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U.S.: Two greenhouse gases rose sharply in '07

Arctic areas are dotted with lakes like these, which contain methane frozen in permafrost below the water.
Arctic areas are dotted with lakes like these, which contain methane frozen in permafrost below the water.NOAA
/ Source: staff and news service reports

Despite international levels to curb their growth, global emissions of two key greenhouse gases — carbon dioxide and methane — rose sharply last year and fears are that melting permafrost might be partly responsible for the latter, federal scientists reported Wednesday.

"Atmospheric carbon dioxide, the primary driver of global climate change, increased by 0.6 percent, or 19 billion tons," the National Oceanic and Atmospheric Administration said in a statement announcing the findings. "Additionally methane rose by 27 million tons after nearly a decade with little or no increase."

Attributed primarily to the burning of fossil fuels, carbon dioxide concentration in the air increased by 2.4 parts per million last year, NOAA's Earth System Research Laboratory reported. That means 2.4 molecules of carbon dioxide were added to every million molecules of air.

Since 2000, annual increases of 2 ppm or more have been common, compared with 1.5 ppm per year in the 1980s and less than 1 ppm per year during the 1960s, according to the lab, which traks emissions from 60 stations around the world.

Global concentration of carbon dioxide is now nearly 385 parts per million. Pre-industrial carbon dioxide levels hovered around 280 ppm until 1850. Human activities pushed those levels up to 380 ppm by early 2006.

Concern has grown in recent years about these gases, with most atmospheric scientists convinced that the increasing accumulation is causing the earth's temperature to rise, potentially disrupting climate and changing patterns of rainfall, drought and other storms.

The U.N.-sponsored Intergovernmental Panel on Climate Change has worked to detail the scientific basis of this problem, and the Kyoto agreement sought to encourage countries to take steps to reduce their greenhouse emissions. Some countries, particularly in Europe, have taken steps to reduce emissions.

Watching the permafrost
As for methane, vast amounts are stored in permafrost, or permanently frozen ground.

Methane is 25 times more potent as a greenhouse gas than carbon dioxide, but there's far less of it in the atmosphere. When related climate affects are taken into account, methane's overall climate impact is nearly half that of carbon dioxide.

Scientists are concerned that as the Arctic continues to warm and permafrost thaws, methane could seep into the atmosphere, possibly fueling a cycle of rising temperatures and more emissions released.

Until last year, global methane levels had been stagnant since 1998.

NOAA scientist Ed Dlugokencky said industrialization in Asia and rising wetland emissions in the Arctic and the tropics are the most likely causes of the methane increase.

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