AGW Observer

Observations of anthropogenic global warming

Archive for September, 2009

New index page

Posted by Ari Jokimäki on September 7, 2009

I have made an index page for the paperlists, as requested:
https://agwobserver.wordpress.com/index/

If you have any comments and suggestions about that, post them here.

Posted in General | 2 Comments »

Papers on tropical troposphere hotspot

Posted by Ari Jokimäki on September 6, 2009

This list contains papers on the tropical troposphere hotspot. 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 4, 2017): Seidel et al. (2012), Mitchell et al. (2013), Varotsos et al. (2013), and Po-Chedley et al. (2015) added. Thanks to Barry for pointing them out.
UPDATE (January 2, 2012): Fu et al. (2011) added.
UPDATE (September 21, 2010): McIntyre & McKitrick (2009) removed (it didn’t pass peer-review) and McKitrick et al. (2010) added.
UPDATE (January 4, 2009): Addendum for Douglass et al. (2008) added, thanks to kse for pointing this out, see the comment section below.
UPDATE (December 24, 2009): Fu et al. (2004) and Steiner et al. (2009) moved to global troposphere list. Some of the papers are still in both lists.
UPDATE (December 24, 2009): Sherwood et al. (2008) added and final publication links to Bengtsson & Hodges (2009) added.
UPDATE (September 23, 2009): Steiner et al. (2009) added, thanks for John Cook for pointing this out (see the comment section below). McCarthy et al. (2008) added.
UPDATE (September 13, 2009): Bengtsson & Hodges (2009?) added.

Removing Diurnal Cycle Contamination in Satellite-Derived Tropospheric Temperatures: Understanding Tropical Tropospheric Trend Discrepancies – Po-Chedley et al. (2015) “Independent research teams have constructed long-term tropical time series of the temperature of the middle troposphere (TMT) using satellite Microwave Sounding Unit (MSU) and Advanced MSU (AMSU) measurements. Despite careful efforts to homogenize the MSU/AMSU measurements, tropical TMT trends beginning in 1979 disagree by more than a factor of 3. Previous studies suggest that the discrepancy in tropical TMT trends is caused by differences in both the NOAA-9 warm target factor and diurnal drift corrections. This work introduces a new observationally based method for removing biases related to satellite diurnal drift. Over land, the derived diurnal correction is similar to a general circulation model (GCM) diurnal cycle. Over ocean, the diurnal corrections have a negligible effect on TMT trends, indicating that oceanic biases are small. It is demonstrated that this method is effective at removing biases between coorbiting satellites and biases between nodes of individual satellites. Using a homogenized TMT dataset, the ratio of tropical tropospheric temperature trends relative to surface temperature trends is in accord with the ratio from GCMs. It is shown that bias corrections for diurnal drift based on a GCM produce tropical trends very similar to those from the observationally based correction, with a trend difference smaller than 0.02 K decade−1. Differences between various TMT datasets are explored further. Large differences in tropical TMT trends between this work and that of the University of Alabama in Huntsville (UAH) are attributed to differences in the treatment of the NOAA-9 target factor and the diurnal cycle correction.” Stephen Po-Chedley, Tyler J. Thorsen, and Qiang Fu, Journal of Climate, 28, 6, DOI: http://dx.doi.org/10.1175/JCLI-D-13-00767.1. [Full text]

Plausible reasons for the inconsistencies between the modeled and observed temperatures in the tropical troposphere – Varotsos et al. (2013) “We hereby attempt to detect plausible reasons for the discrepancies between the measured and modeled tropospheric temperature anomalies in the tropics. For this purpose, we calculate the trends of the upper-minus-lower tropospheric temperature anomaly differences (TAD) for both the measured and modeled time series during 1979–2010. The modeled TAD trend is significantly higher than that of the measured ones, confirming that the vertical amplification of warming is exaggerated in models. To investigate the cause of this exaggeration, we compare the intrinsic properties of the measured and modeled TAD by employing detrended fluctuation analysis (DFA). The DFA exponent obtained for the measured values reveals white noise behavior, while the exponent for the modeled ones shows that they exhibit long-range power law correlations. We suggest that the vertical amplification of warming derived from modeled simulations is weighted with a persistent signal, which should be removed in order to achieve better agreement with observations.” Varotsos, C. A., M. N. Efstathiou, and A. P. Cracknell (2013), Plausible reasons for the inconsistencies between the modeled and observed temperatures in the tropical troposphere, Geophys. Res. Lett., 40, 4906–4910, doi:10.1002/grl.50646. [Full text]

