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Observational constraints on recent increases in the atmospheric CH4 burden
NOAA Earth System Research Laboratory, Boulder, Colorado, USA
NOAA Earth System Research Laboratory, Boulder, Colorado, USA
INSTAAR, University of Colorado, Boulder, Colorado, USA
National Center for Atmospheric Research, Boulder, Colorado, USA
NOAA Earth System Research Laboratory, Boulder, Colorado, USA
NOAA Earth System Research Laboratory, Boulder, Colorado, USA
NOAA Earth System Research Laboratory, Boulder, Colorado, USA
NOAA Earth System Research Laboratory, Boulder, Colorado, USA
NOAA Earth System Research Laboratory, Boulder, Colorado, USA
NOAA Earth System Research Laboratory, Boulder, Colorado, USA
Divisao de Quimica Ambiental, Laboratorio de Quimica Atmosferica, Insituto de Pesquisas Energéticas e Nucleares, São Paulo, Brazil
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.
Received 6 July 2009; accepted 18 August 2009; published 17 September 2009.
Citation: (2009), Observational constraints on recent increases in the atmospheric CH4 burden, Geophys. Res. Lett., 36, L18803, doi:10.1029/2009GL039780.
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