Less dusty air “may spur hurricanes”

A decline in sun-dimming airborne dust has caused a rapid warming of the tropical North Atlantic in recent decades, Reuters reported, citing a study that might help predict hurricanes on the other side of the ocean. About 70% of the warming of the Atlantic since the early 1980s was caused by less dust, American researchers wrote in the journal Science.


Clouds of dust – from drought-affected regions, sandstorms in the Sahara or volcanic eruptions — can be blown thousands of kilometres and reflect some of the sun’s rays back into space. No ocean receives as much dust as the Atlantic.


“Since 1980 tropical North Atlantic Ocean temperatures have been rising at a rate of nearly 0.25 Celsius per decade,” the scientists wrote. Previously, the rapid temperature rise had been blamed on factors such as global warming or shifts in ocean currents. Warmer temperatures may spur more hurricanes, which need sea-surface temperatures of about 28° Celsius to form.


A sea-temperature difference of just one degree Fahrenheit (five-ninths of a degree Celsius) separated 1994 — a quiet hurricane year — from 2005; in that record year, fierce storms included Hurricane Katrina, which devastated the city of New Orleans.


“We were surprised” by the big role of dust on Atlantic temperatures, said Ralf Bennartz, a professor at the University of Wisconsin-Madison and a co-author of the study, written with experts at the National Oceanic and Atmospheric Administration. Their research suggests that only 30% of the warming of the Atlantic can be explained by factors other than dust. The effect of climate change on the amount of dust originating from Africa this century is unclear, Bennartz said.


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