic and Jurassic period could have caused the rapid CO2 increase.” Prosenjit Ghosh, P Ghosh and S.K Bhattacharya, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 170, Issues 3-4, 15 June 2001, Pages 219-236, doi:10.1016/S0031-0182(01)00237-1. [Full text]

Paleobotanical Evidence for Near Present-Day Levels of Atmospheric CO2 During Part of the Tertiary – Royer et al. (2001) “Understanding the link between the greenhouse gas carbon dioxide (CO2) and Earth’s temperature underpins much of paleoclimatology and our predictions of future global warming. Here, we use the inverse relationship between leaf stomatal indices and the partial pressure of CO2 in modern Ginkgo bilobaand Metasequoia glyptostroboides to develop a CO2 reconstruction based on fossil Ginkgo andMetasequoia cuticles for the middle Paleocene to early Eocene and middle Miocene. Our reconstruction indicates that CO2 remained between 300 and 450 parts per million by volume for these intervals with the exception of a single high estimate near the Paleocene/Eocene boundary. These results suggest that factors in addition to CO2 are required to explain these past intervals of global warmth.” Dana L. Royer, Scott L. Wing, David J. Beerling, David W. Jolley, Paul L. Koch, Leo J. Hickey and Robert A. Berner, Science 22 June 2001: Vol. 292 no. 5525 pp. 2310-2313, DOI: 10.1126/science.292.5525.2310. [Full text]

Atmospheric carbon dioxide concentrations over the past 60 million years – Pearson & Palmer (2000) “Knowledge of the evolution of atmospheric carbon dioxide concentrations throughout the Earth’s history is important for a reconstruction of the links between climate and radiative forcing of the Earth’s surface temperatures. Although atmospheric carbon dioxide concentrations in the early Cenozoic era (about 60 Myr ago) are widely believed to have been higher than at present, there is disagreement regarding the exact carbon dioxide levels, the timing of the decline and the mechanisms that are most important for the control of CO2 concentrations over geological timescales. Here we use the boron-isotope ratios of ancient planktonic foraminifer shells to estimate the pH of surface-layer sea water throughout the past 60 million years, which can be used to reconstruct atmospheric CO2 concentrations. We estimate CO2 concentrations of more than 2,000 p.p.m. for the late Palaeocene and earliest Eocene periods (from about 60 to 52 Myr ago), and find an erratic decline between 55 and 40 Myr ago that may have been caused by reduced CO2 outgassing from ocean ridges, volcanoes and metamorphic belts and increased carbon burial. Since the early Miocene (about 24 Myr ago), atmospheric CO2 concentrations appear to have remained below 500 p.p.m. and were more stable than before, although transient intervals of CO2 reduction may have occurred during periods of rapid cooling approximately 15 and 3 Myr ago.” Paul N. Pearson & Martin R. Palmer, Nature 406, 695-699 (17 August 2000), doi:10.1038/35021000. [Full text]

Fossil Plants and Global Warming at the Triassic-Jurassic Boundary – McElwain et al. (1999) “The Triassic-Jurassic boundary marks a major faunal mass extinction, but records of accompanying environmental changes are limited. Paleobotanical evidence indicates a fourfold increase in atmospheric carbon dioxide concentration and suggests an associated 3° to 4°C “greenhouse” warming across the boundary. These environmental conditions are calculated to have raised leaf temperatures above a highly conserved lethal limit, perhaps contributing to the >95 percent species-level turnover of Triassic-Jurassic megaflora.” J. C. McElwain, D. J. Beerling and F. I. Woodward, Science 27 August 1999: Vol. 285 no. 5432 pp. 1386-1390, DOI: 10.1126/science.285.5432.1386.

Stable isotopic composition of pedogenic carbonates of the Early Cretaceous Shimonoseki Subgroup, western Honshu, Japan – Lee & Hisada (1999) “Abundant pedogenic carbonate nodules are present in the Shimonoseki Subgroup in the Kanmon Basin of Kyushu and Honshu, Japan. The oxygen isotope compositions of these pedogenic carbonates range from −20.1 to −22.8‰ (PDB), which is 7‰ lower than those of the septarian crystallaria in the carbonate nodules. The meteoric water composition estimated from the oxygen isotope composition of the soil water in equilibrium with the carbonates is much depleted compared with the estimate from other sources. This suggests that the oxygen isotope compositions of the Shimonoseki pedogenic carbonates were modified during diagenesis. The carbon isotopic compositions of the Shimonoseki carbonates range from −5.4 to −7.0‰ (PDB), with an average of −6.7‰ (PDB), suggesting carbonate formation in soils dominated by C3 type of vegetation. An analysis of these values using Cerling’s model (Cerling, T.E., Wright, V.P., Vanstone, S.D., 1992. Further comments on using carbon isotopes in paleosols to estimate the CO2 content of the palaeo-atmosphere. J. Geol. Soc. London 148 (1991), 945–947; 149, 673–676) indicates that the partial pressure of CO2 in the Early Cretaceous Shimonoseki atmosphere was about 1700–3200 ppmV.” Yong Il Lee and Ken-ichiro Hisada, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 153, Issues 1-4, 15 September 1999, Pages 127-138, doi:10.1016/S0031-0182(99)00069-3.

Late Miocene Atmospheric CO2 Concentrations and the Expansion of C4 Grasses – Pagani et al. (1999) “The global expansion of C4 grasslands in the late Miocene has been attributed to a large-scale decrease in atmospheric carbon dioxide (CO2) concentrations. This triggering mechanism is controversial, in part because of a lack of direct evidence for change in the partial pressure of CO2(pCO2) and because other factors are also important determinants in controlling plant-type distributions. Alkenone-based pCO2 estimates for the late Miocene indicate that pCO2 increased from 14 to 9 million years ago and stabilized at preindustrial values by 9 million years ago. The estimates presented here provide no evidence for major changes in pCO2 during the late Miocene. Thus, C4 plant expansion was likely driven by additional factors, possibly a tectonically related episode of enhanced low-latitude aridity or changes in seasonal precipitation patterns on a global scale (or both).” Mark Pagani, Katherine H. Freeman and Michael A. Arthur, Science 6 August 1999: Vol. 285 no. 5429 pp. 876-879, DOI: 10.1126/science.285.5429.876.

Miocene evolution of atmospheric carbon dioxide – Pagani et al. (1999) “Changes in pCO2 or ocean circulation are generally invoked to explain warm early Miocene climates and a rapid East Antarctic ice sheet (EAIS) expansion in the middle Miocene. This study reconstructs late Oligocene to late Miocene pCO2 from εp values based on carbon isotopic analyses of diunsaturated alkenones and planktonic foraminifera from Deep Sea Drilling Project sites 588 and 608 and Ocean Drilling Program site 730. Our results indicate that highest pCO2 occurred during the latest Oligocene (∼350 ppmv) but decreased rapidly at ∼25 Ma. The early and middle Miocene was characterized by low pCO2 (260–190 ppmv). Lower intervals of pCO2 correspond to inferred organic carbon burial events and glacial episodes with the lowest concentrations occurring during the middle Miocene. There is no evidence for either high pCO2 during the late early Miocene climatic optimum or a sharp pCO2 decrease associated with EAIS growth. Paradoxically, pCO2 increased following EAIS growth and obtained preindustrial levels by ∼10 Ma. Although we emphasize an oceanographic control on Miocene climate, low pCO2 could have primed the climate system to respond sensitively to changes in heat and vapor transport” Pagani, M., M. A. Arthur, and K. H. Freeman (1999), Paleoceanography, 14(3), 273–292, doi:10.1029/1999PA900006. [Full text]

Stable isotopic composition of calcic paleosols of the Early Cretaceous Hasandong Formation, southeastern Korea – Lee (1999) “Abundant pedogenic carbonate nodules are present in the Cretaceous non-marine Hasandong Formation, southeastern Korea. The oxygen isotope compositions of these pedogenic carbonates range from −14.2 to −18.0‰ (PDB). The meteoric water composition estimated from the oxygen isotope composition of the soil-water in equilibrium with the carbonates is much depleted compared with the previous estimate. This suggests that the oxygen isotope compositions of the Hasandong pedogenic carbonates were modified during diagenesis. The carbon isotopic compositions of the Hasandong carbonates range from −2.4 to −9.3‰ (PDB) with an average of −5.6‰ (PDB) suggesting carbonate formation in soils dominated by C3 type of vegetation. The estimated average composition of the vegetation is about 6‰ (PDB) enriched compared with the present-day C3 vegetation. This is probably due to atmospheric influence contributing about 35% of the total CO2 in the soil. An analysis of this contribution using the model of Cerling (1991) indicates that the partial pressure of CO2 in the Early Cretaceous Hasandong atmosphere was about 2300 ppmV.” Yong Il Lee, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 150, Issues 1-2, 15 June 1999, Pages 123-133, doi:10.1016/S0031-0182(99)00010-3. [Full text]

Do fossil plants signal palaeoatmospheric carbon dioxide concentration in the geological past? – McElwain (1998) “Fossil, subfossil, and herbarium leaves have been shown to provide a morphological signal of the atmospheric carbon dioxide environment in which they developed by means of their stomatal density and index. An inverse relationship between stomatal density/index and atmospheric carbon dioxide concentration has been documented for all the studies to date concerning fossil and subfossil material. Furthermore, this relationship has been demonstrated experimentally by growing plants under elevated and reducedcarbon dioxide concentrations. To date, the mechanism that controls the stomatal density response to atmospheric carbon dioxide concentration remains unknown. However, stomatal parameters of fossil plants have been successfully used as a proxy indicator of palaeo–carbon dioxide levels. This paper presents new estimates of palaeo–atmospheric carbon dioxide concentrations for the Middle Eocene (Lutetian), based on the stomatal ratios of fossil Lauraceae species from Bournemouth in England. Estimates of atmospheric carbon dioxide concentrations derived from stomatal data from plants of the Early Devonian, Late Carboniferous, Early Permian and Middle Jurassic ages are reviewed in the light of new data. Semi–quantitative palaeo–carbon dioxide estimates based on the stomatal ratio (a ratio of the stomatal index of a fossil plant to that of a selected nearest living equivalent) have in the past relied on the use of a Carboniferous standard. The application of a new standard based on the present–day carbon dioxide level is reported here for comparison. The resultant ranges of palaeo–carbon dioxide estimates made from standardized fossil stomatal ratio data are in good agreement with both carbon isotopic data from terrestrial and marine sources and long–term carbon cycle modelling estimates for all the time periods studied. These data indicate elevated atmospheric carbon dioxide concentrations during the Early Devonian, Middle Jurassic and Middle Eocene, and reduced concentrations during the Late Carboniferous and Early Permian. Such data are important in demonstrating the long–term responses of plants to changing carbon dioxide concentrations and in contributing to the database needed for general circulation model climatic analogues.” Phil. Trans. R. Soc. Lond. B 29 January 1998 vol. 353 no. 1365 83-96, doi: 10.1098/rstb.1998.0193. [Full text]

Carbon isotopes in continental weathering environments and variations in ancient atmospheric CO2 pressure – Yapp & Poths (1996) “Abundance and carbon isotope data from an Fe(CO3)OH component in apparent solid solution in oolitic goethites have been used to infer ancient atmospheric CO2 pressures. A test of the validity of these estimates might be comparisons of the carbon isotope compositions of Fe(CO3)OH in oolitic goethites with time-equivalent pedogenic calcites. Temporal trends of the oolitic goethite and pedogenic calcite δ13C values are generally similar, but time-equivalent samples from each of these two groups are not common in the existing data. To facilitate discussion of the concept, comparisons were made of available goethite and calcite samples even though ages of the compared samples in each pair were not identical. In four out of the five comparisons, Fe(CO3)OH abundance and δ13C data were combined with pedogenic calcite δ13C data to calculate physically reasonable soil CO2 concentrations for the ancient calcitic soids. This suggests that the compared oolitic goethite and pedogenic calcite systems were responding to the same global scale phenomenon (i.e., atmospheric CO2). Atmospheric PCO2 as determined from the goethites in these four “well-behaved” cases ranged from values indistinguishable from modern (within analytical uncertainty) to values up to approximately 16 time modern (modern atmospheric PCO2 was taken to be 10−3.5 atm). One interpretation of the fifth, “anomalous”, comparison is that atmospheric CO2 levels increased from about 3 times modern to about 18 times modern from the Triassic into the Early Jurassic. This inferred value for the PCO2 of the Early Jurassic atmosphere is not uniquely constrained by the existing data and needs to be substantiated. However, even considerably lower Early Jurassic atmospheric PCO2 values of 6 to 9 times modern (i.e., 1/3 to 1/2 of the estimated value of 18 times modern) would still indicate significant differences between the global carbon cycles then and now. These results highlight the need for more research on the behavior of the atmosphere during and after the Triassic-Jurassic transition.” Crayton J. Yapp and Harald Poths, Earth and Planetary Science Letters, Volume 137, Issues 1-4, January 1996, Pages 71-82, doi:10.1016/0012-821X(95)00213-V.

Middle to Late Paleozoic Atmospheric CO2 Levels from Soil Carbonate and Organic Matter – Mora et al. (1996) “The stable carbon isotope compositions of ancient soil carbonate and coexisting soil organic matter indicate that atmospheric CO2 levels decreased by a factor of 10 during the middle to late Paleozoic era. Proxy measurements of CO2 were made by application of a soil carbonate CO2 paleobarometer to a suite of paleosols that share key physical and chemical characteristics. The estimates agree with theoretical models that imply that a decrease in Paleozoic atmospheric CO2 levels was associated with afforestation of the land surface by terrestrial plants and with global climate change leading to the extensive Permo-Carboniferous glaciation.” Claudia I. Mora, Steven G. Driese and Lee Ann Colarusso, Science 23 February 1996: Vol. 271 no. 5252 pp. 1105-1107, DOI: 10.1126/science.271.5252.1105.

A 400 million year carbon isotope record of pedogenic carbonate; implications for paleoatomospheric carbon dioxide – Ekart et al. (1995) “A 400 record of atmospheric carbon dioxide levels has been estimated by applying a CO2 paleobarometer to a database of 758 analyses of paleosol (fossil soil) carbonates. This database is a compilation of new data and previously published values from the literature. Many new analyses of Mesozoic paleosols are reported, an era poorly represented in the literature. Results indicate that large fluctuations in atmospheric carbon dioxide levels have occurred over the study interval, ranging from the current level up to ten times the current level. Declining pCO2 levels through the middle Paleozoic culminate in low levels in the Early Permian. An abrupt increase in pCO{sub 2} in the Early Permian is followed by a decrease prior to the Permo-Triassic boundary. Carbon dioxide levels increase through the Triassic to approx. 3,000 ppmV, a level maintained through the Jurassic period. Levels lowered through the Cretaceous, dropping to less than 1,000 ppmV prior to the Cretaceous-Tertiary boundary. Relatively low levels persisted throughout the Cenozoic, with some evidence of higher levels in the Eocene and Oligocene.” Douglas D. Ekart, Thure E. Cerling, Isabel P. Montanez, and Neil J. Tabor, American Journal of Science, Vol. 299, December 1999, P.805-827; doi:10.2475/ajs.299.10.805. [Full text]

Concentration of carbon dioxide in the Late Cretaceous atmosphere – Andrews et al. (1995) “Stable carbon isotope data from Late Cretaceous (Maastrichtian) palaeosols in India are used to estimate the concentration of carbon dioxide in the Late Cretaceous atmosphere. We show that the Maastrichtian atmosphere is unlikely to have contained more than about 1300 ppm by volume of CO2.This value agrees with an independently modeled value of CO2 in the Late Cretaceous atmosphere. A low concentration of the greenhouse gas carbon dioxide in the Maastrichtian atmosphere (relative to concentrations in the earlier Cretaceous) is consistent with palaeotemperature information from terrestrial plant and marine fossils, which suggest that the global climate cooled toward the end of the Cretaceous Period.” Andrews, J.E., Tandon, S.K., and Dennis, P.F. 1995, Journal of the Geological Society, London, v. 152, p. 1-3, DOI: 10.1144/gsjgs.152.1.0001.

Stomatal Density and Index of Fossil Plants Track Atmospheric Carbon Dioxide in the Palaeozoic – McElwain & Chaloner (1995) “It has been demonstrated that the leaves of a range of forest tree species have responded to the rising concentration of atmospheric CO2 over the last 200 years by a decrease in both stomatal density and stomatal index. This response has also been demonstrated experimentally by growing plants under elevated CO2 concentrations. Investigation of Quaternary fossil leaves has shown a corresponding stomatal response to changing CO2 concentrations through a glacial-interglacial cycle, as revealed by ice core data. Tertiary leaves show a similar pattern of stomatal density change, using palynological evidence of palaeo-temperature as a proxy measure of CO2 concentration. The present work extends this approach into the Palaeozoic fossil plant record. The stomatal density and index of Early Devonian, Carboniferous and Early Permian plants has been investigated, to test for any relationship that they may show with the changes in atmospheric CO2 concentration, derived from physical evidence, over that period. Observed changes in the stomatal data give support to the suggestion from physical evidence, that atmospheric CO2 concentrations fell from an Early Devonian high of 10-12 times its present value, to one comparable to that of the present day by the end of the Carboniferous. These results suggest that stomatal density of fossil leaves has potential value for assessing changes in atmospheric CO2 concentration through geological time.” Jennifer C. McElwain and William G. Chaloner, Ann Bot (1995) 76 (4): 389-395, doi: 10.1006/anbo.1995.1112. [Full text]

Palaeoclimate and palaeovegetation in central India during the Upper Cretaceous based on stable isotope composition of the palaeosol carbonates – Ghosh et al. (1995) “The oxygen isotope compositions of the pedogenic carbonates formed on the sediments of the Lameta Formation of Central India during the Upper Cretaceous range from −6.7 to −8.9‰. Estimates of the oxygen isotope composition of the soil-water in equilibrium with the carbonates suggest average meteoric water composition of −8‰. This value is considerably lighter compared to the modern precipitation in Central India (−3‰). The lighter oxygen isotope composition can be explained in terms of cumulative effects of highly seasonal (monsoon-like) climatic regime in a rain shadow zone and a more pronounced “continental effect” due to a bigger size of Cretaceous India. The carbon isotopic compositions of the Lameta carbonates range from −7.1 to −10.7 with an average of −9.1‰ suggesting pedogenesis in soils dominated by C3 type of vegetation. The estimated average composition of the vegetation is about 3‰ enriched compared to the modern day C3 vegetation. This is probably due to atmospheric influence contributing about 15% of the total CO2 in the soil. An analysis of this contribution using the model of Cerling (1991) indicates that the partial pressure of CO2 in the Late Cretaceous atmosphere was 800 – 12,000 ppmV” P. Ghosh, S.K.Bhattacharya and R.A. Jani, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 114, Issues 2-4, April 1995, Pages 285-296, doi:10.1016/0031-0182(94)00082-J.

New atmospheric pCO2 estimates from palesols during the late Paleocene/early Eocene global warming interval – Sinha & Stott (1994) “The late Paleocene to early Eocene was one of the warmest intervals in Earth’s history. Superimposed on this long-term warming was an abrupt short-term extreme warm event at or near the Paleocene/Eocene boundary and centered in the higher latitudes. This short-term climate warming was associated with a major benthic foraminiferal extinction and a dramatic 3–4% drop in the ocean’s carbon isotopic composition. It has been suggested that the late paleocene/early Eocene global warming was caused by an enhanced greenhouse effect associated with higher levels of atmospheric CO2 relative to present levels. We present carbon isotopic data from the co-existing paleosols organic matter and carbonates from a terrestrial sequence in the Paris Basin, France that contradict the notion that an increase in atmospheric CO2 level was the cause of extreme warming for this time interval. Atmospheric pCO2 estimates for the Late Paleocene/early Eocene estimated from the terrestrial carbon isotopic record spanning the Paleocene/Eocene transition, are indistinguishable from each other and were generally between 300 and 700 ppm.” Ashish Sinha and Lowell D. Stott, Global and Planetary Change, Volume 9, Issues 3-4, December 1994, Pages 297-307, doi:10.1016/0921-8181(94)00010-7.

Paleoatmospheric Signatures in Neogene Fossil Leaves – Van Der Burgh et al. (1993) “An increase in the atmospheric carbon dioxide (CO2) concentration results in a decrease in the number of leaf stomata. This relation is known both from historical observations of vegetation over the past 200 years and from experimental manipulations of microenvironments. Evidence from stomatal frequencies of fossil Quercus petraea leaves indicates that this relation can be applied as a bioindicator for changes in paleoatmospheric CO2 concentrations during the last 10 million years. The data suggest that late Neogene CO2 concentrations fluctuated between about 280 and 370 parts per million by volume.” Johan Van Der Burgh, Henk Visscher, David L. Dilcher and Wolfram M. Kürschner, Science 18 June 1993: Vol. 260 no. 5115 pp. 1788-1790, DOI: 10.1126/science.260.5115.1788.

Fractionation of carbon isotopes by phytoplankton and estimates of ancient CO2 levels – Freeman & Hayes (1992) “Reports of the 13C content of marine particulate organic carbon are compiled and on the basis of GEOSECS data and temperatures, concentrations, and isotopic compositions of dissolved CO2 in the waters in which the related phytoplankton grew are estimated. In this way, the fractionation of carbon isotopes during photosynthetic fixation of CO2 is found to be significantly correlated with concentrations of dissolved CO2. Because ancient carbon isotopic fractionations have been determined from analyses of sedimentary porphyrins [Popp et al., 1989], the relationship between isotopic fractionation and concentrations of dissolved CO2 developed here can be employed to estimate concentrations of CO2 dissolved in ancient oceans and, in turn, partial pressures of CO2 in ancient atmospheres. The calculations take into account the temperature dependence of chemical and isotopic equilibria in the dissolved-inorganic-carbon system and of air-sea equilibria. Paleoenvironmental temperatures for each sample are estimated from re-constructions of paleogeography, latitudinal temper- ature gradients, and secular changes in low-latitude sea surface temperature. It is estimated that atmospheric partial pressures of CO2 were over 1000 μatm 160–100 Ma ago, then declined to values near 300 μatm during the next 100 Ma. Analysis of a high-resolution record of carbon isotopic fractionation at the Cenomanian-Turonian boundary suggests that the partial pressure of CO2 in the atmosphere was drawn down from values near 840 μatm to values near 700 μatm during the anoxic event.” Freeman, K. H., and J. M. Hayes (1992), Global Biogeochem. Cycles, 6(2), 185–198, doi:10.1029/92GB00190.

Correlation between isotope records in marine and continental carbon reservoirs near the Palaeocene/Eocene boundary – Koch et al. (1992) “CHANGES in the isotope content of the large marine carbon reservoir can force shifts in that of the smaller carbon pools in the atmosphere and on land. The carbon isotope compositions of marine carbonate sediments from the late Palaeocene vary considerably, exhibiting a sudden decrease close to the Palaeocene/Eocene boundary which coincides with deep-sea benthic extinctions1 and with changes in ocean circulation. Here we report that these fluctuations in the marine carbon isotope record are closely tracked by the terrestrial records provided by palaeosol carbonates and mammalian tooth enamel. In using palaeosol carbonates to reconstruct the CO2 content of the ancient atmosphere2, isotope shifts of this sort will have to be taken into account. The sharp decrease in 13C/12C ratios in the late Palaeocene provides a datum for precise correlation of marine and continental records, and suggests that abrupt climate warming at this time may have played an important role in the evolution of land mammals.” Paul L. Koch, James C. Zachos & Philip D. Gingerich, Nature 358, 319 – 322 (23 July 1992); doi:10.1038/358319a0. [Full text]

Higher temperatures and lower oceanic pCO2: A climate enigma at the end of the Paleocene Epoch – Stott (1992) “One of the largest and most abrupt climatic warming events documented in the geologic record occurred at the end of the Paleocene epoch. Oceanic deep waters warmed to 10°C, and high-latitude surface waters warmed from ∼10°C to ∼20°C within several thousand years. This coincided with weakened atmospheric circulation and the extinction of ∼50% of deep-sea benthic foraminiferal species. It has been suggested that this warm excursion was forced by higher atmospheric pCO2 and greenhouse effects caused by a pulse of hydrothermal activity and/or volcanism. Stable isotopic evidence is presented from two widely separated locations that suggest this warming was associated with a drop in oceanic pCO2 rather than an increase. Oceanic pCO2 change across this event was estimated using a model of 13C fractionation in photosynthate organic carbon versus [CO2aq], with solubility constants for CO2 and stable isotopic paleotemperature estimates. To derive a well-preserved record for surface ocean δ13C change the organic carbon bound within the calcite lattice of well-preserved planktonic foraminifera was extracted for isotopic analysis. With allowance for uncertainty in the isotopic differences between phytoplankton and foraminiferal organic matter, the initial results indicate a drop in surface ocean pCO2 at high and low latitudes from 600–700 parts per million (ppm) to ∼200 ppm. Lower pCO2 persisted for at least 10,000 years. The duration of the pCO2 excursion was long enough for the ocean and atmosphere to have reached a new steady state condition. There is no evidence of increased organic carbon burial in the deep sea during this period. Two alternative explanations are presented to account for such a rapid drop in oceanic pCO2. One involves reduced upwelling induced by diminished wind stress as atmospheric circulation weakened in response to climate warming. This would have reduced the rate of metabolic CO2 recycling into the surface ocean. It will be necessary to obtain data from regions outside potential upwelling zones in order to evaluate this. The second involves a readjustment of carbonate equilibria in the ocean to higher [CO3=] in the surface ocean, particularly at high latitudes where surface waters warmed to approximately 20°C. Such a shift in carbonate equilibria would have lowered the ocean’s capacity to take in CO2. If the initial results presented here do accurately reflect a change in the global ocean [CO2aq], the Paleocene/Eocene boundary event may provide clues about the ocean’s physical and biological response to rapid, large-scale perturbations in atmospheric pCO2 and to global warming.” Stott, L. D. (1992), Paleoceanography, 7(4), 395–404, doi:10.1029/92PA01183.

