Dlugokencky et al., GRL (September 2009): Observational constraints on recent increases in the atmospheric CH4 burden

Geophysical Research Letters, 36 (2009) L18803; doi: 10.1029/2009GL039780.

Observational constraints on recent increases in the atmospheric CH₄ burden 

 E. J. Dlugokencky, L. Bruhwiler (NOAA Earth System Research Laboratory, Boulder, CO, U.S.A.), J. W. C. White (INSTAAR, University of Colorado, Boulder, CO, U.S.A.), L. K. Emmons (National Center for Atmospheric Research, Boulder, CO, U.S.A.), P. C. Novelli, S. A. Montzka, K. A. Masarie, P. M. Lang, A. M. Crotwell, J. B. Miller (NOAA Earth System Research Laboratory, Boulder, CO, U.S.A.) and L. V. Gatti (Divisao de Quimica Ambiental, Laboratorio de Quimica Atmosferica, Insituto de Pesquisas Energéticas e Nucleares, São Paulo, Brazil )

Received 6 July 2009; accepted 18 August 2009; published 17 September 2009. 

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.

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.

Link to abstract:  http://www.agu.org/pubs/crossref/2009/2009GL039780.shtml