Posted on 23 September 2025 by Sue Bin Park

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Has the IPCC overestimated climate change impacts?

The Intergovernmental Panel on Climate Change compiles the consensus of thousands of models, and many independent lines of research suggest its estimates were more conservative than what was subsequently observed.

For example, sea-level rise predictions in earlier IPCC reports were later found to be too low compared to recently observed melting of ice sheets and thermal expansion. Studies show IPCC’s mid-range forecasts have been highly accurate, but reports often understate high-end risks.

IPCC reports must be approved by nearly 200 governments and only include findings supported by multiple lines of evidence. That tends to filter out less certain, but still possible, worst-case scenarios.

However, IPCC’s latest 2021 report now states it is virtually certain that human CO2 emissions have been the main driver of warming since the mid-20th century. Given their historically cautious approach, its recent warnings carry even more weight.

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This fact brief is responsive to quotes such as this one.

Sources

American Geophysical Union Evaluating IPCC Projections of Global Sea-Level Change From the Pre-Satellite Era

IPCC AR6 Summary for Policymakers.

IPCC AR6 Longer Report

Climate Central Report: IPCC Underesimates Climate Risks

Live Science 4 Things to Know About the IPCC's Climate Change Report

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Fact briefs are short, credibly sourced summaries that offer "yes/no" answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact — a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all of our published fact briefs here.