Professor Dr. Hoesung Lee, Chair of the IPCC,
c/o World Meteorological Organization
7bis Avenue de la Paix C.P. 2300
CH -1211 Geneva 2, Switzerland.

The Hague, May 25, 2023

Dear Dr. Hoesung Lee,

With the recently published Synthesis Report, the IPCC finished its sixth assessment cycle, consisting of seven reports in total. An international team of scientists from the 1500-strong Climate Intelligence Foundation (Clintel) has assessed several claims from the Working Group 1 (The Physical Science Basis) and Working Group 2 (Impacts, Adaptation and Vulnerability) reports. Results have been summarized in Clintel’s report The Frozen Climate Views of the IPCC:

Thorough analysis by Clintel shows serious errors in latest IPCC report – Clintel

As background information, I wish to remind you of the 2010 InterAcademies Council (IAC) review of IPCC procedures, which was commissioned in the aftermath of disastrous publicity regarding errors in earlier IPCC reports and revelations of efforts by IPCC Lead Authors to stifle debate. The IAC concluded in part (emphasis added by me):

Given that the IAC report was prompted in part by the revelation of errors in the last assessment, the committee examined IPCC’s review process as well. It concluded that the process is thorough, but stronger enforcement of existing IPCC review procedures could minimize the number of errors. To that end, IPCC should encourage review editors to fully exercise their authority to ensure that all review comments are adequately considered. Review editors should also ensure that genuine controversies are reflected in the report and be satisfied that due consideration was given to properly documented alternative views. Lead authors should explicitly document that the full range of thoughtful scientific views has been considered.1

We regrettably conclude that the IPCC has failed to follow this advice and the AR6 exhibits the same flaws as before, namely biased selection of evidence, failure to reflect genuine controversies and failure to give due consideration to properly documented alternative views.

To give one example, the IPCC ignored crucial peer-reviewed literature, showing that normalised disaster losses have decreased since 1990 and that human mortality due to extreme weather has decreased by more than 95% since 1920. The IPCC’s authors asserted the opposite conclusions based on cherry-picked evidence, claiming increases in damage and mortality due to anthropogenic climate change, and the review process failed to correct this inaccuracy.

Clintel’s 180-page report, The Frozen Climate Views of the IPCC, is the first large scale international ‘assessment’ of the IPCC’s Sixth Assessment Report. In 13 chapters the Clintel report shows that IPCC makes numerous serious scientific errors that overall reflect a bias in favour of ‘bad news’ and against ‘good news’. This was the case throughout the report and especially in the preparation of the Summary for Policy Makers. The good news about disaster losses and climate related deaths was left out of the Summary for Policy Makers all together, for instance.

Additionally, where the IPCC AR6 has taken account of evidence that points away from a dismal, worst-case outlook, such as recognition that the RCP8.5, SSP5-8.5 and SSP3-7.0 emission scenarios are low likelihood and that models systematically overstate warming in the tropical troposphere, these findings are buried deep in the chapters and are not emphasized for the media or policy makers. Even worse, despite having concluded in its discussion of emission scenarios that the extreme ones are low likelihood, they are nevertheless given maximum prominence in other parts of the report for the purpose of projecting climate impacts.

Finally, we note that the IPCC has remained silent while the UN Secretary-General and other high-ranking officials repeatedly misrepresented the findings of the IPCC. For example, Secretary-General Guterres said of the Working Group 1 report2

“Today’s IPCC Working Group 1 report is a code red for humanity. The alarm bells are deafening, and the evidence is irrefutable: greenhouse‑gas emissions from fossil-fuel burning and deforestation are choking our planet and putting billions of people at immediate risk.”

The AR6 Working Group 1 report did not say these things, yet the IPCC never corrected him nor challenged any of the similarly inaccurate media coverage that distorts the contents of your report.

With all respect Dr. Lee, seriously misleading the world on such an important subject and on such a large scale is unacceptable for an UN organization that claims to be scientific. The errors and biases that Clintel has found in the AR6 report are worse than those that led to the 2010 IAC Review, indicating ongoing failure of the IPCC to live up to its mission.

The Clintel network therefore requests the following:

  • That the IPCC commissions a team with representation from Clintel and other independent persons not involved in IPCC Leadership to review whether the IPCC has fully implemented and followed the reforms recommended by the 2010 IAC Review, and whether more reforms are needed;
  • That the IPCC reviews prominent statements by major world leaders and media outlets paraphrasing the contents of the AR6 and correct the record where those
    statements are misleading or inaccurate;
  • That the IPCC meets with representatives from Clintel to receive input on the key deficiencies highlighted in our report that require a formal correction.

Looking forward to your response,
Yours sincerely,
Dr. A.J. (Guus) Berkhout, President of Clintel
Emeritus Professor of Geophysics
Member of the Royal Netherlands Academy of Arts and Sciences

P.S. The main objective of the Climate Intelligence Foundation (Clintel) is to generate knowledge and understanding of the causes and effects of climate change, as well as of the effects of climate policy. Clintel published the World Climate Declaration, which has now been signed by more than 1500 scientists and experts worldwide, thus rivalling in size and credentials the IPCC’s Working Group authorship lists. See