Weatherwatch

Springtime creates a big stink around the Arctic. Bubbling away under the ice of Siberia and Alaska is methane, the smelly gas best known in marshlands. It is also a greenhouse gas 20 times more powerful at warming the atmosphere than carbon dioxide. As the climate in the Arctic warms, its permafrost - frozen ground - is thawing out. Dead vegetation laid down over 30,000 years ago that became frozen in ice is now thawing out. As the permafrost melts it also forms new lakes where microbes digest the old vegetation and give off methane.

Katey Walter at the University of Alaska, Fairbanks has a dramatic test for finding the methane bubbles. She breaks the ice over Siberian lakes and drops a lighted match into the hole. The methane instantly ignites and can send a flame shooting up to 20ft high. By capturing methane under the ice, she estimates that the melting permafrost of Siberia alone could release up to 50bn tons of methane, 10 times more methane than exists in the Earth's atmosphere today. Because methane spreads rapidly through the atmosphere, and traps heat so efficiently, the Earth is expected to grow much warmer. The big fear is that the Arctic methane could trigger a runaway greenhouse effect. "Methane release due to thawing permafrost in the Arctic is a global warming wild card", warned a UN report last year. Large amounts entering the atmosphere would trigger abrupt climate changes likely to be irreversible.