April 24, 2008 -- The National Oceanic and Atmospheric Administration released its 2007 measurements of atmospheric greenhouse gases yesterday, and the results were not encouraging.
"We're on the wrong track," said NOAA scientist Pieter Tans, who is in charge of its greenhouse gas measurements program headquartered in Boulder, Colo.
The average level of CO2 in the atmosphere increased by 2.4 parts per million in 2007, bringing the total to nearly 385 parts per million. Pre-industrial levels were around 280 parts per million.
"The rate of increase is accelerating," Tans said. CO2 levels rose about 1.5 ppm per year in the 1980s, and have risen around 2 ppm per year in recent years. Since 2000, levels have increased 3.3 percent per year on average, he said. 2007 marks the third highest annual increase in CO2.
"For the last four to five years we have set new records in burning fossil fuels," Tans added. Fossil fuel burning is the primary source of CO2 in the atmosphere.
"They're completely not surprising," Steven Wofsy of Harvard University in Cambridge, Mass., said of the findings. "With the big increase that we've seen in fossil fuels, the new values of 2-2.5 ppm are going to have to become the norm."
More surprising to climate researchers is that atmospheric methane levels increased this year by 27 million tons, after a decade of staying relatively constant.
Although there is much less methane in the atmosphere -- about 1800 parts per billion -- methane is 25 times more potent a greenhouse gas than CO2, because it absorbs more of the sun's energy.
"People really aren't sure why methane leveled off" in past years, said Ed Dlugokincky at NOAA.
A number of factors probably contributed to a decline in methane emissions beginning in the early 1990s, including a decline in production of fossil fuels in the former Soviet Union accompanying its economic collapse, he said, and efforts to reduce methane emissions from landfills and other human sources in Western Europe.
The 2007 rise is equally mysterious.
"We're pretty sure it's not the result of biomass burning," Dlugokincky said, because the researchers did not detect an increase in carbon monoxide levels, which would be present if burning were the culprit.
The measurements -- weekly samples from about 60 stations around the world -- suggest that methane increases may come from tropical and Arctic latitudes. This may mean that warmer, wetter weather over wetlands in these regions allowed bacteria there to produce more methane, Dlugokincky said.
Another possibility is that the increase marks the beginning of methane releases from the thawing of Arctic permafrost, a potentially huge source of greenhouse gases. Permafrost holds about the same amount of carbon as is present in all of the world's recoverable coal, he said.
"It's way too soon to answer a question like that," he cautioned. Longer term monitoring and more measurement stations in the Arctic will be needed to tell whether this is just a blip in the methane record caused by the right weather conditions, or whether this is a longer term trend.
"We are on the lookout in case something happens in the Arctic," Tans said.
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