SA climate change: what kind and where

A reservoir near Nieu-Bethesda in the Karoo. Eastern SA is looking at a short,
intense rainfall season in future. Across the country conditions will warm up and dry out.
Issue date 5 October 2007

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Climate change is coming – and now a study conducted by Dr Francois Engelbrecht of the University of Pretoria provides some specifics about what different SA regions can expect. Annelie Coleman reports.

According to Dr Francois Engelbrecht of the University of Pretoria, SA’s temperature has been rising at a rate of about 0,2ºC per decade over the last four decades. With greenhouse gas concentrations steadily increasing, temperatures over the African continent should rise even faster in future. On average southern Africa is likely to be 3ºto 5ºwarmer by the end of the century, with disastrous implications for the environment and agriculture. From the perspective of a human lifespan, these temperature increases should set in gradually, at a rate of 0,2ºto 0,3ºper decade, but the accumulated effects should have drastic consequences. El Niño and El Niña T here are strong indications that SA is drifting into a generally warmer and drier climate. Our rainfall is strongly linked to the El Niño/La Niña phenomenon, respectively linked to below and above normal rainfall in our summer rainfall regions. The El Niño phenomenon should occur more frequently in future, resulting in generally drier conditions over SA. The University of Pretoria has conducted a high-resolution modelling study of climate change over southern Africa, using an Australian climate model, called CCAM, to simulate climate and climate change.

CCAM uses the fundamental laws of physics to describe the ocean-landmass-atmosphere system. Over decades of simulated time, the model atmosphere gradually reacts to the enhanced greenhouse effect, just as the true atmosphere would. Weather forecast – long-term! I n this way, the model can estimate the influence of the enhanced greenhouse effect on temperature and rainfall patterns over SA. The model also simulates natural processes, such as El Niño and La events, and how these would change in the future. he study indicates that while SA is indeed moving into a generally drier climate, during some seasons wetter conditions may be expected in specific regions. xwinter rainfall region of the southwestern Cape should become drier, due to a displacement of frontal rain bands to the south.

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In spring, an increase in rainfall is expected over the central interior of SA, associated with cloud bands occurring more often over this region. the eastern region, spring will become drier. Summer is expected to become wetter over eastern but drier over the western interior. Autumn may be expected to become generally drier, in particular over eastern parts. Interpreting the data Much more research is needed to quantify SA’s potential future rainfall distribution. The size and even the direction of the changes to be expected is still uncertain. Complex patterns of change are present on the seasonal time scale. However, the above data indicate that is indeed heading for a generally warmer and drier climate, with a shorter and more intense rainfall season developing over eastern parts. he only region where the model simulated a slight increase in rainfall is the central interior, due to more frequent cloud band formation. A recent study of observed rainfall totals confirms this is a region of possible rainfall increase. |fw

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Annelie Coleman represents Farmer’s Weekly in the Free State, North West and Northern Cape. Agriculture is in her blood. She grew up on a maize farm in the Wesselsbron district where her brother is still continuing with the family business. Annelie is passionate about the area she works in and calls it ‘God’s own country’. She’s particularly interested in beef cattle farming, especially with the indigenous African breeds. She’s an avid reader and owns a comprehensive collection of Africana covering hunting in colonial Africa, missionary history of same period, as well as Rhodesian literature.