The Impact of Human Emissions on Atlantic Temperature Variability, African Rainfall Patterns, and Hurricane Activity

A recent climate study, led by researchers at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, has unveiled a significant connection between human-induced aerosol emissions and both Atlantic hurricane activity and Sahel rainfall patterns. This groundbreaking research, published in the journal Nature on September 13, demonstrates that fluctuations in tropical Atlantic Ocean temperatures are primarily fueled by these emissions, exerting profound impacts on weather phenomena in two distant regions: West Africa’s Sahel and the formation of hurricanes in the Atlantic.

In a year marked by the occurrence of several hurricanes, including Hurricane Idalia, forming in close succession over the tropical Atlantic, this study’s findings carry particular weight. Chengfei He, the lead author of the study and a postdoctoral researcher at the Rosenstiel School, asserted, “Our findings suggest the waxing and waning in Atlantic ocean temperature, hurricanes, and Sahel rainfall are largely driven by human-induced emissions. The novel results are hidden in the noise and can only be revealed by new techniques.”

To reach these remarkable conclusions, the research team employed a grand ensemble simulation technique that amalgamated data from over 400 climate model simulations conducted by climate centers worldwide. This approach, akin to noise-canceling headphones, unraveled the climate changes attributed to external forces, primarily stemming from human activities and volcanic eruptions. This revelation marks a substantial departure from long-standing assumptions, where variations in West African rainfall and Atlantic hurricanes were thought to be driven solely by natural climate cycles, such as the Atlantic Meridional Overturning Circulation.

The historical ramifications of their findings are also noteworthy. The study indicates that the reduced activity of Atlantic hurricanes and drier conditions in the Sahel region in the decades following World War II were predominantly instigated by human-generated aerosol emissions. This culminated in a devastating drought in the early 1980s, leading to food shortages and diseases that claimed the lives of hundreds of thousands from West Africa to Ethiopia. Subsequent reductions in aerosol emissions post-1980s translated into an uptick in Atlantic hurricanes and greater Sahel rainfall.

Furthermore, the research underlines the remarkable similarities between sea surface temperatures, hurricane activity, and Sahel rainfall patterns observed in the tropical Atlantic, all of which align with the study’s model simulations.

However, the researchers caution that hurricane activity remains influenced by numerous factors, and storms may still manifest even during seasons with overall low activity. Chengfei He added, “Due to the continuous reduction in human-induced aerosol emissions around the Atlantic, along with ongoing and future warming due to greenhouse gases, we suggest there will not likely be a return to the quiet period in hurricane activity in the Atlantic in the decades of the mid-century.”

In summary, this study, titled “Tropical Atlantic multidecadal variability is dominated by external forcing,” published in Nature on September 13, 2023, represents a groundbreaking shift in our understanding of the intricate relationship between aerosol emissions, Atlantic hurricane activity, and Sahel rainfall patterns. The research team consisted of Chengfei He, Amy C. Clement, Sydney M. Kramer, Mark A. Cane, Jeremy M. Klavans, Tyler M. Fenske, and Lisa N. Murphy from the University of Miami Rosenstiel School, alongside Sydney Kramer and Jeremy Klavans from the University of Colorado, and Mark Cane from Columbia University.

This study received support from NOAA (Grant No. NA20OAR4310400), the Climate and Large-Scale Dynamics program of the National Science Foundation (Grant Nos. AGS 1735245 and AGS 1650209), and the Paleo Perspectives on Climate Change program of the National Science Foundation (Grant No. AGS 1703076).

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