Hurricane Fiona is harbinger of climate future

For the second time in five years, Puerto Rico has been blasted with a massive hurricane, causing widespread flooding and power outages, and the increasing severity of these storms is caused by climate change, according to studies.

The island, a U.S. territory that hasn't fully recovered from 2017's Hurricane Maria, was hit by Hurricane Fiona on Monday. Parts of Puerto Rico received 30 inches of rain, causing landslides and overflowing rivers. Some rural roads have become impassable and stranded residents. As of Tuesday morning, 1.17 million of Puerto Rico's 1.47 million utility customers were without electricity, according to estimates from

Hundreds of Puerto Ricans have been forced from their homes, and the storm is now gaining strength as it has moved eastward to the Dominican Republic and north to Turks and Caicos. The U.S. National Hurricane Center warned of "life-threatening" flooding in those nations on Tuesday. Now a Category 3 storm, with winds reaching 115 miles per hour, it has caused deaths in Puerto Rico, the Dominican Republic and Guadeloupe.

The Caribbean has always experienced hurricanes in late summer, but all storms have become more intense, on average, as a result of global warming. For each additional degree Celsius (1.8 degrees Fahrenheit) of temperature, the air holds 7% more moisture. More water in the air leads to stronger storms. According to NASA the average global temperature has risen 1.1 C (2 F), since the Industrial Revolution, as humans have emitted heat-trapping gasses by burning fossil fuels.

Storms are also made stronger by warmer ocean temperatures, which provide the energy that powers hurricanes.

A research paper published in April in the journal Nature Communications examined rain in the 2020 Atlantic hurricane season, one of the most active hurricane seasons on record, and found that climate change caused a 10% increase in rainfall during the heaviest three-hour period of storms. Hurricanes are also featuring faster wind speeds, according to NASA.

Last year, a study of satellite images going back to 1979, published in Proceedings of the National Academy of Sciences, showed climate change caused the chance that a hurricane would reach Category 3 or higher to increase by roughly 8% each decade. A Category 3 hurricane is defined as one with sustained winds of at least 110 miles per hour.

"The trend is there and it is real," James P. Kossin, a researcher with the National Oceanic and Atmospheric Administration and the lead author of the study, told the New York Times. "There's this remarkable building of this body of evidence that we're making these storms more deleterious."

It's not that more rain will necessarily fall in total over the course of a year, but that rain is becoming more concentrated in specific extreme events, in between which many areas of the world are experiencing devastating droughts. (Current drought-stricken areas include the American West, much of Europe and the Horn of Africa.)

That's why, in the last few decades, a higher proportion of total precipitation has come from extreme single-day heavy rains. Other parts of the United States have recently experienced this phenomenon, which can lead to deadly flash floods. Earlier this summer, three different areas were hit with "1-in-1,000-year rains" — a name derived from the fact that they are only expected to occur once in 1,000 years, on average — in one week. Southern Illinois received 8 to 12 inches of rain in 12 hours. Six to 10 inches of rain fell in seven hours in St. Louis and up to 14 inches of rain were recorded in eastern Kentucky, causing 39 deaths.

According to data from the U.S. Global Change Research Program, the Midwest gets 42% more heavy precipitation events per year than it did 60 years ago and the Northeast gets 55% more.

Alaska was battered by a typhoon on Friday, washing away roads and causing power outages. The floodwaters began to recede on Sunday.

"For years, scientists have expressed concern that climate change has set the stage for greater impacts from large nontropical cyclones in Alaska," the Washington Post noted.

Calling the storm “unprecedented,” Gov. Mike Dunleavy, a Republican, declared an emergency on Saturday in the face of the storm.

It may have been unusual in the past, but coastal areas from Alaska to Puerto Rico should expect more extreme storms will be headed their way in the future.

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