Its reports are widely cited and have been highly influential in forming national and international responses to climate change, yet some of the scientists whose work is summarized in these reports have accused the IPCC of bias.
Aims
The aims of the IPCC are threefold:
The IPCC is led by government scientists, but also involves several hundred academic scientists and researchers. It synthesises the available information about climate change and global warming, has published four major reports reviewing the latest climate science, as well as more specialized reports.
The current head of IPCC is Rajendra K. Pachauri, elected in May 2002; previously Robert Watson headed the IPCC.
As a summary of current peer reviewed and published science, each IPCC report notes areas where the science has improved since the previous report (except the first one, of course), and also notes areas where further research is required.
The IPCC published a first assessment report in 1990, a supplementary report in 1992, a second assessment report (SAR) in 1995, and a third assessment report (TAR) in 2001. Each of the assessment reports is in three volumes from the working groups I, II and III. Unqualified, "the IPCC report" is often used to mean the WG I report.
The most recent IPCC report is Climate Change 2001, the Third Assessment Report (TAR) WG I report.
The "headlines" from the summary for policymakers in the WG I report [1] were:
IPCC predictions are based on the same models used to establish the importance of the different factors in global warming.
These models need data about anthropogenic emissions of greenhouse gases and aerosols.
These data are predicted from economic models based on 35 different scenarios.
Scenarios go from pessimistic to optimistic, and predictions of global warming depend on the kind of scenario considered.
IPCC uses the best available predictions and their reports are under strong scientific scrutiny.
The IPCC concedes that there is a need for better models and better scientific understanding of some climate phenomena, as well as the uncertainties involved.
Critics point out that the available data is not sufficient to determine the real importance of greenhouse gases in climate change.
Sensitivity of climate to greenhouse gases may be over-estimated or under-estimated estimated because of some flaws in the models and because the importance of some external factors may be misestimated.
On the other hand, predictions are based on scenarios, and the IPCC did not assign any probability to the 35 scenarios used.
Castles and Henderson asserted that the IPCC has been using inflated economic growth rates, which result in increased emission estimates. [1] This was incorrect because IPCC growth and emissions rates were based upon several factors and not only GDP, as rebutted by Nebojsa Nakicenovic et al.
A few participants in IPCC Working Group I (Science) do not agree with the IPCC reports (of the 120 lead authors, 2 have complained [1]). A particularly active critic, MIT physicist Richard Lindzen, expressed his unhappiness about those portions in the Executive Summary based on his contributions in May 2001 before the United States Senate Commerce Committee:
These statements are in turn supported by the executive summary of chapter 8 of the report, which includes:
The report formed the basis of negotiations over the Kyoto Protocol.
A December 20, 1995, Reuters report quoted British scientist Keith Shine, one of IPCC's lead authors, discussing the Policymakers' Summary. He said: "We produce a draft, and then the policymakers go through it line by line and change the way it is presented.... It's peculiar that they have the final say in what goes into a scientists' report." It is not clear, in this case, whether Shine was complaining that the report had been changed to be more skeptical, or less, or something else entirely.
Dr. Frederick Seitz, president emeritus of Rockefeller University and past president of the National Academy of Sciences, has publicly denounced the IPCC report, writing "I have never witnessed a more disturbing corruption of the peer-review process than the events that led to this IPCC report". He opposed it in the Leipzig Declaration of his Science and Environmental Policy Project.
The 1992 supplementary report was an update, requested in the context of the negotiations on the Framework Convention on Climate Change, and the United Nations Conference on Environment and Development (Rio de Jaeiro, 1992).
The major conclusion was that research since 1990 did "not affect our fundamental understanding of the science of the greenhouse effect and either confirm or do not justify alteration of the major conclusions of the first IPCC scientific assessment". It noted that transient (time-dependent) simulations, which had been very preliminary in the FAR, were now improved, but did not include aerosol or ozone changes.
The IPCC first assessment report was completed in 1990, and served as the basis of the United Nations Framework Convention on Climate Change (UNFCCC).
The executive summary of the policymakers summary of the WG I report includes:
In 1991, the SEPP surveyed IPCC contributors and researchers, along with a comparison group of global warming skeptics who had not contributed. [1]
Publications
IPCC Third Assessment Report: Climate Change 2001
In its last report, IPCC stated that average surface temperature is projected to increase by 1.4 to 5.8 Celsius degrees over the period 1990 to 2100, and the sea level is projected to rise by 0.1 to 0.9 metres over the same period. The wide range in predictions is based upon several different scenarios that assume different levels of future CO2 emissions. Each scenario then has a range of possible outcomes associated with it. The most optimistic outcome assumes an aggressive campaign to reduce CO2 emssions, while the most pessimistic is a "business as usual" scenario. The more realistic scenarios fall in between.Debate over Climate Change 2001
The "Summary for Policymakers" of the WG1 reports does include caveats on model treatments: Such models cannot yet simulate all aspects of climate (e.g., they still cannot account fully for the observed trend in the surface-troposphere temperature difference since 1979) and there are particular uncertainties associated with clouds and their interaction with radiation and aerosols. Nevertheless, confidence in the ability of these models to provide useful projections of future climate has improved due to their demonstrated performance on a range of space and time-scales. [1].IPCC Second Assessment Report: Climate Change 1995
Climate Change 1995, the IPCC Second Assessment Report (SAR) was finished in 1996. It is split into four parts:
Each of the last three parts was completed by a separate working group, and each has a Summary for Policymakers (SfP) that represents a consensus of national representatives. The SfP of the WG I report contains headings:Debate over Climate Change 1995
Most scientists involved in climate research believe that the IPCC reports accurately summarise the state of knowledge. Some scientists and scientific organizations have objected and made public comments to that effect.IPCC supplementary report, 1992
IPCC First Assessment Report: 1990
Notice that the report did *not* attribute the observed warming to human influence.External Links