February 5, 2011 — andyextance

More frequent droughts are set to pose challenges to food supplies, and could worsen global warming still further. That’s a message that’s emerged over the past week, which has seen world food prices reach record highs, while researchers unveiled stark messages about drought in Africa and the Amazon forest.

Eastern Africa is seeing decreased rainfall due to warming in the Indian Ocean warn University of California, Santa Barbara, scientists Chris Funk and Park Williams. Over the past 60 years the Indian Ocean has warmed two to three times faster than the central tropical Pacific, they note in a paper published in the journal Climate Dynamics online ahead of print. This has driven increased rain and cycling of air through the atmosphere in the tropical Indian Ocean region. This has extended part of the air flow system known as the Walker circulation westwards, sending dry air towards eastern Africa.

“This response has suppressed convection over tropical eastern Africa, decreasing precipitation during the ‘long-rains’ season of March–June,” Funk and Williams write. Consequently, over the last 20 years, an increased frequency of drought has been observed in this region, making an estimated 17.5 million people food insecure in Kenya, Ethiopia, and Somalia. The scientists note that the US government has spent over $1.1 billion on food aid in these countries since 2009.

“Global temperatures are predicted to continue increasing, and we anticipate that average precipitation totals in Kenya and Ethiopia will continue decreasing or remain below the historical average,” said Funk, who is also affiliated with the US Geological Service. Since 2008, he and his colleagues have shown that the links between rain and the broader climate in the Indian Ocean are changing. As a result predictions previously used by the Intergovernmental Panel on Climate Change (IPCC), that rainfall in eastern Africa will increase as global temperatures rise, will have to be re-examined.

Funk now hopes that this research will identify areas of potential drought and famine in order to target food aid and help make decisions on agricultural development, environmental conservation, and water resources planning.“Although drought is one reason for food shortages, it is exacerbated by stagnating agricultural development and continued population growth.”

Meanwhile, 2010 saw a drought in the Amazon more severe than the one that occurred in 2005, which was described as a “once in a century event”. University of Leeds, UK, researcher Simon Lewis also warns in top journal Science that the drought might result in more than 5 billion tonnes of CO2 emissions. This is a reversal of the Amazon’s usual role removing CO2 from the atmosphere, and comes close to matching the 5.4 billion tonnes of CO2 people in the US produced in 2009 by burning fossil fuels.

“Two unusual and extreme droughts occurring within a decade may largely offset the carbon absorbed by intact Amazon forests during that time,” Lewis said. “If events like this happen more often, the Amazon rainforest would reach a point where it shifts from being a valuable carbon sink slowing climate change, to a major source of greenhouse gases that could speed it up.”

Lewis recently found himself fighting the UK’s Sunday Times, which quoted him to support an article criticising the IPCC. It used his comments to label the IPCC claim that “up to 40 percent of the Amazonian forests could react drastically to even a slight reduction in precipitation” “bogus”. In fact he believed the claim, although not perfect, was broadly correct.

Now, using satellite measurements of rainfall across 5.3 million square kilometres of Amazonia during the 2010 dry season, Lewis and his British and Brazilian colleagues have provided data supporting scientists’ previous predictions. “Having two events of this magnitude in such close succession is extremely unusual,” he said, “but is unfortunately consistent with those climate models that project a grim future for Amazonia.”