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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 10, OCTOBER 1998

PROFESSIONAL PUBLICATIONS...
OF GENERAL INTEREST

Item #d98oct1

“A Large Terrestrial Carbon Sink in North America Implied by Atmospheric and Oceanic Carbon Dioxide Data and Models,” S. Fan (Atmos. Ocean. Sci. Progr., Princeton Univ., Princeton, N.J., 08544; cmc@princeton.edu) et al., Science 282 (5388), 442-446 (1998).

The world was divided into three regions (North America, Eurasia-Africa, and the remainder of the world), and the uptake of CO₂ over each of these regions was estimated from (1) measurements of atmospheric CO₂ concentration that had been gathered by a worldwide network of 63 observational stations, (2) two atmospheric-transport models, (3) two estimates of the sea-air flux of CO₂, and (4) an estimate of the spatial distribution of fossil-fuel CO₂ emissions. Fitting the models to the observed data indicated a west-to-east gradient in estimated atmospheric CO₂, amounting to a decrease of up to 1.7 PgC/y across North America, mostly south of 51oN. The uptake was speculatively attributed to regrowth of forests on abandoned farms and logged-over sites and to the enhancement of plant and tree growth by anthropogenic nitrogen deposition, CO₂ fertilization, and global warming.

Item #d98oct2

“Simulated Influence of Carbon Dioxide, Orbital Forcing and Ice Sheets on the Climate of the Last Glacial Maximum,” A. J. Weaver, M. Eby, A. F. Fanning, and E. C. Wiebe,Nature 394, 847-853 (Aug. 27, 1998).

The climate of the Last Glacial Maximum (which occurred about 21,000 years ago) was modeled with a coupled atmosphere-ocean-sea-ice model to investigate the influences of atmospheric CO₂, the Earth’s orbit, and the ice-sheet albedo. Tropical temperatures were found to be a little more than 2°C lower than today’s temperatures. This result points to a low-to-medium climate sensitivity to radiative perturbations. Even colder temperatures were found in the northern North Atlantic region and were attributed to a weakening and shallowing of the thermohaline circulation. Analysis indicated that ocean-circulation changes since the Last Glacial Maximum did not directly contribute to the intervening change in global-mean temperature.

Item #d98oct3

“Making the Links,” Gunnar Kullenberg,Our Planet 9 (5), http://www.ourplanet.com/imgversn/95/gunnar.html (June 1998).

Among the major issues confronting the oceans in this the year of the ocean are several that impinge on climate change and global warming: the absorption of greenhouse gases, especially carbon dioxide; sea-level change; and large- scale perturbations, such as the El Niño phenomenon, tropical cyclones, and changes in ocean circulation. Kullenberg points out that we know from sediment studies, paleo-oceanography, and ice-core studies that changes can occur in both ocean circulation and climate in mere decades, or even years. However, we do not, as yet, understand the mechanisms that trigger changes. The same is true of the El Niño phenomenon. The requirement for remedying this situation is sustainable, adequate, and scientifically based observation. Such research is gradually being put in place through the Global Ocean Observing System, which is based on existing operational elements, and through modeling.