Revisiting the controversial issue of tropical tropospheric temperature trends – Mitchell et al. (2013) “Controversy remains over a discrepancy between modeled and observed tropical upper tropospheric temperature trends. This discrepancy is reassessed using simulations from the Coupled Climate Model Inter-comparison Project phase 5 (CMIP 5) together with radiosonde and surface observations that provide multiple realizations of possible “observed” temperatures given various methods of homogenizing the data. Over the 1979–2008 period, tropical temperature trends are not consistent with observations throughout the depth of the troposphere, and this primarily stems from a poor simulation of the surface temperature trends. This discrepancy is substantially reduced when (1) atmosphere-only simulations are examined or (2) the trends are considered as an amplification of the surface temperature trend with height. Using these approaches, it is shown that within observational uncertainty, the 5–95 percentile range of temperature trends from both coupled-ocean and atmosphere-only models are consistent with the analyzed observations at all but the upper most tropospheric level (150 hPa), and models with ultra-high horizontal resolution (≤ 0.5° × 0.5°) perform particularly well. Other than model resolution, it is hypothesized that this remaining discrepancy could be due to a poor representation of stratospheric ozone or remaining observational uncertainty.” Mitchell, D. M., P. W. Thorne, P. A. Stott, and L. J. Gray (2013), Revisiting the controversial issue of tropical tropospheric temperature trends, Geophys. Res. Lett., 40, 2801–2806, doi:10.1002/grl.50465. [Full text]

Reexamining the warming in the tropical upper troposphere: Models versus radiosonde observations – Seidel et al. (2012) “A recent study of 1979–2010 tropical tropospheric temperature trends in climate model simulations and satellite microwave sounding unit (MSU) observations concluded that, although both showed greater warming in the upper than lower troposphere, the vertical amplification of warming was exaggerated in most models. We repeat that analysis of temperature trends, vertical difference trends, and trend ratios using five radiosonde datasets. Some, but not all, comparisons support the notion that vertical amplification in models exceeds that observed. However, larger ranges of radiosonde trends compared with those for MSU, and the sensitivity of results to the upper-tropospheric level analyzed, make it difficult to conclude unambiguously that models are inconsistent with radiosonde observations. The larger ranges are due to the availability of more radiosonde datasets with different approaches for adjusting measurement biases. Together these two studies highlight challenges of using imperfect observations of tropical tropospheric temperature over a few decades to assess climate model performance.” Seidel, D. J., M. Free, and J. S. Wang (2012), Reexamining the warming in the tropical upper troposphere: Models versus radiosonde observations, Geophys. Res. Lett., 39, L22701, doi:10.1029/2012GL053850. [Full text]

On the warming in the tropical upper troposphere: Models versus observations – Fu et al. (2011) “IPCC (Intergovernmental Panel on Climate Change) AR4 (Fourth Assessment Report) GCMs (General Circulation Models) predict a tropical tropospheric warming that increases with height, reaches its maximum at ~200 hPa, and decreases to zero near the tropical tropopause. This study examines the GCM-predicted maximum warming in the tropical upper troposphere using satellite MSU (microwave sounding unit)-derived deep-layer temperatures in the tropical upper- and lower-middle troposphere for 1979–2010. While satellite MSU/AMSU observations generally support GCM results with tropical deep-layer tropospheric warming faster than surface, it is evident that the AR4 GCMs exaggerate the increase in static stability between tropical middle and upper troposphere during the last three decades.” Fu, Q., S. Manabe, and C. M. Johanson (2011), On the warming in the tropical upper troposphere: Models versus observations, Geophys. Res. Lett., 38, L15704, doi:10.1029/2011GL048101. [Full text]

