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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 1, NUMBER 3, SEPTEMBER 1988
PROFESSIONAL PUBLICATIONS...
ATMOSPHERIC METHANE
Item #d88sep14
 "Fossil Carbon Sources of Atmospheric Methane," W.M. Sackett,
T.R. Barber, Nature, 334(6179), 201, July 21, 1988.
Item #d88sep15
"Climatic and CH4 Cycle Implications of Glacial-Interglacial CH4
Change in the Vostok Ice Core," D. Raynaud (Lab. Glaciologie, BP 96 38402,
St. Martin d'Héres Cedex, France), J. Chappellaz et al., Nature,
333(6174), 655-657, June 16, 1988.
Strong evidence from analysis of the Vostok ice core shows CH4
concentrations increased from 0.34 to 0.62 ppmv between the end of the
penultimate ice age and the following interglacial, about 160-120 kyr BP. The
contributions of CH4 and associated chemical feedback to the global warming is
estimated to be about 25% of that due to CO2.
Item #d88sep16
"The Global Distribution of Methane in the Troposphere," L.P.
Steele (Coop. Inst. Res. Environ. Sci., Univ. Colorado/NOAA, Boulder, CO 80309),
P.J. Fraser et al., J. Atmos. Chem., 5, 125-171, June 1987.
Methane in air samples collected at roughly weekly intervals for 2 years, at
23 globally distributed sites in the NOAA/GMCC cooperative flask sampling
network, was measured by gas chromatography with a flame ionization detector at
a precision of 0.2%. A complete seasonal cycle of methane at the South Pole is
reported for the first time. Globally averaged background concentrations in the
marine boundary layer calculated for this two-year period indicate an average
increase of 12.8 ppb per year. Evidence is presented that shows a slowing of the
methane growth rate.
Item #d88sep17
"Methane Concentration in the Glacial Atmosphere Was Only Half That
of the Preindustrial Holocene," B. Stauffer (Phys. Inst., Univ. Bern, 3012
Bern, Switzerland), E. Lochbronner et al., Nature, 332(6167),
812-814, Apr. 28, 1988.
Measurements on ice core samples from Byrd Station (Antarctica) and Dye 3
(Greenland) show atmospheric methane concentration was only about 350 ppbv
during the last glaciation, 650 ppbv for a mean preindustrial level, and 1,650
ppbv today.
Item #d88sep18
"Continuing Worldwide Increase in Tropospheric Methane, 1978 to
1987," D.R. Blake (Dept. Chem., Univ. California, Irvine CA 92717), F.S.
Rowland, Science, 239(4844), 1129-31, Mar. 4, 1988.
The average worldwide tropospheric mixing ratio of methane has increased by
11%, from 1.52 ppmv in January 1978 to 1.684 ppmv in September 1987, for an
increment of 0.016+0.001 ppmv per year. The growth in tropospheric methane may
have increased the water concentration in the stratosphere by as much as 28%
since the 1940s and 45% over the past two centuries, and thus could have
increased the mass of precipitable water available for formation of polar
stratospheric clouds.
Item #d88sep19
"Atmospheric Methane: Trends Over the Last 10,000 Years,"
M.A.K. Khalil (Inst. Atmos. Sci., Oregon Grad. Ctr., 19600 N.W. Von Neumann Dr.,
Beaverton OR 97006), R.A. Rasmussen, Atmos. Environ., 21(11), 2445-52,
Nov. 1987.
A construction of atmospheric methane over the last 10,000 years shows that
it has increased to more than double the natural levels of a century ago.
Observations show that CH4 concentrations remained virtually unchanged over
thousands of years until about a few hundred years ago. Rates of increase are
explained by a global mass balance model. In the model, the increase of
emissions from sources affected by human activities is taken to be proportional
to the population, and the atmospheric lifetime of CH4 is taken to be increasing
if human activities are slowly depleting OH radicals that remove CH4 from the
atmosphere.
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