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Causes and global warming

Causes and global warming

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Brazil is in a state Natural disaster Following the catastrophic floods that struck the state on April 27, 2024 Rio Grande do Sulin the far south of the country, is the worst since 1941, and is currently causing 83 deadAbout 300 people were injured, more than 110 were missing, tens of thousands of people were evacuated, and at least 500,000 people were without electricity and clean water. The most affected area was the surrounding area Porto Alegrethe capital of Rio Grande do Sul, where it is found in some places 150 mm Rainfall within 24 hours, the amount expected during the entire month of April. Heavy rains caused rivers to overflow and landslides, with disastrous consequences, from the destruction of roads and bridges to the partial collapse of a hydroelectric dam along the Tacuari River between Pinto Gonçalves and Cutipora. Porto Alegre was completely flooded in about 60 streets and the international airport was closed. the Lake Guayba It reached a record high on Sunday, May 5 5.31 pmIt was never recorded even during the devastating historic flood of 1941.

What happened in Brazil: a meteorological analysis

The first alerts from Brazilian Civil Protection were issued on April 22, when an anti-cylinder high pressure system caused an air mass in northern Brazil, accompanied by an intense heatwave with temperatures up to 10 °C above the average for that period. As the warm, moist air moved south, it encountered a cold front associated with a low pressure system over the Atlantic Ocean: causing severe turbulence that began to hit Rio Grande do Sul in April 27.

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On April 30th Pinto GonsalvesIt fell north of Porto Alegre 149.2 mm Rainfall within 24 hours is above the historical average for the region throughout April. While here the monthly average for April is 112 mmIt means that the expected rain fell in one day 40 days This time of year. It’s also worth noting that, again on April 30, 146.6 mm to Rio PardoWest of Porto Alegre.

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Satellite image from April 30. Red indicates heavy rain on that date. Credits: Inmate.

Then the situation worsened 2 MaggioWhen strong storms coming from the ocean hit an area that is already saturated with water.

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Storms over Rio Grande do Sul on May 2. Credits: NASA – NASA’s World View.

In fact, this region has long been concerned with extreme weather events: it is an area where masses of hot air coming from the tropics collide with cold air of polar origin. The clash between fronts and cold fronts is the perfect recipe for heavy rainfall. In 2023 alone, there were three different floods in Rio Grande do Sul (in July, September and November), which caused a total of 75 deaths. But the last few days have been an event Exceptional densityIt has never been seen in the region for 80 years.

The role of the El Niño phenomenon in the Brazilian floods

According to experts, the factor that contributed to the disaster in Rio Grande do Sul is BoyIt is a climate phenomenon that causes the temperature of the central-eastern Pacific Ocean to rise by at least 0.5 degrees Celsius for at least 5 months. It is a periodic phenomenon, repeated over a maximum period of 7 years, and affects the climate of the entire planet. Last year was marked by a particularly strong El Niño, which was also felt in Brazil and which is still present albeit with weak intensity.

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In general, in Brazil, the El Niño phenomenon causes drought in the north of the country and an increase in rainfall in the south of Brazil. Indeed, 2023 was recorded Severe drought in the Amazon region And floods in Rio Grande do Sul in 2023. Experts had expected that the El Niño phenomenon would continue until this time of year, and in fact it has not completely disappeared yet. Forecasts stated an increased possibility of floods on the southeastern coast of Brazil, according to meteorologists fromInmit (Brazilian National Institute of Meteorology) They agree that El Niño played a role in increasing the intensity of rainfall in Rio Grande do Sul.

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Image taken by the European Sentinel-2 satellite of floods causing flooding in southern Brazil. Credits: EU/Copernicus.

Brazil and Dubai: Does global warming have anything to do with it?

All this happened just three weeks after the tragic floods in the Arabian Peninsula, the most severe since at least 1949, which hit Dubai and Oman in particular, where 19 people died. It’s almost instinctive to wonder if it’s there communication Between two record floods So close in time. The answer is not so simple: on the one hand, a connection between two climate events in such remote areas of the planet should be ruled out, but on the other hand we should not be surprised if extreme events like the one in 2008 occur. They brought Brazil to its knees. This is happening in Oman more and more frequently. Among the many impacts of the climate crisis caused by human-induced global warming, there is actually an increase in the frequency and intensity of extreme weather events.

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Be careful, this one non This means that responsibility for a single extreme event – ​​such as the floods in Brazil or those in Dubai – can be attributed to global warming. There is no direct causal relationship at any level bachelor It happened. The impact of the climate crisis is to make weather and climate disasters increasingly frequent and increasingly harmful.