Extra

The Greenland ice sheet is the second largest body of frozen water in the world, with the potential to raise sea levels by 23 feet if it melts. 

In this Threshold extra, we’re talking with leading climate scientists and glaciologists about the cryosphere—all the things that are frozen in the Earth’s system: permafrost, sea ice, land ice, and snow. We take a close look at how two of its key elements have fared in 2020: the Greenland ice sheet and Arctic sea ice.