The amount of heat-trapping carbon dioxide in the atmosphere reached a record 390.9 parts per million (ppm) in 2011, according to a report released Tuesday by the UN’s World Meteorological Organization (WMO). That’s a 40 percent increase over levels in 1750, before humans began burning fossil fuels in earnest.
Although CO2 is still the most significant long-lived greenhouse gas, levels of other heat-trapping gases have also climbed to record levels, according to the report. Methane, for example hit 1813 parts per billion (ppb) in 2011, and nitrous oxide rose to 324.2 ppb. All told, the amount of excess heat prevented from escaping into outer space was 30 percent higher in 2011 than it was as recently as 1990.
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