In one of the planet's coldest places, 130 kilometers south of Russia's Arctic coast, scientist Sergey Zimov can find no sign of permafrost as global warming permeates Siberia's soil.
As everything from mammoth bones to ancient vegetation frozen inside it for millennia thaws and decomposes, it now threatens to release vast amounts of greenhouse gases.
Zimov, who has studied permafrost from his scientific base in the diamond-producing Yakutia region for decades, is seeing the effects of climate change in real time.