AGW Observer

Observations of anthropogenic global warming

New research from last week 8/2012

Posted by Ari Jokimäki on February 27, 2012

You know those that claim global warming has stopped? Well, it seems that they are talking about boreal winter only.

You know the climate models that can’t do anything right? Well, it seems that they should put tails on them.

You know that the global warming has happened before? Well, it seems that also mass extinctions have happened before.

We also have studies on Himalayan glaciers, Central America climate change rate, extreme weather in China, Russian 2010 heat wave, wind power density, Miocene climate optimum, Turkey corn, and climate sensitivity. Question of the week is: Do kangaroos in Australia affect the temperature trends?


Recent lapse in global warming is just a boreal winter thing

Asymmetric seasonal temperature trends – Cohen et al. (2012) [FULL TEXT]

Abstract: “Current consensus on global climate change predicts warming trends driven by anthropogenic forcing, with maximum temperature changes projected in the Northern Hemisphere (NH) high latitudes during winter. Yet, global temperature trends show little warming over the most recent decade or so. For longer time periods appropriate to the assessment of trends, however, global temperatures have experienced significant warming trends for all seasons except winter, when cooling trends exist instead across large stretches of eastern North America and northern Eurasia. Hence, the most recent lapse in global warming is a seasonal phenomenon, prevalent only in boreal winter. Additionally, we show that the largest regional contributor to global temperature trends over the past two decades is land surface temperatures in the NH extratropics. Therefore, proposed mechanisms explaining the fluctuations in global annual temperatures should address this apparent seasonal asymmetry.”

Citation: Cohen, J. L., J. C. Furtado, M. Barlow, V. A. Alexeev, and J. E. Cherry (2012), Asymmetric seasonal temperature trends, Geophys. Res. Lett., 39, L04705, doi:10.1029/2011GL050582.


Long probability distribution tails complicate model estimates of temperature extremes

Long tails in regional surface temperature probability distributions with implications for extremes under global warming – Ruff & Neelin (2012) [FULL TEXT]

Abstract: “Prior work has shown that probability distributions of column water vapor and several passive tropospheric chemical tracers exhibit longer-than-Gaussian (approximately exponential) tails. The tracer-advection prototypes explaining the formation of these long-tailed distributions motivate exploration of observed surface temperature distributions for non-Gaussian tails. Stations with long records in various climate regimes in National Climatic Data Center Global Surface Summary of Day observations are used to examine tail characteristics for daily average, maximum and minimum surface temperature probability distributions. Each is examined for departures from a Gaussian fit to the core (here approximated as the portion of the distribution exceeding 30% of the maximum). While the core conforms to Gaussian for most distributions, roughly half the cases exhibit non-Gaussian tails in both winter and summer seasons. Most of these are asymmetric, with a long, roughly exponential, tail on only one side. The shape of the tail has substantial implications for potential changes in extreme event occurrences under global warming. Here the change in the probability of exceeding a given threshold temperature is quantified in the simplest case of a shift in the present-day observed distribution. Surface temperature distributions with long tails have a much smaller change in threshold exceedances (smaller increases for high-side and smaller decreases for low-side exceedances relative to exceedances in current climate) under a given warming than do near-Gaussian distributions. This implies that models used to estimate changes in extreme event occurrences due to global warming should be verified regionally for accuracy of simulations of probability distribution tails.”

Citation: Ruff, T. W. and J. D. Neelin (2012), Long tails in regional surface temperature probability distributions with implications for extremes under global warming, Geophys. Res. Lett., 39, L04704, doi:10.1029/2011GL050610.


Global warming possibly one cause for Permian–Triassic mass extinction

Climate warming in the latest Permian and the Permian–Triassic mass extinction – Joachimski et al. (2012)

Abstract: “High-resolution oxygen isotope records document the timing and magnitude of global warming across the Permian-Triassic (P-Tr) boundary. Oxygen isotope ratios measured on phosphate-bound oxygen in conodont apatite from the Meishan and Shangsi sections (South China) decrease by 2‰ in the latest Permian, translating into low-latitude surface water warming of 8 °C. The oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates, suggesting that the addition of isotopically light carbon to the ocean-atmosphere system by Siberian Traps volcanism and related processes resulted in higher greenhouse gas levels and global warming. The major temperature rise started immediately before the main extinction phase, with maximum and harmful temperatures documented in the latest Permian (Meishan: bed 27). The coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems. In addition, very warm climate conditions in the Early Triassic may have played a major role in the delayed recovery in the aftermath of the Permian-Triassic crisis.”

