DATE RESOURCES AND MEASUREMENT

1983 - PRESENT

Globally-averaged, monthly mean atmospheric methane abundance is determined from marine surface sites. The Global Monitoring Division of NOAA's Earth System Research Laboratory has measured methane since 1983 at a globally distributed network of air sampling sites.

Credits: Ed Dlugokencky, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends_ch4/)

The methane ice core records for this time period are derived from three cores obtained from Law Dome, East Antarctica from 1987 to 1993, and samples from the Eurocore and GISP2 ice cores from the Summit region, Greenland. The Law Dome sites satisfy many of the desirable characteristics of an ideal ice core site for atmospheric reconstructions including negligible melting of the ice sheet surface, low concentrations of impurities, regular stratigraphic layering undisturbed at the surface by wind or at depth by ice flow, and high snow accumulation rate.

1000 years ago - 1980

Credits:

Etheridge, D.M., et al., 2002

Ice Core, Firn Air and Archived Air Atmospheric Methane Concentration Data

IGBP PAGES/World Data Center for Paleoclimatology

Data Contribution Series #2002-039.

NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Etheridge, D. M., Steele, L. P., Francey, R. J., and Langenfelds, R. L., 1998, Atmospheric methane between 1000 A.D. and present: Evidence of anthropogenic emissions and climatic variability J. Geophys. Res. Vol. 103, No. D13, p. 15,979 (98JD00923)

800,000 YEARS AGO - 1000 YEARS AGO

Changes in past atmospheric methane concentrations are determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric methane levels over the past 800,000 years.

Credits: Loulergue, L., A. Schilt, R. Spahni, V. Masson-Delmotte, T. Blunier, B. Lemieux, J.-M. Barnola, D. Raynaud, T.F. Stocker, and J. Chappellaz. 2008.

Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years.

Nature, Vol. 453, pp. 383-386, 15 May 2008. doi:10.1038/nature06950

METHANE

A hydrocarbon gas produced both through natural sources and human activities, including the decomposition of wastes in landfills, agriculture, and especially rice cultivation, as well as ruminant digestion and manure management associated with domestic livestock. On a molecule-for-molecule basis, methane is a far more active greenhouse gas than carbon dioxide, but also one which is much less abundant in the atmosphere.