Implications of the recent fluctuations in the growth rate of tropospheric methane

Global measurements show that the mixing ratio of tropospheric methane (CH4) increased by 1.1% (19.5 ± 1.7 ppbv) over the five‐year period 1996–2000, with striking fluctuations in its annual growth rate. Whereas the global CH4 growth rate reached 15.9 ± 0.7 ppbv yr−1 in 1998, the growth rate was −2....

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Bibliographic Details
Published in:Geophysical research letters 2002-05, Vol.29 (10), p.117-1-117-4
Main Authors: Simpson, Isobel J., Chen, Tai-Yih, Blake, Donald R., Rowland, F. Sherwood
Format: Article
Language:English
Subjects:
Air pollution
Extrapolation
Fluctuation
Greenhouse effect
Greenhouse gases
Methane
Monitoring
Retarding
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Summary:Global measurements show that the mixing ratio of tropospheric methane (CH4) increased by 1.1% (19.5 ± 1.7 ppbv) over the five‐year period 1996–2000, with striking fluctuations in its annual growth rate. Whereas the global CH4 growth rate reached 15.9 ± 0.7 ppbv yr−1 in 1998, the growth rate was −2.1 ± 0.8 ppbv yr−1 in 2000. This is the first time in our 23‐year global monitoring program that we have measured a negative annual CH4 growth rate. The CH4 growth rate fluctuates in an unpredictable fashion, and we reemphasize that global CH4 concentrations cannot be extrapolated into the future based on past trends. As a result, we suggest that the slowing of the CH4 growth rate during much of the 1980s and 1990s cannot be used to imply that CH4 will no longer be of concern in greenhouse gas studies during this century.
ISSN:0094-8276
1944-8007
DOI:10.1029/2001GL014521