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Comment on 'A dramatic decrease in the growth rate of atmospheric methane in the Northern Hemisphere during 1992' by E. J. Dlugokencky et al.The carefully measured decrease in the growth rate of atmospheric methane (CH4) in 1992 reported by Dlugokencky et al. (1994) is an impressive accomplishment, and testimony for the importance of maintaining high-quality, long-term monitoring of atmospheric composition. The changing growth rate of atmospheric CH4 has important implications for assessing and understanding the potential magnitude and rates of a future greenhouse gas-induced climate change. Furthermore, the CH4 data from the current Climate Monitoring and Diagnostics Laboratory (CMDL) globally-distributed network of cooperative air sampling sites are clearly the best record of global CH4 trends and distribution currently available. However, we argue briefly here that the speculation by Dlugokencky et al. (1994) on possible mechanisms for the decreased growth rate in 1992 is only one scenario of many that could possibly fit with the constraints imposed by the reported data. Our comments are to (1) illustrate the difficulties of deducing small changes in complex, poorly understood, geographically diverse natural and anthropogenic sources of CH4 from measurements at the remotely-located CMDL sampling sites and (2) emphasize that detailed bottoms-up analyses are necessary to really advance the understanding of changes in source strengths; we are not promoting alternative mechanisms to explain the 1992 decrease in atmospheric CH4.
Document ID
19950036073
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Hogan, Kathleen B.
(U.S. Environmental Protection Agency, Washington, DC United States)
Harriss, Robert C.
(NASA Headquarters Washington, DC United States)
Date Acquired
August 16, 2013
Publication Date
November 1, 1994
Publication Information
Publication: Geophysical Research Letters
Volume: 21
Issue: 22
ISSN: 0094-8276
Subject Category
Environment Pollution
Accession Number
95A67672
Distribution Limits
Public
Copyright
Other

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