One odd fact that you may not know about El Niño — an unusually powerful one is expected this year — is that the waters in the Pacific don’t just become warmer and circulate less vigorously, which causes all sorts of weather changes across the globe.

El Niño also causes sea levels to fluctuate weirdly. To the east, the temperature shift can cause the sea to rise, possibly resulting in disastrous flooding along the California coast. At the same time, sea level temporarily may drop by as much as a foot in the Southern Hemisphere

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But here’s some even worse news for the Samoans and other South Pacific island residents. Thanks to climate change, we’re going to see more frequent powerful El Niño events in the future, with more frequent extreme sea-level swings — and the islands are going to suffer because of it, with increased destruction of coral, as well as coastline erosion and flooding when sea levels rebound.

That dire forecast comes from a new study by scientists at the University of Hawaii at Mānoa’s  International Pacific Research Center, and their colleagues at the Commonwealth Scientific and Industrial Research Organisation in Australia.

Using climate modeling, the researchers projected that by the end of the century, the intensified wind impacts of strong El Niño and La Niña events are likely to double the frequency of extreme sea level occurrences, especially in the tropical southwestern Pacific.

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“We noted a trend in greater variability and were surprised at first to find not only more frequent and prolonged drops in sea level, but also more frequent high sea level events,” University of Hawaii at Mānoa  researcher Axel Timmermann explained in a press release. “This will further increase the risk of coastal inundations.”

“The possibility of more frequent flooding in some areas and sea level drops in others would have severe consequences for the vulnerable coastlines of Pacific islands,” his colleague Matthew Widlansky added.