January 1, 2015.
Atmospheric methane has important indirect and direct contributions to climate. It has a radiative forcing of 0.5 W/m2 which is second only to carbon dioxide. It is also important in atmospheric chemistry by affecting the oxidizing capacity of the atmosphere. The main sources of methane to the atmosphere are known but the relative contributions of each source have large uncertainties. Atmospheric measurements are used to try to understand methane’s budget of emissions and losses. Approximately 2/3 of methane emissions are from anthropogenic sources (fossil fuel exploitation, ruminant animals, landfills, and rice agriculture) and about 1/3 are from natural sources (wetlands, termites, and natural geologic seeps). Its main loss is reactions with hydroxyl (OH) radicals in the troposphere. From 1983-1999 the rate of increase of atmospheric methane was decreasing and its atmospheric burden remained nearly constant from 1999 until 2006. In 2007, atmospheric methane began increasing again at a rate comparable to the late 1980s. Superimposed on top of the long term changes are shorter interannual variations in methane growth rate. Both the long and short term behavior reveal information about processes that emit it to or remove it from the atmosphere. In this presentation, we focus on the potential of tropical wetlands as a driver of the long term behavior of methane.
National Oceanic Atmospheric Administration Earth Systems Research Laboratory (NOAA ESRL)
This material is based upon work supported by the National Science Foundation under Grant No. 1340110 and is made possible with contributions from the S.D. Bechtel Jr. Foundation, Howard Hughes Medical Institute, Chevron Corporation, National Marine Sanctuary Foundation, and from the host research center. Any opinions, findings, and conclusions or recommendations expressed in this material are solely those of the authors. The STAR Program is administered by the Cal Poly Center for Excellence in STEM Education on behalf of the California State University system.