Scientists say levels have been stable for about seven years following a steep rise during the last century.

Methane is the second most important gas contributing to the human-made greenhouse effect after carbon dioxide. Current concentrations are about 150% above pre-industrial levels.

But because methane is broken down relatively easily, atmospheric concentrations would return to pre-industrial levels within about a decade if the various sources of production linked to human activities could be eliminated.

So some good news in the world of global warming. Although carbon dioxide levels are still way too high, some of the damage that global warming is going to cause may be less severe with lower levels of methane in the atmosphere.