CNN, By Matthew Knight, November 30
Concentrations of greenhouse gases in the Earth’s atmosphere reached record highs in 2011, according to new data published by the World Meteorological Organization (WMO).
The WMO’s annual Greenhouse Gas Bulletin, released Tuesday, reports that carbon dioxide rose to 390.9 parts per million (ppm), up two ppm on 2010 levels.
Carbon dioxide is the single most important greenhouse gas emitted by humans, says the WMO, and the increases recorded last year are in line with average rises seen each year over the last decade.
Combined with average yearly rises of 1.5 ppm during the 1990s, the WMO says radiative forcing (the warming effect on our climate) by long-lived greenhouse gases has now increased 30% since 1990.
Around 60% of methane released into the atmosphere comes from human activities such as farming, rice agriculture, fossil fuel exploitation, landfill and biomass burning, according to the WMO. In 2011, concentrations reached a new high of 1813 parts per billion (ppb), 259% higher than pre-industrial levels.
Emissions of nitrous oxide — 40% of which are estimated to come from human activity — reached 324.2 ppb, up one ppb on the 2010 figure and 120% higher than pre-industrial times.
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