Supercomputer peers into SA’s climate future — and paints a frightening picture

27 Nov 2022

The Lengau supercomputer at the Council for Scientific and Industrial Research Centre for High Performance Computing in Rosebank, Cape Town, has been working on future climate models for South Africa.

In Cape Town, a modern-day oracle has peered into our future and what it saw was frightening.

The future it predicted holds killer heatwaves, storms of unprecedented power and habitat-altering droughts.

The Lengau supercomputer at the Council for Scientific and Industrial Research (CSIR) Centre for High Performance Computing in Rosebank, Cape Town, has been working on future climate models for South Africa.

What Lengau, which means cheetah in Sotho, predicted is that South Africa is likely to face four tipping point events that will cause irreversible changes to the country’s climate system.

And they could happen in the next decade or two.

The first tipping point event is a Day-Zero drought hitting Gauteng, devastating the economy of the province and causing an unprecedented humanitarian crisis.

“This is where the Vaal [Dam] is not at 95%, it is at 25%. That is a true water crisis. Because when the levels fall to below 20%, then it is really difficult to get to the water,” said Francois Engelbrecht, a professor of climatology at Wits University’s Global Change Institute.

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“This affects businesses, industry and households. I would say there may be a risk of social unrest. And this is our single biggest climate change danger in South Africa.”

The second tipping point is the complete collapse of South Africa’s maize crops and its cattle industry. This will be brought on by a series of long-lasting droughts. Southern African farmers got a taste of this during the 2015/2016 drought during which Botswana lost 40% of its cattle.

Killer heatwaves are the third predicted tipping point, which could result in the deaths of tens of thousands.

The fourth tipping point is a weather phenomenon not yet seen in South Africa.

The warming of the Mozambique Channel is bringing the possibility of Category 4 or 5 tropical cyclones moving further south than usual and making landfall in Maputo or even Richards Bay.

Hurricane Katrina, which hit New Orleans in 2005, killing 1,800 people and causing damage amounting to $125-billion, was classified as a Category 5 tropical cyclone.

Those in the path of a Category 4 or 5 cyclone will face wind speeds of more than 200km/h, torrential rainfall of up to 1,000mm in a 24-hour period and deadly storm surges.

South Africa doesn’t have a cyclone season, so its citizens and government would be unprepared for such a disaster.

Predicting when they will occur

While southern African climate models see these four tipping points somewhere on the horizon, the problem is tying down when they are likely to arrive.

“We have just launched two major research projects that will, for the first time, formally quantify the likelihood of these tipping points occurring in southern Africa in the next 10 years, and in the next 20 years,” said Engelbrecht.

“One project, that is funded by the National Research Foundation, is specifically focused on understanding the risk of a Day-Zero drought in Gauteng.”

The other project involves scientists from South Africa, Namibia, Botswana, Zambia and Germany studying heatwaves and their impact on the cattle industry. The project will also look at the effects of droughts on large mammals in national parks and on communities that are reliant on groundwater.

“So we have this group of experts and we are hoping to make progress in understanding these two tipping point risks in southern Africa,” says Engelbrecht.

“Because we are arguing that if we can go to Rand Water or the Department of Water and Sanitation, and we can give them published credible research, saying that the risk is large, let’s say it’s a 30% or 50% chance that it may occur in the next 10 years, then one should expect them to take action. But if you can’t tell them exactly how big the risks are, it’s difficult for them to take the right actions.”

Earlier this year, South Africa experienced a little of the future of which Lengau has forewarned.

The floods in KwaZulu-Natal in the week leading up to Easter caused billions of rands in damage, displaced 40,000 people and left 448 dead.

In a warming world, more extreme weather events like the KZN floods are expected to happen.

“I think there are very important lessons to be learnt from [the KZN floods]; it shows how vulnerable we are across South Africa,” said Engelbrecht.

“We need to become more efficient in terms of our early warning systems, and also the uptake of those warnings in communities. And if we can learn from [the KZN floods], it may help us to prepare for that day when we get a Category 4 or 5 hurricane moving as far south as Maputo or even Richards Bay.”

Global tipping points

Countries across the world are facing the possibility of climate tipping points.

A recent study that appeared in the journal Science concluded that multiple climate tipping points could be triggered if the global temperature rises beyond 1.5°C above pre-industrial levels.

These tipping points include the Greenland ice sheet collapse, the Amazon rainforest die-off and the melting of permafrost.

The timespans over which these tipping points occur could vary from decades to hundreds of thousands of years.

The lead author of the study, David Armstrong McKay from Stockholm Resilience Centre, University of Exeter, and the Earth Commission, explained: “We can see signs of destabilisation already in parts of the West Antarctic and Greenland ice sheets, in permafrost regions, the Amazon rainforest, and potentially the Atlantic overturning circulation as well.

“The world is already at risk of some tipping points. As global temperatures rise further, more tipping points become possible.”

The Sixth Assessment Report of the Intergovernmental Panel on Climate Change stated that the risks of triggering climate tipping points become high at around 2°C above pre-industrial temperatures and very high from 2.5-4°C.

“Since I first assessed climate tipping points in 2008, the list has grown and our assessment of the risk they pose has increased dramatically,” said another co-author of the paper, Tim Lenton, the director of the Global Systems Institute at the University of Exeter. DM/OBP

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Predicting when they will occur

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