IPCC Third Assessment Report - Scientific Opinion

Scientific Opinion

The IPCC is backed by the scientific community. For example, a joint statement of support was issued in May 2001 by the science academies of Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden and the UK. It states: "We recognise the IPCC as the world's most reliable source of information on climate change and its causes, and we endorse its method of achieving consensus."

In 2001, the executive branch of the US federal government asked the US National Research Council (US NRC, 2001) to produce an assessment of climate change science. Part of the assessment by US NRC (2001) looks at the report produced by Working Group I (WG I) in the TAR. Working Group I's contribution to the TAR assesses the physical scientific aspects of the climate system and climate change. US NRC (2001) generally agrees with findings of the WG I report, for example, US NRC (2001) state that " IPCC’s conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue."

US NRC (2001) emphasize the need for governments to have a good understanding of uncertainties in climate change science. The example cited by US NRC (2001) is the uncertainty over future changes in GHG emissions, which may be less or more than that projected by the TAR. US NRC (2001) also state:

The most valuable contribution U.S. scientists can make is to continually question basic assumptions and conclusions, promote clear and careful appraisal and presentation of the uncertainties about climate change as well as those areas in which science is leading to robust conclusions, and work toward a significant improvement in the ability to project the future.