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Hurricanes are strengthening faster than they did 30 years ago

The main cause appears to be a natural climate phenomenon that warms the seawater where hurricanes typically intensify in the Atlantic, according to a study.
Credit: NASA/NOAA GOES Project via Getty Images
In this NASA/NOAA handout image, NOAA's GOES satellite shows Hurricane Irma (C) in the Caribbean Sea, Tropical Storm Jose (R) in the Atlantic Ocean and Tropical Storm Katia in the Gulf of Mexico taken at 15:45 UTC on September 08, 2017.

With the start of hurricane season just three weeks away — and memory of last year's disastrous storms still fresh — scientists reported that powerful hurricanes are strengthening faster than they did 30 years ago.

Four of the monster hurricanes last year (Harvey, Irma, Jose and Maria) all intensified rapidly — when the maximum wind speed increases at least 29 mph within 24 hours.

Maria was an extreme example on Sept. 18 — roaring from a Category 1 (90 mph) to a Category 5 (160 mph) in under 18 hours.

According to a study out this week, the main cause appears to be a natural climate phenomenon that warms the seawater where hurricanes typically intensify in the Atlantic.

Hurricanes get their strength from warmer ocean water. The warmer the upper ocean, the more powerful a hurricane can become.

In the study, researchers analyzed 30 years of satellite hurricane data, from 1986 through 2015. Although scientists said rapid intensification is not happening more often, hurricanes that do intensify rapidly do so more quickly and get stronger.

The natural climate cycle, known as the Atlantic Multidecadal Oscillation (AMO), governs how the temperature of north Atlantic Ocean swings between warmer and cooler, with each period typically lasting a decade or more. The AMO has generally been in its warm phase since the late 1990s.

"This was a surprise, that the AMO seems to be a bigger influence in rapid intensification than other factors, including overall warming," said lead author Karthik Balaguru of the Pacific Northwest National Laboratory.

The study also said, "The role of (man-made) climate change cannot be ruled out."

Scientists said the average boost in wind speed during a 24-hour intensification is about 13 mph more than it was in the late 1980s.

Penn State climate scientist Michael Mann, who was not involved in the study, told The Washington Post that the study’s attribution to this cycle, rather than human activity, was “not justified.”

The study was published in Geophysical Research Letters, a publication of the American Geophysical Union.

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