The images circulated around the world, appearing almost surreal. On April 15 and 16, deluge after deluge of rain fell on large parts of the United Arab Emirates, Oman, Bahrain and Saudi Arabia, countries on the Arabian Peninsula known for their aridity. In Dubai, the Emirates' most populous city, a gigantic, twilight-colored thunderstorm towered over skyscrapers, before the monumental highways, shopping malls and even the airport, one of the world's busiest, were flooded. It would be several days before all the water could be drained away.

The storms killed four people in the United Arab Emirates and 20 in Oman. They also caused extensive damage, severely disrupting infrastructure and city operations. Dubai Airport canceled over 2,000 flights, only returning to normal operations after a week. On Wednesday, the oil-rich country announced an aid package of $544 million to repair damaged homes.

The term "deluge" is appropriate. The Emirates recorded the equivalent of almost two years' worth of rainfall in the space of a single day, with up to 250 millimeters in some areas. These torrential rains were the most extreme event in the country since recording began 75 years ago.

While the spectacular and unusual nature of the phenomenon has not failed to fuel speculation and controversy as to its causes, a scientific study published Thursday, April 25, by the World Weather Attribution, provides some answers. The international network of researchers believes that global warming – which has already reached 1.2°C since pre-industrial times and is caused by the burning of fossil fuels (coal, oil and gas) – is the most likely explanation. However, the researchers are unable to determine precisely how much of this is due to human influence.

In the southern Arabian Peninsula, an area subject to rainfall that is as rare as it is irregular, two trends can be seen in historical observations. On the one hand, heavy rainfall is more frequent during El Niño years, the ongoing natural phenomenon that is warming the planet. Mansour Almazroui, a climatologist at King Abdulaziz University in Jeddah, Saudi Arabia, and an author of the study, explained that the very warm waters of the Pacific, Atlantic and Indian oceans carried a lot of energy into the atmosphere, fuelling the vast storm systems.

On the other hand, the heavy precipitation that occurs during El Niño years is now between 10% and 40% more intense than in pre-industrial times. The amplitude of the range reflects a significant degree of uncertainty, linked to the low number of extreme precipitation events recorded in the archives and the very high variability from one year to the next.

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