Papers on polar ice sheets

This is a list of papers on the modern observations of Greenland and Antarctic ice sheets. 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 (November 25, 2009): Chen et al. (2009) added, thanks to John Cook for pointing it out, see the comment section below.

Polar ice sheets

Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE – Velicogna (2009) “We use monthly measurements of time-variable gravity from the GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission to determine the ice mass-loss for the Greenland and Antarctic Ice Sheets during the period between April 2002 and February 2009. We find that during this time period the mass loss of the ice sheets is not a constant, but accelerating with time, i.e., that the GRACE observations are better represented by a quadratic trend than by a linear one, implying that the ice sheets contribution to sea level becomes larger with time. In Greenland, the mass loss increased from 137 Gt/yr in 2002–2003 to 286 Gt/yr in 2007–2009, i.e., an acceleration of −30 ± 11 Gt/yr2 in 2002–2009. In Antarctica the mass loss increased from 104 Gt/yr in 2002–2006 to 246 Gt/yr in 2006–2009, i.e., an acceleration of −26 ± 14 Gt/yr2 in 2002–2009.” [Link to PDF]

Recent Sea-Level Contributions of the Antarctic and Greenland Ice Sheets – Shepherd & Wingham (2007) A review article. “As global temperatures have risen, so have rates of snowfall, ice melting, and glacier flow. Although the balance between these opposing processes has varied considerably on a regional scale, data show that Antarctica and Greenland are each losing mass overall. Our best estimate of their combined imbalance is about 125 gigatons per year of ice, enough to raise sea level by 0.35 millimeters per year.” [Link to PDF]

Interannual variations of the mass balance of the Antarctica and Greenland ice sheets from GRACE – Ramillien et al. (2006) “We use new GRACE geoid solutions provided by the Groupe de Recherche en Géodésie Spatiale (GRGS/CNES), at the resolution of ~400 km and sampled at 10-day interval. In the three regions, significant interannual variations are observed, which we approximate as linear trends over the short time span of analysis. Over Greenland, an apparent total volume loss of 119 +/− 10 cu km/yr water is observed. For the Antarctica ice sheet, a bimodal behaviour is apparent, with volume loss amounting to 88 +/− 10 cu km/yr water in the West, and increase in the East amounting to 72 +/− 20 cu km/yr water.” [Link to PDF]

Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002 – Zwally et al. (2005) “Changes in ice mass are estimated from elevation changes derived from 10.5 years (Greenland) and 9 years (Antarctica) of satellite radar altimetry data from the European Remote-sensing Satellites ERS-1 and -2. … The Greenland ice sheet is thinning at the margins (−42 ± 2 Gt a⁻¹ below the equilibrium-line altitude (ELA)) and growing inland (+53 ± 2 Gt a⁻¹ above the ELA) with a small overall mass gain (+11 ± 3 Gt a⁻¹; −0.03 mm a⁻¹ SLE (sea-level equivalent)). The ice sheet in West Antarctica (WA) is losing mass (−47 ± 4 Gt a⁻¹) and the ice sheet in East Antarctica (EA) shows a small mass gain (+16 ± 11 Gt a⁻¹) for a combined net change of −31 ± 12 Gt a⁻¹ (+0.08 mm a⁻¹ SLE).” [Link to PDF]

Mass Balance of Polar Ice Sheets – Rignot & Thomas (2002) “Recent advances in the determination of the mass balance of polar ice sheets show that the Greenland Ice Sheet is losing mass by near-coastal thinning, and that the West Antarctic Ice Sheet, with thickening in the west and thinning in the north, is probably thinning overall.” [Link to PDF]

Greenland ice sheet

Large and Rapid Melt-Induced Velocity Changes in the Ablation Zone of the Greenland Ice Sheet – van de Wal et al. (2008) “Continuous Global Positioning System observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the Greenland Ice Sheet. Within days, ice velocity reacts to increased meltwater production and increases by a factor of 4. Such a response is much stronger and much faster than previously reported. Over a longer period of 17 years, annual ice velocities have decreased slightly, which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input, which results in a more or less constant ice flux over the years.” [Link to PDF]

Seasonal Speedup Along the Western Flank of the Greenland Ice Sheet – Joughin et al. (2008) “It has been widely hypothesized that a warmer climate in Greenland would increase the volume of lubricating surface meltwater reaching the ice-bedrock interface, accelerating ice flow and increasing mass loss. We have assembled a data set that provides a synoptic-scale view, spanning ice-sheet to outlet-glacier flow, with which to evaluate this hypothesis. On the ice sheet, these data reveal summer speedups (50 to 100%) consistent with, but somewhat larger than, earlier observations. The relative speedup of outlet glaciers, however, is far smaller (<15%). Furthermore, the dominant seasonal influence on Jakobshavn Isbrae's flow is the calving front's annual advance and retreat. With other effects producing outlet-glacier speedups an order of magnitude larger, seasonal melt's influence on ice flow is likely confined to those regions dominated by ice-sheet flow."

Changes in the Velocity Structure of the Greenland Ice Sheet – Rignot & Kanagaratnam (2006) “Using satellite radar interferometry observations of Greenland, we detected widespread glacier acceleration below 66° north between 1996 and 2000, which rapidly expanded to 70° north in 2005. Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year. As more glaciers accelerate farther north, the contribution of Greenland to sea-level rise will continue to increase.”

Satellite Gravity Measurements Confirm Accelerated Melting of Greenland Ice Sheet – Chen et al. (2006) “Using time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, we estimate ice mass changes over Greenland during the period April 2002 to November 2005. After correcting for the effects of spatial filtering and limited resolution of GRACE data, the estimated total ice melting rate over Greenland is –239 ± 23 cubic kilometers per year, mostly from East Greenland. This estimate agrees remarkably well with a recent assessment of –224 ± 41 cubic kilometers per year, based on satellite radar interferometry data. GRACE estimates in southeast Greenland suggest accelerated melting since the summer of 2004, consistent with the latest remote sensing measurements.” [Link to PDF]

Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow – Zwally et al. (2002) “The near coincidence of the ice acceleration with the duration of surface melting, followed by deceleration after the melting ceases, indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice-bedrock interface. … The indicated coupling between surface melting and ice-sheet flow provides a mechanism for rapid, large-scale, dynamic responses of ice sheets to climate warming.” [Link to PDF]

Antarctic ice sheet

Accelerated Antarctic ice loss from satellite gravity measurements – Chen et al. (2009) “The Gravity Recovery and Climate Experiment⁵ (GRACE) offers the opportunity of quantifying polar ice-sheet mass balance from a different perspective^{6, 7}. Here we use an extended record of GRACE data spanning the period April 2002 to January 2009 to quantify the rates of Antarctic ice loss. In agreement with an independent earlier assessment⁴, we estimate a total loss of 190±77 Gt yr^-1, with 132±26 Gt yr^-1 coming from West Antarctica. However, in contrast with previous GRACE estimates, our data suggest that East Antarctica is losing mass, mostly in coastal regions, at a rate of -57±52 Gt yr^-1, apparently caused by increased ice loss since the year 2006.”

West Antarctic Ice Sheet collapse – the fall and rise of a paradigm – Vaughan (2008) “It is now almost 30 years since John Mercer (1978) first presented the idea that climate change could eventually cause a rapid deglaciation, or “collapse,” of a large part of the West Antarctic ice sheet (WAIS), raising world sea levels by 5 m and causing untold economic and social impacts. … Through the 1990s, however, a lack of observational evidence for ongoing retreat in WAIS and improved understanding of the complex dynamics of ice streams meant that estimates of likelihood of collapse seemed to be diminishing. In the last few years, however, satellite studies over the relatively inaccessible Amundsen Sea sector of West Antarctica have shown clear evidence of ice sheet retreat showing all the features that might have been predicted for emergent collapse. … Since much of WAIS appears to be unchanging, it may, no longer be reasonable to suggest there is an imminent threat of a 5-m rise in sea level resulting from complete collapse of the West Antarctic ice sheet, but there is strong evidence that the Amundsen Sea embayment is changing rapidly. This area alone, contains the potential to raise sea level by around ~1.5 m, but more importantly it seems likely that it could, alter rapidly enough, to make a significant addition to the rate of sea-level rise over coming two centuries.”

Measurements of Time-Variable Gravity Show Mass Loss in Antarctica – Velicogna & Wahr (2006) “Using measurements of time-variable gravity from the Gravity Recovery and Climate Experiment satellites, we determined mass variations of the Antarctic ice sheet during 2002–2005. We found that the mass of the ice sheet decreased significantly, at a rate of 152 ± 80 cubic kilometers of ice per year, which is equivalent to 0.4 ± 0.2 millimeters of global sea-level rise per year. Most of this mass loss came from the West Antarctic Ice Sheet.” [Link to PDF]

Mass balance of the Antarctic ice sheet – Wingham et al. (2006) “Here, we use satellite radar altimetry to measure the elevation change of 72% of the grounded ice sheet during the period 1992–2003. Depending on the density of the snow giving rise to the observed elevation fluctuations, the ice sheet mass trend falls in the range −5-+85 Gt yr⁻¹. … Mass gains from accumulating snow, particularly on the Antarctic Peninsula and within East Antarctica, exceed the ice dynamic mass loss from West Antarctica.” [Link to PDF]

Widespread Complex Flow in the Interior of the Antarctic Ice Sheet – Bamber et al. (2000) “It has been suggested that as much as 90% of the discharge from the Antarctic Ice Sheet is drained through a small number of fast-moving ice streams and outlet glaciers fed by relatively stable and inactive catchment areas. Here, evidence obtained from balance velocity estimates suggests that each major drainage basin is fed by complex systems of tributaries that penetrate up to 1000 kilometers from the grounding line into the interior of the ice sheet.” [Link to PDF]

Satellite Radar Interferometry for Monitoring Ice Sheet Motion: Application to an Antarctic Ice Stream – Goldstein et al. (1993) “The SRI velocities and grounding line of the Rutford Ice Stream, Antarctica, agree fairly well with earlier ground-based data. The combined use of SRI and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior.” [Link to PDF]

West Antarctic ice sheet and CO₂ greenhouse effect: a threat of disaster – Mercer (1978) Not an observational paper but is included here because it seems to be a classic on this subject. “If the global consumption of fossil fuels continues to grow at its present rate, atmospheric CO₂ content will double in about 50 years. Climatic models suggest that the resultant greenhouse-warming effect will be greatly magnified in high latitudes. The computed temperature rise at lat 80° S could start rapid deglaciation of West Antarctica, leading to a 5 m rise in sea level.” [Link to PDF]

Papers on reconstructions of modern temperatures

This is a list of papers on proxy based reconstructions of modern temperatures with emphasis on global and semi-global analyses. “Modern” here refers to last couple of thousands of years. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

On the reliability of millennial reconstructions of variations in surface air temperature in the Northern Hemisphere – Datsenko & Sonechkin (2008) “The reliability of the recently published reconstructions of the surface air temperature variability in the Northern Hemisphere over the past 2000 yr is discussed. For this purpose, the power spectra of the two best known reconstructions (Mann et al.[10–12] and Moberg et al. [13]) are calculated and compared to the spectra of the 150-yr temperature series based on instrumental observations and simulated 1000-yr series. It is found that the Mann et al. reconstruction drastically underestimates low-frequency temperature variations, whereas the Moberg et al. reconstruction reproduces them much better, although with a certain underestimation rather than overestimation, as Mann et al. have recently argued.”

Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia – Mann et al. (2008) “Following the suggestions of a recent National Research Council report [NRC (National Research Council) (2006) Surface Temperature Reconstructions for the Last 2,000 Years (Natl Acad Press, Washington, DC).], we reconstruct surface temperature at hemispheric and global scale for much of the last 2,000 years using a greatly expanded set of proxy data for decadal-to-centennial climate changes, recently updated instrumental data, and complementary methods that have been thoroughly tested and validated with model simulation experiments. Our results extend previous conclusions that recent Northern Hemisphere surface temperature increases are likely anomalous in a long-term context. Recent warmth appears anomalous for at least the past 1,300 years whether or not tree-ring data are used.” [Link to PDF]

Millennial temperature reconstruction intercomparison and evaluation – Juckes et al. (2007) “Here recent work is reviewed and some new calculations performed with an aim to clarifying the consequences of the different approaches used. A range of proxy data collections introduced by different authors is used to estimate Northern Hemispheric annual mean temperatures with two reconstruction algorithms: (1) inverse regression and, (2) compositing followed by variance matching (CVM). … A reconstruction using 13 proxy records extending back to AD 1000 shows a maximum pre-industrial temperature of 0.25 K (relative to the 1866 to 1970 mean). The standard error on this estimate, based on the residual in the calibration period, is 0.14 K. Instrumental temperatures for two recent years (1998 and 2005) have exceeded the pre-industrial estimated maximum by more than 4 standard deviations of the calibration period residual.” [Link to PDF]

Climate sensitivity constrained by temperature reconstructions over the past seven centuries – Hegerl et al. (2006) “A number of observational studies, however, find a substantial probability of significantly higher sensitivities, yielding upper limits on climate sensitivity of 7.7 K to above 9 K (refs 3–8). Here we demonstrate that such observational estimates of climate sensitivity can be tightened if reconstructions of Northern Hemisphere temperature over the past several centuries are considered. … After accounting for the uncertainty in reconstructions and estimates of past external forcing, we find an independent estimate of climate sensitivity that is very similar to those from instrumental data. If the latter are combined with the result from all proxy reconstructions, then the 5–95 per cent range shrinks to 1.5–6.2 K, thus substantially reducing the probability of very high climate sensitivity.” [Link to PDF]

Extracting a Climate Signal from 169 Glacier Records – Oerlemans et al. (2005) “I constructed a temperature history for different parts of the world from 169 glacier length records. Using a first-order theory of glacier dynamics, I related changes in glacier length to changes in temperature. … Moderate global warming started in the middle of the 19th century. The reconstructed warming in the first half of the 20th century is 0.5 kelvin.” [Link to PDF]

Proxy-Based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Method, Predictor Network, Target Season, and Target Domain – Rutherford et al. (2005) “Results are presented from a set of experiments designed to investigate factors that may influence proxy-based reconstructions of large-scale temperature patterns in past centuries. … The comparisons demonstrate dependence of reconstructions on seasonal, spatial, and methodological considerations, emphasizing the primary importance of the target region and seasonal window of the reconstruction.” [Link to PDF]

Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data – Moberg et al. (2005) “Here we reconstruct Northern Hemisphere temperatures for the past 2,000 years by combining low-resolution proxies with tree-ring data, using a wavelet transform technique11 to achieve timescale-dependent processing of the data. … According to our reconstruction, high temperatures—similar to those observed in the twentieth century before 1990—occurred around ad 1000 to 1100, and minimum temperatures that are about 0.7 K below the average of 1961–90 occurred around ad 1600.” [Link to PDF] [Their own 2008-paper that criticises this work]

Borehole climate reconstructions: Spatial structure and hemispheric averages – Pollack & Smerdon (2004) “Ground surface temperature (GST) reconstructions determined from temperature profiles measured in terrestrial boreholes, when averaged over the Northern Hemisphere, estimate a surface warming of ∼1 K during the interval AD 1500–2000. Other traditional proxy-based estimates suggest less warming during the same interval. … We demonstrate the consistency of GST warming estimates by showing that over a wide range of grid element area and occupancy weighting schemes, the five-century GST change falls in the range of 0.89–1.05 K. … Reconstructions assembled after excluding low-occupancy grid elements show a five-century GST change in the range of 1.02–1.06 K.” [Link to PDF]

Climate over past millennia – Jones & Mann (2004) “We review evidence for climate change over the past several millennia from instrumental and high-resolution climate “proxy” data sources and climate modeling studies. … We devote particular attention to proxy-based reconstructions of temperature patterns in past centuries, which place recent large-scale warming in an appropriate longer-term context. Our assessment affirms the conclusion that late 20th century warmth is unprecedented at hemispheric and, likely, global scales.” [Link to PDF]

Global surface temperatures over the past two millennia – Mann & Jones (2003) “We present reconstructions of Northern and Southern Hemisphere mean surface temperature over the past two millennia based on high-resolution ‘proxy’ temperature data which retain millennial-scale variability. These reconstructions indicate that late 20th century warmth is unprecedented for at least roughly the past two millennia for the Northern Hemisphere.” [Link to PDF]

Low-frequency temperature variations from a northern tree ring density network – Briffa et al. (2001) “We describe new reconstructions of northern extratropical summer temperatures for nine subcontinental-scale regions and a composite series representing quasi “Northern Hemisphere” temperature change over the last 600 years. … The 20th century is clearly shown by all of the palaeoseries composites to be the warmest during this period.” [Link to PDF]

Temperature trends over the past five centuries reconstructed from borehole temperatures – Huang et al. (2000) “Here we use present-day temperatures in 616 boreholes from all continents except Antarctica to reconstruct century-long trends in temperatures over the past 500 years at global, hemispheric and continental scales. The results confirm the unusual warming of the twentieth century revealed by the instrumental record6, but suggest that the cumulative change over the past five centuries amounts to about 1 K, exceeding recent estimates from conventional climate proxies.” [Link to PDF]

Annual climate variability in the Holocene: interpreting the message of ancient trees – Briffa (2000) “As for assessing the significance of 20th century global warming, the evidence from dendroclimatology in general, supports the notion that the last 100 years have been unusually warm, at least within a context of the last two millennia. However, this evidence should not be considered equivocal. The activities of humans may well be impacting on the ‘natural’ growth of trees in different ways, making the task of isolating a clear climate message subtly difficult.” [Link to PDF]

Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations – Mann et al. (1999) “Building on recent studies, we attempt hemispheric temperature reconstructions with proxy data networks for the past millennium. We focus not just on the reconstructions, but the uncertainties therein, and important caveats. Though expanded uncertainties prevent decisive conclusions for the period prior to AD 1400, our results suggest that the latter 20th century is anomalous in the context of at least the past millennium. The 1990s was the warmest decade, and 1998 the warmest year, at moderately high levels of confidence. The 20th century warming counters a millennial‐scale cooling trend which is consistent with long‐term astronomical forcing.” [Link to PDF]

Global-scale temperature patterns and climate forcing over the past six centuries – Mann et al. (1998) “Spatially resolved global reconstructions of annual surface temperature patterns over the past six centuries are based on the multivariate calibration of widely distributed high-resolution proxy climate indicators. Time-dependent correlations of the reconstructions with time-series records representing changes in greenhouse-gas concentrations, solar irradiance, and volcanic aerosols suggest that each of these factors has contributed to the climate variability of the past 400 years, with greenhouse gases emerging as the dominant forcing during the twentieth century. Northern Hemisphere mean annual temperatures for three of the past eight years are warmer than any other year since (at least) ad 1400.” [Link to PDF]

High-resolution palaeoclimatic records for the last millennium: interpretation, integration and comparison with General Circulation Model control-run temperatures – Jones et al. (1998) “We have averaged 17 temperature reconstructions (representing various seasons of the year), all extending back at least to the mid-seventeenth century, to form two annually resolved hemispheric series (NH10 and SH7). … The coldest year of the millennium over the NH is ad 1601, the coldest decade 1691–1700 and the seventeenth is the coldest century.” [Link to PDF]

Influence of volcanic eruptions on Northern Hemisphere summer temperature over the past 600 years – Briffa et al. (1998) “Here we use this well dated, high-resolution composite time-series to suggest that large explosive volcanic eruptions produced different extents of Northern Hemisphere cooling during the past 600 years. The large effect of some recent eruptions is apparent, such as in 1816, 1884 and 1912, but the relative effects of other known, and perhaps some previously unknown, pre-nineteenth-century eruptions are also evaluated. The most severe short-term Northern Hemisphere cooling event of the past 600 years occurred in 1601, suggesting that either the effect on climate of the eruption of Huaynaputina, Peru, in 1600 has previously been greatly underestimated, or another, as yet unidentified, eruption occurred at the same time.”

‘Little Ice Age’ summer temperature variations: their nature and relevance to recent global warming trends – Bradley & Jones (1993) “Using historical, tree-ring and ice core data, we examine climatic variations during the period commonly called the ‘Little Ice Age’. The coldest conditions of the last 560 years were between AD 1570 and 1730, and in the nineteenth century. Unusually warm conditions have prevailed since the 1920s, probably related to a relative absence of major explosive volcanic eruptions and higher levels of greenhouse gases.”

Closely related

Papers on the MWP as Global Event

Papers on the iris hypothesis of Lindzen

This is a list of papers on the iris hypothesis of Lindzen. The list contains only papers that concentrate on the iris hypothesis, so there’s no such papers that study related matters but only mention the hypothesis in passing. 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 (November 18, 2009): Earth Observatory article added to the “closely related” section, thanks to Paul Middents for pointing it out (see the comment section below).

Papers of others

An Evaluation of the Proposed Mechanism of the Adaptive Infrared Iris Hypothesis Using TRMM VIRS and PR Measurements – Rapp et al. (2005) “This [iris] hypothesis assumes that increased precipitation efficiency in regions of higher sea surface temperatures will reduce cirrus detrainment. Tropical Rainfall Measuring Mission (TRMM) satellite measurements are used here to investigate the adaptive infrared iris hypothesis. … The current analysis does not show any significant SST dependence of the ratio of cloud area to surface rainfall for deep convection in the tropical western and central Pacific.” [Link to PDF]

Examination of the Decadal Tropical Mean ERBS Nonscanner Radiation Data for the Iris Hypothesis – Lin et al. (2004) “In this study, the ERBS decadal observations are compared with the predictions of the Iris hypothesis using 3.5-box model. … On the decadal time scale, the predicted tropical mean radiative flux anomalies are generally significantly different from those of the ERBS measurements, suggesting that the decadal ERBS nonscanner radiative energy budget measurements do not support the strong negative feedback of the Iris effect.” [Link to PDF]

The decadal tropical mean radiation data and the Iris hypothesis – Lin et al. (2003) A conference paper. “This study examines the evidence of the strong negative climate feedback of the Iris hypothesis using decadal satellite observations of tropical mean radiative energy budget anomalies, and finds that the decadal satellite measurements do not support the Iris effect.”

Examination of New CERES Data for Evidence of Tropical Iris Feedback – Chambers et al. (2002) “New data products from the Clouds and the Earth’s Radiant Energy System (CERES) instrument on the Tropical Rainfall Measuring Mission Satellite have been examined in the context of the recently proposed adaptive tropical infrared Iris hypothesis. … Regardless of definition, the radiative properties are found to be different from those assigned in the original Iris hypothesis. As a result, the strength of the feedback effect is reduced by a factor of 10 or more. Contrary to the initial Iris hypothesis, most of the definitions tested in this paper result in a small positive feedback. Thus, the existence of an effective infrared iris to counter greenhouse warming is not supported by the CERES data.”

New CERES Data Examined for Evidence of Tropical Iris Feedback – Chambers et al. (2002) A conference paper. “New data products are available from the CERES instrument, a part of the NASA Earth Observing System. … Regardless, the current results show that the proposed Iris feedback is very much weaker when objectively-determined radiative properties are used in the model.” [Link to PDF]

Reply – Chambers et al. (2002) “Chou et al. (2002, hereinafter CLH) argue in their comment that the way in which Lin et al. (2002) analyzed the Clouds and the Earth’s Radiant Energy System (CERES) data (Wielicki et al. 1996) is not appropriate. … The analysis in the Lin et al. paper exactly followed the original iris idea, as presented by Lindzen et al. (2001, hereinafter LCH), yet obtained significantly different results. We have repeated the analysis with some additional thresholds as illustrated in the CLH comment, and our basic conclusion remains: the difference between the net radiative fluxes of the cloudy-moist and clear-moist regions should be small. Thus, the radiative forcing resulting from a change in tropical high cloud amount is still about 1/10 of that found in LCH.” [Link to PDF]

Climatic Properties of Tropical Precipitating Convection under Varying Environmental Conditions – Del Genio & Kovari (2002) “A clustering algorithm is used to define the radiative, hydrological, and microphysical properties of precipitating convective events in the equatorial region observed by the Tropical Rainfall Measuring Mission (TRMM) satellite. … The adaptive iris hypothesis (clouds thinning with warming) is clearly not supported by the TRMM data. … Several flaws in reasoning lead Lindzen et al. (2001) to their conclusion.” [Link to PDF]

Tropical cirrus and water vapor: an effective Earth infrared iris feedback? – Fu et al. (2002) “We argue that the water vapor feedback is overestimated in Lindzen et al. (2001) by at least 60%, and that the high cloud feedback is small. Although not mentioned by Lindzen et al. (2001), tropical low clouds make a significant contribution to their negative feedback, which is also overestimated. Using more realistic parameters in the model of Lindzen et al. (2001), we obtain a feedback factor in the range of -0.15 to -0.51, compared to their larger negative feedback factor of -0.45 to -1.03. It is noted that our feedback factor could still be overestimated due to the assumption of constant low cloud cover in the simple radiative-convective model.” [Link to PDF]

The Iris Hypothesis: A Negative or Positive Cloud Feedback? – Lin et al. (2002) “Using the Tropical Rainfall Measuring Mission (TRMM) satellite measurements over tropical oceans, this study evaluates the iris hypothesis recently proposed by Lindzen et al. that tropical upper-tropospheric anvils act as a strong negative feedback in the global climate system. … The observations show that the clouds have much higher albedos and moderately larger longwave fluxes than those assumed by Lindzen et al. As a result, decreases in these clouds would cause a significant but weak positive feedback to the climate system, instead of providing a strong negative feedback.” [Link to PDF]

Comments on “Does the Earth Have an Adaptive Infrared Iris?” – Harrison (2002) Finds much smaller value for fractional cloud-cover decrease per °C than Lindzen et al. (2001). [Link to PDF]

No Evidence for Iris – Hartmann & Michelsen (2002) “It is shown that the negative correlation between cloud-weighted sea surface temperature (SST) and high cloud fraction discussed recently by Lindzen et al. results from variations in subtropical clouds that are not physically connected to the deep convection near the equator. A negative correlation between cloud-weighted SST and average cloud fraction results from any variation in cloud fraction over the areas with lower SSTs within the domain of interest. Therefore, this correlation is not evidence that tropical cloud anvil area is inversely proportional to sea surface temperature and should not be used to infer the existence of a negative feedback in the climate system.” [Link to PDF]

Papers of Lindzen et al.

Comments on “Examination of the Decadal Tropical Mean ERBS Nonscanner Radiation Data for the Iris Hypothesis” – Chou & Lindzen (2005)

Further Results On The Iris Effect – Lindzen et al. (2002) A conference paper. “Our data set now extends to 4 full years rather than the 20 months used in the original study. … We have used CERES data in order to investigate how albedo varies with area of cirrus (scaled by cumulus activity) in order to separate the albedo change due to fluctuations of cirrus areas from mean albedos which are biased by the high albedos associated with thick anvils near cumulus cores. It is, of course, the former which are relevant to the feedback. Results from each of the above studies will be presented.”

