View source for Asian brown cloud

{{about|the Indian Ocean brown cloud|China|Air pollution in China}}
[[File:China.A2004040.0245.250m.jpg|thumb|Atmospheric Brown Cloud over China]]
[[File:Giant Brown Cloud Storm over Asia (NASA).jpg|thumb|Big Brown Cloud Storm over Asia]]
The '''Indian Ocean brown cloud''' or '''Asian brown cloud''' is a layer of [[air pollution]] that recurrently covers parts of [[South Asia]], namely the northern [[Indian Ocean]], [[India]], and [[Pakistan]].<ref>{{cite journal
 |last=Srinivasan 
 |title=Asian Brown Cloud – fact and fantasy 
 |journal=Current Science 
 |volume=83 
 |issue=5 
 |url=http://www.ias.ac.in/currsci/sep102002/586.pdf 
 |archive-url=https://web.archive.org/web/20041105023244/http://www.ias.ac.in/currsci/sep102002/586.pdf 
 |url-status=dead 
 |archive-date=5 November 2004 
 |date=10 September 2002 
 |pages=586–592 
}}</ref><ref>{{cite journal
|last1=Ramanathan
|first1=Veerabhadran
|author-link=Veerabhadran Ramanathan
|title=Indian Ocean experiment: An integrated analysis of the climate forcing and effects of the great Indo-Asian haze
|journal=Journal of Geophysical Research
|volume=106|issue=D22
|year=2001|pages=28371–28398
|doi=10.1029/2001JD900133
|last2=Crutzen
|first2=P. J.
|last3=Lelieveld
|first3=J.
|last4=Mitra
|first4=A. P.
|last5=Althausen
|first5=D.
|last6=Anderson
|first6=J.
|last7=Andreae
|first7=M. O.
|last8=Cantrell
|first8=W.
|last9=Cass
|first9=G. R.
|last10=Chung
|first10=C. E.
|last11=Clarke
|first11=A. D.
|last12=Coakley
|first12=J. A.
|last13=Collins
|first13=W. D.
|last14=Conant
|first14=W. C.
|last15=Dulac
|first15=F.
|last16=Heintzenberg
|first16=J.
|last17=Heymsfield
|first17=A. J.
|last18=Holben
|first18=B.
|last19=Howell
|first19=S.
|last20=Hudson
|first20=J.
|last21=Jayaraman
|first21=A.
|last22=Kiehl
|first22=J. T.
|last23=Krishnamurti
|first23=T. N.
|last24=Lubin
|first24=D.
|last25=McFarquhar
|first25=G.
|last26=Novakov
|first26=T.
|last27=Ogren
|first27=J. A.
|last28=Podgorny
|first28=I. A.
|last29=Prather
|first29=K.
|last30=Priestley
|first30=K.
|bibcode=2001JGR...10628371R|display-authors=8
|doi-access=free
}}</ref> Viewed from [[satellite photo]]s, 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).<ref name="Ramanathan-2002">Ramanathan, Veerabhadran ''et al.'' (2002) [http://www.rrcap.unep.org/issues/air/impactstudy/index.cfm ''The Asian brown cloud climate and other environmental impacts: impact study''] {{webarchive |url=https://web.archive.org/web/20040605194625/http://www.rrcap.unep.org/issues/air/impactstudy/index.cfm |date=June 5, 2004 }} Center for Clouds, Chemistry and Climate, United Nations Environment Programme, Nairobi Kenya, {{ISBN|92-807-2240-9}}, accessed 8 December 2008</ref>

The term ''atmospheric brown cloud'' is used for a more generic context not specific to the Asian region.<ref>{{cite journal |last=Haag |first=Amanda Leigh|date=2007 |title=The even darker side of brown clouds |url=http://www.nature.com/climate/2007/0709/full/climate.2007.41.html |journal=Nature Reports Climate Change|volume=1|issue=709|pages=52–53|doi=10.1038/climate.2007.41 |access-date=16 September 2014}}</ref>

==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<ref name="Gustafsson-09">{{cite journal |last1=Gustafsson |first1=Örjan |last2=Kruså |first2=Martin |last3=Zencak |first3=Zdenek |last4=Sheesley |first4=R. J. |last5=Granat |first5=Lennart |last6=Engström |first6=Erik |last7=Praveen |first7=P. S. |last8=Rao |first8=P. S. P. |last9=Leck |first9=Caroline |last10=Rodhe |first10=Henning |year=2009 |title=Brown Clouds over South Asia: Biomass or Fossil Fuel Combustion? |journal=[[Science (journal)|Science]] |volume=323 |issue= 5913|pages=495–498 |doi=10.1126/science.1164857 |pmid=19164746|bibcode = 2009Sci...323..495G |s2cid=44712883 |display-authors=etal}}</ref> and industrial processes with incomplete burning.<ref>{{cite journal|last=Taylor|first=David|title=The ABCs of Haze|journal=[[Environmental Health Perspectives]] |volume=111|issue=1|archive-url=https://web.archive.org/web/20060828001357/http://www.ehponline.org/docs/2003/111-1/forum.html#thea|archive-date=2006-08-28|url=http://www.ehponline.org/docs/2003/111-1/forum.html#thea|date=1 January 2003|pages=A21–A22|doi=10.1289/ehp.111-a21a|pmc=1241333}}</ref> The cloud is associated with the winter [[monsoon]] (November/December to April) during which there is no rain to wash pollutants from the air.<ref name="Petit">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</ref>