Use of carbon isotopes in paleosols as an indicator of the P(CO2) of the paleoatmosphere – Cerling (1992) “Measurements of carbon isotopic composition of coexisting paleosol organic matter and carbonate results in improved estimates of the paleo-P(CO2) content of the paleoatmosphere. Measurements from Tertiary paleosols indicate that the levels of CO2 in the early Eocene, middle and late Miocene, and Pliocene were less than 1000 ppmV. Early Cretaceous levels of P(CO2) were significantly higher, of the order of 1500 to 3000 ppmV.” Cerling, T. E. (1992), Global Biogeochem. Cycles, 6(3), 307–314, doi:10.1029/92GB01102.

Carbon dioxide in the atmosphere; evidence from Cenozoic and Mesozoic Paleosols – Cerling (1991) “A diffusion-reaction model for the isotopic composition of soil CO2 and soil carbonate is evaluated. It shows which variables are important under different conditions and shows that under certain circumstances the carbon isotopic composition of soil carbonate can be used to estimate P(CO2) of the atmosphere from late Paleozoic to the present. The isotopic composition of soil carbonate produced under uniform conditions is essentially constant below about 20 cm in most soils. Today, the isotopic composition of soil organic matter, which is mostly determined by the fraction of C4 biomass present, is the most important factor in determining the carbon isotopic composition of soil carbonate. However, prior to the advent of C4 plants making up a significant fraction of the biomass, probably in the Tertiary, the concentration of CO2 in the atmosphere can be estimated because of mixing of atmospheric CO2 with CO2 produced in the soil. The diffusion-reaction model also suggests that before the advent of higher land plants most soil carbonate should have {delta}13C values between {minus}6.5 and {minus}8.5 permil suggesting that P(CO2) was significantly higher than today, probably on the order of 1,500 to 3,000 ppmV.” Thure E. Cerling, American Journal of Science, Vol. 291, April 1991, P.377-400; doi:10.2475/ajs.291.4.377. [Full text]

Lacustrine carbonates and pedogenesis: sedimentology and origin of palustrine deposits from the Early Cretaceous Rupelo Formation, W Cameros Basin, N Spain – Platt (1989) “The Berriasian Rupelo Formation of the W Cameros Basin consists of a 2–200 m thickness of marginal and open lacustrine carbonate and associated deposits. Open lacustrine facies contain a non-marine biota with abundant charophytes (both stems and gyrogonites), ostracods, gastropods and rare vertebrates. Carbonate production was mainly biogenic. The associated marginal lacustrine (‘palustrine’) facies show strong indications of subaerial exposure and exhibit a wide variety of pedogenic fabrics. Silicified evaporites found near to the top of the sequence reflect a short hypersaline phase in the lake history. The succession was laid down in a low gradient, shallow lake complex characterized by wide fluctuations of the shoreline. Carbon and oxygen stable isotope analyses from the carbonates show non-marine values with ranges of δ13 from − 7 to − 11‰and δ18 from − 3 to − 7.5‰. Differences in the isotopic composition of open lacustrine carbonates are consistent with sedimentary evidence of variation in organic productivity within the lake. Analyses from the entire sample suite plot on a linear trend; isotopic compositions become lighter with increasing evidence of pedogenic modification. This suggests progressive vadose zone diagenesis and influence of meteoric waters rich in soil-derived CO2. The stable isotope data thus support evidence from petrography and facies relations that ‘palustrine’limestones form through pedogenic modification of lake carbonates.” Nigel H. Platt, Sedimentology, Volume 36, Issue 4, pages 665–684, August 1989.

Isotopic imprint of climate and hydrogeochemistry on terrestrial strata of the Triassic-Jurassic Hartford and Fundy rift basins – Suchecki et al. (1988) “Late Triassic to Early Jurassic terrestrial sequences in the Hartford and Fundy rift basins have distinctive carbon and oxygen isotopic compositions of calcite and dolomite. The isotopic data mostly reflect paleoclimatic fluctuations and hydrogeochemistry of the lacustrine, playa, and fluvial environments. Dolomites from laminae in three sequences of playa red mudstones and lacustrine gray to black mudstones in the Hartford basin have variable isotopic compositions (delta 13 C = -5.8 to + 1.8 per thousand PDB; delta 18 O = -7.2 to +0.7 per thousand PDB). Within any single symmetrical cycle of playa red mudstone–lacustrine gray, black, gray mudstone–playa red mudstone, there is a systematic change to relatively enriched 13 C compositions in dolomite in the grayish black and black mudstones in the center of the cycle. These carbon isotopic data suggest that the lacustrine sequences formed as the lakes changed from well mixed with anoxic bottom waters to stratified with anoxic bottom waters where 13 C-depleted carbon was concentrated in organic matter that was then buried. Calcites from lacustrine, micritic, and biomicritic limestones of the Scots Bay Formation of the Fundy basin have stable isotopic compositions (delta 13 C = -4.6 to -2.2 per thousand PDB; delta 18 O = -6.1 to -3.0 per thousand PDB) that become more enriched in 18 O and 13 C upward in shallowing depositional sequences. These isotopic data reflect initial calcite precipitation when a high inflow of fresh water produced high lake levels, followed by progressively lower inflow, resulting in lower lake stands and higher salinity due to continuing evaporative loss of surface water. The lake waters were well oxygenated at all times. In the Hartford basin, caliche calcites in fluvial mudstones and sandstones have isotopic compositions (delta 13 C = -7.3 to -3.8 per thousand PDB; delta 18 O = -8.0 to – 5.6 per thousand PDB) that reflect paleosol processes during climatic conditions that varied from warm and dry in Late Triassic time to relatively cooler and probably wetter in the Early Jurassic. Isotopic compositions of caliche calcites in redbeds in the Fundy basin indicate a parallel climate change from Late Triassic to Early Jurassic time, but also that the climate was relatively hotter and probably drier over the entire interval, as compared to the Hartford basin.” Robert K. Suchecki, John F. Hubert, and Carol C. Birney de Wet, Journal of Sedimentary Research; September 1988; v. 58; no. 5; p. 801-811; DOI: 10.1306/212F8E6D-2B24-11D7-8648000102C1865D.

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Molecular proxies for paleoclimatology – Eglinton & Eglinton (2008) “We summarize the applications of molecular proxies in paleoclimatology. Marine molecular records especially are proving to be of value but certain environmentally persistent compounds can also be measured in lake sediments, loess deposits and ice cores. The fundamentals of this approach are the molecular parameters, the compound abundances and carbon, hydrogen, nitrogen and oxygen isotopic contents which can be derived by the analysis of sediment extracts. These afford proxy measures which can be interpreted in terms of the conditions which control climate and also reflect its operation. We discuss two types of proxy; those of terrigenous and those of aquatic origin, and exemplify their application in the study of marine sediments through the medium of ten case studies based in the Atlantic, Mediterranean and Pacific Oceans, and in Antarctica. The studies are mainly for periods in the present, the Holocene and particularly the last glacial/interglacial, but they also include one study from the Cretaceous. The terrigenous proxies, which are measures of continental vegetation, are based on higher plant leaf wax compounds, i.e. long-chain (circa C30) hydrocarbons, alcohols and acids. They register the relative contributions of C3 vs. C4 type plants to the vegetation in the source areas. The two marine proxies are measures of sea surface temperatures (SST). The longer established one, (U37K′) is based on the relative abundances of C37 alkenones photosynthesized by unicellular algae, members of the Haptophyta. The newest proxy (TEX86) is based on C86 glycerol tetraethers (GDGTs) synthesized in the water column by some of the archaeal microbiota, the Crenarchaeota.” Timothy I. Eglinton and Geoffrey Eglinton, Earth and Planetary Science Letters, Volume 275, Issues 1-2, 30 October 2008, Pages 1-16, doi:10.1016/j.epsl.2008.07.012. [Full text]

Geocarb III: A Revised Model of Atmospheric CO2 over Phanerozoic Time – Berner & Kothavala (2001) “Revision of the GEOCARB model (Berner, 1991, 1994) for paleolevels of atmospheric CO2, has been made with emphasis on factors affecting CO2 uptake by continental weathering. This includes: (1) new GCM (general circulation model) results for the dependence of global mean surface temperature and runoff on CO2, for both glaciated and non-glaciated periods, coupled with new results for the temperature response to changes in solar radiation; (2) demonstration that values for the weathering-uplift factor fR(t) based on Sr isotopes as was done in GEOCARB II are in general agreement with independent values calculated from the abundance of terrigenous sediments as a measure of global physical erosion rate over Phanerozoic time; (3) more accurate estimates of the timing and the quantitative effects on Ca-Mg silicate weathering of the rise of large vascular plants on the continents during the Devonian; (4) inclusion of the effects of changes in paleogeography alone (constant CO2 and solar radiation) on global mean land surface temperature as it affects the rate of weathering; (5) consideration of the effects of volcanic weathering, both in subduction zones and on the seafloor; (6) use of new data on the 13C values for Phanerozoic limestones and organic matter; (7) consideration of the relative weather- ing enhancement by gymnosperms versus angiosperms; (8) revision of paleo land area based on more recent data and use of this data, along with GCM-based paleo-runoff results, to calculate global water discharge from the continents over time. Results show a similar overall pattern to those for GEOCARB II: very high CO2 values during the early Paleozoic, a large drop during the Devonian and Carbonifer- ous, high values during the early Mesozoic, and a gradual decrease from about 170 Ma to low values during the Cenozoic. However, the new results exhibit considerably higher CO2 values during the Mesozoic, and their downward trend with time agrees with the independent estimates of Ekart and others (1999). Sensitivity analysis shows that results for paleo-CO2 are especially sensitive to: the effects of CO2 fertilization and temperature on the acceleration of plant-mediated chemical weathering; the quantitative effects of plants on mineral dissolution rate for constant temperature and CO2; the relative roles of angiosperms and gymnosperms in accelerating rock weather- ing; and the response of paleo-temperature to the global climate model used. This emphasizes the need for further study of the role of plants in chemical weathering and the application of GCMs to study of paleo-CO2 and the long term carbon cycle.” Robert A. Berner and Zavareth Kothavala, American Journal of Science, Vol. 301, February 2001, P.182-204; doi:10.2475/ajs.301.2.182. [Full text]

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Papers on global warming and Earth’s rotation

Posted by Ari Jokimäki on May 25, 2011

This is a list of papers on global warming effects to Earth’s rotation. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (October 20, 2020): Zotov et al. (2016) and Mitrovica et al. (2015) added.

A possible interrelation between Earth rotation and climatic variability at decadal time-scale (Zotov et al. 2016) (OPEN ACCESS) “Using multichannel singular spectrum analysis (MSSA) we decomposed climatic time series into principal components, and compared them with Earth rotation parameters. The global warming trends were initially subtracted. Similar quasi 60 and 20 year periodic oscillations have been found in the global mean Earth temperature anomaly (HadCRUT4) and global mean sea level (GMSL). Similar cycles were also found in Earth rotation variation. Over the last 160 years multi-decadal change of Earth’s rotation velocity is correlated with the 60-year temperature anomaly, and Chandler wobble envelope reproduces the form of the 60-year oscillation noticed in GMSL. The quasi 20-year oscillation observed in GMSL is correlated with the Chandler wobble excitation. So, we assume that Earth’s rotation and climate indexes are connected. Despite of all the clues hinting this connection, no sound conclusion can be done as far as ocean circulation modelling is not able to correctly catch angular momentum of the oscillatory modes.” Leonid Zotov, C. Bizouard, C.K. Shum (2016). Geodesy and Geodynamics, Volume 7, Issue 3, Pages 216-222, https://doi.org/10.1016/j.geog.2016.05.005.

Reconciling past changes in Earth’s rotation with 20th century global sea-level rise: Resolving Munk’s enigma (Mitrovica et al. 2015) (OPEN ACCESS) “In 2002, Munk defined an important enigma of 20th century global mean sea-level (GMSL) rise that has yet to be resolved. First, he listed three canonical observations related to Earth’s rotation [(i) the slowing of Earth’s rotation rate over the last three millennia inferred from ancient eclipse observations, and changes in the (ii) amplitude and (iii) orientation of Earth’s rotation vector over the last century estimated from geodetic and astronomic measurements] and argued that they could all be fit by a model of ongoing glacial isostatic adjustment (GIA) associated with the last ice age. Second, he demonstrated that prevailing estimates of the 20th century GMSL rise (~1.5 to 2.0 mm/year), after correction for the maximum signal from ocean thermal expansion, implied mass flux from ice sheets and glaciers at a level that would grossly misfit the residual GIA-corrected observations of Earth’s rotation. We demonstrate that the combination of lower estimates of the 20th century GMSL rise (up to 1990) improved modeling of the GIA process and that the correction of the eclipse record for a signal due to angular momentum exchange between the fluid outer core and the mantle reconciles all three Earth rotation observations. This resolution adds confidence to recent estimates of individual contributions to 20th century sea-level change and to projections of GMSL rise to the end of the 21st century based on them.” Jerry X. Mitrovica, Carling C. Hay, Eric Morrow, Robert E. Kopp, Mathieu Dumberry, Sabine Stanley (2015). Science Advances 11 Dec 2015: Vol. 1, no. 11, e1500679. DOI: 10.1126/sciadv.1500679.

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process? – Roy & Peltier (2011) “Recent trends in the two primary anomalies in the rotational state of the planet are analyzed in detail, namely those associated with the speed and direction of polar wander and with the non-tidal acceleration of the rate of axial rotation (via the measurement of the changing oblateness of the Earth’s shape). It is demonstrated that a significant change in the secular trends in both of these independent parameters became evident subsequent to approximately 1992. It is suggested that both parameters might have come to be substantially influenced by mass loss from both the great polar ice sheets, and from the very large number of small ice-sheets and glaciers that are also being influenced by the global warming phenomenon. The modern values for the secular drifts in those parameters that we estimate are appropriate to the period during which measurements have been made by the satellites of the Gravity Recovery and Climate Experiment (GRACE). These changes in secular rates might greatly assist in understanding why the GRACE-inferred values of the time derivatives of the degree two and order one Stokes coefficients differ so significantly from those associated with Late Quaternary ice-age influence.” Roy, K., and W. R. Peltier (2011), Geophys. Res. Lett., 38, L10306, doi:10.1029/2011GL047282.

Ocean bottom pressure changes lead to a decreasing length-of-day in a warming climate – Landerer et al. (2007) “We use a coupled climate model to evaluate ocean bottom pressure changes in the IPCC-A1B climate scenario. Ocean warming in the 21st and 22nd centuries causes secular oceanic bottom pressure anomalies. The essential feature is a net mass transfer onto shallow shelf areas from the deeper ocean areas, which exhibit negative bottom pressure anomalies. We develop a simple mass redistribution model that explains this mechanism. Regionally, however, distinct patterns of bottom pressure anomalies emerge due to spatially inhomogeneous warming and ocean circulation changes. Most prominently, the Arctic Ocean shelves experience an above-average bottom pressure increase. We find a net transfer of mass from the Southern to the Northern Hemisphere, and a net movement of mass closer towards Earth’s axis of rotation. Thus, ocean warming and the ensuing mass redistribution change the length-of-day by −0.12 ms within 200 years, demonstrating that the oceans are capable of exciting nontidal length-of-day changes on decadal and longer timescales.” Landerer, F. W., J. H. Jungclaus, and J. Marotzke (2007), Geophys. Res. Lett., 34, L06307, doi:10.1029/2006GL029106.

The 60-year solar modulation of global air temperature: the Earth’s rotation and atmospheric circulation connection – Mazzarella (2007) “Spectral analysis of geomagnetic activity, global air temperature, Earth’s rotation rate and zonal circulation, when smoothed from secular trend and periods shorter than 23 years, shows a concentration of energy around the 60-year period explaining more than 80% of the entire variance. This information has enabled the set-up of a cascade physical model that integrates the Sun-atmosphere-Earth system as a single unit and ties solar corpuscular radiation to global warming through Earth’s rotation and atmospheric circulation. Our results suggest that changes in geomagnetic activity, and in the Earth’s rotation, could be used as long- and short-term indicators, respectively, of future changes in global air temperature.” A. Mazzarella, Theoretical and Applied Climatology, Volume 88, Numbers 3-4, 193-199, DOI: 10.1007/s00704-005-0219-z.

Earth rotation/polar motion excitations from atmospheric models – Salstein (2005) “We review both the characteristics of the angular momentum signals that excite Earth rotation variations as calculated from global analyses of the atmosphere, as well as the ability of the current generation of global atmospheric models to simulate such signals. We are interested in results for the planetary axial component, whose fluctuations are related to length of day, and the two equatorial components, related to polar motion. Model results are compared with the analyses of the atmosphere that are produced by weather forecast centers, both contemporaneously and retrospectively, which are also known as operational analyses and reanalyses, repectively. Results from simulations by a group of atmospheric general circulation models forced by time-variable sea surface temperatures over a one- to two-decade period enable us to assess the current state-of-the-art in simulating atmospheric excitations of Earth rotation. These models have become increasingly skillful in this regard on both seasonal and interannual timescales, with much of the latter related to the dominant El Niño-Southern Oscillation atmosphere-ocean signal. Recently, some atmospheric general circulation models have also been run to simulate much of the last century. Several realizations of such a model for a period covering the 20th century, for example, have been used to estimate excitations of the Earth rotation on a number of time scales. Information from all these simulations of the past is useful in the design of atmosphere, or atmosphere-ocean coupled, models that can serve as tools to forecast the future, including those with scenarios of projected increases in greenhouse gases; such models could produce changes in Earth rotation or polar motion parameters.” Salstein, David A., Artificial Satellites – Journal of Planetary Geodesy (ISSN 0208-841X), Vol. 40, No. 1, p. 35 – 46 (2005). In: Proceedings of the seminar “Earth rotation and satellite geodesy from astrometry to GNSS”, Warsaw, September, 18-19, 2003. Part III: Earth rotation.

Low-frequency excitation of length of day and polar motion by the atmosphere – de Viron et al. (2004) “Results of a 100-year run of the Hadley Centre general circulation model are used to compute monthly values of the three components of atmospheric torque on the Earth and of the associated atmospheric angular momentum series. All these results are compared with equivalent ones from the National Center for Environmental Prediction/National Center for Atmospheric Research reanalyses for the overlap period since 1948. We find some important differences; consequently, our results should be taken as an order of magnitude of the effect. We also compute the effect of the atmosphere on length of day (LOD) and polar motion by the use of both the torque and the angular momentum approaches. We find comparable amplitude with both torque and angular momentum for the polar motion; the axial torque, however, related to LOD, appears to be unphysical. The excitation of long-period LOD variation is in phase with the observed variation but much smaller. The low-frequency polar motion is only coherent with the observation at certain particular periods.” de Viron, O., D. Salstein, C. Bizouard, and L. Fernandez (2004), J. Geophys. Res., 109, B03408, doi:10.1029/2003JB002817.

CO2-Induced Changes in Atmospheric Angular Momentum in CMIP2 Experiments – Räisänen (2003) “The response of atmospheric angular momentum to a gradual doubling of CO2 is studied using 16 model experiments participating in the second phase of the Coupled Model Intercomparison Project (CMIP2). The relative angular momentum associated with atmospheric zonal winds increases in all but one of the models, although the magnitude of the change varies widely. About 90% of the 16-model mean increase comes from increasing westerly winds in the stratosphere and the uppermost low-latitude troposphere above 200 hPa. This increase in westerly winds reflects a steepening of the meridional temperature gradient near the tropopause and in the upper troposphere. The simulated temperature gradient at this height increases partly as an indirect consequence of the poleward decrease in the tropopause height, and partly because convection induces a maximum in warming in the tropical upper troposphere. The change in the omega angular momentum associated with the surface pressure distribution is in most models smaller than the change in the relative angular momentum, although its exact value is sensitive to the method of calculation.” Räisänen, Jouni, 2003, J. Climate, 16, 132–143. [Full text]

Unusual Behavior in Atmospheric Angular Momentum during the 1965 and 1972 El Niños – Huang et al. (2003) “The global atmospheric angular momentum (AAM) is known to increase with tropical eastern Pacific sea surface temperature (SST) anomalies during El Niño events. Using a reanalysis dataset, the ratio of the monthly AAM anomaly to El Niño SST anomaly (based on the Niño-3.4 index) is found to be approximately 1 angular momentum unit (=1025 kg m2 s−1) per degree Celsius for most post-1975 El Niños. This ratio is much smaller, however, during the 1965/66 and 1972/73 El Niños, raising the possibilities that either the early reanalysis data are in error due to sparse observations, or the atmospheric response to the two early El Niños was unusual. The possibility of a severe data problem in the reanalysis is ruled out by cross-validating the AAM time series with independent measurements of length of day. The latitudinal structures of the zonal wind anomalies in 1965/66 and 1972/73 are examined for both the reanalysis and a set of general circulation model (GCM) simulations. Multiple GCM runs with specified SST produce a more positive ensemble-mean AAM anomaly in 1965 than its counterpart in the reanalysis. The GCM-simulated ensemble-mean zonal wind anomaly resembles the canonical El Niño response with accelerations of subtropical zonal jets in both hemispheres, a pattern that is almost absent in the reanalysis. On the other hand, a large spread exists among the individual ensemble members in the 1965/66 GCM simulations. Although the majority of the individual ensemble members shows the canonical El Niño response, two outliers (out of 12 runs) exhibit very small zonal wind responses in the Northern Hemisphere similar to the reanalysis. Thus, the observed AAM anomaly during 1965/66 is interpreted as an outlier with atmospheric noise being strong enough to overwhelm the canonical El Niño response. The low AAM in the 1972/73 event is related in the reanalysis to a significantly negative zonal wind response on the equator. This signal is robustly reproduced, although with a slightly smaller amplitude, in the ensemble mean and all individual ensemble members in the GCM simulations. The small ensemble standard deviation and large ensemble-mean response on the equator indicate that the negative response is due to the lower-boundary forcing related to the SST anomaly. The fact that the AAM anomaly in 1972/73 is not well correlated with the Niño-3.4 index, then, indicates that SST anomalies outside the conventional El Niño region may be responsible for the low AAM. The uncharacteristically low values of global AAM in 1965/66 and 1972/73 contribute to a low mean for the decade before 1975, which, combined with high AAM in the post-1980 era, produces a significant upward trend in AAM in the second half of the twentieth century. If the weak AAM anomalies during the two pre-1975 El Niños are due to random noise or incidental non-El Niño influences, taking them at face value would result in an overestimate of about 15%–20% in the multidecadal trend of AAM due to boundary forcing alone. Notably, a multidecadal trend in AAM is also simulated in the ensemble mean of the multiple GCM runs, but its magnitude is smaller than the observed counterpart and more consistent with the multidecadal trend of the Niño-3.4 index. The implications of these findings for climate change detection are discussed.” Huang, Huei-Ping, Klaus M. Weickmann, Richard D. Rosen, 2003, J. Climate, 16, 2526–2539. [Full text]

Recent Earth Oblateness Variations: Unraveling Climate and Postglacial Rebound Effects – Dickey et al. (2002) “Earth’s dynamic oblateness (J 2) has been decreasing due to postglacial rebound (PGR). However, J 2 began to increase in 1997, indicating a pronounced global-scale mass redistribution within Earth’s system. We have determined that the observed increases in J 2 are caused primarily by a recent surge in subpolar glacial melting and by mass shifts in the Southern, Pacific, and Indian oceans. When these effects are removed, the residual trend in J 2 (–2.9 x 10−11 year−1) becomes consistent with previous estimates of PGR from satellite and eclipse data. The climatic significance of these rapid shifts in glacial and oceanic mass, however, remains to be investigated.” Jean O. Dickey, Steven L. Marcus, Olivier de Viron and Ichiro Fukumori, Science 6 December 2002: Vol. 298 no. 5600 pp. 1975-1977, DOI: 10.1126/science.1077777.

Effect of global warming on the length-of-day – Viron et al. (2002) “The anthropogenic increase in greenhouse gas concentrations in the Earth atmosphere will probably induce important modifications of the global circulation in the atmosphere and ocean. Due to the angular momentum conservation of the Earth-atmosphere-ocean system, variation of the length-of-day (LOD) can be expected. By using the outputs of the models participating to the Coupled Model Intercomparison Project (CMIP-2), we reach the following conclusions: (1) the models globally agree to an increase of the LOD of the order of 1 μs/year, (2) the effect is mostly associated with an increase of the mean zonal wind, of which about one third is compensated by a change in mass repartition.” de Viron, O., V. Dehant, H. Goosse, and M. Crucifix (2002), Geophys. Res. Lett., 29(7), 1146, doi:10.1029/2001GL013672.

