Evidence from Siberian caves suggests that a global temperature rise of 1.5C could see permafrost thaw over a large area of Siberia.
A study shows that more than a trillion tonnes of the greenhouse gases CO2 and methane could be released into the atmosphere as a result.
An international team has published details in the journal Science.
The evidence comes from analysis of stalactites and stalagmites in caves along the "permafrost frontier".
Speleothems Reveal 500,000-Year History of Siberian Permafrost - published Thursday 21st February. http://www.sciencemag.org/content/ea...cience.1228729