Atmospheric methane levels off: Temporary pause or a new steady-state?
Article first published online: 8 OCT 2003
Copyright 2003 by the American Geophysical Union.
Geophysical Research Letters
Volume 30, Issue 19, October 2003
How to Cite
2003), Atmospheric methane levels off: Temporary pause or a new steady-state? Geophys. Res. Lett., 30, 1992, doi:10.1029/2003GL018126, 19., , , , , , and (
- Issue published online: 8 OCT 2003
- Article first published online: 8 OCT 2003
- Manuscript Accepted: 2 SEP 2003
- Manuscript Received: 8 JUL 2003
- Manuscript Revised: 8 JUL 2003
 The globally-averaged atmospheric methane abundance determined from an extensive network of surface air sampling sites was constant at ∼1751 ppb from 1999 through 2002. Assuming that the methane lifetime has been constant, this implies that during this 4-year period the global methane budget has been at steady state. We also observed a significant decrease in the difference between northern and southern polar zonal annual averages of CH4 from 1991 to 1992. Using a 3-D transport model, we show that this change is consistent with a decrease in CH4 emissions of ∼10 Tg CH4 from north of 50°N in the early-1990s. This decrease in emissions may have accelerated the global methane budget towards steady state. Based on current knowledge of the global methane budget and how it has changed with time, it is not possible to tell if the atmospheric methane burden has peaked, or if we are only observing a persistent, but temporary pause in its increase.