- Why have hurricanes been decreasing? Give thanks to La Niña.
- Although there may be fewer tropical cyclones, the damage they cause is increasing.
- Rapidly intensifying storms appear to be on the increase.
Hurricanes – and the storms like them around the planet – have actually been decreasing worldwide over the past 30 years or so, according to a study published this week. But at the same time, the damage they cause has been increasing.
Why have hurricanes been decreasing? Give thanks to La Niña.
“We attribute this decreasing global trend to the shift toward a more La Niña-like basic state in the overall tropical climate,” study co-lead author Phil Klotzbach of Colorado State University told USA TODAY.
“While La Niña increases Atlantic hurricane activity, it tends to decrease Pacific activity,” he said. “Since the Pacific generates much more activity than the Atlantic climatologically, La Niña tends to reduce global storm activity.”
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The La Niña climate pattern is a natural cycle marked by cooler-than-average ocean water in the central Pacific Ocean. It is one of the main drivers of weather in the United States and around the world, especially during the late fall, winter and early spring.
During a La Niña, the Atlantic hurricane season tends to be more active, and the Pacific season is usually much quieter.
Although there may be fewer tropical cyclones (the umbrella term for hurricanes, typhoons and cyclones), the damage they cause is increasing, basically because we have more valuable things in the way. “We find a significant increase in global damage caused by tropical cyclones, primarily due to growth in population and wealth along the coastline,” Klotzbach said.
“The largest increase in global damage was in the Atlantic,” he said. “That is somewhat to be expected given that the Atlantic has the largest financial exposure to hurricanes.”
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This would include coastal areas of the United States.
“For example, while the Atlantic only had 11% of the global total of Category 4-5 hurricanes during our study period (1990-2021), 62% of global damage from tropical cyclones occurred in the Atlantic,” he said.
How climate change affects hurricane intensity
Other findings from the study included that rapidly intensifying storms appear to be on the increase.
Researchers found an increase in storms that intensified by 60 mph or more in 24 hours, likely because of warmer sea-surface temperatures. Some of this increase in intensity is tied to climate change-related warming, Klotzbach said.
The number of strong hurricanes is also increasing, according to the study: “While the trend is not statistically significant, we find an increasing trend in the percentage of hurricanes reaching Category 4-5 intensity,” Klotzbach said. These are the most intense storms, with wind speeds of at least 130 mph, which can produce “catastrophic” damage, according to the National Hurricane Center.
“This change toward potentially fewer storms but more strong storms is in line with what climate models project with continued climate change,” Klotzbach said.