IPCC Criticism

The Intergovernmental Panel on Climate Change (IPCC) officially released its Fourth Assessment Report (AR4) in 2007. This document is often regarded as the definitive word on the science behind global warming. However, AR4 gives a distorted, misleading, biased and often erroneous picture. Examples of these distortions are listed here, with attention focused on the Working Group 1 Report "The Physical Science Basis" (WG1), and in particular its Summary for Policymakers (SPM). Curiously, the SPM was released in February 2007, several months before the main report. Confusingly, a "Synthesis Report" was issued in November 2007, with its own SPM. More background to the structure of the IPCC report is given here.

Errors, distortions and exaggerations in the WGI Report

  1. How the IPCC invented a new calculus. The IPCC authors invented a new way of measuring the slope of a graph, in order to create the false impression that global warming is accelerating.
  2. The table that didn't add up. The WG1 SPM was approved by the IPCC even though it contained a table with arithmetic errors. The table was quietly corrected with no admission of the error.
  3. False statement about Antarctic sea ice. The IPCC claims that there is no significant trend in Antarctic sea ice. In fact several papers (ignored by the IPCC) show a significant positive trend.
  4. Misleading claims about sea level rise.  AR4 gives the misleading impression that the rate of sea level rise is increasing, using the trick of switching from one measurement system (tide gauges) to another (satellites). 
  5. Incorrect calculation of an average.  An arithmetic error was made in the calculation of an average of a contribution to radiative forcing. Hence four diagrams in AR4 are wrong and misleading.
  6. False claims about Antarctic ice sheet. The IPCC claims that the Antarctic ice sheet is melting and that this is contributing to sea level rise, but recent research papers show that in fact the ice sheet is thickening.
  7. Dubious claims about Greenland ice sheet. The IPCC claims that the Greenland ice sheet is melting and causing sea level to rise - ignoring or misrepresenting research that shows the opposite.
  8. Erroneous claims about snow cover. The IPCC makes the false claim that snow cover is decreasing in both hemispheres.
  9. Exaggerated claims about water vapour. The IPCC summary claims that water vapour has increased. In fact studies show no significant trend or in some cases a decrease.
  10. Misleading claims on increased tropical cyclone activity. The IPCC states that tropical cyclones have increased, by cherry-picking start dates, but their own data shows no evidence of this.
  11. The IPCC contradicts itself over the medieval warm period. The IPCC's own data shows clear evidence that the medieval warm period was as warm as the late 20th century, but the text states the opposite.
  12. False statement about paleoclimate studies. The IPCC claims that there is increased confidence in proxy temperature reconstructions, but in fact the opposite is the case.
  13. Proxies that aren't proxies. The IPCC makes use of 'proxy' data such as tree rings to justify their claim that current temperatures are unusual - but this data doesn't match measured temperature.
  14. Downplaying the urban heat island effect. The IPCC significantly underestimates the influence of the fact that many temperature measurement sites are located in cities.
  15. The UN misquotes its own report. A UN press release coinciding with the release of AR4 blatantly misquoted the report, incorrectly claiming that man-made global warming was unequivocal.
  16. Underestimating past variation in carbon dioxide. The IPCC claims that past variation of carbon dioxide levels in the atmosphere was very low, ignoring published research that shows much greater variation.
  17. Biased reporting of the literature. One of many examples where the IPCC ignores or disparages research that does not support its agenda, in the area of past solar activity.
  18. Where's the beef? The crucial step of the argument for global warming - how carbon dioxide causes heating - is barely mentioned and the numbers  not justified by the IPCC.
  19. Hypothetical positive feedback. The alarming predictions of the IPCC rely on the assumption of a strong positive feedback, for which there is no evidence. 
  20. The lost continent of Antarctica. A world map of 'global warming' in the SPM omits Antarctica, where there has been no warming.
  21. Misleading claims about increased greenhouse effect.  The IPCC claims that observations show an increase in the greenhouse effect, referring to one paper but ignoring a more recent one that casts doubt on these results.
  22. Misleading statement about ocean heat. The IPCC SPM says that ocean heat content is increasing, without mentioning a paper that shows recent ocean cooling.
