What We Know About Climate Change and Hurricanes

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Hurricane Ida intensified overnight and became a Category 4 storm in just a few hours. The rapid increase in power raises questions about how much climate change is affecting hurricanes around the world. Atlantic Ocean. While researchers can’t say for certain whether human-induced climate change will mean longer or longer active hurricane seasons In the future, there is broad agreement on one thing: Global warming is changing storms.

The unusually warm Atlantic surface temperatures are helping to increase storm activity, scientists say. “It’s very likely that human-induced climate change contributed to this abnormally warm ocean,” said James P. Kossin, a climate scientist at the National Oceanic and Atmospheric Administration. “Climate change makes it more likely for hurricanes to behave in certain ways.”

Here are some of these ways.

There is a strong scientific consensus that hurricanes are getting stronger.

Hurricanes are complex, but one of the key factors that determines how strong a given storm will ultimately be is ocean surface temperature, because warmer water provides more of the energy that fuels storms.

“Potential density is increasing,” said Kerry Emanuel, a professor of atmospheric science at the Massachusetts Institute of Technology. “We predicted it would increase 30 years ago, and observations show it is rising.”

Stronger winds combined with downed power lines, damage to roofs and rising sea levels mean worse coastal flooding.

Dr. “Even if the storms don’t change, the storm surge is rising at sea level,” Emanuel said. He used New York City as an example, where sea levels rose by a foot in the last century. “If Sandy’s storm surge had occurred in 1912 instead of 2012,” he said, “it probably wouldn’t have flooded Lower Manhattan.”

Warming also increases the amount of water vapor the atmosphere can hold. In fact, every degree Celsius of warming makes the air hold about 7 percent more water.

This means we can expect future storms to release higher amounts of precipitation.

Researchers don’t yet know why storms move slower, but they are. Some say slowdowns in global atmospheric circulation or global winds may be partly to blame.

In a 2018 article, Dr. Kossin found that hurricanes over the United States have slowed 17 percent since 1947. Along with the increase in rain rates, storms cause a 25 percent increase in local precipitation in the United States, he said.

Slower, wetter storms also worsen flooding. Dr. Kossin likened the problem to walking around your backyard using a hose to spray water onto the ground. If you walk fast, the water won’t have a chance to start the pool. But if you walk slowly, “it will rain a lot under you,” he said.

Climate change is expanding the area where hurricanes can form, as warmer water helps fuel hurricanes.

Dr. Kossin said it’s “a migration of tropical cyclones from the tropics to the subtropics and mid-latitudes.” This could mean more storms making landfall at higher latitudes, such as in the United States or Japan.

As the climate warms, researchers say they expect storms to intensify faster. Researchers are still unsure why this happens, but the trend seems clear.

In a 2017 paper based on climate and hurricane models, Dr. Emanuel found that rapidly intensifying storms—storms that increase wind speeds to 70 miles per hour or more within 24 hours of landing—are rare in the period from 1976. 2005. On average, he estimated their probabilities in those years to be equal to one in a century.

At the end of the 21st century, he discovered that these storms can form. every five or 10 years.

Dr. “This is a forecaster’s nightmare,” Emanuel said. If a tropical storm or Category 1 hurricane turns into a Category 4 hurricane overnight, “there’s no time to evacuate people,” he said.

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