Panel and multivariate methods for tests of trend equivalence in climate data series – McKitrick et al. (2010) “We explain panel and multivariate regressions for comparing trends in climate data sets. They impose minimal restrictions on the covariance matrix and can embed multiple linear comparisons, which is a convenience in applied work. We present applications comparing post-1979 modeled and observed temperature trends in the tropical lower- and mid-troposphere. Results are sensitive to the sample length. In data spanning 1979–1999, observed trends are not significantly different from zero or from model projections. In data spanning 1979–2009, the observed trends are significant in some cases but tend to differ significantly from modeled trends.” Ross McKitrick, Stephen McIntyre, Chad Herman, Atmospheric Science Letters, Article first published online: 17 SEP 2010, DOI: 10.1002/asl.290. [Full text]

On the evaluation of temperature trends in the tropical troposphere – Bengtsson & Hodges (2009) “A series of model experiments with the coupled Max-Planck-Institute ECHAM5/OM climate model have been investigated and compared with microwave measurements from the Microwave Sounding Unit (MSU) and re-analysis data for the period 1979-2008. … When forced by analysed sea surface temperature the model reproduces accurately the time-evolution of the mean outgoing tropospheric microwave radiation especially over tropical oceans but with a minor bias towards higher temperatures in the upper troposphere. … We have also compared the trend of the vertical lapse rate over the tropical oceans assuming that the difference between TLT and TMT is an approximate measure of the lapse rate. The TLT–TMT trend is larger in both the measurements and in the JRA25 than in the model runs by 0.04–0.06 K/decade. Furthermore, a calculation of all 30 year TLT–TMT trends of the unforced 500-year integration vary between ±0.03 K/decade suggesting that the models have a minor systematic warm bias in the upper troposphere.” [Full text]

Robust Tropospheric Warming Revealed by Iteratively Homogenized Radiosonde Data – Sherwood et al. (2008) “Results are presented from a new homogenization of data since 1959 from 527 radiosonde stations. … The troposphere warms at least as strongly as the surface, with local warming maxima at 300 hPa in the tropics” [Full text]

Toward Elimination of the Warm Bias in Historic Radiosonde Temperature Records—Some New Results from a Comprehensive Intercomparison of Upper-Air Data – Haimberger et al. (2008) “Both of the new adjusted radiosonde time series are in better agreement with satellite data than comparable published radiosonde datasets, not only for zonal means but also at most single stations. A robust warming maximum of 0.2–0.3K (10 yr)−1 for the 1979–2006 period in the tropical upper troposphere could be found in both homogenized radiosonde datasets.” [Full text]

Consistency of modelled and observed temperature trends in the tropical troposphere – Santer et al. (2008) “Early versions of satellite and radiosonde datasets suggested that the tropical surface had warmed more than the troposphere, while climate models consistently showed tropospheric amplification of surface warming in response to human-caused increases in well-mixed greenhouse gases (GHGs). We revisit such comparisons here using new observational estimates of surface and tropospheric temperature changes. We find that there is no longer a serious discrepancy between modelled and observed trends in tropical lapse rates. … Our results contradict a recent claim that all simulated temperature trends in the tropical troposphere and in tropical lapse rates are inconsistent with observations. This claim was based on use of older radiosonde and satellite datasets, and on two methodological errors: the neglect of observational trend uncertainties introduced by interannual climate variability, and application of an inappropriate statistical consistency test.” [Full text]

Warming maximum in the tropical upper troposphere deduced from thermal winds – Allen & Sherwood (2008) “Climate models and theoretical expectations have predicted that the upper troposphere should be warming faster than the surface. Surprisingly, direct temperature observations from radiosonde and satellite data have often not shown this expected trend. However, non-climatic biases have been found in such measurements. Here we apply the thermal-wind equation to wind measurements from radiosonde data, which seem to be more stable than the temperature data. … Warming patterns are consistent with model predictions except for small discrepancies close to the tropopause.” [Full text]

