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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.
[edit] Scientific criticism
Scientific criticism can broadly be broken down into criticism that the report is too conservative or that it overstates the dangers of climate change. In this case, the view that the IPCC is conservative means the IPCC did not go far enough, 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 IPCC lead authors, who have been shown to favor their own research rather than opposing views.
[edit] AR4 is too conservative
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.
- Scientists, including former U.S. Department of Energy member Joseph Romm, have claimed that the report underestimates positive feedbacks that could lead to a runaway greenhouse effect, 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 The report is also said to be out of date because it omits recent observations such as the release of greenhouse gases, including methane, from thawing tundra.[1]
- The actual report gives a warning that positive feedbacks could release more carbon dioxide in a yet uncertain magnitude, but it does not mention gases with an even greater global warming potential like methane: "Climate-carbon cycle coupling is expected to add carbon dioxide to the atmosphere as the climate system warms, but the magnitude of this feedback is uncertain. This increases the uncertainty in the trajectory of carbon dioxide emissions required to achieve a particular stabilization level of atmospheric carbon dioxide concentration." [2]
[edit] 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 [4]: 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. RealClimate describes it as "profoundly ignorant" of IPCC processes, and contends that there were "so many bizarre statements in the Fraser Institute report that some of us think that spotting them could serve as a good final exam in an elementary course on climate change." [5].
- The American Association of Petroleum Geologists referred to AR4 as "wildly distorted and politicized."[6] However, organization members "have threatened to not renew their memberships if the AAPG does not alter its position on global climate change," according to president Lee T. Billingsley.[7]
[edit] 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.[8]
- 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"[9].
- 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".[9]
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
[edit] References
