U.N.: Greenhouse gases at record high in 2011 Smokestack emissions are seen in this time exposure photograph taken outside the La Cygne Generating Station's coal-fired power plant Thursday, Jan. 19, 2012, in La Cygne, Kan. / AP Photo/Charlie Riedel GENEVA The U.N. weather agency says concentrations of the main global warming pollutant in the world's air reached a record high in 2011. The World Meteorological Organization says the planet averaged 390 parts per million of heat-trapping carbon dioxide in the atmosphere - up 40 percent from before the Industrial Age, when levels were about 275 parts per million. WMO officials said Tuesday there was a 30 percent increase in the warming effect on the global climate between 1990 and 2011, mainly due to carbon dioxide from fossil fuel burning. WMO Secretary-General Michel Jarraud said the 350 billion metric tons of carbon dioxide added to the atmosphere since 1750 "will remain there for centuries, causing our planet to warm further and impacting on all aspects of life on earth."