Statement by CLINTEL and ICSF on Release of the IPCC Sixth Assessment Report (AR6)

August 9, 2021
Recognition at last for scientists challenging climate alarmism

Climate scientists from IPCC‐circles have admitted that their new generation of climate models – referred to as CMIP6‐models – are ‘overheated’ and therefore too alarmist. This groundbreaking concession was made the week before the highly‐anticipated release of the Sixth Assessment Report (AR6) ‐ the flagship 6‐year product of UN’s climate agency, IPCC.

The concession also raises questions on the reliability of temperature forecasts of IPCC’s previous generation of models (CMIP5), which used the extremely high RCP8.5 emissions scenario. Results were often falsely touted as a business‐as‐usual case and used to promote extreme climate action.

Observations had already indicated that CMIP5‐models were too sensitive to greenhouse gas increases, probably by a factor of two. The combination of too high climate sensitivity and too high emissions projections resulted in implausible high temperature forecasts. As the new generation models (CMIP6) appear to run even warmer, they will make the new equivalent of RCP8.5 in AR6 ludicrously high. It explains the uncomfortable feelings in IPCC‐circles that these projections may be science fiction.

The good news for society is that IPCC‐scientists themselves are beginning to doubt whether their models can be trusted as a policy instrument. “It’s become clear over the last year or so that we can’t avoid this admission”, Gavin Schmidt ‐ director of NASA’s Goddard Institute for Space Studies ‐ told the renowned journal Science. Schmidt also said: “You end up with numbers for even the near‐ term that are insanely scary—and wrong.

This unexpected announcement by the NASA director is widely seen as a first step in the rehabilitation of realist scientists. These scientists have been vilified for years for revealing facts, theoretically and empirically, that the IPCC models tell a political story and pay scant attention to the natural cycles in the earth’s climate. They have also stated that while climate models are very useful to study the Earth’s complex climate system, they are inadequate to make reliable projections on which to base climate policy. In recent years, CLINTEL has sent registered letters to world leaders, warning them that real observations and model projections increasingly contradict each other, resulting in inappropriate climate policies.

American climate scientist, Judith Curry, reacted as follows: “The elephant in the room for the IPCC is that they are heavily relying on the RCP8.5 scenario in their climate recommendations, which are now widely regarded as implausible.” Michael Asten, an expert reviewer of the AR6 report, sees the admission that IPCC climate models are running inconceivably hot is a significant concession.

CLINTEL and ICSF have consistently argued that, while the climate is changing, partly due to anthropogenic influences, there is no climate crisis, and that at some point that key truth would come out. That moment of truth has now come, and climate policy needs to change accordingly.

Guus Berkhout is President of CLINTEL (, Jim O’Brien is Chair of the ICSF (

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