WASHINGTON (AFP) — Global greenhouse gas emissions including main offender carbon dioxide rose in 2007 despite efforts to curb them, a US government agency said.
Atmospheric CO2 increased by 0.6 percent or 19 billion tonnes over 2006 levels, the National Oceanic and Atmospheric Administration (NOAA) said in preliminary data from its annual update to its greenhouse gas index.
"Viewed another way, last year's carbon dioxide increase means 2.4 molecules of the gas were added to every million molecules of air, boosting the global concentration to nearly 385 parts per million (ppm)," a NOAA statement said.
In the pre-industrial era, until 1850, the concentration of carbon dioxide in the air was roughly 280 ppm, the agency said.
Since 2000, carbon dioxide has increased two ppm a year on average, compared to 1.5 ppm per year in the 1980s and less than one ppm per year in the 1960s.
The burning of coal, oil and natural gas is the main source of carbon dioxide emissions. Oceans, vegetation and soils absorb about one half of all CO2 emissions, while the rest persists in the atmosphere for centuries.
About 20 percent of CO2 released from the burning of fossil fuels in 2007 will likely remain in the atmosphere for thousands of years, according to the latest scientific assessment by the International Panel on Climate Change.
Other than CO2 -- the key driver of global warming -- atmospheric levels of methane, another greenhouse gas, rose 20 million tonnes last year after a decade of remaining static, the NOAA said.
Methane is 25 times more powerful as a greenhouse gas than CO2 but there is much less of it in the atmosphere, so its overall impact on climate is roughly half that of CO2.
NOAA scientist Ed Dlugokencky said the sudden rise in methane levels in 2007 was probably due to rapid industrial growth in Asia and rising wetland emissions in the Arctic and the tropics.
NOAA tracks data from 60 sites around the world to compile its annual greenhouse gas index.
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