IPCC Workshop Report on Climate Sensitivity

The IPCC Working Group I (WGI) held a Workshop on Climate Sensitivity on 26-29 July 2004 in Paris, France, as a major keystone in activities preparing for the WGI contribution to the IPCC Fourth Assessment Report (AR4).
Throughout the last three IPCC assessments the climate sensitivity has been estimated as being in the range 1.5 to 4.5°C for CO2 doubling (i.e., uncertain by a factor of three), making this parameter central to discussions of uncertainty in climate change. Some recent studies have suggested that new insights into the likely range of climate sensitivity may be possible through comparisons of models and observational data - both contemporary and historical or paleoclimatic. Observation/model intercomparisons were a special focus of the workshop in Paris.
The workshop was structured around four topics:

• Climate sensitivity from models
• Climate sensitivity from observations (including modern and paleoclimatic observations)
• Radiative transfer and forcing
• Probabilistic measures of climate sensitivity

The Workshop Report is published in September 2004 by the IPCC Working Group I Technical Support Unit, Boulder, Colorado, USA.
Electronic copies of the report are available from the IPCC website