Comment on “No Evidence for Iris” – Lindzen et al. (2002) “However, the points raised by HM hardly constitute challenges to the hypothesis.” [Link to PDF]

Comments on “The Iris Hypothesis: A Negative or Positive Cloud Feedback?” – Chou et al. (2002) “The difference in the feedback factor is due to a larger contrast in albedos and a smaller contrast in the outgoing longwave radiation (OLR) between the high-level cloudy region and the surrounding regions as derived by Lin et al. when compared with that specified in LCH. It appears that the approach taken by Lin et al. to estimate the albedo and OLR is not appropriate and that the inferred climate sensitivity is unreliable.” [Link to PDF]

Does the Earth Have an Adaptive Infrared Iris? – Lindzen et al. (2001) “Motivated by the observed relation between cloudiness (above the trade wind boundary layer) and high humidity, cloud data for the eastern part of the western Pacific from the Japanese Geostationary Meteorological Satellite–5 (which provides high spatial and temporal resolution) have been analyzed, and it has been found that the area of cirrus cloud coverage normalized by a measure of the area of cumulus coverage decreases about 22% per degree Celsius increase in the surface temperature of the cloudy region. … This new mechanism would, in effect, constitute an adaptive infrared iris that opens and closes in order to control the Outgoing Longwave Radiation in response to changes in surface temperature in a manner similar to the way in which an eye’s iris opens and closes in response to changing light levels.” [Link to PDF]

Closely related

Earth Observatory: Arbiters of Energy A lay people level review of the issue.

Papers on carbon cycle feedback

This is a list of papers on carbon cycle feedback. Note that the list is not only observational papers, there are modelling papers also. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Quantifying Carbon Cycle Feedbacks – Gregory et al. (2009) “This paper demonstrates how carbon cycle feedback can be expressed in formally similar ways to climate feedback, and thus compares their magnitudes. The carbon cycle gives rise to two climate feedback terms: the concentration–carbon feedback, resulting from the uptake of carbon by land and ocean as a biogeochemical response to the atmospheric CO₂ concentration, and the climate–carbon feedback, resulting from the effect of climate change on carbon fluxes. In the earth system models of the Coupled Climate–Carbon Cycle Model Intercomparison Project (C4MIP), climate–carbon feedback on warming is positive and of a similar size to the cloud feedback. The concentration–carbon feedback is negative; it has generally received less attention in the literature, but in magnitude it is 4 times larger than the climate–carbon feedback and more uncertain.”

A revised estimate of the processes contributing to global warming due to climate-carbon feedback – Cadule et al. (2009) “We show here that, because of the specific spatial and temporal distribution of the radiative forcing exerted by those external perturbations, the temperature gains are all different. Based on our revised method, we found that, for the SRES A2 scenario, the projected global warming in 2100, due to increases in atmospheric CO₂, non-CO₂ GHGs and anthropogenic sulphate aerosols, is 2.3–5.6°C. This is accidentally nearly equal to the original one of Meehl et al. (2007) (2.4–5.6°C).”

What determines the magnitude of carbon cycle-climate feedbacks? – Matthews et al. (2007) “In this study, we use a coupled climate-carbon model to investigate how the response of vegetation photosynthesis to climate change contributes to the overall strength of carbon cycle-climate feedbacks. We find that the feedback strength is particularly sensitive to the model representation of the photosynthesis-temperature response, with lesser sensitivity to the parameterization of soil moisture and nitrogen availability. In all simulations, large feedbacks are associated with a climatic suppression of terrestrial primary productivity and consequent reduction of terrestrial carbon uptake.” [Link to PDF]

Terrestrial Carbon–Cycle Feedback to Climate Warming – Luo (2007) A review article. “Nonetheless, experimental results are so variable that we have not generated the necessary insights on ecosystem responses to effectively improve global models. To constrain model projections of carbon-climate feedbacks, we need more empirical data from whole-ecosystem warming experiments across a wide range of biomes, particularly in tropic regions, and closer interactions between models and experiments.” [Link to PDF]

Climate–Carbon Cycle Feedback Analysis: Results from the C⁴MIP Model Intercomparison – Friedlingstein et al. (2006) “Eleven coupled climate–carbon cycle models used a common protocol to study the coupling between climate change and the carbon cycle. … There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic carbon perturbation. A larger fraction of anthropogenic CO₂ will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO₂ varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO₂ levels led to an additional climate warming ranging between 0.1° and 1.5°C.” [Link to PDF]

Positive feedback between global warming and atmospheric CO₂ concentration inferred from past climate change – Scheffer et al. (2006) “Here we present an alternative way of estimating the magnitude of the feedback effect based on reconstructed past changes. Linking this information with the mid-range Intergovernmental Panel on Climate Change estimation of the greenhouse gas effect on temperature we suggest that the feedback of global temperature on atmospheric CO₂ will promote warming by an extra 15–78% on a century-scale.” [Link to PDF]

Primary productivity control of simulated carbon cycle–climate feedbacks – Matthews et al. (2005) “In this study, we demonstrate that the response of vegetation primary productivity to climate changes is a critical controlling factor in determining the strength of simulated carbon cycle-climate feedbacks. This conclusion sheds new light on coupled climate-carbon cycle model results, and highlights the need for improved model representation of photosynthesis processes so as to better constrain future projections of climate change.”

How strong is carbon cycle-climate feedback under global warming? – Zeng et al. (2004) Thesis paper on modelling carbon cycle feedback. “The behavior of the coupled carbon cycle and physical climate system in a global warming scenario is studied using an Earth system model including the atmosphere, land, ocean, and the carbon cycle embedded in these components. … Results indicate a positive feedback to global warming from the interactive carbon cycle, with an additional increase of 90 ppmv in the atmospheric CO₂, and 0.6 degree additional warming, thus confirming recent results from the Hadley Centre and IPSL.” [Link to PDF]

Quantifying the effects of CO₂-fertilized vegetation on future global climate and carbon dynamics – Thompson et al. (2004) “In particular, the response of the land biosphere to the ongoing increase in atmospheric CO₂ is not well understood. To evaluate the approximate upper and lower limits of land carbon uptake, we perform simulations using a comprehensive climate-carbon model. … In a second case, CO₂ fertilization saturates in year 2000; here the land becomes an additional source of CO₂ by 2050. The predicted atmospheric CO₂ concentration at year 2100 differs by 40% between the two cases. We show that current uncertainties preclude determination of whether the land biosphere will amplify or damp atmospheric CO₂ increases by the end of the century.” [Link to PDF]

How positive is the feedback between climate change and the carbon cycle? – Friedlingstein et al. (2003) “Here we perform a detailed feedback analysis to show that such differences are due to two key processes that are still poorly constrained in these coupled models: first Southern Ocean circulation, which primarily controls the geochemical uptake of CO₂, and second vegetation and soil carbon response to global warming. Our analytical analysis reproduces remarkably the results obtained by the fully coupled models. Also it allows us to identify that, amongst the two processes mentioned above, the latter (the land response to global warming) is the one that essentially explains the differences between the IPSL and the Hadley results.” [Link to PDF]

Strong carbon cycle feedbacks in a climate model with interactive CO₂ and sulphate aerosols – Jones et al. (2003) “A climate change experiment is presented which uses a General Circulation Model (GCM) in which both interactive carbon and sulphur cycles have been included for the first time, along with the natural climate forcings due to solar changes and volcanic aerosol. … The additional forcings act to delay by more than a decade the conversion of the land carbon sink to a source, but ultimately result in a more abrupt rate of CO₂ increase with the land carbon source (which reaches 7 GtC yr^-1 by 2100) exceeding the ocean carbon sink (which saturates at 5 GtC yr^-1 by 2100) beyond about 2080.”

On the magnitude of positive feedback between future climate change and the carbon cycle – Dufresne et al. (2002) “We use an ocean-atmosphere general circulation model coupled to land and ocean carbon models to simulate the evolution of climate and atmospheric CO₂ from 1860 to 2100. … By 2100, we estimate that atmospheric CO₂ will be 18% higher due to the climate change impact on the carbon cycle. Such a positive feedback has also been found by Cox et al. [2000] . However, the amplitude of our feedback is three times smaller than the one they simulated. We show that the partitioning between carbon stored in the living biomass or in the soil, and their respective sensitivity to increased CO₂ and climate change largely explain this discrepancy.” [Link to PDF]

Positive feedback between future climate change and the carbon cycle – Friedlingstein et al. (2001) “Here, using climate and carbon three‐dimensional models forced by a 1% per year increase in atmospheric CO₂, we show that there is a positive feedback between the climate system and the carbon cycle. Climate change reduces land and ocean uptake of CO₂, respectively by 54% and 35% at 4 × CO₂. This negative impact implies that for prescribed anthropogenic CO₂ emissions, the atmospheric CO₂ would be higher than the level reached if climate change does not affect the carbon cycle. We estimate the gain of this climate‐carbon cycle feedback to be 10% at 2 × CO₂ and 20% at 4 × CO₂. This translates into a 15% higher mean temperature increase.”

Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model – Cox et al. (2000) “Here we present results from a fully coupled, three-dimensional carbon–climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a ‘business as usual’ scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr^-1 is balanced by the terrestrial carbon source, and atmospheric CO₂ concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback.” [Link to PDF]

Papers on glacier melting

This is a list of papers on melting glaciers with emphasis on global observational analysis and mass balance measurements. 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 (November 8, 2009): Few links added to the “closely related” section, thanks to mspelto for pointing them out, see the discussion section below. I also added Barry (2006).

Six decades of glacier mass-balance observations: a review of the worldwide monitoring network – Zemp et al. (2009) A review paper. “Six decades of annual mass-balance data have been compiled and made easily available by the World Glacier Monitoring Service and its predecessor organizations. In total, there have been 3480 annual mass-balance measurements reported from 228 glaciers around the globe. … The available data from the six decades indicate a strong ice loss as early as the 1940s and 1950s followed by a moderate mass loss until the end of the 1970s and a subsequent acceleration that has lasted until now, culminating in a mean overall ice loss of over 20 m w.e. for the period 1946-2006.” [Link to PDF]

After six decades of monitoring glacier mass balance we still need data but it should be richer data – Braithwaite (2009) A review paper (which in my opinion could have a better title). “However, 30 year series from 30 glaciers confirm a recent (1996-2005) trend to very negative mass balance after two decades of nearly zero mass balance.” [Link to PDF]

Glaciers Dominate Eustatic Sea-Level Rise in the 21st Century – Meier et al. (2007) “The contribution of these smaller glaciers has accelerated over the past decade, in part due to marked thinning and retreat of marine-terminating glaciers associated with a dynamic instability that is generally not considered in mass-balance and climate modeling. This acceleration of glacier melt may cause 0.1 to 0.25 meter of additional sea-level rise by 2100″

The status of research on glaciers and global glacier recession: a review – Barry (2006) A review paper. “Nevertheless, there has been substantial glacier retreat since the Little Ice Age and this has accelerated over the last two to three decades. Documenting these changes is hampered by the paucity of observational data. This review outlines the measurements that are available, new techniques that incorporate remotely sensed data, and major findings around the world. The focus is on changes in glacier area, rather than estimates of mass balance and volume changes that address the role of glacier melt in global sea-level rise.” [Link to PDF]

Mass balance of glaciers and ice caps: Consensus estimates for 1961–2004 – Kaser et al. (2006) “Working with comprehensive collections of directly-measured data on the annual mass balance of glaciers other than the two ice sheets, we combine independent analyses to show that there is broad agreement on the evolution of global mass balance since 1960. Mass balance was slightly below zero around 1970 and has been growing more negative since then. Excluding peripheral ice bodies in Greenland and Antarctica, global average specific balance for 1961–1990 was −219 ± 112 kg m−2 a−1, representing 0.33 ± 0.17 mm SLE (sea-level equivalent) a−1. For 2001–2004, the figures are −510 ± 101 kg m−2 a−1 and 0.77±0.15 mm SLE a−1. Including the smaller Greenland and Antarctic glaciers, global total balance becomes 0.38 ± 0.19 mm SLE a−1 for 1961–1990 and 0.98 ± 0.19 mm SLE a−1 for 2001–2004. For 1991–2004 the glacier contribution, 0.77 ± 0.26 mm SLE a−1, is 20–30% of a recent estimate of 3.2 ± 0.4 mm a−1 of total sea-level rise for 1993–2005.” [Link to PDF]

Changes in mountain glaciers and ice caps during the 20th century – Ohmura (2006) “The global mass balance of the glaciers outside Greenland and Antarctica is evaluated based on long-term mass-balance observations on 75 glaciers. The cause of the mass-balance change is investigated by examining winter and summer balances from 34 glaciers. The main finding is a common development in mass-balance changes shared by a number of glaciers separated by large distances and climatic conditions. The average mass balance for the second half of the 20th century was negative at −270 to −280 mm a⁻¹. The negative mass balance was found to be intensified at −10 mm a⁻².” [Link to PDF]

Extracting a Climate Signal from 169 Glacier Records – Oerlemans et al. (2005) “I constructed a temperature history for different parts of the world from 169 glacier length records. Using a first-order theory of glacier dynamics, I related changes in glacier length to changes in temperature. … Moderate global warming started in the middle of the 19th century. The reconstructed warming in the first half of the 20th century is 0.5 kelvin.” [Link to PDF]

Secular glacier mass balances derived from cumulative glacier length changes – Hoelzle et al. (2003) “The mean specific mass balance determined from glacier length change data since 1900 shows considerable regional variability but centers around a mean value of about −0.25 m year⁻¹ water equivalent.” [Link to PDF]

Glacier mass balance: the first 50 years of international monitoring – Braithwaite (2002) “The paper reviews measurements of glacier mass balance in the period 1946-95. There are data for 246 glaciers but most records are quite short. The available mass-balance data are biased to Western Europe, North America and the former USSR with too few measurements from other parts of the world. … There is no sign of any recent global trend towards increased glacier melting, and the data mainly reflect variations within and between regions.”

