The concentration of greenhouse gases in the atmosphere hit a record high in 2011, the United Nations' World Meteorological Organization (WMO) reported Tuesday (Nov. 20).
Chief among these heat-trapping gases is carbon dioxide (CO2), the biggest culprit behind global warming. Carbon dioxide levels reached about 390.9 parts per million last year, which is 140 percent of the pre-industrial level of 280 parts per million and nearly 2 parts per million higher than the 2010 carbon dioxide level, according to the WMO report.
The international body estimates that about 413 billion tons (375 billion metric tons) of carbon have been released into the atmosphere since 1750, primarily from fossil fuel combustion. About half of this atmospheric carbon dioxide remains in the atmosphere, and much of it will linger for centuries, causing the planet to warm further, WMO Secretary-General Michel Jarraud warned.
Historically, the Earth's oceans and forests have helped balance the atmosphere's carbon equation by sucking up large amounts of the greenhouse gas. But Jarraud said natural carbon sinks might not be able to mitigate the problem as effectively in the future.