February 28, 2007
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FROM VOLUME 8, NUMBER 8, AUGUST 1995
OF GENERAL INTEREST: TROPICAL CLIMATE CHANGE
"Cooling of Tropical Brazil (5° C) During the Last Glacial Maximum,"
M. Stute (Lamont-Doherty Earth Observ., Rte. 9W, Palisades NY 10964), M. Forster
et al., Science, 269(5222), 379-382, July 21, 1995.
A 30,000-year paleotemperature record derived from noble gases dissolved in
C14-dated ground water indicates that the climate in lowland tropical Brazil was 5.4° C cooler during the last glacial maximum than today. The tropical Americas
appear to be characterized by a temperature sensitivity comparable to that found
in higher latitudes, in agreement with several other types of temperature
reconstruction, but contrary to the sea-surface temperature reconstruction of
"Cooling the Tropics," W.S. Broecker (Lamont-Doherty Earth
Observ., Rte. 9W, Palisades NY 10964), Nature, 376(6537),
212-213, July 20, 1995.
The recent paper by Thompson (see next entry) is the latest in a series of
results showing that the tropics did cool during glacial periods, contrary to
previous views. The findings send a strong warning to those who discount the
continuing buildup of greenhouse gases; the paleoclimate record shows that the
Earth's climate system is sensitive to even small nudges.
"Late Glacial Stage and Holocene Tropical Ice Core Records from
Huascarán, Peru," L.G. Thompson (Dept. Geolog. Sci., Ohio State
Univ., Columbus OH 43210), E. Mosley-Thompson et al., Science, 269(5220),
46-50, July 7, 1995.
Two ice cores from a Peruvian glacier show that glacial conditions in the
high-altitude tropics were as much as 8° to 12° C cooler than today. The
atmosphere contained 200 times as much dust, and the Amazon Basin forest may
have been much less extensive. A strong warming has dominated the last two
centuries. (A related news item appears on p. 32 of same issue.)
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