Hurricanes are intensifying faster than ever due to climate change


Hurricane Ian is rapidly gaining strength in the Caribbean as it passes over ultra-warm Caribbean and Gulf of Mexico waters. The National Hurricane Center had predicted the system would quickly go from a tropical storm to at least a Category 4 hurricane in less than 72 hours.

It’s a unprecedented forecastexperts told CNN, but according to one scientist, it is becoming more likely as the climate crisis progresses, pushing ocean temperatures higher and setting the stage for tropical storms to erupt at a breakneck pace in major killer hurricanes.

Rapid intensification is precisely what it sounds like – the winds of a hurricane building up rapidly over a short period of time. Scientists have defined it as an increase in wind speed of at least 35 mph in 24 hours or less.

The phenomenon unfolded at breathtaking speed in the Philippines this weekend. Super Typhoon Noru exploded in force on its final approach to the Pacific island nation, dropping from the equivalent of a Category 1 hurricane to a Category 5 overnight while Manila residents slept.

Noru’s rapid intensification just before landfall – which was not expected – likely meant residents had no time to prepare for the much stronger storm.

Hurricane Ian has been in the forecast for days, giving Cuba and Florida the advantage of the weather. Winds from the storm increased from 45 mph Sunday evening to 80 mph late Monday morning, and further strengthening is expected. Ian could step up to at least a Category 4 before he makes landfall in Florida midweek.

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

That’s “kind of on the extreme of how quickly storms can escalate,” Wing told CNN. “Only about 6% of all forecast periods are associated with these types of observed rapid intensification rates. And so this is something that is by definition, a rare event. Sometimes it only happens a few times a season.

Live updates: Florida prepares for Hurricane Ian

But man-made climate change stacks the deck in favor of more intense storms. So not only do they generate more precipitation and larger storm surges, but they are also more likely to be stronger and escalate faster.

“Climate change is increasing both the maximum intensity these storms can reach and the rate of intensification that can take them to that maximum,” said Jim Kossin, senior scientist at the Climate Service. “The escalation rates at Noru and Ian are good examples of very rapid escalation, and there have been many more recently.”

Two ingredients must come together for a rapid escalation to occur, Kossin told CNN. The first is that the upper level winds around the hurricane must be weak – strong winds can keep a storm from intensifying or even tear a storm apart.

The second is that warm ocean water must extend well below the surface, up to hundreds of feet deep, to provide enough fuel for the hurricane to grow stronger.

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

Scientists have shown that humans are the main cause of the relentless warming trend. Global warming emissions from fossil fuels 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 increase in temperature.

And much of that warming has happened in the upper layers 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 the kinetic energy that is the winds,” Masters told CNN. “So if you increase the amount of thermal energy in the ocean by heating it up, you’re going to increase not only the maximum intensity that they can get, but also the rate at which they reach that maximum intensity.”

A 2019 study found that Atlantic hurricanes in particular exhibited a “very unusual” increase in rapid intensification from the 1980s to the early 2000s – a trend that could only be explained by climate change in human origin. And, worryingly, scientists have found that the biggest changes occur in the strongest storms, making the most life-threatening hurricanes even more dangerous.

“Climate change increases the odds that you’ll get a fast intensifier,” Masters said.

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

Forecasters are better able to see signs of this phenomenon before it happens, giving coastal residents more time to prepare for the worst.

Kossin said there were several reasons for this. The first is that meteorologists are increasingly confident in computer forecasting models, which are improving at seemingly light speed. The other is that they have seen more extreme cases of rapid escalation in recent years, which makes it easier to predict them going forward.

Masters told CNN that all adds up to better predictions.

“The forecast is unprecedented primarily because the [National] Hurricane Center is getting better at its job,” Masters said. Weather models “have improved so much. And our forecasting techniques are improving.

Teresa H. Sadler