IPCC Caught Amplifying Its Own Alarmism, And The Media Made It Worse

Researchers examined the the IPCC’s own assessment reports, and thousands of media articles. They concluded that the IPCC policymaker summaries essentially put thumbs on the severity scale of projected future warming, stressing the more alarmist possibilities (in their view) of adding extra molecules of carbon dioxide to the atmosphere. One weakness of doing that being the lack of certainty that slight atmospheric composition changes alone (or at all) ‘force’ anything to happen to the long term temperature of the Earth, when other factors may have an equivalent effect, as historical climate data shows. Any tendency to detach the summaries from the original data is obviously likely to give policymakers a misleading impression of the Earth’s climate situation. However the author says ‘the dynamics at play here require no misconduct or even intent’. [See links for more].
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A potentially very significant new preprint by Galiani et al. documents how the IPCC (Intergovernmental Panel on Climate Change) and the media introduce bias into assessment and reporting on climate change — a bias toward more extreme claims, says Roger Pielke Jr. @ Climate Dispatch.

The paper is a preprint, and its data files are not yet available, so the findings should be considered preliminary.

Specifically, the paper claims that the IPCC Summary for Policymakers (SPM) is biased toward making claims more extreme than the underlying science represented elsewhere in the IPCC reports.

Critics of the IPCC have often made this assertion, but this is the first analysis that I am aware of that seeks to systematically evaluate the claim with data.

Today’s post shares my interpretation of the new analysis.

What Galiani et al. Did
Scientific findings of the IPCC — especially those projecting climate futures — can be thought of as the result of a linear process, shown in the figure below.

The process begins with the selection and prioritization of scenarios used in projective climate research. Researchers then apply those scenarios in further modeling, ultimately publishing results in the peer-reviewed literature.
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What Galiani et al. Found
Galiani et al. scored ~114,000 matched claim pairs drawn from all six IPCC Assessment Reports (1990–2023) and 116,000 newspaper articles from ten major US and UK outlets, using three independent large language models — GPT-5-mini, Claude Haiku 4.5, and Gemini 2.5 Flash — to evaluate each pair on the three dimensions: severity shift, uncertainty compression, and scenario salience.

The headline result is unambiguous: at every measured stage, in every Assessment Report, claims shift systematically toward the more severe end of the scientific ranges presented by the IPCC in its Technical Summary.

The dominant effect is severity shift — the tendency to emphasize the upper end of reported quantitative ranges while backgrounding or ignoring the lower end.
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The fact that the media has a bias toward amplifying climate science will come as a surprise to absolutely nobody. However, the finding that the IPCC SPMs also reflect the same bias is a very significant finding.
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Why Galiani et al. Matters
Galiani et al. offer the first evidence that the IPCC process amplifies climate science [toward] more extreme conclusions, beyond those reported in the Technical Summaries, and by extension, beyond what’s found in the peer-reviewed literature.

Because Galiani et al. look at only a subset of the climate science communication chain, their results should be interpreted as just a floor of possible amplification bias.

As I’ve documented at THB at length, the overreliance on extreme climate scenarios in research and policy represents an enormous source of bias, beyond that documented in this new preprint.

Full article here.