Climate: why the multiplication of heatwaves combined with marine flooding threatens coastlines ?

Climate: why the multiplication of heatwaves combined with marine flooding threatens coastlines ?

Extreme heat and rising sea levels are usually studied separately, but researchers from the Hong Kong Polytechnic University have found that the two phenomena combine and that the frequency of wave-sinking during a heatwave could be multiplied by five by mid-century. Dimitar DILKOFF/AFP

The risk of simultaneous occurrence of a heatwave and marine submersion, due to storms during periods of high tides, is multiplied by global warming and the continued rise in sea levels, according to a study published Thursday which promotes the adaptation of coastal populations to this threat.

Extreme heat and sea level rise are usually studied separately, but researchers at the Hong Kong Polytechnic University found that the two phenomena combine and that the frequency of waves -submersion in the heatwave could be multiplied by five by the middle of the century.

These events pose "very dangerous" threats to coastal communities, combining excess mortality from heatwaves to floods, in proportions that could "exceed their capacity to adapt", l'told AFP ;lead author of the study, Mo Zhao.

Previous studies have already established that heat fuels storm regimes, such as tropical cyclones, that cause occasional sea level rises, said co-author Shuo Wang, an expert on hydroclimate extremes.

Their study, published in the journal Communications Earth & Environment, demonstrates that high temperatures not only precede storms, but persist during them, leaving populations at the mercy of both extremes.

A world warmed by at least 1.2°C

Coastal areas around the world have already seen these combined events occur on average 3.7 days more per year between 1998 and 2017 compared to the previous two decades.

By 2049, the study predicts, these events will increase by an average of 31 days per year if humanity continues unabated with its current global greenhouse gas emissions# 39;origin of global warming. Africa and the east coast of South America would see the largest increases, according to the authors.

Nearly 900 million people worldwide live in low-lying coastal areas, according to a study published in 2023 by the University of Cambridge, which predicts an increase in a third in the coming decades.

For the populations concerned, the solution cannot be reduced to installing air conditioning. Not only is it not widespread in poor countries, underlines the study, but it is energy-intensive and exposed to power cuts, frequent during storms.

"If we take urgent action to mitigate climate change, the situation will improve", believes Shuo Wang. But in a world that has already warmed by at least 1.2°C since the pre-industrial era, these extreme events cannot be completely avoided.

Governments must therefore already invest in the adaptation of coastal infrastructure in order to better protect populations, and in early warning systems, recommends Mr. Wang.< /p>

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