DURBAN - THE chill experienced across the country since last week Thursday was “the exception rather than the rule”, according to Climatology Professor Francois Engelbrecht of the Global Change Institute at the University of the Witwatersrand.
Engelbrecht said the extreme weather was the result of a cold front that swept cold air from the high latitudes of the Southern Ocean deep into the interior.
He said last Friday the South African Weather Service (Saws) released some statistics from weather stations where records had been broken in terms of the lowest minimum temperatures, a consequence of the cold front’s effect.
“Almost no part of South Africa escaped the cold weather. At Makhanda (Grahamstown), a new record was set in terms of the lowest maximum temperature measured: 6.8°C (length of record: 29 years),” said Engelbrecht.
But Engelbrecht said exceptionally cold winters over the interior were becoming the exception rather than the rule. Over the past five decades, clear upward trends in minimum temperatures have been detected – a regional consequence of global warming, he said.
“In fact, in a warmer world, the westerly wind regime over the Southern Ocean and embedded cold fronts are increasingly being displaced towards the South Pole, making it increasingly difficult for cold fronts to reach South Africa.
“On the average, frontal systems today already follow tracks about 200km further to the south than 50 years ago – the consequence of the combined effects of global warming and the depletion of the ozone layer over Antarctica.”
One consequence of this aspect of southern hemisphere climate change was that winters over South Africa have been becoming systematically warmer, said Engelbrecht.
He said this process had important consequences for winter rainfall. As the frontal systems are displaced southwards, decreasing rainfall is expected over the Western Cape and Eastern Cape, he said.
“This, in turn, means that multi-year droughts occurring in the winter rainfall region (for example, the Cape Town ‘day zero’ drought of 2015-2017) will become increasingly likely as the world continues to warm,” he said.
According to Engelbrecht, a recent study estimated that the risk of such droughts occurring are already three times higher than they were supposed to be, as a consequence of the southward displacement of the cold fronts that has occurred to date.
“Despite the hardship the extreme cold has brought, let us note that such northward displaced cold fronts often bring much-needed winter rainfall to the southern parts of South Africa,” he said. For example, during the past few days good rains fell over parts of the Eastern Cape that remain in the grip of an extreme drought.
Saws said KwaZulu-Natal has experienced mainly partly cloudy to sunny conditions with cool to cold temperatures since Thursday.
“Most stations recorded maximums below 20°, with the coldest being 8° in Underberg and 6° in Kokstad on Friday. The lowest minimum temperature recorded was -13° in Underberg on Saturday morning.”
The weather service said isolated showers were observed in places along the coast on Saturday and over the north-coast yesterday morning. Saws said at this stage warmer temperatures were expected this coming weekend.
THE MERCURY