Warming may spell wet future for Africa

摘要

A flood of greenhouse gases into the atmosphere may trigger downpours in certain parts of Africa. Greenhouse gases play a large role in boosting rainfall in northern and southeastern areas of the continent, scientists report in the Dec. 5 Science. The finding may portend how climate change will alter access to water and help scientists understand other climate data that predict surges in African rainfall. Between around 21,000 and 14,700 years ago, Africa experienced a soggy era over a northern belt across the width of the continent and in a southeastern region around northern Tanzania. Using a computer simulation to re-crzeate that period, researchers led by Bette Otto-Bliesner of the National Center for Atmospheric Research in Boulder, Colo., individually added and removed variables that could have spurred the showers. These factors include an uptick in greenhouse gases noted during that time frame and changes to the Earth's tilt and orbit, which alter the amount of sunlight that reaches the planet's surface. Increases in greenhouse gases - to levels near to those of pre-industrial times - was behind much of the northern region's extra moisture and nearly all of it in the southeastern region, the researchers conclude.