Icy Siberian caves show tiny warming, may mean big thaw

OSLO (REUTERS) - Ancient records from icy caves in Siberia show that a small amount of global warming can thaw vast areas of frozen ground and release harmful stores of greenhouse gases, a study showed.

Any melt of permafrost, or permanently frozen soil that covers almost a quarter of the northern hemisphere from Alaska to China, can also destabilise everything from oil and gas pipelines to buildings and roads.

"Global climates only slightly warmer than today are sufficient to thaw significant regions of permafrost," experts in Britain, Russia, Switzerland and Mongolia wrote in Friday's edition of the journal Science after studying Siberian caves.

A global rise of 1.5 deg C above late 19th century temperatures - less than a 2.0 deg C ceiling for global warming set in 2009 by almost 200 nations - could bring a substantial thaw as far north as 60 degrees latitude, they said.