Featured Research

from universities, journals, and other organizations

New insights on drought predictions in East Africa

Date:
January 18, 2013
Source:
Woods Hole Oceanographic Institution
Summary:
New research helps explain the mechanisms at work behind historical patterns of aridity in Eastern Africa over many decades -- findings that may help improve future predictions of drought and food security in the region.

Climate model simulations analyzed as part of the study revealed that the relationship between sea surface temperatures and atmospheric convection in the Indian Ocean changes rainfall in East Africa. Specifically, wet conditions in coastal East Africa are associated with cool sea surface temperatures in the eastern Indian Ocean and warm sea surface temperatures in the western Indian Ocean, which cause ascending atmospheric circulation over East Africa and enhanced rainfall. The opposite situation—cold sea surface temperatures in the western Indian Ocean and warmer in the East—causes drought. Such variations in sea-surface temperatures likely caused the historical fluctuations in rainfall seen in the paleorecord.
Credit: Courtesy Jessica Tierney, et al, 2013

With more than 40 million people living under exceptional drought conditions in East Africa, the ability to make accurate predictions of drought has never been more important. In the aftermath of widespread famine and a humanitarian crisis caused by the 2010-2011 drought in the Horn of Africa -- possibly the worst drought in 60 years -- researchers are striving to determine whether drying trends will continue.

While it is clear that El Niño can affect precipitation in this region of East Africa, very little is known about the drivers of long-term shifts in rainfall. However, new research described in the journal Nature helps explain the mechanisms at work behind historical patterns of aridity in Eastern Africa over many decades, and the findings may help improve future predictions of drought and food security in the region.

"The problem is, instrumental records of temperature and rainfall, especially in East Africa, don't go far enough in time to study climate variability over decades or more, since they are generally limited to the 20th century," explains first author Jessica Tierney, a geologist at the Woods Hole Oceanographic Institution (WHOI). Tierney and her colleagues at WHOI and the Lamont-Doherty Earth Observatory of Columbia University used what is known as the paleoclimate record, which provides information on climate in the geologic past, to study East African climate change over a span of 700 years.

The paleoclimate record in East Africa consists of indicators of moisture balance -- including pollen, water isotopes, charcoal, and evidence for run-off events -- measured in lake sediment cores. Tierney and her colleagues synthesized these data, revealing a clear pattern wherein the easternmost sector of East Africa was relatively dry in medieval times (from 1300 to 1400 a.d.), wet during the "Little Ice Age" from approximately 1600 to 1800 a.d., and then drier again toward the present time.

Climate model simulations analyzed as part of the study revealed that the relationship between sea surface temperatures and atmospheric convection in the Indian Ocean changes rainfall in East Africa. Specifically, wet conditions in coastal East Africa are associated with cool sea surface temperatures in the eastern Indian Ocean and warm sea surface temperatures in the western Indian Ocean, which cause ascending atmospheric circulation over East Africa and enhanced rainfall. The opposite situation -- cold sea surface temperatures in the western Indian Ocean and warmer in the East -- causes drought. Such variations in sea-surface temperatures likely caused the historical fluctuations in rainfall seen in the paleorecord.

The central role of the Indian Ocean in long-term climate change in the region was a surprise. "While the Indian Ocean has long been thought of as a 'little brother' to the Pacific, it is clear that it is in charge when it comes to these decades-long changes in precipitation in East Africa," says Tierney.

Many questions remain, though. "We still don't understand exactly what causes the changes in sea surface temperatures in the Indian Ocean and the relationship between those changes and global changes in climate, like the cooling that occurred during the Little Ice Age or the global warming that is occurring now," says Tierney. "We'll need to do some more experiments with climate models to understand that better."

In the past decade, the easternmost region of Africa has gotten drier, yet general circulation climate models predict that the region will become wetter in response to global warming. "Given the geopolitical significance of the region, it is very important to understand whether drying trends will continue, in which case the models will need to be revised, or if the models will eventually prove correct in their projections of increased precipitation in East Africa," says co-author Jason Smerdon, of the Lamont-Doherty Earth Observatory.

While it's currently unclear which theory is correct, the discovery of the importance of the Indian Ocean may help solve the mystery. "In terms of forecasting long-term patterns in drought and food security, we would recommend that researchers make use of patterns of sea surface temperature changes in the Indian Ocean rather than just looking at the shorter term El Niño events or the Pacific Ocean," says Tierney.

In addition, Tierney and her colleagues lack paleoclimate data from the region that is most directly affected by the Indian Ocean -- the Horn of Africa. The paleoclimate data featured in this study are limited to more equatorial and interior regions of East Africa. With support from National Science Foundation, Tierney and her colleagues are now developing a new record of both aridity and sea surface temperatures from the Gulf of Aden, at a site close to the Horn.

"This will give us the best picture of what's happened to climate in the Horn, and in fact, it will be the first record of paleoclimate in the Horn that covers the last few millennia in detail. We're working on those analyses now and should have results in the next year or so," says Tierney.

This research was based on work supported by the National Science Foundation and the National Oceanic and Atmospheric Administration (NOAA).


Story Source:

The above story is based on materials provided by Woods Hole Oceanographic Institution. Note: Materials may be edited for content and length.


Journal Reference:

  1. Jessica E. Tierney, Jason E. Smerdon, Kevin J. Anchukaitis, Richard Seager. Multidecadal variability in East African hydroclimate controlled by the Indian Ocean. Nature, 2013; 493 (7432): 389 DOI: 10.1038/nature11785

Cite This Page:

Woods Hole Oceanographic Institution. "New insights on drought predictions in East Africa." ScienceDaily. ScienceDaily, 18 January 2013. <www.sciencedaily.com/releases/2013/01/130118145354.htm>.
Woods Hole Oceanographic Institution. (2013, January 18). New insights on drought predictions in East Africa. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2013/01/130118145354.htm
Woods Hole Oceanographic Institution. "New insights on drought predictions in East Africa." ScienceDaily. www.sciencedaily.com/releases/2013/01/130118145354.htm (accessed July 25, 2014).

Share This




More Earth & Climate News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Virginia Governor Tours Tornado Aftermath

Virginia Governor Tours Tornado Aftermath

AP (July 25, 2014) — Virginia Gov. Terry McAuliffe toured the Cherrystone Family Camping and RV Resort on the Chesapeake Bay today, a day after it was hit by a tornado. The storm claimed two lives and injured dozens of others. (July 25) Video provided by AP
Powered by NewsLook.com
Europe's Highest Train Turns 80 in French Pyrenees

Europe's Highest Train Turns 80 in French Pyrenees

AFP (July 25, 2014) — Europe's highest train, the little train of Artouste in the French Pyrenees, celebrates its 80th birthday. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) — The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) — Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins