Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Pollution in Northern Hemisphere helped cause 1980s African drought

07.06.2013
Decades of drought in central Africa reached their worst point in the 1980s, causing Lake Chad, a shallow lake used to water crops in neighboring countries, to almost dry out completely.
The shrinking lake and prolonged drought were initially blamed on overgrazing and bad agricultural practices. More recently, Lake Chad became an example of global warming.

New University of Washington research, to be published in Geophysical Research Letters, shows that the drought was caused at least in part by Northern Hemisphere air pollution.

Aerosols emanating from coal-burning factories in the United States and Europe during the 1960s, ’70s and ’80s cooled the entire Northern Hemisphere, shifting tropical rain bands south. Rains no longer reached the Sahel region, a band that spans the African continent just below the Sahara desert.

When clean-air legislation passed in the U.S. and Europe, the rain band shifted back, and the drought lessened.

Related research by the UW researchers and their collaborators shows that global warming is now causing the land-covered Northern Hemisphere to warm faster than the Southern Hemisphere, further reversing the pre-1980s trend.

Previous research has suggested a connection between coal-burning and the Sahel drought, but this was the first study that used decades of historical observations to find that this drought was part of a global shift in tropical rainfall, and then used multiple climate models to determine why.

“One of our research strategies is to zoom out,” said lead author Yen-Ting Hwang, a UW doctoral student in atmospheric sciences. “Instead of studying rainfall at a particular place, we try to look for the larger-scale patterns.”

To determine that the Sahel drought was part of a broader shift, the authors looked at precipitation from all rain gauges that had continuous readings between 1930 and 1990. Other places on the northern edge of the tropical rain band, including northern India and South America, also experienced dryer climates in the 1970s and ’80s. Meanwhile, places on the southern edge of the rain band, such as northeast Brazil and the African Great Lakes, were wetter than normal.

To understand the reason, authors looked at all 26 climate models used by the Intergovernmental Panel on Climate Change. Researchers discovered that almost all the models also showed some southward shift, and that cooling from sulfate aerosols in the Northern Hemisphere was the primary cause.

“We think people should know that these particles not only pollute air locally, but they also have these remote climate effects,” Hwang said.

Light-colored sulfate aerosols are emitted mainly by dirty burning of coal. They create hazy air that reflects sunlight, and also lead to more reflective, longer-lasting clouds.

People living in the Northern Hemisphere did not notice the cooling, the authors said, because it balanced the heating associated with the greenhouse effect from increased carbon dioxide, so temperatures were steady.

“To some extent, science messed this one up the first time around,” said co-author Dargan Frierson, a UW associate professor of atmospheric sciences. “People thought that a large part of that drought was due to bad farming practices and desertification. But over the last 20 years or so we’ve realized that that was quite wrong, and that large-scale ocean and atmosphere patterns are significantly more powerful in terms of shaping where the rains fall.”

The models did not show as strong a shift as the observations, Frierson said, suggesting that ocean circulation also played a role in the drought.

The good news is that the U.S. Clean Air Act and its European counterpart had an unintended positive effect beyond improved air quality and related health benefits. Although shorter-term droughts continue to affect the Sahel, the long-term drought began to recover in the 1980s.

“We were able to do something that was good for us, and it also benefited people elsewhere,” Frierson said.

The work was funded by the National Science Foundation. Sarah Kang at the Ulsan National Institute of Science and Technology in South Korea was a co-author.

For more information, contact Hwang at 206-543-0333 or yting@atmos.washington.edu and Frierson at 206-685-7364 or dargan@atmos.washington.edu

Hannah Hickey | EurekAlert!
Further information:
http://www.uw.edu
http://www.washington.edu/news/2013/06/06/pollution-in-northern-hemisphere-helped-cause-1980s-african-drought/

More articles from Earth Sciences:

nachricht A damming trend
17.12.2018 | Michigan State University

nachricht Live from the ocean research vessel Atlantis
13.12.2018 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Data storage using individual molecules

Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.

Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Formed to Meet Customers’ Needs – New Laser Beams for Glass Processing

17.12.2018 | Physics and Astronomy

Preserving soil quality in the long term

17.12.2018 | Architecture and Construction

New RNA sequencing strategy provides insight into microbiomes

17.12.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>