Epic Hurricanes

Two record-breaking hurricanes have struck the U.S. in just a few weeks. In late August, Harvey dumped record rains on Texas. Late last week and over the weekend, Irma unleashed record winds that devastated several Caribbean islands. The storm caused flooding and widespread power outages in Florida. Another hurricane, Jose, is churning in the Atlantic now. As climate change alters the planet, will monster storms become the new normal?

Hurricanes (and their Pacific cousins, typhoons) form over the ocean. They strengthen by drawing energy from the water’s warmth. Heat energy is like fuel for a big storm. The hotter the water, the more energy the hurricane can gather.

Climate scientists think hurricanes will tend to become more intense as the planet’s average temperature rises. Using computer models, researchers can predict how much the oceans will heat up in the coming years. They can also predict how much warmer the air above the oceans will get. These models point to a future in which warmer seas will probably make for more intense hurricanes, creating bigger storms with faster winds.

Air temperature also affects the intensity of hurricanes. Warmer air can hold more water vapor. That’s why droplets form outside a cold drink on a hot day: When the air right next to your drink cools, it can’t hold as much water. The water in the cooler air condenses into liquid droplets that cling to the glass. As Earth’s temperatures increase, hurricanes will be able to hold more water. Because of this, scientists expect heavier rainfall once those storms reach land.

There’s already some evidence that hurricanes in recent years have formed more quickly, carried more precipitation, and had more total energy than those from a few decades ago. Harvey’s record rainfall may be another example of this trend.

Future storms will likely be more intense, on average. But will they also happen more often? That’s a little trickier to predict, says Paul Ullrich, a climate researcher at the University of California, Davis.

Ullrich says many climate researchers are beginning to think that hurricanes might actually form less frequently in a warmer world. Some models suggest that the bigger, more intense storms that form will absorb a lot of heat energy from the oceans—leaving behind slightly cooler waters in their wake. That could make the birth of another big storm less likely until the ocean warms up again.

As areas hit hardest by the recent hurricanes start on the long road to recovery, residents and officials all along the Atlantic coast are considering how best to prepare their homes and communities for the future. Scientists will be analyzing the data from the latest record-breaking storms in the months and years ahead to better understand what kinds of extreme weather future hurricane seasons might bring.