As with our planet as a whole, if you want to know the fate of polar bears in a warming world, you need to follow the energy.

For the planet, researchers have been doing just that by keeping track of how carbon dioxide and other greenhouse gases we emit into the atmosphere have been tipping the climate’s energy balance toward more and more warming. And the high north where polar bears live has warmed faster than any other region on Earth, resulting in shrinking sea ice and a cascade of ot