HR: 0800h
AN: B51D-0256    [Abstracts]
TI: Long-Term Trends of Methane Sources
AU: * Khalil, M K
EM: aslamk@pdx.edu
AF: Portland State University, Department of Physics, P.O.Box 751, Portland, OR 97207-0751 United States
AU: Butenhoff, C L
EM: christop@global.phy.pdx.edu
AF: Portland State University, Department of Physics, P.O.Box 751, Portland, OR 97207-0751 United States
AB: By combining the ambient measurements from OGI and NOAA programs, we construct a 23 year global time series of methane measurements spanning the polar, middle and tropical regions of both hemispheres from 1980 to 2003. The time series is used to evaluate the emissions of methane over this time and to use the results to define the role of human activities on the recent global changes of atmospheric methane. The results show that for the duration of the measurements the buildup of methane in the atmosphere has been slowing down. The global emissions as calculated by using a low resolution chemistry-transport model, have been constant for as long. It is possible that emissions have been falling, especially during the last decade depending on whether OH has fallen or not. The OH trends are taken from calculations using methyl chloroform measurements over the same time and locations as the methane time series. During the span of the measurements, there have been three or four occasions when larger than normal emissions of methane have occurred originating in the Northern Hemisphere, probably in the tropics, that have spread to the global scale. This research was supported by the Office of Science (BER), US Department of Energy, Grants No. DE-FG02-04ER63913 and DE-FG03-01ERG63262.
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: Fall Meeting 2005