February 28, 2007
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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 11, NUMBER 7, JULY 1998
"Long-Term Growth at Elevated Carbon Dioxide Stimulates Methane
Emission in Tropical Paddy Rice," (see Impacts of Elevated CO2,
this Global Climate Change Digest issue--July 1998).
"Global Methane Emission from Wetlands and Its Sensitivity to Climate
Change," M. Cao, K. Gregson, S. Marshall (Biolog. Sci., Univ.
Nottingham, Loughborough LE12 5RD, UK; e-mail:
Stewart.Marshall@Nottingham.ac.uk),Atmos. Environ., 32(19),
3293-3299, Oct. 1998.
Uses process-based ecosystem models to estimate a global emission of 145
Tg/year, of which 92 Tg/year comes from natural wetlands and 53 Tg/year
from rice paddies. Emissions from high-latitude wetlands and rice paddies
were only half those reported in the traditional literature, confirming
more recent measurements. The models show that modest global warming may
produce a higher emission, but this effect may be reversed by larger
increases in temperature, because of soil moisture depletion.
"Atmospheric Methane Between 1000 A.D. and Present: Evidence of
Anthropogenic Emissions and Climatic Variability," D.M. Etheridge
(Atmos. Res., CSIRO, PMB 1, Aspendale, Victoria 3195, Australia; e-mail:
email@example.com), L.P. Steele et al.,J. Geophys. Res., 103(D13),
15,979-15,993, July 20, 1998.
Unifies and coordinates several records of methane including those from
ice cores. Calculates an average total methane source of 250 Tg/year for
1000-1800 A.D., reaching near stabilization at about 560 Tg/year in the
1980s and 1990s. The calculated trend of methane and one of its isotopes
supports the stabilization of the total methane source.
"Continuing Decline in the Growth Rate of the Atmospheric Methane
Burden," (see Of General Interest, this Global Climate Change
Digest issue--July 1998).
"Changing Concentration, Lifetime and climate Forcing of Atmospheric
Methane," J. Lelieveld (Inst. Marine & Atmos. Res.,
Princetonplein 5, 3584 CC Utrecht, Neth.), P.J. Crutzen, F.J. Dentener,Tellus,
50B(2), 128-150, Apr. 1998.
Reviews source and sink estimates and presents global 3D model
calculations, showing that the main features of the global methane
distribution are well represented. Scenario calculations indicate that the
importance of the climatic forcing of methane relative to that of CO2
will decrease from about 35% now to about 15% in the year 2050.
"Methane Fluxes on Boreal Peatlands of Different Fertility and the
Effect of Long-Term Experimental Lowering of the Water Table on Flux
Rates," H. Nykanen (Natl. Public Health Inst., POB 95, FIN-70701
Kuopio, Finland; e-mail: Hannu.Nykanen@ktl.fi), J. Alm et al.,Global
Biogeochem. Cycles, 12(1), 53-69, Mar. 1998.
Methane fluxes were measured at 17 peatland sites with different
nutritional and hydrological characteristics by a static chamber
technique. Results can be used to predict the possible changes in methane
emissions if climate is drying in the north. For instance, lowering the
present water table by 10 cm would induce a 70% reduction in emissions
from fens and a 45% reduction from bogs.
"Response of Tundra CH4 and CO2 Flux to
Manipulation of Temperature and Vegetation," J.H. Verville (Dept.
Biolog. Sci., Stanford Univ., Stanford CA 94305), S.E. Hobbie et al., Biogeochemistry,
41, 215-235, 1998.
Conducted removals of plant species, air temperature manipulations, and
vegetation and soil transplants in Alaskan wet-meadow and tussock tundra
communities. Results strongly suggest that changes in methane and CO2
flux in response to climate change will be more strongly mediated by
large-scale changes in vegetation and soil parameters than by direct
"Sensitivity of the Atmospheric CH4 Growth Rate to Global
Temperature Changes Observed from 1980 to 1992," S. Bekki (Ctr.
Atmos. Sci., Univ. Cambridge, Lensfield Rd., Cambridge CB2 1EW, UK), K.S.
Law, Tellus, 49B(4), 409-416, Sep. 1997.
Uses a 2-D chemistry-transport model to explore two competing
temperature dependencies of methane: emissions from wetlands, and
destruction related to OH concentration. The wetland effect dominates in
the Northern Hemisphere; the OH effect is more important in the tropics.
"North Siberian Lakes: A Methane Source Fueled by Pleistocene Carbon,"
S.A. Zimov...F.S. Chapin III (Dept. Integrative Biol., Univ. California,
Berkeley CA 94720) et al.,Science, 277(5327), 800-802,
Aug. 8, 1997.
Estimates that emissions from north Siberian lakes contributes about 1.5
teragrams of methane per year to observed winter increases in atmospheric
"Enhanced CH4 Emissions from a Wetland Soil Exposed to
Elevated CO2," J.P. Megonigal (Dept. Biol., George Mason
Univ., Fairfax VA 22030), W.H. Schlesinger, Biogeochemistry, 37(1)
77-88, Apr. 1997.
Glasshouse and growth chamber experiments show that elevated CO2
may dramatically increase methane emissions from wetlands, a source that
currently accounts for 40% of global emissions.
