Extinction risks in a rapidly warming planet depend on previous slow temperature swings

Considering "climate memory" changes the risk calculation as much as an organism's geographic range or abundance

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Rising global temperatures are one of the biggest threats to biodiversity. The slow creep up of the thermometer — 1.2 degrees Celsius over the past 150 years — is blisteringly fast on a geological timescale, and species can only adapt so fast. But they’ve evolved to deal with changing temperatures in the past — sometimes, very far in the past. Scientists writing in Nature earlier this year found that considering this “memory” of climate history helps better predict extinction risks as the planet continues to heat up.

The researchers tracked thousands of animal extinctions through the fossil record and compared their frequencies under different prehistoric combinations of long- and short-term temperature changes. If a rapid change in temperature was preceded by a slower temperature change in the opposite direction, the rapid change was usually less deadly. They presume this occurs because the second change returns to distant-past temperatures for which species remained fit, after timescales as long as 60 million years. On the other hand, rapid temperature changes in the same direction as a previous slower change were especially risky.

The effect of prior long-term temperature is strong enough to seriously impact predictions of extinction risk for any given group of species. According to their results, it changes the risk calculation as much as its geographic range or abundance. And, while even the “short-term” prehistoric extinctions happened over timescales far slower than today’s maelstrom of extinction, long-term temperature effects provide a bit of hope: The rapid warming of the Anthropocene was preceded by a long global cooling period, which could make climate change a little less deadly.