Arctic tundra is now a source – not a sink – of carbon emissions

The Arctic tundra now emits more carbon dioxide and other greenhouse gases than it absorbs. Rising temperatures due to climate change have shifted the ecosystem’s effect on the planet – it has moved from helping to cool Earth to having a warming effect.

“It’s a really serious change,” says Twila Moon at the National Snow and Ice Data Center in Colorado. “Human-caused warming is now causing warming from nature. It is irreversible on a thousands-of-years timescale.”…