Comments
Sources of the 2007 and 2008 Rises in Atmospheric Methane
After 10 years of stability for atmospheric methane concentration, there were rises in both 2007 and 2008. According to a new study published in Geophysical Research Letters (GRL) the source was not from the alarmists’ favourite CH4 hydrates and Arctic Permafrost. In 2007 the extra methane emissions came from northern wetlands, and in 2008 they came from tropical wetlands.
Dlugokencky, E. J., et al. (2009), Observational constraints on recent increases in the atmospheric CH4 burden, Geophys. Res. Lett., 36, L18803, doi:10.1029/2009GL039780.
Abstract:
Measurements of atmospheric CH4 from air samples collected weekly at 46 remote surface sites show that, after a decade of near-zero growth, globally averaged atmospheric methane increased during 2007 and 2008. During 2007, CH4 increased by 8.3 ± 0.6 ppb. CH4 mole fractions averaged over polar northern latitudes and the Southern Hemisphere increased more than other zonally averaged regions. In 2008, globally averaged CH4 increased by 4.4 ± 0.6 ppb; the largest increase was in the tropics, while polar northern latitudes did not increase. Satellite and in situ CO observations suggest only a minor contribution to increased CH4 from biomass burning. The most likely drivers of the CH4 anomalies observed during 2007 and 2008 are anomalously high temperatures in the Arctic and greater than average precipitation in the tropics. Near-zero CH4 growth in the Arctic during 2008 suggests we have not yet activated strong climate feedbacks from permafrost and CH4 hydrates.
Figure 1. Atmospheric methane concentrations, 1985-2008, with the IPCC methane projections overlaid (adapted from: Dlugokencky et al., 2009 by World Climate Report)