Project
Atmospheric Brown Clouds
Project
Atmospheric Brown Clouds (ABC) was created to
study brown clouds and their human impacts under the sponsorship
of the United Nations Environmental Program (UNEP),The scientific
team is led by Professors V.
Ramanathan and Paul
Crutzen of the Center
for Clouds, Chemistry, and Climate at the Scripps Institution of Oceanography.
IGCC collaborated with
the Center for Clouds, Chemistry, and Climate on a
study of the impacts of brown clouds
on rice output in the Indian subcontinent.
The
initial focus of Project ABC is Asia, where
over 50 percent of the world’s population lives
and where industrial and demographic growth rates are
high. A primary thrust of Project ABC is to assess the
impact of brown clouds on the Asian monsoon, which brings
live-giving rainfall to the region. Recently, evidence
has emerged that an immense and persistent cloud of
aerosol pollution has already
affected temperature, precipitation, and solar radiation
in the region.
In early 1999, more than 200 scientists from India, the
United States, and Europe gathered in the Maldives to
conduct the Indian Ocean Experiment (INDOEX). INDOEX
revealed an immense “brown cloud” over the
Northern Indian Ocean. Unlike regular clouds, which
are made up of water vapor, brown clouds are mostly
made up of miniscule particles called aerosols, which
consist of sulfates, nitrates, black carbon, fly ash,
and hundreds of organic compounds. A fundamental message
from INDOEX is that due to long-range transport, what
we normally associate with urban haze can span an entire
subcontinent plus an ocean basin. Brown clouds have
subsequently been found in other regions.
Brown clouds absorb solar energy. In so doing, they
reduce the amount that reaches the earth’s surface,
and they heat up the atmosphere. As the atmosphere heats
up, the amount of rainfall in a region is decreased.
While the greenhouse effect is the major issue for global
climate change, brown clouds are emerging as a major
factor in regional climate change and in reductions
of regional rainfall, especially in tropical regions.
Brown clouds are so large in the tropics for two main
reasons. One is the large increase in emissions of aerosols
and their precursors that has occurred in developing
countries. The other is the unique meteorology of the
tropics and the subtropics.
IGCC researchers
included Prof. Max
Auffhammer (Department of Agricultural
and Resource Economics, UC Berkeley) and IGCC Environmental
Research Director Prof. Jeffrey
R. Vincent. They presented
preliminary results at a Project
ABC workshop in April
2005 and will present updated results at the next
project workshop in December 2005. Results so far
suggest
that brown clouds have contributed to the stagnation
of rice output that has occurred in the region during
the past 10–15 years.
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