To learn how Earth’s species go extinct, scientists have often focused on what’s readily available from the fossil record—organisms’ intrinsic traits, such as their body size or the geographic range they occupy. Yet some of the largest mass extinctions in the geologic past have also been connected to a different factor: extrinsic climate change. The sparse fossil record makes it difficult to estimate the climate contributions to extinction for specific times and places. Most studies, therefore, have treated intrinsic and extrinsic factors separately.

A 2021 climate study, for example, looked only at temperature over the past 450 million years, when animals and plants became abundant on Earth. It found that a historical increase of 5 °C reduced global biodiversity (see figure 1) by about 75%.1 That’s similar in magnitude to the five largest extinctions.

Now Cooper Malanoski and Erin Saupe of the University of Oxford and their colleagues...

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