A comprehensive study from the University of Miami shows that human-induced aerosol emissions are a major driver of temperature changes in the tropical Atlantic Ocean. These fluctuations strongly influence rainfall in the West African Sahel region and the occurrence of Atlantic hurricanes. The researchers found that Atlantic hurricane activity and Sahel rainfall follow patterns of aerosol emissions.
A new climate study led by scientists at the University of Miami's Rosenstiel School of Oceanic, Atmospheric and Earth Sciences finds that temperature fluctuations in tropical Atlantic temperatures are largely driven by human-induced aerosol emissions, affecting rainfall in the West African Sahel and hurricane formation in the Atlantic.
The research results were published in the journal Nature on September 13. Within a year, multiple hurricanes, including Hurricane Idalia, formed over the tropical Atlantic.
"Our results show that increases and decreases in Atlantic temperatures, hurricanes, and Sahel rainfall are largely caused by anthropogenic emissions," said Chengfei He, lead author of the study and a postdoctoral researcher at the Rosenstiel School. "In noise disturbances, they can only be revealed through new technologies."
Continued declines in human-induced aerosol emissions around the Atlantic Ocean, combined with ongoing and future warming due to greenhouse gases, suggest that Atlantic hurricane activity may not return to a lull in the mid-century decades. Image source: NOAA
The researchers used large ensemble simulation techniques to average more than 400 climate model simulations from the Global Climate Center. Like noise-canceling headphones, the technology shows climate change caused by external forcing, primarily from the impact of human activities and volcanic eruptions on the climate system.
"Changes in West African rainfall and Atlantic hurricanes have long been thought to be driven by natural cycles within the climate system, such as the Atlantic Meridional Overturning Circulation," said study co-author Amy Clement, a professor of atmospheric sciences. Rosenstiel School. "Now we find that the forced climate changes in our model simulations agree well with real-world observations in the tropical Atlantic."
Results from these simulations suggest that Atlantic hurricane activity was suppressed and the Sahel became drier in the decades following World War II, primarily due to anthropogenic aerosol emissions. The Sahel region of West Africa stretches from south of the Sahara Desert to the Red Sea.
In the early 1980s, drought caused food shortages and disease to peak, killing hundreds of thousands of people from West Africa to Ethiopia. Reductions in aerosol emissions after the 1980s have led to an increase in Atlantic hurricanes and increased rainfall in the Sahel. The results also show similarities in sea surface temperatures, hurricane activity and Sahel rainfall, very similar to what scientists have observed in the tropical Atlantic.
The researchers also noted that there are many factors that influence hurricane season activity, and that storms can and will occur even when overall hurricane season activity is low.
"Due to declining human-induced aerosol emissions around the Atlantic Ocean, combined with ongoing and future warming due to greenhouse gases, we believe it is unlikely that Atlantic hurricane activity will return to a lull in the decades to mid-century," he said.
The study, "Decadal variability in the tropical Atlantic governed by external forcing," was published in the September 13 issue of Nature. The study's authors include Chengfei He, Amy Clement, Lisa Murphy and Tyler Fenske of the University of Miami Rosenstiel School, Sydney Kramer and Jeremy Klavans of the University of Colorado, and Mark Cane of Columbia University.