Climate crisis causes hurricanes to intensify rapidly, experts say

Hurricane Ian is rapidly strengthening in the Caribbean as it passes through the region’s ultra-hot waters and the Gulf of Mexico. The National Hurricane Center predicted that the system would rapidly intensify from a tropical storm to at least a Category 4 hurricane in less than 72 hours.

It’s an unprecedented prediction, experts told CNN but one scientist says it is becoming more likely as the climate crisis progresses, raising ocean temperatures and laying the groundwork for tropical storms to explode at breakneck pace into deadly major hurricanes.

Rapid intensification is exactly what it sounds like — the winds of a hurricane rapidly building up in a short period of time. Scientists defined it as an increase in wind speed of at least 56 km/h in 24 hours or less.

The phenomenon occurred with shocking speed in the Philippines this weekend. Super typhoon Noru exploded in force on its final approach towards the Pacific island nation, going from the equivalent of a Category 1 hurricane to a Category 5 hurricane overnight as residents of Manila slept.

Noru’s rapid intensification just before landfall — which was unforeseen — likely meant that residents didn’t have time to prepare for the much stronger storm.

Hurricane Ian has been forecast for days, giving Cuba and Florida the benefit of time. Winds in the storm increased from 72 km/h on Sunday night to 128 km/h in the late morning of Monday (6), and more strengthening is in the forecast. Ian could step up to at least a Category 4 before arriving in Florida midweek.

Rapid intensification has historically been a rare phenomenon, according to Allison Wing, assistant professor of atmospheric science at Florida State University.

“It’s really the extreme of how quickly storms can intensify,” Wing told CNN . “Only something like 6% or more of all forecast time periods have these types of observed rapid intensification rates associated with them. And so it’s something that is, by definition, a rare event. Sometimes that only happens a few times a season.”

But man-made climate change is stacking the deck in favor of more intense storms. So not only are they generating more rain and bigger storms – they are also more likely to be stronger and are intensifying faster.

“Climate change is increasing both the maximum intensity these storms can reach and the rate of intensification that can drive them to that maximum,” said Jim Kossin, senior scientist at the Climate Service.

“The rates of intensification in Noru and Ian are good examples of very rapid intensification, and there have been many more recently.”

Two ingredients must come together for rapid intensification to occur, Kossin told CNN . The first is that the higher level winds around the hurricane need to be light – strong winds can stop a storm from intensifying or even destroy a storm.

The second is that warm ocean water must extend well below the surface, reaching hundreds of meters deep, to provide enough fuel for the hurricane to strengthen.

More than 90% of global warming over the past 50 years has occurred in the oceans, according to the National Oceanic and Atmospheric Administration. The last five years have been the warmest on record for the world’s oceans.

Scientists have shown that humans are the dominant cause of the relentless warming trend. Emissions from fossil fuels that warm the planet trap heat in the atmosphere, creating an energy imbalance. The oceans, in turn, absorb 90% of the excess heat, which has led to an alarming rise in temperature.

And much of that warming has taken place in the upper levels of the ocean, where hurricanes get their energy, said Jeff Masters, a meteorologist at Yale Climate Connections.

“Hurricanes and typhoons are heat engines, which means they take heat energy from the oceans and convert it into kinetic energy which is the winds,” Masters told CNN .

“So if you increase the amount of heat energy in the ocean by heating it, you will increase not only the maximum intensity they can get, but also the rate at which they reach that maximum intensity.”

A 2019 study found that Atlantic hurricanes, in particular, showed a “highly unusual” increase in rapid intensification from the 1980s to the early 2000s — a trend that could only be explained by human-caused climate change.

And worryingly, scientists found that the most significant changes were happening with the strongest storms, making the most life-threatening hurricanes even more dangerous.

“Climate change increases the chances that you will get a quick enhancer,” said Masters.

Some of the most devastating recent hurricanes in the United States have been those that rapidly intensified just before making landfall — something Hurricane Ian is not expected to do. More recently, Hurricane Ida in 2021 strengthened from a Category 1 to a strong Category 4 in the 24 hours before hitting Louisiana and leaving a trail of destruction in its wake from the Gulf Coast to the northeast.

Meteorologists are getting better at seeing signs of this phenomenon before it happens, giving people along the coast more time to prepare for the worst.

Kossin said there are several reasons for this. One is that meteorologists are becoming more reliant on computer forecasting models, which are improving at the seemingly speed of light. The other is that they’ve seen more extreme cases of rapid escalation in recent years, which makes it easier for them to predict the future.

Masters told CNN that all contribute to better forecasts.

“The forecasts are unprecedented primarily because the National Hurricane Center is getting better at its work,” said Masters. Climate models “have gotten a lot better. And our forecasting techniques are improving.”