Glacier Mass Balance and Regime: Data of Measurements and Analysis – Duyrgerov et al. (2002) “This is the most complete data set of parameters of glacier regime have ever been compiled and published before. Data presented in appendixes include annual mass balances and related variables of mountain and subpolar glaciers outside the two major ice sheets. … The rate of annual melt-water production (ablation) by glaciers has been increasing, and comprised of about 1.7 m/yr in water equivalent for the period. … The equilibrium-line altitude has risen by 200 m…” [Link to PDF]

On Rates and Acceleration Trends of Global Glacier Mass Changes – Haeberli et al. (1999) “During the coming decades, excess radiation income and sensible heat (a few watts per square metre) as calculated with numerical climate models are both estimated to increase by a factor of about two to four as compared to the mean of the 20th century. The rate of average annual mass loss (a few decimetres per year) measured today on mountain glaciers in various parts of the world now appears to accelerate accordingly, even though detailed interpretation of the complex processes involved remains difficult. Within the framework of secular glacier retreat and Holocene glacier fluctuations, similar rates of change and acceleration must have taken place before, i.e. during times of weak anthropogenic forcing. However, the anthropogenic influences on the atmosphere could now and for the first time represent a major contributing factor to the observed glacier shrinkage at a global scale. Problems with such assessments mainly concern aspects of statistical averaging, regional climate variability, strong differences in glacier sensitivity and relations between mass balance and cumulative glacier length change over decadal to secular time scales. Considerable progress has recently been achieved in these fields of research.”

Mass balance of glaciers other than the ice sheets – Cogley & Adams (1998) “Small glaciers appear to have been at equilibrium or shrinking very slightly during 1961-90, according to analysis of an essentially complete set of published measurements. Simple calculations give an average annual mass balance of 195±59 mm a^-1 (water equivalent but this is too low because of systematic errors. … Among the 231 measured glaciers, many are small and belong to a restricted size range in which balance is negative, but much of the small-glacier extent is accounted for by larger glaciers in a size range where balance is indistinguishable from zero. Correcting for this size bias increases the average balance to 35 ±89 mm a^-1. Inspection of time series for 1940-95 (251 glaciers shows that mass balance was least negative during the 1960s, and has varied in broad agreement with Northern Hemisphere temperature anomalies;”

Year-to-Year Fluctuations of Global Mass Balance of Small Glaciers and Their Contribution to Sea-Level Changes – Dyurgerov & Meier (1997) “We estimate the means and the interannual variability during the last 30 yr of the mass balances of the small glaciers of the world (all glaciers except for the two large ice sheets), as well as the influence of these mass balance changes on fluctuations of sea level and their relation to climate. … [Area weighted mean] produces a new global mass balance value, averaging -130 +/- 33 mm yr^-1, totaling -3.9 m in water equivalent for 1961-1990 period…”

Mass Balance of Mountain and Subpolar Glaciers: A New Global Assessment for 1961-1990 – Dyurgerov & Meier (1997) “The goals of this article are (1) to combine published and unpublished mass balance measured data on more than 200 glaciers, check the quality of the data, digitize, and compile these for the period from the end of World War II (1945) to 1993 (with emphasis on the 1961-1990 period), and (2) to perform a review and analysis of this compilation. A simple global average mass balance for this period is -164 mm yr^-1 (totaling -4.9 m) in water equivalent, not including iceberg calving.” [Link to PDF]

Quantifying Global Warming from the Retreat of Glaciers – Oerlemans et al. (1994) “Records of glacier fluctuations compiled by the World Glacier Monitoring Service can be used to derive an independent estimate of global warming during the last 100 years. … The retreat of glaciers during the last 100 years appears to be coherent over the globe. On the basis of modeling of the climate sensitivity of glaciers, the observed glacier retreat can be explained by a linear warming trend of 0.66 kelvin per century.” [Link to PDF]

Contribution of Small Glaciers to Global Sea Level – Meier (1984) “The average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance. These data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975. Although the error band is large, these glaciers appear to account for a third to half of observed rise in sea level, approximately that fraction not explained by thermal expansion of the ocean.”

Closely related

Basics of glacier mass balance are given in this article by Mauri Pelto (and more here).

World Glacier Monitoring Service and their Mass Balance Bulletin (Some of the MBB PDF’s are very large, over 10MB or even over 20MB).

Papers on climate sensitivity estimates

This is a list of papers on climate sensitivity estimates. The list is based on the “Estimates of Climate Sensitivity” by Barton Paul Levenson (2006), with some additions from John Cook’s article on climate sensitivity and from my own searches. 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 (November 7, 2009): Kirk-Davidoff (2009), an additional note to Schwartz (2007), and Covey et al. (1996) added, thanks to PeterPan for suggesting these.
UPDATE (November 6, 2009): I forgot to include Schwartz (2007), I added it now. I also added Schwartz’s response to critics, thanks to Paul Middents for pointing it out, see the discussion section below.

Newer papers and other papers not in Levenson’s list:

On the diagnosis of climate sensitivity using observations of fluctuations – Kirk-Davidoff (2009) “It has been shown that lag-covariance based statistical measures, suggested by the Fluctuation Dissipation Theorem (FDT), may allow estimation of climate sensitivity in a climate model. Recently Schwartz (2007) has used measures of the decay of autocorrelation in a global surface temperature time series to estimate the real world climate sensitivity. Here we use a simple climate model, and analysis of archived coupled climate model output from the IPCC AR4 runs, for which the climate sensitivity is known, to test the utility of this approach. Our analysis of these archived model output data show that estimates of climate sensitivity derived from century-long time scales typically grossly underestimate the models’ true climate sensitivity.” [Link to PDF]

Complementary observational constraints on climate sensitivity – Urban & Keller (2009) “Here we show that reducing the uncertainty about (i) oceanic heat uptake and (ii) aerosol climate forcing can—in principle—cut off this heavy upper tail of climate sensitivity estimates. Observations of oceanic heat uptake result in a negatively correlated joint likelihood function of climate sensitivity and ocean vertical diffusivity. This correlation is opposite to the positive correlation resulting from observations of surface air temperatures. As a result, the two observational constraints can rule out complementary regions in the climate sensitivity-vertical diffusivity space, and cut off the heavy upper tail of the marginal climate sensitivity estimate.” [Link to PDF]

Insufficient forcing uncertainty underestimates the risk of high climate sensitivity – Tanaka et al. (2009) An example that shows how uncertainty in climate sensitivity estimates doesn’t necessarily mean that climate sensitivity is low. “In spite of various efforts to estimate its value, climate sensitivity is still not well constrained. Here we show that the probability of high climate sensitivity is higher than previously thought because uncertainty in historical radiative forcing has not been sufficiently considered. The greater the uncertainty that is considered for radiative forcing, the more difficult it is to rule out high climate sensitivity, although low climate sensitivity (<2°C) remains unlikely." [Link to PDF]

Target atmospheric CO₂: Where should humanity aim? – Hansen et al. (2008) “Paleoclimate data show that climate sensitivity is ~3°C for doubled CO₂, including only fast feedback processes. Equilibrium sensitivity, including slower surface albedo feedbacks, is ~6°C for doubled CO₂ for the range of climate states between glacial conditions and ice-free Antarctica.” [Link to PDF]

The equilibrium sensitivity of the Earth’s temperature to radiation changes – Knutti et al. (2008) A review article. “The quest to determine climate sensitivity has now been going on for decades, with disturbingly little progress in narrowing the large uncertainty range. However, in the process, fascinating new insights into the climate system and into policy aspects regarding mitigation have been gained. The well-constrained lower limit of climate sensitivity and the transient rate of warming already provide useful information for policy makers. But the upper limit of climate sensitivity will be more difficult to quantify.” [Link to PDF]

Aerosol radiative forcing and climate sensitivity deduced from the Last Glacial Maximum to Holocene transition – Chylek & Lohmann (2008) “We use the temperature, carbon dioxide, methane, and dust concentration record from the Vostok ice core to deduce the aerosol radiative forcing during the Last Glacial Maximum (LGM) to Holocene transition and the climate sensitivity. … This suggests a 95% likelihood of warming between 1.3 and 2.3 K due to doubling of atmospheric concentration of CO₂.”

Climate sensitivity constrained by CO₂ concentrations over the past 420 million years – Royer et al. (2007) “Here we estimate long-term equilibrium climate sensitivity by modelling carbon dioxide concentrations over the past 420 million years and comparing our calculations with a proxy record. Our estimates are broadly consistent with estimates based on short-term climate records, and indicate that a weak radiative forcing by carbon dioxide is highly unlikely on multi-million-year timescales. We conclude that a climate sensitivity greater than 1.5 °C has probably been a robust feature of the Earth’s climate system over the past 420 million years, regardless of temporal scaling.” [Link to PDF]

Heat capacity, time constant, and sensitivity of Earth’s climate system – Schwartz (2007) See John Cook’s article for some comments on this paper. Note that in the response to critics Schwartz revises the estimated sensitivity from 1.1 K to 1.9 K. “The equilibrium sensitivity of Earth’s climate is determined as the quotient of the relaxation time constant of the system and the pertinent global heat capacity. … The resultant equilibrium climate sensitivity, 0.30 ± 0.14 K/(W m−2), corresponds to an equilibrium temperature increase for doubled CO₂ of 1.1 ± 0.5 K.” [Link to PDF] [Link to Schwartz's response to critics]

Solar-Cycle Warming at the Earth’s Surface and an Observational Determination of Climate Sensitivity – Tung & Camp (2007) “From solar min to solar max, the TSI reaching the earth’s surface increases at a rate comparable to the radiative heating due to a 1% per year increase in greenhouse gases, and will probably add, during the next five to six years in the advancing phase of Solar Cycle 24, almost 0.2 °K to the globally-averaged temperature, thus doubling the amount of transient global warming expected from greenhouse warming alone. Deducing the resulting pattern of warming at the earth’s surface promises insights into how our climate reacts to known radiative forcing, and yields an independent measure of climate sensitivity based on instrumental records. This model-independent, observationally-obtained climate sensitivity is equivalent to a global double-CO₂ warming of 2.3 -4.1 °K at equilibrium, at 95% confidence level.” [Link to PDF]

Using multiple observationally-based constraints to estimate climate sensitivity – Annan & Hargreaves (2006) “Climate sensitivity has been subjectively estimated to be likely to lie in the range of 1.5–4.5°C, and this uncertainty contributes a substantial part of the total uncertainty in climate change projections over the coming century. Objective observationally-based estimates have so far failed to improve on this upper bound, with many estimates even suggesting a significant probability of climate sensitivity exceeding 6°C. In this paper, we show how it is possible to greatly reduce this uncertainty by using Bayes’ Theorem to combine several independent lines of evidence. Based on some conservative assumptions regarding the value of independent estimates, we conclude that climate sensitivity is very unlikely (<5% probability) to exceed 4.5°C. We cannot assign a significant probability to climate sensitivity exceeding 6°C without making what appear to be wholly unrealistic exaggerations about the uncertainties involved. This represents a significant lowering of the previously-estimated bound." [Link to PDF]

Constraining Climate Sensitivity from the Seasonal Cycle in Surface Temperature – Knutti et al. (2006) “A probability density function for climate sensitivity is then calculated from the present-day seasonal cycle in reanalysis and instrumental datasets. Subject to a number of assumptions on the models and datasets used, it is found that climate sensitivity is very unlikely (5% probability) to be either below 1.5–2 K or above about 5–6.5 K, with the best agreement found for sensitivities between 3 and 3.5 K.”

An Observationally Based Estimate of the Climate Sensitivity – Gregory et al. (2002) “A probability distribution for values of the effective climate sensitivity, with a lower bound of 1.6 K (5th percentile), is obtained on the basis of the increase in ocean heat content in recent decades from analyses of observed interior-ocean temperature changes, surface temperature changes measured since 1860, and estimates of anthropogenic and natural radiative forcing of the climate system.” [Link to PDF]

Quantifying Uncertainties in Climate System Properties with the Use of Recent Climate Observations – Forest et al. (2002) “We derive joint probability density distributions for three key uncertain properties of the climate system, using an optimal fingerprinting approach to compare simulations of an intermediate complexity climate model with three distinct diagnostics of recent climate observations. On the basis of the marginal probability distributions, the 5 to 95% confidence intervals are 1.4 to 7.7 kelvin for climate sensitivity and -0.30 to -0.95 watt per square meter for the net aerosol forcing.” [Link to PDF]

Paleoclimate data constraints on climate sensitivity: The paleocalibration method – Covey et al. (1996) “We use a new technique called paleocalibration to calculate the ratio of temperature response to forcing on a global mean scale for three key intervals of Earth history. By examining surface conditions reconstructed from geologic data for the Last Glacial Maximum, the middle Cretaceous and the early Eocene, we can estimate the equilibrium climate sensitivity to radiative forcing changes for different extreme climates. We find that the ratios for these three periods, within error bounds, all lie in the range obtained from general circulation models: 2–5 K global warming for doubled atmospheric carbon dioxide. Paleocalibration thus provides a data-based confirmation of theoretically calculated climate sensitivity.” [Link to PDF]

How Sensitive Is the World’s Climate? – Hansen et al. (1993) “But climate models are mainly a tool that helps extract information from real-world climate changes. The principal climate characteristic to be evaluated is the global climate sensitivity to a perturbing forcing, such as a change of atmospheric composition. Our most precise knowledge of climate sensitivity comes from data on ancient and recent climate changes.” [Link to PDF]

The ice-core record: climate sensitivity and future greenhouse warming – Lorius et al. (1990) “The prediction of future greenhouse-gas-induced warming depends critically on the sensitivity of Earth’s climate to increasing atmospheric concentrations of these gases. Data from cores drilled in polar ice sheets show a remarkable correlation between past glacial–interglacial temperature changes and the inferred atmospheric concentration of gases such as carbon dioxide and methane. These and other palaeoclimate data are used to assess the role of greenhouse gases in explaining past global climate change, and the validity of models predicting the effect of increasing concentrations of such gases in the atmosphere.” [Link to PDF]