Ocean angular momentum signals in a climate model and implications for Earth rotation – Ponte et al. (2002) “Estimates of ocean angular momentum (OAM) provide an integrated measure of variability in ocean circulation and mass fields and can be directly related to observed changes in Earth rotation. We use output from a climate model to calculate 240 years of 3-monthly OAM values (two equatorial terms L1 and L2, related to polar motion or wobble, and axial term L3, related to length of day variations) representing the period 1860-2100. Control and forced runs permit the study of the effects of natural and anthropogenically forced climate variability on OAM. All OAM components exhibit a clear annual cycle, with large decadal modulations in amplitude, and also longer period fluctuations, all associated with natural climate variability in the model. Anthropogenically induced signals, inferred from the differences between forced and control runs, include an upward trend in L3, related to inhomogeneous ocean warming and increases in the transport of the Antarctic Circumpolar Current, and a significantly weaker seasonal cycle in L2 in the second half of the record, related primarily to changes in seasonal bottom pressure variability in the Southern Ocean and North Pacific. Variability in mass fields is in general more important to OAM signals than changes in circulation at the seasonal and longer periods analyzed. Relation of OAM signals to changes in surface atmospheric forcing are discussed. The important role of the oceans as an excitation source for the annual, Chandler and Markowitz wobbles, is confirmed. Natural climate variability in OAM and related excitation is likely to measurably affect the Earth rotation, but anthropogenically induced effects are comparatively weak.” R. Ponte, J. Rajamony and J. Gregory, Climate Dynamics, Volume 19, Number 2, 181-190, DOI: 10.1007/s00382-001-0216-6.

Trend in Atmospheric Angular Momentum in a Transient Climate Change Simulation with Greenhouse Gas and Aerosol Forcing – Huang et al. (2001) “The authors investigate the change of atmospheric angular momentum (AAM) in long, transient, coupled atmosphere–ocean model simulations with increasing atmospheric greenhouse gas concentration and sulfate aerosol loading. A significant increase of global AAM, on the order of 4 × 1025 kg m2 s-1 for 3 × CO2–1 × CO2, was simulated by the Canadian Centre for Climate Modelling and Analysis (CCCma) coupled model. The increase was mainly contributed by the relative component of total AAM in the form of an acceleration of zonal mean zonal wind in the tropical–subtropical upper troposphere. Thus, under strong global warming, a superrotational state emerged in the tropical upper troposphere. The trend in zonal mean zonal wind in the meridional plane was characterized by 1) a tropical–subtropical pattern with two maxima near 30° in the upper troposphere, and 2) a tripole pattern in the Southern Hemisphere extending through the entire troposphere and having a positive maximum at 60°S. The implication of the projected increase of global AAM for future changes of the length of day is discussed. The CCCma coupled global warming simulation, like many previous studies, shows a significant increase of tropical SST and includes a zonally asymmetric component that resembles El Niño SST anomalies. In the CCCma transient simulations, even though the tropical SST and global AAM both increased nonlinearly with time, the ratio of their time increments ΔAAM/ΔSST remained approximately constant at about 0.9 × 1025 kg m2 s-1 (°C)-1. This number is close to its counterpart for the observed global AAM response to El Niño. It is suggested that this ratio may be useful as an index for intercomparisons of different coupled model simulations.” Huang, Huei-Ping, Klaus M. Weickmann, C. Juno Hsu, 2001, J. Climate, 14, 1525–1534, doi: 10.1175/1520-0442(2001)0142.0.CO;2. [Full text]

The influence of global warming in Earth rotation speed – del Rio (1999) “The tendency of the atmospheric angular momentum (AAM) is investigated using a 49-year set of monthly AAM data for the period January 1949-December 1997. This data set is constructed with zonal wind values from the reanalyses of NCEP/NCAR, used in conjunction with a variety of operationally produced AAM time series with different independent sources and lengths over 1976-1997. In all the analyzed AAM series the linear trend is found to be positive. Since the angular momentum of the atmosphere-earth system is conserved this corresponds to a net loss of angular momentum by the solid earth, therefore decreasing the Earth rotation speed and increasing the length of day (LOD). The AAM rise is significant to the budget of angular momentum of the global atmosphere-earth system; its value in milliseconds/century (ms/cy) is +0.56 ms/cy, corresponding to one-third of the estimated increase in LOD (+1.7 ms/cy). The major contribution to this secular trend in AAM comes from the equatorial Tropopause. This is consistent with results from a previous study using a simplified aqua-planet model to investigate the AAM variations due to near equatorial warming conditions. During the same time interval, 1949-1997, the global marine + land-surface temperature increases by about 0.79 °C/cy, showing a linear correspondence between surface temperature increase and global AAM of about 0.07 ms per 0.1 °C. These results imply that atmospheric angular momentum may be used as an independent index of the global atmosphere’s dynamical response to the greenhouse forcing, and as such, the length of day may be used as an indirect indicator of global warming.” Abarca del Rio, R., Ann. Geophys., 17, 806-811, doi:10.1007/s00585-999-0806-x, 1999. [Full text]

Response of Zonal Winds and Atmospheric Angular Momentum to a Doubling Of CO2 – Rosen & Gutowski (1992) “The possible impact of doubling CO2 on the zonal-mean zonal winds and the angular momentum of the atmosphere is examined using general circulation model output archived by the Goddard Institute for Space Studies, the National Center for Atmospheric Research, and the Geophysical Fluid Dynamics Laboratory. Whereas the emphasis in most previous studies with these models has been placed on the temperature and precipitation changes expected from a doubled-CO2 scenario, the intent here is to investigate some of the dynamical consequences predicted by them models, especially within the tropics where the zonal-wind and temperature changes are less tightly coupled than elsewhere. Comparisons among the three models of the difference in zonal-mean zonal winds between 2×CO2 and 1×CO2 simulations indicate a common tendency when CO2 is doubled for winds to become more easterly in much of the tropics during June-July-August. Less of a consensus for the tropics emerges for December-January-February, perhaps as a result of differences among the models’ basic climatologies for the zonal-wind field. In general, however, changes predicted for the zonal winds in the tropics and elsewhere are comparable to the interannual variability currently observed, suggesting that these changes ought to become detectable eventually. Largely because of the tropical wind changes, decreases in the troposphere’s relative angular momentum accompany a doubling of CO2 in all the model runs. The amplitude of the decrease is typically a considerable fraction of a model’s seasonal cycle and, in some cases, is large enough that a measurable change in the length of day could result. Although the possibility of an anthropogenic effect on earth’s rotation is noteworthy, such a prediction must be regarded as tentative in light of the shortcomings found in the models’ zonal-wind climatologies and the differences in their zonal-mean responses.” Rosen, Richard D., William J. Gutowski, 1992, J. Climate, 5, 1391–1404. doi: 10.1175/1520-0442(1992)0052.0.CO;2. [Full text]

Global Sea Level and Earth Rotation – Peltier (1988) “Recent analyses of long time scale secular variations of sea level, based on tide gauge observations, have established that sea level is apparently rising at a globally averaged rate somewhat in excess of 1 millimeter per year. It has been suggested that the nonsteric component of this secular rate might be explicable in terms of ongoing mass loss from the small ice sheets and glaciers of the world. Satellite laser ranging and very long baseline interferometry data may be used to deliver strong constraints on this important scenario because of the information that these systems provide on variations of the length of day and of the position of the rotation pole with respect to the earth’s surface geography. These data demonstrate that the hypothesis of mass loss is plausible if the Barents Sea was covered by a substantial ice sheet at the last maximum of the current ice age 18,000 years ago.” W. R. Peltier, Science 13 May 1988: Vol. 240 no. 4854 pp. 895-901, DOI: 10.1126/science.240.4854.895.

An El Niño Signal in Atmospheric Angular Momentum and Earth Rotation – Rosen et al. (1984) “Anomalously high values of atmospheric angular momentum and length of day were observed in late January 1983. This signal in the time series of these two coupled quantities appears to have been a consequence of the equatorial Pacific Ocean warming event of 1982-1983.” Richard D. Rosen, David A. Salstein, T. Marshall Eubanks, Jean O. Dickey and J. Alan Steppe, Science 27 July 1984: Vol. 225 no. 4660 pp. 411-414, DOI: 10.1126/science.225.4660.411.

Atmospheric angular momentum fluctuations and changes in the length of the day – Hide et al. (1980) “Fluctuations in the angular momentum of the Earth’s atmosphere correspond fairly well with equal and opposite fluctuations in the angular momentum of the Earth’s ‘solid’ mantle. A decrease of 20% of the relative angular momentum of the atmosphere during the second half of May 1979 was accompanied by a speeding up of the rotation of the mantle causing the length of the day (l.o.d.) to decrease by 0.6 10-3 s. Although motions in the Earth’s liquid core produce the more pronounced ‘decade’ variations in the l.o.d. there is no evidence that core motions produce l.o.d. variations on much shorter time-scales.” R. Hide, N. T. Birch, L. V. Morrison, D. J. Shea & A. A. White, Nature 286, 114 – 117 (10 July 1980); doi:10.1038/286114a0.

Long Term Variations in the Length of Day and Climatic Change – Lambeck & Cazenave (1976) “The long-period (greater than about 10 yr) variations in the length-of-day (LOD) observed since 1820 show a marked similarity with variations observed in various climatic indices; periods of acceleration of the Earth corresponding to years of increasing intensity of the zonal circulation and to global-surface warming: periods of deceleration corresponding to years of decreasing zonal-circulation intensity and to a global decrease in surface temperatures. The long-period atmospheric excitation functions for near-surface geostrophic winds, for changes in the atmospheric mass distribution and for eustatic variations in sea level have been evaluated and correlate well with the observed changes in the LOD; although their total effect represents only about 10 per cent of the required excitation. The computed excitation lags the LOD variations by about 10–15 yr. Upper atmospheric winds or other meteorological related factors appear to be quite inadequate to provide the additional driving force that is required if the LOD changes are of meteorological origin. Instead, it appears that the LOD fluctuations and the climatic variations on a time scale of 20–30 yr may have a common origin as has been suggested by Anderson. That is, the results suggest that indirect solid Earth effects on climate may be important.” Kurt Lambeck, Amy Cazenave, Geophysical Journal of the Royal Astronomical Society, Volume 46, Issue 3, pages 555–573, September 1976. [Full text]

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Papers on atmospheric carbon monoxide

Posted by Ari Jokimäki on March 18, 2011

This is a list of papers on atmospheric carbon monoxide with an emphasis on the observations and on the relation to fossil fuel sources. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (May 16, 2012): Wang et al. (2012) added.

The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950: implications for the CO budget – Wang et al. (2012) “We present a 60-year record of the stable isotopes of atmospheric carbon monoxide (CO) from firn air samples collected under the framework of the North Greenland Eemian Ice Drilling (NEEM) project. CO concentration, δ13C, and δ18O of CO were measured by gas chromatography/isotope ratio mass spectrometry (gc-IRMS) from trapped gases in the firn. We applied LGGE-GIPSA firn air models (Witrant et al., 2011) to correlate gas age with firn air depth and then reconstructed the trend of atmospheric CO and its stable isotopic composition at high northern latitudes since 1950. The most probable firn air model scenarios show that δ13C decreased slightly from −25.8‰ in 1950 to −26.4‰ in 2000, then decreased more significantly to −27.2‰ in 2008. δ18O decreased more regularly from 9.8‰ in 1950 to 7.1‰ in 2008. Those same scenarios show CO concentration increased gradually from 1950 and peaked in the late 1970s, followed by a gradual decrease to present day values (Petrenko et al., 2012). Results from an isotope mass balance model indicate that a slight increase, followed by a large reduction, in CO derived from fossil fuel combustion has occurred since 1950. The reduction of CO emission from fossil fuel combustion after the mid-1970s is the most plausible mechanism for the drop of CO concentration during this time. Fossil fuel CO emissions decreased as a result of the implementation of catalytic converters and the relative growth of diesel engines, in spite of the global vehicle fleet size having grown several fold over the same time period.” Wang, Z., Chappellaz, J., Martinerie, P., Park, K., Petrenko, V., Witrant, E., Emmons, L. K., Blunier, T., Brenninkmeijer, C. A. M., and Mak, J. E.: The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950: implications for the CO budget, Atmos. Chem. Phys., 12, 4365-4377, doi:10.5194/acp-12-4365-2012, 2012. [full text]

Global estimates of CO sources with high resolution by adjoint inversion of multiple satellite datasets (MOPITT, AIRS, SCIAMACHY, TES) – Kopacz et al. (2010) “We combine CO column measurements from the MOPITT, AIRS, SCIAMACHY, and TES satellite instruments in a full-year (May 2004–April 2005) global inversion of CO sources at 4°×5° spatial resolution and monthly temporal resolution. The inversion uses the GEOS-Chem chemical transport model (CTM) and its adjoint applied to MOPITT, AIRS, and SCIAMACHY. Observations from TES, surface sites (NOAA/GMD), and aircraft (MOZAIC) are used for evaluation of the a posteriori solution. Using GEOS-Chem as a common intercomparison platform shows global consistency between the different satellite datasets and with the in situ data. Differences can be largely explained by different averaging kernels and a priori information. The global CO emission from combustion as constrained in the inversion is 1350 Tg a−1. This is much higher than current bottom-up emission inventories. A large fraction of the correction results from a seasonal underestimate of CO sources at northern mid-latitudes in winter and suggests a larger-than-expected CO source from vehicle cold starts and residential heating. Implementing this seasonal variation of emissions solves the long-standing problem of models underestimating CO in the northern extratropics in winter-spring. A posteriori emissions also indicate a general underestimation of biomass burning in the GFED2 inventory. However, the tropical biomass burning constraints are not quantitatively consistent across the different datasets.” Kopacz, M., Jacob, D. J., Fisher, J. A., Logan, J. A., Zhang, L., Megretskaia, I. A., Yantosca, R. M., Singh, K., Henze, D. K., Burrows, J. P., Buchwitz, M., Khlystova, I., McMillan, W. W., Gille, J. C., Edwards, D. P., Eldering, A., Thouret, V., and Nedelec, P., Atmos. Chem. Phys., 10, 855-876, doi:10.5194/acp-10-855-2010, 2010. [full text]

Comparison of adjoint and analytical Bayesian inversion methods for constraining Asian sources of carbon monoxide using satellite (MOPITT) measurements of CO columns – Kopacz et al. (2009) “We apply the adjoint of an atmospheric chemical transport model (GEOS-Chem CTM) to constrain Asian sources of carbon monoxide (CO) with 2° × 2.5° spatial resolution using Measurement of Pollution in the Troposphere (MOPITT) satellite observations of CO columns in February–April 2001. Results are compared to the more common analytical method for solving the same Bayesian inverse problem and applied to the same data set. The analytical method is more exact but because of computational limitations it can only constrain emissions over coarse regions. We find that the correction factors to the a priori CO emission inventory from the adjoint inversion are generally consistent with those of the analytical inversion when averaged over the large regions of the latter. The adjoint solution reveals fine-scale variability (cities, political boundaries) that the analytical inversion cannot resolve, for example, in the Indian subcontinent or between Korea and Japan, and some of that variability is of opposite sign which points to large aggregation errors in the analytical solution. Upward correction factors to Chinese emissions from the prior inventory are largest in central and eastern China, consistent with a recent bottom-up revision of that inventory, although the revised inventory also sees the need for upward corrections in southern China where the adjoint and analytical inversions call for downward correction. Correction factors for biomass burning emissions derived from the adjoint and analytical inversions are consistent with a recent bottom-up inventory on the basis of MODIS satellite fire data.” Kopacz, M., D. J. Jacob, D. K. Henze, C. L. Heald, D. G. Streets, and Q. Zhang (2009), J. Geophys. Res., 114, D04305, doi:10.1029/2007JD009264. [full text]

Model analysis of the factors regulating the trends and variability of carbon monoxide between 1988 and 1997 – Duncan & Logan (2008) “We used a 3-D model of chemistry and transport to investigate trends and variability in tropospheric carbon monoxide (CO) for 1988–1997 caused by changes in the overhead ozone column, fossil fuel emissions, biomass burning emissions, methane, and transport. We found that the decreasing CO burden in the northern extra-tropics (−0.85%/y) was more heavily influenced by the decrease in European emissions during our study period than by the similar increase in Asian emissions, as transport pathways from Europe favored accumulation at higher latitudes in winter and spring. However, the opposite trends in the CO burdens from these two source regions counterbalanced at lower latitudes. Elsewhere, the factors influencing CO often compete, diminishing their cumulative impact, and trends in model CO were small or insignificant for our study period, except in the tropics in boreal fall (1.1%/y), a result of emissions from major fires in Indonesia late in 1997. There was a decrease in the ozone column during the study period as a result of the phase of the solar cycle and the eruption of Pinatubo in 1991. This decrease contributed negatively to the trend in model CO by increasing the hydroxyl radical (OH). The impact of this negative contribution was diminished by a positive contribution of similar magnitude from increasing methane. However, the trends in these two factors did not cancel for tropospheric OH, which responded primarily to changes in the ozone column.” Duncan, B. N. and Logan, J. A., Atmos. Chem. Phys., 8, 7389-7403, doi:10.5194/acp-8-7389-2008, 2008. [full text]

Using CO2:CO correlations to improve inverse analyses of carbon fluxes – Palmer et al. (2006) “Observed correlations between atmospheric concentrations of CO2 and CO represent potentially powerful information for improving CO2 surface flux estimates through coupled CO2-CO inverse analyses. We explore the value of these correlations in improving estimates of regional CO2 fluxes in east Asia by using aircraft observations of CO2 and CO from the TRACE-P campaign over the NW Pacific in March 2001. Our inverse model uses regional CO2 and CO surface fluxes as the state vector, separating biospheric and combustion contributions to CO2. CO2-CO error correlation coefficients are included in the inversion as off-diagonal entries in the a priori and observation error covariance matrices. We derive error correlations in a priori combustion source estimates of CO2 and CO by propagating error estimates of fuel consumption rates and emission factors. However, we find that these correlations are weak because CO source uncertainties are mostly determined by emission factors. Observed correlations between atmospheric CO2 and CO concentrations imply corresponding error correlations in the chemical transport model used as the forward model for the inversion. These error correlations in excess of 0.7, as derived from the TRACE-P data, enable a coupled CO2-CO inversion to achieve significant improvement over a CO2-only inversion for quantifying regional fluxes of CO2.” Palmer, P. I., P. Suntharalingam, D. B. A. Jones, D. J. Jacob, D. G. Streets, Q. Fu, S. A. Vay, and G. W. Sachse (2006), J. Geophys. Res., 111, D12318, doi:10.1029/2005JD006697. [full text]

Adjoint inverse modeling of CO emissions over Eastern Asia using four-dimensional variational data assimilation – Yumimoto & Uno (2006) “We developed a four-dimensional variational (4DVAR) data assimilation system for a regional chemical transport model (CTM). In this study, we applied it to inverse modeling of CO emissions in the eastern Asia during April 2001 and demonstrated the feasibility of our assimilation system. Three ground-based observations were used for data assimilation. Assimilated results showed better agreement with observations; they reduced the RMS difference by 16–27%. Observations obtained on board the R/V Ronald H. Brown were used for independent validation of the assimilated results. The CO emissions over industrialized east central China between Shanghai and Beijing were increased markedly by the assimilation. The results show that the annual anthropogenic (fossil and biofuel combustion) CO emissions over China are 147 Tg. Sensitivity analyses using the adjoint model indicate that the high CO concentration measured on 17 April at Rishiri, Japan (which the assimilation was unable to reproduce) originated in Russia or had traveled from outside the Asian region (e.g. Europe).” Keiya Yumimoto and Itsushi Uno, Atmospheric Environment, Volume 40, Issue 35, November 2006, Pages 6836-6845, doi:10.1016/j.atmosenv.2006.05.042.

Improved quantification of Chinese carbon fluxes using CO2/CO correlations in Asian outflow – Suntharalingam et al. (2004) “We use observed CO2:CO correlations in Asian outflow from the TRACE-P aircraft campaign (February–April 2001), together with a three-dimensional global chemical transport model (GEOS-CHEM), to constrain specific components of the east Asian CO2 budget including, in particular, Chinese emissions. The CO2/CO emission ratio varies with the source of CO2 (different combustion types versus the terrestrial biosphere) and provides a characteristic signature of source regions and source type. Observed CO2/CO correlation slopes in east Asian boundary layer outflow display distinct regional signatures ranging from 10–20 mol/mol (outflow from northeast China) to 80 mol/mol (over Japan). Model simulations using best a priori estimates of regional CO2 and CO sources from Streets et al. [2003] (anthropogenic), the CASA model (biospheric), and Duncan et al. [2003] (biomass burning) overestimate CO2 concentrations and CO2/CO slopes in the boundary layer outflow. Constraints from the CO2/CO slopes indicate that this must arise from an overestimate of the modeled regional net biospheric CO2 flux. Our corrected best estimate of the net biospheric source of CO2 from China for March–April 2001 is 3200 Gg C/d, which represents a 45% reduction of the net flux from the CASA model. Previous analyses of the TRACE-P data had found that anthropogenic Chinese CO emissions must be ∼50% higher than in Streets et al.’s [2003] inventory. We find that such an adjustment improves the simulation of the CO2/CO slopes and that it likely represents both an underreporting of sector activity (domestic and industrial combustion) and an underestimate of CO emission factors. Increases in sector activity would imply increases in Chinese anthropogenic CO2 emissions and would also imply a further reduction of the Chinese biospheric CO2 source to reconcile simulated and observed CO2 concentrations.” Suntharalingam, P., D. J. Jacob, P. I. Palmer, J. A. Logan, R. M. Yantosca, Y. Xiao, M. J. Evans, D. G. Streets, S. L. Vay, and G. W. Sachse (2004), J. Geophys. Res., 109, D18S18, doi:10.1029/2003JD004362. [full text]

Evaluation of pollutant outflow and CO sources during TRACE-P using model-calculated, aircraft-based, and Measurements of Pollution in the Troposphere (MOPITT)-derived CO concentrations – Allen et al. (2004) “Outflow of CO from Asia during March 2001 is evaluated using data from the Transport and Chemical Evolution over the Pacific (TRACE-P) mission and the Measurements of Pollution in the Troposphere (MOPITT) instrument in conjunction with model-calculated CO from the University of Maryland chemistry and transport model (UMD CTM). Comparison of model-calculated CO with aircraft measurements indicates that temporal and spatial variations in CO are well captured by the model (mean correlation coefficient of 0.78); however, model-calculated mixing ratios are lower than observed especially for pressures >850 hPa where negative biases of ∼60 ppbv were seen. Regression analysis is used to optimize the magnitudes of the bottom-up TRACE-P Asian fossil fuel (FF), biofuel (BF), and biomass burning (BB) CO emission inventories. Resulting Asian scaling factors are 1.59 ± 0.34 for FF + BF emissions and 0.47 ± 0.46 for BB emissions. Resulting FF + BF emissions are 27.7 ± 6.1 Tg for March 2001 (301 ± 67 Tg for an entire year). Resulting BB emissions for March 2001 are 8.5 ± 8.3 Tg. These results are consistent with recent inverse modeling studies. Scaling factors are lowest (highest) for experiments that assume a high (low) CO yield for the oxidation of anthropogenic and natural hydrocarbons and for experiments that use (do not use) an aerosol-modified OH distribution. Comparison of model-calculated CO with MOPITT measurements supports the results from our regression analysis. Without exception, mean March 2001 model-calculated CO profiles in the TRACE-P region from a simulation with adjusted CO sources are within a standard deviation of mean March 2001 MOPITT-sampled profiles.” Allen, D., K. Pickering, and M. Fox-Rabinovitz (2004), J. Geophys. Res., 109, D15S03, doi:10.1029/2003JD004250.

