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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 12, NUMBER 1, JANUARY 1999

NEWS...
The Other Climate Changes

Item #d99jan38

In the article “Landscape Changes Make Regional Climate Run Hot and Cold” [Science 283, 317-319 (Jan. 8, 1999)], Jennifer Couzin notes that global warming (along with acid precipitation and ozone depletion) is the most commonly known form of climate change but that there are many others, and she gives a sampling of them:

• On the eastern plains of Colorado, dry prairie has been converted into irrigated agricultural fields. During the past decade, the mean July temperature has dropped as much as 2° C in lockstep with the expansion of irrigated acreage. Transpiration from the plants drives the cooling, and the moisture released to the atmosphere is swept upslope by the winds, increasing precipitation there.
• In the Amazon rainforest, slash-and-burn agriculture and forest-product extraction has replaced large tracts of forest with grasslands that do not transpire as much water as the vegetation they replaced. As a result, patches of climate that are 1° C warmer and 30% drier are now spread across Amazonia. Similar regions can be found in sub-Saharan Africa.
• A survey of 16 years of weather records for the U.S. eastern seaboard revealed that 20% more rain fell over the Atlantic on weekends than on weekdays and coastal cyclones were weaker on weekends. These patterns result from a buildup of industrial and transportation pollutants during the week, providing a buildup of condensation nuclei to produce cloudiness and rain.
• Upstream from the Aral sea, decades of overirrigation have siphoned off the sea’s source waters, causing the waters to recede miles from the former shores and leaving the former seabed bare and dusty. Without the moderating influence of the water, summers have gotten hotter and drier, and winters have gotten colder.

Although these examples are all regional changes, global change is, after all, the sum total of regional changes.