Assessing Bias and Uncertainty in the HadAT-Adjusted Radiosonde Climate Record – McCarthy et al. (2008) “This paper presents an automated homogenization method designed to replicate the decisions made by manual judgment in the generation of an earlier radiosonde dataset [i.e., the Hadley Centre radiosonde temperature dataset (HadAT)]. … Using climate model data to simulate biased radiosonde data, the authors show that limitations in the homogenization method are sufficiently large to explain much of the tropical trend discrepancy between HadAT and estimates from satellite platforms and climate models. … Previous assessment of trends and uncertainty in HadAT is likely to have underestimated the systematic bias in tropical mean temperature trends.” [Full text]

A comparison of tropical temperature trends with model predictions – Douglass et al. (2008) “We examine tropospheric temperature trends of 67 runs from 22 Climate of the 20th Century model simulations and try to reconcile them with the best available updated observations (in the tropics during the satellite era). Model results and observed temperature trends are in disagreement in most of the tropical troposphere, being separated by more than twice the uncertainty of the model mean.” [However, they ignored the observation uncertainties, see Santer et al. above and this RealClimate article.] [Full text] [Addendum]

Utility of Radiosonde Wind Data in Representing Climatological Variations of Tropospheric Temperature and Baroclinicity in the Western Tropical Pacific – Allen & Sherwood (2007) “Wind data show a slowing of the midlatitude jets in the Maritime Continent region since 1979, indicating that tropical thicknesses and temperature have increased less than those poleward of 25°N/S. This pattern is consistent with Microwave Sounding Unit temperature trends in the region but is exaggerated south of the equator in trends obtained directly from the temperature data. … These results support the use of the wind field as a way of overcoming heterogeneities in the temperature records in the monitoring of climate change patterns.” Allen, Robert J., Steven C. Sherwood, 2007, J. Climate, 20, 5229–5243. [Full text]

Tropical vertical temperature trends: A real discrepancy? – Thorne et al. (2007) “The uncertainty of inter-satellite calibration implied by available MSU T2 (mid-troposphere) estimates (σ = 0.035K) is much greater than that required to adequately resolve the trend (σ < 0.01K), or the amplification behaviour (implied amplification range ±0.95)."

Ozone, water vapor, and temperature in the upper tropical troposphere: Variations over a decade of MOZAIC measurements – Bortz et al. (2006) Provides another dataset for the tropics (by in situ aircraft samples), including water vapor and ozone measurements. “The decade of MOZAIC in situ measurements now available provides unique insights into the composition and processes of the upper tropical troposphere. In this analysis of temperature, water vapor, and ozone at flight cruise levels in the tropics, we find greater seasonal variability for all three parameters in the South (0–20°S) than in the North (0–20°N) Tropics.” [Full text]

The Vertical Structure of Temperature in the Tropics: Different Flavors of El Niño – Trenberth & Smith (2006) Discusses the strong role of El Niño on tropical temperatures. [Full text]

Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences – Karl et al. (2006) Report about temperature trends in stratosphere and in troposphere. [Full text of chapter 1]

Satellite-derived vertical dependence of tropical tropospheric temperature trends – Fu & Johanson (2005) “For the tropical troposphere’s response to greenhouse forcing, GCMs predict a positive temperature trend that is greater than that at the surface and increases with height [e.g., Hansen et al., 2002]. … Tropical atmospheric temperatures in different tropospheric layers are retrieved using satellite-borne Microwave Sounding Unit (MSU) observations. We find that tropospheric temperature trends in the tropics are greater than the surface warming and increase with height. Our analysis indicates that the near-zero trend from Spencer and Christy’s MSU channel-2 angular scanning retrieval for the tropical low-middle troposphere (T2LT) is inconsistent with tropical tropospheric warming derived from their MSU T2 and T4 data.” [Full text]

