The IPCC Third Assessment Report on the Scientific Basis of Climate Change

The Intergovernmental Panel on Climate Change (IPCC) has recently completed its Third Assessment Report on the Scientific Basis of Climate Change. The report builds on previous IPCC assessment reports in 1990 and 1995 and has been in preparation for the past three and a half years through the work of more than 500 scientists world wide who have been taking stock of the research findings reported in some 4000 peer—reviewed scientific papers. The report consists of a Summary for Policymakers, a Technical Summary and an underlying detailed report of fourteen chapters. The Summary for Policymakers was approved on a line by line basis by an intergovernmental session of the science working group (Working Group 1) of the IPCC, held in Shanghai, China on 17–20 January 2001, with the participation of some 45 of the 122 Lead Authors and official government delegations from 99 countries. The report concludes that, although many uncertainties remain, the past five years of observations and research have provided stronger evidence than hitherto of a human impact on global climate and increased confidence in the capability of climate models to project future global climate trends for a range of emission scenarios through the twenty first century. This article, which is based, in part, on the author's experience as Principal Delegate of Australia to the IPCC and as a member of the IPCC Bureau since 1994, describes the operation of the IPCC assessment process and the preparation, approval and main conclusions of the science component of the Third Assessment Report.