Greenhouse gases rise sharply in 2007

Global levels of atmospheric carbon dioxide (CO2), the primary driver of global warming, last year increased by 0.6%, or 19 billion tonnes, scientists at the US National Oceanic and Atmospheric Administration (NOAA) have found. Methane, which is 25 times more potent as a greenhouse gas than CO2, also rose by 27 million tonnes after nearly a decade with little or no increase.

Methane levels rose last year for the first time since 1998. NOAA scientist Ed Dlugokencky said rapid industrialisation in Asia and rising wetland emissions in the Arctic and tropics are the most likely causes of the increase.

Permafrost, or permanently frozen ground, contains vast stores of carbon. Scientists are concerned that as the Arctic continues to warm
and permafrost thaws, carbon could seep into the atmosphere in the form of methane, possibly fuelling a cycle of carbon release and
temperature rise.

"We’re on the lookout for the first sign of a methane release from thawing Arctic permafrost," said Dlugokencky. "It’s too soon to tell
whether last year’s spike in emissions includes the start of such a trend."

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