The ocean breathes, and hurricanes swing on its breath like on a seesaw. In the North Atlantic, there is a slow rhythm: the water alternately warms and cools, with each phase lasting twenty to thirty years. When the water is warm, more hurricanes are born. One scientist calculated that during warm decades there were on average 22.5 hurricanes, compared with 17 during cold ones. Warm water acts as fuel for storms, giving them more energy.
But a storm's strength is only half the story. Where it goes matters just as much. When the Pacific shifts into its cold phase (La Niña) while the Atlantic remains warm, hurricanes more often reach land. In such seasons, hurricane winds were stronger: up to 165 and 170 knots, compared with up to 155 knots during the Pacific's warm phase. That is the difference between torn-off roofs and demolished houses.
Atlantic water temperatures are rising faster than models predicted. In 2023, the water was as warm as models had expected only by 2040. That means the seesaw is swinging harder, and the next warm period could bring hurricanes unlike any we have seen. From 2020 to 2023, five major hurricanes struck the United States, whereas only three had hit during the entire previous period. Now meteorologists understand how the two oceanic rhythms combine, allowing them to issue better warnings.
From 2020 to 2023, five major hurricanes of category 3 or higher struck the United States, compared to three over the entire previous decade.
In Kim Stanley Robinson's novel 'Forty Signs of Rain', climate scientists try to predict abrupt changes in ocean currents and their weather impacts, echoing efforts to link slow ocean oscillations to hurricane activity.