Once-in-a-century extreme weather events to happen annually

Even if global warming is limited to 1.5°C above pre-industrial levels, once-in-a-century extreme-sea-level events will occur every year, according to an international study.

The study models the frequency of extreme-sea-level events – triggered by a combination of storm surges, tides and waves – that we will see across the globe as temperatures increase.

“At vulnerable locations, high extreme sea levels can constitute severe hazards, causing extensive damages to both human settlements and coastal ecosystems when natural and engineered defenses are overtopped or breached,” the authors explain in their paper, published in Nature Climate Change.

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As global temperatures rise, so will global mean sea levels. This alone will increase coastal flooding and erosion, but it also increases damage done by waves and storm surges.

The study used computational modelling to assess the potential for coastal flooding on a global scale. It covered a wide range of emissions scenarios (taking into account temperature rises of between 1.5°C and 5°C above pre-industrial levels) and looked at the risks across a large number of coastlines to provide uniform coverage over most of the world’s shores.

“We estimate that by 2100, approximately 50% of the 7,000+ locations considered will experience the present-day 100-year extreme-sea-level event at least once a year, even under 1.5°C of warming,” the authors write.

They say that coastlines in the tropics, as well as parts of the Mediterranean and Arabian Peninsula, “appear more sensitive than the northern high latitudes, where some locations do not see this frequency change even for the highest global warming levels”.

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Other locations may see a surge in these extreme events well before the end of the century – in the 2070s or 2080s if warming is limited to 1.5 °C, and as early as the 2060s if it blows out to 4°C or 5°C.

“Our findings have important policy and practical implications as they highlight that even if the Paris Agreement goals will be achieved, extreme events potentially conducive to coastal flooding will be experienced at unprecedented frequencies in many parts of the world’s coasts,” the authors conclude.

This research follows on the heels of the Intergovernmental Panel on Climate Change’s sixth assessment report, which says that we need to immediately slash greenhouse-gas emissions and rapidly reduce our reliance on fossil fuels in order to avoid the worst-case scenarios of extreme weather, sea-level rise and more.

It also comes as Hurricane Ida hits the eastern US, leaving millions without power, destroying homes and claiming at least one life – a death toll that’s predicted to increase. Scientists have been warning that climate change is making hurricanes stronger, slower and wetter – and Ida checks all these boxes.

Fuelled by warmer-than-normal water in the Gulf of Mexico, Ida is also generating large storm surges along the coast.