Growing up in Fairbanks, Alaska, Nathan Baring has seen the signs of a warming world all around him. The winters have begun to lose their infamous chill. Thawing permafrost is shifting the ground beneath his feet. And some years, there isn’t even enough snow to ski.

“If you have eyes and you walk out your back door, you can see the changes that have taken place over only my short childhood,” said Baring, 19, who already has six years of climate activism under his belt.