GLOBAL WARMING: The Scientific Assessment
The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 to provide a scientific assessment of climate change and its anthropogenic causes, as well as possible impacts on people. The IPCC was split into Working Groups to address three separate areas: the scientific aspects of the climate system; the impacts of climate change and possible adaptations; and the options for mitigation of climate change. The IPCC has published three reports (1990, 1996 and the latest in 2001). This newest Third Assessment Report (TAR) builds upon the previous work and incorporates the latest results in climate research.
The IPCC reports can be downloaded for free from http://www.ipcc.ch
In the IPCC’s Third Assessment Report, Working Group I offers the following statements:
Is the Earth’s climate changing? The answer is unequivocally “Yes”. A suite of evidence supports this conclusion and provides insight about the rapidity of those changes. These data are also the bedrock upon which to construct the answer to the more difficult question: “Why is it changing?”
This last question is answered with a detailed presentation of the latest evidence including:
- Three of the last five years of the 1990s decade (1995, 1997, and 1998) were the warmest globally in the instrumental record.
- There is a wide range of evidence of qualitative consistencies between observed climate changes and [computer] model responses to anthropogenic forcing.
- Evidence of a human influence on climate is obtained over a substantially wider range of detection techniques.
Despite some remaining uncertainties, such as the precise impact of aerosols (particles and droplets suspended in air) and the considerable differences in response by different computer models to the same greenhouse gas forcing, the IPCC came to the strong conclusion that:
‘In light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.’
More about the Keeling curve.