Is climate change generating stronger, more frequent typhoons?

Thanks to ocean warming, over the past 40 years tropical cyclones in East and Southeast Asia have increased – both in strength and frequency, say scientists. 

Bullit Marquez/AP
Commuters and motorists navigate heavy monsoon rains inundating low-lying areas in Manila, Philippines, on Aug. 26. Typhoons that slam into land in the northwestern Pacific – especially the biggest tropical cyclones of the bunch – have gotten considerably stronger since the 1970s, a new study concludes.

Warming waters are producing increasingly powerful typhoons, according to a new study from the University of North Carolina at Chapel Hill.

Ocean warming has already left a clear mark on marine biodiversity, causing coral bleaching and altered animal behavior. But a new study, published Monday in the journal Nature Geoscience, emphasizes the impact of warming waters on coastal communities. In the last 40 years, researchers say, tropical cyclones in East and Southeast Asia have increased – both in strength and frequency – as a result of the climatological trend.

“It is a very, very substantial increase,” lead author Wei Mei, a professor of marine sciences at UNC, told the Guardian. “We believe the results are very important for east Asian countries because of the huge populations in these areas. People should be aware of the increase in typhoon intensity because when they make landfall these can cause much more damage.”

Both “typhoon” and “hurricane” refer to rotating storm systems that form over tropical waters – the only difference is location. Hurricanes strike the Atlantic Ocean, while typhoons occur in the Pacific Ocean. Both can devastate island and coastal communities with heavy rains and winds surpassing 74 mph.

Research: Allison Terry, Elizabeth Barber; Graphic: Jake Turcotte

Warm surface water can worsen the effects of these storms. When a system approaches land, it picks up heat from coastal waters, adding energy which fuels the storm further.

“If you have warming coastal water, it means that typhoons can get a little extra jolt just before they make landfall,” Kerry Emanuel, an MIT meteorologist who wasn’t involved in the study but provided data to researchers, told the Verge. “And that's obviously not good news.”

Using data from Hawaiian and Japanese weather centers, Dr. Mei and his colleagues compared recent warming against the development of Pacific storms. The team found that typhoons in East and Southeast Asia have intensified by nearly 15 percent since the 1970s, which translates to a 50 percent rise in potential destructive power. Researchers also found that the annual proportion of typhoons that reach category 4 and 5, which can reach wind speeds of more than 150 mph, has more than doubled.

Research: Allison Terry, Elizabeth Barber; Graphic: Jake Turcotte

But is this worsening trend a function of climate change? Possibly, but it’s hard to say.

The new study is based on just 40 years of data, which isn’t enough to confirm a long-term climatological cause. That’s why Mei and colleagues chose to focus on a regional warming trend, rather than the global one.

“We want to give the message that typhoon intensity has increased and will increase in the future because of the warming climate,” Mei said. “Understanding intensity change is very important for disaster preparation.”

But climate models do predict that Earth’s oceans, including the northwest Pacific, will continue to warm in coming years. So whether or not climate change has already caused stronger tropical storms, it likely will in the future.

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