Russia's permafrost is thawing - and it could make melting polar ice caps look like a sideshow | Climate News | Sky News
It's 30C (86F) when our small propeller plane touches down in the Arctic town of Chersky in the far northeastern tip of Russia.
"My name is Zimov. You know what that means? In Russian it means I'm a winter person. This is climate change for you, I can't stand this heat!"
Their focus is permafrost and the risk it represents as our planet warms. Sergei Zimov has warned of the dangers of thawing permafrost since the 1990s.
"Now it is much easier for me to argue with other scientists because I said for years that the permafrost would melt and now it's happening," Mr Zimov says.
Permafrost is the layer of permanently frozen soil which stretches beneath 65% of the Russian landmass and nearly a quarter of the northern hemisphere.
Except that it is thawing and, as it does, the more than 1,400 gigatonnes of carbon trapped inside (one gigatonne is one billion tonnes) is starting to escape in the form of greenhouse gases, carbon dioxide and methane.
It is a vicious feedback loop which, in a worst-case scenario, could make even the melting of the polar ice caps look like a side-show.
