Expect more intense hurricanes as the world heats up, say scientists

A warmer world makes hurricanes more dangerous. Scientists say that they are wetter, have more energy, and intensify faster.

Their storm surges are more destructive because climate change has already made the sea soar. And lately, storms seem to slow down more often and thus shed more rain.

Study after study shows that climate change in general worsens hurricanes. But determining the role of global warming in a specific storm such as Hurricane Florence or Typhoon Mangkhut is not so simple – at least not without detailed statistical and computer analyzes.

The Associated Press consulted 17 meteorologists and scientists studying climate change, hurricanes, or both. Some experts remain cautious about assigning global warming to a single event, but most scientists clearly see the human hand in Florence.

Global warming did not provoke Florence, they say. But this makes the system a greater danger.

"Florence is yet another poster child for man-made storms that are becoming more and more common and destructive as the planet heats up," said Jonathan Overpeck, Dean of the United States. Environmental School of the University of Michigan. He said the risk extends beyond the Atlantic Ocean, like Typhoon Mangkhut, which hit the Philippines on Friday.

For years, when asked about climate change and specific weather events, scientists would refrain from making clear connections. But in recent years, the new field of attribution studies has allowed researchers to use statistics and computer models to try to calculate how events would be different in a world without climate change. human origin.

A few months after Hurricane Harvey, studies have shown that global warming significantly increases the likelihood of record heavy rain from Harvey.

"It's a bit like a plot of" Back to the Future ", where you're traveling in another reality" plausible but without humans changing the climate, "said Peter Stott, a research scientist in the field of climate change. 39, University of Exeter, pioneers of the field.

A report from the National Academy of Sciences estimates that these studies are generally credible. A team of scientists tried to do a similar analysis for Florence, but the outside experts were suspicious because they were based on forecasts and not on observations and did not use enough computer simulations.

As the world heats up and science progresses, scientists become more specific, even without attribution studies. They cite basic physics, the latest research on storms and past studies, and bring them together for something like Florence.

"I think we can say that the storm is stronger, wetter and more impactful from the point of view of coastal flooding than it would have been caused by man-made warming," writes Michael Mann, a climatologist with Pennsylvania State University. "And we do not need an attribution study to tell us in my opinion." We just need the laws of thermodynamics.

Georgia Tech climatologist Kim Cobb is not limited to basic physics, but to all peer-reviewed studies that specifically link climate change to wetter storms.

"We have solid data across decades of rainfall records to determine attribution – climate change is increasing the frequency of extreme precipitation events," Cobb said.

Several factors make scientists more confident in showing the finger of climate change in Florence.

For each degree of air warming, it can hold up to 4% more water (7% per degree Celsius) and provide much better energy to the storm, according to scientists.

"The amount of water coming out of hurricanes is certainly the strongest connection we have," said Jim Kossin, a climatologist with the National Oceanic and Atmospheric Administration.

For Florence, "it is very likely that climate change has warmed the ocean so that the intense rains of the hurricane are more destructive than without global warming," said Jeff Masters, former director of meteorology.

The warmer air and water also make the storms stronger or stronger, Stott said.

A Kossin study conducted this year showed that tropical cyclones – a category with hurricanes and typhoons – move more slowly and even more slowly. Kossin said, "This is happening much more than before." Several studies acknowledge that climate change is to blame but that their conclusions differ slightly.

With the emergence of Florence, a place in the United States was inundated with a hurricane stuck for four consecutive years, said Hal Needham, a storm surge specialist.

Kossin and Overpeck also pointed out that studies show that storms are intensifying faster than before.

Just like in Hurricane Sandy, scientists said it was clear that storm surges were worsened by sea level rise because the power of 6 to 10 feet from Water is adding to past decades. An extra 8 inches or so can make the difference between staying dry or damaged, said Masters.

In the Carolinas, natural and temporary climate factors have added to the "march upward" global warning. Because of this, the seas have increased by almost 5 inches in five years, said Andrea Dutton of the University of Florida.

Meteorologist Ryan Maue of weathermodels.com warned that observers should "stick to general trends in the world and not to individual cases".

Brian McNoldy, a hurricane expert at the University of Miami, said there were too many changing factors that made climate change particularly responsible.

"If you try to adopt a climate policy," Mr. Maue said Friday, "you do not want to do it on a storm basis."