Hurricane Fiona, typhoons part of wetter storms caused by climate change

Hurricane Fiona, typhoons part of wetter storms caused by climate change

Powerful storms ravaged three disparate, far-flung corners of the planet this weekend, but they all had one thing in common: they were getting stronger and wetter as climate change drove them.

From Hurricane Fiona sweeping across Puerto Rico and the Dominican Republic to Typhoon Nanmadol ravaging Japan, to the remnants of Typhoon Merbok wreaking havoc in Alaska, the last 72 hours have demonstrated the devastating effects of heavy rain and flooding.

The three weekend storms contribute to a trend of wetter storms in a warmer future, said Michael Wehner, a senior scientist at Lawrence Berkeley National Laboratory.

“The worst storms will get worse,” he said.

With climate change making storms rainier and more intense, the weekend’s extreme weather events offer a glimpse of what could happen more often in the future, experts say.

One of the most pronounced ways storms have been affected by climate change in recent years can be measured in rainfall increases, said Kevin Reed, an associate professor of atmospheric sciences at Stony Brook University in New York.

As the world’s oceans warm, they provide more energy for storms, making them more intense as they form. A warmer atmosphere can also hold more moisture, Reed said.

“If you have warmer water, you have more evaporation, which means you have more moisture in the atmosphere, which means you can get more precipitation,” he said.

Up until the weekend, the Atlantic hurricane season had been unusually calm, but Reed said mid-September is usually the peak of the season, meaning other powerful storms could be on the way.

“Hurricane Fiona reminds us that while it has been relatively calm, things can change and strong storms can have a really big impact,” he added.

Image: Hurricane Fiona in Puerto Rico's Cayey (Stephanie Rojas/AP)

Image: Hurricane Fiona in Puerto Rico’s Cayey (Stephanie Rojas/AP)

Scientists have estimated that for every 1 degree Celsius increase in temperature, the atmosphere can hold 7% more evaporated moisture. The planet has warmed about 1.1 degrees Celsius since the pre-industrial era.

Hurricane Fiona, which hit Puerto Rico on Sunday and caused a power outage across the island, is already causing heavy rainfall in the region.

In an update early Monday morning, the National Hurricane Center warned of “heavy rains and catastrophic flooding” across much of Puerto Rico. Multiple locations on the island received more than 20 centimeters of rain in the past 72 hours.

A day earlier, one of the strongest storms in at least a decade hit Alaska. Remains of Typhoon Merbok brought hurricane-force winds, high seas and rain that caused widespread flooding along the coast. (Typhoons and hurricanes are both tropical cyclones, but differ in their naming conventions based on where they occur.)

Image: Flooding in Nome Alaska (Peggy Fagerstrom/AP)

Image: Flooding in Nome Alaska (Peggy Fagerstrom/AP)

And thousands of miles away in Japan, Typhoon Nanmadol became one of the most intense storms to hit the country in years. Weather stations on the island of Kyushu recorded nearly 20 inches of rain in 24 hours on Sunday, according to weather experts at Yale Climate Connections.

More than 8 million people were asked to evacuate before the typhoon made landfall. The Japan Meteorological Agency warned Monday that heavy rains, storms, high waves and storm surges are expected to continue as the storm moves along the coast. Heavy rainfall recommendations remain in effect in much of the country.

Wehner of Lawrence Berkeley National Laboratory and Reed of Stony Brook University collaborated on a paper published in April in the journal Nature Communications that examined precipitation in the 2020 Atlantic hurricane season, which was one of the most active hurricane seasons on record. They found that climate change made the entire season wetter overall, and they measured a 10% increase in rainfall during the heaviest three hours of rainfall during storms.

“That means the storm rained 10% more because of climate change than it did without,” Reed said.

This increase in extreme precipitation could be catastrophic for the people living in the areas affected by supercharged storms. In Puerto Rico, for example, communities have still not fully recovered from Hurricane Maria in 2017.

“These storms are certainly scientifically interesting,” Wehner said, “but the part of the human tragedy is much more important.”

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