Researchers are uncertain whether anthropogenic climate change means a longer future hurricane season or a more active hurricane season, but there is broad consensus on one thing.
Scientists say the unusually warm Atlantic surface temperature helped increase storm activity. “It is very likely that human-induced climate change has contributed to the extraordinarily warm waters,” said James P. Kossin, a climate scientist at the US National Oceanic and Atmospheric Administration. “Climate change makes it more likely that hurricanes will behave in certain ways.”
Here are some of these methods:
1. Strong wind. There is a solid scientific consensus that hurricanes are becoming more powerful.
Hurricanes are complex, but one of the key factors in determining how strong a particular storm will ultimately be is sea surface temperature. This is because warm water provides more energy to facilitate the storm.
Kerry Emanuel, a professor of atmospheric science at the Massachusetts Institute of Technology, said: “We predicted it would go up 30 years ago, and observations show it goes up.”
Strong winds, combined with power line downs, roof damage, and sea level rise, mean worsening coastal floods.
“Even if the storm itself hasn’t changed, the storm surge is on the storm surge,” said Dr. Emmanuel. He used New York City as an example, where sea level had risen about a foot in the last century. “If the Sundi storm surge occurred in 1912 instead of 2012, it probably wouldn’t have flooded Lower Manhattan,” he said.
2. More rain. Warming also increases the amount of water vapor that the atmosphere can hold. In fact, a 1 degree Celsius warming can hold about 7 percent more water in the air.
This means that future storms can be expected to rain more.
3. The storm will be slower. Researchers still don’t know why the storm is moving more slowly, but it is. Some say it may be due in part to slowing global atmospheric circulation or global winds.
In a 2018 paper, Dr. Kossin wrote that hurricanes in the United States have slowed by 17% since 1947. Coupled with the increase in rainfall, he said, storms are increasing local rainfall in the United States by 25%.
Slow, damp storms also exacerbate floods. Dr. Kossin likened this problem to walking around the backyard, spraying water on the ground with a hose. If you walk fast, the water has no chance to start the pool. But as he walked slowly, he said, “You will have a lot of rain under you.”
4. Widespread storm. Climate change is expanding the zones in which hurricanes can form, as warmer water helps fuel hurricanes.
“Tropical cyclones move from tropical to subtropical and mid-latitude,” Dr. Kossin said. This could mean more storms landing at higher latitudes, as in the United States and Japan.
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5. More volatility. As the climate warms, researchers also expect the storm to intensify more rapidly, they say. They are not yet clear why it is happening, but the trend seems clear.
In a 2017 paper based on a model of climate and hurricanes, Dr. Emmanuel said that rapidly intensifying storms (wind speeds of more than 70 mph in the 24 hours prior to landing) were rare from 1976 to 2005. I am writing. He estimated that those possibilities of those years were equal to about once in a century.
By the end of the 21st century, he discovered that those storms might form. Once every 5 or 10 years..
“It’s a forecaster’s nightmare,” said Dr. Emmanuel. If a tropical cyclone or category 1 hurricane evolves into a category 4 hurricane overnight, he said, “There is no time to evacuate people.”