Citation: Michael M. Joachimski, Xulong Lai, Shuzhong Shen, Haishui Jiang, Genming Luo, Bo Chen, Jun Chen and Yadong Sun, Geology, v. 40 no. 3 p. 195-198, doi: 10.1130/G32707.1.


Himalayan glaciers have gotten darker

Darkening of the mid-Himalaya glaciers since 2000 and the potential causes – Ming et al. (2012) [FULL TEXT]

Abstract: “Himalayan glaciers are a vital water source for people in the high regions of Asia. Their complete melting would be a crisis for approximately 1 billion people. Albedo is one of the key parameters that affect the energy balance of the snow and ice surfaces. Since 2000, albedos have been retrieved from satellite data for eleven representative Himalayan glaciers. It was found that most of the glaciers showed declining trends in the albedo of their upper areas, indicating that they have generally become darker in the past decade. A simulation case study in conjunction with in situ measurements showed that light-absorbing constituents (e.g., black carbon and dust) could be partly responsible for this phenomenon during late springtime; the background regional warming could also be responsible. The current surface radiation absorption in Himalayan glaciers could lead to significant melting, causing most of them to be in danger of rapid mass loss.”

Citation: Jing Ming et al 2012 Environ. Res. Lett. 7 014021 doi:10.1088/1748-9326/7/1/014021.


In 86,000 year temperature record from Central America no climate change matches the rate of current one

Rapid climate change and no-analog vegetation in lowland Central America during the last 86,000 years – Correa-Metrio et al. (2012)

Abstract: “Glacial–interglacial climate cycles are known to have triggered migrations and reassortments of tropical biota. Although long-term precessionally-driven changes in temperature and precipitation have been demonstrated using tropical sediment records, responses to abrupt climate changes, e.g. the cooling of Heinrich stadials or warmings of the deglaciation, are poorly documented. The best predictions of future forest responses to ongoing warming will rely on evaluating the influences of both abrupt and long-term climate changes on past ecosystems. A sedimentary sequence recovered from Lake Petén-Itzá, Guatemalan lowlands, provided a natural archive of environmental history. Pollen and charcoal analyses were used to reconstruct the vegetation and climate history of the area during the last 86,000 years. We found that vegetation composition and air temperature were strongly influenced by millennial-scale changes in the North Atlantic Ocean. Whereas Greenland warm interstadials were associated with warm and relatively wet conditions in the Central American lowlands, cold Greenland stadials, especially those associated with Heinrich events, caused extremely dry and cold conditions. Even though the vegetation seemed to have been highly resilient, plant associations without modern analogs emerged mostly following sharp climate pulses of either warmth or cold, and were paralleled by exceptionally high rates of ecological change. Although pulses of temperature change are evident in this 86,000-year record none matched the rates projected for the 21st Century. According to our findings, the ongoing rapid warming will cause no-modern-analog communities, which given the improbability of returning to lower-than-modern CO2 levels, anthropogenic barriers to migration, and increased anthropogenic fires, will pose immense threats to the biodiversity of the region.”

Citation: Alexander Correa-Metrio, Mark B. Bush, Kenneth R. Cabrera, Shannon Sully, Mark Brenner, David A. Hodell, Jaime Escobar, Tom Guilderson, Quaternary Science Reviews, http://dx.doi.org/10.1016/j.quascirev.2012.01.025.


