Hurricanes will continue to become more intense

By examining data on the past four decades of hurricane activity and the conditions that shaped them, a team of researchers from Department of Energy’s Pacific Northwest National Laboratory (PNNL) has found that the U.S. Atlantic Coast is becoming a breeding ground for rapidly intensifying massive hurricanes, due to climate change and other environmental conditions that beget increasingly severe storms.

“Our findings have profound implications for coastal residents, decision- and policy-makers,” said study lead author Khartik Balaguru, a climate scientist at PNNL. “And this isn’t specific only to the Atlantic. It’s happening in several prominent coastal regions across the world.”

According to Dr. Balaguru and his colleagues, climate change is the key factor influencing the severity of hurricanes. As temperatures rise, the Earth’s surface warms, with land becoming significantly warmer than the sea. As greenhouse gases continue to build, the temperature difference between warmer land and cooler sea increases substantially. 

“Unlike the ocean with unlimited water supply, there’s much less water in soil. That means the land can’t evaporate as much water, so it can’t get rid of the extra heat trapped by greenhouse gases as quickly as the ocean,” explained study co-author Roby Leung, an atmospheric scientist at PNNL.

The higher-pressure air over the cooler sea blows inward, toward lower-pressure land areas, while the Earth’s rotation guides these winds in a cyclonic, twisting direction, thus strengthening what scientists call “vorticity” – a spinning motion of air that sucks up warm, moist air and convert its energy into damaging winds. As moist air rises inside the hurricane’s core and cools towards the top, water vapor condenses and emits heat which, in its turn, warms nearby air, causing it to ascend further, invigorating the storm. 

Although vertical wind shear can throw a wrench into this “heat engine” – as hurricanes are often described – by injecting dry air into the storm’s core, this negating force has unfortunately weakened on the Atlantic Coast over the past decades. 

“The nearshore environment has absolutely become more favorable for hurricanes near the Atlantic Coast, and that’s very consistent with the rising hurricane intensification we’ve observed in the region,” said Dr. Balaguru.

By using models depicting the consequences of climate change on these factors, the scientists found that wind shear will continue to weaken on the Atlantic Coast, while the atmospheric humidity and nearshore vorticity will increase, bringing even greater chances of wetter, faster-developing hurricanes by the end of the century. Although this research has only focused on the northern hemisphere, one could expect similar phenomena in the southern hemisphere too, Dr. Balaguru concluded.

The study is published in the journal Geophysical Research Letters.

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By Andrei Ionescu, Earth.com Staff Writer