The Indian Ocean brown cloud or Asian brown cloud is a layer of
air pollution
Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different type ...
that recurrently covers parts of
South Asia
South Asia is the southern subregion of Asia, which is defined in both geographical and ethno-cultural terms. The region consists of the countries of Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka.;;;;; ...
, namely the northern
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by ...
,
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
, and
Pakistan
Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...
. Viewed from
satellite photos, the cloud appears as a giant brown stain hanging in the air over much of South Asia and the Indian Ocean every year between January and March, possibly also during earlier and later months. The term was coined in reports from the UNEP
Indian Ocean Experiment (INDOEX). It was found to originate mostly due to Sikh farmers burning stubble in Punjab and to lesser extent Haryana. The debilitating air quality in Delhi is also due to the stubble burning in Punjab.
[Ramanathan, Veerabhadran ''et al.'' (2002]
''The Asian brown cloud climate and other environmental impacts: impact study''
Center for Clouds, Chemistry and Climate, United Nations Environment Programme, Nairobi Kenya, , accessed 8 December 2008
The term ''atmospheric brown cloud'' is used for a more generic context not specific to the Asian region.
Causes
The Asian brown cloud is created by a range of airborne particles and pollutants from combustion (e.g., woodfires, cars, and factories),
biomass burning
and industrial processes with incomplete burning. The cloud is associated with the winter
monsoon
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
(November/December to April) during which there is no rain to wash pollutants from the air.
[Petit, C. W. (2003) "A darkening sky: A smoky shroud over Asia blocks both sun and rain" ''U.S. News & World Report'' (17 March 2003), 134(8): pp. 46-8]
Observations
This pollution layer was observed during the Indian Ocean Experiment (INDOEX) intensive field observation in 1999 and described in the UNEP impact assessment study published 2002.
Scientists in India claimed that the Asian Brown cloud is not something specific to Asia.
Subsequently, when the
United Nations Environment Programme
The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
(UNEP) organized a follow-up international project, the subject of study was renamed ''the Atmospheric Brown Cloud'' with focus on Asia.
The cloud was also reported by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeedin ...
in 2004 and 2007.
Although aerosol particles are generally associated with a
global cooling effect, recent studies have shown that they can actually have a warming effect in certain regions such as the
Himalayas
The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 10 ...
.
Impacts
Health problems
One major impact is on
health
Health, according to the World Health Organization, is "a state of complete physical, mental and social well-being and not merely the absence of disease and infirmity".World Health Organization. (2006)''Constitution of the World Health Organ ...
. A 2002 study indicated nearly two million people die each year, in Asia alone, from conditions related to the brown cloud.
Regional weather
A second assessment study was published in 2008. It highlighted regional concerns regarding:
* Changes of rainfall patterns with the Asian
monsoon
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
, as well as a delaying of the start of the Asian monsoon, by several weeks. The observed weakening Indian monsoon and in China northern drought and southern flooding is influenced by the clouds.
* Increase in rainfall over the
Australia
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
n
Top End and
Kimberley regions. A
CSIRO study has found that by displacing the
thermal equator southwards via cooling of the air over East Asia, the
monsoon
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
which brings most of the rain to these regions has been intensified and displaced southward.
* Retreat of the
Hindu Kush-
Himalayan glaciers and snow packs. The cause is attributed to rising air temperatures that are more pronounced in elevated regions, a combined warming effect of greenhouse gases and the Asian Brown Cloud. Also
deposition
Deposition may refer to:
* Deposition (law), taking testimony outside of court
* Deposition (politics), the removal of a person of authority from political power
* Deposition (university), a widespread initiation ritual for new students practiced f ...
of
black carbon decreases
the reflection and exacerbates the retreat. Asian glacial melting could lead to water shortages and floods for the hundreds of millions of people who live downstream.
* Decrease of crop harvests. Elevated concentrations of
surface ozone are likely to affect crop yields negatively. The impact is crop specific.
Cyclone intensity in Arabian Sea
A 2011 study found that pollution is making
Arabian Sea
The Arabian Sea ( ar, اَلْبَحرْ ٱلْعَرَبِيُّ, Al-Bahr al-ˁArabī) is a region of the northern Indian Ocean bounded on the north by Pakistan, Iran and the Gulf of Oman, on the west by the Gulf of Aden, Guardafui Channe ...
cyclones more intense as the atmospheric brown clouds has been producing weakening wind patterns which prevent wind shear patterns that historically have prohibited cyclones in the Arabian Sea from becoming major storms. This phenomenon was found responsible for the formation of stronger storms in
2007 and
2010 that were the first recorded storms to enter the
Gulf of Oman.
Global warming and dimming
The 2008 report also addressed the global concern of
warming and concluded that the brown clouds have masked 20 to 80 percent of
greenhouse gas forcing in the past century. The report suggested that air pollution regulations can have large amplifying effects on global warming.
Another major impact is on the polar ice caps.
Black carbon (
soot) in the Asian Brown Cloud may be reflecting sunlight and dimming Earth below but it is warming other places by absorbing incoming radiation and warming the atmosphere and whatever it touches. Black carbon is three times more effective than carbon dioxide—the most common greenhouse gas—at melting polar ice and snow. Black carbon in snow causes about three times the temperature change as carbon dioxide in the atmosphere. On snow—even at concentrations below five parts per billion–dark carbon triggers melting, and may be responsible for as much as 94 percent of Arctic warming.
See also
*
Asian Dust
*
Arctic haze
*
Air pollution in India
*
Chemical Equator
The chemical equator term and concept was coined in 2008 when researchers from University of York discovered a distinct divide between the polluted air and haze over Indonesia from the largely uncontaminated atmosphere over Australia. This divide ...
*
1997
File:1997 Events Collage.png, From left, clockwise: The movie set of ''Titanic'', the highest-grossing movie in history at the time; '' Harry Potter and the Philosopher's Stone'', is published; Comet Hale-Bopp passes by Earth and becomes one of ...
,
2006,
2009,
2013 Southeast Asian haze
References
Further reading
*
* Silva-Send, Nilmini (2007) ''Preventing regional air pollution in Asia : the potential role of the European Convention on Long Range Transboundary Air Pollution in Asian regions''
University of Kiel, Kiel, Germany,
External links
Bray, Marianne (2002) "'Asian Brown Cloud' poses global threat" CNN from WebArchive
{{DEFAULTSORT:Asian Brown Cloud
Air pollution by region
Climate of India
Climate of Pakistan
Indian Ocean
Meteorology research and field projects
Smog events
South Asia
Air pollution in India