Very Chilly boffins working in the Arctic have come across evidence that the huge quanties of methane below the seabed are showing signs of destabilising.
According to the journal Science, the boffins have discovered that methane is leaking from the sub-sea permafrost far faster than had been previously estimated.
As a greenhouse gas, methane is 25 times more powerful than carbon dioxide but emissions from subsea permafrost are not included in climate change prediction models.
Natalia Shakhova, of the University of Alaska, told The Times the sub-sea permafrost should act as a cap or seal, preventing leakage.
Methane levels have doubled since the beginning of the Industrial Revolution but 40 per cent of sources are natural.
The rise of methane has caused the Arctic to warm at about twice the rate of the rest of the planet. The boffins are worried that as rising temperatures melt more permafrost, the added methane will raise temperatures further and so cause a wider thaw.
Dr Shakhova said the methane has not been included in climate models and the teams are trying to work out why this is happening. The fear is that that the sub-sea permafrost has been showing signs of destabilisation.