Leaking Siberian ice raises a tricky climate issue

As the air warms, the tops of the wedges melt and create depressions in the land. Water either forms a lake or runs off to lower ground, creating a series of steep hillocks and gullies. During summer, lakeside soil may erode and tumble into the water, settling on the bottom where bacteria eat it and cough up yet more methane.

The process takes a long time, but Zimov has done a simulation by bulldozing trees and scraping off moss and surface soil from 1 hectare (2.5 acres) of former larch forest, rendering it as if it had been leveled by fire.

Seven years later the previously flat terrain is carved up with crevices 10 to 15 feet (3 to 5 meters) deep, creating a snowy badlands.

Gazing across a white river to the apartment blocks on a distant hill, Zimov said, "In another 30 years all of Chersky will look like this."