Seminars

Seminar Abstract

Integrating the science and economics of climate change and the role of the oceans

Global climate change is in the news and is the subject of policy debate within most nations. It is also the subject of ongoing international negotiations in the Framework Convention on Climate Change and its Kyoto Protocol. To inform processes of policy development and implementation there is urgent need for better integration of the diverse components of the problem. Climate research needs to focus on predictions that relate to economic, social, and environmental effects. Forecasts of greenhouse gases and atmospheric aerosols, should take account of the economic, technological, and political forces that drive emissions. Assessments of possible societal and ecosystem impacts, and the analysis of alternative strategies for mitigation or adaptation, need to be based on realistic evaluations of the uncertainties of climate science and the likely paths to their reduction.

Motivated by the challenge of bringing together these diverse elements, the MIT Joint Program on the Science and Policy of Global Change has developed an Integrated Global System Model (IGSM) comprising coupled sub-models of economic development, atmospheric chemistry, climate dynamics and ecosystems. One important goal of the Program is to carefully analyze the scientific and economic implications of proposed policies. Another important goal of the Program is to provide objective estimates of the uncertainty in projections of climate change and its impacts. Such estimates are crucial information for decision makers as they evaluate policies to reduce the risk of climate impacts. The results of an uncertainty analysis involving hundreds of runs of the IGSM imply that, without specific mitigation policies, the global average surface temperature may rise between 1.0 and 4.9?C from 1990 to 2100 (95% confidence limits). Polar temperatures, absent policy, are projected to rise from about 2 to 12?C (95% limits) with obvious great risks for high latitude ecosystems and ice sheets at the high end of this range.

Analysis of the Kyoto Protocol, and more stringent climate mitigation policies, shows the disparities among countries in economic costs and the difficulties in accounting simply for the effects of other greenhouse gases relative to carbon dioxide. Also, the greatest effect of these policies is to lower the probability of extreme changes as opposed to lowering the medians. There is 1 chance in 10 of warming exceeding 3.8?C in the above no policy case, but less than 1 chance in 250 if a policy aimed at keeping carbon dioxide levels below twice their preindustrial values is adopted.

The ocean plays a key role in global climate through its meridional and vertical transport of heat and carbon. Uncertainty in the deep oceanic circulation is one of the three leading uncertainties in the natural climate system which contributes to the above wide ranges in projected warming. Recent work at MIT implies that current ocean models are significantly overestimating vertical transport and that the deep circulation may almost cease if radiative forcing and climate sensitivity are sufficiently large.

Faced with the above estimated odds, the long lifetimes of most greenhouse gases in the atmosphere, the long delay in ultimate warming due to ocean heat uptake, and the capital-intensive global energy infrastructure, the case is strong for beginning action now. The challenge is to devise national and international approaches to this problem.

* Member of Advanced Global Atmospheric Gases Experiment (AGAGE)

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CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
Karen Wild-Allen, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5010
Piers Dunstan, (Biological seminars) CSIRO Marine and Atmospheric Research (03) 6232 5382
Sandra Zicus, Antarctic Climate and Ecosystems CRC (03) 6226 7888 & Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2509