Amplification of Surface Temperature Trends and Variability in the Tropical Atmosphere – Santer et al. (2005) Highlights the problematics of the issue, and also notes the role of El Niño in tropical temperature variability. “On multidecadal time scales, tropospheric amplification of surface warming is a robust feature of model simulations, but it occurs in only one observational data set. Other observations show weak, or even negative, amplification.” [Full text]

Closely related

The Radiative Signature of Upper Tropospheric Moistening – Soden et al. (2005) “Climate models predict that the concentration of water vapor in the upper troposphere could double by the end of the century as a result of increases in greenhouse gases. Such moistening plays a key role in amplifying the rate at which the climate warms in response to anthropogenic activities, but has been difficult to detect because of deficiencies in conventional observing systems. We use satellite measurements to highlight a distinct radiative signature of upper tropospheric moistening over the period 1982 to 2004. The observed moistening is accurately captured by climate model simulations and lends further credence to model projections of future global warming.” [Full text]

There are a lot of papers discussing troposphere temperature trends from the global perspective. Those papers are not on the list above, but have their own list:

Papers on tropospheric temperatures

Posted in AGW evidence | 28 Comments »

Paperlists – some updates

Posted by Ari Jokimäki on September 5, 2009

I have been wondering if the links in my paperlists have been unclear, especially if everyone have realized that there usually are two links; first one to the official abstract page of the paper, and the second one to the PDF file containing the whole paper. Links have been side-by-side so they might be unclear. Therefore I have decided to move the PDF links at the end of each entry so that they are clearly separated from the abstact links. I’ll update all the old postings little by little.

Some of you may have wondered what are the paperlists for that I keep posting. One reason for it is that I’m using the paperlists myself, so they serve as linklists for my own benefit. I also hope that others benefit from them too in order to gain some real information about climate science straight from the source of the information, i.e. the scientists.

Posted in General | 5 Comments »

Papers on minor role of the Sun in recent climate change

Posted by Ari Jokimäki on September 3, 2009

NOTE! There is a new version of this paperlist: Papers on the role of the Sun in recent global warming.

This list contains papers that show Sun’s role to be minor in the recent climate change. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

LATEST UPDATE (April 18, 2012): Stauning (2011) added. Thanks to Barry for pointing it out.

Solar activity–climate relations: A different approach – Stauning (2011) “The presentation of solar activity–climate relations is extended with the most recent sunspot and global temperature data series. The extension of data series shows clearly that the changes in terrestrial temperatures are related to sources different from solar activity after ∼1985. Based on analyses of data series for the years 1850–1985 it is demonstrated that, apart from an interval of positive deviation followed by a similar negative excursion in Earth’s temperatures between ∼1923 and 1965, there is a strong correlation between solar activity and terrestrial temperatures delayed by 3 years, which complies with basic causality principles. A regression analysis between solar activity represented by the cycle-average sunspot number, SSNA, and global temperature anomalies, ΔTA, averaged over the same interval lengths, but delayed by 3 years, provides the relation ΔTA∼0.009 (±0.002) SSNA. Since the largest ever observed SSNA is ∼90 (in 1954–1965), the solar activity-related changes in global temperatures could amount to no more than ±0.4 °C over the past ∼400 years where the sunspots have been recorded. It is demonstrated that the small amplitudes of cyclic variations in the average global temperatures over the ∼11 year solar cycle excludes many of the various driver processes suggested in published and frequently quoted solar activity–climate relations. It is suggested that the in-cycle variations and also the longer term variations in global temperatures over the examined 135 years are mainly caused by corresponding changes in the total solar irradiance level representing the energy output from the core, but further modulated by varying energy transmission properties in the active outer regions of the Sun.” P. Stauning, Journal of Atmospheric and Solar-Terrestrial Physics, Volume 73, Issue 13, August 2011, Pages 1999–2012, http://dx.doi.org/10.1016/j.jastp.2011.06.011.

