CO2, methane up sharply in 2007

The amount of two key greenhouse gases in the Earth's atmosphere rose sharply last year, and carbon dioxide levels this year are literally off the chart, the US government reported.

In its annual index of greenhouse gas emissions, the National Oceanic and Atmospheric Administration found atmospheric carbon dioxide, the primary driver of global climate change, rose by 0.6 per cent, or 19 billion tons last year. The amount of methane increased by 0.5 per cent, or 27 million tons, after nearly a decade of little or no change, according to preliminary figures issued by scientists at the government's Earth System Research Laboratory in Colorado.

Methane's greenhouse effect is 25 times more potent than carbon dioxide's, but there is far less of it in the atmosphere.