Papers in Levenson’s list:

The origin of the European “Medieval Warm Period” – Goosse et al. (2006) “ECBILT-CLIO-VECODE has a relatively weak climate sensitivity, with a 1.8°C increase in global mean temperature in response to a doubling of atmospheric CO₂ concentration.” [Link to PDF]

Climate sensitivity constrained by temperature reconstructions over the past seven centuries – Hegerl et al. (2006) “A number of observational studies, however, find a substantial probability of significantly higher sensitivities, yielding upper limits on climate sensitivity of 7.7 K to above 9 K (refs 3–8). Here we demonstrate that such observational estimates of climate sensitivity can be tightened if reconstructions of Northern Hemisphere temperature over the past several centuries are considered. … After accounting for the uncertainty in reconstructions and estimates of past external forcing, we find an independent estimate of climate sensitivity that is very similar to those from instrumental data. If the latter are combined with the result from all proxy reconstructions, then the 5–95 per cent range shrinks to 1.5–6.2 K, thus substantially reducing the probability of very high climate sensitivity.” [Link to PDF]

An atmosphere–ocean time series model of global climate change – Stern (2005) “A time series model of the atmosphere–ocean climate system is developed, in which surface temperature (atmospheric temperature over land and sea surface temperature) moves towards a long-run equilibrium with both radiative forcing and ocean heat content, while ocean heat content accumulates the deviations from atmospheric equilibrium. … The resulting parameter estimates are closer to theoretically expected values than those of previous time series models and the estimated climate sensitivity to a doubling of carbon dioxide is 4.4 K.” [Link to PDF]

Global Warming Simulation due to the High Resolution Climate Model by Using the Earth Simulator – Sumi (2005) “Various simulations are conducted following IPCC guidance and these results are submitted to IPCC Data Center. Warming of the global averaged surface temperature is consistent to the previous estimate.” [Link to PDF]

Dynamical aspects of climate sensitivity – Boer & Yu (2003) “Dynamical aspects of climate feedback/sensitivity are investigated in climate change simulations with a common atmospheric general circulation model coupled to a full ocean model, which responds both dynamically and thermo-dynamically, and to a mixed-layer ocean component which responds only thermodynamically.” [Link to PDF]

Celestial driver of Phanerozoic climate? – Shaviv & Veizer (2003) “We find that at least 66% of the variance in the paleotemperature trend could be attributed to CRF variations likely due to solar system passages through the spiral arms of the galaxy. Assuming that the entire residual variance in temperature is due solely to the CO₂ greenhouse effect, we propose a tentative upper limit to the long-term “equilibrium” warming effect of CO₂, one which is potentially lower than that based on general circulation models.” [Link to PDF]

Climates of the Twentieth and Twenty-First Centuries Simulated by the NCAR Climate System Model – Dai et al. (2001) “The Climate System Model, a coupled global climate model without “flux adjustments” recently developed at the National Center for Atmospheric Research, was used to simulate the twentieth-century climate using historical greenhouse gas and sulfate aerosol forcing. … The projected global surface warming from the 1990s to the 2090s is 1.9°C under the BAU scenario and 1.5°C under the STA550 scenario. In both cases, the midstratosphere cools due to the increase in CO2, whereas the lower stratosphere warms in response to recovery of the ozone layer.”

Committed warming and its implications for climate change – Wetherald et al. (2001) “Time lags between changes in radiative forcing and the resulting simulated climate responses are investigated in a set of transient climate change experiments. … Results suggest that if the radiative forcing is held fixed at today’s levels, the global mean SAT will rise an additional 1.0K before equilibrating. This unrealized warming commitment is larger than the 0.6K warming observed since 1900.” [Link to PDF]

A transient climate change simulation with greenhouse gas and aerosol forcing: experimental design and comparison with the instrumental record for the twentieth century – Boer et al. (2000) “The Canadian Centre for Climate Modelling and Analysis (CCCma) global coupled model is used to investigate the potential climate effects of increasing greenhouse gas (GHG) concentrations and changes in sulfate aerosol loadings. … Simulations of the evolution of temperature and precipitation from 1900 to the present are compared with available observations. … IPCC 1990 estimates that the climate sensitivity falls in the range 1.5 to 4.5 °C so that the CCCma model sensitivity at 3.5 °C is in the upper half of this range.” [Link to PDF]

Parallel climate model (PCM) control and transient simulations – Washington et al. (2000) “Results from a 300 year present-day coupled climate control simulation are presented, as well as for a transient 1% per year compound CO₂ increase experiment which shows a global warming of 1.27 °C for a 10 year average at the doubling point of CO₂ and 2.89 °C at the quadrupling point. … A 0.5% per year CO₂ increase experiment also was performed showing a global warming of 1.5 °C around the time of CO₂ doubling and a similar warming pattern to the 1% CO₂ per year increase experiment.” [Link to PDF]

Coupled climate modelling at GFDL: Recent accomplishment and future plans – Delworth et al. (1999) (CLIVAR Exchanges 4(4), 15-20)

Transient Climate Change Simulations with a Coupled Atmosphere–Ocean GCM Including the Tropospheric Sulfur Cycle – Roeckner et al. (1999) “The time-dependent climate response to changing concentrations of greenhouse gases and sulfate aerosols is studied using a coupled general circulation model of the atmosphere and the ocean (ECHAM4/OPYC3). … As in previous experiments, the climate response is similar, but weaker, if aerosol effects are included in addition to greenhouse gases.”

Effective thermal conduction model for estimating global warming – Wolbarst (1999) “This paper presents a simple way to approximate the dependence of the global mean air temperature at Earth’s surface on the atmospheric concentration of carbon dioxide. It treats the atmosphere as a blanket, the effective thermal conductivity of which is a decreasing function of the amount of CO₂ present, and does not involve the details of energy transport.”

Climate simulation at the secular time scale – Bertrand (1998) (Thèse de doctorat, Université catholique de Louvain, 208 pp.)

Transient Climate Change in the CSIRO Coupled Model with Dynamic Sea Ice – Gordon & O’Farrell (1997) “The CSIRO coupled model has been used in a “transient” greenhouse experiment. … The transient experiment (1% increase in CO₂ compounding per annum) gave a 2°C warming at time of CO₂ doubling. The model displayed a “cold start” effect with a (maximum) value estimated at 0.3°C.”

Multi-fingerprint detection and attribution analysis of greenhouse gas, greenhouse gas-plus-aerosol and solar forced climate change – Hegerl et al. (1997) “A multi-fingerprint analysis is applied to the detection and attribution of anthropogenic climate change.” [Link to PDF]

An Estimation of the Climatic Effects of Stratospheric Ozone Losses during the 1980s – MacKay et al. (1997) “Ozone perturbations at high latitudes result in a cooling of the surface–troposphere system that is greater (by a factor of 2.8) than that estimated from the change in radiative forcing resulting from ozone depletion and the model’s 2 × CO₂ climate sensitivity.”

Geographical scenarios of greenhouse-gas and anthropogenic-sulfate-aerosol induced climate changes – Schlesinger et al. (1997) (Climate Research Group Report, Department of Atmospheric Sciences, University of illinois at Urbana Champaign, Urbana, IL, USA)

Sensitivity of Simulated Global Climate to Perturbations in Low-Cloud Microphysical Properties. Part I: Globally Uniform Perturbations – Chen & Ramaswamy (1996) “The sensitivity of the global climate to perturbations in the microphysical properties of low clouds is investigated using a general circulation model coupled to a static mixed layer ocean with fixed cloud distributions and incorporating a new broadband parameterization for cloud radiative properties. … The model’s climate sensitivity (ratio of global-mean surface temperature response to the global-mean radiative forcing) is virtually independent (to 10%) of the sign, magnitude, and the spatial pattern of the forcings considered, thus revealing a linear and invariant nature of the model’s global-mean response.” [Link to PDF]

The Effect of Enhanced Greenhouse Warming on Winter Cyclone Frequencies and Strengths – Lambert (1995) “The extratropical winter cyclone climatologies for the Northern and Southern Hemispheres are presented for a control, or 1 × CO₂ simulation, and an enhanced greenhouse warming, or 2 × CO₂ simulation, using the second generation Canadian Climate Centre general circulation model.”

A Global Climate Model (GENESIS) with a Land-Surface Transfer Scheme (LSX). Part II: CO₂ Sensitivity – Thompson & Pollard (1995) “The sensitivity of the equilibrium climate to doubled atmospheric CO₂ is investigated using the GENESIS global climate model version 1.02. … The global annual surface-air warming in the model is 2.1°C, with global precipitation increasing by 3.3%.”

Response of the Météo-France climate model to changes in CO₂ and sea surface temperature – Mahfouf et al. (1993) “The climate response to an increase in carbon dioxide and sea surface temperatures is examined using the Météo-France climate model. … A 5-year simulation is performed with a doubled CO₂ concentration using, as lower boundary conditions, mean surface temperatures anomalies and sea ice limits predicted for the years 56–65 of a 100-year transient simulation performed at Hamburg with a global coupled atmosphere-ocean model. The perturbed simulation produces a global mean surface air warming of 1.4 K and an increase in global mean precipitation rate of 4%.”

Century-scale effects of increased atmospheric CO₂ on the ocean-atmosphere system – Manabe & Stouffer (1993) “A coupled ocean-atmosphere climate model is presently used to project the evolution of the world’s climate over the course of several centuries characterized by (1) a doubling and (2) a quadrupling of atmospheric CO₂. Global mean surface air temperature increases of 3.5 and 7 percent, respectively, are seen over a period of 500 years; these projections are respectively associated with sea level rises of 1 and 2 m apart from ice-sheet melting, which would make the figures much larger.”

Greenhouse Gas–induced Climate Change Simulated with the CCC Second-Generation General Circulation Model – Boer et al. (1992) “The Canadian Climate Centre second-generation atmospheric general circulation model coupled to a mixed-layer ocean incorporating thermodynamic sea ice is used to simulate the equilibrium climate response to a doubling of C0₂. … The results of the simulation indicate a global annual warming of 3.5°C with enhanced warming found over land and at higher latitudes.”

Deriving global climate sensitivity from palaeoclimate reconstructions – Hoffert & Covey (1992) “Here we retrieve the sensitivity of two palaeoclimates, one colder and one warmer than present, by independently reconstructing both the equilibrium surface tem-perature change and the radiative forcing. Our results yield ΔT_2x = 2.3 ±0.9 °C. This range is comparable with estimates from GCMs and inferences from recent temperature observations and ocean models.”

The Response of the BMRC AGCM to a Doubling of CO₂ – McAvaney et al. (1991) (BMRC Technical Memorandum No. 3)

Sensitivity of the equilibrium surface temperature of a GCM to systematic changes in atmospheric carbon dioxide – Oglesby & Saltzman (1990) “The equilibrium response of surface temperature to atmospheric CO₂ concentration, for six values between 100 and 1000 ppm, is calculated from a series of general circulation model experiments. This response is nonlinear, showing greater sensitivity for lower values of CO₂ than for the higher values. It is suggested that changes in CO₂ concentration of a given magnitude (e.g., 100 ppm) play a larger role in the Pleistocene ice age type temperature variations, than in causing global temperature changes due to anthropogenic increases.”

C0₂ and climate: a missing feedback? – Mitchell & Ingram (1989) “Here we report results of simulations that indicate that the changes of state of cloud water may provide a substantial negative feedback on climate. The feedback is concen-trated in mid-latitudes and affects both the magnitude and distribu-tion of the climate change expected from increases in ‘greenhouse’ gases. Improved measurements and parameterizations of cloud processes are needed to quantify this process.”

The effect of doubling the CO 2 concentration on convective and non-convective rainfall in a general circulation model coupled with a simple mixed layer ocean – Noda & Tokioka (1989) (Journal of the Meteorological Society of Japan, 67, 95-110)

Design and Critical Appraisal of an Accelerated Integration Procedure for Atmospheric GCM/Mixed-Layer Ocean Models – Schlesinger et al. (1989) “The AIP was used for 1 × CO₂ and 2 × CO₂ simulations with the OSU AGCM/mixed-layer Oman model.”

Climate sensitivity due to increased CO₂: experiments with a coupled atmosphere and ocean general circulation model – Washington & Meehl (1989) “Three simulations are run: one with an instantaneous doubling of atmospheric CO₂ (from 330 to 660 ppm), another with the CO₂ concentration starting at 330 ppm and increasing linearly at a rate of 1% per year, and a third with CO₂ held constant at 330 pm. Results at the end of 30 years of simulation indicate a globally averaged surface air temperature increase of 1.6° C for the instantaneous doubling case…”

Cloud Feedback Processes in a General Circulation Model – Wetherald & Manabe (1988) “The influence of the cloud feedback process upon the sensitivity of climate is investigated by comparing the behavior of two versions of a climate model with predicted and prescribed cloud cover. … At most latitudes the effect of reduced cloud amount in the upper troposphere overshadows that of increased cloudiness around the tropopause, thereby lowering the global mean planetary albedo and enhancing the CO₂ induced warming. On the other hand, the increase of low cloudiness in high latitudes raises the planetary albedo and thus decreases the CO₂ induced warming of climate. However, the contribution of this negative feedback process is much smaller than the effect of the positive feedback process involving the change of high cloud.” [Link to PDF]

Simulated climate and CO₂—Induced climate change over Western Europe – Wilson & Mitchell (1987) “When atmospheric CO₂ concentrations are quadrupled, and sea surface temperatures and sea ice extents changed appropriately, the number of cold episodes is reduced and precipitation is less frequent in summer and autumn over much of Europe, and throughout the year in the south.”

