Atmospheric science: Methane rises from wetlands

Recent reconstructions of Northern Hemisphere temperatures and climate forcing over the past 1000 years allow the warming of the 20th century to be placed within a historical context and various mechanisms of climate change to be tested. Comparisons of observations with simulations from an energy balance climate model indicate that as much as 41 to 64% of preanthropogenic (pre-1850) decadal-scale temperature variations was due to changes in solar irradiance and volcanism. Removal of the forced response from reconstructed temperature time series yields residuals that show similar variability to those of control runs of coupled models, thereby lending support to the models' value as estimates of low-frequency variability in the climate system. Removal of all forcing except greenhouse gases from the approximately 1000-year time series results in a residual with a very large late-20th-century warming that closely agrees with the response predicted from greenhouse gas forcing. The combination of a unique level of temperature increase in the late 20th century and improved constraints on the role of natural variability provides further evidence that the greenhouse effect has already established itself above the level of natural variability in the climate system. A 21st-century global warming projection far exceeds the natural variability of the past 1000 years and is greater than the best estimate of global temperature change for the last interglacial.

[1]  G. Denton,et al.  Holocene Climatic Variations—Their Pattern and Possible Cause , 1973, Quaternary Research.

[2]  C. Hammer.  Past volcanism revealed by Greenland Ice Sheet impurities , 1977, Nature.

[3]  André Berger,et al.  Long-Term Variations of Caloric Insolation Resulting from the Earth's Orbital Elements , 1978, Quaternary Research.

[4]  A. Robock.  The "Little Ice Age": Northern Hemisphere Average Observations and Model Calculations , 1979, Science.

[5]  W. Dansgaard,et al.  Greenland ice sheet evidence of post-glacial volcanism and its climatic impact , 1980, Nature.

[6]  J. D. Hays,et al.  The Last Interglacial Ocean , 1984, Quaternary Research.

[7]  T. Wigley,et al.  Thermal expansion of sea water associated with global warming , 1987, Nature.

[8]  R. Turco,et al.  Self-limiting physical and chemical effects in volcanic eruption clouds , 1989 .

[9]  kwang-yul kim,et al.  On the relation between polar continentality and climate: Studies with a nonlinear seasonal energy balance model , 1990 .

[10]  T. Wigley,et al.  Natural variability of the climate system and detection of the greenhouse effect , 1990, Nature.

[11]  E. Friis-christensen,et al.  Length of the Solar Cycle: An Indicator of Solar Activity Closely Associated with Climate , 1991, Science.

[12]  S. Baum,et al.  Climate model comparison of Gondwanan and Laurentide glaciations , 1991 .

[13]  J. Lean,et al.  Estimating the Sun's radiative output during the Maunder Minimum , 1992 .

[14]  J. Houghton,et al.  Climate change 1992 : the supplementary report to the IPCC scientific assessment , 1992 .

[15]  G. Bonan,et al.  Effects of boreal forest vegetation on global climate , 1992, Nature.

[16]  T. Wigley,et al.  Solar cycle length, greenhouse forcing and global climate , 1992, Nature.

[17]  M. Stuiver,et al.  Modeling Atmospheric 14C Influences and 14C Ages of Marine Samples to 10,000 BC , 1993, Radiocarbon: An International Journal of Cosmogenic Isotope Research.

[18]  Douglas V. Hoyt,et al.  A discussion of plausible solar irradiance variations, 1700-1992 , 1993 .

[19]  J. Hansen,et al.  Stratospheric aerosol optical depths, 1850–1990 , 1993 .

[20]  J. Overpeck,et al.  Hypothesized causes of decade-to-century-scale climate variability: Climate model results , 1993 .

[21]  S. Idso,et al.  Detecting the aerial fertilization effect of atmospheric CO2 enrichment in tree‐ring chronologies , 1993 .

[22]  T. Crowley,et al.  Reassessment of Crete (Greenland) ice core acidity/volcanism link to climate change , 1993 .

[23]  kwang-yul kim,et al.  Towards development of a strategy for determining the origin of decadal-centennial scale climate variabiligy , 1993 .

[24]  E. Werker,et al.  Early medical use of cannabis , 1993, Nature.

[25]  J. Oerlemans.  Quantifying Global Warming from the Retreat of Glaciers , 1994, Science.

[26]  kwang-yul kim,et al.  Modeling the climate effect of unrestricted greenhouse emissions over the next 10,000 years , 1994 .

[27]  Remo Guidieri.  Res , 1995, RES: Anthropology and Aesthetics.

[28]  G. Zielinski.  Stratospheric loading and optical depth estimates of explosive volcanism over the last 2100 years derived from the Greenland Ice Sheet Project 2 ice core , 1995 .

[29]  R. Pielke,et al.  The boreal forest and the polar front , 1995 .

[30]  J. Lean,et al.  Reconstruction of solar irradiance since 1610: Implications for climate change , 1995 .

[31]  M. Stuiver,et al.  The GISP2 δ18O Climate Record of the Past 16,500 Years and the Role of the Sun, Ocean, and Volcanoes , 1995, Quaternary Research.

[32]  C. Hammer,et al.  A 10‐century comparison of prominent bipolar volcanic events in ice cores , 1995 .

[33]  T. C. Johns,et al.  A search for human influences on the thermal structure of the atmosphere , 1995, Nature.

