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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 1-2, JANUARY-FEBRUARY 1998

PROFESSIONAL PUBLICATIONS...
CLIMATE MECHANISMS AND FEEDBACKS

Item #d98feb46

"Climate Change and the Global Atmospheric Electrical System," R.G. Harrison (Dept. Meteor., Univ. Reading, POB 243, Earley Gate, Reading RG6 6BB, UK; e-mail: r.g.harrison@uk.ac.rdg),Atmos. Environ., 31(20), 3483-3484, Aug. 4, 1997.

Proposes briefly that in tropical regions, an increase in lightning can be expected from an increase in temperature, a non-linear effect that could have consequences for global ozone and even CO₂.

Item #d98feb47

"Responses of Atmospheric Methane Consumption by Soils to Global Climate Change," G.M. King (Marine Ctr., Univ. Maine, Walpole ME 04573; e-mail: gking@maine.edu),Global Change Biology, 3(4), 351-362, Aug. 1997.

Reviews a number of analyses indicating that atmospheric methane consumption is generally reduced by human activities such as ammonium deposition and changes in hydrology. Future trends in the soil methane sink are likely to increase the accumulation of atmospheric methane.

Item #d98feb48

"The Potential for Feedback Effects Induced by Global Warming on Emissions of Nitrous Oxide by Soils," K.A. Smith (Inst. Ecol., Univ. Edinburgh, Edinburgh EH9 3JG, UK; e-mail: k.a.smith@ed.ac.uk),Global Change Biology, 3(4), 327-338, Aug. 1997.

A review concluding that models of global and regional trends give very conflicting predictions of the direction and magnitude of climatic impacts on nitrous oxide fluxes, but the prediction of a positive feedback seems to be the more soundly based.

Item #d98feb49

"Predicted Reduction in Basal Melt Rates of an Antarctic Ice Shelf in a Warmer Climate," K.W. Nicholls (Brit. Antarctic Survey, High Cross, Madingley Rd., Cambridge CB3 0ET, UK; e-mail: k.nicholls@bas.ac.uk),Nature, 388(6641), 460-461, July 31, 1997.

Uses measurements of temperature in a cavity beneath the Filchner-Ronne Ice Shelf made during springtime warming as an analog for climate warming. Concludes that moderate warming could lead to a basal thickening of the shelf, perhaps increasing its longevity.

Item #d98feb50

"How Dry Is the Tropical Free Troposphere? Implications for Global Warming Theory," R.W. Spencer (NASA/Marshall Space Flight Ctr., ES41, Huntsville Al 35806), W.D. Braswell,Bull. Amer. Meteor. Soc., 78(6), 1097-1106, June 1997.

The low humidity zones of the tropical free troposphere are poorly measured by radiosondes, leading to substantial uncertainty in GCM simulations. The latest satellite-based, microwave humidity sounder data suggest even drier conditions than have been previously reported. This underscores the importance of understanding how these low humidity levels are controlled in order to tune and validate GCMs, and to predict the magnitude of water vapor feedback and thus global warming.

Item #d98feb51

"Variations in the Tropical Greenhouse Effect During El Niño," B.J. Soden (NOAA/GFDL, POB 308, Princeton NJ 08542; e-mail: bjs@gfdl.gov),J. Clim., 10(5), 1050-1055, May 1997.

Addresses the controversy over the role of water vapor as a feedback mechanism of greenhouse warming. Results presented here provide observational support for a positive water vapor feedback, and show that GCMs are capable of simulating this effect.

Item #d98feb52

"Inherently Unstable Climate Behavior Due to Weak Thermohaline Ocean Circulation," E. Tziperman (Dept. Environ. Sci., Weizmann Inst. Sci., Rehovot 76100, Israel; e-mail: eli@beach.weizmann.ac.il),Nature, 386(6625), 592-595, Apr. 10, 1997.

Simulations of greenhouse warming often predict a weakening of the thermohaline circulation (THC). This study uses a global coupled ocean-atmosphere-ice GCM with realistic geography to show that there is a wide range of weak mean states of the THC that cannot be stably sustained by the climate system (and that would lead to climate fluctuations).

