HR: 08:45h
AN: U51B-04 INVITED    [Abstracts]
TI: Estimating the sensitivity of the climate system to CO2 forcing from observed climate change
AU: * Hegerl, G
EM: Gabi.Hegerl@ed.ac.uk
AF: GeoSciences,University of Edinburgh, Grant Institute, The King's Buildings West Mains Road EDINBURGH, Edinburgh, EH9 3JW, United Kingdom
AU: Knutti, R
AF: Institute for Atmospheric and Climate Science, ETH Zuerich, Universitaetsstr 16, Zuerich, 80092, Switzerland
AU: Allen, M
AF: University of Oxford Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory Parks Road, Oxford, OX1 3PU, United Kingdom
AB: Observations of climate change over the 20th century and over recent paleoclimatic periods have been used to estimate the equilibrium climate sensitivity, which is the global mean equilibrium warming in response to a doubling of CO2 in the atmosphere. This talk compares the evidence and the uncertainties in different lines of evidence, including 20th century warming, Northern Hemispheric climate changes over the last millennium and data for the Last Glacial maximum. While most lines of evidence render very small climate responses or negative feedbacks unlikely, constraining the equilibrium climate sensitivity at the upper range remains difficult. However, the available information, taken together, yields very high climate change less likely than each individual line of evidence suggests. However, when using multiple lines of evidence of climate change, important questions arise about the independence of information used, and if the feedbacks that are sampled in the observed climate change fully span the feedbacks important to drive the climate systems response to CO2 doubling. The talk concludes with a discussion of limitations of equilibrium climate sensitivity, and ideas how to move beyond it.
DE: 1610 Atmosphere (0315, 0325)
SC: Union [U]
MN: 2007 Fall Meeting