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Intergovernmental Panel on Climate Change
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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.

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. The converse view is the IPCC conclusions are alarmist, and that the IPCC overstated the state of the science and oversold the consequences of global warming.

AR4 understates the danger of climate change

Ice sheets and sea level rise

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Data Center demonstrates that the 18 models on which the IPCC has based its current recommendations could already be out of date, and that the retreat of the ice could already be 30 years ahead of the IPCC's worst case scenario.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 effect of the melting of the east Antarctic, although less probable would be an order of magnitude greater.

In a lecture he gave at the University of California, Santa Barbara, climate scientist James E. Hansen criticised the IPCC for its description of future sea level rise. Hansen has also written on this issue:

The IPCC (2007) midrange projection for sea level rise this century is 20–43 cm (8–17 inches) and its full range is 18– 59 cm (7–23 inches). The IPCC notes that they are unable to evaluate possible dynamical responses of the ice sheets, and thus do not include any possible ‘rapid dynamical changes in ice flow’. Yet the provision of such specific numbers for sea level rise encourages a predictable public response that the projected sea level change is moderate, and smaller than in IPCC (2001). Indeed, there have been numerous media reports of ‘reduced’ sea level rise predictions, and commentators have denigrated suggestions that business-as-usual greenhouse gas emissions may cause a sea level rise of the order of meters

The IPCC is doing a commendable job, but we need something more. Given the reticence that the IPCC necessarily exhibits, there need to be supplementary mechanisms. The onus, it seems to me, falls on us scientists as a community.

In a lecture given at Princeton University, IPCC author Michael Oppenheimer admitted that the IPCC report could have better explained the contribution of melting ice sheets in predictions of sea level rise. Oppenheimer said that the IPCC Working Group II Summary of Policymakers (quoted below) managed this better than the Working Group I Summary of Policymakers:

There is medium confidence that at least partial deglaciation of the Greenland ice sheet, and possibly the West Antarctic ice sheet, would occur over a period of time ranging from centuries to millennia for a global average temperature increase of 1-4°C (relative to 1990-2000), causing a contribution to sea-level rise of 4-6 m or more.

Projected date of melting of Himalayan glaciers; use of 2035 in place of 2350

A paragraph in the 938-page 2007 Working Group II report (WGII) included a projection that Himalayan glaciers could disappear by 2035. This projection was not included in the final summary for policymakers which highlighted the importance of the glaciers for freshwater availability, and stated that "Widespread mass losses from glaciers and reductions in snow cover over recent decades are projected to accelerate throughout the 21st century". Late in 2009, in the approach to the Copenhagen climate summit, the 2035 date was strongly questioned in India. On 19 January 2010 the IPCC acknowledged that the date was incorrect, while reaffirming that the conclusion in the final summary was robust. They expressed regret for "the poor application of well-established IPCC procedures in this instance" and their vice-chairman Jean-Pascal van Ypersele said that the reviewing procedures would have to be tightened.

The WGII report ("Impacts, Adaptation and Vulnerability"), chapter 10, page 493 says:

Glaciers in the Himalaya are receding faster than in any other part of the world (see Table 10.9) and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate. Its total area will likely shrink from the present 500,000 to 100,000 km2 by the year 2035 (WWF, 2005).

(emphasis added). The WWF report referred to is "WWF (WorldWildlife Fund), 2005: An overview of glaciers, glacier retreat, and subsequent impacts in Nepal, India and China. World Wildlife Fund, Nepal Programme, 79 pp" . The date of 2035 has been correctly quoted by the IPCC from the WWF report, which says:

In 1999, a report by the Working Group on Himalayan Glaciology (WGHG) of the International Commission for Snow and Ice (ICSI) stated: “glaciers in the Himalayas are receding faster than in any other part of the world and, if the present rate continues, the livelihood of them disappearing by the year 2035 is very high”.

It has been suggested that this report should not have been used , as it does not appear to be peer-reviewed . However, IPCC rules permit the use of non-peer-reviewed material, providing it is "internationally available".

The WWF report appears to be relying on "Variations of Snow and Ice in the past and at present on a Global and Regional Scale" . The exact quote used above does not appear in this report (though the same quote, with the same mistake of "livelihood", appears elsewhere , so it seems likely that the WWF has relied on press reports about the ICSI report. The ICSI report itself states:

The degradation of the extrapolar glaciation of the Earth will be apparent in rising ocean level already by the year 2050, and there will be a drastic rise of the ocean thereafter caused by the deglaciation-derived runoff (see Table 11 ). This period will last from 200 to 300 years. The extrapolar glaciation of the Earth will be decaying at rapid, catastrophic rates—its total area will shrink from 500,000 to 100,000 km² by the year 2350. Glaciers will survive only in the mountains of inner Alaska, on some Arctic archipelagos, within Patagonian ice sheets, in the Karakoram Mountains, in the Himalayas, in some regions of Tibet and on the highest mountain peaks in the temperature latitudes

Thus, the IPCC has erroneously used a date of 2035 instead of 2350. However, IPCC itself correctly quoted its own source, the WWF report. There is no clear reason why the IPCC used the WWF report rather than the original ICSI source. The ICSI source itself, whilst it does provide a 2350 date, does not provide a good scientific justification for that date.

The IPCC acknowledged the error in the date of Himalayan glacier melt but also stated that it does not change the broad picture of man-made climate change.

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."

