Large parts of the Northern hemisphere from Alaska to China hold a dangerous treasure. 24 percent of this land’s ground is frozen throughout the year – so called permafrost. It holds more than 1,000 gigatons of the most dangerous greenhouse gases: carbon dioxide and methane. Release of those would accelerate climate change to great extend.

Now, researchers found evidence that permafrost could start melting already at a 1.5 degrees Celsius rise in temperature. Also, the world already warmed up by 0.6 to 0.7 degree Celsius compared to the preindustrial level. So adding another 0.8 could already let permafrost melt.

That’s at least what happened in former times, as the scientists from Britain, Russia, Mongolia and Switzerland found out. They went into Siberian caves located along the ‘permafrost frontier’ studying stalactites and stalagmites as they function as a kind of climate archive – they only grow when liquid rainwater and snow melt drips from the surface into the caves.

“The stalactites and stalagmites from these caves are a way of looking back in time to see how warm periods similar to our modern climate affect how far permafrost extends across Siberia”, said Dr Anton Vaks of Oxford University’s Department of Earth Sciences, who led the work.

The amplifying effect on global warming the release of greenhouse gases held in the permafrost would have, exceeds everything climate models yet suggest. So, though almost 200 nations agreed in 2009 to the 2 degree target for global warming, this may not be enough to keep permafrost from melting and thus to mitigate climate change.