In Soviet gulags, guards used to use mosquitoes to torture prisoners. During a recent summer reporting trip to Siberia, a 60 Minutes team found out why.

“They’re everywhere,” producer Henry Schuster told 60 Minutes Overtime. “It’s incredibly, intensely uncomfortable.”

The 60 Minutes team was in Siberia to report on a new front in combating climate change. As correspondent Scott Pelley reports this week, a Russian geophysicist is warning that frozen soil, called permafrost, contains enough greenhouse gas itself to threaten the climate if it ever melts.

But it is melting, thanks to climate change. The warming temperatures are also causing more mosquitoes in Siberia and throughout the Arctic. Research shows warming above the Arctic Circle causes the pesky critters to emerge earlier, grow faster, and survive longer.