Uncertainty

The 2007 IPCC Working Group I Report quantified the effect of anthropogenic aerosols on the climate in terms of their radiative forcing. Radiative forcing measures the influence a particular factor has on changing the Earth-atmosphere-system energy balance. The effect of aerosols was assessed to be the dominant uncertainty in radiative forcing.

A 2008 Report for the US Climate Change Science Program (CCSP) suggested that the IPCC report may have been 'overconfident' with its uncertainty estimate for the total aerosol forcing. This was based on an earlier 2006 paper that elicitated the judgement of twenty-four experts on aerosol forcing. The CCSP Report went on to say:

expert judgment is not a substitute for definitive scientific research. Nor is it a substitute for careful deliberative expert reviews of the literature of the sort undertaken by the IPCC. However, its use within such review processes could enable a better expression of the diversity of expert judgment and allow more formal expression of expert judgments, which are not adequately reflected, in the existing literature. It can also provide insights for policy makers and research planners while research to produce more definitive results is ongoing. It is for these reasons that Moss and Schneider have argued that such elicitations should become a standard input to the IPCC assessment process

Policy advice

In 2007, economist and former IPCC author Richard Tol wrote a paper on the IPCC Working Group III Report. Tol said that the quality of the Working Group III Report had declined. He made several criticisms of the Report's content, and suggested changes in procedure that could improve the quality of future IPCC assessments:

It would be much better to shift the IPCC from UNEP and the environment ministries to ICSU and the ministries of research and higher education. Academic quality should be guiding principle in selecting authors. As a check, the committees that nominate and select authors should publish their proceedings. The review editors should become more independent, and gain the right to reject chapters that are not properly revised. The alternative is a gradual erosion of the quality, prestige and, eventually, influence of the IPCC.

References

1. CNN "Arctic melt worse than predictions"
2. This contrasts with the IPCC AR3, which included earlier estimates of these ice dynamics, and had a higher top end sea level rise estimate, although much lower than some new estimates. The report states that recent observations suggest that ice flow dynamics could lead to additional rise: "Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude."
3. Climate change and trace gases. By James Hansen, Makiko Sato, et.al. Phil.Trans.R.Soc.A (2007)365,1925–1954, doi:10.1098/rsta.2007.2052. Published online 18 May 2007,
4. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) . Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 881pp. ,, and .
5. Hansen, J.E. (26 March 2007). "How Can We Avoid Dangerous Human-Made Climate Change". UCTV – University of California Television. Retrieved 2009-05-20.
6. Hansen, J.E. (2007). "Scientific reticence and sea level rise". Environ. Res. Lett. doi:10.1088/1748-9326/2/2/024002. Retrieved 2009-05-20. {{cite journal}}: Check |doi= value (help); Unknown parameter |doi_brokendate= ignored (|doi-broken-date= suggested) (help)
7. Oppenheimer, M. (1 April 2008). "Ice Sheets and Sea Level Rise: How Should IPCC Handle Deep Uncertainty?". Princeton University, Woodrow Wilson School of Public and International Affairs. Retrieved 2009-05-20.
8. M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds. (2007). "IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change" (PDF). Cambridge University Press. Retrieved 2009-05-20.{{cite web}}: CS1 maint: multiple names: authors list (link)
9. Mukherjee, Krittivas and Alister Doyle (Agence France-Presse), "U.N. panel re-examines Himalayan glacier thaw report", NewsDaily, January 18, 2010.
10. Richard Black (19 January 2010). "UN climate body admits 'mistake' on Himalayan glaciers". BBC News. Retrieved 2010-01-23.
11. "IPCC statement on the melting of Himalayan glaciers" (PDF). 20 January 2010. Retrieved 2010-01-23.
12. Cruz, R.V., H. Harasawa, M. Lal, S. Wu, Y. Anokhin, B. Punsalmaa, Y. Honda, M. Jafari, C. Li and N. Huu Ninh (2007), "10 Asia", Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (PDF), Cambridge University Press, pp. 469–506 {{citation}}: line feed character in |title= at position 8 (help)CS1 maint: multiple names: authors list (link)
13. http://www.timesonline.co.uk/tol/news/environment/article6991177.ece
14. Mukherjee, Krittivas and Alister Doyle (Agence France-Presse), "U.N. panel re-examines Himalayan glacier thaw report", NewsDaily, January 18, 2010.
15. BBC news UN mistake
16. BBC "Stark picture of a warming world"
17. Prometheus: Chris Landsea Leaves IPCC Archives
18. Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.) (2007). "IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change". Cambridge University Press. Retrieved 2009-12-07. {{cite web}}: |author= has generic name (help)CS1 maint: multiple names: authors list (link)
19. Granger Morgan, H. Dowlatabadi, M. Henrion, D. Keith, R. Lempert, S. McBrid, M. Small, T. Wilbanks (eds.) (2009). "Best practice approaches for characterizing, communicating, and incorporating scientific uncertainty in decisionmaking. Final Report, Synthesis and Assessment Product 5.2". US Climate Change Science Program website. Retrieved 2009-12-07. {{cite web}}: |author= has generic name (help)CS1 maint: multiple names: authors list (link)
20. Tol, R.S.J. (2007). "Biased Policy Advice from the Intergovernmental Panel on Climate Change". Energy & Environment. 18 (7+8): 929–936. Retrieved 2009-05-20.

Further reading

• "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.

• Criticisms