Atmospheric methane levels continued to increase in 2009, the World Meteorological Organisation’s annual Greenhouse Gas Bulletin (summary PDF) confirmed this week. Methane averaged 1803 ppb over the year, up 5 ppb on 2008, and now contributes 18.1% of the radiative forcing caused by current greenhouse gas levels. The Bulletin suggests that “likely causes were above average wetland methane emissions due to exceptionally warm temperatures at high northern latitudes in 2007 and heavy precipitation in tropical wetlands in 2007 and 2008. However, it cautions that the reasons for the recent increases are not yet fully understood.”
A hint that the rise might be continuing this year is contained in this rather striking graph of methane levels recorded recently at the Mt Zeppelin recording station (a misty mountain?) in Ny Ã…lesund, Svalbard…