Monthly CO surface sources inventory based on the 2000–2001 MOPITT satellite data – Pétron et al. (2004) “This paper presents results of the inverse modeling of carbon monoxide surface sources on a monthly and regional basis using the MOPITT (Measurement Of the Pollution In The Troposphere) CO retrievals. The targeted time period is from April 2000 to March 2001. A sequential and time-dependent inversion scheme is implemented to correct an a priori set of monthly mean CO sources. The a posteriori estimates for the total anthropogenic (fossil fuel + biofuel + biomass burning) surface sources of CO in TgCO/yr are 509 in Asia, 267 in Africa, 140 in North America, 90 in Europe and 84 in Central and South America. Inverting on a monthly scale allows one to assess a corrected seasonality specific to each source type and each region. Forward CTM simulations with the a posteriori emissions show a substantial improvement of the agreement between modeled CO and independent in situ observations.” Pétron, G., C. Granier, B. Khattatov, V. Yudin, J.-F. Lamarque, L. Emmons, J. Gille, and D. P. Edwards (2004), Geophys. Res. Lett., 31, L21107, doi:10.1029/2004GL020560. [full text]

Comparative inverse analysis of satellite (MOPITT) and aircraft (TRACE-P) observations to estimate Asian sources of carbon monoxide – Heald et al. (2004) “We use an inverse model analysis to compare the top-down constraints on Asian sources of carbon monoxide (CO) in spring 2001 from (1) daily MOPITT satellite observations of CO columns over Asia and the neighboring oceans and (2) aircraft observations of CO concentrations in Asian outflow from the TRACE-P aircraft mission over the northwest Pacific. The inversion uses the maximum a posteriori method (MAP) and the GEOS-CHEM chemical transport model (CTM) as the forward model. Detailed error characterization is presented, including spatial correlation of the model transport error. Nighttime MOPITT observations appear to be biased and are excluded from the inverse analysis. We find that MOPITT and TRACE-P observations are independently consistent in the constraints that they provide on Asian CO sources, with the exception of southeast Asia for which the MOPITT observations support a more modest decrease in emissions than suggested by the aircraft observations. Our analysis indicates that the observations do not allow us to differentiate source types (i.e., anthropogenic versus biomass burning) within a region. MOPITT provides ten pieces of information to constrain the geographical distribution of CO sources, while TRACE-P provides only four. The greater information from MOPITT reflects its ability to observe all outflow and source regions. We conducted a number of sensitivity studies for the inverse model analysis using the MOPITT data. Temporal averaging of the MOPITT data (weekly and beyond) degrades the ability to constrain regional sources. Merging source regions beyond what is appropriate after careful selection of the state vector leads to significant aggregation errors. Calculations for an ensemble of realistic assumptions lead to a range of inverse model solutions that has greater uncertainty than the a posteriori errors for the MAP solution. Our best estimate of total Asian CO sources is 361 Tg yr−1, over half of which is attributed to east Asia.” Heald, C. L., D. J. Jacob, D. B. A. Jones, P. I. Palmer, J. A. Logan, D. G. Streets, G. W. Sachse, J. C. Gille, R. N. Hoffman, and T. Nehrkorn (2004), J. Geophys. Res., 109, D23306, doi:10.1029/2004JD005185. [full text]

Inverting for emissions of carbon monoxide from Asia using aircraft observations over the western Pacific – Palmer et al. (2003) “We use aircraft observations of continental outflow over the western Pacific from the Transport and Chemical Evolution over the Pacific (TRACE-P) mission (March–April 2001), in combination with an optimal estimation inverse model, to improve emission estimates of carbon monoxide (CO) from Asia. A priori emissions and their errors are from a customized bottom-up Asian emission inventory for the TRACE-P period. The global three-dimensional GEOS-CHEM chemical transport model (CTM) is used as the forward model. The CTM transport error (20–30% of the CO concentration) is quantified from statistics of the difference between the aircraft observations of CO and the forward model results with a priori emissions, after removing the mean bias which is attributed to errors in the a priori emissions. Additional contributions to the error budget in the inverse analysis include the representation error (typically 5% of the CO concentration) and the measurement accuracy (≃2% of the CO concentration). We find that the inverse model can usefully constrain five sources: Chinese fuel consumption, Chinese biomass burning, total emissions from Korea and Japan, total emissions from Southeast Asia, and the ensemble of all other sources. The inversion indicates a 54% increase in anthropogenic emissions from China (to 168 Tg CO yr−1) relative to the a priori; this value is still much lower than had been derived in previous inversions using the CMDL network of surface observations. A posteriori emissions of biomass burning in Southeast Asia and China are much lower than a priori estimates.” Palmer, P. I., D. J. Jacob, D. B. A. Jones, C. L. Heald, R. M. Yantosca, J. A. Logan, G. W. Sachse, and D. G. Streets (2003), J. Geophys. Res., 108(D21), 8828, doi:10.1029/2003JD003397. [full text]

Reanalysis of tropospheric CO trends: Effects of the 1997–1998 wildfires – Novelli et al. (2003) “For the past decade NOAA/CMDL has measured tropospheric carbon monoxide from a global network of sampling sites. The resulting data set provides an internally consistent picture of CO in the lower troposphere that is used to study its distribution, trends and budget. All measurements were referenced to the so-called CMDL Reference Scale (WMO 88), which was based on two sets of primary standards produced at CMDL during the late 1980s and early 1990s. A long-term downward trend in tropospheric CO during the 1990s, overlaid with shorter periods of increase and decrease, was indicated from the air measurements. Primary standards prepared in 1999 and 2000 suggested that the scale had drifted upward over time, and that mixing ratios determined in field samples were underestimated. We have applied a time dependent correction to our CO measurements based upon four sets of primary standards. In this paper, we describe the revision of the CO scale and our atmospheric measurements. A reanalysis of tropospheric trends through 2001 was based on the revised global data set. The results support previous reports of a decline in tropospheric CO. This decrease is now found largely confined to the Northern Hemisphere, where dramatic reductions in fossil fuel emissions have reportedly occurred. In contrast, no significant trend is determined in the Southern Hemisphere between 1991 and 2001. Globally averaged CO exhibits large interannual variability, primarily reflecting year to year changes in emissions from biomass burning. Dramatic enhancements of tropospheric CO in 1997 and 1998 resulted from exceptionally widespread wildfires which provided a strong pulse of CO to the atmosphere. In years of extensive boreal biomass burning, fire emissions can perturb CO levels over regional and global scales, disturbing oxidation/reduction chemistry in the troposphere.” Novelli, P. C., K. A. Masarie, P. M. Lang, B. D. Hall, R. C. Myers, and J. W. Elkins (2003), J. Geophys. Res., 108(D15), 4464, doi:10.1029/2002JD003031. [full text]

Global distribution of carbon monoxide – Holloway et al. (2000) “This study explores the evolution and distribution of carbon monoxide (CO) using the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory three-dimensional global chemical transport model (GFDL GCTM). The work aims to gain an improved understanding of the global carbon monoxide budget, specifically focusing on the contribution of each of the four source terms to the seasonal variability of CO. The sum of all CO sources in the model is 2.5 Pg CO/yr (1 Pg = 103 Tg), including fossil fuel use (300 Tg CO/yr), biomass burning (748 Tg CO/yr), oxidation of biogenic hydrocarbons (683 Tg CO/yr), and methane oxidation (760 Tg CO/yr). The main sink for CO is destruction by the hydroxyl radical, and we assume a hydroxyl distribution based on three-dimensional monthly varying fields given by Spivakovsky et al. [1990], but we increase this field by 15% uniformly to agree with a methyl chloroform lifetime of 4.8 years [Prinn et al, 1995]. Our simulation produces a carbon monoxide field that agrees well with available measurements from the NOAA/Climate Monitoring and Diagnostics Laboratory global cooperative flask sampling network and from the Jungfraujoch observing station of the Swiss Federal Laboratories for Materials Testing and Research (EMPA) (93% of seasonal-average data points agree within ±25%) and flight data from measurement campaigns of the NASA Global Tropospheric Experiment (79% of regional-average data points agree within ±25%). For all 34 ground-based measurement sites we have calculated the percentage contribution of each CO source term to the total model-simulated distribution and examined how these contributions vary seasonally due to transport, changes in OH concentration, and seasonality of emission sources. CO from all four sources contributes to the total magnitude of CO in all regions. Seasonality, however, is usually governed by the transport and destruction by OH of CO emitted by fossil fuel and/or biomass burning. The sensitivity to the hydroxyl field varies spatially, with a 30% increase in OH yielding decreases in CO ranging from 4–23%, with lower sensitivities near emission regions where advection acts as a strong local sink. The lifetime of CO varies from 10 days over summer continental regions to well over a year at the winter poles, where we define lifetime as the turnover time in the troposphere due to reaction with OH.” Holloway, T., H. Levy II, and P. Kasibhatla (2000), J. Geophys. Res., 105(D10), 12,123–12,147, doi:10.1029/1999JD901173.

Carbon monoxide in the U.S. mid‐Atlantic troposphere: Evidence for a decreasing trend – Hallock-Waters et al. (1999) “Nearly continuous measurements of carbon monoxide (CO) were made at Shenandoah National Park‐Big Meadows in rural Virginia, a site considered representative of regional air quality, from December 1994 to November 1997. Similar observations were also made at this location from October 1988 to October 1989. These observations combine to indicate a decreasing trend in CO concentration over the U.S. mid‐Atlantic region of about 5.0 ppbv yr−1, with greater than 95% confidence that the slope is significantly different from zero. The decrease suggests U.S. reductions in anthropogenic CO emissions have been effective in reducing pollutant levels. The observed trend is consistent with the U.S. EPA reported trend in emissions and the decrease in Northern Hemisphere tropospheric background CO mixing ratios observed by other researchers.” Hallock‐Waters, K. A., B. G. Doddridge, R. R. Dickerson, S. Spitzer, and J. D. Ray (1999), Geophys. Res. Lett., 26(18), 2861–2864, doi:10.1029/1999GL900609. [full text]

Distributions and recent changes of carbon monoxide in the lower troposphere – Novelli et al. (1998) “Since 1988, the distribution of carbon monoxide (CO) in the lower troposphere has been determined using a globally distributed air sampling network. Site locations range from 82°N to 90°S, with wide longitudinal coverage, and represent the marine boundary layer, regionally polluted atmospheres, and the free troposphere. These measurements present a unique, intercalibrated, and internally consistent data set that are used to better define the global temporal and spatial distribution of CO. In this paper, times series from 49 sites are discussed. With an average lifetime of ∼2 months, CO showed significant concentration gradients. In the marine boundary layer, mixing ratios were greatest in the northern winter (200–220 ppb) and lowest in the southern summer (35–45 ppb). The interhemispheric gradient showed strong seasonality with a maximum difference between the high latitudes of the northern and southern hemispheres (160–180 ppb) in February and March and a minimum in July and August (10–20 ppb). Higher CO was found in regions near human development relative to those over more remote areas. The distributions provide additional evidence of the widespread pollution of the lower atmosphere. Remote areas in the high northern hemisphere are polluted by anthropogenic activities in the middle latitudes, and those in the southern hemisphere are heavily influenced by the burning of biomass in the tropics. While tropospheric concentrations of CO exhibit periods of increase and decrease, the globally averaged CO mixing ratio over the period from 1990 through 1995 decreased at a rate of approximately 2 ppb yr−1.” Novelli, P. C., K. A. Masarie, and P. M. Lang (1998), J. Geophys. Res., 103(D15), 19,015–19,033, doi:10.1029/98JD01366. [full text]

An internally consistent set of globally distributed atmospheric carbon monoxide mixing ratios developed using results from an intercomparison of measurements – Novelli et al. (1998) “The Measurement of Air Pollution from Satellite (MAPS) instrument measures carbon monoxide (CO) in the middle troposphere from a space platform. In anticipation of the deployment of MAPS aboard the space shuttle Endeavor for two 10-day missions in 1994, plans were made to prepare a set of correlative measurements which would be used as part of the mission validation program. Eleven laboratories participated in the correlative measurement program by providing NASA with the results of their CO field programs during April and October 1994. Measurements of CO in the boundary layer, while not used in the MAPS validation, provide a picture of CO in the lower troposphere. Because measurements of CO made by different laboratories have been known to differ significantly, all correlative team members participated in an intercomparison of their measurements to define potential differences in techniques and calibration scales. While good agreement was found between some laboratories, there were differences between others. The use of similar analytical techniques and calibration scales did not always provide similar results. The results of the intercomparisons were used to normalize all ground-based measurements to the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory CO reference scale. These data provide an internally consistent picture of CO in thelower atmosphere during spring and fall 1994.” Novelli, P. C., et al. (1998), J. Geophys. Res., 103(D15), 19,285–19,293, doi:10.1029/97JD00031.

Recent Changes in Atmospheric Carbon Monoxide – Novelli et al. (1994) “Measurements of carbon monoxide (CO) in air samples collected from 27 locations between 71°N and 41°S show that atmospheric levels of this gas have decreased worldwide over the past 2 to 5 years. During this period, CO decreased at nearly a constant rate in the high northern latitudes. In contrast, in the tropics an abrupt decrease occurred beginning at the end of 1991. In the Northern Hemisphere, CO decreased at a spatially and temporally averaged rate of 7.3 (±0.9) parts per billion per year (6.1 percent per year) from June 1990 to June 1993, whereas in the Southern Hemisphere, CO decreased 4.2 (±0.5) parts per billion per year (7.0 percent per year). This recent change is opposite a long-term trend of a 1 to 2 percent per year increase inferred from measurements made in the Northern Hemisphere during the past 30 years.” Paul C. Novelli, Ken A. Masarie, Pieter P. Tans and Patricia M. Lang, Science 18 March 1994: Vol. 263 no. 5153 pp. 1587-1590, DOI: 10.1126/science.263.5153.1587.

Mixing Ratios of Carbon Monoxide in the Troposphere – Novelli et al. (1992) “Carbon monoxide (CO) mixing ratios were measured in air samples collected weekly at eight locations. The air was collected as part of the CMDL/NOAA cooperative flask sampling program (Climate Monitoring and Diagnostics Laboratory, formerly Geophysical Monitoring for Climatic Change, Air Resources Laboratory/National Oceanic and Atmospheric Administration) at Point Barrow, Alaska (71°N), Niwot Ridge, Colorado (40°N), Mauna Loa and Cape Kumakahi, Hawaii (19°N), Guam, Marianas Islands (13°N), Christmas Island (2°N), Ascension Island (8°S) and American Samoa (14°S). Half-liter or 3-L glass flasks fitted with glass piston stopcocks holding teflon O rings were used for sample collection. CO levels were determined within several weeks of collection using gas chromatography followed by mercuric oxide reduction detection, and mixing ratios were referenced against the CMDL/NOAA carbon monoxide standard scale. During the period of study (mid-1988 through December 1990) CO levels were greatest in the high latitudes of the northern hemisphere (mean mixing ratio from January 1989 to December 1990 at Point Barrow was approximately 154 ppb) and decreased towards the south (mean mixing ratio at Samoa over a similar period was 65 ppb). Mixing ratios varied seasonally, the amplitude of the seasonal cycle was greatest in the north and decreased to the south. Carbon monoxide levels were affected by both local and regional scale processes. The difference in CO levels between northern and southern latitudes also varied seasonally. The greatest difference in CO mixing ratios between Barrow and Samoa was observed during the northern winter (about 150 ppb). The smallest difference, 40 ppb, occurred during the austral winter. The annually averaged CO difference between 71°N and 14°S was approximately 90 ppb in both 1989 and 1990; the annually averaged interhemispheric gradient from 71°N to 41°S is estimated as approximately 95 ppb.” Novelli, P. C., L. P. Steele, and P. P. Tans (1992), J. Geophys. Res., 97(D18), 20,731–20,750, doi:10.1029/92JD02010.

The global cycle of carbon monoxide: Trends and mass balance – Khalil & Rasmussen (1990) “The annual global emissions of CO are estimated to be about 2,600 ± 600 Tg, of which about 60% are from human activities including combustion of fossil fuels and oxidation of hydrocarbons including methane. The remaining 40% of the emissions are from natural processes, mostly from the oxidation of hydrocarbons but also from plants and the oceans. Almost all the CO emitted into the atmosphere each year is removed by reactions with OH radicals (85%), by soils (10%), and by diffusion into the stratosphere. There is a small imbalance between annual emissions and removal, causing an increase of about 1% per year. It is very likely that the imbalance is due to increasing emissions from anthropogenic activities. The average concentration of CO is about 90 ppbv, which amounts to about 400 Tg in the atmosphere, and the average lifetime is about 2 months. This view of the global cycle of CO is consistent with the present estimates of average OH concentrations and the budgets of other trace gases including methane and methylchloroform. There are large remaining uncertainties that may in the future upset the apparently cohesive present budget of CO. If the present view of the global cycle of CO is correct, then it is likely that, in time, increasing levels of CO will contribute to widespread changes in atmospheric chemistry.” M.A.K. Khalil, a and R.A. Rasmussen, Chemosphere, Volume 20, Issues 1-2, 1990, Pages 227-242, doi:10.1016/0045-6535(90)90098-E.

Spectroscopic measurements of atmospheric carbon monoxide and methane. 1: latitudinal distribution – Dianov-Klokov et al. (1989) “The results of spectroscopic total column measurements of CO and CH4 at different points of the Northern and Southern Hemispheres in 1970–1985, are reported. Seasonal cycles of CO are evident for all the sites. The Northern Hemispheric long-term positive trend of CO seems to be 1.5–2% per year. In the Southern Hemisphere, temporal increasing was not detected and a possible upper limit for it is about 0.6% per year. Methane concentration in the Northern Hemisphere increases at a rate of 1.2% per year.” V. I. Dianov-Klokov, L. N. Yurganov, E. I. Grechko and A. V. Dzhola, Journal of Atmospheric Chemistry, Volume 8, Number 2, 139-151, DOI: 10.1007/BF00053719. [full text]

Spectroscopic measurements of atmospheric carbon monoxide and methane. 2: Seasonal variations and long-term trends – Dianov-Klokov & Yurganov (1989) “A spectroscopic technique for measuring CO and CH4 contents is described and the latitudinal distributions of these gases are presented. Carbon monoxide abundance decreases southward, having two local maxima: in midlatitudes and in the tropics. The slope of latitude dependence varies according to the season of the year. The difference in CH4 content does not exceed the accuracy of the method (±8%).” V. I. Dianov-Klokov and L. N. Yurganov, Journal of Atmospheric Chemistry, Volume 8, Number 2, 153-164, DOI: 10.1007/BF00053720.

A survey of continental concentrations of atmospheric CO in the southern hemisphere – Kirchhoff & Marinho (1989) “The first large scale survey of surface CO concentrations at Southern Hemisphere continental sites is described. Marine sites are compared to sites with a true continental character with the objective to identify different ecological surface conditions in terms of CO concentrations. The marine sites at the Atlantic coast show the lowest concentrations, about 100 ppbv, whereas the sites in the savannah region show concentrations 3 times as large owing to the influence of nearby biomass burning activity. The observations were highly variable, with one result as high as 700 ppbv. These high values are comparable to sites near urban developments. Sites in the Amazonian rain forest show concentrations as low as the coastal sites, on the average, but sporadic peaks have been seen when air masses are brought in from city areas or from large forest fires.” V.W.J.H. Kirchhoff and E.V.A. Marinho, Atmospheric Environment, Volume 23, Issue 2, 1989, Pages 461-466, doi:10.1016/0004-6981(89)90589-1.

Carbon monoxide in the Earth’s atmosphere: indications of a global increase – Khalil & Rasmussen (1988) “Over half of the carbon monoxide in the atmosphere comes from human activities including motor traffic, other combustion of fossil fuels, and slash and burn agriculture1–4. Additional anthropogenic sources include the burning of wood, savannah lands, and the oxidation of hydrocarbons including methane. Over the years these sources have increased gradually and may have already caused the concentrations of CO to double since pre-industrial times when human activities did not significantly affect the global cycles of CO and other trace gases. Increasing levels of CO can lead to an increase of tropospheric O3 (refs 5,6) and a build-up of many other trace gases in the Earth’s atmosphere, which may in turn cause widespread perturbations of tropospheric chemistry, global warming, and other climatic changes7. In a recent report8 to senior US Government officials the National Academies stated the urgent need to know the global distribution and trends of CO. During the past 6–8 years we have taken systematic measurements of CO at sites ranging from within the Arctic Circle to the South Pole. The rates of increase of the globally averaged concentration are between 0.8% and 1.4% per year depending on the statistical method used for estimating the trends. These increases may have gone on for much longer because more than half of the atmospheric CO now comes from anthropogenic sources. We find that the rates of increase are largest at mid-northern and tropical latitudes, where most of the sources are located.” M. A. K. Khalil & R. A. Rasmussen, Nature 332, 242 – 245 (17 March 1988); doi:10.1038/332242a0.

The seasonality of CO abundance in the Southern Hemisphere – Seiler et al. (1984) “CO mixing ratios in air have been measured continuously at Cape Point (34°21prime;S; 18°29’E) between 1978 and 1981. The results show a seasonal variation of the CO mixing ratios with minimum values of 53 p.p.b.v. during January/February and maximum values of 87 p.p.b.v. during September/October. Short-term variations of CO mixing ratios in clean, undisturbed air were lacking, indicating that CO is well mixed in the Southern Hemisphere at latitudes of 20–40° S and that the observed seasonal variation is not due to temporal changes of local and regional source strengths. The seasonality of CO is explained by the seasonal variation of OH and by the north–south shift of the intertropical convergence zone. The agreement of CO mixing ratios measured at Cape Point and over the Southern Atlantic in 1971/1972 indicates that the southern hemispheric CO mixing ratios cannot have changed by more than 5–10% during the last decade.” Wolfgang Seiler, Helmut Giehl, Ernst-Günther Brunke, Eric Halliday, Tellus B, Volume 36B, Issue 4, pages 219–231, September 1984, DOI: 10.1111/j.1600-0889.1984.tb00244.x.

The Distribution of Carbon Monoxide and Ozone in the Free Troposphere – Seiler & Fishman (1981) “The two-dimensional distributions of CO and O3 in the free troposphere during July and August, 1974, are discussed. The data confirm the previous findings that both of these gases are considerably more abundant in the northern hemisphere, but the degree of the asymmetry is somewhat different from what had been reported previously, especially for CO. When examined with respect to other available data sets, the conclusion is drawn that a pronounced seasonal cycle exists for CO in both hemispheres which may be driven by the likely seasonal cycle of the OH radical. The data also indicate that CO concentrations exhibit significant variability with height in the northern hemisphere, whereas southern hemispheric concentrations are quite constant with altitude except in cases where interhemispheric exchange of air may be occurring. A discussion on the vertical and horizontal transport processes inferred from the CO and O3 measurements is presented. The possible interdependence of the photochemical cycles of these two trace gases is also discussed.” Seiler, W., and J. Fishman (1981), J. Geophys. Res., 86(C8), 7255–7265, doi:10.1029/JC086iC08p07255.

The cycle of atmospheric CO – Seiler (1974) “New measurements of the CO-mixing ratio in the two hemispheres with the dissolved CO in surface seawater together with previous results are used to set up a detailed budget of CO in the atmosphere. It is shown that CO is produced by technological and by natural sources. The source strengths of both kinds of sources are of the same magnitude. The total CO-production rate is estimated to be 10 × 1014 g per year. The corresponding residence time is 0.5 years. From the observed latitudinal CO-distribution between the hemispheres the production of CO by the oxidation of methane in the troposphere is judged to be a minor source. CO is removed by microbiological processes at the soil surfaces, by photochemical consumption in the stratosphere, and probably also by reaction with OH radicals in the troposphere.” Wolfgang Seiler, Tellus, Volume 26, Issue 1-2, pages 116–135, February 1974, DOI: 10.1111/j.2153-3490.1974.tb01958.x.

The Abundance of Atmospheric Carbon Monoxide above Columbus, Ohio – Shaw (1958) “From measurements of the line R(3) of the 4.7 μ fundamental band appearing in the solar spectrum, the usual CO content of the atmosphere above Columbus, Ohio, during1952-53 has been found to be between 0.04 and 0.07 atm-cm/air mass. There is evidence for some increase in CO content on occasional days during the colder months of the year, but, because the line measured is contaminated by a weak H2O absorption, it is not possible to show that similar increases also occur during the summer months. The occasions of high CO contentare usually associated with periods of low visibility and usually occur during the early part of the day. This is especially true of the period October 20-November 13, 1952, when the worst forest fires for twenty years were burning in southeastern Ohio and states farther south. The present data are compared with the results of other workers.” Shaw, J. H., Astrophysical Journal, vol. 128, p.428, 1958. [full text]

The absorption due to carbon monoxide in the infrared solar spectrum – Locke & Herzberg (1953) “New tracings of the absorption bands due to carbon monoxide in the 4.7 μ and 2.4 μ regions of the solar spectrum were obtained with a spectrometer of high resolving power. From the observed absorption intensity at 4.7 μ the abundance of carbon monoxide in the earth’s atmosphere over Ottawa was found, during spring and fall 1952, to vary between 0.1 and 0.2 cm-atm. Similar observations, made at other stations, were re-evaluated with the laboratory data used at Ottawa. The values for the carbon monoxide abundance in the earth’s atmosphere at different geographical locations, determined in this way, were found to be within the limits of the values obtained at Ottawa. Absorption lines due to solar carbon monoxide in the 4.7 μ region of the spectrum were resolved. Their intensity relative to the intensity of the solar carbon monoxide absorption in the 2.4 μ region of the spectrum was found to be in agreement with expectations based on the theoretical curves of growth for solar absorption lines.” J. L. Locke and L. Herzberg, Can. J. Phys. 31(4): 504–516 (1953), doi:10.1139/p53-050.

Investigations of Atmospheric CO at the Jungfraujoch – Benesch et al. (1953) “Analysis of high-resolution solar spectra taken at the Jungfraujoch in Switzerland indicates that the terrestrial atmospheric CO content may vary by a factor of five in extreme cases, and is, furthermore, subject to surprisingly large fluctuations within the period of one hour. These variations are apparently unrelated to the more readily available data on general meteorological conditions, but a mechanism is suggested wherein the fluctuations of the CO may depend on atmospheric irregularities of a more finely detailed nature than those which normally come into consideration in meteorological observations.” W. Benesch, M. Migeotte, and L. Neven, JOSA, Vol. 43, Issue 11, pp. 1119-1123 (1953), doi:10.1364/JOSA.43.001119.

Identification of Carbon Monoxide in the Atmosphere above Flagstaff, Arizona – Adel (1952) No abstract. Adel, Arthur, Astrophysical Journal, vol. 116, p.442, 1952. [full text]

The Fundamental Band of Carbon Monoxide at 4.7μ in the Solar Spectrum – Migeotte (1949) No abstract available, but according to Shaw (1958) this is first identification of CO in Earth’s atmosphere. Marcel V. Migeotte, Phys. Rev. 75, 1108–1109 (1949).

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Papers on weekly cycle in climate

Posted by Ari Jokimäki on January 5, 2011

This is a list of papers showing observations of weekly cycle in climate related variables. Weekly cycle in climate parameters is suggestive of anthropogenic control. Papers on so called “weekend effect” are also included. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (February 5, 2012): Asmi (2012) and Pollack et al. (2012) added.
UPDATE (November 5, 2011): Rosenfeld & Bell (2011) and Tuttle & Carbone (2011) added.

