This Year’s Wild Hurricane Season Is an Ominous Sign of What’s Ahead

Sea surface temperatures must be 82°F or warmer to form and sustain tropical cyclones

By Mira Rojanasakul and Brian K. Sullivan

December 5, 2020, 7:00 AM EST

This year’s record-breaking Atlantic hurricane season officially ended Nov. 30, but the procession of violent storms it unleashed foreshadows a dark future fueled by climate change.

A combination of warmer oceans, weather patterns triggered by La Nina and an unusually busy African monsoon season led to the 30 tropical storms and hurricanes that formed in 2020—more than double the long-term average. A record 12 hit the U.S., and 10 abruptly exploded in strength and became more deadly as they approached land, which Yale Climate Connections meteorologist Jeff Masters says could be a grim omen for what lies ahead.

“We have entered a new climate,” Masters said. “Heat is energy and when everything else comes together and you get that heat there, then things are going to go bonkers.”

Total number of Atlantic storms per year, 1950–2020 👆

Source: NOAA

The year produced so many storms that forecasters exhausted the names on the official list and had to resort to the Greek alphabet to designate new ones. That’s only happened once before, in 2005, and 2020 went much further into the roster.

One of the drivers this year has been La Nina, the Pacific Ocean pattern that can affect weather around the world. It grew stronger than expected, shutting down wind shear across the Atlantic that can stop storms from growing, said Phil Klotzbach, lead author of the Colorado State University seasonal hurricane forecast.

Hurricanes draw their strength and power from warm ocean temperatures, and 2020 had the highest average sea surface temperatures on record.

Source: Phil Klotzbach analysis of NOAA data

In the U.S. more than 60 million people live in the path of hurricanes. Some of the fastest growing counties lie along the vulnerable Gulf Coast, which was struck nine times this year, and as many as 7.3 million homes are at risk from storm surge along the U.S. Atlantic and Gulf coastlines, according to CoreLogic.

With storms able to hold more moisture in a warmer climate and sea-levels rising, people along the coasts in the U.S., Mexico, the Caribbean and Central America are facing increased risks from Atlantic storms, said Katherine Klosowski, vice president and manager of natural hazards at insurer FM Global.

While 2020 didn’t see a storm as catastrophic as 2005’s Hurricane Katrina, which killed 1,800 people and cost $125 billion in damage, the unprecedented season still wreaked havoc from Nicaragua to New York.

The 2020 Atlantic hurricane season produced 30 named storms—the most going back to at least 1851.

A record 12 of those made landfall in the contiguous United States.

There was another strange phenomenon this year: Louisiana, Mexico, Nicaragua and Honduras all took repeat blows as some storms followed similar paths.

Also unusual was the number of systems that rapidly intensified as they neared the coastline. To meet the criteria, a storm’s winds must strengthen by about 35 miles per hour in 24 hours. It makes meteorologists worry that climate change is imbuing hurricanes with added intensity, making them more ferocious in the years ahead.

In Central America, back-to-back hurricanes killed hundreds, displaced thousands and decimated crops. In the U.S., Hurricane Isaias left more than 1 million people in the Northeast without power for up to a week, while Hurricane Laura essentially wiped whole towns off the Gulf Coast.

U.S. damages alone likely totaled $66 billion, according to Chuck Watson, a disaster modeler at Enki Research.

Future seasons are likely to produce more powerful storms, but 2020’s record number may not be broken again soon.

“I don’t think that’s something we necessarily expect to see more of in the future,” Klotzbach said. “Climate change’s impacts on hurricanes appear to be more in increasing their intensity than their frequency.”

While the official season runs from June 1 to November 30, the Atlantic started spawning storms in May and there’s a good chance it will continue through December.

“We have a whole month to go,” Masters said.