Item #d98feb53

Two related items in Nature, 386(6626), Apr. 17, 1997:

"From the Labrador Sea to Global Change," B. Dickson (Ctr. for Environ., Pakefield Rd., Lowestoft, Suffolk NR33 0HT, UK), 649-650. Comments how studies like the following are providing an understanding of the powerful changes that have occurred in the North Atlantic, and how those changes may relate to global shifts in climate.

"Surprisingly Rapid Spreading of Newly Formed Intermediate Waters Across the North Atlantic Ocean," A. Sy (Bundesamt für Seeschiffahrt und Hydrographie, Bernhard-Nocht-Str. 78, D-20359 Hamburg, Ger.; e-mail: sy@bsh.d400.de), M. Rhein et al., 675-679. Ocean temperature, salinity and chlorofluorocarbon concentration data show that water masses formed by deep convection in the Labrador Sea spread three to four times faster than previously estimated, with associated consequences for the North Atlantic thermohaline circulation.

Item #d98feb54

Two related items in Nature, 385(6618), Feb. 20, 1997:

"Cool Tropical Punch of the Ice Ages," C. Charles (Scripps Inst. Oceanog., La Jolla CA 92093; e-mail: ccharles@ucsd.edu), 681-683. Comments on the following article and other recent studies describing observations of past tropical sea surface temperatures, which imply that the tropical oceans are dynamically involved in glacial cycles. The nature of tropical cooling during ice ages bears on the sensitivity of the climate system to perturbations, including possible future anthropogenic effects.

"Influence of Ocean Heat Transport on the Climate of the Last Glacial Maximum, R.S. Webb (NOAA-NGDC Paleoclim. Prog., 325 Broadway, Boulder CO 80303; e-mail: rwebb@ngdc.noaa.gov), D.H. Rind et al., 695-699. Climate simulations suggest (among other things) that climate sensitivity for increased CO₂ may be higher than the IPCC "best estimates."

Item #d98feb55

"The Impact of Permafrost Thawing on the Carbon Dynamics of Tundra," C. Waelbroeck (Ctr. Faibles Radioactiv., Lab. mixte CNRS-CEA, 91198 Gif-sur-Yvette Cedex, France; e-mail: clairew@cfr.cnrs-gif.fr), P. Monfray et al.,Geophys. Res. Lett., 24(3), 229-232, Feb. 1, 1997.

A multi-component model shows that the tundra ecosystem's response to thawing may be a long-lasting increase in carbon accumulation, following a temporary increase in CO₂ emissions.

Item #d98feb56

"Polar Snow Cover Changes and Global Warming," H. Ye (Dept. Geog., Univ. Delaware, Newark DE 19716), J.R. Mather,Intl. J. Climatol., 17(2), 155-162, Feb. 1997.

Studies doubled CO₂ temperature and precipitation predictions from three GCMs for all land areas poleward of 60 latitude. Total accumulation increases poleward of 60 latitude, with a major increase in the Antarctic and a slight decrease in the Northern Hemisphere.

Item #d98feb57

"Principles for a Climate Regulation Mechanism during the Late Phenerozoic Era, Based on Carbon Fixation in Peat-Forming Wetlands," L.G. Franzén (Dept. Phys. Geog., Göteborg Univ., S-413 81 Gothenburg, Sweden; e-mail: LARS@gig.gu.se), D. Chen, L.F. Klinger,Ambio, 25(7), 435-442, Nov. 1996.

Models the climate regulating effect of peat bogs, which act as carbon sinks. With present levels of CO₂, the model shows that the initiation of a new ice age could already have been delayed roughly 700-1000 years. Scenarios with further increases in CO₂ show a much longer delay.

Item #d98feb58

"Water Vapor and Cloud Feedback over the Tropical Oceans: Can We Use ENSO as a Surrogate for Climate Change?" K.-M. Lau (NASA-Goddard, Greenbelt MD 20771; e-mail: lau@climate.gsfc.nasa.gov), C.-H. Ho, M.-D. Chou,Geophys. Res. Lett., 23(21), 2971-2974, Oct. 15, 1996.

Global climate model experiments show that regionally based interannual variability should not be used to infer radiative feedback sensitivity for climate change, unless proper corrections are made for the effect of large scale circulation.