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Persistent heavy rains fuelled a third consecutive week of deadly flooding in Brazil’s southernmost state of Rio Grande do Sul, devastating a region which is a key agricultural and economic driver of the national economy.
More than 150 people have been confirmed dead and 104 remained missing, with some 600,000 displaced and a total 2.2mn out of a population of about 10mn affected by the historic floods, which many meteorologists have attributed to global warming.
The Guaíba river, which runs by the state capital Porto Alegre, breached its banks to rise a record of 5.33 metres at its peak last week. This compares with a previous record of 4.76 metres in 1941, and a flood point above 3m.
The waters subsided slightly before rising again as fresh rains fell at the start of this week, renewing warnings from authorities.
By Friday, the river level had fallen below 5 metres for the first time in several days but experts warned that it could take weeks for the waters to retreat to anywhere near normal levels.
Economists estimate the disaster — which some have compared to Hurricane Katrina’s impact on New Orleans in 2005 — will shave up to 0.3 per cent off Brazilian growth this year. Officials estimate economic damage done to be about $2bn.
The state accounts for about 6 per cent of Brazil’s GDP and produces more than two-thirds of its rice, as well as growing tobacco, wheat and soy, and livestock.
The region is at a geographical meeting point between tropical and polar atmospheres, which creates a weather pattern with periods of intense rains or drought.
These atmospheric conditions are exacerbated by climate change, as well as the influence of the naturally occurring El Niño phenomenon, which warms the Pacific Ocean.
The period between the end of April and the beginning of May 2024 was still influenced by El Niño, the World Meteorological Organization said.
Its warming effect helped block cold fronts and concentrate the systems of areas of instability over Rio Grande do Sul.
In addition, the much higher temperature of the south Atlantic Ocean, close to the equatorial belt, also contributed to the humidity, intensifying the rainfall, the WMO said.
The transport of humidity from the Amazon and the contrast with the warmer air to the north, as well as colder air to the south of Rio Grande do Sul, helped to strengthen the storms, the Brazilian weather agency, Inmet, said.
While the El Niño conditions are expected to weaken to neutral and shift to the opposing La Niña phenomenon of the cooling of the Pacific Ocean, there is uncertainty in its strength and timing, the WMO has noted.
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