Methane as a Greenhouse Gas
CCSP Research Highlight 1

NOAA

NOAA’s carbon-monitoring network gives the largest spatial distribution of global methane measurements. Samples processed at the agency’s Climate Monitoring and Diagnostics Lab (CMDL) in Boulder, Colo., are taken from nearly 50 sites covering the planet to derive overall global methane concentrations in the atmosphere.

CMDL research indicates that over the past decade, although methane concentrations have continued to increase, the overall rate of methane growth has slowed. In the late 1970s, the growth rate was approximately 20 ppbv per year. In the 1980s, growth slowed to 9-13 ppbv per year. The period of 1990 to 1998 saw variable growth of between 0 and 13 ppbv per year (IPCC, 2001) . A recent study by Dlugokencky, et. al. shows that atmospheric methane has been at a steady state of 1751 ppbv between 1999 and 2002. (See Figure 2, from Dlugokencky, et. al., 2003.)

NOAA also generates atmospheric transport models to learn more about methane sources and sinks. These models indicate how methane concentrations vary by latitude, season or other parameters. One of the key pieces of information derived is the imbalance between emissions and the earth’s ability to reabsorb it – essential in studying atmospheric methane’s lifespan and its climate-forcing capacity.