“Our objective has been to make semi-quantitative predictions of 2030 food security in eastern and southern Africa,” said Chris Funk of the University of California, Santa Barbara. “If observed trends in rainfall, population and agricultural capacity continue, the combination of increasingly common droughts, rapidly growing food requirements and stagnating agricultural development could be very dangerous.”

Rainfall levels have already declined during the main eastern African long rains (in March, April and May) and the main summer rains in southern African (in December, January and February).

Chris Funk and colleagues from the University of California, Santa Barbara, the United States Geological Survey, NASA-Goddard Space Flight Center, and the University of Massachusetts Lowell, believe that the rainfall changes may be attributed to anthropogenic warming in the Indian Ocean. Together with declining agricultural capacity, the researchers say that the rainfall decreases are likely to constitute a prime example of societally dangerous climate change.

“Our work suggests strongly that greenhouse gas emissions, which have come mostly from wealthy developed countries, already constitute an example of dangerous climate change,” said Funk. “Our greenhouse-gas emissions have probably led to a roughly 15% decline in main growing season rainfall in parts of eastern and southern Africa. The rainfall declines, combined with tremendous levels of rural poverty and vulnerability, produce undernourishment, malnutrition, child stunting and social disruption, hindering progress towards Millenium Development Goals.”

Although the most recent IPCC simulations suggest that greenhouse-gas emissions will lead to a wetter eastern Africa, Funk believes “this is primarily a spurious result caused by the fact that the current generation of climate models represent precipitation very poorly over Africa”. His analysis of model results over the Indian Ocean, “where the models perform well”, shows that anthropogenic warming in the region “has caused and likely will cause main-growing-season drought in the world's most food-insecure countries.”

On the plus side, Funk says that the team’s food-balance modelling suggests that modest improvements in per capita agricultural capacity could substantially alleviate undernourishment, making Africa agriculturally self-supporting in 30 years.

Funk and colleagues decided to analyse rainfall- and agricultural-capacity trends in eastern and southern Africa following work for the US Agency for International Development’s Famine Early Warming System. Now Funk says the researchers are moving forward in several directions: downscaling, upscaling and adaptation. “On the downscaling front we're working on producing higher-resolution, 21st century projections of rainfall for Africa so that we can run crop models,” he said. “This will let us look at patterns of risks and opportunities for improved crop selection.”

Finally, on the adaptation side the team is working with Thomas Egwang, executive director of the African Academy of Sciences, to promote discussion and action on African climate change and food security. The researchers reported their work in PNAS.

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