In an article titled “A westward extension of the warm pool leads to a westward extension of the Walker circulation, drying eastern Africa,” published online in Climate Dynamics: Observational, Theoretical and Computational Research on the Climate System (DOI: 10.1007/s00382-010-0984-y) on February 4, UCSB Geography Researchers Chris Funk and Park Williams note that “Observations and simulations link anthropogenic greenhouse and aerosol emissions with rapidly increasing Indian Ocean sea surface temperatures.” Sid Perkins, writing for Nature Climate Change, provides the following summary in the journal’s research highlights—“Continued warming of the Indian Ocean could lessen rainfall over east Africa”:
Spikes in Indian Ocean sea-surface temperature have changed the region’s weather patterns and triggered more frequent droughts in east Africa in recent decades. Research now suggests this trend may continue, with dire implications for agriculture and food security. When climate scientists Park Williams of the University of California, Santa Barbara, and Chris Funk of the US Geological Survey in Sioux Falls, South Dakota, looked at climate data for the tropical Pacific and Indian Oceans from 1948 through to 2009, they found that the strongest year-to-year variations in climate occurred in the southern tropical Indian Ocean. In years when sea-surface temperatures (SSTs) were unusually high, evaporation was enhanced, boosting rainfall over the ocean. Consequent changes in atmospheric circulation brought dry air masses over eastern Africa, triggering drought. During the past few decades, each 1 °C rise in global average temperature boosted Indian Ocean SSTs by about 1.5 °C. Because global warming is expected to continue, east African rainfall will probably continue to decrease, threatening an area where 17.5 million people suffered food insecurity after severe droughts in 2008 and 2009.
