Hurricanes and the climate – is the worst yet to come?

A few weeks ago we witnessed the dramatic saga unfold in Houston as Hurricane Harvey slammed the Texas coast. Lives were lost and entire neighborhoods vanished. According to scientists, Harvey dumped more rain than any previously recorded storm in the contiguous U.S. This week the nation braced again as Hurricane Irma swept through Florida. Are these storms just a fluke, or a sign of things to come? As a scientist who studies climate change, this question concerns me.

The International Panel on Climate Change has warned of increased storm severity due to climate change. According to its latest report, “intense tropical cyclone activity has increased in the North Atlantic since 1970” and “extreme precipitation events will become more intense and frequent in many regions.”

In 2006, a study out of the Massachusetts Institute of Technology stated that human activity is, “likely responsible for long-term trends in tropical Atlantic warmth and tropical cyclone activity.” As for climate projections, sophisticated models consistently show that greenhouse warming will cause the average intensity of tropical cyclones to become stronger globally.

To understand why hurricanes will intensify under a warmer climate you need only know that hurricanes are fueled by heat. As the climate warms and places like the Caribbean experience record breaking ocean temperatures, a normal category three or four hurricane can instead become a category four or five.

That hurricanes feed off ocean heat is a principle widely understood. As one study notes, “as climate change causes the atmosphere and, in turn, the seas to warm, the ocean stores more energy that is converted to hurricane wind.” As for extreme precipitation events, a warmer ocean also means more evaporation and more atmospheric moisture. More moisture means more rain.

A recent article in The Atlantic articulated an important difference between Harvey and its predecessors. Typically, as hurricanes grows, their winds churn up deeper, cooler water. This cool water calms and slows the storms. In the case of Harvey, deep water was churned up. However, the underlying water was still warm, not cool.

Thus, the calming effect was missing, and the storm was not weakened. Adding insult to injury, the magnitude of precipitation allowed Harvey to last longer over land because the immense flooding meant the storm could feed off its own underlying flood waters, as if still over ocean.

With Irma’s 185 mph sustained wind speeds weakening dramatically before making landfall in Florida, the U.S. dodged a bullet this month. But these “once in every 500 years” storms are becoming all too frequent, and a new super storm is likely around the corner. It is therefore imperative that we listen to the climate science.

Storms are predicted to worsen as temperatures rise, yet things can be done today to curb carbon emissions and prevent the worst. Congress has the power to rapidly shift us towards clean energy.

Citizen’s Climate Lobby, Friends Committee on National Legislation, and #PutAPriceOnIt are a few organizations that deserve credit for galvanizing such political action. If regulation seems costly, consider the cost of Harvey and Irma, or the $46 billion spent last year on U.S. climate-related disaster relief.

The 52 member House Climate Solutions Caucus, composed equally of Republicans and Democrats, suggests reason for hope. However, if Congress is to fully commit to climate action, public pressure will remain essential.

Shahir Masri, Sc.D., is an assistant specialist in air pollution exposure assessment and epidemiology at the University of California at Irvine, and also teaches at the Schmid College of Science and Technology at Chapman University. He earned his Doctor of Science and Master of Science degrees from the Department of Environmental Health at the Harvard T.H. Chan School of Public Health. He also holds a Bachelor of Science degree in Environmental Science from the University of California, Los Angeles.