Extensive research shows how increasing greenhouse gas concentrations amplify deadly storms, droughts and heat waves, but reducing them along with other industrial pollution emissions will also affect global weather.

The effects of emission reductions have been studied less than the increase, but understanding how the climate responds to such reductions is also crucial to protect people from extreme climatic factors such as floods, heat, droughts and cyclones.

New research NOAA, published today in Science Advances, shows that the rise and fall of industrial soot – aerosols – play a crucial role in the activity of tropical storms around the world. The study found some twists that should be of interest to politicians, the study’s author said Hiruyuki Murakamiresearcher of tropical storms in the NOAA Geophysical Hydrodynamics Laboratory.

Aerosols often form a reflective shield in the atmosphere that can hold heat higher but reduces the amount of heat that reaches the planet’s surface. Murakami’s modeling study shows that a 50 percent drop in air pollution in Europe and North America between 1980 and 2020 led to warming of the surface of the tropical Atlantic Ocean, where cyclones rose 33 percent over the same 40-year period. he said.

“Reducing air pollution does not always reduce the risk of tropical cyclones,” he said, adding that climate policy should take into account the pros and cons of various impacts from reducing industrial pollution. If policies to reduce greenhouse gas emissions succeed quickly, it could further reduce aerosol pollution, leading to more heating and tropical storm activity.

Princeton University climate researcher and tropical storm expert Gabrielle Centurywho was not involved in the study said the study helps provide a more holistic global picture of how changes in aerosol levels affect tropical storms.

“Given the role that aerosols play in global and regional temperatures, hydroclimates and Atlantic tropical cyclones, it makes sense that they could have a significant impact on the global activity of tropical cyclones,” he said. “Research shows well … that aerosols have contributed to the redistribution of tropical cyclone activity – increasing it in some places and decreasing it in others.”

The study shows that aerosol exposure is not isolated from the Atlantic, he said, but includes a global shift. He noted that aerosols are among the most volatile elements of the climate system, so he expects further research to study the uncertainties associated with their effects.

The study of aerosols and tropical storms helps explain when and where these storms are expected to cause significant damage, allowing citizens and governments to prepare for it, he said.

Murakami said he found the aerosol’s fingerprints by changing the levels and patterns of human emissions in his model, leaving other climatic factors unchanged. The study did not count how much the reduction in aerosols increased ocean warming and tropical storms, he said.

Reducing pollution in the Northern Hemisphere has also helped increase the activity of tropical storms in the Atlantic by changing major wind patterns, he said.

As the number of aerosols decreases the general warming of the surface in medium and high latitudes pushes the jet stream, a band of strong winds blowing from west to east, about 5-9 miles in the atmosphere, to the pole. As these westerly winds weaken over the tropical Atlantic, where many major hurricanes form, he said, surface conditions are more conducive to the development and strengthening of tropical cyclones.

Aerosols have a different effect on hurricanes. And 2020 paper in Geophysical Research Letters found that they doubled rainfall and lightning in urban areas around Houston during Hurricane Harvey, which flooded the area with record rains.

And a The 2021 study in Nature Communications looked back and found that the drop in hurricane activity from the 1960s to the 1980s was probably due to an increase in the number of aerosols at a time when industrial air pollution peaked.

Century said that in the future he expects the greenhouse gas warming effect to become more dominant compared to aerosols.

“Given the relatively short lifespan of aerosols in the atmosphere, as aerosol emissions decrease, the impact of greenhouse gases should become more and more apparent,” he said.

Regional nuances of impact

At the same time, the reduction in pollution in Europe and North America has had the opposite effect on the southern hemisphere, where it has dampened tropical storm activity. The northern hemisphere heats up faster than the southern hemisphere, and as warm air rises, this rising contrast causes more air to rise north of the equator, Murakami said, causing a downward flow of air in the southern hemisphere that slows a tropical cyclone. formation.

Rapid growth in industrial pollution in Asia, especially in China and India, is likely to have also played a significant role in reducing tropical storm activity in the western North Pacific, where typhoons threaten vulnerable island nations as well as Okinawa, Japan and China.

“The important thing is that as the number of aerosols in China and India increased, people did not pay much attention to the effect,” Murakami said. “We’ve clearly found that aerosols reduce the number of tropical cyclones in the western North Pacific.” The effect is the “reverse side” of what is happening in the Atlantic, he said, air pollution is a “key ingredient” for a 14 percent reduction in tropical cyclones in the North Pacific from 1980 to 2020.

“This study shows that reducing air pollution increases the risk of tropical cyclones occurring in the North Atlantic,” he said. “It could also happen if air pollution decreases rapidly in Asia.”

Deep dives into the connection between aerosols and hurricanes are helpful, he said Jim CosinHurricane expert and senior scientist s Climate Servicewhich provides financial climate risk analysis for governments and businesses.

“At this point, any changes we make will have some impact on the climate and local tropical cyclones,” he said. “We know that the reduction of aerosols in the Atlantic has contributed to an increase in frequency and maximum intensity. There are a lot of things that are not good to increase. ”

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Extreme climatic events caused by global warming are increasing globally, and in the United States hurricanes and tropical storms were by far the deadliest and most harmful between 1980 and 2021, killing 6,697 people and causing more than $ 1.1 trillion in losses. that’s more than half of $ 2.1. trillions of total damage from all weather and climate cataclysms over this time period, reports National Oceanic and Atmospheric Administration.

Cosin said for decades, cooling aerosols have masked the greenhouse gas warming effect that amplifies tropical storms.

“But there is no more credit,” he said. “Now we pay the bagpipes. Now it’s coming back to us. “


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