By Agence France-Presse
Wednesday, June 19, 2013
Areas of permafrost could start to thaw within decades, freeing long-stored greenhouse gases to the atmosphere, according to a study released on Wednesday that measured ancient stalagmites in a Siberian cave.
Continuous permafrost — land that is frozen all year round — starts to thaw when temperatures rise around 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels, its authors said.
Earth has already warmed by around 0.8 C (1.4 F) since the start of the Industrial Revolution in the mid-18th century, and on current trends, the threshold could be reached “within 10-30 years,” they said.
“An urgent global effort (in) reducing emissions of greenhouse gases is required,” they warned.
A team led by Gideon Henderson at Oxford University’s Department of Earth Sciences looked at speleothems — stalagmites and stalactites — at Ledyanaya Lenskya cave near Lensk, eastern Siberia.
Speleothems grow when water from the surface seeps through the roof of the cave.
Caves themselves are usually at about the same temperature as the mean average air temperature at the surface.