Are secular correlations between sunspots, geomagnetic activity, and global temperature significant? – Love et al. (2011) “Recent studies have led to speculation that solar-terrestrial interaction, measured by sunspot number and geomagnetic activity, has played an important role in global temperature change over the past century or so. We treat this possibility as an hypothesis for testing. We examine the statistical significance of cross-correlations between sunspot number, geomagnetic activity, and global surface temperature for the years 1868–2008, solar cycles 11–23. The data contain substantial autocorrelation and nonstationarity, properties that are incompatible with standard measures of cross-correlational significance, but which can be largely removed by averaging over solar cycles and first-difference detrending. Treated data show an expected statistically-significant correlation between sunspot number and geomagnetic activity, Pearson p < 10−4, but correlations between global temperature and sunspot number (geomagnetic activity) are not significant, p = 0.9954, (p = 0.8171). In other words, straightforward analysis does not support widely-cited suggestions that these data record a prominent role for solar-terrestrial interaction in global climate change. With respect to the sunspot-number, geomagnetic-activity, and global-temperature data, three alternative hypotheses remain difficult to reject: (1) the role of solar-terrestrial interaction in recent climate change is contained wholly in long-term trends and not in any shorter-term secular variation, or, (2) an anthropogenic signal is hiding correlation between solar-terrestrial variables and global temperature, or, (3) the null hypothesis, recent climate change has not been influenced by solar-terrestrial interaction.” Love, J. J., K. Mursula, V. C. Tsai, and D. M. Perkins (2011), Geophys. Res. Lett., 38, L21703, doi:10.1029/2011GL049380. [Full text]

An influence of solar spectral variations on radiative forcing of climate – Haigh et al. (2010) “The thermal structure and composition of the atmosphere is determined fundamentally by the incoming solar irradiance. Radiation at ultraviolet wavelengths dissociates atmospheric molecules, initiating chains of chemical reactions—specifically those producing stratospheric ozone—and providing the major source of heating for the middle atmosphere, while radiation at visible and near-infrared wavelengths mainly reaches and warms the lower atmosphere and the Earth’s surface. Thus the spectral composition of solar radiation is crucial in determining atmospheric structure, as well as surface temperature, and it follows that the response of the atmosphere to variations in solar irradiance depends on the spectrum. Daily measurements of the solar spectrum between 0.2 µm and 2.4 µm, made by the Spectral Irradiance Monitor (SIM) instrument on the Solar Radiation and Climate Experiment (SORCE) satellite since April 2004, have revealed that over this declining phase of the solar cycle there was a four to six times larger decline in ultraviolet than would have been predicted on the basis of our previous understanding. This reduction was partially compensated in the total solar output by an increase in radiation at visible wavelengths. Here we show that these spectral changes appear to have led to a significant decline from 2004 to 2007 in stratospheric ozone below an altitude of 45 km, with an increase above this altitude. Our results, simulated with a radiative-photochemical model, are consistent with contemporaneous measurements of ozone from the Aura-MLS satellite, although the short time period makes precise attribution to solar effects difficult. We also show, using the SIM data, that solar radiative forcing of surface climate is out of phase with solar activity. Currently there is insufficient observational evidence to validate the spectral variations observed by SIM, or to fully characterize other solar cycles, but our findings raise the possibility that the effects of solar variability on temperature throughout the atmosphere may be contrary to current expectations.” Joanna D. Haigh, Ann R. Winning, Ralf Toumi & Jerald W. Harder, Nature, Volume: 467, Pages: 696–699, Date published: 07 October 2010, doi:10.1038/nature09426. [Full text]

Solar change and climate: an update in the light of the current exceptional solar minimum – Lockwood (2010) “Solar outputs during the current solar minimum are setting record low values for the space age. Evidence is here reviewed that this is part of a decline in solar activity from a grand solar maximum and that the Sun has returned to a state that last prevailed in 1924. Recent research into what this means, and does not mean, for climate change is reviewed.” [Full text]

