Fires, intensified by climate change, release carbon trapped in soil and plants. More frequent infernos have now transformed the tundra into a net source of carbon dioxide emissions. It’s a dramatic shift for the Arctic, and one that will make the planet even hotter.

For millennia, Arctic ecosystems have stored more carbon dioxide than they release, but that has shifted as warming temperatures have boosted wildfires and melted permafrost in the north

The Arctic tundra has historically helped reduce global emissions. But rising temperatures and wildfires in the region are changing that, scientists say.