An investigation of cloud cover change in response to thermal forcing – Wetherald & Manabe (1986) “This article reviews the distributions of cloud cover change from several climate sensitivity experiments conducted at the Geophysical Fluid Dynamics Laboratory of NOAA (GFDL) and other institutions. … It was found that in all five cases, clouds were decreased in the moist, convectively active regions such as the tropical and middle latitude rainbelts, whereas they increased in the stable region near the model surface from middle to higher latitudes. In addition, cloud also increased in the lower model stratosphere and generally decreased in the middle and upper troposphere for practically all latitudes.”

Volcanic, CO₂ and solar forcing of Northern and Southern Hemisphere surface air temperatures – Gilliland & Schneider (1984) “The model used here allows a direct comparison of observed and simulated temperatures from the same physical domains—over land and sea separately in each hemisphere. … The empirically derived CO₂ equilibrium doubling response for air surface temperature is 1.6 +/- 0.3°C, although the statistical significance of this result is uncertain.”

Climate sensitivity: Analysis of feedback mechanisms – Hansen et al. (1984) “We study climate sensitivity and feedback processes in three independent ways: (1) by using a three dimensional (3-D) global climate model for experiments in which solar irradiance S_o is increased 2 percent or CO₂ is doubled, (2) by using the CLIMAP climate boundary conditions to analyze the contributions of different physical processes to the cooling of the last ice age (18K years ago), and (3) by using estimated changes in global temperature and the abundance of atmospheric greenhouse gases to deduce an empirical climate sensitivity for the period 1850-1980. … Our 3-D global climate model yields a warming of ~4°C for either a 2 percent increase of S_o or doubled CO₂. … The temperature increase believed to have occurred in the past 130 years (approximately 0.5°C) is also found to imply a climate sensitivity of 2.5-5°C for doubled Cog…” [Link to PDF]

Seasonal Cycle Experiment on the Climate Sensitivity Due to a Doubling of CO₂ With an Atmospheric General Circulation Model Coupled to a Simple Mixed-Layer Ocean Model – Washington & Meehl (1984) “A simple slab ocean of 50 m depth, which allows for seasonal ocean heat storage but no ocean heat transport, is coupled to a global spectral general circulation model with global domain, realistic geography, and computed clouds. Globally averaged, the annual mean surface air temperature increase computed over the last 3 years of an integration with a full annual cycle for 2 × CO₂ compared to the control for 1 × CO₂ is 3.5°C.”

Climate Studies with a Multi-Layer Energy Balance Model. Part II: The Role of Feedback Mechanisms in the CO₂ Problem – Chou et al. (1982) “The sensitivity of climate to a doubling of the atmospheric CO₂, content has been studied using the GLAS multi-layer energy balance model. In response to a doubled CO₂ content, tropospheric temperature lapse rate decreases at low latitudes but increases at high latitudes. Averaged over the Northern Hemisphere, the change is +2.3°C in the surface temperature and +0.47°C in the earth’s brightness temperature. … It is found that the sensitivity of surface temperature is approximately doubled at all latitudes due to the change in water vapor content.”

Sensitivity Analysis of a Radiative-Convective Model by the Adjoint Method – Hall et al. (1982) “The adjoint method of sensitivity analysis is demonstrated on a radiative-convective climate model. … The sensitivities accurately predict the effect on surface air temperature of small variations in the model parameters. Relative sensitivities are used to rank the importance of all the parameters. Several of the sensitivities to parameters customarily considered in previous works (e.g., solar constant, surface albedo, relative humidity, CO₂ concentration) are reproduced, but the largest sensitivities are to constants used to compute the saturation vapor pressure of water.”

Impact of coupled perturbations of atmospheric trace gases on Earth’s climate and ozone – Nicoli & Visconti (1982) “The doubling of carbon dioxide concentration has the effect of warming the troposphere and cooling the stratosphere. As a result of this cooling, the change of ozone columnar density produced by 10 ppb of chlorine amount to 9.3% as compared to –10.9% obtained without temperature feedback. Perturbation in nitrous oxide correspond to an increase in NO x of the stratosphere with consequent ozone reduction while doubling the methane concentration correspond to a slight increase in columnar density. The effect of the increased methane concentration in the stratosphere contributes to reduce the effect of CFC due to the enhanced formation of HCl. The perturbation of these two minor constituents appreciably increase the greenhouse effect to 2.30 from 1.67°, obtained when carbon dioxide alone is considered.”

The Role of Ocean-Atmosphere Interactions in the CO₂ Climate Problem – Ramanathan (1981) “The climate sensitivity question is examined from the viewpoint of surface energy balance considerations. This approach clarifies the role of ocean-atmosphere interactions in determining the surface warming to an increase in CO₂. The study uses a one-dimensional, 17-layer, coupled ocean-atmosphere model. The primary contribution to the surface warming is from the enhanced tropospheric IR emission, which is an order of magnitude greater than the direct CO₂ radiative heating at the surface. The source for this enhancement is the increased H₂O evaporation from the warmer oceans in the CO₂ rich atmosphere and, hence, ocean-atmosphere interactions play a crucial role in determining the magnitude of the surface warming as well as its transient response.”

On the Distribution of Climate Change Resulting from an Increase in CO₂ Content of the Atmosphere – Manabe & Wetherald (1980) “A study of the climatic effect of doubling or quadrupling of CO₂ in the atmosphere has been continued by the use of a simple general circulation model with a limited computational domain, highly idealized geography, no seasonal variation of insolation, and a simplified interaction between cloud and radiative transfer. The results from the numerical experiments reveal that the response of the model climate to an increase of CO₂ content in air is far from uniform geographically.” [Link to PDF]

The Climatological Significance of a Doubling of Earth’s Atmospheric Carbon Dioxide Concentration – Idso (1980) “The mean global increase in thermal radiation received at the surface of the earth as a consequence of a doubling of the atmospheric carbon dioxide content is calculated to be 2.28 watts per square meter. Multiplying this forcing function by the atmosphere’s surface air temperature response function, which has recently been determined by three independent experimental analyses to have a mean global value of 0.113 K per watt per square meter, yields a value of <= 0.26 K for the resultant change in the mean global surface air temperature. This result is about one order of magnitude less than those obtained from most theoretical numerical models, but it is virtually identical to the result of a fourth experimental approach to the problem described by Newell and Dopplick."

A CO₂-climate sensitivity study with a mathematical model of the global climate – Manabe & Stouffer (1979) “An increase in the CO₂-content of the atmosphere resulting from man’s activity could have a significant effect on the climate in the near future. We describe here some new results from a study of the response of a mathematical model of the climate to an increase in the CO₂ content of the air.”

Some Experiments with a Zonally Averaged Climate Model – Ohring & Adler (1978) “When the atmospheric carbon dioxide content is doubled, the hemispheric mean surface temperature increases by 0.5°C in the absence of ice feedback, the largest increases taking place at high latitudes. Ice albedo feedback amplifies the hemispheric average temperature change by about 50%; amplifications as large as several hundred percent are obtained in polar regions. A change in mean surface temperature of ±1°C for a ±1% change in solar constant is obtained in the absence of ice feedback, but this is amplified to −1.5°C (decreased solar constant) and 1.4°C (increased solar constant) when ice feedback is included. As In the 2×CO₂ case, polar amplification factors due to ice albedo feedback are several hundred percent.”

A Radiative-Convective Model Study of the CO₂ Climate Problem – Augustsson & Ramanathan (1977) “A radiative-convective model study of the increase in global surface temperature ΔTg due to an increase in the CO₂ concentration is presented. … The computed value of ΔTg is very sensitive to radiative-convective model assumptions regarding cloud top and relative humidity. Because of this sensitivity the estimated value of ΔTg for a doubling of the CO₂ concentration ranges from 1.98 to 3.2 K.”

An Annual Zonally Averaged Hemispherical Climatic Model with Diffuse Cloudiness Feedback – Temkin & Snell (1976) “An annual, zonally averaged, steady-state hemispherical climatic model is developed which incorporates the diffuse thin cloud tropospheric structure of Weare and Snell as a cloudiness feedback mechanism. … The response of the model to variations in various climatic determinants is studied, including hemispherical variations in carbon dioxide, aerosol and solar constant, and also including certain zonal variations in man-made thermal energy and aerosol. … The sensitivity of the model in terms of the hemispherical mean sea level temperature is about twice that of the globally averaged model of Weare and Snell.”

The dependence of atmospheric temperature on the concentration of carbon dioxide – Manabe (1975) A book chapter. “The effect of changes in the carbon dioxide content of the atmosphere on the average world temperature is investigated using a radiative, convective model of the atmosphere (Manabe et al., 1964, 1967). The radiative, convective equilibrium of the atmosphere obtained with the model is in good agreement with the distribution given by the U.S. standard atmosphere. Numerical computations indicate that doubling or halving the atmospheric CO₂ concentration increases or decreases the surface temperature of the atmosphere by about 2.3 deg C. Assuming a 25% increase from the 1900 concentration by the end of this century, a corresponding 0.8 deg C increase in average surface temperature is predicted.”

The Effects of Doubling the CO₂ Concentration on the climate of a General Circulation Model – Manabe & Wetherald (1975) “An attempt is made to estimate the temperature changes resulting from doubling the present CO₂ concentration by the use of a simplified three-dimensional general circulation model. … It is shown that the CO₂ increase raises the temperature of the model troposphere, whereas it lowers that of the model stratosphere.”

A study of the sensitivity of radiativeconvective models – Ramanathan (1975) (Preprints Second Conf. Atmospheric Radiation, 1975) This probably is the referred Ramanathan (1975).

A Reassessment of the Effect of CO₂ Variations on a Simple Global Climatic Model – Sellers (1974) “A simple global climatic model described earlier is modified slightly and reapplied to the CO₂ problem. … …the average global surface temperature drops 1.64C if the amount of CO₂ in the atmosphere is halved and rises 1.32C if the amount is doubled.”

A Diffuse Thin Cloud Atmospheric Structure as a Feedback Mechanism in Global Climatic Modeling – Weare & Snell (1974) “The sensitivity of the “climate” to variations in aerosol optical density, atmospheric carbon dioxide, and the solar constant is calculated and the results are comparable to those obtained by others using very different models. In general, our model exhibits slightly greater stability.”

A New Global Climatic Model – Sellers (1973) “The initial carbon dioxide content of the atmosphere (250 cm) was doubled and halved without any appreciable effect on surface temperatures. Doubling the CO₂ content increased the temperature by at most 0.6C (at high northern latitudes in winter); the average increase was only 0.1C.” [Link to PDF]

Estimates of future change of climate due to the increase of carbon dioxide concentration in the air – Manabe (1971) (Man’s Impact on the Climate, W. I-I. Matthews, W. W. Kellogg, and G. D. Robinson, Eds., Cambridge, MA: The MIT Press, 249-264)

Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate – Rasool & Schneider (1971) “Effects on the global temperature of large increases in carbon dioxide and aerosol densities in the atmosphere of Earth have been computed. It is found that, although the addition of carbon dioxide in the atmosphere does increase the surface temperature, the rate of temperature increase diminishes with increasing carbon dioxide in the atmosphere.”

Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity – Manabe & Wetherald (1967) “Radiative convective equilibrium of the atmosphere with a given distribution of relative humidity is computed as the asymptotic state of an initial value problem. … According to our estimate, a doubling of the CO₂ content in the atmosphere has the effect of raising the temperature of the atmosphere (whose relative humidity is fixed) by about 2C. Our model does not have the extreme sensitivity of atmospheric temperature to changes of CO₂ content which was adduced by Möller.” [Link to PDF]

On the Influence of Changes in the CO₂ Concentration in Air on the Radiation Balance of the Earth’s Surface and on the Climate – Möller (1963) (J. Geophysical Research 68, 3877-3886) Is missing from JGR digital library.

The carbon dioxide theory of climate change – Plass (1956) “The most recent calculations of the infra-red flux in the region of the 15 micron CO₂ band show that the average surface temperature of the earth increases 3.6° C if the CO₂ concentration in the atmosphere is doubled and decreases 3.8° C if the CO₂ amount is halved, provided that no other factors change which influence the radiation balance.” [Link to PDF]

The Artificial Production of Carbon Dioxide and Its Influence on Climate – Callendar (1938) (Quarterly J. Royal Meteorological Society 64, 223-40)

The Temperature of the Lower Atmosphere of the Earth – Hulburt (1931) “From the known amounts of the various gases of the atmosphere from sea level to about 20 km, from the observed light absorption coefficients of the gases and from the albedo of the earth’s surface the temperature of the atmosphere in radiative equilibrium is calculated on the assumption that the sunlight is the only source of energy. … Calculation shows that doubling or tripling the amount of the carbon dioxide of the atmosphere increases the average sea level temperature by about 4° and 7°K, respectively; halving or reducing to zero the carbon dioxide decreases the temperature by similar amounts. Such changes in temperature are about the same as those which occur when the earth passes from an ice age to a warm age, or vice versa. Thus the calculation indicates that the carbon dioxide theory of the ice ages, originally proposed by Tyndall, is a possible theory.”

On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground – Arrhenius (1896) “Thus if the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression.” [Link to PDF]

Wrong trend

Hey, this is wrong way around!

In this particular occasion (today’s situation just few minutes ago), there is 32 paperlist views and 9 clicks to papers. This is quite common situation. The paperlists in this blogs are just lists of links to scientific papers. I’m not even giving full abstracts in the lists, just a few selected sentences.

So click those links, dear readers.

