Hurricanes Emit Heat to Space, Helping to Cool the Planet
As global warming causes the world to get hotter, hurricanes are projected to get stronger and wetter. Yet the relationship between the climate and those massive storms goes both ways. Counterintuitively, hurricanes cool down the ocean surface, allowing the earth to emit more heat to space, according to a new study led by researchers at Princeton.
While the association between hurricanes and cooling might sound surprising, it makes sense when looking at how the planet behaves as a whole, said lead author Gabriel Rios, a doctoral candidate in atmospheric science in Princeton’s Program in Atmospheric and Oceanic Sciences. “Hurricanes might be one method the earth uses to try to regulate change and keep the amount of energy in the system constant.”
Scientists know a lot about how various climate factors like humidity, season, and sea surface temperature affect the frequency and intensity of hurricanes, which are also known as tropical cyclones. But less research has been conducted on what effect these energy-intensive events exert on the atmosphere and ocean, Rios said.
“It’s like throwing a rock into a pond,” he said. “Maybe it’s small, but the rock is going to create ripples, and those ripples are going to change the pond.”
In the new study, just published in the Proceedings of the National Academy of Sciences, Rios and his colleagues in the Vecchi Research Group – led by HMEI faculty director Gabe Vecchi – developed a model-based method that allowed them to create climate scenarios with and without hurricanes. They compared the results of the two models to discern hurricanes’ effect on climate.
The findings suggest that hurricanes exert a cooling effect through several mechanisms. They stir up colder water and bring it to the ocean’s surface, dropping its mean annual temperature by about a tenth of a degree Celsius. They also dry out the atmosphere and reduce high-altitude cloud cover. Together, these changes increase the amount of heat emitted to space by up to 3 Watts per meters squared in areas with hurricane activity, resulting in net cooling.
Because these findings are based on models, they should be considered both hypothetical and preliminary, Rios said. But they do have real-world implications. Major climate models that are used to predict global warming are run at too coarse a resolution to take the effects of hurricanes on the climate into account, he explained. But their study suggests that hurricanes could be having a discernible effect on temperature, cloud cover and moisture distribution, with potential implications for global rainfall and how energy is transported to areas without direct impacts from hurricanes. “The takeaway is that there’s a value to using these higher-resolution climate models,” Rios said. “Otherwise, we might be missing phenomena that impact climate projections.”
Many questions remain, Rios added, including how hurricanes change the climate overall, and whether they will continue to increase in frequency as climate change brings warming temperatures and higher levels of carbon dioxide—or whether they will somehow self-regulate, as the new findings suggest.