Aerosols May Have Helped Suppress Hurricanes During 20th Century

Lee Rannals for – Your Universe Online

Researchers wrote in the journal Nature Geoscience that aerosols could have played a role in helping to suppress the number of Atlantic hurricanes over the 20th Century.

The scientists found that aerosols make clouds brighter, which causes them to reflect more energy back from the sun into space. This impacts ocean temperatures and tropical circulation patterns, making the conditions less favorable for hurricanes.

“Industrial emissions from America and Europe over the 20th Century have cooled the North Atlantic relative to other regions of the ocean. Our research suggests that this alters tropical atmosphere circulation – making it less likely that hurricanes will form,” said Dr. Nick Dunstone, a Met Office climate prediction scientist and lead author of the research.

He said since the introduction of the clean air-acts in the 1980s, concentrations of aerosols over the North Atlantic have reduced, which has helped increase hurricane activity.

“On the other hand, the reduction in aerosols has been beneficial for human health and has been linked to the recovery of Sahel rains since the devastating drought in the 1980s,” Dunstone said.

Dr. Doug Smith, a Met Office research fellow and co-author of the study, said there was a relatively quiet hurricane period between 1900 and 1920, and then again from 1970 to 1980. Active periods have 40 percent more hurricane activity than these quiet periods.

The researchers were able to use changes in man-made aerosol emissions in the Met Office Hadley Center model to reproduce the decade-to-decade Atlantic hurricane activity.

“This study, together with work we published last year, suggests that there may be a greater role than previously thought for man-made influence on regional climate changes that have profound impacts on society,” said Dr. Ben Booth, a Met Office climate processes scientist and another co-author of the study.

The scientists say this study will help future international research because modeling the impact of aerosols is one of the largest uncertainties in climate science. This study suggests the number of Atlantic hurricanes over the next couple of decades will depend on future aerosol emissions and how they interact with natural cycles in the North Atlantic.

The National Oceanic Atmospheric Administration (NOAA) is predicting the 2013 hurricane season will be very active. NOAA said there will be seven to 11 hurricanes hitting the Atlantic, three to six of which could turn into major storms with winds 111 mph or higher.

Experts say higher than average water temperatures in the Atlantic and Caribbean Sea are one of the major factors for their 2013 prediction.

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