Patterns of change: whose fingerprint is seen in global warming?

Attributing observed climate change to causes is challenging. This letter communicates the physical arguments used in attribution, and the statistical methods applied to explore to what extent different possible causes can be used to explain the recent climate records. The methods use fingerprints of climate change that are identified on the basis of the physics governing our climate system, and through the use of climate model experiments. These fingerprints characterize the geographical and vertical pattern of the expected changes caused by external influences, for example, greenhouse gas increases and changes in solar radiation, taking also into account how these forcings and their effects vary over time. These time‐space fingerprints can be used to discriminate between observed climate changes caused by different external factors. Attribution assessments necessarily take the natural variability of the climate system into account as well, evaluating whether an observed change can be explained in terms of this internal variability alone, and estimating the contribution of this source of variability to the observed change. Hence the assessment that a large part of the observed recent warming is anthropogenic is based on a rigorous quantitative analysis of these joint drivers and their effects, and proceeds through a much more comprehensive and layered analysis than a comparison at face value of model simulations with observations.

[1]  H. Storch,et al.  Statistical Analysis in Climate Research , 2000 .

[2]  Myles R. Allen,et al.  Observational Constraints on Past Attributable Warming and Predictions of Future Global Warming , 2006 .

[3]  Michael E. Schlesinger,et al.  An oscillation in the global climate system of period 65–70 years , 1994, Nature.

[4]  Reto Knutti,et al.  Early onset of significant local warming in low latitude countries , 2011 .

[5]  Mike Lockwood,et al.  SOLAR INFLUENCES ON CLIMATE , 2009 .

[6]  G. Hegerl,et al.  Detection of Human Influence on a New, Validated 1500-Year Temperature Reconstruction , 2007 .

[7]  John E. Harries,et al.  Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997 , 2001, Nature.

[8]  John R. Lanzante,et al.  Stratospheric temperature trends: our evolving understanding , 2011 .

[9]  Michael K. Tippett,et al.  A Significant Component of Unforced Multidecadal Variability in the Recent Acceleration of Global Warming , 2011 .

[10]  Thomas C. Peterson,et al.  Tropospheric temperature trends: history of an ongoing controversy , 2011 .

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

[12]  M. Noguer,et al.  Climate change 2001: The scientific basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change , 2002 .

[13]  S. Solomon.  The Physical Science Basis : Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , 2007 .

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

[15]  Vincent R. Gray.  Climate Change 2007: The Physical Science Basis Summary for Policymakers , 2007 .

[16]  T. Delworth,et al.  Can the Atlantic Ocean drive the observed multidecadal variability in Northern Hemisphere mean temperature? , 2007 .

[17]  P. Stott,et al.  Do Models Underestimate the Solar Contribution to Recent Climate Change , 2003 .

[18]  Francis W. Zwiers,et al.  Use of models in detection and attribution of climate change , 2011 .

[19]  M. Schlesinger,et al.  Implications for global warming of intercycle solar irradiance variations , 1992, Nature.

[20]  T. Delworth,et al.  Probing the Fast and Slow Components of Global Warming by Returning Abruptly to Preindustrial Forcing , 2010 .

[21]  G. Hegerl,et al.  Understanding and Attributing Climate Change , 2007 .

[22]  Jeffrey T. Kiehl,et al.  Twentieth century climate model response and climate sensitivity , 2007 .

[23]  Jonathan M. Gregory,et al.  Mechanisms for the land/sea warming contrast exhibited by simulations of climate change , 2008 .

[24]  Francis W. Zwiers,et al.  Detection and attribution of climate change: a regional perspective , 2010 .

[25]  B. Santer,et al.  Penetration of Human-Induced Warming into the World's Oceans , 2005, Science.

[26]  K. Hasselmann.  Stochastic climate models Part I. Theory , 1976 .

[27]  S. Levitus,et al.  Warming of the World Ocean , 2000 .

[28]  Alan Robock,et al.  Global cooling after the eruption of Mount Pinatubo: a test of climate feedback by water vapor. , 2002, Science.

[29]  P. Imkeller,et al.  Stochastic climate models , 2001 .

[30]  S. Solomon.  IPCC (2007): Climate Change The Physical Science Basis , 2007 .

[31]  Molly O. Baringer,et al.  State of the Climate in 2009 , 2010 .

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

[33]  J. Wallace,et al.  A Pacific Interdecadal Climate Oscillation with Impacts on Salmon Production , 1997 .

[34]  K. Hasselmann.  On the signal-to-noise problem in atmospheric response studies , 1979 .

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

[36]  P. Jones,et al.  Uncertainty estimates in regional and global observed temperature changes: A new data set from 1850 , 2006 .