Bhekisisa: Why storms that used to happen every 50 years are hitting more often

Climate scientists agree that intense downpours and heavy storms are likely to happen more often and become more unpredictable in the future. But can every extreme weather event be pinned on climate change? We look at what past data and future predictions say.

The weather is good for small talk. But it’s been making big headlines more and more often lately.

In the first five months of this year alone, many parts of South Africa have been battered by storms, floods and lasting or scorching heat, with the government issuing three notices of weather-related national disasters and official warnings about severe heat between January and May.

Researchers agree that global warming caused by the release of large amounts of greenhouse gases from burning fossil fuels like coal and oil can be clearly linked to intense downpours and heavy storms occurring more often.

But how badly unexpectedly heavy weather will affect people’s lives depends on a combination of environmental factors and communities’ preparedness.

“We are vulnerable to events which we may be able to forecast but whose actual intensity in specific locations we may not be able to predict,” said President Cyril Ramaphosa shortly after the spate of heavy weather days in parts of the Western, Eastern and Northern Cape in early May, which claimed at least 10 lives, displaced thousands of people and badly damaged roads, buildings and utility systems.

And it is exactly this type of unpredictability that climate experts say the world has to stall itself against in the face of changing long-term weather patterns.

But can every extreme weather event be pinned on climate change?

To answer this, scientists compare how likely it would have been that an event of similar intensity would have occurred if the atmosphere had not warmed from what it had been about 150 years ago.

For example, rainfall like what caused the heavy floods in parts of Limpopo, Mpumalanga and Mozambique in January is likely to occur only every 50 years, researchers found, which makes it a rare event. But it would have been even rarer if the air had not warmed by about 1.3°C, their analyses showed. Moreover, datasets they looked at suggested that downpours during spells like these are becoming about 40% more intense.

Having historic or baseline data to compare current events to is important to help scientists predict how things might change, which, in turn, can help decision-makers plan ahead so that the fallout of extreme weather can be handled better.

In today’s story – the second in our series about what climate change could mean