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published by IISD, the International Institute for Sustainable Development
in cooperation with the Climate Change Secretariat.
Special Report on Selected Side Events at SB 22
19-27 May 2005 | Bonn, Germany
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Brief Analysis

Event convened on Thursday, 26 May 2005

Simulations of global climate change commitment for the IPCC AR4

Presented by the University Corporation for Atmospheric Research

William Collins, National Center for Atmospheric Research, introduced simulations for the IPCC’s fourth assessment report (AR4). He presented the Community Climate System Model (CCSM) and explained that the models used for the AR4 have produced realistic predictions and can simulate: mean sea-surface temperatures to within 0.03C; ocean heat uptake to within 25%; and ocean uptake of tracers to within 10%.

Collins outlined climatic effects based on several scenarios for changes in carbon dioxide concentrations for the 21st to 23rd centuries, from a “stabilization” scenario, involving stabilization of carbon dioxide concentrations at 20th century levels, to a “business-as-usual” scenario, involving an increase of 250%. He highlighted: the likelihood of polar amplification; and a 10 to 25cm rise in sea levels from the “stabilization” through to “business-as-usual” scenarios, noting that these projections do not account for ice sheet melting. He also explained that under the “business-as-usual” scenario, there could be no Arctic sea ice during summer time by the end of the 21st century.

Collins then discussed projected climatic changes based on a combined analysis of 12 climate models in the IPCC archive, including: an increase in global surface temperature by 0.5C over the 21st century; an average sea level rise of 10cm; polar amplification; and the possibility of an “El Niño-like signature,” where the eastern Atlantic Ocean warms more than the western part. He noted that the models indicate few statistically significant changes for precipitation other than a slight increase in the strength of the Indian monsoon and a weakening of the US monsoon. He concluded that all the models used for the AR4 predict global warming over the next century and highlighted that the actual effects of global warming are likely to be considerably larger than the committed change.

William Collins, National Center for Atmospheric Research, highlighted aerosol as one of the particular challenges for climate simulations

Discussion: Participants discussed issues associated with the models used, including: reasons for their use; existing uncertainties; their availability; and differences between these and other models. The discussion also addressed, inter alia: regional precipitation changes; warming differences between the tropics and the poles; the fact that “floating ice” melting does not contribute to sea level rise; the introduction of black carbon to the poles; and the inclusion of more information on the carbon cycle model and biogeochemistry in the AR4.

William Collins <>

COP 11, COP/MOP 1, SB 23

United Nations Climate Conference: Montreal 2005

A reception hosted by Canada on 25 May 2005

The Earth Negotiations Bulletin on the side (ENBOTS) © <> is a special publication of the International Institute for Sustainable Development (IISD) in cooperation with the United Nations Framework Convention on Climate Change (UNFCCC) Secretariat. This issue has been written by Ingrid Barnsley, Alice Bisiaux, Maria Larsson Ortino, and Kati Kulovesi. The photographer is Leila Mead. The Digital Editor is Diego Noguera. The Editor is Lisa Schipper, Ph.D. <>. The Director of IISD Reporting Services is Langston James “Kimo” Goree VI <>. Funding for the publication of ENBOTS at UNFCCC SB 22 is provided by the UNFCCC Secretariat. The opinions expressed in ENBOTS are those of the authors and do not necessarily reflect the views of IISD and funders. Excerpts from ENBOTS may be used in non-commercial publications only with appropriate academic citation. For permission to use this material in commercial publications, contact the Director of IISD Reporting Services at <>. Electronic versions of issues of ENBOTS from SB 22 can be found on the Linkages website at The ENBOTS Team at SB 22 can be contacted by e-mail at <>.

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