Web Release Date: February 14,
Atmospheric Methane: Trends and Cycles of Sources and Sinks
and
Department of Physics, Portland State University, P.O. Box 751, Portland, Oregon 97207, and Department of Environmental Science, Oregon Graduate Institute, Beaverton, Oregon 97006
Received for review July 27, 2006
Revised manuscript received January 10, 2007
Accepted January 13, 2007
Abstract:
For more than 20 years the global emissions and the lifetime of methane have probably been constant, so the buildup of methane in the atmosphere has been slowing down for as long. During this time, there have been periodic events occurring every seven to eight years, when global methane concentrations increased by some 10 ppb and later fell back, in some cases due to temporary increases of emissions from the northern tropics that spread to the global scale. These conclusions are derived from the accumulated global observations that now span 23 years and define the role of human activities in the recent cycle of atmospheric methane.
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