Reuters: Gases blamed for global warming reached record levels in the atmosphere last year, the United Nations weather agency said on Tuesday. Concentrations of carbon dioxide (CO2) and nitrous oxide (N2O) touched new highs after more steady rises in 2007, and methane had its largest annual increase in a decade, the World Meteorological Organization said. “The major greenhouse gases — CO2, methane and N2O — have all reached new highs in 2007. Two of them, CO2 and N20, are increasing …