Durban - Drought-stricken South Africa is unlikely to get a good top-up of heavy rain in the coming summer months, with local and international climate boffins predicting one of the strongest El Nino weather events in more than half a century.
The other bad news is that climate experts at the CSIR warned on Thursday that this year was on its way to being the warmest year ever recorded, partly owing to climate change and partly to the massive El Nino event developing over the Pacific Ocean.
Strong El Nino weather events often – but not always – lead to drier conditions in southern Africa.
Last week the World Meteorological Organisation issued a special El Nino update, warning that sea surface temperatures over parts of the Pacific Ocean were expected to rise 2ºC above average over the next few months.
Because the El Nino/Southern Oscillation is one of the major drivers of the climate system, a strong El Nino was expected to trigger unusual or extreme climate events way beyond the Pacific.
The Indian met department, for the first time in its history, was predicting 12 percent less rainfall.
The World Meteorological Organisation said that in Africa, a strong El Nino event often led to more rain over the Horn of Africa, whereas southern Africa often became drier.
Dr Willem Landman, chief researcher (seasonal forecasts) at the CSIR in Pretoria, told The Mercury that the El Nino signal was strong and that there was “a very, very good chance” that it would strengthen over the coming months.
“The intensity forecast shows a 2ºC warmer than average sea surface temperature over the Pacific. I think it may be even hotter, which would make this event one of the strongest – if not the strongest – over the past few decades.
Drought
“In short, it is highly likely it will be a strong event. Where there is a warming pattern and an El Nino together, they don’t generally bring good news for South Africa’s farmers, because they generally contribute to drought conditions.”
Landman said while strong El Nino events did not necessarily mean that South Africa would get less rain, none of the models were showing good summer rain.
“The models are telling us that its more likely to be dry.”
However, it was not possible to predict the intensity of the drier conditions or to make reliable predictions on percentage rainfall reductions.
“We can only predict if there is a high probability of dry conditions over this period (September 2015 to April 2016).
The World Meteorological Organisation outlook suggests that this El Nino is likely to be among the strongest since the last event in 1997-1998 “and is potentially among the four strongest events since 1950”.
SA Weather Service long-range forecaster Asmerom Beraki also said El Nino events usually led to drier and warmer conditions in KwaZulu-Natal and the rest of South Africa.
Although this was not always the case, “caution was given to the summer rainfall areas of South Africa to be ready for a generally dry summer season”.
The CSIR climate modellers said temperatures over subtropical southern Africa had risen at more than twice the global rate over the past five decades.
Moreover, further warming of 4ºC-6ºC over the subtropics and 3ºC-5ºC over the tropics is projected by the end of the century relative to the present-day climate – depending on the rate of man-made greenhouse gas emission reductions.
The predictions are based on a CSIR study using a powerful computer cluster at the Centre for High Performance Computing.
This study comes ahead of the UN Framework Convention on Climate Change’s 21st Conference of the Parties, which is due to take place in Paris in November.
“If the negotiations fail to ensure a high-mitigation future, we are likely to see rapidly rising surface temperature across the continent,” said Dr Francois Engelbrecht, CSIR principal researcher and leader of the study.
The Mercury