Over the past 50 years, anthropogenic climate change has shifted from an abstract possibility predicted by a few scientists to a reality everyone can see and feel. Global-mean surface temperatures have risen 1 °C, and the Arctic has warmed a staggering 3 °C.

The principal cause is rising atmospheric carbon dioxide from the burning of fossil fuels. Transitioning to a low-carbon economy in the next several decades will be necessary to avoid catastrophic climate change that could, for example, push outdoor temperature and humidity in the Persian Gulf region beyond what humans can endure.1 But even if societies succeed in bending carbon emissions downward, they will still need to adapt to climate changes that are already underway, including more severe heat waves, heavier rainstorms, and less summer irrigation water resulting from reductions in snowpack.

Adapting to that future requires accurate and actionable science. Although older and current climate models...

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