Understanding Extreme Weather in a Changing Climate

ClimaMeter is an experimental rapid framework for understanding extreme weather events in a changing climate based on looking at similar past weather situations. Find out more here and follow us on X

Climate Change likely increased by up to 15% the heavy rainfall that caused Texas Floods

On May 5, 2024, a weather system fueled by anomalously warm air coming from the Gulf of Mexico produced intense and persistent rainfall over areas near and west of Huston, Texas, where the soil was already saturated from abundant precipitations in previous days and weeks. The rivers in the area reached levels unseen since hurricane Harvey, resulting in extensive flooding that required rescuing several hundred people, and causing at least one fatality. 

ClimaMeter found that weather systems similar to the one that caused the Texas Floods are up to 15% more rainy over some areas in the affected region. The analysis show that the Pacific Decadal Oscillation might have played a role in increasing the chance of a severe convective event. Results also suggest that the warmer than normal water in the Gulf of Mexico, which is warming as global temperature increases, has likely provided enhanced moisture and instability, making the event more intense.

Image:  Houston (Texas) during the flood

Climate change increased up to 15% the heavy rain that caused massive floods in South Brazil 

Between 30 April and 2 May, a low depression system across southern Brazil brought large amounts of rainfall to Rio Grande do Sul, with large regions of the state exceeding 200mm accumulated precipitation over three days. The massive rain caused a dam to collapse. At least 90 people died and more than 500,000 people are without water supply.

To analyze the drivers of this extreme meteorological event, ClimaMeter conducted a rapid analysis using a methodology based on historical meteorological information from the last 40 years. We compared how similar low depression systems were at the end of the 20th century (1979-2001) and how they are now, in recent decades (2002-2023), when the effect of climate change has become more evident. 

Using this methodology, ClimaMeter found that depressions akin to those that hit Rio Grande do Sul are now about 15% more intense. The analysis shows that climate change played an important role in fueling this heavy rainfall episode, as the contribution of El Niño alone can’t explain the intensity of the observed event.

Image:  Brazil Floods, source: twitter

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