[34]  Reply to Comment by Jacoby and D'Arrigo , 1996 .

[35]  Jean Jouzel,et al.  Climatic Variations and Forcing Mechanisms of the Last 2000 Years , 1996 .

[36]  Benjamin D. Santer,et al.  Estimates of low frequency natural variabilit in near-surface air temperature , 1996 .

[37]  Kwang-Yul Kim,et al.  Comparison of proxy records of climate change and solar forcing , 1996 .

[38]  D. Etheridge,et al.  Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn , 1996 .

[39]  C. P. Sonnett.  Climatic variations and forcing mechanisms of the last 2000 years , 1997 .

[40]  U. Cubasch,et al.  Simulation of the influence of solar radiation variations on the global climate with an ocean-atmosphere general circulation model , 1997 .

[41]  Konrad A Hughen,et al.  Arctic Environmental Change of the Last Four Centuries , 1997 .

[42]  J. Jouzel,et al.  Solar modulation of cosmogenic nuclide production over the last millennium: comparison between 14C and 10Be records , 1997 .

[43]  Christopher R. J. Kilburn,et al.  Volcanoes of the World , 1997 .

[44]  M. R. Allen,et al.  Checking for model consistency in optimal fingerprinting , 1999 .

[45]  R. Voss,et al.  Multi-fingerprint detection and attribution analysis of greenhouse gas, greenhouse gas-plus-aerosol and solar forced climate change , 1997 .

[46]  R. Sausen,et al.  Periodically synchronously coupled integrations with the atmosphere-ocean general circulation model ECHAM3/LSG , 1998 .

[47]  F. H. Schweingruber,et al.  Influence of volcanic eruptions on Northern Hemisphere summer temperature over the past 600 years , 1998, Nature.

[48]  Malcolm K. Hughes,et al.  Global-scale temperature patterns and climate forcing over the past six centuries , 1998, Nature.

[49]  H. Storch,et al.  Temperatures at the last interglacial simulated by a coupled ocean‐atmosphere climate model , 1998 .

[50]  Gerald R. North,et al.  Detecting Climate Signals in the Surface Temperature Record , 1998 .

[51]  C. C. Chuang,et al.  Climate forcing by carbonaceous and sulfate aerosols , 1998 .

[52]  G. Myhre,et al.  New estimates of radiative forcing due to well mixed greenhouse gases , 1998 .

[53]  V. Ramaswamy,et al.  Global sensitivity studies of the direct radiative forcing due to anthropogenic sulfate and black carbon aerosols , 1998 .

[54]  Klaus Hasselmann,et al.  Detection and Attribution of Recent Climate Change: A Status Report , 1999 .

[55]  Alan Robock,et al.  Global warming in the context of the Little Ice Age , 1999 .

[56]  T. Peng,et al.  A possible 20th-century slowdown of southern ocean deep water formation , 1999, Science.

[57]  kwang-yul kim,et al.  Modeling the temperature response to forced climate change over the last six centuries , 1999 .

[58]  P. Damon,et al.  Solar cycle length and 20th Century northern hemisphere warming: Revisited , 1999 .

[59]  Mark New,et al.  Surface air temperature and its changes over the past 150 years , 1999 .

[60]  J. Majorowicz,et al.  Regional climatic warming and associated twentieth century land-cover changes in north-western North America , 1999 .

[61]  John F. B. Mitchell,et al.  Causes of twentieth-century temperature change near the Earth's surface , 1999, Nature.

[62]  M. Lockwood,et al.  Long‐term drift of the coronal source magnetic flux and the total solar irradiance , 1999 .

[63]  M. Hughes,et al.  Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations , 1999 .

[64]  Judith Lean,et al.  Evaluating sun–climate relationships since the Little Ice Age , 1999 .

[65]  Signature of superfluid density in the single-particle excitation spectrum of Bi2Sr2CaCu2O8+δ , 2000, cond-mat/0009306.

[66]  T. Delworth,et al.  Simulation of early 20th century global warming , 2000, Science.

[67]  T. Crowley,et al.  How Warm Was the Medieval Warm Period , 2000 .

[68]  Gabriele C. Hegerl,et al.  A Comparison of Surface Air Temperature Variability in Three 1000-Yr Coupled Ocean–Atmosphere Model Integrations , 2000 .

[69]  K. Briffa.  Annual climate variability in the Holocene: interpreting the message of ancient trees , 2000 .

[70]  Shaopeng Huang,et al.  Temperature trends over the past five centuries reconstructed from borehole temperatures , 2000, Nature.

[71]  H. Storch,et al.  Climate Simulation for 125 kyr BP with a Coupled Ocean-Atmosphere General Circulation Model , 2000 .

[72]  P. J. Rasch,et al.  Radiative forcing due to sulfate aerosols from simulations with the National Center for Atmospheric Research Community Climate Model, Version 3 , 2000 .

[73]  J. Jouzel,et al.  Solar irradiance during the last 1200 years based on cosmogenic nuclides , 2000 .

[74]  Probability of Future Climatically Significant Volcanic Eruptions , 2000 .

[75]  Signature of superfluid density in the single-particle excitation spectrum of Bi(2)Sr(2)CaCu(2)O(8+delta) , 2000, Science.