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Embargoed until 2 P.M., EST
NSF PR 01-100 - December 6, 2001
Tiny Particles of Pollution May Carry Large Consequences
for Earth's Water Supply
A new study conducted by researchers at the Scripps
Institution of Oceanography at the University of California,
San Diego, argues that particles of human-produced
pollution may be playing a significant role in weakening
Earth's water cycle much more than previously realized.
The study was funded by the National Science Foundation
(NSF) and other federal agencies.
Tiny aerosols primarily made up of black carbon, the
Scripps scientists argue, can lead to a weaker hydrological
cycle, which connects directly to water availability
and quality, a major environmental issue of the 21st
century. The paper, based on results obtained during
the international Indian Ocean Experiment (INDOEX),
is published in the December 7 issue of the journal
Science.
"By combining a unique set of field measurements with
models, INDOEX scientists have provided strong evidence
that human-produced atmospheric pollution may be having
a profound effect on the Earth's water cycle, weakening
it as pollution increases," said Jay Fein, director
of NSF's climate dynamics program, which funded the
research. "The large extent and magnitude of the effect
is an unexpected discovery which will have important
implications for environmental policy."
"Initially we were seeing aerosols as mainly a cooling
agent, offsetting global warming; in this article
we are saying that perhaps an even bigger impact of
aerosols is on the water budget of the planet," said
Scripps scientist V. Ramanathan, who along with Scripps
scientist Paul Crutzen, a co-author of the new study,
led the INDOEX science team as co-chief scientists.
"Through INDOEX we found that aerosols are cutting
down sunlight going into the ocean. The energy for
the hydrological cycle comes from sunlight."
The $25 million INDOEX project involved more than 150
scientists across several disciplines from Austria,
France, Germany, India, Maldives, the Netherlands,
Sweden and the United States. The project was sponsored
primarily by the National Science Foundation and the
Department of Energy, and funded in part by NASA and
the National Oceanic and Atmospheric Administration.
It focused on the Indian Ocean region in a Smultiplatform"
analysis approach of satellites, aircraft, ships,
surface stations and balloons. The project was designed
to assess the nature and magnitude of the chemical
pollution over the tropical Indian Ocean and to assess
the significance of the region's aerosols.
Early on INDOEX researchers documented a human-produced
brownish-gray haze layer of about 10 million square
kilometers over the Indian-Asian region. The particles
within the haze, researchers discovered, were causing
a three-fold decrease in solar radiation reaching
the earth's surface as compared with the top of the
atmosphere. The aerosols, typically in the submicrometer-
to micrometer-size range, were a mixture of sulfates,
nitrates, organic particles, fly ash and mineral dust,
formed by fossil fuel combustion and rural biomass
burning.
"One of the key revelations from INDOEX is that air
pollution is not only an industrial phenomenon," said
Crutzen. "The part of the atmosphere that you would
expect to be the cleanest -- areas without a lot of
industrialization -- in fact can be very highly polluted,
especially during the dry season."
In the Science paper, Ramanathan, Crutzen, J.T.
Kiehl (National Center for Atmospheric Research, Boulder,
Colorado), and Daniel Rosenfeld (The Hebrew University
of Jerusalem), say the aerosol issues raised from
INDOEX are a "major environmental concern."
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