Papers on anthropogenic carbon dioxide observations

This is a list of papers on carbon dioxide sources of atmospheric carbon dioxide concentration. Emphasis is on the papers that study the cause for the decadal increasing trend of carbon dioxide concentration in the atmosphere. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Variations of anthropogenic CO₂ in urban area deduced by radiocarbon concentration in modern tree rings – Rakowski et al. (2008) “Radiocarbon concentration in the atmosphere is significantly lower in areas where man-made emissions of carbon dioxide occur. This phenomenon is known as Suess effect, and is caused by the contamination of clean air with non-radioactive carbon from fossil fuel combustion. The effect is more strongly observed in industrial and densely populated urban areas. Measurements of carbon isotope concentrations in a study area can be compared to those from areas of clear air in order to estimate the amount of carbon dioxide emission from fossil fuel combustion by using a simple mathematical model. This can be calculated using the simple mathematical model. The result of the mathematical model followed in this study suggests that the use of annual rings of trees to obtain the secular variations of ¹⁴C concentration of atmospheric CO₂ can be useful and efficient for environmental monitoring and modeling of the carbon distribution in local scale.”

High resolution atmospheric monitoring of urban carbon dioxide sources – Pataki et al. (2006) “We used a tunable diode laser absorption spectrometer (TDL) to measure CO₂ mixing ratios and carbon isotope composition of CO₂ in order to estimate the contribution of gasoline versus natural gas combustion to atmospheric CO₂ in Salt Lake City. The results showed a pronounced diurnal pattern: the proportional contribution of natural gas combustion varied from 30–40% of total anthropogenic CO₂ during evening rush hour to 60–70% at pre-dawn. In addition, over a warming period of several days, the proportional contribution of natural gas combustion decreased with air temperature, likely related to decreased residential heating. These results show for the first time that atmospheric measurements may be used to infer patterns of energy and fuel usage on hourly to daily time scales.” [Link to PDF]

Controlling for anthropogenically induced atmospheric variation in stable carbon isotope studies – Long et al. (2005) “Recent elevation of atmospheric CO₂ concentration, related primarily to fossil fuel combustion, has reduced atmospheric CO₂ δ¹³C (¹³C/¹²C), and this change in isotopic baseline has, in turn, reduced plant and animal tissue δ¹³C of terrestrial and aquatic organisms. Such depletion in CO₂ δ¹³C and its effects on tissue δ¹³C may introduce bias into δ¹³C investigations, and if this variation is not controlled, may confound interpretation of results obtained from tissue samples collected over a temporal span. … …we estimated a correction factor that controls for atmospheric change…”

Diurnal variability of δ¹³C and δ¹⁸O of atmospheric CO₂ in the urban atmosphere of Kraków, Poland – Zimnoch et al. (2004) “This article presents the results of measurements of the isotopic composition and concentration of atmospheric carbon dioxide, performed on air samples from Kraków (Southern Poland) in different seasons of the year. … The calculations show that during the summer and early autumn the dominant contribution to local CO₂ peaks is the biosphere, making up to 20% of atmospheric CO₂ during the nocturnal temperature inversion in the lower troposphere. During early spring and winter, anthropogenic emissions are the main local source.” [Link to PDF]

Seasonal cycle of carbon dioxide and its isotopic composition in an urban atmosphere: Anthropogenic and biogenic effects – Pataki et al. (2003) “Atmospheric CO₂ mixing ratios and carbon and oxygen isotope composition were measured at 18 m above the ground in Salt Lake City, Utah, United States, for a one-year period. … The isotope-tracer technique used shows promise for quantifying the impacts of urban processes on the isotopic composition of the atmosphere and partitioning urban CO₂ sources into their component parts.” [Link to PDF]

Stable carbon isotope constraints on mixing and mass balance of CO₂ in an urban atmosphere: Dallas metropolitan area, Texas, USA – Clark-Thorne & Yapp (2003) “The concentrations and δ¹³C values of atmospheric CO₂ were measured in 150 air samples collected at 8 sites in the Dallas metropolitan area over the period August 1998 to December 1999. … …but the overall pattern suggests that, as temperature decreases, the proportion of anthropogenic CO₂ derived from combustion of natural gas increases. This increase appears to reflect increased use of natural gas for home heating, etc., in cooler weather. Therefore, seasonally changing patterns of fossil fuel use are detectable in the atmospheric CO₂ of this urban environment.”

Evidence for preindustrial variations in the marine surface water carbonate system from coralline sponges – Böhm et al. (2002) “Carbon isotope records from coralline sponges clearly reflect the industrial ¹²C increase in atmospheric CO₂ with a precision that permits quantitative interpretations. … All δ¹³C records (appendix A) show the full extent of the industrial decline (Figure 3) caused by the anthropogenic addition of ¹²C-enriched CO₂ to the atmosphere. … The industrial decline in δ¹³C started in the first half of the 19th century after a short period of stable values around 1800 A.D.” [Link to PDF]

A 1000-year high precision record of δ¹³C in atmospheric CO₂ – Francey et al. (1999) “We present measurements of the stable carbon isotope ratio in air extracted from Antarctic ice core and firn samples. … Here, we start by confirming the trend in the Cape Grim in situ δ¹³C record from 1982 to 1996, and extend it back to 1978 using the Cape Grim Air Archive. … An almost continuous atmospheric history of δ¹³C over 1000 years results, exhibiting significant decadal-to-century scale variability unlike that from earlier proxy records. The decrease in δ¹³C from 1860 to 1960 involves a series of steps confirming enhanced sensitivity of δ¹³C to decadal timescale-forcing, compared to the CO₂ record.”

The ¹³C Suess Effect in the World Surface Oceans and Its Implications for Oceanic Uptake of CO₂: Analysis of Observations at Bermuda – Bacastow et al. (1996) “Surface ocean water δ¹³C measurements near Bermuda are examined in an attempt to find the annual decrease caused by the addition of anthropogenic CO₂ to the atmosphere. … Results are, in general, consistent with the low side of the Intergovernmental Panel on Climate Control estimation of 2.0 ± 0.8 GtC yr⁻¹.” [Link to PDF]

Isotopic characterisation of anthropogenic CO₂ emissions using isotopic and radiocarbon analysis – Meijer et al. (1996) “At the station Kollumerwaard (Netherlands), for monitoring tracers in the troposphere, air is sampled in sixteen containers for off-line ¹³C, ¹⁸O and ¹⁴C isotopic analysis of CO₂. … Results during the first year of operation show that the δ¹³C values for the anthropogenic CO₂ are significantly more negative than generally assumed (values ranging from -30 to -58 ‰ VPDB), which clearly indicates the importance of natural gas consumption in the Netherlands. …As an important side result, the method produces reliable values for the regionally averaged ratio CO : fossil CO₂ (results ranging from 0.5 to 1%), a direct measure for combustion quality.”

Interannual extremes in the rate of rise of atmospheric carbon dioxide since 1980 – Keeling et al. (1995) “Observations of atmospheric CO₂ concentrations at Mauna Loa, Hawaii, and at the South Pole over the past four decades show an approximate proportionality between the rising atmospheric concentrations and industrial CO₂ emissions. This proportionality, which is most apparent during the first 20 years of the records, was disturbed in the 1980s by a disproportionately high rate of rise of atmospheric CO₂, followed after 1988 by a pronounced slowing down of the growth rate. To probe the causes of these changes, we examine here the changes expected from the variations in the rates of industrial CO₂ emissions over this time, and also from influences of climate such as El Niño events. We use the ¹³C/¹²C ratio of atmospheric CO₂ to distinguish the effects of interannual variations in biospheric and oceanic sources and sinks of carbon. We propose that the recent disproportionate rise and fall in CO¹³ growth rate were caused mainly by interannual variations in global air temperature (which altered both the terrestrial biospheric and the oceanic carbon sinks), and possibly also by precipitation. We suggest that the anomalous climate-induced rise in CO¹³ was partially masked by a slowing down in the growth rate of fossil-fuel combustion, and that the latter then exaggerated the subsequent climate-induced fall.” [Link to PDF]

Oceanic Uptake of Fossil Fuel CO₂: Carbon-13 Evidence – Quay et al. (1992) “The δ¹³C value of the dissolved inorganic carbon in the surface waters of the Pacific Ocean has decreased by about 0.4 per mil between 1970 and 1990. This decrease has resulted from the uptake of atmospheric CO₂ derived from fossil fuel combustion and deforestation. The net amounts of CO₂ taken up by the oceans and released from the biosphere between 1970 and 1990 have been determined from the changes in three measured values: the concentration of atmospheric CO₂, the δ¹³C of atmospheric CO₂ and the δ¹³C value of dissolved inorganic carbon in the ocean. The calculated average net oceanic CO₂ uptake is 2.1 gigatons of carbon per year. This amount implies that the ocean is the dominant net sink for anthropogenically produced CO₂ and that there has been no significant net CO₂ released from the biosphere during the last 20 years.” [Link to PDF]

Input of excess CO₂ to the surface ocean based on ¹³C/¹²C ratios in a banded Jamaican sclerosponge – Druffel & Benavides (1986) “Here we present surface ocean ¹³C and ¹⁸O records measured in the skeleton of a living sclerosponge (Ceratoporella nicholsoni), which accretes aragonite in isotopic equilibrium with the surrounding sea water/dissolved inorganic carbon (DIC) system. The ¹³C record reveals a decrease of 0.50 [promille] from 1820 to 1972.”

Ice core record of the ¹³C/¹²C ratio of atmospheric CO₂ in the past two centuries – Friedli et al. (1986) “The release of carbon into the atmosphere due to the activities of humans has caused an increase in concentration as well as a change in the isotopic composition of atmospheric carbon dioxide. CO₂ derived from fossil fuel combustion and from biomass destruction have δ¹³C values of ~-25 [promille] (compared to the atmospheric value of ~-7 [promille]) and are thus depleted in ¹³C. We have measured δ¹³C of CO₂ separated from air trapped in bubbles in ice samples from an ice core taken at Siple Station in Antarctica, in which it has been possible to demonstrate the atmospheric increase of CO₂ (ref. 1) and methane2 with high time resolution. The isotopic results, together with the CO₂ record from the same ice core, yield information on the sources of excess carbon dioxide and provide a data base for testing the consistency of global carbon cycle models.”

Recent trends in the ¹³C/¹²C ratio of atmospheric carbon dioxide – Keeling et al. (1979) “The ¹³C/¹²C ratio of atmospheric carbon dioxide has decreased by approximately 0.6 [promille] over 22 yr according to new direct measurements reported here.”

Papers on sea ice amount observations

This is a list of papers on the amount of sea ice globally and in Arctic and Antarctic regions. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Global sea ice papers

Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century – Rayner et al. (2003) “We present the Met Office Hadley Centre’s sea ice and sea surface temperature (SST) data set, HadISST1, and the nighttime marine air temperature (NMAT) data set, HadMAT1. HadISST1 replaces the global sea ice and sea surface temperature (GISST) data sets and is a unique combination of monthly globally complete fields of SST and sea ice concentration on a 1° latitude-longitude grid from 1871. … The sea ice fields are made more homogeneous by compensating satellite microwave-based sea ice concentrations for the impact of surface melt effects on retrievals in the Arctic and for algorithm deficiencies in the Antarctic and by making the historical in situ concentrations consistent with the satellite data.”

Analysis of merged SMMR‐SSMI time series of Arctic and Antarctic sea ice parameters 1978–1995 – Bjørgo et al. (1997) “The Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) and the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSMI) provide information on the global sea ice cover from 1978 to present. … Statistical analysis on the time series estimates the decreases in Arctic ice extent and ice area to be 4.5% and 5.7%, respectively, during the 16.8‐year observation period.” [Link to PDF]

Observed Hemispheric Asymmetry in Global Sea Ice Changes – Cavalieri et al. (1997) “From November 1978 through December 1996, the areal extent of sea ice decreased by 2.9 ± 0.4 percent per decade in the Arctic and increased by 1.3 ± 0.2 percent per decade in the Antarctic. The observed hemispheric asymmetry in these trends is consistent with a modeled response to a carbon dioxide-induced climate warming. The interannual variations, which are 2.3 percent of the annual mean in the Arctic, with a predominant period of about 5 years, and 3.4 percent of the annual mean in the Antarctic, with a predominant period of about 3 years, are uncorrelated.”

Arctic and antarctic sea ice, 1978-1987: Satellite passive-microwave observations and analysis – Gloersen et al. (1992) “This book contains a description and analysis of the spatial and temporal variations in the Arctic and Antarctic sea ice covers from October 26, 1978 througb August 20, 1987. It is based on data collected by tbe Scanning Multichannel Microwave Radiometer (SMMR) onboard the NASA Nimbus 7 satellite. … The interannual variability of the ice extent areas is much larger for the perimeter seas than for the Arctic as a whole; some regions exhibit decreasing trends, while others exhibit increasing trends. … As in the Arctic, the individual sectors have larger interannual differences than in the Antarctic as a whole, implying compensating relationships in the various regions.”

Arctic sea ice papers

Circumpolar thinning of Arctic sea ice following the 2007 record ice extent minimum – Giles et al. (2008) “Using satellite radar altimetry data, covering the Arctic Ocean up to 81.5° North, we show that the average winter sea ice thickness anomaly, after the melt season of 2007, was 0.26 m below the 2002/2003 to 2007/2008 average. More strikingly, the Western Arctic anomaly was 0.49 m below the six-year mean in the winter of 2007/2008. These results show no evidence of short-term preconditioning through ice thinning between 2002 and 2007 but show that, after the record minimum ice extent in 2007, the average ice thickness was reduced, particularly in the Western Arctic.”

