Criticism of the IPCC Fourth Assessment Report

The IPCC Fourth Assessment Report (AR4) has been subjected to both scientific and non scientific (process based) criticism. Scientific criticism can broadly be broken down into criticism that the report either greatly understates or greatly overstates the dangers of climate change. Process criticism does not concern the science, but it can affect the science.

Scientific criticism

Scientific criticism can broadly be broken down into two criticisms: that the report is too conservative or that it overstates the dangers of climate change. The view that the IPCC is too conservative means the IPCC did not go far enough and it understated the state of the science or the consequences of global warming. Conversely, those who view the IPCC as alarmist think that the IPCC overstated the state of the science and oversold the consequences of global warming. In addition, some scientists are concerned about potential biases of the report's lead authors, who have been shown to favor their own research.

AR4 understates the danger of climate change

Scientists at the National Snow and Ice Data Center (NSIDC) and the National Center for Atmospheric Research (NCAR) found that satellite and other observations show the Arctic ice cover is retreating more rapidly than estimated by any of the eighteen computer models used by the Intergovernmental Panel on Climate Change (IPCC) in preparing its 2007 assessments.

• Former U.S. Department of Energy member Joseph Romm has claimed that the report underestimates positive feedbacks that could lead to runaway climate change, thus greatly underestimating the future warming and its effects. The report is also said to be out of date because it omits recent observations such as the release of greenhouse gases, including methane, from thawing tundra.

• Arctic Sea ice is melting faster than predicted by climate models. Research conducted by the U.S.-based National Center for Atmospheric Research and the National Snow and Ice Data Center demonstrates that the 18 models on which the IPCC has based its current recommendations could already be out of date, and that the retreat of the ice could already be 30 years ahead of the IPCC's worst case scenario.

• The IPCC AR4 estimates explicitly exclude the influence of the melting of ice sheets. These ice sheets include most notably the Greenland ice sheet, and both the east and west Antarctic ice sheets, as well as numerous glaciers. This results in a major underestimate of the upper limit for sea level rise. Due to Arctic melting the Greenland ice sheet is particularly vulnerable, and "we cannot rule out large changes on decadal time-scales once wide-scale surface melt is underway.", the melting of the Greenland ice sheet would result in an increase in sea level rise of over 7m . Melting of the west Antarctic ice sheet would cause a similar, if slightly smaller rise in sea levels due to being grounded below sea level, whilst the affect of the melting of the east Antarctic, although less probable would be an order of magnitude greater.

AR4 overstates the dangers of climate change

• Shortly after publication of the AR4 Summary for Policymakers, The libertarian Fraser Institute issued an alternative "Independent Summary for Policymakers" (ISPM) drawing skeptical conclusions : There is no evidence provided by the IPCC in its Fourth Assessment Report that the uncertainty can be formally resolved from first principles, statistical hypothesis testing or modeling exercises. Consequently, there will remain an unavoidable element of uncertainty as to the extent that humans are contributing to future climate change, and indeed whether or not such change is a good or bad thing..

Process criticism

• Critics contend that the IPCC is an unusual organisation in that the evidence is supplied by scientists, but the summaries of its reports are agreed between scientists and representatives of governments.

• In January 2005, Dr. Chris Landsea who was already an author on the 2001 report (TAR), withdrew his participation in the Fourth Assessment Report claiming that the portion of the IPCC to which he contributed had become "politicized" and that the IPCC leadership simply dismissed his concerns. He published an open letter explaining why he was resigning and to "bring awareness to what I view as a problem in the IPCC process". The conflict centers around Dr. Kevin Trenberth's public contention that global warming was contributing to "recent hurricane activity", which Landsea described as a "misrepresentation of climate science while invoking the authority of the IPCC". He has stated that the process of producing the Fourth Assessment Report is "motivated by pre-conceived agendas" and "scientifically unsound". Landsea writes that "the IPCC leadership said that Dr. Trenberth was speaking as an individual even though he was introduced in the press conference as an IPCC lead author."

Further information: Politics of global warming

Further reading

• [http://www.inclusivedemocracy.org/journal/vol4/vol4_no4_trainer_critique_stern.htm "A critique of the Stern and IPCC analyses of CO2 mitigation: Consumer-capitalist society cannot solve the problem" Ted Trainer, The International Journal of Inclusive Democracy, vol 4, no 4, october 2008.