Cycles and trends in solar irradiance and climate – Lean (2009) “Claims that the Sun has caused as much as 70% of the recent global warming (based in part on the attribution of radiometric trends to real solar irradiance changes) presents fundamental puzzles. It requires that the Sun’s brightness increased more in the past century than at any time in the past millennium, including over the past 30 years, contrary to the direct space-based observations. And it requires, as well, that Earth’s climate be insensitive to well-measured increases in greenhouse gases at the same time that it is excessively sensitive to poorly known solar brightness changes. Both scenarios are far less plausible than the simple attribution of most (90%) industrial global warming to anthropogenic effects, rather than to the Sun.” [Full text]

Solar trends and global warming – Benestad & Schmidt (2009) “We use a suite of global climate model simulations for the 20th century to assess the contribution of solar forcing to the past trends in the global mean temperature. … We also demonstrate that the methodologies used by Scafetta and West (2005, 2006a, 2006b, 2007, 2008) are not robust to these same factors and that their error bars are significantly larger than reported. Our analysis shows that the most likely contribution from solar forcing a global warming is 7 ± 1% for the 20th century and is negligible for warming since 1980.” [Full text]

Total solar irradiance variability: What have we learned about its variability from the record of the last three solar cycles? – Fröhlich (2009) “Presently, there are three TSI composites available, called PMOD, ACRIM and IRMB, which are all constructed from the same original data, but use different procedures to correct for sensitivity changes. The PMOD composite is the only one which also corrects the early HF data for degradation. The origin of the differences between the three composite are discussed by comparison with the record of ERBE.” [Full text]

Recent changes in solar outputs and the global mean surface temperature. III. Analysis of contributions to global mean air surface temperature rise – Lockwood (2008) “It is shown that the contribution of solar variability to the temperature trend since 1987 is small and downward; the best estimate is −1.3% and the 2σ confidence level sets the uncertainty range of −0.7 to −1.9%. The result is the same if one quantifies the solar variation using galactic cosmic ray fluxes (for which the analysis can be extended back to 1953) or the most accurate total solar irradiance data composite.” [Full text]

Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature. II. Different reconstructions of the total solar irradiance variation and dependence on response time scale – Lockwood & Fröhlich (2008) “Use of the ACRIM composite, which shows a rise in TSI over recent decades, is shown to be inconsistent with most published evidence for solar influences on pre-industrial climate. The conclusions of our previous paper, that solar forcing has declined over the past 20 years while surface air temperatures have continued to rise, are shown to apply for the full range of potential time constants for the climate response to the variations in the solar forcings.” [Full text]

Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature – Lockwood & Fröhlich (2007) “Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth’s climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.” [Full text]

Variations in solar luminosity and their effect on the Earth’s climate – Foukal et al. (2006) “In this Review, we show that detailed analysis of these small output variations has greatly advanced our understanding of solar luminosity change, and this new understanding indicates that brightening of the Sun is unlikely to have had a significant influence on global warming since the seventeenth century.” [Full text]

A review of the solar cycle length estimates – Benestad (2005) “There have been speculations about an association between the solar cycle length and Earth’s climate, however, the solar cycle length analysis does not follow Earth’s global mean surface temperature. A further comparison with the monthly sunspot number, cosmic galactic rays and 10.7 cm absolute radio flux since 1950 gives no indication of a systematic trend in the level of solar activity that can explain the most recent global warming.”

Can solar variability explain global warming since 1970? – Solanki & Krivova (2003) “The solar records are scaled such that statistically the solar contribution to climate is as large as possible in this period. Under this assumption we repeat the comparison but now including the period 1970–1999. This comparison shows without requiring any recourse to modeling that since roughly 1970 the solar influence on climate (through the channels considered here) cannot have been dominant. In particular, the Sun cannot have contributed more than 30% to the steep temperature increase that has taken place since then, irrespective of which of the three considered channels is the dominant one determining Sun-climate interactions: tropospheric heating caused by changes in total solar irradiance, stratospheric chemistry influenced by changes in the solar UV spectrum, or cloud coverage affected by the cosmic ray flux.” [Full text]