Accelerated decline in the Arctic sea ice cover – Comiso et al. (2008) “Satellite data reveal unusually low Arctic sea ice coverage during the summer of 2007, caused in part by anomalously high temperatures and southerly winds. The extent and area of the ice cover reached minima on 14 September 2007 at 4.1 × 10⁶ km² and 3.6 × 10⁶ km², respectively. These are 24% and 27% lower than the previous record lows, both reached on 21 September 2005, and 37% and 38% less than the climatological averages. Acceleration in the decline is evident as the extent and area trends of the entire ice cover (seasonal and perennial ice) have shifted from about −2.2 and −3.0% per decade in 1979–1996 to about −10.1 and −10.7% per decade in the last 10 years.” [Link to PDF]

Recent trend reversals in arctic sea ice extents: possible connections to the north Atlantic oscillation – Parkinson (2008) “This paper reports the results of regression analysis performed on the yearly averaged ice extents for the two time periods 1979-1990 and 1990-1999, and reveals two important findings: (1) for the Arctic as a whole, the decade of the 1990s witnessed a deceleration of the trend toward lesser ice extents; and (2) the sign of the trend reversed from the 1979-1990 period to the 1990-1999 period in seven of the nine regions into which the Arctic ice cover is divided for analysis. The paper explores the possible connection between the spatial patterns of the sea ice trends and their reversals and the North Atlantic Oscillation (NAO), which reached a peak in its annual index in 1990.”

Arctic sea ice decline: Faster than forecast – Stroeve et al. (2007) “From 1953 to 2006, Arctic sea ice extent at the end of the melt season in September has declined sharply. All models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) show declining Arctic ice cover over this period. However, depending on the time window for analysis, none or very few individual model simulations show trends comparable to observations. If the multi-model ensemble mean time series provides a true representation of forced change by greenhouse gas (GHG) loading, 33–38% of the observed September trend from 1953–2006 is externally forced, growing to 47–57% from 1979–2006.” [Link to PDF]

Rapid reduction of Arctic perennial sea ice – Nghiem et al. (2007) “The extent of Arctic perennial sea ice, the year-round ice cover, was significantly reduced between March 2005 and March 2007 by 1.08 × 106 km², a 23% loss from 4.69 × 106 km² to 3.61 × 106 km², as observed by the QuikSCAT/SeaWinds satellite scatterometer (QSCAT). … QSCAT data also revealed mechanisms contributing to the perennial-ice extent loss: ice compression toward the western Arctic, ice loading into the Transpolar Drift (TD) together with an acceleration of the TD carrying excessive ice out of Fram Strait, and ice export to Baffin Bay.” [Link to PDF]

Thinning of the Arctic sea‐ice cover – Rothrock et al. (1999) “Comparison of sea‐ice draft data acquired on submarine cruises between 1993 and 1997 with similar data acquired between 1958 and 1976 indicates that the mean ice draft at the end of the melt season has decreased by about 1.3 m in most of the deep water portion of the Arctic Ocean, from 3.1 m in 1958–1976 to 1.8 m in the 1990s.” [Link to PDF]

Arctic sea ice extents, areas, and trends, 1978–1996 – Parkinson et al. (1999) “Satellite passive-microwave data for November 1978 through December 1996 reveal marked seasonal, regional, and interannual variabilities, with an overall decreasing trend of −34,300 ± 3700 km²/yr (−2.8%/decade) in Arctic sea ice extents over the 18.2-year period.”

Satellite Evidence for an Arctic Sea Ice Cover in Transformation – Johannessen et al. (1999) “Recent research using microwave satellite remote sensing data has established that there has been a reduction of about 3 percent per decade in the areal extent of the Arctic sea ice cover since 1978, although it is unknown whether the nature of the perennial ice pack has changed. These data were used to quantify changes in the ice cover’s composition, revealing a substantial reduction of about 14 percent in the area of multiyear ice in winter during the period from 1978 to 1998. There also appears to be a strong correlation between the area of multiyear ice and the spatially averaged thickness of the perennial ice pack, which suggests that the satellite-derived areal decreases represent substantial rather than only peripheral changes.” [Link to PDF]

Antarctic sea ice papers

Non‐annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent – Turner et al. (2009) “Based on a new analysis of passive microwave satellite data, we demonstrate that the annual mean extent of Antarctic sea ice has increased at a statistically significant rate of 0.97% dec^-1 since the late 1970s.”

Thickness distribution of Antarctic sea ice – Worby et al. (2008) “Ship-based observations are used to describe regional and seasonal changes in the thickness distribution and characteristics of sea ice and snow cover thickness around Antarctica. The data set comprises 23,373 observations collected over more than 2 decades of activity and has been compiled as part of the Scientific Committee on Antarctic Research (SCAR) Antarctic Sea Ice Processes and Climate (ASPeCt) program. The results show the seasonal progression of the ice thickness distribution for six regions around the continent together with statistics on the mean thickness, surface ridging, snow cover, and local variability for each region and season. … The long-term mean and standard deviation of total sea ice thickness (including ridges) is reported as 0.87 ± 0.91 m, which is 40% greater than the mean level ice thickness of 0.62 m.” [Link to PDF]

Antarctic sea ice variability and trends, 1979–2006 – Cavalieri & Parkinson (2008) “Analyses of 28 years (1979–2006) of Antarctic sea ice extents and areas derived from satellite passive microwave radiometers are presented and placed in the context of results obtained previously for the 20-year period 1979–1998. … The total Antarctic sea ice extent trend increased slightly, from 0.96 ± 0.61% decade^-1 to 1.0 ± 0.4% decade^-1, from the 20- to 28-year period, reflecting contrasting changes in the sector trends.”

Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions – Zhang et al. (2007) A model study, but important for the explanation of the sea ice increase in Antarctic. “Estimates of sea ice extent based on satellite observations show an increasing Antarctic sea ice cover from 1979 to 2004 even though in situ observations show a prevailing warming trend in both the atmosphere and the ocean. This riddle is explored here using a global multicategory thickness and enthalpy distribution sea ice model coupled to an ocean model. … The model shows that an increase in surface air temperature and downward longwave radiation results in an increase in the upper-ocean temperature and a decrease in sea ice growth, leading to a decrease in salt rejection from ice, in the upper-ocean salinity, and in the upper-ocean density. The reduced salt rejection and upper-ocean density and the enhanced thermohaline stratification tend to suppress convective overturning, leading to a decrease in the upward ocean heat transport and the ocean heat flux available to melt sea ice. The ice melting from ocean heat flux decreases faster than the ice growth does in the weakly stratified Southern Ocean, leading to an increase in the net ice production and hence an increase in ice mass. This mechanism is the main reason why the Antarctic sea ice has increased in spite of warming conditions both above and below during the period 1979–2004 and the extended period 1948–2004.” [Link to PDF]

Variability of Antarctic sea ice 1979–1998 – Zwally et al. (2002) “The principal characteristics of the variability of Antarctic sea ice cover as previously described from satellite passive microwave observations are also evident in a systematically calibrated and analyzed data set for 20.2 years (1979–1998). The total Antarctic sea ice extent (concentration >15%) increased by 11,180 ± 4190 km² yr^-1 (0.98 ± 0.37% (decade)^-1). The increase in the area of sea ice within the extent boundary is similar (10,860 ± 3720 km² yr^-1 and 1.26 ± 0.43% (decade)^-1).”

Papers on cloud feedback observations

This is a list of papers on cloud feedback observations. Note that most papers listed are local analyses. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Observational and Model Evidence for Positive Low-Level Cloud Feedback – Clement et al. (2009) “Feedbacks involving low-level clouds remain a primary cause of uncertainty in global climate model projections. This issue was addressed by examining changes in low-level clouds over the Northeast Pacific in observations and climate models. Decadal fluctuations were identified in multiple, independent cloud data sets, and changes in cloud cover appeared to be linked to changes in both local temperature structure and large-scale circulation. This observational analysis further indicated that clouds act as a positive feedback in this region on decadal time scales. … The only model that passed this test simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback.” [Link to PDF]

Cloud forcing and feedback during recent Arctic sea ice loss – Kay et al. (2009) “Recent impressive declines in Arctic sea ice extent provide new opportunities to assess the influence of cloud forcing and feedbacks on sea ice loss in observations and models. … Our results indicate large-scale atmospheric circulation patterns and sea surface temperatures primarily controlled Arctic cloud forcing. Cloud feedback on sea ice extent loss is important because it can amplify or dampen ice loss processes. … We find that the observed cloud feedbacks are not well represented in either assimilation system. We explore reasons for incorrect model cloud feedbacks and the implications for the radiative forcing on projected sea ice loss.” [Presentation material]

Evaluation of Cloud Feedback at Local Scale: Warming or Cooling? – Malek (2009) A conference paper. “To evaluate cloudiness and its feedback at local scale, a radiation station was set up, which used two CM21 Kipp & Zonen pyranometers (one inverted), and two CGI Kipp & Zonen pyrgeometers (one inverted) in Logan, Utah, USA. … As shown, due to cloudiness at the experimental site, the net radiation loss was 2791−3707 = −916 MJ m⁻² y⁻¹, which indicates cooler temperature and a negative feedback due to cloudiness.”

Cloud radiative forcing of subtropical low level clouds in global models – Karlsson et al. (2008) “Simulations of subtropical marine low clouds and their radiative properties by nine coupled ocean-atmosphere climate models participating in the fourth assesment report (AR4) of the intergovernmental panel on climate change (IPCC) are analyzed. Satellite observations of cloudiness and radiative fluxes at the top of the atmosphere (TOA) are utilized for comparison. … As a consequence of the combination of these two biases, this study suggests that all investigated models are likely to overestimate the radiative response to changes in low level subtropical cloudiness.”

Cloud Feedbacks in the Climate System: A Critical Review – Stephens (2005) A review article. “This paper offers a critical review of the topic of cloud–climate feedbacks and exposes some of the underlying reasons for the inherent lack of understanding of these feedbacks and why progress might be expected on this important climate problem in the coming decade. … Models provide the tool for diagnosing processes and quantifying feedbacks while observations provide the essential test of the model’s credibility in representing these processes. … Aspects of these parameterizations remain worrisome, containing levels of empiricism and assumptions that are hard to evaluate with current global observations. Clearly observationally based methods for evaluating cloud parameterizations are an important element in the road map to progress.” [Link to PDF]

The Iris Hypothesis: A Negative or Positive Cloud Feedback? – Lin et al. (2002) “Using the Tropical Rainfall Measuring Mission (TRMM) satellite measurements over tropical oceans, this study evaluates the iris hypothesis recently proposed by Lindzen et al. that tropical upper-tropospheric anvils act as a strong negative feedback in the global climate system. The modeled radiative fluxes of Lindzen et al. are replaced by the Clouds and the Earth’s Radiant Energy System (CERES) directly observed broadband radiation fields. The observations show that the clouds have much higher albedos and moderately larger longwave fluxes than those assumed by Lindzen et al. As a result, decreases in these clouds would cause a significant but weak positive feedback to the climate system, instead of providing a strong negative feedback.” [Link to PDF]

Influence of cloud feedback on annual variation of global mean surface temperature – Tsushima & Manabe (2001) “The goal of this study is to estimate the cloud radiative feedback effect on the annual variation of the global mean surface temperature using radiative flux data from the Earth Radiation Budget Experiment. We found that the influence of the cloud feedback upon the change of the global mean surface temperature is quite small, though the increase of the temperature is as much as 3.3 K from January to July. On a global scale, we found no significant relationship between either solar reflectivity of clouds or effective cloud top height and the annual cycle of surface temperature.” [Link to PDF]

Cloud Feedbacks – Randall et al. (2000) A symposium paper. “The observational literature contains some evidence of cloud feedbacks on decadal time scales. Recent work shows that global atmospheric circulation models (AGCMs) are capable of simulating many observed fluctuations of cloudiness.” [Link to PDF]

Interannual Variability in Stratiform Cloudiness and Sea Surface Temperature – Norris & Leovy (1994) “Long-term datasets of cloudiness and sea surface temperature (SST) from surface observations from 1952 to 1981 are used to examine interannual variations in MSC and SST. Linear correlations of anomalies in seasonal MSC amount with seasonal SST anomalies are negative and significant in midlatitude and eastern subtropical oceans, especially during summer. Significant negative correlations between SST and nimbostratus and nonprecipitating midlevel cloudiness are also observed at midlatitudes during summer, suggesting that summer storm tracks shift from year to year following year-to-year meridional shifts in the SST gradient. Over the 30-yr period, there are significant upward trends in MSC amount over the northern midlatitude oceans and a significant downward trend off the coast of California. The highest correlations and trends occur where gradients in MSC and SST are strongest.” [Link to PDF]

Cirrus-cloud thermostat for tropical sea surface temperatures tested using satellite data – Fu et al. (1992) “Ramanathan and Collins have suggested cirrus clouds associated with tropical convection might act as a ‘thermostat’ to limit tropical sea surface temperatures (SSTs) to less than 305 K by shielding the ocean from sunlight. Here we use satellite radiance data to test this hypothesis. We find that changes in the properties of cirrus clouds do not seem to be related to changes in SSTs. During the 1987 El Niño event, large-scale perturbations to the radiative effects of cirrus clouds were controlled by changes in large-scale atmospheric circulation rather than directly by SSTs. If they are averaged over the entire tropical Pacific, increases in surface evaporative cooling are stronger than decreases in solar heating owing to cirrus cloud variations. Thus we conclude that there is no ‘cirrus cloud thermostat’ to tropical SSTs.” [Link to PDF]

Thermodynamic regulation of ocean warming by cirrus clouds deduced from observations of the 1987 El Niño – Ramanathan & Collins (1991) “Observations made during the 1987 El Niño show that in the upper range of sea surface temperatures, the greenhouse effect increases with surface temperature at a rate which exceeds the rate at which radiation is being emitted from the surface. In response to this ’super greenhouse effect’, highly reflective cirrus clouds are produced which act like a thermostat shielding the ocean from solar radiation. The regulatory effect of these cirrus clouds may limit sea surface temperatures to less than 305 K.” [Link to PDF]

Closely related

Papers on global cloud cover trends
Papers on the albedo of the Earth