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Human aerosol emissions directly linked to stronger hurricanes in the Atlantic

Researchers have discovered a significant correlation between human-caused aerosol emissions and temperature fluctuations in the tropical Atlantic Ocean. This relationship, uncovered in a new study by the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, impacts both the rainfall in West Africa’s Sahel region and the formation of hurricanes in the Atlantic.

In the midst of a year marked by multiple hurricanes, including the notorious Hurricane Idalia, which formed swiftly over the tropical Atlantic, the study offers a fresh perspective. According to Chengfei He, the lead author and a postdoctoral researcher at Rosenstiel School, the discoveries suggest that “the variations in Atlantic ocean temperature, hurricanes, and Sahel rainfall are predominantly influenced by human-induced emissions.”

How the study was conducted

By employing a sophisticated grand ensemble simulation technique, which averaged over 400 climate model simulations from global climate centers, the team was able to extract the primary climate change drivers from the ‘noise’.

This approach, analogous to how noise-cancelling headphones function, illuminated the impacts stemming from external forcings on the climate system, predominantly from human activities and volcanic eruptions.

Amy Clement, a professor of atmospheric sciences at the Rosenstiel School and co-author of the study, elaborated on the novelty of the findings. While earlier beliefs suggested that the alterations in West African rainfall and Atlantic hurricanes were consequences of natural climatic cycles, such as the Atlantic Meridional Overturning Circulation, this research indicates otherwise.

Clement stated that their model simulations depicting forced climate changes “closely match the real-world observations in the tropical Atlantic.”

Linking aerosol emissions with hurricanes

A significant revelation from the study is the link between human-caused aerosol emissions and climatic events post World War II. The ensuing suppressed Atlantic hurricane activity and a drier Sahel can be attributed to these emissions.

The Sahel region, which extends south of the Saharan desert from the Atlantic to the Red Sea, experienced severe drought in the early 1980s, culminating in food shortages, widespread diseases, and the tragic loss of hundreds of thousands of lives from West Africa to Ethiopia.

The research notes a marked shift post the 1980s, as reduced aerosol emissions led to an increase in Atlantic hurricanes and enhanced Sahel rainfall. This pattern in sea surface temperature, hurricane activity, and Sahel rainfall closely mimics the observations in the tropical Atlantic.

While human-induced aerosol emissions undeniably influence hurricane season activity, the researchers caution against oversimplifying. Multiple factors determine the intensity and frequency of hurricanes, and even in low-activity seasons, potent storms can manifest.

Chengfei He warned of future implications, stating that due to the “continuous reduction in human-induced aerosol emissions around the Atlantic, complemented by the ongoing and future warming attributed to greenhouse gases, we might not see a return to the quieter hurricane activity witnessed in the mid-century Atlantic.”

This pivotal study, titled “Tropical Atlantic multidecadal variability is dominated by external forcing,” can be found in the September 13 issue of the esteemed journal, Nature.

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