- Sahel drought
Saheldrought from the late 1960s to early 1980s created a faminethat killed a million people and afflicted more than 50 million.Fact|date=September 2008 The economies, agriculture, livestock and human populations of much of Mauritania, Mali, Chad, Nigerand Burkina Faso(known as Upper Volta during the time of the drought) were severely impacted.
Previous Sahel droughts
Because the Sahel's rainfall is heavily concentrated in a very small period of the year, the region has been prone to droughts ever since
agriculturedeveloped around 5,000 years ago.
Records of climate in the Sahel begin with early
Muslimtravellers in the early Medieval Warm Period. These suggest that Sahel rainfall was relatively low in the seventh and eighth centuries and then increased substantially from about 800 AD.cite book |title=Eaters of the Dry Season: Circular Labor Migration in the West African Sahel |last=Rain |first=David |authorlink= |coauthors= |year=1999 |publisher=Westview Press |location=Boulder, CO |isbn=0813338727 |pages=p. 77 ] There was a decline in rainfall from about 1300 AD, but an increase again around 200 years later.
The first major reported
droughtin the Sahel occurred around 1640, and a major drought after generally wet conditions occurred, based on the reports of European travellers, [cite web |url=http://www.greenstone.org/greenstone3/nzdl;jsessionid=1AB0DFF58D047EC9E8B55C523A65856F?a=d&d=HASH99771026b305b974da2200.7&c=envl&sib=1&dt=&ec=&et=&p.a=b&p.s=ClassifierBrowse&p.sa= |title=Climate and Man in the Sahel during the Historical Period |accessdate=2008-06-19 |work=World Environmental Library |date= ] during the 1680s. This cycle of several wet decades followed by a drought was repeated during the 18th century, [ [http://ag.arizona.edu/~lmilich/desclim.html Len Milich: Anthropogenic Desertification vs ‘Natural’ Climate Trends] ] but around 1790 dry conditions similar to those of the late twentieth century set in and continued until around 1870. After that, a very wet period set in for around 25 years, followed by a return to drier conditions.
The first rain gauges in the Sahel date from 1898 and they reveal that a major drought, accompanied by large-scale famine, in the 1910s, followed by wet conditions during the 1920s and 1930s reaching a peak with the very wet year of 1936. The 1940s saw several minor droughts — notably in 1949 — but the 1950s were consistently wet and expansion of agriculture to feed growing populations characterised this decade and many have thought it contributed to the severity of the subsequent Sahel drought.
Potential factors contributing to Sahel drought
Originally it was believed that the drought in the Sahel primarily was caused by humans over-using natural resources in the region through
overgrazing, deforestationand poor land management. [ [http://www.eden-foundation.org/project/desertif.html "Desertification - a threat to the Sahel", August 1994] ] [ [http://www.csmonitor.com/2005/0801/p01s02-woaf.html Hunger is spreading in Africa] ] In the late 1990s,Fact|date=August 2008 climate model studies suggested that large scale climate changes were also triggers for the drought.
In the early 2000s, after the phenomenon of
global dimmingwas discovered, some speculatively suggestedFact|date=August 2008 that the drought was likely caused by air pollution generated in Eurasia and North America. The pollution changed the properties of clouds over the Atlantic ocean, disturbing the monsoons and shifting the tropical rains southwards.
In 2005, a series of climate modeling studies performed at
NOAA/ Geophysical Fluid Dynamics Laboratoryindicated that the late 20th century Sahel drought was likely a climatic response to changing sea surface temperature patterns, and that it could be viewed as a combination of natural variability superimposed upon an anthropogenically forced regional drying trend. [cite journal |last=Held |first=I. M. |authorlink= |coauthors="et al." |year=2005 |month= |title=Simulation of Sahel drought in the 20th and 21st centuries |journal=PNAS |volume=102 |issue=50 |pages=17891–17896 |doi=10.1073/pnas.0509057102 |url= |accessdate= |quote=|pmid=16322101 ] These climate model simulations indicated that the general late 20th century Sahel drying trend was attributable to human-induced factors; largely due to an increase in greenhouse gasesand partly due to an increase in atmospheric aerosols. These climate changemodeling studies also project that human-induced climate change could lead to a 25% reduction in Sahel rainfall by year 2100.
A 2006 study by NOAA scientists Rong Zhang and Thomas L. Delworth suggests that the
Atlantic Multidecadal Oscillationplays a leading role. An AMO warm phase strengthens the summer rainfall over Sahel, while a cold phase reduces it.cite journal |last=Zhang |first=Rong |authorlink= |coauthors=Delworth, Thomas L. |year=2006 |month= |title=Impact of Atlantic multidecadal oscillations on India/Sahel rainfall and Atlantic hurricanes |journal=Geophysical Research Letters |volume=33 |issue= |pages=L17712 |doi=10.1029/2006GL026267 |url= |accessdate= |quote= ]
United Nations Sahel drought response
In 1973, The United Nations Sahelian Office (UNSO) was created to address the problems of drought in the Sahel region following the West African Sahel drought of 1968-73. In the 1990s, the
United Nations Convention to Combat Desertification(UNCCD) was adopted and UNSO became the United Nations Development Programme's Office to Combat Desertification and Drought, as its scope broadened to be global rather than only focused on Africa. [ [http://www.undp.org/drylands/history.html UNDP | Drylands Development Centre ] ]
2005–06 Niger food crisis
*cite journal |last=Folland |first=C. K. |authorlink= |coauthors=Palmer, T. N.; Parker, D. E. |year=1986 |month= |title=Sahel rainfall and worldwide sea temperatures, 1901−85 |journal=Nature |volume=320 |issue=6063 |pages=602–607 |doi=10.1038/320602a0 |url= |accessdate= |quote=
*cite journal |last=Giannini |first=A. |authorlink= |coauthors=Saravanan, R.; Chang, P. |year=2003 |month= |title=Oceanic Forcing of Sahel Rainfall on Interannual to Interdecadal Time Scales |journal=Science |volume=302 |issue=5647 |pages=1027–1030 |doi=10.1126/science.1089357 |url= |accessdate= |quote=|pmid=14551320
* [http://www.unccd.int/ United Nations Convention to Combat Desertification home page]
* Climate research summary - [http://www.gfdl.noaa.gov/research/climate/highlights/index.html#sahel Sahel drought: past problems, an uncertain future] Text, graphics and [http://www.gfdl.noaa.gov/research/climate/highlights/images/ani/SahelPR_ANN5yr_CM2Q_h1_A1B_6fps_720x480.mov animations] from
NOAA/ Geophysical Fluid Dynamics Laboratory
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