The Sun’s Role in Climate Variations – Rind (2002) A review paper. “Is the Sun the controller of climate changes, only the instigator of changes that are mostly forced by the system feedbacks, or simply a convenient scapegoat for climate variations lacking any other obvious cause? This question is addressed for suggested solar forcing mechanisms operating on time scales from billions of years to decades. Each mechanism fails to generate the expected climate response in important respects, although some relations are found. The magnitude of the system feedbacks or variability appears as large or larger than that of the solar forcing, making the Sun’s true role ambiguous.” [Full text]

The effects of solar variability on the Earth’s climate – Haigh (2002) A review paper. “Observational data suggest that the Sun has influenced temperatures on decadal, centennial and millennial time-scales, but radiative forcing considerations and the results of energy-balance models and general circulation models suggest that the warming during the latter part of the 20th century cannot be ascribed entirely to solar effects.” [Full text]

The Sun’s total irradiance: Cycles, trends and related climate change uncertainties since 1976 – Fröhlich & Lean (1998) “A composite record of the Sun’s total irradiance compiled from measurements made by five independent space‐based radiometers since 1978 exhibits a prominent 11‐year cycle with similar levels during 1986 and 1996, the two most recent minimum epochs of solar activity. This finding contradicts recent assertions of a 0.04% irradiance increase from the 1986 to 1996 solar minima and suggests that solar radiative output trends contributed little of the 0.2°C increase in the global mean surface temperature in the past decade.” [Full text]

Dependence of global temperatures on atmospheric CO2 and solar irradiance – Thomson (1997) “I estimate transfer functions from changes in atmospheric CO2 and from changes in solar irradiance to hemispheric temperatures that have been corrected for the effects of precession. They show that changes from CO2 over the last century are about three times larger than those from changes in solar irradiance. The increase in global average temperature during the last century is at least 20 times the SD of the residual temperature series left when the effects of CO2 and changes in solar irradiance are subtracted.” [Full text]

The Seasons, Global Temperature, and Precession – Thomson (1995) “Coherence between changes in the amplitude of the annual cycle and those in the average temperature show that between 1854 and 1922 there were small temperature variations, probably of solar origin. Since 1922, the phase of the Northern Hemisphere coherence between these quantities switched from 0° to 180° and implies that solar variability cannot be the sole cause of the increasing temperature over the last century. About 1940, the phase patterns of the previous 300 years began to change and now appear to be changing at an unprecedented rate. The average change in phase is now coherent with the logarithm of atmospheric CO2 concentration.”

Closely related

Papers on the insignificant role of cosmic rays in climate.

There are also many papers suggesting stronger role for the Sun in recent climate change, such as Scafetta & West (2006) included in Nils Simon’s collection, which contains also some other papers not listed here.

Update history

UPDATE (November 16, 2011): Love et al. (2011) added.
UPDATE (October 15, 2010): Haigh et al. (2010) added. Thanks to Barry for pointing it out, see the comment section below.
UPDATE (April 11, 2010): Thomson (1995) and Thomson (1997) added.
UPDATE (March 9, 2010): Lean (2009) added, thanks to PeterPan for pointing it out, see the comment section below.
UPDATE (February 19, 2010): Lockwood (2009) is now Lockwood (2010) because it wasn’t officially published until now.
UPDATE (January 14, 2010): Lockwood (2009) added, thanks to Matti for pointing it out.
UPDATE (December 15, 2009): Full text link to Benestad & Schmidt (2009) added, thanks to PeterPan for pointing it out, see the comment section below.
UPDATE (December 9, 2009): Benestad & Schmidt (2009) added.
UPDATE (October 26, 2009): Benestad (2005) added. Thanks to PeterPan for pointing it out, see the comment section below.
UPDATE (September 15, 2009): Some time ago I added Foukal et al. (2006) but forgot to make the update note about it. Nils Simon pointed out his collection of papers (thanks Nils) where I found this paper. I also added a note in the “closely related” section.

Posted in AGW evidence | 19 Comments »

 
%d bloggers like this: