Atmospheric Brown Cloud
Watch: http://www.youtube.com/watch?v=qYYK-2sDN4U
The first fully-researched and detailed report on the environmental impact of South Asian
Haze was released by UNEP and the Center for Clouds, Chemistry and Climate (C4) in
August 2002. The report is mainly based on the studies of the Indian Ocean Experiment
(INDOEX) and its team of 200 scientists. It provides a summary of the large brownish
haze layer and its impact on the radioactive heating of the atmosphere and surface for
South Asia and the Indian Ocean. It also discusses early findings with respect to the
effects of the haze on regional temperatures, rainfall, agriculture and health.
Findings are based on limited sets of modeling studies. Because definitive conclusions
cannot yet be drawn, these studies emphasize the importance of the haze on climate and
the great need for further research into the problem of brown haze.
Quick facts
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brown haze extends over South, Southeast and East Asia
haze is concentrated 3 kilometers above the surface and can travel halfway
around the globe in less than a week
large earth surface cooling due to reduced sunlight throws off the hydrological
cycle
What is in the Brown Haze?
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black carbon and ash
sulfates
nitrates
mineral dust
75% of the cloud is man-made
Causes
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forest fires
inefficient cooking fuels
factories
motor vehicle use
Effects
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significant reduction of solar radiation to the earth’s surface by as much as 15%
changed regional monsoon patterns (less sea evaporation from sunlight means
less rain)
less rain in northwest India, Pakistan, and Afghanistan by as much as 40%
more rain and flooding in other areas
reduction of photosynthesis (drop in agricultural productivity)
acid rain and plant damage
breathing problems and diseases
Source: UNEP and C4. The Asian Brown Cloud: Climate and Other Environmental Impacts
UNEP, Nairobi
Giant Atmospheric Brown Cloud Has Intercontinental Reach
NASA scientists announced a giant, smoggy atmospheric brown cloud, which forms over South Asia
and the Indian Ocean, has intercontinental reach. The scientists presented their findings today during
the American Geophysical Union Fall meeting in San Francisco.
The scientists discussed the massive cloud's sources, global movement and its implications. The brown cloud is
a moving, persistent air mass characterized by a mixed-particle haze. It also contains other pollution, such as
ozone.
"Ozone is a triple-threat player in the global environment. There are three very different ways ozone affects our
lives," said Robert Chatfield, a scientist at NASA's Ames Research Center, Moffett Field, Calif. "A protective
layer of good ozone, high in the atmosphere, shields us from deadly ultraviolet light that comes from the sun.
Second, bad or smog ozone near the surface of Earth can burn our lungs and damage crops. In our study, we are
looking at a third major effect of ozone, that it can warm the planet, because it is a powerful greenhouse gas,"
Chatfield said.
"We found both brown cloud pollution and natural processes can contribute to unhealthy levels of ozone in the
troposphere where we live and breathe. Some ozone from the brown cloud rises to high enough altitudes to
spread over the global atmosphere," Chatfield explained. Ozone from the Earth's protective stratospheric layer,
produced by natural processes, can migrate down to contribute to concentrations in the lower atmosphere,
according to the scientists.
The researchers studied the intercontinental smog ozone processes associated with the brown cloud over South
Asia. They used a NASA technique that combines data acquired by satellites with ozone data measured by
instruments on special weather balloons.
The ozone-monitoring instrument on NASA's Aura satellite is providing data about the brown cloud. "The
beautiful, high-detail images from this instrument promise to help us sort out our major questions about how
much of the tropospheric ozone is from pollution and how much is from natural factors," Chatfield said.
Analysis shows ozone in the lower atmosphere over the Indian Ocean comes from the intensely developed
industrial-agricultural areas in the region. The southern pollutant buildup has long-range effects, often traveling
across Africa, further than the brown cloud of particles, according to researchers.
Massive Pollution Documented Over Indian Ocean
An international group of scientists participating in a climate field experiment has documented
widespread pollution covering about 10 million square kilometers of the tropical Indian Ocean -roughly the same area as the continental United States. The finding raises serious questions about
what impact the extensive pollution is having on climate processes and on marine life in the ocean
below.
The scientists are participating in the Indian Ocean Experiment (INDOEX), a $25 million project, sponsored in
part by the National Science Foundation, to investigate how tiny pollutant particles called aerosols are
transported through the atmosphere and their effect on climate. The team of scientists was shocked by the extent
of pollution they encountered during the six-week field experiment that began in early February and continued
through the end of March 1999. "There was a brownish haze layer all over the Indian Ocean almost 1,000 miles
off the coast," he said. "That was what really stunned us -- how pervasive these aerosols were and how they
could survive at such long distances from where they originated." The INDOEX scientists reported finding a
dense, brown haze of pollution extending from the ocean surface to altitudes of 2 miles in the air.
The haze layer covered much of the research area almost continually during the six-week experiment. The
affected area includes most of the northern Indian Ocean, including the Arabian Sea, much of the Bay of
Bengal, and spills over into the equatorial Indian Ocean to about 5 degrees south of the equator. "It appeared as
if the whole Indian subcontinent was surrounded by a mountain of pollution," agreed Ramanathan. "At times,
we couldn't even see the low clouds because the haze layer was so thick."
The haze is caused by high concentrations of small particles known as aerosols that are usually less than a few
micrometers in diameter. Comprised primarily of soot, sulfates, nitrates, organic particles, fly ash and mineral
dust, the particles often reduced visibility over the open ocean. The haze layer also contains relatively high
concentrations of gases, including carbon monoxide, various organic compounds, and sulfur dioxide, providing
conclusive evidence that the haze layer is caused by pollution. "There is little doubt that future levels of
pollution from India and other nations bordering on the Indian Ocean region are going to grow substantially in
the future.
Asia and the Indian subcontinent, which together have a population of more than 2 billion people, emit large
quantities of pollutants that can be carried to the Indian Ocean during the northern hemisphere winter by
monsoon winds from the northeast. "If you cut the amount of sunlight going into the ocean, you will also impact
the amount of moisture evaporating from the sea surface either regionally or globally and, consequently, the
amount of rainfall that will be generated," Ramanathan said. "So the entire hydrological cycle is being
perturbed."
A reduction in the amount of sunlight reaching the ocean surface can also have a detrimental effect on plant life
that depends on photosynthesis, including plankton, which provides a key link in the marine food chain. Early
results indicate that the pollutants play a dual role in that they have both warming and cooling effects. The tiny
particles produce a cooling effect in that they scatter sunlight back to space. By acting as seeds for cloud
condensation, they also produce an indirect cooling effect by increasing both the longevity and reflectivity, or
albedo, of clouds. The pollutants have a warming effect, however, in that they absorb a large amount of sunlight.
The airborne particles over the northern Indian Ocean are unusually dark because they contain large amounts of
soot and other materials from incompletely burned fuels and wastes. Dark aerosols lead to the increased
absorption of solar radiation.
"The soot contributes a substantial amount of heating of the atmosphere, but it also reduces the amount of
sunlight reaching the ocean," Ramanathan said. "So, it is just too early to say at this point whether the net effect
is one of cooling or warming." The dark airborne particles over the Indian Ocean appear to be markedly
different from those over North America and Europe, where advanced pollution control technologies remove
much of the dark material and yield particles that are relatively brighter. "What INDOEX has pointed out very
dramatically is that the long-range transport of aerosols can be extremely important and that we should be
looking more closely at what impact this is having on global climate."
Asia's brown clouds 'warm planet'
Clouds of pollution over the Indian Ocean appear to cause as much warming as greenhouse gases
released by human activity, a study has suggested.
US researchers used unmanned aircraft to measure the effects of the "brown clouds" on the surrounding
area.
Writing in Nature, they said the tiny particles increased the solar heating of the lower atmosphere by about
50%.
The warming could be enough to explain the retreat of glaciers in the Himalayas, the scientists proposed.
The clouds contain a mixture of light absorbing aerosols and light scattering aerosols, which cause the
atmosphere to warm and the surface of the Earth to cool.
The main sources of the pollutants came from wood burning and fossil fuels, the team added.
Aerosols, also known as particulates, cool the land or sea below because they filter out light from the Sun.
While this process, known as "global dimming", is fairly well understood, the effect aerosols have on the
surrounding atmosphere is still unclear.
The scientists, from the University of California San Diego and the Nasa Langley Research Center, said there
remained a degree of uncertainty because, until now, estimates had largely been derived from computer
models.
Solar heating
For their study, the team of researchers used three unmanned aircraft, fitted with miniaturised instruments
that were able to measure aerosol concentrations, soot amounts and the flow of energy from the Sun.
The crafts flew over the polluted region of the Indian Ocean at varying heights between 500m (1,640ft) and
3,000m (9,840ft).
"During 18 flight missions, the three unmanned aerial vehicles were flown with a separation of tens of
metres or less and less than 10 seconds (apart), which made it possible to measure the atmospheric solar
heating rates directly," they wrote.
"We found that atmospheric brown clouds enhanced lower atmospheric solar heating by about 50%.
"[The pollution] contributes as much as the recent increase in anthropogenic greenhouse gases to regional
lower atmospheric warming trends," they suggested.
"We propose that the combined warming trend of 0.25 Kelvin per decade may be sufficient to account for
the observed retreat of the Himalayan glaciers."
Seasonal glacier and snow melt from the mountain range feeds rivers that supplies water to about 40% of
the world's population.
The United Nations Environment Programme (Unep), in its latest Snow and Ice Outlook report, said the ice
sheets in the region could retreat by up to 81% by the end of the century.
Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/6926597.stm
Published: 2007/08/01 18:34:48 GMT © BBC MMVII
Asian Brown Cloud Activity
Essential Question: How have humans altered their environment?
The Asian Brown Cloud is a giant brown haze as large as a continent and 2 miles thick. It was created
from factory’s smoke, forest fires, automobiles and inefficient cooking fuel.
Task: Choose one of the activities below to demonstrate your knowledge of the “Asian Brown Cloud.”
1. Pretend that you are a student in India and make a poster to make people aware of the dangers
of the “Asian Brown Cloud” and how to help alleviate the problem.
2. Write a commercial that explains the dangers of the “Asian Brown Cloud”
3. Write a news article that illustrates a story of how someone or something has been affected by
the “Brown Cloud”
4. Write a letter to a public official and propose a law that will demand Indian citizens take action
to reduce the effects of the “Asian Brown Cloud”
5. Write a song that explains the dangers of the Asian “brown” cloud.
Asian Brown Cloud Rubric
1
2
3
4
Wrote the words Asian
“brown” cloud but do
not write any thing that
is true about the “Asian
Brown Cloud”.
Includes elements in the
definition that are
wrong.
Gives the basic
definition without
explaining the “Asian
Brown Cloud”.
Demonstrates a clear
understanding of the
“Asian Brown Cloud”.
Simply wrote one reason
why the “Asian Brown”
Cloud” exists.
Included some of the
definition but also
concluded false reasons
why the Asian Brown”
Cloud” exists.
Gave the basic reasons
why the Asian “brown”
cloud exist that you
learned in the notes.
It is clear by the work of
what caused the “Asian
Brown Cloud”.
Attempted to explain
where the cloud is
located but got confused
and thought it was
coming to Woodland.
Only told part of the
location.
Copied the location
from the notes.
Utilized knowledge of
geography and
explained where the
“Asian Brown Cloud” is
located.
Explained fictional
problems the “Asian
Brown Cloud” has
created.
Only explained part of
what the “Brown Cloud”
is doing to Asia.
Copied what was stated
in the notes.
The project exemplifies
the students
understanding of why
the “Brown Cloud” is so
dangerous.