Criticism of IPCC AR4

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, 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 The report is also said to be out of date because it omits recent observations such as the release of greenhouse gases, including methane, from thawing tundra. [For example, see Joseph Romm's December 2006 book, "", pp. 65-72, and [http://climateprogress.org/2007/02/01/climate-progress-on-fox-news/ his interview] on Fox News on January 31 2007.] :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." [ [http://users.telenet.be/j.janssens/CommentsSPM4web.pdf WG1 SPM, page 17] ]

*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. [ [http://www.cnn.com/2007/TECH/science/05/02/arctic.ice CNN "Arctic melt worse than predictions"] ]

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 [ [http://www.fraserinstitute.org/Commerce.Web/product_files/Independent%20Summary5.pdf] Independent Summary for Policymakers] : "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." [ [http://www.realclimate.org/index.php/archives/2007/02/fraser-institute-fires-off-a-damp-squib/ Fraser Institute fires off a damp squib] ] .

*The American Association of Petroleum Geologists referred to AR4 as "wildly distorted and politicized." [ [http://www.google.com/search?q=cache:DN5c3SUxEWsJ:dpa.aapg.org/correlator/2007/spring/myths.cfm+wildly+distorted+and+politicized+site:aapg.org&hl=en&ct=clnk&cd=1&gl=us 403 Forbidden ] ] 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. [ [http://www.aapg.org/explorer/president/2007/03mar.cfm AAPG Explorer President's Column] ]

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. [ [http://news.bbc.co.uk/2/hi/science/nature/6524325.stm BBC "Stark picture of a warming world"] ]

*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" [http://sciencepolicy.colorado.edu/prometheus/archives/science_policy_general/000318chris_landsea_leaves.html Prometheus: Chris Landsea Leaves IPCC Archives ] ] . 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."

*Critics contend that the degree of review of AR4 and the consensus it represents have been exaggerated or misunderstood, though not necessarily by the IPCC itself. For example, AR4 is based on a review of the outside work of over 2,500 scientists, but AR4 is sometimes wrongly described as being reviewed or approvedby over 2,500 scientists. [http://conservationvalue.blogspot.com/2007/01/new-ipcc-report-2500-scientists-say.html Conservation Value Notes, accessed September 29, 2008] One such source was the Union of Concerned Scientists inaccurately said that "an additional 2,500 experts reviewed the draft documents." [http://www.ucsusa.org/global_warming/science_and_impacts/science/ipcc-backgrounder.html The IPCC: Who Are They and Why Do Their Climate Reports Matter?, accessed September 29, 2008] David Suzuki, perhaps the most prominent environmentalist in Canada made a similar, wrong statement when he said, "2,500 scientists signed the IPCC (Inter-Governmental Panel on Climate Change) Report". [http://www.canadianvalues.ca/issues.aspx?aid=267 Institute for Canadian Values, "Global Warming Charlatan", accessed September 29, 2008] Tom Harris and John McLean have pointed out that only 62 scientists actually reviewed the critical chapter 9 which includes the conclusion that human activity is the driving force of global warming, [http://www.newsletter.co.uk/3425/OPINION-True-nature-of-climate.4488683.jp The News Letter, "True Nature of Climate Change Highly Uncertain", Sept. 13, 2008] [http://letters.salon.com/25eabdb0b33361da6439ca9a109ed3e9/author/ Salon, "UN scientists really don't believe what we are told they believe". August 18, 2007] An examination of the IPCC's "Comments on the Second Order Draft". [http://hcl.harvard.edu/collections/ipcc/ Working Group I Fourth Assessment Report, Review Comments and Responses] reveals that there were indeed comments by only 62 reviewers of the second order draft, though we cannot know how many scientists reviewed the chapter but accepted its conclusions by default by making no comments. While the IPCC has not made known the number of reviewers of chapter 9, it is certainly considerably closer to 62 than to 2,500.

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