Airborne and ground-based observations of a weekend effect in ozone, precursors, and oxidation products in the California South Coast Air Basin – Pollack et al. (2012) “Airborne and ground-based measurements during the CalNex (California Research at the Nexus of Air Quality and Climate Change) field study in May/June 2010 show a weekend effect in ozone in the South Coast Air Basin (SoCAB) consistent with previous observations. The well-known and much-studied weekend ozone effect has been attributed to weekend reductions in nitrogen oxide (NOx = NO + NO2) emissions, which affect ozone levels via two processes: (1) reduced ozone loss by titration and (2) enhanced photochemical production of ozone due to an increased ratio of non-methane volatile organic compounds (VOCs) to NOx. In accord with previous assessments, the 2010 airborne and ground-based data show an average decrease in NOx of 46 ± 11% and 34 ± 4%, respectively, and an average increase in VOC/NOx ratio of 48 ± 8% and 43 ± 22%, respectively, on weekends. This work extends current understanding of the weekend ozone effect in the SoCAB by identifying its major causes and quantifying their relative importance from the available CalNex data. Increased weekend production of a VOC-NOx oxidation product, peroxyacetyl nitrate, compared to a radical termination product, nitric acid, indicates a significant contribution from increased photochemical production on weekends. Weekday-to-weekend differences in the products of NOx oxidation show 45 ± 13% and 42 ± 12% more extensive photochemical processing and, when compared with odd oxygen (Ox = O3 + NO2), 51 ± 14% and 22 ± 17% greater ozone production efficiency on weekends in the airborne and ground-based data, respectively, indicating that both contribute to higher weekend ozone levels in the SoCAB.” Pollack, I. B., et al. (2012), Airborne and ground-based observations of a weekend effect in ozone, precursors, and oxidation products in the California South Coast Air Basin, J. Geophys. Res., 117, D00V05, doi:10.1029/2011JD016772.

Weakness of the weekend effect in aerosol number concentrations – Asmi (2012) “Weekday related anthropogenic aerosol emissions have been suggested to affect regional climate via indirect aerosol effects. I studied the variability of potential cloud condensation nuclei using measurements of number size distributions of Cloud Condensation Nuclei (CCN) -sized aerosol particles and CCNs measured at several European regional background stations, located at a wide variety of environments. With notably rare exceptions, there were no statistically significant difference between concentrations on different weekdays. I further analysed the concentration timeseries of four long-period datasets in Germany and Finland with wavelet analysis. Outside of urban areas, very little weekday-connected variability was found. The lack of 7-day variability outside of cities is in contrast of earlier studies in this field, which used mostly particle mass as the representative measure of aerosol concentration. A time-scale and variability analysis showed that PM10 and PM2.5 are more sensitive for the weekly variation than CCN-sized particles. Using mass-based variations as a proxy for short-term variations of CCN particle numbers can thus overestimate the weekend effect for these particles. The results of this study do not support aerosol indirect effects from 50 to 500 nm diameter particles as a major contributor on potential weekday connected variations in European meteorology.” Ari Asmi, Atmospheric Environment, http://dx.doi.org/10.1016/j.atmosenv.2012.01.060.

Inferences of weekly cycles in summertime rainfall – Tuttle & Carbone (2011) “In several continental regions a weekly cycle of air pollution aerosols has been observed. It is usually characterized by concentration minima on weekends (Saturday and Sunday) and maxima on weekdays (Tuesday–Friday). Several studies have associated varying aerosol concentrations with precipitation production and attempted to determine whether or not there is a corresponding weekly cycle of precipitation. Results to date have been mixed. Here we examine a 12 year national composited radar data set for evidence of weekly precipitation cycles during the warm season (June–August). Various statistical quantities are calculated and subjected to “bootstrap” testing in order to assess significance. In many parts of the United States, warm season precipitation is relatively infrequent, with a few extreme events contributing to a large percentage of the total 12 year rainfall. For this reason, the statistics are often difficult to interpret. The general area east of the Mississippi River and north of 37°N contains regions where 25%–50% daily rainfall increases are inferred for weekdays (Tuesday–Friday) relative to weekends. The statistics suggest that western Pennsylvania is the largest and most likely contiguous region to have a weekly cycle. Parts of northern Florida and southeastern coastal areas infer a reverse-phase cycle, with less rainfall during the week than on weekends. Spot checks of surface rain gauge data confirm the phase of these radar-observed anomalies in both Pennsylvania and Florida. While there are indications of a weekly cycle in other locations of the United States, the degree of confidence is considerably lower. There is a strong statistical inference of weekday rainfall maxima over a net 8% of the area examined, which is approximately twice the area of cities. Future examination of lofted aerosol content, related condensation/ice nuclei spectra, and knowledge of the convective dynamical regime are needed in order to assess how anthropogenic aerosols may affect rainfall at urban and regional scales. If radar is the primary method of observation, it is also necessary to examine the effects of variable aerosol content on the parametric relationship between rainfall rate and radar reflectivity factor. Polarimetric radar observations could also serve to verify microphysical-dynamical hypotheses regarding precipitation production.” Tuttle, J. D., and R. E. Carbone (2011), J. Geophys. Res., 116, D20213, doi:10.1029/2011JD015819.

Why do tornados and hailstorms rest on weekends? – Rosenfeld & Bell (2011) “This study shows for the first time statistical evidence that when anthropogenic aerosols over the eastern United States during summertime are at their weekly mid-week peak, tornado and hailstorm activity there is also near its weekly maximum. The weekly cycle in summertime storm activity for 1995–2009 was found to be statistically significant and unlikely to be due to natural variability. It correlates well with previously observed weekly cycles of other measures of storm activity. The pattern of variability supports the hypothesis that air pollution aerosols invigorate deep convective clouds in a moist, unstable atmosphere, to the extent of inducing production of large hailstones and tornados. This is caused by the effect of aerosols on cloud drop nucleation, making cloud drops smaller and hydrometeors larger. According to simulations, the larger ice hydrometeors contribute to more hail. The reduced evaporation from the larger hydrometeors produces weaker cold pools. Simulations have shown that too cold and fast-expanding pools inhibit the formation of tornados. The statistical observations suggest that this might be the mechanism by which the weekly modulation in pollution aerosols is causing the weekly cycle in severe convective storms during summer over the eastern United States. Although we focus here on the role of aerosols, they are not a primary atmospheric driver of tornados and hailstorms but rather modulate them in certain conditions.” Rosenfeld, D., and T. L. Bell (2011), J. Geophys. Res., 116, D20211, doi:10.1029/2011JD01.

An Empirical Study of Geographic and Seasonal Variations in Diurnal Temperature Range – Jackson & Forster (2010) “The diurnal temperature range (DTR) of surface air over land varies geographically and seasonally. The authors have investigated these variations using generalized additive models (GAMs), a nonlinear regression methodology. With DTR as the response variable, meteorological and land surface parameters were treated as explanatory variables. Regression curves related the deviation of DTR from its mean value to values of the meteorological and land surface variables. Cloud cover, soil moisture, distance inland, solar radiation, and elevation were combined as explanatory variables in an ensemble of 84 GAM models that used data grouped into seven vegetation types and 12 months. The ensemble explained 80% of the geographical and seasonal variation in DTR. Vegetation type and cloud cover exhibited the strongest relationships with DTR. Shortwave radiation, distance inland, and elevation were positively correlated with DTR, whereas cloud cover and soil moisture were negatively correlated. A separate analysis of the surface energy budget showed that changes in net longwave radiation represented the effects of solar and hydrological variation on DTR. It is found that vegetation and its associated climate is important for DTR variation in addition to the climatic influence of cloud cover, soil moisture, and solar radiation. It is also found that surface net longwave radiation is a powerful diagnostic of DTR variation, explaining over 95% of the seasonal variation of DTR in tropical regions.” Jackson, Lawrence S., Piers M. Forster, 2010, J. Climate, 23, 3205–3221, doi: 10.1175/2010JCLI3215.1.

Weekend effect: Anthropogenic or natural? – Kim et al. (2010) “Human activities have been suggested to result in weekly changes of meteorological variables, called the “weekend effect.” Recent debates on its statistical significance, however, reveal that there still remain huge uncertainties as to the anthropogenic origin of the weekend effect. We show that atmospheric Rossby waves induce the “natural” weekend effect, which is much stronger than the “anthropogenic” weekend effect. The “natural” weekend effect does not completely disappear even with averaging over 61 years of data; as a result, true “anthropogenic” weekend effect is obscured by the natural component. We attempted to remove the “natural” component in the diurnal temperature range and the resulting pattern is an overall positive weekend effect over North America.” Kim, K.-Y., R. J. Park, K.-R. Kim, and H. Na (2010), Geophys. Res. Lett., 37, L09808, doi:10.1029/2010GL043233. [full text]

The Detection of Weekly Preferential Occurrences with an Application to Rainfall – Marani (2010) “The detection of weekly preferential occurrences in atmospheric and hydrologic processes has recently attracted much attention as a way to identify the signature of anthropogenic climatic changes. The interpretation of previous analyses, however, is not unequivocal, in part as a result of a lack of widely accepted statistical criteria. Here, a general and exact method to detect the presence of weekly preferential occurrences is developed and applied to long rainfall observations in Marghera, Italy; Philadelphia, Pennsylvania; and Portland, Maine. The method makes use of the fact that, under the null hypothesis of stationarity, the process of event occurrence in the different days of the week is equivalent to the random distribution of a number of balls (the wet days) in a set of boxes (the days of the week). The departure from a homogeneous distribution is then characterized through the probability of the maximum number of balls in a box, which can be computed exactly with no ad hoc assumptions. The new method shows that (i) preferential rainfall weekly occurrences emerge in all cases in the most recent period analyzed (1990–2006), while they are absent—or are too weak to be detected—in previous years (before 1989); and (ii) the balls-in-boxes approach appears to be more sensitive than Pearson’s test when deviations from homogeneity are associated with just one day of the week, a common occurrence in connection with day-of-the-week effects. The results presented help to reconcile previous contrasting studies and to contribute compelling evidence that anthropogenic changes in the local climate have occurred over the past century in urban and industrial areas.” Marani, Marco, 2010, J. Climate, 23, 2379–2387, doi: 10.1175/2009JCLI3313.1.

Day-of-the-week variations of urban temperature and their long-term trends in Japan – Fujibe (2010) “Temperature differences among days of the week and their long-term trends were evaluated using 29 years of hourly data from the Automated Meteorological Data Acquisition System network of Japan. Stations were categorized with respect to the population density around each site, and an urban temperature anomaly (δT*) was defined as a departure from the spatial average of nearby rural stations. On Saturdays and holidays (Sundays and national holidays), δT* was lower than on weekdays by 0.2–0.25°C at Tokyo, by 0.1–0.2°C at Osaka, and by about 0.02°C at stations where the population density was 300 to 1,000 km–2. Moreover, δT* showed a relative decreasing trend over the long term on Mondays and an increasing trend on Fridays, at a rate of about 0.05–0.1°C decade–1 at Tokyo and about 0.02°C decade–1 at stations where the population density was 100 to 1,000 km–2, but no significant difference in δT* trends was observed between weekdays and weekend days.” Fumiaki Fujibe, Theoretical and Applied Climatology, Volume 102, Numbers 3-4, 393-401, DOI: 10.1007/s00704-010-0266-y.

Long-term changes in summer weekend effect over northeastern China and the connection with regional warming – Ho et al. (2009) “The 7-day cycle of human activities may lead to the “weekend effect” in climate variables and air pollutants. The weekend effect is defined as the average value (e.g., the diurnal temperature range) for Saturday through Monday minus the average value for Wednesday through Friday. A composite of the ground observations over northeastern China presents that, during 26-year (1980–2005) summers, the weekend effect in the diurnal temperature range increased by 1.2°C. Conversely, the weekend effects in the relative humidity, cloud amount, and light rain (≤5 mm day−1) events decreased. These changes are due to a shifted phase of the weekly cycle of the meteorological variables. The long-term change in weekend effects have a high correlation coefficient (∣r∣ ≈ 0.8) with the decrease in relative humidity over the region, which is likely induced by regional warming. The results suggest that regional warming is a possible factor in a transition of dominant aerosol effects in the weekend effect.” Ho, C.-H., Y.-S. Choi, and S.-K. Hur (2009), Geophys. Res. Lett., 36, L15706, doi:10.1029/2009GL039509.

Weekly periodicities of Aerosol Optical Thickness over Central Europe – evidence of an anthropogenic direct aerosol effect – Bäumer et al. (2008) “Statistical analyses of data from ground-based sun photometer stations in Central Europe are presented. All stations are part of the Aerosol Robotic Network (AERONET), and only data of the highest data quality level 2.0 has been applied. The averages by weekday of Aerosol Optical Thickness (AOT) at a wavelength of 440 nm of 12 of the 14 stations in the investigation area show a weekly periodicity with lowest values on Sunday and Monday, but greatest values from Wednesday until Saturday, that is significant at least on a 90% level. The stations in Germany and in Greater Paris show weekly cycles with ranges of about 20% on average. In Northern Italy and Switzerland this range is about 10% on average. By applying several checks, we exclude that the weekly cycles were caused by a maintenance effect or by different retrieval conditions as a consequence of a weekly cycle in cloud cover. The corresponding weekly cycle of anthropogenic gaseous and particulate emissions leads us to the conclusion of the anthropogenic origin of the weekly AOT cycle. Since these AOT patterns are derived from the reduction of the direct sun radiation by the columnar atmospheric aerosol, this result represents strong evidence for an anthropogenic direct aerosol effect on shortwave radiation. Furthermore, this study makes a first contribution to the understanding and explanation of recently observed weekly periodicities in meteorological variables as temperature in Germany.” Bäumer, D., Rinke, R., and Vogel, B., Atmos. Chem. Phys., 8, 83-90, doi:10.5194/acp-8-83-2008, 2008. [full text]

Winter “weekend effect” in southern Europe and its connections with periodicities in atmospheric dynamics – Sanchez-Lorenzo et al. (2008) “Winter weekly cycles of different climatic variables have been detected over Spain during the 1961–2004 period. The 13 analyzed series come from stations placed on different climatological and geographical areas with different level of urban influence. Therefore, the weekly cycles can hardly be related with local effects. Contrarily, we suggest that the weekly cycles may be related with changes in the atmospheric circulation over Western Europe, which may be due to some indirect effect of anthropogenic aerosols. Particularly interesting is the observed increase in Sea Level Pressure over Southern Europe during the weekends and consequently a decrease of anticyclonic conditions during the central weekdays.” Sanchez-Lorenzo, A., J. Calbó, J. Martin-Vide, A. Garcia-Manuel, G. García-Soriano, and C. Beck (2008), Geophys. Res. Lett., 35, L15711, doi:10.1029/2008GL034160.

Analysis of the weekly cycle of aerosol optical depth using AERONET and MODIS data – Xia et al. (2008) “Multi-year Aerosol Robotic Network (AERONET) and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) data are used to study AOD weekly variations at the global scale. A clear weekly cycle of AOD is observed in the United States (U.S.) and Central Europe. AOD during the weekday is larger than that during the weekend in 36 out of 43 AERONET sites in the U.S. The average U.S. weekend effect (the percent difference in AOD during the weekday and the weekend) is 3.8%. A weekly periodicity with lower AODs on Sunday and Monday and higher AODs from Wednesday until Saturday is revealed over Central Europe and the average weekend effect there is 4.0%. The weekly cycle in urban sites is greater than that in rural sites. AOD during the weekday is also significantly larger than that during the weekend in urban AERONET sites in South America and South Korea. However, a reversed AOD weekly cycle is observed in the Middle East and India. AODs on Thursday and Friday, the “weekend” for Middle East cultures, are relatively lower than AODs on other days. There is no clear weekly variation of AOD over eastern China. The striking feature in this region is the occurrence of much higher AOD on Sunday and this phenomenon is independent of season. The analysis of MODIS aerosol data is in good agreement with that of AERONET data.” Xia, X., T. F. Eck, B. N. Holben, G. Phillippe, and H. Chen (2008), J. Geophys. Res., 113, D14217, doi:10.1029/2007JD009604.

An unexpected pattern of distinct weekly periodicities in climatological variables in Germany – Bäumer & Vogel (2007) “Statistical analyses of data from 12 German meteorological stations meeting WMO standards in the period 1991–2005 are presented. These stations represent different local climate conditions in terms of both meteorology and pollution situation. For the average over data of all stations, we identified significant weekly periodicities in many variables such as temperature, daily temperature range, sunshine duration, cloud amount, precipitation, and precipitation frequency. Not only data of stations situated in congested urban areas, but also data of remote stations as e.g. on Mount Zugspitze 2960 m above sea level in the Alps showed significant in-phase weekly cycles. These weekly periodicities cannot be explained completely by local pollution effects or local heat emissions. We tend towards the hypothesis that the anthropogenic weekly emission cycle and the subsequent aerosol cycle interact with the atmospheric dynamics on a larger scale which leads to a forcing of a naturally existing 7-day period among the spectrum of atmospheric periods.” Bäumer, D., and B. Vogel (2007), Geophys. Res. Lett., 34, L03819, doi:10.1029/2006GL028559. [full text]

Weekly precipitation cycles? Lack of evidence from United States surface stations – Schultz et al. (2007) “Previous work has inferred a relationship between human activity and the occurrence and amount of precipitation through examining possible weekly cycles in precipitation. Daily precipitation records for 219 surface observing stations in the United States for the 42-year period 1951–1992 are investigated for weekly cycles in precipitation. Results indicate that neither the occurrence nor amount of precipitation significantly depends upon the day of the week.” Schultz, D. M., S. Mikkonen, A. Laaksonen, and M. B. Richman (2007), Geophys. Res. Lett., 34, L22815, doi:10.1029/2007GL031889. [full text]

Weekly cycle of aerosol-meteorology interaction over China – Gong et al. (2007) “Weekly cycles of the concentration of anthropogenic aerosols have been observed in many regions around the world. The phase and the magnitude of these cycles, however, vary greatly depending on region and season. In the present study the authors investigated important features of the weekly cycles of aerosol concentration and the covariations in meteorological conditions in major urban regions over east China, one of the most polluted areas in the world, in summertime during the period 2001–2005/2006. The PM10 (aerosol particulate matters of diameter < 10 μm) concentrations at 29 monitoring stations show significant weekly cycles with the largest values around midweek and smallest values in weekend. Accompanying the PM10 cycle, the meteorological variables also show notable and consistent weekly cycles. The wind speed in the lower troposphere is relatively small in the early part of the week and increases after about Wednesday. At the same time, the air temperature anomalies in low levels are positive and then become negative in the later part of the week. The authors hypothesize that the changes in the atmospheric circulation may be triggered by the accumulation of PM10 through diabatic heating of lower troposphere. During the early part of a week the anthropogenic aerosols are gradually accumulated in the lower troposphere. Around midweek, the accumulated aerosols could induce radiative heating, likely destabilizing the middle to lower troposphere and generating anomalously vertical air motion and thus resulting in stronger winds. The resulting circulation could promote ventilation to reduce aerosol concentrations in the boundary layer during the later part of the week. Corresponding to this cycle in anthropogenic aerosols the frequency of precipitation, particularly the light rain events, tends to be suppressed around midweek days through indirect aerosol effects. This is consistent with the observed anthropogenic weather cycles, i.e., more (less) solar radiation near surface, higher (lower) maximum temperature, larger (smaller) diurnal temperature range, and fewer (more) precipitation events in midweek days (weekend).” Gong, D.-Y., C.-H. Ho, D. Chen, Y. Qian, Y.-S. Choi, and J. Kim (2007), J. Geophys. Res., 112, D22202, doi:10.1029/2007JD008888. [full text, slide show]

Weekend effect in diurnal temperature range in China: Opposite signals between winter and summer – Gong et al. (2006) “Intense human activity can impact weather and climate in many ways. One possible important consequence is the weekly cycle (so-called weekend effect) in the diurnal temperature range (DTR). The weekend effect is defined as the average DTR for Saturday through Monday minus the average DTR for Wednesday through Friday. In the present study, the weekend effect in the DTR over east China combined with station observations of maximum and minimum temperatures, relative humidity, and total solar irradiance for the period 1955–2000 was analyzed. Results show that the weekend effect in the DTR has the opposite signal between winter (December, January, and February) and summer (June, July, and August). Wintertime DTR tends to have a positive weekend effect (i.e., larger DTR in weekend days compared to weekdays), in association with increased maximum temperature and total irradiance but decreased relative humidity. While summertime DTR displays a much stronger and significantly negative weekend effect (i.e., smaller DTR in weekend days), in association with decreased maximum temperature and total solar irradiance but increased relative humidity and a greater number of rainy days. This study indicates that the DTR difference between weekend and weekdays is predominantly related to weekly changes in the maximum temperature. The weekend effect in the DTR and maximum temperature is also found in the Reanalysis 2 data. The weekend effect in winter is supported by an analogous holiday (Spring Festival) effect. Since the late 1970s, the weekend effect has been enhanced in both winter and summer, concurrent with rapid development and enhanced human activity in China. The direct and indirect effects of human-related aerosols on radiation, cloud, precipitation, and so on, might play an important role in generating the opposite signal in the weekend effect for different seasons. During a dry winter, the reduction of aerosol concentrations may overwhelmingly impact on the DTR through a direct effect, i.e., by increasing total solar irradiance near the surface and raising the daytime temperature and maximum temperature and lowering relative humidity. By contrast, in summer the indirect effect of aerosols, i.e., reduction in precipitation efficiency caused by more numerous and smaller cloud droplets, would largely be responsible for the increased numbers of rainy days, the reduction of the total solar irradiance, and the lowering of the maximum temperature and DTR.” Gong, D.-Y., D. Guo, and C.-H. Ho (2006), J. Geophys. Res., 111, D18113, doi:10.1029/2006JD007068. [full text]

Comparison of 7 years of satellite-borne and ground-based tropospheric NO2 measurements around Milan, Italy – Ordóñez et al. (2006) “Tropospheric NO2 vertical column densities (VCDs) over the Lombardy region were retrieved from measurements of the Global Ozone Monitoring Experiment (GOME) spectrometer for the period 1996–2002 using a differential optical absorption method. This data set was compared with in situ measurements of NO2 at around 100 ground stations in the Lombardy region, northern Italy. The tropospheric NO2 VCDs are reasonably well correlated with the near-surface measurements under cloud-free conditions. However, the slope of the tropospheric VCDs versus ground measurements is higher in autumn-winter than in spring-summer. This effect is clearly reduced when the peroxyacetyl nitrate and nitric acid (HNO3) interferences of conventional NOx analyzers are taken into account. For a more quantitative comparison, the NO2 ground measurements were scaled to tropospheric VCDs using a seasonal NO2 vertical profile over northern Italy calculated by the Model of Ozone and Related Tracers 2 (MOZART-2). The tropospheric VCDs retrieved from satellite and those determined from ground measurements agree well, with a correlation coefficient R = 0.78 and a slope close to 1 for slightly polluted stations. GOME cannot reproduce the high NO2 amounts over the most polluted stations, mainly because of the large spatial variability in the distribution of pollution within the GOME footprint. The yearly and weekly cycles of the tropospheric NO2 VCDs are similar for both data sets, with significantly lower values in the summer months and on Sundays, respectively. Considering the pollution level and high aerosol concentrations of this region, the agreement is very good. Furthermore, uncertainties in the ground-based measurements, including the extrapolation to NO2 VCDs, might be as important as those of the NO2 satellite retrieval itself.” Ordóñez, C., A. Richter, M. Steinbacher, C. Zellweger, H. Nüß, J. P. Burrows, and A. S. H. Prévôt (2006), J. Geophys. Res., 111, D05310, doi:10.1029/2005JD006305. [full text]

Weekly periodicity of environmental variables in Phoenix, Arizona – Shutters & Balling (2006) “Though there is no known meteorological cause for weekly cycling of environmental variables, weekly cycles have been discovered at local to global scales, particularly in areas affected by human urbanization. To uncover such cycles in Phoenix, AZ, and to highlight possible mechanisms for their existence, data from several public domain sources were collected and analyzed for cycles in three categories of variables: meteorological, pollution, and human activity measured as vehicle traffic flows. Results indicated that many meteorological and pollution variables do exhibit weekly periodicity and that these cycles are likely due to the weekly pattern of human traffic flows. Atmospheric concentrations of O3 and NOX gases exhibit a high degree of negative correlation, supporting recent research that suggests anthropogenic NOX gases are effective scavengers of ozone in urban cores. Results further suggest that vehicle-generated NOX gases may be a significant generator of atmospheric nitrate particulates. Finally, both traffic flow and NOX gas concentrations display a strong correlation with wind speed in the urban core, though this study does not speculate on a mechanism for this relationship.” Shade T. Shutters and Robert C. Balling Jr., Atmospheric Environment, Volume 40, Issue 2, January 2006, Pages 304-310, doi:10.1016/j.atmosenv.2005.09.037.

Urban aerosols and their variations with clouds and rainfall: A case study for New York and Houston – Jin et al. (2005) “Diurnal, weekly, seasonal, and interannual variations of urban aerosols were analyzed with an emphasis on summer months using 4 years of the NASA Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) observations, in situ Aerosol Robotic Network (AERONET) observations, and in situ U.S. Environmental Protection Agency (EPA) PM2.5 data for one midlatitude city (New York) and one subtropical city (Houston). Seasonality is evident in aerosol optical thickness measurements, with a minimum in January and a maximum in April to July. The diurnal variations of aerosols, however, are detectable but largely affected by local and regional weather conditions, such as surface and upper-level winds. On calm clear days, aerosols peak during the two rush hours in the morning and evening. Furthermore, the anthropogenic-induced weekly cycles of aerosols and clouds are analyzed, which by themselves are weak, as the anthropogenic signal is mixed with noise of natural weather variability. In addition, corresponding cloud properties observed from MODIS demonstrate an opposite phase to the seasonality of aerosols. Nevertheless, no clear relationship was observed between monthly mean aerosols and rainfall measurements from NASA’s Tropical Rainfall Measuring Mission (TRMM), implying that in the summer the aerosol impact may not be the primary reason for the change of urban rainfall amount.” Jin, M., J. M. Shepherd, and M. D. King (2005), J. Geophys. Res., 110, D10S20, doi:10.1029/2004JD005081. [full text]

Atmospheric visibility trends in an urban area in Taiwan 1961–2003 – Tsai (2005) “Climatological observations made in Tainan urban area, southern Taiwan, between 1961 and June 2003 were analyzed along with critical air pollutants monitored from 1994 to June 2003 in order to establish the relationship between atmospheric visibility and major air pollutants and meteorological parameters in the urban area. The visibility discrepancy between weekend and week days was also examined. Average annual visibility in the complete period 1961–2003 was 12.4±4.2 km. However, during the early 1960s it was >20 km, against only 6–7 km between 2002 and 2003. This study revealed a correlation between PM10 and NOx levels, which were higher on weekdays than on weekends, and low weekday visibility. Furthermore, decreased visibility was related mostly to increases in PM10. A weekend effect, in which weekend ozone concentrations exceed weekday concentrations, was also revealed. Mixing layer height is an most important meteorological parameter involved in visibility reduction. Principal component analysis demonstrated that increased vehicular emissions, road traffic dust and industrial activity markedly impacted visibility. Pollutant standard index (PSI) values >100 were characterized by concentrations of PM10 and NOx and atmospheric pressure higher than normal, but with wind speed lower than normal. Regression results for various empirical models of visibility demonstrated that higher PM10 concentrations implied lower visibility ranges, and the parameter of ln[PM10] represented the most significant impact on visibility. Because PM2.5 has a significant impact on visibility, a targeted reduction of PM10 would not completely improve the visual range. However, there is a strong association between presence of PM10 and presence of PM2.5, such that a targeted reduction in PM10 is likely to lead to an increase in visibility.” Ying I. Tsai, Atmospheric Environment, Volume 39, Issue 30, September 2005, Pages 5555-5567, doi:10.1016/j.atmosenv.2005.06.012.

Variations in the diurnal character of tropical cyclone wind speeds – Cerveny & Balling (2005) It is not mentioned in the abstract, but apparently they also found a weekly cycle in their data. “A significant decline in diurnal temperature range (DTR) is identified along the Atlantic seaboard. Recent studies suggest that DTR changes demonstrate a human-created weekly cycle and may therefore be anthropogenic. In this study, we address whether there is a change in the diurnal variation in Tropical Cyclone (TC) wind speeds that is consistent with the DTR trend over land. Our analysis of 34 years of TC activity reveals variations such that the difference between day and night wind speeds of TCs has decreased over time. Our work gives limited support to the contention that TC diurnal wind speed differences are thermally driven and, hence, warmer night temperatures (a smaller DTR over time) are leading to stronger nighttime winds over time. Our study initiates investigation of potential influences of climate changes (such as DTR) on secondary climatic phenomena.” Cerveny, R. S., and R. C. Balling Jr. (2005), Geophys. Res. Lett., 32, L06706, doi:10.1029/2004GL021177.

Observations of a “weekend effect” in diurnal temperature range – Forster & Solomon (2003) “Using surface measurements of maximum and minimum temperatures from the Global Daily Climatological Network data set, we find evidence of a weekly cycle in diurnal temperature range (DTR) for many stations in the United States, Mexico, Japan, and China. The “weekend effect,” which we define as the average DTR for Saturday through Monday minus the average DTR for Wednesday through Friday, can be as large as 0.5 K, similar to the magnitude of observed long-term trends in DTR. This weekend effect has a distinct large-scale pattern that has changed only slightly over time, but its sign is not the same in all locations. The station procedures and the statistical robustness of both the individual station data and the patterns of DTR differences are thoroughly examined. We conclude that the weekend effect is a real short time scale and large spatial scale geophysical phenomenon, which is necessarily human in origin. We thus provide strong evidence of an anthropogenic link to DTR, an important climate indicator. Several possible anthropogenic mechanisms are discussed; we speculate that aerosol-cloud interactions are the most likely cause of this weekend effect, but we do not rule out others.” Piers M. de F. Forster and Susan Solomon, PNAS September 30, 2003, vol. 100 no. 20 11225-11230, doi: 10.1073/pnas.2034034100. [full text]

Weekly cycle of NO2 by GOME measurements: a signature of anthropogenic sources – Beirle et al. (2003) “Nitrogen oxides (NO+NO2=NOx and reservoir species) are important trace gases in the troposphere with impact on human health, atmospheric chemistry and climate. Besides natural sources (lightning, soil emissions) and biomass burning, fossil fuel combustion is estimated to be responsible for about 50% of the total production of NOx. Since human activity in industrialized countries largely follows a seven-day cycle, fossil fuel combustion is expected to be reduced during weekends. This “weekend effect” is well known from local, ground based measurements, but has never been analysed on a global scale before. The Global Ozone Monitoring Experiment (GOME) on board the ESA-satellite ERS-2 allows measurements of NO2 column densities. By estimating and subtracting the stratospheric column, and considering radiative transfer, vertical column densities (VCD) of tropospheric NO2 can be determined (e.g. Leue et al., 2001). We demonstrate the statistical analysis of weekly cycles of tropospheric NO2 VCDs for different regions of the world. In the cycles of the industrialized regions and cities in the US, Europe and Japan a clear Sunday minimum of tropospheric NO2 VCD can be seen. Sunday NO2 VCDs are about 25-50% lower than working day levels. Metropolitan areas with other religious and cultural backgrounds (Jerusalem, Mecca) show different weekly patterns corresponding to different days of rest. In China, no weekly pattern can be found. The presence of a weekly cycle in the measured tropospheric NO2 VCD may help to identify the different anthropogenic source categories. Furthermore, we estimated the lifetime of tropospheric NO2 by analysing the mean weekly cycle exemplarily over Germany, obtaining a value of about 6 h in summer and 18-24 h in winter.” Beirle, S., Platt, U., Wenig, M., and Wagner, T., Atmos. Chem. Phys., 3, 2225-2232, doi:10.5194/acp-3-2225-2003, 2003. [full text]

A weekly cycle in atmospheric carbon dioxide – Cerveny & Coakley (2002) “We present a new statistic called the “Mean Symmetrized Residual” (MSR) for detection and quantification of a weekly cycle in measured daily atmospheric carbon dioxide (CO2). At the Mauna Loa Observatory in Hawaii, we conclude that CO2 concentrations, on average, are significantly lower (0.022 parts per million by volume, ppmv) on weekends (Saturday–Sunday) than during the rest of the week. Over the past twenty-five years, the variation of the mean values of MSR (as a function of day of the week) has been relatively stable. We speculate that the observed weekday/weekend variation in CO2 at Mauna Loa is the result of anthropogenic emissions on Hawaii and nearby sources. We do not detect a weekly cycle in daily CO2 concentration measured at South Pole, Antarctica. This methodology has applicability to a variety of datasets.” Cerveny, R. S., and K. J. Coakley (2002), Geophys. Res. Lett., 29(2), 1028, doi:10.1029/2001GL013952.

The influence of tropospheric ozone on the air temperature of the city of Toronto, Ontario, Canada – Beaney & Gough (2002) “Weekday/weekend variations in tropospheric ozone concentrations were examined to determine whether ground-level greenhouse gases have a significant impact on local climate. The city of Toronto, Canada, was chosen due to a high volume of commuter traffic and frequent exposure to high ozone episodes. Due to day-of-the-week variations in commuter traffic, ozone concentrations were shown to vary significantly between weekdays and weekends. During high ozone episodes weekend air temperatures were significantly higher than those observed on weekdays. As no meteorological phenomenon is known to occur over a 7 day cycle the observed temperature variations were attributed to anthropogenic activity.” Gary Beaney and William A. Gough, Atmospheric Environment, Volume 36, Issue 14, May 2002, Pages 2319-2325, doi:10.1016/S1352-2310(02)00184-X.

Spectral analysis of weekday–weekend differences in ambient ozone, nitrogen oxide, and non-methane hydrocarbon time series in California – Marr & Harley (2002) “We describe the history and spatial distribution of day-of-week differences in ambient ozone, NOx, and VOC concentrations through the analysis of two decades of measurements from sites located throughout California. Spectral analysis of the concentration time series shows that weekly patterns in ozone concentrations, typically with higher values of ozone on weekends, have become more widespread in California between 1980 and 1999. In contrast, a strong weekly pattern in NOx concentrations has been present throughout the entire period, and weekly patterns in VOC concentrations, though not as evident, have also been present during the entire 20-yr period. We examine 8-h average ozone concentrations, which appear to be a more sensitive measure of day-of-week differences in ozone than are 1-h averages. At sites with significant weekly cycles, fluctuations in pollutant concentrations that occur on a weekly time scale account for 6.6±3.5%, 3.0±1.7%, and 2.1±0.9% of the total variance in NOx, NMHC, and ozone concentrations, respectively. Concentrations of all three pollutants have been declining in most locations over the past 20 yr. Our results support the hypothesis that the weekend ozone effect is due to a combination of VOC-sensitivity and reduced NOx emissions on weekends. The spread of the weekend ozone effect may be due to a shift in ozone formation towards VOC-sensitivity, as control programs have reduced emissions of VOC more than NOx.” Linsey C. Marr and Robert A. Harley, Atmospheric Environment, Volume 36, Issue 14, May 2002, Pages 2327-2335, doi:10.1016/S1352-2310(02)00188-7.

Comparison between weekend and weekday ozone concentration in large cities in France – Pont & Fontan (2001) “This paper examines ozone data from five large French cities (Marseilles, Lyon, Paris, Strasbourg and Toulouse) in spring and summer over a three-year period to study the possible influence of local primary pollutant emissions. In these cities the level of traffic emission varies according to the day of the week. There is a decrease of about 25% in traffic emissions between non-consecutive Tuesdays and Sundays. Traffic emissions on Fridays are about 40% more than on non-consecutive Sundays whereas they seem to be similar for non-consecutive Tuesdays and Thursdays. Despite this variation in traffic emissions between Fridays and Sundays, 85% of daily ozone maxima are identical for all days compared; in 15% of cases, percentiles of daily ozone maxima vary by about 20% at the most. This difference is observed for the highest values of daily ozone maxima that we can find both in rural and urban sites. Marseilles is the most pollution-sensitive city; every site of this area is concerned, which gives a regional origin to ozone variability. In the less-populated Toulouse area, differences between ozone on Fridays and Sundays are less significant. Our results show the importance of advection phenomena of ozone. It calls into question strategies of local reductions in traffic during ozone episodes.” Véronique Pont and Jacques Fontan, Atmospheric Environment, Volume 35, Issue 8, 2001, Pages 1527-1535, doi:10.1016/S1352-2310(00)00308-3.

Weekly Precipitation Cycles along the Northeast Corridor? – DeLisi et al. (2001) “Twenty years of precipitation data from seven cities along or near the east coast of the United States from the northern mid-Atlantic region to northern New England have been analyzed to determine if there are any weekly cycles in either daily precipitation frequency or intensity. Any such weekly cycle could be considered evidence of anthropogenic influence on the climate of that region. Data were examined for each individual site and for all sites combined. The data were subjected to various statistical procedures, including one-way analysis of variance, Student’s t-test, and the chi-square goodness-of-fit test. Overall, results were not significant at the 95% confidence level. Thus, this study is unable to detect any weekly cycle in daily precipitation intensity or frequency.” DeLisi, Mark P., Alan M. Cope, Jason K. Franklin, 2001, Wea. Forecasting, 16, 343–353. [full text]

Spectral analysis of air pollutants. Part 1: elemental carbon time series – Hies et al. (2000) “An effective method to analyse different air pollution sources in an elemental carbon time series is presented. As a second feature, this technique allows a fast and efficient classification of monitoring sites. Time series of daily elemental carbon measurements at various urban locations have been evaluated with the corresponding power spectra. Typical and well-known periodicities caused by anthropogenic and meteorological influences have been identified using coherence and phase spectra. It will be shown that domestic heating by coal combustion appears as a 365 day periodicity, traffic contributes 3.5, 4.6 and 7 day peaks in the spectrum and elevated long range elemental carbon can be identified as characteristic peaks with periodicities in the range from 13 to 42 days. As the relative amplitudes of the various influences vary depending on the location of the measurement site in the urban area, the use of estimated power spectra helps to find the influence of traffic, domestic coal-heating and long range transport on the elemental carbon concentration.” Thomas Hies, Renate Treffeisen, Ludwig Sebald and Eberhard Reimer, Atmospheric Environment, Volume 34, Issue 21, 2000, Pages 3495-3502, doi:10.1016/S1352-2310(00)00146-1.

Comparisons of weekday–weekend ozone: importance of biogenic volatile organic compound emissions in the semi-arid southwest USA – Diem (2000) “This paper examines differences between daily maximum weekday and weekend ambient ozone concentrations in the Tucson, AZ metropolitan area. Temporal variations in the Weekend Effect (i.e. weekend ozone concentrations are larger than weekday concentrations) are not explained entirely by changes in anthropogenic emissions of ozone precursor chemicals (i.e. nitrogen oxides and volatile organic compounds). A dramatic change from the Weekend Effect in June to the Weekday Effect (i.e. weekday ozone concentrations are larger than weekend concentrations) in July is associated with the onset of the North American Monsoon. A transition from a relatively dry atmosphere during the arid foresummer months of May and June to a relatively moist atmosphere during the monsoon months of July and August seems to explain the changes in ozone concentrations. Moist conditions are associated with increases in biogenic volatile organic compound (BVOC) emissions in the urban forest and surrounding desert areas. BVOC emissions appear to be an important source of VOCs, especially during the monsoon months. Therefore, an increase in ambient BVOC concentrations from June to July presumably reverses the sensitivity of ozone production in the Tucson area from VOC- to NOx-sensitive.” Jeremy E. Diem, Atmospheric Environment, Volume 34, Issue 20, 2000, Pages 3445-3451, doi:10.1016/S1352-2310(99)00511-7.

Weekly cycles of air pollutants, precipitation and tropical cyclones in the coastal NW Atlantic region – Cerveny & Balling (1998) “Direct human influences on climate have been detected at local scales, such as urban temperature increases and precipitation enhancement, and at global scales. A possible indication of an anthropogenic effect on regional climate is by identification of equivalent weekly cycles in climate and pollution variables. Weekly cycles have been observed in both global surface temperature and local pollution data sets. Here we describe statistical analyses that reveal weekly cycles in three independent regional-scale coastal Atlantic data sets: lower-troposphere pollution, precipitation and tropical cyclones. Three atmospheric monitoring stations record minimum concentrations of ozone and carbon monoxide early in the week, while highest concentrations are observed later in the week. This air-pollution cycle corresponds to observed weekly variability in regional rainfall and tropical cyclones. Specifically, satellite-based precipitation estimates indicate that near-coastal ocean areas receive significantly more precipitation at weekends than on weekdays. Near-coastal tropical cyclones have, on average, significantly weaker surface winds, higher surface pressure and higher frequency at weekends. Although our statistical findings limit the identification of cause–effect relationships, we advance the hypothesis that the thermal influence of pollution-derived aerosols on storms may drive these weekly climate cycles.” Randall S. Cerveny & Robert C. Balling, Jr., Nature 394, 561-563 (6 August 1998) | doi:10.1038/29043. [full text]

Weekly cycle of meteorological variations in Melbourne and the role of pollution and anthropogenic heat release – Simmonds & Keay (1997) “An aspect of anthropogenic impacts on climate have been assessed by examining the day-of-the-week variation (DOWV) of important meteorological elements. The data used were those of daily maximum and minimum temperature and rainfall for Melbourne for the period 1856–1990. This long series has been broken up into five 27-yr subperiods to expose how any such variation has changed over the record. We find there to be no DOWV in the summer “half” of the year for any of the subperiods. The only statistically significant variations to have physical meaning occur in the winter of the most recent subperiod (1964–1990). In that time maximum temperature exhibits a significant (10% confidence level) DOWV and weekdays are 0.29°C warmer than weekends (5%). Minimum temperatures and rainfall amounts were also found to be greater (10% level) on weekdays by 0.24°C and 0.20 mm d−1, respectively. We have considered the possible impacts of day-of-the-week variation of atmospheric pollution loading and of the local generation of heat. We hypothesise that the magnitude of the contrast between weekday-weekend anthropogenic heat emissions is sufficient to explain the temperature differences and these in turn are consistent with the weekday excess of rainfall. This perspective is concordant with the results of many recent studies which stress the importance of anthropogenic heating.” Ian Simmonds and Kevin Keay, Atmospheric Environment, Volume 31, Issue 11, June 1997, Pages 1589-1603, doi:10.1016/S1352-2310(96)00344-5. [full text]

Weekend-weekday differences of near-surface ozone concentrations in Switzerland for different meteorological conditions – Brönnimann & Neu (1997) “Mean weekly cycles of daily ozone peak levels are extracted out of 8 yr data sets under selected meteorological conditions. In the region under study, the emissions of precursor substances are considerably lower on weekends than on weekdays, as can be derived from the Swiss emission inventory or from traffic frequencies. Chemical production as well as destruction of ozone are affected differently by sudden changes in emissions, depending on meteorology and on the structure of the emissions. Therefore, in Switzerland, several distinct patterns of the weekly cycle of mean daily ozone peak concentrations can be detected. When meteorology is not favourable to ozone production, weekends show generally higher ozone peaks than weekdays. Favourable meteorology (i.e. high solar radiation, high temperatures, low wind speeds) produces an inverse pattern, the mean ozone peaks being 10–15% lower on Sundays than on Thursdays or Fridays. Differences in emission structures slightly modify the patterns and can delay the effects. Threshold values to separate favourable conditions can be estimated for radiation and temperature. In Switzerland, “favourable” meteorology is achieved on about 30–50 days per year, corresponding well with “summer smog days”.” Stefan Brönnimann and Urs Neu, Atmospheric Environment, Volume 31, Issue 8, April 1997, Pages 1127-1135, doi:10.1016/S1352-2310(96)00311-1.

C2—C6 hydrocarbon measurements at four rural locations across Canada – Bottenheim & Shepherd (1995) “Observations of low molecular weight hydrocarbons at four rural locations in Canada are reported. The measurements cover a period of one year (1991), and the seasonal trends are discussed. It is deduced that most variation is due to photochemically driven processes (OH chemistry). Although at least two of the sites were well removed from large urban source regions, the observations show a clear anthropogenic influence on the rural hydrocarbon levels at all sites. Air mass back-trajectories have been used to investigate the origin of the observed hydrocarbons. Weekday/weekend effects are distinguishable at two of the sites, and correlation with a limited set of CO observations at one of the sites is found to be very good for those compounds that are known to originate from transportation related processes. Comparison of the data with published observations suggests that the background distribution of hydrocarbons over the North American continent is quite homogeneous. Isoprene is the only hydrocarbon of biogenic origin that was measured in this study, and its importance relative to the other measured compounds with respect to photochemical processes is indicated.” Jan W. Bottenheim and Marjorie F. Shepherd, Atmospheric Environment, Volume 29, Issue 6, 1995, Pages 647-664, doi:10.1016/1352-2310(94)00318-F.

Weekdays warmer than weekends? – Gordon (1994) No abstract available, but is described in Bäumer et al. (2008): “Gordon (1994) found a significant but very small weekly temperature cycle for the northern hemisphere for the period 1979–1992.” A. H. Gordon, Nature 367, 325 – 326 (27 January 1994); doi:10.1038/367325b0.

Photochemistry of the “Sunday Effect” – Graedel et al. (1977) No abstract available, but apparently finds a weekly cycle from pollution data sets. Thomas E. Graedel, Leonilda A. Farrow, Thomas A. Weber, Environ. Sci. Technol., 1977, 11 (7), pp 690–694, DOI: 10.1021/es60130a005.

A comparison of weekend-weekday ozone and hydrocarbon concentrations in the Baltimore-Washington metropolitan area – Lebron (1975) “A “smog index”, related to dosage (ppm-h) of ozone, was derived. Indices were calculated using data from the Baltimore-Washington metropolitan area for the months of June–September of 1972 and 1973. On the average, weekends had higher indices than weekdays, although this difference may not be statistically significant. Further analysis of the data indicates that 06:00–09:00 h average concentrations of non-methane hydrocarbons are significantly higher during weekdays than during weekends and no relationship exists between these morning hydrocarbon levels and the afternoon peak ozone concentration. These results place some doubt on the effectiveness of early morning hydrocarbon emission control alone in an abatement program for photochemical oxidants.” Felipe Lebron, Atmospheric Environment, Volume 9, Issue 9, September 1975, Pages 861-863, doi:10.1016/0004-6981(75)90046-3.

Sunday and Workday Variations in Photochemical Air Pollutants in New Jersey and New York – Cleveland et al. (1974) “Concentration distributions of air contaminants and meteorological variables in New Jersey and New York for workdays (Mondays through Fridays, omitting holidays) and Sundays are compared by means of quantile-quantile plots. The ozone distributions are slightly higher on Sundays, and the primary pollutant distributions are lower. These results raise serious questions about the validity of current concepts underlying ozone reduction in urban atmospheres.” W. S. Cleveland, T. E. Graedel, B. Kleiner and J. L. Warner, Science 13 December 1974, Vol. 186 no. 4168 pp. 1037-1038, DOI: 10.1126/science.186.4168.1037.

Note on the effect of the weekly cycle of air pollution on solar radiation at Toronto – Mateer (1961) Int J Air Water Pollut. 1961 Jun;4:52-4.

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Papers on lake effect and climate

Posted by Ari Jokimäki on December 10, 2010

This is a list of papers on the lake effect and how climate affects it. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

A New Look at Lake-Effect Snowfall Trends in the Laurentian Great Lakes Using a Temporally Homogeneous Data Set – Kunkel et al. (2009) “Snowfall data are subject to quality issues that affect their usefulness for detection of climate trends. A new analysis of lake-effect snowfall trends utilizes a restricted set of stations identified as suitable for trends analysis based on a careful quality assessment of long-term observation stations in the lake-effect snowbelts of the Laurentian Great Lakes. An upward trend in snowfall was found in two (Superior and Michigan) of the four snowbelt areas. The trends for Lakes Erie and Ontario depended on the period of analysis. Although these results are qualitatively similar to outcomes of other recent studies, the magnitude of the upward trend is about half as large as trends in previous findings. The upward trend in snowfall was accompanied by an upward trend in liquid water equivalent for Superior and Michigan, while no trend was observed for Erie and Ontario. Air temperature has also trended upward for Superior and Michigan, suggesting that warmer surface waters and less ice cover are contributing to the upward snowfall trends by enhancing lake heat and moisture fluxes during cold air outbreaks. However, a more comprehensive study is needed to definitely determine cause and effect. Overall, this study finds that trends in lake-effect snowfall are not as large as was believed based on prior research.” Kenneth E. Kunkel, Leslie Ensor, Michael Palecki, David Easterling, David Robinson, Kenneth G. Hubbard, Kelly Redmond, Journal of Great Lakes Research 35(1):23-29. 2009, doi: 10.1016/j.jglr.2008.11.003. [Full text]

Climatology of Lake-Effect Precipitation Events over Lake Champlain – Laird et al. (2009) “This study provides the first long-term climatological analysis of lake-effect precipitation events that developed in relation to a small lake (having a surface area of ≤1500 km2). The frequency and environmental conditions favorable for Lake Champlain lake-effect precipitation were examined for the nine winters (October–March) from 1997/98 through 2005/06. Weather Surveillance Radar-1988 Doppler (WSR-88D) data from Burlington, Vermont, were used to identify 67 lake-effect events. Events occurred as 1) well-defined, isolated lake-effect bands over and downwind of the lake, independent of larger-scale precipitating systems (LC events), 2) quasi-stationary lake-effect bands over the lake embedded within extensive regional precipitation from a synoptic weather system (SYNOP events), or 3) a transition from SYNOP and LC lake-effect precipitation. The LC events were found to occur under either a northerly or a southerly wind regime. An examination of the characteristics of these lake-effect events provides several unique findings that are useful for comparison with known lake-effect environments for larger lakes. January was the most active month with an average of nearly four lake-effect events per winter, and approximately one of every four LC events occurred with southerly winds. Event initiation and dissipation occurred on a diurnal time scale with an average duration of 12.1 h. In general, Lake Champlain lake-effect events 1) typically yielded snowfall, with surface air temperatures rarely above 0°C, 2) frequently had an overlake mesolow present with a sea level pressure departure of 3–5 hPa, 3) occurred in a very stable environment with a surface inversion frequently present outside the Lake Champlain Valley, and 4) averaged a surface lake–air temperature difference of 14.4°C and a lake–850-hPa temperature difference of 18.2°C. Lake Champlain lake-effect events occur within a limited range of wind and temperature conditions, thus providing events that are more sensitive to small changes in environmental conditions than are large-lake lake-effect events and offering a more responsive system for subsequent investigation of connections between mesoscale processes and climate variability.” Laird, Neil F., Jared Desrochers, Melissa Payer, 2009, J. Appl. Meteor. Climatol., 48, 232–250, doi: 10.1175/2008JAMC1923.1. [Full text]

Climate teleconnections related to El Niño winters in a lake-effect region of west-central New York – Grimaldi (2008) “A 64-year climatological record for the cold season in Syracuse, New York is analyzed for temperature and snowfall. Evidence suggests that El Niño winters are characterized by warmer temperatures and below normal snowfall during the first month of winter followed by colder temperatures and above normal snowfall for the second month of winter. Major snow events were more than five times more likely to occur for El Niño winters compared to climatology. It is suggested that the greater frequency of heavy snowfalls is related to both favorable dynamics and warmer lake/ocean temperatures which follow the mild early winter period.” Richard Grimaldi, Atmospheric Science Letters, Volume 9, Issue 1, pages 18–25, January/March 2008, DOI: 10.1002/asl.166. [Full text]

Hydroclimatic Analysis of Snowfall Trends Associated with the North American Great Lakes – Ellis & Johnson (2004) “Research over the past several decades has indicated that snowfall has increased dramatically over portions of the past century across those areas of the Great Lakes region of North America that are subject to lake-effect snowfall. Within this study, time series of annual midwinter snowfall within lake-effect areas show evidence of a clear increase in both snowfall and snowfall frequency through a 40-yr period beginning in the early 1930s and ending in the early 1970s. The goal of the work presented here is to determine to what extent the apparent increases in lake-effect snowfall actually modified the winter hydroclimate of the areas. Simple hydroclimatic analysis of midwinter precipitation to the lee of Lakes Erie and Ontario for the period of significant snowfall increases suggests that the changes were a product of 1) a shift toward more precipitation events that were snowfall rather than rainfall, 2) an associated decrease in midwinter rainfall, 3) an increase in the intensity of individual snowfall events, and 4) an increase in the snowfall/snow water equivalence ratio. The balance was a small increase in total precipitation confined to areas in close proximity to the lakes across northeastern Ohio and western New York, while areas outside the regions generally experienced an overall decrease in midwinter precipitation. While the cause(s) of the snowfall trends remains elusive, the results of the work presented here suggest that no great long-term regional change occurred in the true wintertime seasonal hydroclimate of the lake-effect areas. Rather, much of the touted snowfall increase simply came at the expense of rainfall events to produce only small changes in total precipitation over the time period of significant snowfall increase.” Ellis, Andrew W., Jennifer J. Johnson, 2004, J. Hydrometeor, 5, 471–486. [Full text]

Increasing Great Lake–Effect Snowfall during the Twentieth Century: A Regional Response to Global Warming? – Burnett et al. (2003) “The influence of the Laurentian Great Lakes on the climate of surrounding regions is significant, especially in leeward settings where lake-effect snowfall occurs. Heavy lake-effect snow represents a potential natural hazard and plays important roles in winter recreational activities, agriculture, and regional hydrology. Changes in lake-effect snowfall may represent a regional-scale manifestation of hemispheric-scale climate change, such as that associated with global warming. This study examines records of snowfall from several lake-effect and non-lake-effect sites throughout most of the twentieth century in order to 1) determine whether differences in snowfall trends exist between these settings and 2) offer possible linkages between lake-effect snow trends and records of air temperature, water temperature, and ice cover. A new, historic record of oxygen isotope [δ18O(CaCO3)] data from the sediments of three eastern Finger Lakes in central New York is presented as a means of independently assessing changes in Great Lakes lake-effect snowfall. Results reveal a statistically significant increasing trend in snowfall for the lake-effect sites, whereas no trend is observed in the non-lake-effect settings. The Finger Lake oxygen isotope record reflects this increase in lake-effect snow through a statistically significant trend toward lower δ18O(CaCO3) values. Records of air temperature, water temperature, and lake ice suggest that the observed lake-effect snow increase during the twentieth century may be the result of warmer Great Lakes surface waters and decreased ice cover, both of which are consistent with the historic upward trend in Northern Hemispheric temperature due to global warming. Given projected increases in future global temperature, areas downwind of the Great Lakes may experience increased lake-effect snowfall for the foreseeable future.” Burnett, Adam W., Matthew E. Kirby, Henry T. Mullins, William P. Patterson, 2003, J. Climate, 16, 3535–3542. [Full text]

Assessment of Potential Effects of Climate Change on Heavy Lake-Effect Snowstorms Near Lake Erie – Kunkel et al. (2002) “The potential effects of future climate change on the frequency of heavy lake-effect snowstorms in the Lake Erie snowbelt were assessed using recent transient simulations from two General Circulation Models (GCMs): the second-generation Hadley Centre (HadCM2) and the first generation Canadian Climate Centre (CGCM1) coupled ocean-atmosphere models. An analysis of historical heavy lake-effect snowstorms identified six weather conditions to be closely related to heavy lake-effect snowstorm occurrence: surface wind speed > 6 m/s, surface wind direction of south southwest to west northwest, surface air temperature in the range of −10°C to 0°C, lake surface to air temperature difference > 7°C, lower tropospheric stability (Tlake − 850 >15°C), and a highly amplified middle tropospheric wave train. These criteria were applied to daily grid point data from the GCMs for two periods, the late 20th Century and the late 21st Century, to determine the relative frequency with which heavy lake-effect conditions were predicted. Surface conditions favorable for heavy lake-effect snow decreased in frequency by 50% and 90% for the HadCM2 and CGCM1, respectively, by the late 21st Century. This reduction was due almost entirely to a decrease in the number of occurrences of surface air temperature in the range of −10 to 0°C, which in turn was the result of an increase in average winter air temperatures. Other surface conditions favorable for lake-effect snow occurred at about the same frequency in the late 21st Century as in the late 20th Century, suggesting that lake-effect rain events may replace lake-effect snow events. Changes in the middle tropospheric wave train were also noted in both models. However, there were sizable biases in the simulation of the present-day climate, raising questions about the validity of the future projections.” Kenneth E. Kunkel, Nancy E. Westcott and David A.R. Kristovich, Journal of Great Lakes Research, Volume 28, Issue 4, 2002, Pages 521-536, doi:10.1016/S0380-1330(02)70603-5.

Synoptic mechanisms associated with snowfall increases to the lee of Lakes Erie and Ontario – Leathers & Ellis (1996) “Snowfall is a cyrospheric variable that impacts nearly every sector of society. Because of its societal importance, snowfall is a logical variable to be used as an indicator of potential global environmental change. This study investigates the mechanisms responsible for large observed snowfall increases across the eastern Great Lakes region of the USA. Results indicate that mean snowfall amounts across sections of western New York and north-western Pennsylvania have increased by up to 100 cm over the 60-year period encompassing the snowfall seasons 1930–1931 through to 1989–1990. A synoptic climatological approach is utilized to identify consistent synoptic-scale atmospheric patterns responsible for snowfall across the region. Nine synoptic types are identified as producing significan t snowfall in the study area; five with synoptic characteristics indicative of lake-effect snowfall and four evidencing characteristics of snowfall associated with cyclonic influence. An examination of the seasonal frequency of the nine synoptic types indicates a substantial increase in the frequency of the five lake-effect synoptic types and a long-term decrease in the numbers of cyclone synoptic types over the period 1950–1951 through to 1981–1982. Information concerning trends in the frequency and the intensity of each of the nine snowfall-producing synoptic types was combined to produce a modelled snowfall change due to frequency and intensity variations over the period. Trends in the frequency and intensity of the synoptic patterns associated with lake- effect snowfall explain the majority of the observed snowfall increase across the region. Variations in the synoptic types associated with cyclonically induced snowfall are shown to be unimportant to snowfall changes across the eastern Great Lakes area. Possible reasons for increases in the frequency and the intensity of the lake-effect synoptic types are discussed.” Daniel J. Leathers, Andrew W. Ellis, International Journal of Climatology, Volume 16, Issue 10, pages 1117–1135, October 1996, DOI: 10.1002/(SICI)1097-0088(199610)16:103.0.CO;2-4.

Temporal characteristics of USA snowfall 1945–1946 through to 1984–1985 – Leathers et al. (1993) “The temporal variability of USA snowfall is investigated for the period 1945–1946 through to 1984–1985 using linear trend and principal components analyses. The results of the linear trend analysis indicate that two regions of the USA evidence significant changes in monthly snowfall over the period. These areas include the Great Lakes/upper mid-west and high plains regions of the USA. In the Great Lakes/upper mid-west sector, positive linear trends are found in monthly snowfall totals for the mid-winter months (December, January, February). For the high plains region, positive linear trends are found for the month of December. Principal components analysis (PCA) is used with seasonal snowfall data in order to better understand the spatial and temporal nature of seasonal snowfall variations across the USA. The PCA isolates six spatially coherent regions in which seasonal snowfall varied similarly over the 40-year period. Only one of these regions, centred on the Great Lakes and upper mid-west, displays any long-term change in seasonal snowfall, a positive trend during the period 1945–1946 through to 1984–1985. These results are discussed in the context of man-induced and natural environmental changes.” Daniel J. Leathers, Thomas L. Mote, Karl C. Kuivinen, Stuart McFeeters, Douglas R. Kluck, International Journal of Climatology, Volume 13, Issue 1, pages 65–76, January/February 1993, DOI: 10.1002/joc.3370130105.

Spatiotemporal Trends in Lake Effect and Continental Snowfall in the Laurentian Great Lakes, 1951–1980 – Norton & Bolsenga (1993) “A new raster-based monthly snowfall climatology was derived from 1951–1980 snowfall station data for the Laurentian Great Lakes. An automated methodology was used to obtain higher spatial resolution than previously obtained. The increase in resolution was attained by using all available monthly snowfall data from over 1230 stations per year combined with a monthly lime step to produce high-resolution grids. These monthly grids were combined to produce snow-year grids. Multiyear average grids were created and compared. This technique minimizes traditional problems associated with missing data and variable length station records. The three 10-year average distribution maps presented here indicate a period of increasing snowfall. Windowing of the 30 seasonal grids revealed that increasing snowfall was attributable to an increase in lake effect snowfall and not to continental snowfall. The Great Lakes drainage basin was evaluated for trends within and between monthly and seasonal average snowfall through windowing of all 240 monthly grids. The graphical and statistical evaluation of these trends indicates a strong natural variation in the region’s snowfall and reveals an increasing trend during the study period.” Norton, D. C., S. J. Bolsenga, 1993, J. Climate, 6, 1943–1956. [Full text]

Numerical Study of the Influence of Environmental Conditions on Lake-Effect Snowstorms over Lake Michigan – Hjelmfelt (1990) “Numerical simulations are used to examine the influence of environmental parameters on the morphology of lake effect snowstorms over Lake Michigan. A series of model sensitivity studies are performed using the Colorado State University mesoscale model to examine the effects of lake–land temperature difference, surface roughness, atmospheric boundary layer stability, humidity, and wind speed and direction on the morphology of simulated storms. Four morphological types of lake effect snowstorms have been identified: (i) Broad area coverage, which may become organized into wind parallel bands or cellular convection; (ii) shoreline bands with a line of convection roughly parallel to the lee shore and a well developed land breeze on the lee shore; (iii) midlake band with low-level convergence centered over the lake; and (iv) mesoscale vortices with a well-developed cyclonic flow pattern in the boundary layer. The model is able to reproduce all four morphological types. Simulations varying environmental parameters independently define the thermodynamic and wind conditions for the occurrence of each morphological type. In particular, the limiting conditions of lake–land temperature difference, upwind wind speed stability, and humidity for development of a land breeze on the east side of Lake Michigan are defined for lake snow conditions. The effects of wind direction, surface roughness, and latent heat release are also described.” Hjelmfelt, Mark R., 1990, Mon. Wea. Rev., 118, 138–150. [Full text]

Quantitative Estimates of the Effect of Lake Michigan on Snowfall – Braham & Dungey (1984) “A climatological study of snowfall in the snowbelts of Michigan shows that decade-average amounts varied by a factor of 2 during the period from 1909/10 through 1980/81. The effect of Lake Michigan on total winter snowfall along its shores has been estimated. A long-term average effect of +10% is found for the Wisconsin shore south of Sheboygan, and an average of +60% for the Michigan shore, south of Hart, with a minimum effect in the 1930s and a maximum in the 1960s.” Braham, Roscoe R., Maureen J. Dungey, 1984, J. Climate Appl. Meteor., 23, 940–949. [Full text]

Lake Effect Snowfall to the Lee of the Great Lakes: Its Role in Michigan – Eichenlaub (1970) “Lake effect snowfalls contribute a significant proportion of the total winter snowfall in areas to the lee of the Great Lakes. In Michigan during the seasons 1957–58 through 1961–62 at least 30% of the seasonal snowfall in lee areas was derived from lake-atmosphere interactions. Evidence suggests that lake effect snowfall has significantly increased during the past several decades, particularly in southwestern Michigan and northern Indiana. While the observed changes cannot be definitely ascribed to any single factor, it seems likely that a general cooling of winter temperatures may be partially responsible for this climatic change.” Eichenlaub, Val L., 1970, Bull. Amer. Meteor. Soc., 51, 403–412. [Full text]

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Papers on diurnal temperature range

Posted by Ari Jokimäki on November 24, 2010

This is a list of papers on the diurnal temperature range (daily maximum and minimum temperatures), both global and regional papers are included. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Associations of diurnal temperature range change with the leading climate variability modes during the Northern Hemisphere wintertime and their implication on the detection of regional climate trends – Wu (2010) “This study examines associations of diurnal temperature range (DTR) changes in observations at the global, hemispheric, subcontinental, and grid box scales with five leading climate variability modes, including the Arctic Oscillation (AO), hemispheric Pacific–North America (PNA)–like mode, Pacific Decadal Oscillation, El Niño Southern Oscillation (ENSO), and Antarctic Oscillation (AAO) during the Northern Hemisphere winter season (Jan–Mar). Winter DTR variability in most subcontinental regions is significantly related to variations in either the AO, or hemispheric PNA-like mode, or ENSO index in the Northern Hemisphere. In the Southern Hemisphere, the DTR variability appears closely coupled with variations in the ENSO and AAO. From 1951 to 2000, variations in the circulation patterns account for a significant fraction of the DTR increase at all scales although the strength of these associations varies geographically. After removing the linearly congruent component of leading climate variability modes from the total wintertime DTR trends in the observations, statistically significant residual trends in DTR are still found at the global, hemispheric, and most subcontinental regions. Ensemble mean multimodel averaged DTR trends to major anthropogenic and natural forcing are significantly smaller than not only observed total DTR trends but also residual trends at these large scales. The implication of changes in the leading climate variability modes on the detection of regional DTR trends is discussed. We find that the detection of the regional response to combined anthropogenic and natural forcing is robust to the exclusion of trends related to changes of the five modes considered here.” Wu, Q. (2010), J. Geophys. Res., 115, D19101, doi:10.1029/2010JD014026.

Detection and attribution of anthropogenic forcing to diurnal temperature range changes from 1950 to 1999: comparing multi-model simulations with observations – Zhou et al. (2009) “Observations show that the surface diurnal temperature range (DTR) has decreased since 1950s over most global land areas due to a smaller warming in maximum temperatures (T max) than in minimum temperatures (T min). This paper analyzes the trends and variability in T max, T min, and DTR over land in observations and 48 simulations from 12 global coupled atmosphere-ocean general circulation models for the later half of the 20th century. It uses the modeled changes in surface downward solar and longwave radiation to interpret the modeled temperature changes. When anthropogenic and natural forcings are included, the models generally reproduce observed major features of the warming of T max and T min and the reduction of DTR. As expected the greenhouse gases enhanced surface downward longwave radiation (DLW) explains most of the warming of T max and T min while decreased surface downward shortwave radiation (DSW) due to increasing aerosols and water vapor contributes most to the decreases in DTR in the models. When only natural forcings are used, none of the observed trends are simulated. The simulated DTR decreases are much smaller than the observed (mainly due to the small simulated T min trend) but still outside the range of natural internal variability estimated from the models. The much larger observed decrease in DTR suggests the possibility of additional regional effects of anthropogenic forcing that the models can not realistically simulate, likely connected to changes in cloud cover, precipitation, and soil moisture. The small magnitude of the simulated DTR trends may be attributed to the lack of an increasing trend in cloud cover and deficiencies in charactering aerosols and important surface and boundary-layer processes in the models.” Liming Zhou, Robert E. Dickinson, Aiguo Dai and Paul Dirmeyer, Climate Dynamics, Volume 35, Numbers 7-8, 1289-1307, DOI: 10.1007/s00382-009-0644-2. [Full text]

Diurnal temperature range over Europe between 1950 and 2005 – Makowski et al. (2008) “It has been widely accepted that diurnal temperature range (DTR) decreased on a global scale during the second half of the twentieth century. Here we show however, that the long-term trend of annual DTR has reversed from a decrease to an increase during the 1970s in Western Europe and during the 1980s in Eastern Europe. The analysis is based on the high-quality dataset of the European Climate Assessment and Dataset Project, from which we selected approximately 200 stations covering the area bordered by Iceland, Algeria, Turkey and Russia for the period 1950 to 2005. We investigate national and regional annual means as well as the pan-European mean with respect to trends and reversal periods. 17 of the 24 investigated regions including the pan-European mean show a statistical significant increase of DTR since 1990 at the latest. Of the remaining 7 regions, two show a non-significant increase, three a significant decrease and two no significant trend. Changes in DTR are affected by both surface shortwave and longwave radiation, the former of which has undergone a change from dimming to brightening in the period considered. Consequently, we discuss the connections between DTR, shortwave radiation and sulfur emissions which are thought to be amongst the most important factors influencing the incoming solar radiation through the primary and secondary aerosol effect. We find reasonable agreement between trends in SO2 emissions, radiation and DTR in areas affected by high pollution. Consequently, we conclude that the trends in DTR could be mostly determined by changes in emissions and the associated changes in incoming solar radiation.” Makowski, K., Wild, M., and Ohmura, A., Atmos. Chem. Phys., 8, 6483-6498, doi:10.5194/acp-8-6483-2008, 2008. [Full text]

Impact of global dimming and brightening on global warming – Wild et al. (2007) “Speculations on the impact of variations in surface solar radiation on global warming range from concerns that solar dimming has largely masked the full magnitude of greenhouse warming, to claims that the recent reversal from solar dimming to brightening rather than the greenhouse effect was responsible for the observed warming. To disentangle surface solar and greenhouse influences on global warming, trends in diurnal temperature range are analyzed. They suggest that solar dimming was effective in masking greenhouse warming, but only up to the 1980s, when dimming gradually transformed into brightening. Since then, the uncovered greenhouse effect has revealed its full dimension, as manifested in a rapid temperature rise (+0.38°C/decade over land since mid-1980s). Recent solar brightening cannot supersede the greenhouse effect as main cause of global warming, since land temperatures increased by 0.8°C from 1960 to 2000, even though solar brightening did not fully outweigh solar dimming within this period.” Wild, M., A. Ohmura, and K. Makowski (2007), Geophys. Res. Lett., 34, L04702, doi:10.1029/2006GL028031. [Full text]

Maximum and minimum temperature trends for the globe: An update through 2004 – Vose et al. (2005) “New data acquisitions are used to examine recent global trends in maximum temperature, minimum temperature, and the diurnal temperature range (DTR). On average, the analysis covers the equivalent of 71% of the total global land area, 17% more than in previous studies. Consistent with the IPCC Third Assessment Report, minimum temperature increased more rapidly than maximum temperature (0.204 vs. 0.141°C dec−1) from 1950–2004, resulting in a significant DTR decrease (−0.066°C dec−1). In contrast, there were comparable increases in minimum and maximum temperature (0.295 vs. 0.287°C dec−1) from 1979–2004, muting recent DTR trends (−0.001°C dec−1). Minimum and maximum temperature increased in almost all parts of the globe during both periods, whereas a widespread decrease in the DTR was only evident from 1950–1980.” Vose, R. S., D. R. Easterling, and B. Gleason (2005), Maximum and minimum temperature trends for the globe: An update through 2004, Geophys. Res. Lett., 32, L23822, doi:10.1029/2005GL024379. [Short version of the article]

Diurnal temperature range as an index of global climate change during the twentieth century – Braganza et al. (2004) “The usefulness of global-average diurnal temperature range (DTR) as an index of climate change and variability is evaluated using observations and climate model simulations representing unforced climate variability and anthropogenic climate change. On decadal timescales, modelled and observed intrinsic variability of DTR compare well and are independent of variations in global mean temperature. Observed reductions in DTR over the last century are large and unlikely to be due to natural variability alone. Comparison of observed and anthropogenic-forced model changes in DTR over the last 50 years show much less reduction in DTR in the model simulations due to greater warming of maximum temperatures in the models than observed. This difference is likely attributed to increases in cloud cover that are observed over the same period and are absent in model simulations.” Braganza, K., D. J. Karoly, and J. M. Arblaster (2004), Geophys. Res. Lett., 31, L13217, doi:10.1029/2004GL019998. [Full text]

Daily maximum and minimum temperature trends in a climate model – Stone & Weaver (2003) “The recent observed global warming trend over land has been characterised by a faster warming at night, leading to a considerable decrease in the diurnal temperature range (DTR). Analysis of simulations of a climate model including observed increases in greenhouse gases and sulphate aerosols reveals a similar trend in the DTR of −0.2°C per century, albeit of smaller magnitude than the observed −0.8°C per century. This trend in the model simulations is related to changes in cloud cover and soil moisture. These results indicate that the observed decrease in the DTR could be a signal of anthropogenic forcing of recent climate change.” Stone, D. A., and A. J. Weaver (2002), Geophys. Res. Lett., 29(9), 1356, doi:10.1029/2001GL014556. [Full text]

Effects of Clouds, Soil Moisture, Precipitation, and Water Vapor on Diurnal Temperature Range – Dai et al. (1999) “The diurnal range of surface air temperature (DTR) has decreased worldwide during the last 4–5 decades and changes in cloud cover are often cited as one of the likely causes. To determine how clouds and moisture affect DTR physically on daily bases, the authors analyze the 30-min averaged data of surface meteorological variables and energy fluxes from the the First International Satellite Land Surface Climatology Project Field Experiment and the synoptic weather reports of 1980–1991 from about 6500 stations worldwide. The statistical relationships are also examined more thoroughly in the historical monthly records of DTR, cloud cover, precipitation, and streamflow of this century. It is found that clouds, combined with secondary damping effects from soil moisture and precipitation, can reduce DTR by 25%–50% compared with clear-sky days over most land areas; while atmospheric water vapor increases both nighttime and daytime temperatures and has small effects on DTR. Clouds, which largely determine the geographic patterns of DTR, greatly reduce DTR by sharply decreasing surface solar radiation while soil moisture decreases DTR by increasing daytime surface evaporative cooling. Clouds with low bases are most efficient in reducing the daytime maximum temperature and DTR mainly because they are very effective in reflecting the sunlight, while middle and high clouds have only moderate damping effects on DTR. The DTR reduction by clouds is largest in warm and dry seasons such as autumn over northern midlatitudes when latent heat release is limited by the soil moisture content. The net effects of clouds on the nighttime minimum temperature is small except in the winter high latitudes where the greenhouse warming effect of clouds exceeds their solar cooling effect. The historical records of DTR of the twentieth century covary inversely with cloud cover and precipitation on interannual to multidecadal timescales over the United States, Australia, midlatitude Canada, and former U.S.S.R., and up to 80% of the DTR variance can be explained by the cloud and precipitation records. Given the strong damping effect of clouds on the daytime maximum temperature and DTR, the well-established worldwide asymmetric trends of the daytime and nighttime temperatures and the DTR decreases during the last 4–5 decades are consistent with the reported increasing trends in cloud cover and precipitation over many land areas and support the notion that the hydrologic cycle has intensified.” Dai, Aiguo, Kevin E. Trenberth, Thomas R. Karl, 1999: Effects of Clouds, Soil Moisture, Precipitation, and Water Vapor on Diurnal Temperature Range. J. Climate, 12, 2451–2473, doi: 10.1175/1520-0442(1999)0122.0.CO;2. [Full text]

Maximum and Minimum Temperature Trends for the Globe – Easterling et al. (1997) “Analysis of the global mean surface air temperature has shown that its increase is due, at least in part, to differential changes in daily maximum and minimum temperatures, resulting in a narrowing of the diurnal temperature range (DTR). The analysis, using station metadata and improved areal coverage for much of the Southern Hemisphere landmass, indicates that the DTR is continuing to decrease in most parts of the world, that urban effects on globally and hemispherically averaged time series are negligible, and that circulation variations in parts of the Northern Hemisphere appear to be related to the DTR. Atmospheric aerosol loading in the Southern Hemisphere is much less than that in the Northern Hemisphere, suggesting that there are likely a number of factors, such as increases in cloudiness, contributing to the decreases in DTR.” David R. Easterling, Briony Horton, Philip D. Jones, Thomas C. Peterson, Thomas R. Karl, David E. Parker, M. James Salinger, Vyacheslav Razuvayev, Neil Plummer, Paul Jamason and Christopher K. Folland, Science 18 July 1997, Vol. 277 no. 5324 pp. 364-367, DOI: 10.1126/science.277.5324.364. [Full text]

The Influence of Land Use/Land Cover on Climatological Values of the Diurnal Temperature Range – Gallo et al. (1996) “The diurnal temperature range (DTR) at weather observation stations that make up the U.S. Historical Climatology Network was evaluated with respect to the predominant land use/land cover associated with the stations within three radii intervals (100, 1000, and 10 000 m) of the stations. Those stations that were associated with predominantly rural land use/land cover (LULC) usually displayed the greatest observed DTR, whereas those associated with urban related land use or land cover displayed the least observed DTR. The results of this study suggest that significant differences in the climatological DTR were observed and could be attributed to the predominant LULC associated with the observation stations. The results also suggest that changes in the predominant LULC conditions, within as great as a 10 000 m radius of an observation station, could significantly influence the climatological DTR. Future changes in the predominant LULC associated with observation sites should be monitored similar to the current practice of monitoring changes in instruments or time of observation at the observations sites.” Gallo, Kevin P., David R. Easterling, Thomas C. Peterson, 1996, J. Climate, 9, 2941–2944. [Full text]

Southwest Pacific temperatures: trends in maximum and minimum temperatures – Salinger (1995) “Diurnal temperature trends are described for newly homogenised climate data sets for a large area of the South Pacific. The diurnal trends differ from those documented for Northern Hemisphere land areas, where decreases are observed in the diurnal temperature range as a result of increases principally in minimum temperature. The Southwest Pacific divides into four regions that share coherent diurnal temperature trends over the past five decades. Two regions southwest of the South Pacific Convergence Zone (SPCZ) display steady warming in mean temperature. The other two regions, located northeast of the SPCZ, cooled in the 1970’s and warmed in the 1980’s. The warming in three of the four regions can be attributed to increases in both mean daily maximum (mostly daytime) and mean daily minimum (mostly night time) temperature, with little change in the diurnal temperature range. In New Zealand, modification of the regional temperature trend occurs as atmospheric circulation interacts with the high orography, producing different local behaviour in trends of maximum and minimum temperature and diurnal temperature range. The present results come from sites where there can be no question of any urban influence. Most of the Southwest Pacific sites provide a very good climate monitoring platform for the surrounding oceans because of their island location.” M. J. Salinger, Atmospheric Research, Volume 37, Issues 1-3, July 1995, Pages 87-99, doi:10.1016/0169-8095(94)00071-K. [Full text]

Recent variations in mean temperature and the diurnal temperature range in the Antarctic – Jones (1995) “Monthly mean surface temperature data are available from nearly twenty stations for the period since the International Geophysical Year 1957. All but three stations show an increase in mean temperatures over this time, amounting in the average to 0.57°C over 1957 to 1994. All of this warming occurred before the early 1970s. Since then, there has been no change. The warming has been greatest in the Antarctic Peninsula. Analyses of the less‐widely available diurnal temperature range (DTR) (maximum‐minimum) data show regions of increase and decrease over Antarctica. An average continental DTR series shows no trend over 1957 to 1992. Analyses for six mid‐to‐high latitude Southern Ocean islands show increases in mean temperature over 1961–90. Given the low year‐to‐year variability in these data, these trends are more significant than for any of the stations on the Antarctic continent. The marked decrease in mean temperatures over Antarctica during 1993 and 1994 seems unrelated to sea‐ice variations which show little change since the early 1980s.” Jones, P. D. (1995), Geophys. Res. Lett., 22(11), 1345–1348, doi:10.1029/95GL01198.

Asymmetric diurnal temperature change in the Alpine Region – Weber et al. (1994) “By now there is general agreement that the annual mean temperature of earth’s surface has increased during the last century. Recently, it has become obvious that this warming is quite inhomogeneous in various respects. Besides the spatial and seasonal variability of the temperature trend a diurnal asymmetry of increase has been observed. In large continental regions the annual mean of the daily minimum temperature has increased noticeably faster than the annual mean of the daily maximum. The same behaviour is found in the present study for low‐lying stations in Central Europe. However, data from mountain top stations show a similar increase for both minimum and maximum of daily temperatures. No diurnal asymmetry was observed for these stations. The good agreement of the time series from different mountain stations leads us to believe that the observed trends of minimum and maximum temperature are not caused by particular local influences or observation errors. An analysis of monthly and seasonal means shows that most of the warming took place in fall.” Weber, R. O., P. Talkner, and G. Stefanicki (1994), Geophys. Res. Lett., 21(8), 673–676, doi:10.1029/94GL00774. [Full text]

Nighttime warming and the greenhouse effect – Kukla & Karl (1993) No abstract.

A New Perspective on Recent Global Warming: Asymmetric Trends of Daily Maximum and Minimum Temperature – Karl et al. (1993) “Monthly mean maximum and minimum temperatures for over 50% (10%) of the Northern (Southern) Hemisphere landmass, accounting for 37% of the global landmass, indicate that the rise of the minimum temperature has occurred at a rate three times that of the maximum temperature during the period 1951–90 (0.84°C versus 0.28°C). The decrease of the diurnal temperature range is approximately equal to the increase of mean temperature. The asymmetry is detectable in all seasons and in most of the regions studied. The decrease in the daily temperature range is partially related to increases in cloud cover. Furthermore, a large number of atmospheric and surface boundary conditions are shown to differentially affect the maximum and minimum temperature. Linkages of the observed changes in the diurnal temperature range to large-scale climate forcings, such as anthropogenic increases in sulfate aerosols, greenhouse gases, or biomass burning (smoke), remain tentative. Nonetheless, the observed decrease of the diurnal temperature range is clearly important, both scientifically and practically.” Karl, Thomas R., and Coauthors, 1993, Bull. Amer. Meteor. Soc., 74, 1007–1023. [Full text]

Southwest Pacific temperatures: Diurnal and seasonal trends – Salinger et al. (1993) “Temperature trends are presented for a large part of the southwest Pacific. The trends differ from those documented for Northern Hemisphere land areas, where warming has occurred mainly through increases in minimum temperature. The New Zealand patterns are derived from recently completed analyses of monthly and annual mean maximum and minimum surface temperature records for a newly homogenised historical climate data series for New Zealand and outlying islands. They indicate that the warming in the New Zealand region over the past five decades can be attributed to increases in both mean maximum (mostly daytime) and mean minimum (mostly night time) temperature. All seasons show a temperature increase, with the largest occurring in summer (DJF). Northern Hemisphere evidence suggests that changes in cloud cover and the presence of sulfate aerosols plays a direct role. The present results imply that, while the observed warming in a large portion of the Northern Hemisphere landmass may be significantly affected by both these factors, sulfate aerosol effects may be less important in the Southern Hemisphere.” Salinger, M. J., J. Hay, R. McGann, and B. Fitzharris (1993), Geophys. Res. Lett., 20(10), 935–938, doi:10.1029/93GL01113.

Global warming: Evidence for asymmetric diurnal temperature change – Karl et al. (1990) “Analyses of the year‐month mean maximum and minimum surface thermometric record have now been updated and expanded to cover three large countries in the Northern Hemisphere (the contiguous United States, the Soviet Union, and the People’s Republic of China). They indicate that most of the warming which has occurred in these regions over the past four decades can be attributed to an increase of mean minimum (mostly nighttime) temperatures. Mean maximum (mostly daytime) temperatures display little or no warming. In the USA and the USSR (no access to data in China) similar characteristics are also reflected in the changes of extreme seasonal temperatures, e.g., increase of extreme minimum temperatures and little or no change in extreme maximum temperatures. The continuation of increasing minimum temperatures and little overall change of the maximum leads to a decrease of the mean (and extreme) temperature range, an important measure of climate variability. The cause(s) of the asymmetric diurnal changes are uncertain, but there is some evidence to suggest that changes in cloud cover plays a direct role (where increases in cloudiness result in reduced maximum and higher minimum temperatures). Regardless of the exact cause(s), these results imply that either: (1) climate model projections considering the expected change in the diurnal temperature range with increased levels of the greenhouse gases are underestimating (overestimating) the rise of the daily minimum (maximum) relative to the maximum (minimum), or (2) the observed warming in a considerable portion of the Northern Hemisphere landmass is significantly affected by factors unrelated to an enhanced anthropogenically‐induced greenhouse effect.” Karl, T. R., G. Kukla, V. N. Razuvayev, M. J. Changery, R. G. Quayle, R. R. Heim Jr., D. R. Easterling, and C. B. Fu (1991), Geophys. Res. Lett., 18(12), 2253–2256, doi:10.1029/91GL02900.

Is Recent Climate Change Across the United States Related to Rising Levels of Anthropogenic Greenhouse Gases? – Plantico et al. (1990) “Global warming as a result of rising concentrations of anthropogenic greenhouse gases is predicted by current climate models. During the period 1948–1987, the concentration of anthropogenic greenhouse gases increased by more than 30%, and the mean annual temperature of the northern hemisphere increased by about 0.15°C. The mean annual temperature of the contiguous United States, however, does not show any significant trend. To gain a better understanding of why the United States’ temperature record does not reflect the anticipated greenhouse warming, we studied the inter-relationships between trends of temperature, cloudiness, sunshine and precipitation. Both the seasonal and annual trends for 23 geographic regions covering the United States were analyzed using Monte Carlo field significance tests. Several seasonal and regional differences were noted. While winters and autumns cooled, springs and summers warmed. Annually, cooling has occurred across the eastern half of the country, while warming dominates in the West. The largest changes in maximum temperature, daily temperature range, cloud amount, percent of possible sunshine and precipitation occur during autumn. Autumn also has the most significant correlations between trends. We found that the recent decrease of the maximum temperature and daily temperature range in autumn is statistically associated with increasing cloud amount and precipitation, and with decreasing sunshine. The widespread reduction in the temperature range is a result of decreased maximum and increased minimum temperatures. Cloud amount increased over most of the country during all seasons except spring. During spring the cloud amount remained fairly constant even though precipitation increased. Interestingly, no significant correlation was found between trends of mean temperature and cloud amount. Although several features of the recent climate change across the United States agree qualitatively with the model-predicted impact of increasing anthropogenic greenhouse gases, the regional and seasonal distribution of the observed trends do not appear in line with the model results. We conclude that either the recent changes of temperature, cloud amount, sunshine and precipitation over the United States are as yet unrelated to the increasing anthropogenic greenhouse gases, or that the transient response of regional climates to the greenhouse effect is not proportional to the modeled difference between the 1 × CO2 and 2 × CO2 equilibrium climates.” Plantico, M. S., T. R. Karl, G. Kukla, and J. Gavin (1990), J. Geophys. Res., 95(D10), 16,617–16,637, doi:10.1029/JD095iD10p16617.

Relationship between Decreased Temperature Range and Precipitation Trends in the United States and Canada, 1941–80 – Karl et al. (1986) “Previous work has shown significant decreases of the diurnal temperature range (1941–80) across a network of 130 stations in the United States and Canada. In the present study, changes in monthly total precipitation at these same stations were related to the decrease in temperature range using various Monte Carlo. These tests indicate that factors other than those related to precipitation contributed to the decrease of daily temperature range. Further study of the mechanisms responsible for the decreased temperature range is warranted, based on these results. The decreased range may be one of the few pieces of evidence available in North America that is consistent with potential impacts of increased greenhouse gases and/or anthropogenic aerosols.” Karl, Thomas R., George Kukla, Joyce Gavin, 1986, J. Climate Appl. Meteor., 25, 1878–1886. [Full text]

Decreasing Diurnal Temperature Range in the United States and Canada from 1941 through 1980 – Karl et al. (1984) “An appreciable number of nonurban stations in the United States and Canada have been identified with statistically significant (at the 90% level) decreasing trends in the monthly mean diurnal temperature range between 1941–80. The percentage of stations in the network showing the decrease is higher than expected due to chance throughout the year, with a maximum reached during late summer and early autumn and a minimum in December. Monte Carlo tests indicate that during five months the field significance of the decreasing range is above the 99% level, and in 12 months above the 95% level. There is a negligible probability that such a result is due to chance. In contrast, trends of increasing or decreasing monthly mean maximum or minimum temperatures have at most only two months with field significance at or above the 90% level. This is related to the tendency toward increasing temperature in the western portions of North America and decreasing temperature in the east. The physical mechanism responsible for the observed decrease in the diurnal range is not known. Possible explanations include greenhouse effects such as changes in cloudiness, aerosol loading, atmospheric water vapor content, or carbon dioxide. Change in circulation is also a possibility, but it will be difficult to isolate since the patterns of the decreased diurnal temperature range have high field significance throughout much of the year, relatively low spatial coherence, and occur at many stations where individual trends in the maximum and minimum temperature are not statistically significant. Our data show that the trends in the maximum and minimum temperatures may differ considerably from trends in the mean.” Karl, T. R., G. Kukla, J. Gavin, 1984, J. Climate Appl. Meteor., 23, 1489–1504. [Full text]

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Papers on pre-industrial anthropogenic climate forcing

Posted by Ari Jokimäki on October 26, 2010

This is a list of papers on the effect of pre-industrial mankind to the climate. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Contribution of anthropogenic land cover change emissions to preindustrial atmospheric CO2 – Reick et al. (2010) “Based on a recent reconstruction of anthropogenic land cover change (ALCC) we derive the associated CO2 emissions since 800 AD by two independent methods: a bookkeeping approach and a process model. The results are compared with the preindustrial development of atmospheric CO2 known from antarctic ice cores. Our results show that preindustrial CO2 emissions from ALCC have been relevant for the preindustrial carbon cycle, although before 1750 AD their trace in atmospheric CO2 is obscured by other processes of similar magnitude. After 1750 AD the situation is different: the steep increase in atmospheric CO2 until 1850 AD – this is before fossil-fuel emissions rose to significant values – is to a substantial part explained by growing emissions from ALCC.”

Biophysical feedbacks between the Pleistocene megafauna extinction and climate: The first human-induced global warming? – Doughty et al. (2010) “A large increase in Betula during a narrow 1000 year window, ∼13,800 years before present (YBP) in Alaska and Yukon corresponded in time with the extinction of mammoths and the arrival of humans. Pollen data indicate the increase in Betula during this time was widespread across Siberia and Beringia. We hypothesize that Betula increased due to a combination of a warming climate and reduced herbivory following the extinction of the Pleistocene mega herbivores. The rapid increase in Betula modified land surface albedo which climate-model simulations indicate would cause an average net warming of ∼0.021°C per percent increase in high latitude (53–73°N) Betula cover. We hypothesize that the extinction of mammoths increased Betula cover, which would have warmed Siberia and Beringia by on average 0.2°C, but regionally by up to 1°C. If humans were partially responsible for the extinction of the mammoths, then human influences on global climate predate the origin of agriculture.”

The prehistoric and preindustrial deforestation of Europe – Kaplan et al. (2009) “Humans have transformed Europe’s landscapes since the establishment of the first agricultural societies in the mid-Holocene. The most important anthropogenic alteration of the natural environment was the clearing of forests to establish cropland and pasture, and the exploitation of forests for fuel wood and construction materials. While the archaeological and paleoecological record documents the time history of anthropogenic deforestation at numerous individual sites, to study the effect that prehistoric and preindustrial deforestation had on continental-scale carbon and water cycles we require spatially explicit maps of changing forest cover through time. Previous attempts to map preindustrial anthropogenic land use and land cover change addressed only the recent past, or relied on simplistic extrapolations of present day land use patterns to past conditions. In this study we created a very high resolution, annually resolved time series of anthropogenic deforestation in Europe over the past three millennia by 1) digitizing and synthesizing a database of population history for Europe and surrounding areas, 2) developing a model to simulate anthropogenic deforestation based on population density that handles technological progress, and 3) applying the database and model to a gridded dataset of land suitability for agriculture and pasture to simulate spatial and temporal trends in anthropogenic deforestation. Our model results provide reasonable estimations of deforestation in Europe when compared to historical accounts. We simulate extensive European deforestation at 1000 BC, implying that past attempts to quantify anthropogenic perturbation of the Holocene carbon cycle may have greatly underestimated early human impact on the climate system.” Jed O. Kaplan, Kristen M. Krumhardt, and Niklaus Zimmermann, The prehistoric and preindustrial deforestation of Europe, Quaternary Science Reviews, Volume 28, Issues 27-28, December 2009, Pages 3016-3034, doi:10.1016/j.quascirev.2009.09.028. [Full text]

Effects of human land-use on the global carbon cycle during the last 6,000 years – Olofsson & Hickler (2008) “Humanity has become a major player within the Earth system, particularly by transforming large parts of the land surface and by altering the gaseous composition of the atmosphere. Deforestation for agricultural purposes started thousands of years ago and might have resulted in a detectable human influence on climate much earlier than the industrial revolution. This study presents a first attempt to estimate the impact of human land-use on the global carbon cycle over the last 6,000 years. A global gridded data set for the spread of permanent and non-permanent agriculture over this time period was developed and integrated within the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM). The model was run with and without human land-use, and the difference in terrestrial carbon storage was calculated as an estimate of anthropogenic carbon release to the atmosphere. The modelled total carbon release during the industrial period (a.d. 1850–1990) was 148 gigatons of carbon (GtC), of which 33 GtC originated from non-permanent agriculture. For pre-industrial times (4000 b.c.–a.d. 1850), the net carbon release was 79 GtC from permanent agriculture with an additional 35 GtC from non-permanent agriculture. The modelled pre-industrial carbon release was considerably lower than would be required for a substantial influence on the climate system.” Jörgen Olofsson and Thomas Hickler, Vegetation History and Archaeobotany, Volume 17, Number 5, 605-615, DOI: 10.1007/s00334-007-0126-6. [Full text]

Using multiple archives to understand past and present climate–human–environment interactions: the lake Erhai catchment, Yunnan Province, China – Dearing et al. (2008) “A 6.48 m sediment core sequence from Erhai lake, Yunnan Province, provides a multi-proxy record of Holocene environmental evolution and human activity in southwest China. These sedimentary records provide proxy time series for catchment vegetation, flooding, soil erosion, sediment sources and metal workings. They are complemented by independent regional climate time-series from speleothems, archaeological records of human habitation, and a detailed documented environmental history. The article attempts to integrate these data sources to provide a Holocene scale record of environmental change and human–environment interactions. These interactions are analysed in order to identify the roles of climate and social drivers on environmental change, and the lessons that may be learned about the future sustainability of the landscape. The main conclusions are: lake sediment evidence for human impacts from at least 7,500 cal year BP is supported by a terrestrial record of cultural horizons that may extend back to ∼9,000 cal year BP. A major shift in the pollen assemblage, defined by detrended correspondence analysis, at ∼4,800 cal year BP marks the transition from a ‘nature-dominated’ to a ‘human-dominated’ landscape. From 4,300 cal year BP, a change in river discharge responses may signal the beginning of hydraulic modification through drainage and irrigation. Major increases in disturbed land taxa and loss of forest taxa from 2,200 cal year BP onward, also associated with the start of significant topsoil erosion, register the expansion of agriculture by Han peoples. It is also the start of silver smelting linked to trade along the SW Silk Road with Dali becoming a regional centre. Peak levels of disturbed land taxa, topsoil and gully erosion are associated with the rise and fall of the Nanzhao (CE 738–902) and Dali (CE 937–1253) Kingdoms, and the documented environmental crisis that occurred in the late Ming and Qing dynasties (CE 1644–1911). The crisis coincides with a stronger summer monsoon, but exploitation of marginal agricultural land is the main driver. These historical perspectives provide insight into the resilience and sustainability of the modern agricultural system. The largest threat comes from high magnitude-low frequency flooding of lower dry farmed terraces and irrigated valley plains. A sustainable future depends on reducing the use of high altitude and steep slopes for grazing and cultivation, maintaining engineered flood defences and terraces, and anticipating the behaviour of the summer monsoon.” J. A. Dearing, R. T. Jones, J. Shen, X. Yang, J. F. Boyle, G. C. Foster, D. S. Crook and M. J. D. Elvin, Using multiple archives to understand past and present climate–human–environment interactions: the lake Erhai catchment, Yunnan Province, China, 2008, Journal of Paleolimnology, Volume 40, Number 1, 3-31, DOI: 10.1007/s10933-007-9182-2.

Climate-human-environment interactions: resolving our past – Dearing (2006) “The paper reviews how we can learn from the past about climate-human-environment interactions at the present time, and in the future. It focuses on data sources for environmental change at local/regional and regional/global spatial scales, and shows the scope and limitations of each. It reviews alternative methods for learning from the past, including the increasing use of simulation models. The use of multiple records (observational, palaeoenvironmental, archaeological, documentary) in local case-studies is exemplified in a study from China, where independent records help unravel the complexity of interactions and provide a basis for assessing the resilience and sustainability of the landscape system. Holocene global records for Natural Forcings (e.g. climate and tectonics), Human Society and Ecosystems are reviewed, and the problems of reconstructing global records of processes that are only recorded at local scales examined. Existing regional/global records are used to speculate about the veracity of anthropogenic forcing of global climate, with specific consideration of the Ruddiman theory. The paper concludes that a full understanding of causes of earth system change through (at least) the Holocene can come only through the most rigorous reconstructions of climate, human activities and earth processes, and importantly their interactions, at all locations and at all scales. It follows that we need to promote inter-scale learning: regionalisation and generalisation of existing data would be useful first steps. There is now a need to develop long-term simulation models that can help anticipate complex ecosystem behaviour and environmental processes in the face of global environmental change – and resolving our past is an essential element in that endeavour.” Dearing, J. A.: Climate-human-environment interactions: resolving our past, Clim. Past, 2, 187-203, doi:10.5194/cp-2-187-2006, 2006. [Full text]

The Anthropogenic Greenhouse Era Began Thousands of Years Ago – Ruddiman (2003) “The anthropogenic era is generally thought to have begun 150 to 200 years ago, when the industrial revolution began producing CO2 and CH4 at rates sufficient to alter their compositions in the atmosphere. A different hypothesis is posed here: anthropogenic emissions of these gases first altered atmospheric concentrations thousands of years ago. This hypothesis is based on three arguments. (1) Cyclic variations in CO2 and CH4 driven by Earth-orbital changes during the last 350,000 years predict decreases throughout the Holocene, but the CO2 trend began ananomalous increase 8000 years ago, and the CH4 trend did so 5000 years ago.(2) Published explanations for these mid- to late-Holocene gas increases basedon natural forcing can be rejected based on paleoclimatic evidence. (3) A wide array of archeological, cultural, historical and geologic evidence points to viable explanations tied to anthropogenic changes resulting from early agriculture in Eurasia, including the start of forest clearance by 8000 years ago and of rice irrigation by 5000 years ago. In recent millennia, the estimated warming caused by these early gas emissions reached a global-mean value of 0.8 °C and roughly 2 °C at high latitudes, large enough to have stopped a glaciation of northeastern Canada predicted by two kinds of climatic models. CO2 oscillations of 10 ppm in the last 1000 years are toolarge to be explained by external (solar-volcanic) forcing, but they can be explained by outbreaks of bubonic plague that caused historically documented farm abandonment in western Eurasia. Forest regrowth on abandoned farms sequestered enough carbon to account for the observed CO2decreases. Plague-driven CO2 changes were also a significant causal factor in temperature changes during the Little Ice Age (1300–1900 AD).” William F. Ruddiman, Climatic Change, Volume 61, Number 3, 261-293, DOI: 10.1023/B:CLIM.0000004577.17928.fa. [Full text]

The case for human causes of increased atmospheric CH4 over the last 5000 years – Ruddiman & Thomson (2001) “We propose that humans significantly altered atmospheric CH4 levels after 5000 years BP and that anthropogenic inputs just prior to the industrial revolution accounted for up to 25% of the CH4 level of 725 ppb (parts per billion). We base this hypothesis on three arguments: (1) the 100 ppb increase in atmospheric CH4 that occurred after 5000 years BP follows a pattern unprecedented in any prior orbitally driven change in the ice-core record; (2) non-anthropogenic explanations for this increase (expansion of boreal peat lands or tropical wetlands) are inconsistent with existing evidence; and (3) inefficient early rice farming is a quantitatively plausible means of producing anomalously large CH4 inputs to the atmosphere prior to the industrial revolution. If the areas flooded for farming harbored abundant CH4-producing weeds, disproportionately large amounts of CH4 would have been produced in feeding relatively small pre-industrial populations.” [Full text]

On the origin and magnitude of pre-industrial anthropogenic CO2 and CH4 emissions – Kammen & Marino (1993) “The potential impact of human activity on the climate system, particularly as related to fossil fuel combustion, is widely acknowledged. However, little is known of the origin and magnitude of anthropogenic non-fossil emissions, although this activity currently contributes up to 40% of the global CO2 emissions. Here we provide estimates of CO2 and CH4 emissions resulting from pre-industrial societies by combining historical demographic and archaeological data. Combustion of non-fossil carbon for domestic needs, small-scale industrial/craft activities and resulting from agricultural land management was significant, reaching about 1 Gt of carbon (GtC) as CO2yr−1 and 10 Tg of of carbon CH4yr−1 by 1800 A.D. This data implies a significant anthropogenic source of pre-industrial atmospheric greenhouse gases; consistent with estimates derived from carbon cycle models. We illustrate the contribution of archaeological data with two case studies: (i) estimates of CH4 emissions from agricultural activity from the Maya Lowlands; and (ii) evidence of correlations between climatic and socio-economic conditions in North Atlantic Norse settlements. This work provides an improved baseline for studies of historic climate change, such as the Little Ice Age, as well as for evaluating strategies for mitigating current greenhouse gas emissions.”

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