  23. Ignoring research that does not fit the agenda.  Work of a Finnish research team with 34 publications in the field of tree ring temperature reconstructions is completely ignored by the IPCC.
  24. Inconsistent statement about wind strength. The IPCC SPM claims that the strength of westerly winds has increased - but if true this would be evidence for cooling of the atmosphere.
  25. Error regarding total radiative forcing. The 'total net anthropogenic radiative forcing' given by the IPCC is incorrect, according to climate scientist Roger Pielke.
  26. Unfair citation of criticism. IPCC author Kevin Trenberth cites his own criticism of the work of other authors, but does not mention those authors' response to his criticism.
  27. Ignoring criticism of the surface temperature record.  Many papers have been written raising questions about the accuracy and bias of surface temperature measurements, but these are ignored by the IPCC.
  28. No explanation for mid-century cooling. The IPCC has no consistent or valid explanation for a period of cooling from 1940-1970.
  29. False statements about tropospheric warming. The IPCC claims that the troposphere (lower atmosphere) has warmed more than the surface, but the IPCC's own graphs show that this is not true.
  30. Unsubstantiated claims of human influence. The IPCC makes confident claims about man's influence on the climate but provides no evidence to support these claims.
  31. Misleading temperature trends (1). The IPCC claims that the trend from 1906-2005 is larger than that from 1901-2000 due to recent warm years, but in fact this is due to a sharp drop in temperatures from 1901-1906.
  32. Misleading temperature trends (2). The IPCC compares chalk with cheese in order to convey the false impression that temperature trends are increasing.
  33. False claim of warming since the TAR. The IPCC's claim that temperatures have increased since its 2001 Third Assessment Report is demonstrably false. 
  34. More false statements on temperature trends.  The IPCC significantly underestimates temperature trends in the early part of the 20th century.
  35. False claims about hurricanes. The IPCC makes unsustainable claims about increasing hurricane activity and a link with global warming, ignoring key papers that find no link; this lead to one expert resigning from the IPCC.
  36. If you don't like it, resign.  Some scientists who do not support the IPCC agenda find they have no alternative but to resign from the IPCC process.
  37. Reviewer comments ignored.  The IPCC reports undergo a process of review by scientists and goverments. But many valid comments and criticisms of the IPCC view are simply ignored.
  38. Exaggerated claims of increased precipitation.  The IPCC summary greatly exaggerates the claims from its main report about an alleged very slight increase in heavy rainfall events.
  39. Trying to suppress work that doesn't support the agenda.  IPCC authors try to keep a paper by McKitrick and Michaels out of AR4, "even if we have to redefine what the peer-review literature is".
  40. Hiding the decline - in the number of storms.   IPCC authors insert a line about increasing wind strength into the final version of the SPM. They discuss (by email) evidence for declining number of storms but decide not to mention this.
  41. Hiding inconvenient proxy data.  The IPCC refuses to show proxy ice core data showing a warm medieval period in the Southern Hemisphere, despite acknowledging a shortage of such data and despite reviewer comments.
  42. False confidence in man-made warming.  The IPCC SPM claims "very high confidence" regarding the quantification of man-made global warming, but the main body of the report is much more cautious. 
  43. Spinning the literature on cloud feedback.  IPCC authors regurgitate chunks of their own papers on clouds, but cut back sections that refer to negative cloud feedback.
  44. Cherry-picking solar irradiance reconstructions. The IPCC selects outdated estimates of past solar radiance (to try to 'explain' early 20th century warming) while ignoring more recent research that shows very little variation. 
  45. False confidence in long-term climate predictions.  The IPCC makes the ridiculous claim that predicting the climate 50 years ahead is much easier than predicting the weather a few weeks ahead. 
  46. Exaggerating climate sensitivity results from satellite data.  The IPCC distorts published research on the sensitivity of the climate to doubling of CO2, in such a way as to exaggerate the climate sensitivity.
  47. Underestimating uncertainty in aerosol forcing.  The uncertainty range in the value of aerosol forcing proposed by the IPCC is lower than that proposed by experts in the field. 
  48. Refusing to acknowledge an error. When the arithmetic error describe in point 5 was formally reported, the IPCC denied there was any error, falsely claiming that the text explained the reasoning adequately.

