Reduced aerosol pollution has led to more North Atlantic hurricanes, study finds

Reduced aerosol pollution has led to more North Atlantic hurricanes, study finds

A new study published Wednesday in the journal Science Advances found that over the past four decades, a 50% decrease in aerosols – tiny particles of air pollution – in North America and Europe has led to a 33% increase of the number of tropical cyclones in the North Atlantic.

On On the other side of the world, the study found that a 40% increase in aerosol pollution in China and India over the same period led to a 14% drop in the number of tropical cyclones in western North Pacific. Air pollution increased significantly in China and India during this period due to the economic and industrial growth of the countries.

“Reducing aerosol emissions is good for human health, but on the other hand, we have found that there are adverse effects when we reduce aerosol emissions – and that is the ‘hurricane activity,” said Hiro Murakami, the study’s lead author and a scientist. at the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory, CNN told CNN.

Aerosols are not like greenhouse gases. They are tiny particles of pollution that float in the air and, unlike carbon dioxide or methane, which absorb sunlight and cause warming, reflect sunlight back into space, which has an effect cooling. There are natural aerosols, but much of the pollution in the early to mid-20th century came from sources such as industrial smokestacks and car exhaust.

Murakami found that as aerosol pollution decreased in the decades following the U.S. Clean Air Act and similar actions in Europe, the ocean could absorb more sunlight, leading to temperatures of warmer sea surfaces that fueled more storms.

Murakami warns that his results don’t mean we should stop monitoring air pollution. Reducing aerosol emissions is a bit like quitting smoking, he said. When a person quits smoking, they improve their health and can prevent cancer. But in some cases, quitting smoking also comes with side effects, including weight gain and feeling stressed.

“The decrease in aerosols is actually similar,” he said. “The decrease in aerosols can lead to good health, but on the other hand, the risk of a hurricane increases. This is where the good things come with the bad things. It’s kind of like the pros and cons .”

Jim Kossin, a senior hurricane scientist at the Climate Service who reviewed the research, said the study is important in helping to distinguish how storms respond to air pollution versus greenhouse gases.

“Tropical cyclones are pretty random animals, and they react to the random nature of the atmosphere at any given time,” Kossin told CNN. “But certainly this constant ocean warming that’s happening in the Atlantic due to the combination of increasing greenhouse gases and decreasing particulate pollution, which has a profound effect – and the Changes in particulate pollution have a much more dramatic effect on hurricanes.”

Other scientists not involved in the study told CNN the findings are consistent with what they know about the complex nature of air pollution and add to the growing body of research on the how the climate crisis can influence hurricanes.

“This study shows very well that the impact of aerosols is not isolated to the Atlantic, but involves a global change in the distribution of tropical cyclones,” Gabriel Vecchi, professor of climate and geosciences at the Institute, told CNN. Princeton University. “Aerosols are among the most uncertain elements of the climate system, so I think there should be – and I predict there will be – follow-up studies that explore the sensitivity of the results to a range of uncertainties. related to aerosols.”

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Tom Knutson, a senior scientist at NOAA’s Geophysical Fluid Dynamics Laboratory who was not involved in the study, said aerosol pollution is another important way humans have altered hurricane activity. over the past 40 years.

“It’s like the aerosols create a kind of vacation because of the hurricanes in the Atlantic, but then when we reduce the aerosol forcing, it kind of comes back,” Knutson told CNN. “We think there are several things going on in the Atlantic and this paper is one that attempts to unravel the relative influence of these different things.”

Murakami said he expects aerosol pollution to remain stable, so greenhouse gas emissions will begin to have a stronger influence on hurricanes over time, particularly on their intensity.

“Climate science is very complex and it’s a work in progress, especially for hurricane activity,” Murakami said. “What we have seen over the past 40 years may not apply in the future, so we may see something very different.”

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