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New African rainfall patterns

New African rainfall patterns africa924
06 Mar
2015
Satellite data reveals that over the last decade, Africa, as a whole, has become both wetter and greener

A new study led by the University of Leicester has concluded that there have been noticeable changes in rainfall across the African continent over the last ten years. The international research team was analysing satellite images of sub-Saharan Africa from a rain dataset produced by the Climate Prediction Centre of the National Oceanic and Atmospheric Administration (NOAA).

Together with the Joint Research Centre of the European Commission, the Institute of Electromagnetic Sensing of Environment of the National Research Council of Italy, and the Polish Institute of Geodesy and Cartography, the study analysed ten years of satellite data.

The researchers discovered drastically different amounts of rainfall compared to a decade earlier, with higher levels of rainfall in many areas, including large parts of the Sahel, more commonly associated with severe famines. Regions in West Africa, Central African Republic, western Cameroon and north-eastern South Africa were highlighted as benefiting most from the extra rainfall, and consequently increased vegetation, as compared to a decade previously.

However, other countries, such as the Congo, Nigeria and Madagascar, in turn experienced less rainfall.

Image-1Trend in rainfall over ten years. Blue = wetter conditions, red = drier conditions (Image: 2014 A.Hoscilo, H.Balzter, E.Bartholomé, M.Boschetti, P.A.Brivio, A.Brink, M.Clerici and J.F.Pekel)

The study, co-authored by Professor Heiko Balzter of the Centre for Landscape and Climate Research at the University of Leicester, does warn of drawing conclusions from these findings about the impacts in Africa of wider climate change.

‘The time-series is too short to say anything about long-term climate change,’ Professor Balzter tells Geographical. ‘We know for a fact that in Africa the weather is also fluctuating on time-scales of decades – multi-decadal oscillations – and not just on the time-scale of ten years that we were able to examine.’

He also warns about problems which could arise in those countries which have seen decreasing rainfall, saying: ‘This is an issue even in the wet tropics of the Congo, where low rainfall means restrictions to ship movements on the rivers there, which are the main transport routes in the dense jungle.’

On the subject of the increased rainfall across many other regions of Africa, Balzter directly links the greening of the Sahel region to the ‘wetter weather’, adding that it ‘depends highly on the African monsoon’. But again, he makes it clear that this does not mean we can conclude that these would be the same results as would be caused by climate change.

‘The weather systems can change a lot on the time-scales of tens of years,’ he says. ‘This means that our maps cannot be regarded as maps of long-term climate change impacts. They merely reflect climatic impacts over the past ten years. We know that this period is too short to relate it to the global warming debate.’

Image-2Trend in vegetation greenness over ten years. Green = greener conditions, red = less green conditions (Image: 2014 A.Hoscilo, H.Balzter, E.Bartholomé, M.Boschetti, P.A.Brivio, A.Brink, M.Clerici and J.F.Pekel)

The study will be published under the name ‘A conceptual model for assessing rainfall and vegetation trends in sub-Saharan Africa from satellite data’ in the International Journal of Climatology.

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