Errors, distortions and exaggerations in the WGII Report

  1. Incorrect claim about Himalayan glaciers.  The IPCC incorrectly said that Himalayan glaciers could melt to one fifth of their current area by 2035. This is probably a misreading of 2350.
  2. False claims about disaster losses.  The IPCC claims a link between disaster losses and climate, by relying on a single cherry-picked non-peer-reviewed paper. 
  3. Unsubstantiated claim about loss of Amazon rainforest.  Chapter 13 of WGII claimed that 40% of the Amazon rainforest could 'react drastically' to a change in climate. The source for this was a WWF report that does not even support the claim. See also BBC report and The Telegraph.
  4. Error about the Netherlands and sea level.  Chapter 12 of WGII claims that 55% of The Netherlands is below sea level. In fact  the figure is about 26%.  See also reports here and here
  5. Unsubstantiated claims about Africa.  A claim repeatedly made by the IPCC that agricultural yields in some African countries could fall by 50% as soon as 2020 has no basis. 
  6. False claims about wildfires and climate.  The IPCC claims that wildfires influence tourism, relying on newspaper reports and ignoring three expert reviewers who identify problems with this claim.

Errors, distortions and exaggerations in the WGIII Report

The report of Working Group III of the IPCC is concerned with "Mitigation of Climate Change".

Richard Tol, Professor of Economics, has investigated WGIII and reported his results at Roger Pielke Jr.'s blog. In his overall summary, he writes that the IPCC "substantially and knowingly misrepresents the state of the art in our understanding of the costs of emission reduction. It leads the reader to the conclusion that emission reduction is much cheaper and easier than it will be in real life."  He also writes that "all errors point in one direction: alarmism about climate change", and  refers to the "inability of the IPCC to constructively engage with valid criticism". His specific criticisms are as follows:

Part I. Claims by the IPCC in WGIII chapter 11 that climate policy would stimulate growth and create jobs are biased and not based on peer-reviewed literature.

Part II. Again in Chapter 11, the IPCC highlights work that supports the view that costs of emission reduction are low, while ignoring or misquoting studies that find such costs are high.

Part III. In the Summary for Policymakers (SPM) in WGIII, the IPCC underestimates the costs of emissions reduction,  failing to correct its estimates for selection bias.

Part IV. In Chapter 3, the IPCC misrepresents a paper (Fisher et al 2006), ignoring complaints about this by reviewers.

Part V. In Chapter 3 and in the SPM, the IPCC incorrectly claims that exchange rates are immaterial, and misrepresents the literature.  Several reviewer comments on this are ignored.

Part VI. In the SPM, Table SPM1 underestimates the cost of reducing emissions, by a misleading process of "double counting". The errors were pointed out by reviewers, but ignored by the IPCC.

See also Tol's Guest Post at the Klimazwiebel blog, where he ends by saying that tables in the WGIII SPM are misleading and cherry-picked.

Acknowledgements: These examples come from many different sources.  Many of them arise simply from a careful reading of AR4. Many originated from a thread at climate audit (which no longer exists) so thanks are due to those who contributed to that - especially Max. Several examples come from Roger Pielke's Climate Science blog.

A note on timings: Most of the items on WGI were written in the second half of 2008. The WGII and WGIII articles were written in early 2010, when the mainstream media started to note these errors.

Comments, questions and further examples of IPCC bias and distortion can be sent to  globwarmqs at googlemail.com

IPCC-related links