==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.<ref name="Ramanathan-2002"/> Scientists in India claimed that the Asian Brown cloud is not something specific to Asia.<ref>{{cite journal | url = http://www.ijoem.com/article.asp?issn=0019-5278;year=2008;volume=12;issue=2;spage=93;epage=95;aulast=Pandve | last = Pandve | first = Harshal T. | title = The Asian Brown Cloud | access-date = 8 December 2008 | pmid = 20040987 | journal =  Indian Journal of Occupational and Environmental Medicine| year = 2008 | volume = 12 | issue = 2 | pages = 93–5 | doi = 10.4103/0019-5278.43269 | pmc = 2796752 | archive-url = https://web.archive.org/web/20090224215327/http://www.ijoem.com/article.asp?issn=0019-5278;year=2008;volume=12;issue=2;spage=93;epage=95;aulast=Pandve | archive-date = 24 February 2009 | url-status = dead }}</ref> 
Subsequently, when the [[United Nations Environment Programme]] (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]] in 2004<ref>[http://www.nasa.gov/vision/earth/environment/brown_cloud.html NASA Eyes Effects of a Giant 'Brown Cloud' Worldwide (2004)]</ref> and 2007.<ref>[http://earthobservatory.nasa.gov/IOTD/view.php?id=8857 Global Aerosol System 2000-2007 (NASA Earth Observatory)]</ref>

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]].<ref>{{cite journal
|last1=Ramanathan
|first1=Veerabhadran
|title=Warming trends in Asia amplified by brown cloud solar absorption
|journal=[[Nature (journal)|Nature]]|volume=448
|doi= 10.1038/nature06019
|date=2 August 2007|pages=575–578
|pmid=17671499
|last2=Ramana
|first2=MV
|last3=Roberts
|first3=G
|last4=Kim
|first4=D
|last5=Corrigan
|first5=C
|last6=Chung
|first6=C
|last7=Winker
|first7=D
|issue=7153|bibcode = 2007Natur.448..575R |s2cid=4420513
}}</ref>

==Impacts==

===Health problems===
One major impact is on [[health]]. A 2002 study indicated nearly two million people die each year, in Asia alone, from conditions related to the brown cloud.<ref>{{cite journal |last=Ahmad |first=K. |title=Pollution cloud over south Asia is increasing ill health |journal=[[Lancet (journal)|Lancet]] |year=2002 |volume=360 |issue=9332 |pages=549 |doi=10.1016/S0140-6736(02)09762-3 |pmid=12241664 |s2cid=35909421 }}</ref>

