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 12, NUMBER 1, JANUARY 1999
The Other Climate Changes
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 seas 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.
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