Extreme temperature and extreme rain have increased in southern China

Spatial and temporal changes in extreme temperature and extreme precipitation in Guangxi – Nie et al. (2012)

Abstract: “This study focuses on extreme temperature and extreme precipitation changes in Guangxi Province of south China, which has experienced increased numbers of climate disasters in recent years. In this paper, spatial and temporal changes in extreme temperature and extreme precipitation were reconstructed for the period 1960–2009. The method of FFT filtering was used to smooth time series of extreme temperature and extreme precipitation, linear regression to calculate linear fits, and spline interpolation to interpolate station data and estimate linear changes. The results show that the annual extreme temperature increased in most of the area during 1960–2009, especially in the northeast. The greatest increase was in the extreme temperature in winter, compared to that in autumn, summer and spring in order from high to low across most of the study area. The annual extreme precipitation changed little in the first three decades and increased significantly in the last two decades, and varied with region and season. Spatially, the annual trend of extreme precipitation increased across most of the province, except in some areas of the southeast. The seasonal change trend of extreme precipitation varied greatly across different areas.”

Citation: Chengjing Nie, Hairong Li, Linsheng Yang, Bixiong Ye, Erfu Dai, Shaohong Wu, Yi Liu, Yongfeng Liao, Quaternary International, http://dx.doi.org/10.1016/j.quaint.2012.02.029.


Anthropogenic warming in southeastern Australia seems to proceed with step changes

Detecting and attributing nonlinear anthropogenic regional warming in southeastern Australia – Jones (2012)

Abstract: “Nonlinear anthropogenic warming is detected and attributed as a series of step changes in observed and simulated climate for southeastern Australia (SEA). A stationary period of 1910–1967 and non-stationary period of 1968–2010 was established using statistically significant step-changes (pH0 < 0.01) in the relationship between observed minimum (Tmin) and maximum (Tmax) temperature (0.6°C in 1968) and Tmax and rainfall (P; 0.7°C in 1997). Regressions between these pairings during stationary conditions were used to determine how Tmin and Tmax would have evolved under non-stationary conditions. Assuming these relationships remain constant, the resulting residuals were attributed to anthropogenic regional warming. This warming was initiated as step changes in 1968 for Tmin (0.7°C) and 1973 for Tmax (0.5°C), coinciding with step changes in zonal (24–44°S) and southern hemisphere mean air temperatures (Tav). A step change in 1997 in Tmax (0.8°C) coincided with a statistically significant step change in global mean air temperature of 0.3°C. This analysis was repeated using regionally averaged output from eleven climate model simulations. Regional warming in all models commenced with step changes in Tmin ranging from 0.4 to 0.7°C between 1964 and 2003. Tmax underwent step changes ranging from 0.7 to 1.1°C simultaneously or within several decades. Further step changes, combined with rising trends, were simulated under increasing radiative forcing to 2100. This highlights limitations in the current use of the signal-to-noise model that considers anthropogenic climate change as a monotonic curve. The identification of multiple step changes in a changing climate provides important information for planning adaptation.”

Citation: Jones, R. N. (2012), Detecting and attributing nonlinear anthropogenic regional warming in southeastern Australia, J. Geophys. Res., 117, D04105, doi:10.1029/2011JD016328.


Russian 2010 heat wave was both natural and anthropogenic in origin

Reconciling two approaches to attribution of the 2010 Russian heat wave – Otto et al. (2012)

Abstract: “In the summer 2010 Western Russia was hit by an extraordinary heat wave, with the region experiencing by far the warmest July since records began. Whether and to what extent this event is attributable to anthropogenic climate change is controversial. Dole et al. (2011) report the 2010 Russian heat wave was “mainly natural in origin” whereas Rahmstorf and Coumou (2011) write that with a probability of 80% “the 2010 July heat record would not have occurred” without the large-scale climate warming since 1980, most of which has been attributed to the anthropogenic increase in greenhouse gas concentrations. The latter explicitly state that their results “contradict those of Dole et al. (2011).” Here we use the results from a large ensemble simulation experiment with an atmospheric general circulation model to show that there is no substantive contradiction between these two papers, in that the same event can be both mostly internally-generated in terms of magnitude and mostly externally-driven in terms of occurrence-probability. The difference in conclusion between these two papers illustrates the importance of specifying precisely what question is being asked in addressing the issue of attribution of individual weather events to external drivers of climate.”

Citation: Otto, F. E. L., N. Massey, G. J. van Oldenborgh, R. G. Jones, and M. R. Allen (2012), Reconciling two approaches to attribution of the 2010 Russian heat wave, Geophys. Res. Lett., 39, L04702, doi:10.1029/2011GL050422.


Wind power density and wind speed decrease in U.S. High Plains during winter and spring

Estimated changes in wind speed and wind power density over the western High Plains, 1971–2000 – Greene et al. (2012)

Abstract: “This manuscript presents the results of research on the temporal patterns in wind speed and wind power density from 1971 to 2000. The study area is across the western High Plains states east of the Rocky Mountains in an area which has a proven wind power resource. Policies and economic analyses involving the rapidly expanding wind power industry have often assumed a constant in the wind resource; however, any temporal pattern or trend in wind speeds can have a meaningful impact on the reliability of wind power as an energy resource. Using data provided by the North American Regional Climate Change Assessment Program (NARCCAP) to analyze decadal and seasonal trends of wind data, this study shows that from 1971 to 2000 there were some notable changes in the NARCCAP simulated wind velocities over the study region. Wind speed trends across the central High Plains of the USA were most notable across the western portion of the study area along the higher terrain near the front range of the Rocky Mountains. The most significant changes occurred during winter and spring when a large portion of the study area experienced the most substantial decrease in wind speed, with a 20% reduction in wind power density during spring across the western portion of the study area. During summer and fall, the trends are less noticeable, with only very small changes in the summer. Fall was the only season that saw widespread increased values of wind power density from the 1970s to 1990s, with increases of nearly 10% in some southern areas of the study area. Based upon the analysis of the data and previous literature, it is theorized that these changes could be the result of changing synoptic patterns across the study region.”

Citation: J. Scott Greene, Matthew Chatelain, Mark Morrissey and Steve Stadler, Theoretical and Applied Climatology, DOI: 10.1007/s00704-012-0596-z.


Model shows far less ocean warming than proxies show during Miocene climatic optimum

Modeling the Miocene climatic optimum: Ocean circulation – Herold et al. (2012)

Abstract: “Ocean circulation is investigated using the Community Climate System Model 3 (CCSM3) forced with early to middle Miocene (∼20–14 Ma) topography, bathymetry, vegetation and modern CO2. Significant bottom water formation is modeled in the Weddell Sea along with intermediate North Component Water formation in the North Atlantic. This is attributed primarily to stronger- and weaker-than-modern convective preconditioning in the Weddell and Labrador Seas, respectively. Global meridional overturning and gyre circulation is weaker in the Miocene due to weaker midlatitude westerlies in the southern hemisphere, caused by lowering of the meridional surface temperature gradient, in addition to regional influences on convection. Subsurface temperatures in the Miocene are significantly higher in the far North Atlantic, Greenland-Norwegian Seas and Arctic basin compared to the present. Ocean heat transport is symmetrical about the equator and resembles that simulated for late Cretaceous and early Cenozoic climates, suggesting the northern hemisphere dominated ocean heat transport active today developed after the middle Miocene. Simulated deep water warming in the Miocene is more than an order of magnitude lower than indicated by proxies. This discrepancy is not reconciled by higher CO2 due to the persistence of sea-ice at sites of deep water formation. This suggests that either the CCSM3 is insufficiently sensitive to Miocene boundary conditions, greater greenhouse forcing existed than is currently reconstructed, or that proxy records of warming are exaggerated. Given the diversity of global Miocene proxy records and their near-unanimous estimate of a significantly warmer Earth, the first two options are more likely.”

Citation: Herold, N., M. Huber, R. D. Müller, and M. Seton (2012), Modeling the Miocene climatic optimum: Ocean circulation, Paleoceanography, 27, PA1209, doi:10.1029/2010PA002041.


Corn yield in western Turkey is generally expected to decrease

Evaluation of climate change effects on future corn (Zea mays L.) yield in western Turkey – Durdu (2012)

Abstract: “A comparative performance analysis was studied on well-known drought indices [Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI) and its moisture anomaly index (Orig-Z), self-calibrated Palmer Drought Severity Index (SC-PDSI) and its moisture anomaly index (SC-Z)] to determine the most appropriate index for assessing corn (Zea mays L.) yield in four crop regions (Aydın, Denizli, Afyon, Uşak) in western Turkey and to evaluate the vulnerability of corn production to climate change with future projections provided by the Hadley Centre for Climate Prediction and Research ENSEMBLES project (HadCM3Q0). A series of curvilinear regression-based crop-yield models were developed for each of the crop region based on the drought indices. The crop-yield model that performed best at high-drought risk years was the SC-PDSI in Aydın region and the PDSI in Denizli, Afyon and Uşak regions. The SC-PDSI index in Aydın region described 75.1% of the measured variability. The PDSI index in Denizli Ayfon and Uşak regions explained 69.8, 71.3 and 66.4% of the measured yield variability, respectively. The vulnerability of the corn yield to HadCM3Q0 projections was evaluated for Aydın and Afyon regions due to the resolution of the regional climate model. For the high-drought risk years, the expected decrease in corn yields was 2.1 ton ha−1 in Aydın region and 0.014 ton ha−1 for Afyon region. For the low drought risk years, the crop yield models predicted the expected decrease in corn yield as 0.104 ton ha−1 in Afyon region. However, there was a positive yield response by 0.022 ton ha−1 in Aydın region.”

Citation: Ömer Faruk Durdu, International Journal of Climatology, DOI: 10.1002/joc.3435.


New climate sensitivity estimate is consistent with previous studies

A climate sensitivity estimate using Bayesian fusion of instrumental observations and an Earth System model – Olson et al. (2012) [FULL TEXT]

Abstract: “Current climate model projections are uncertain. This uncertainty is partly driven by the uncertainty in key model parameters such as climate sensitivity (CS), vertical ocean diffusivity (Kv), and strength of anthropogenic sulfate aerosol forcing. These parameters are commonly estimated using ensembles of model runs constrained by observations. Here we obtain a probability density function (pdf) of these parameters using the University of Victoria Earth System Climate Model (UVic ESCM) – an intermediate complexity model with a dynamic three-dimensional ocean. Specifically, we run an ensemble of UVic ESCM runs varying parameters that affect CS, ocean vertical diffusion, and the effects of anthropogenic sulfate aerosols. We use a statistical emulator that interpolates the UVic ESCM output to parameter settings where the model was not evaluated. We adopt a Bayesian approach to constrain the model output with instrumental surface temperature and ocean heat observations. Our approach accounts for the uncertainties in the properties of model-data residuals. We use a Markov chain Monte Carlo method to obtain a posterior pdf of these parameters. The mode of the climate sensitivity estimate is 2.8°C, with the corresponding 95% credible interval ranging from 1.8 to 4.9°C. These results are generally consistent with previous studies. The CS pdf is sensitive to the assumptions about the priors, to the effects of anthropogenic sulfate aerosols, and to the background vertical ocean diffusivity. Our method can be used with more complex climate models.”

Citation: Olson, R., R. Sriver, M. Goes, N. M. Urban, H. D. Matthews, M. Haran, and K. Keller (2012), A climate sensitivity estimate using Bayesian fusion of instrumental observations and an Earth System model, J. Geophys. Res., 117, D04103, doi:10.1029/2011JD016620.


CLASSIC OF THE WEEK: Mitchell (1953)

On the causes of instrumentally observed secular temperature trends – Mitchell (1953) [FULL TEXT]

Abstract: “Three independent studies of city influence are presented. In the first, recent overlapping observations between the New Haven city and airport stations are used to estimate the local city influence which in turn is used to revise the secular station trend. In the second, evidence of negligible city influence but of real climatic change at Blue Hill Observatory since 1890 is discussed. In the third, a statistical study involving 77 stations in the United States, whose temperature records were observationally homogeneous between 1900 and 1940, bears out the prevalence of important city influence in this country. Except in the period of rapid climatic temperature change occurring since about 1890, observed temperature records, with few individual exceptions, are concluded to be very misleading as direct measures of macroclimatic change over periods longer than a few decades. With their use in climatic studies, particularly those extending back of 1900, isolation of the effects of widespread urban development and frequent thermometer relocation is imperative. At average stations in the United States, urban development has contributed local temperature rises at the rate of more than 1F in a century. The influence of very large cities has not been in proportion.”

Citation: Mitchell, J. Murray, 1953, J. Meteor., 10, 244–261, doi: http://dx.doi.org/10.1175/1520-0469(1953)0102.0.CO;2.


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

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