===Regional weather===
A second assessment study was published in 2008.<ref>{{Cite web |url=http://www.unep.org/pdf/ABCSummaryFinal.pdf |title=Archived copy |access-date=2008-11-18 |archive-url=http://webarchive.loc.gov/all/20081118220650/http://www.unep.org/pdf/ABCSummaryFinal.pdf |archive-date=2008-11-18 |url-status=bot: unknown }}</ref> It highlighted regional concerns regarding:
* Changes of rainfall patterns with the Asian [[monsoon]], as well as a delaying of the start of the Asian monsoon, by several weeks.<ref>[http://www.nepalitimes.com/news.php?id=15452 Brown cloud delaying monsoon].</ref><ref>[http://zc.iap.ac.cn/uploadpdf/tac2012_Rashed_Li_BC.pdf Paper reporting the delaying of the monsoon being caused by brown cloud]{{Dead link|date=October 2016 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> The observed weakening Indian monsoon and in China northern drought and southern flooding is influenced by the clouds.
* Increase in rainfall over the [[Australia]]n [[Top End]] and [[Kimberley (Western Australia)|Kimberley]] regions. A [[CSIRO]] study has found that by displacing the [[thermal equator]] southwards via cooling of the air over East Asia, the [[monsoon]] which brings most of the rain to these regions has been intensified and displaced southward.<ref>{{cite journal|last1=Rotstayn|first1=Leon|title=Have Australian rainfall and cloudiness increased due to the remote effects of Asian anthropogenic aerosols?|journal=Journal of Geophysical Research|volume=112|issue=D09202|archive-url=https://web.archive.org/web/20070930184533/http://www.agu.org/pubs/crossref/2007/2006JD007712.shtml|archive-date=2007-09-30|url=http://www.agu.org/pubs/crossref/2007/2006JD007712.shtml|date=2 May 2007|doi=10.1029/2006JD007712|pages=D09202|last2=Cai|first2=Wenju|last3=Dix|first3=Martin R.|last4=Farquhar|first4=Graham D.|last5=Feng|first5=Yan|last6=Ginoux|first6=Paul|last7=Herzog|first7=Michael|last8=Ito|first8=Akinori|last9=Penner|first9=Joyce E.|last10=Roderick|first10=Michael L.|last11=Wang|first11=Minghuai|bibcode=2007JGRD..11209202R|display-authors=8|hdl=2027.42/94749|hdl-access=free}}</ref>
* Retreat of the [[List of glaciers of Pakistan|Hindu Kush]]-[[List of glaciers of India|Himalaya]]n 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 (Aerosol physics)|deposition]] of [[black carbon]] decreases [[albedo|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 [[smog|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]] 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 [[Cyclone Gonu|2007]] and [[Cyclone Phet|2010]] that were the first recorded storms to enter the [[Gulf of Oman]].<ref>{{cite web|url=https://www.nsf.gov/news/news_summ.jsp?cntn_id=122072&WT.mc_id=USNSF_51&WT.mc_ev=click|title=Link Between Air Pollution and Cyclone Intensity in Arabian Sea |publisher=[[National Science Foundation]]|date=2011-11-02|access-date=2011-11-07}}</ref><ref>{{cite journal|title=Arabian Sea tropical cyclones intensified by emissions of black carbon and other aerosols |first1=Amato T.|last1= Evan|first2=James P.|last2=Kossin|first3=Chul|last3=Chung|first4=V.|last4=Ramanathan|journal=Nature|issue=7371|pages=94–97 |date=2011-11-03|doi=10.1038/nature10552 |pmid=22051678 |volume=479|bibcode = 2011Natur.479...94E |s2cid=4423931}}</ref>

===Global warming and dimming===
The 2008 report also addressed the global concern of [[global warming|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.<ref>{{cite journal|last=Biello|first=David|title=Brown Haze from Cooking Fires Cooking EarthToo.The brown haze over Asia warms the atmosphere just as much as greenhouse gases.|journal= Scientific American|url=http://www.scientificamerican.com/article.cfm?id=brown-haze-from-cooking-fires-cooking-earth|date= August 1, 2007}}</ref> Black carbon is three times more effective than carbon dioxide—the most common greenhouse gas—at melting polar ice and snow.<ref>{{cite journal|last=Biello|first=David|title= Impure as the Driven Snow: Smut is a bigger problem than greenhouse gases in polar meltdown.|journal= Scientific American|url= http://www.scientificamerican.com/article.cfm?id=impure-as-the-driven-snow|date= June 8, 2007}}</ref> 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.<ref>{{cite journal|last=Boswell |first=Randy |title=Burning crops darken Arctic sky, speed polar melt. |journal=Canwest News Service |url=http://www.canada.com/technology/Burning+crops+darken+Arctic+speed+polar+melt/1635692/story.html |archive-url=https://web.archive.org/web/20100206215104/http://www.canada.com/technology/Burning%2Bcrops%2Bdarken%2BArctic%2Bspeed%2Bpolar%2Bmelt/1635692/story.html |url-status=dead |archive-date=February 6, 2010 |date=October 19, 2009 }}</ref>

==See also==
{{portal|Global warming|Environment}}
* [[Asian Dust]]
* [[Arctic haze]]
* [[Air pollution in India]]
* [[1997 Southeast Asian haze|1997]], [[2006 Southeast Asian haze|2006]], [[2009 Southeast Asian haze|2009]], [[2013 Southeast Asian haze]]

==References==
{{Reflist|30em}}

==Further reading==
* {{Cite journal | doi = 10.1016/S1352-2310(03)00536-3 | last1 = Ramanathan | first1 = V. | last2 = Crutzen | first2 = P. J. | year = 2003 | title = New Directions: Atmospheric Brown "Clouds" | journal = Atmospheric Environment | volume = 37 | issue = 28| pages = 4033–4035 |bibcode = 2003AtmEn..37.4033R }}
* 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, {{OCLC|262737812}}

==External links==
* [https://web.archive.org/web/20071009231830/http://archives.cnn.com/2002/WORLD/asiapcf/south/08/12/asia.haze/ Bray, Marianne (2002) "'Asian Brown Cloud' poses global threat" CNN], from WebArchive

{{Asia Pollution}}

{{DEFAULTSORT:Asian Brown Cloud}}
[[Category:Air pollution by region]]
[[Category:Climate of India]]
[[Category:Climate of Pakistan]]
[[Category:Indian Ocean]]
[[Category:Meteorology research and field projects]]
[[Category:Smog events]]
[[Category:South Asia]]
[[Category:Air pollution in India]]