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Cyclones a reality as oceans warm up

Locals affected by Cyclone Idai walk on flooded land in Buzi district outside Beira, Mozambique, March 21, 2019.
Locals affected by Cyclone Idai walk on flooded land in Buzi district outside Beira, Mozambique, March 21, 2019.
Image: REUTERS/Siphiwe Sibeko

Tropical cyclone Idai has made headlines across southern Africa throughout this month.

Lingering in the Mozambique Channel at tropical cyclone intensity the storm made landfall in Beira, Mozambique in the middle of the month, then tracked in a westerly direction until its dissipation.

The storm caused flooding, excessive wind speed and storm surge damage in the central region of Mozambique.

Adjacent countries of Malawi and Zimbabwe experienced severe rainfall, flooding and damage from the high wind speed. Madagascar also experienced bouts of high rainfall during the storm's pathway to Beira.

The flooding has left hundreds of thousands of people homeless and displaced across the region while the death toll has continued to rise.

The effects of the cyclone were felt as far south as SA which introduced rolling blackouts due to damaged transmission lines that supply the country with 1100MW of power from Cahora Bassa in northern Mozambique.

Historically, nine storms that had reached tropical cyclone intensity made landfall on Mozambique, with the most severe being tropical cyclone Eline in February 2000.

It had a category 4 intensity and resulted in 150 deaths and 300,000 people displaced.

Tropical cyclones are large storm systems. A 100km radius is typical of category 1 tropical cyclones, the lowest-intensity ones. As the storms intensify to categories 2, 3, 4 and 5, the size increases significantly. This means a high intensity storm, such as tropical cyclone Idai, has a range of impact larger than the storm track that it follows.

In recent years concerns have been growing about the impact of climate change on cyclones. Research has shown that changes to the world's temperature, as well as ocean warming, are responsible for an increase in the severity of tropical cyclones.

This has recently been researched for the South Indian Ocean. As the ocean is warming, the region which experiences temperatures conducive to tropical cyclone formation is expanding and temperatures in the tropical regions are becoming warm enough for cyclone intensification.

Category 5 tropical cyclones, which have been experienced in the North Atlantic for almost a century, started to occur in the South Indian Ocean since 1994, and have occurred increasingly frequently since then.

This means that as climate change continues and intensifies, so too do these storms. This will mean a greater frequency of not only severe damage from storms, but damage over a larger region.

This requires countries to communicate effectively with one another to provide coherent messages about the forecasting of the storm track.

This storm provides a grim prospect of the future of tropical cyclones in a region under continued threat from climate change. Effective adaptation to minimise storm damage is essential in preparing the region for an increase in the severity of these storms.

- Fitchett is senior lecturer in physical geography at Wits. Article appears courtesy of The Conversation.

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