(CNN) -- 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. "These
billions of tons of additional carbon dioxide in our atmosphere
will remain there for centuries, causing our planet to warm
further and impacting on all aspects of life on Earth," WMO
secretary general Michel Jarraud said in a statement. According
to the WMO, about 375 billion tons of carb