"An Inverse Modeling Approach to Investigate the Global Atmospheric
Methane Cycle," R. Hein (Inst. Physik Atmos., DLR Oberpfaffenhofen,
D-82234 Wessling, Ger.), P.J. Crutzen, M. Heimann,Global Biogeochem.
Cycles, 11(1), 43-76, Mar. 1997.
Deduces information on methane sources and sinks from observed spatial
and temporal variations of atmospheric methane mixing ratios, using a 3-D
atmospheric transport model combined with a tropospheric chemistry module.
Constructs two scenarios which reproduce the main features seen in the
NOAA/CMDL methane observations for the 1980s. Examines the decrease in
growth rate in the early 1990s, which cannot be associated uniquely with
any particular source.
Two related items in Nature, 385(6615), Jan. 30, 1997:
"Bottom Line for Hydrocarbons," I.R. MacDonald (College of
Geosci., Texas A&M Univ., College Sta. TX 77843), 389-390. There is
renewed scientific interest in oceanic methane gas hydratesa solid
form of methane combined with waterbecause they play a potentially
enormous role in the global carbon cycle. The following paper revises
upwards the world stores of gas hydrates.
"Direct Measurement of in situ Methane Quantities in a
Large Gas-Hydrate Reservoir," G.R. Dickens (Dept. Earth Sci., James
Cook Univ., Townsville, Queensland 4811, Australia), C.K. Paull et al.,
426-428. Reports direct measurements of methane stored as gas hydrate and
free gas in a sediment from the western Atlantic Ocean. Results indicate
substantial quantities of methane stored as gas hydrate, with an
equivalent or greater amount occurring as bubbles of free gas in the
sediments below the hydrate zone.
"Is the Amplitude of the Methane Seasonal Cycle Changing?" E.J.
Dlugokencky (NOAA/CMDL, 325 S. Broadway, Boulder CO 80303; e-mail:
firstname.lastname@example.org), K.A. Masarie et al.,Atmos. Environ., 31(1),
21-26, Jan. 1997.
Analyzes 12 years of data from a globally distributed set of sampling
sites. If there are systematic changes occurring in the seasonal cycle of
atmospheric methane, a longer record will be needed to extract them from
"Atmospheric Methane over the Last Century," M.A.K. Khalil
(Dept. Physics, Portland State Univ., POB 751, Portland OR 97207), M.J.
Shearer, R.A. Rasmussen,World Resource Review, 8(4),
481-492, Dec. 1996.
Reviews the role of methane in the environment and how well we
understand the trends over the last 100 years, particularly possible
reasons for the recent slowdown in the global rate of increase of methane
in the atmosphere.
"Changing Trends in Tropospheric Methane and Carbon Monoxide: A
Sensitivity Analysis of the OH Radical," H. van Dop (Inst. Marine &
Atmos. Res.-IMAU, Utrecht Univ., POB 80005, 3508 TA Utrecht, Neth.;
e-mail: email@example.com), M. Krol,J. Atmos. Chem., 25(3),
271-288, Nov. 1996.
Concludes that climatic fluctuations (tropospheric water vapor,
temperature and convective activity) and stratospheric ozone depletion
(through tropospheric UV radiation) have a significant influence on
tropospheric composition, and thus on trends in methane and carbon
"Nitrous Oxide and Methane fluxes from Perturbed and Unperturbed
Boreal Forest Sites in Northern Ontario," (see Nitrogen Cycle, this
Global Climate Change Digest issue--July 1998).
"Changes in CH4 and CO Growth Rates after the Eruption of
Mt. Pinatubo and Their Link with Changes in Tropical Tropospheric UV Flux,"
E.J. Dlugokencky (NOAA/CMDL, 325 S. Broadway, Boulder CO 80303; e-mail:
firstname.lastname@example.org), E.G. Dutton et al., Geophys. Res. Lett.,
23(20), 2761-2764, Oct. 1, 1996.
Trace gas measurements and calculations suggest that decreased UV flux
following the Pinatubo eruption decreased the steady-state OH
concentration, and led to the observed anomalously large growth rates for
methane and CO in the early 1990s.
"Deforestation and Methane Release from Termites in Amazonia,"
C. Martius (INPA, Caixa Postal 478, 69.011-970 Manaus-Amazonas, Brazil),
P.M. Fearnside et al.,Chemosphere, 33(3), 517-536, Aug.
Re-evaluates and rejects the hypothesis that deforestation leads to
higher populations of wood-feeding termites, and to a significant increase
in termite-emitted methane, in areas of cleared and burned former primary
"A Reevaluation of the Open Ocean Source of Methane to the
Atmosphere," T.S. Bates (PMEL, NOAA, 7600 Sand Pt. Way NE, Seattle WA
98115), K.C. Kelly et al.,J. Geophys. Res., 101(D3),
6953-6961, Mar. 20, 1996.
Using seawater and atmospheric methane mixing ratios measured on several
cruises in the Pacific, estimates a total global ocean-to-atmosphere flux
that is an order of magnitude less than estimated by the IPCC (1994).
Guide to Publishers
Index of Abbreviations