Scientists think the amount of methane emitted to the atmosphere from freshwater ecosystems will increase as the climate warms, reports Tim Radford. And that will trigger further warming.

This highlights another mechanism by which the global carbon cycle may serve to accelerate rather than mitigate future climate change.
British scientists have identified yet another twist to the threat of global warming. Any further rises in temperature are likely to accelerate the release of methane from rivers, lakes, deltas, bogs, swamps, marshlands and rice paddy fields.