Article

Nature 399, 749-755 (24 June 1999) | doi:10.1038/21586; Received 18 December 1998; Accepted 28 April 1999

A record of atmospheric halocarbons during the twentieth century from polar firn air

James H. Butler1, Mark Battle2,5, Michael L. Bender2,5, Stephen A. Montzka1, Andrew D. Clarke3,5, Eric S. Saltzman4, Cara M. Sucher2,5, Jeffrey P. Severinghaus2,5 & James W. Elkins1

  1. National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado 80303, USA
  2. Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA
  3. Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Colorado 80309, USA
  4. Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida 33149, USA
  5. Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA (M.B., M.L.B.) National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado 80303, USA (A.D.C.) US Global Change Research Program, Washington DC 20024, USA (C.M.S.) Scripps Institution of Oceanography, La Jolla, California 92037, USA (J.P.S.).

Correspondence to: James H. Butler1 Correspondence and requests for materials should be addressed to J.H.B. (e-mail: Email: jbutler@cmdl.noaa.gov). Data for gases at all sampling sites are available at http://cmdl.noaa.gov/noah or by anonymous ftp at ftp://ftp.cmdl.noaa.gov/noah.

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Measurements of trace gases in air trapped in polar firn (unconsolidated snow) demonstrate that natural sources of chlorofluorocarbons, halons, persistent chlorocarbon solvents and sulphur hexafluoride to the atmosphere are minimal or non-existent. Atmospheric concentrations of these gases, reconstructed back to the late nineteenth century, are consistent with atmospheric histories derived from anthropogenic emission rates and known atmospheric lifetimes. The measurements confirm the predominance of human activity in the atmospheric budget of organic chlorine, and allow the estimation of atmospheric histories of halogenated gases of combined anthropogenic and natural origin. The pre-twentieth-century burden of methyl chloride was close to that at present, while the burden of methyl bromide was probably over half of today's value.