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.