February 28, 2007
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FROM VOLUME 12, NUMBER 4, APRIL 1999
JOURNAL ARTICLES...EL NIÑO
Genesis and Evolution of the 1997-98 El Niño, M. J.
McPhaden,Science 283 (5404), 950-954 (1999).
Data from satellites and a network of buoys moored near the equator
indicated a build-up of excess heat in the western Pacific in 1995 and
1996. The onset of the El Niño was triggered by weather systems
migrating into the western Pacific from the Indian Ocean in late 1996. In
early 1997, a weakening and reversal of the trade winds in the equatorial
Pacific rapidly led to unusually warm sea-surface waters. With the
collapse of the easterly trade winds, warm surface waters migrated
eastward from the western Pacific. In early 1998, the high sea-surface
temperatures added to the usual seasonal warming. When the trade winds
abruptly returned to near normal strength in the eastern Pacific in May
1998, the cold subsurface waters were drawn upwards, and sea-surface
temperatures plummeted, marking an end to the El Niño. The study
also suggests that natural decadal fluctuations in ocean conditions may
have combined with global warming to influence the 1997-98 El Niño.
Horse Sickness and ENSO in South Africa, M. Baylis, P. S.
Mellor, and R. Meiswinkle,Nature 397, 574 (1999).
Meteorological patterns and records about epidemics of African horse
sickness back to 1803 were analyzed, and 13 of the 14 outbreaks of African
horse sickness coincided with an El Niño. A spell of drought
followed by heavy rainfall, climatological results associated with El Niño,
seems to alter the breeding sites and to increase the population of the
biting midge, the insect that spreads the disease. These results imply
that the increasing frequency of El Niño currently observed could
result in an increase in a range of diseases spread by flying insects,
including diseases that affect humans.
El Niño and Global Warming, K. E. Trenberth,Current:
The Journal of Marine Education 15, 12-18 (1998).
El Niños transfer heat from the Pacific Ocean to the atmosphere,
and the global mean temperature peaks three to four months after an El Niño
peaks. This warming helps dry out regions in Indonesia, Australia, Africa,
and South America already prone to drought. Analysis indicates that a
departure by one standard deviation in the Southern Oscillation Index
results in a warming of the global atmosphere of about 0.1° C. The
theory is put forth that much of the heat trapped by the greenhouse effect
may be going into the oceans and later released through such mechanisms as
El Niño, producing El Niños that are larger and more
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