The Future of Storms?

Early on the morning of August 27, as Hurricane Harvey pummeled Texas, floodwaters began lapping at the Nguyen family’s tree-lined front yard in Houston. Within hours, water rushed into their two-story brick house. The dad, Viet, plunged through the currents to grab life jackets and a raft from the garage.

“Are we going to die?” Brayden, 9, asked.

The Nguyens survived, but Harvey ruined most of their belongings and did major damage to their home. It was one of the worst natural disasters in U.S. history. As the hurricane turned city streets into raging rivers, tens of thousands had to flee their homes. Thousands of others were left stranded, some waiting desperately on rooftops for rescue by boat or helicopter. At least 70 people died.

Less than two weeks after Harvey, Hurricane Irma—the strongest Atlantic storm ever recorded—led to a mass evacuation of millions of people in Florida after it flattened several islands in the Caribbean. Irma killed more than 50 people.

The rain came quietly, but quickly. At 5 a.m. on August 27, floodwaters washed against the Nguyen family’s tree-lined front yard in Houston, Texas. Within hours, water rushed into their two-story brick house. The family struggled to move everything they could upstairs, out of the water’s reach. Then the dad, Viet, plunged through the currents to grab life jackets and a raft from the garage.

“Are we going to die?” Brayden, 9, asked.

The family survived, but Hurricane Harvey ruined most of their belongings and did major damage to their home. The storm was one of the worst natural disasters in U.S. history. It turned city streets into raging rivers. Thousands of people were left stranded in homes and on rooftops, hoping for rescue by boat or helicopter. At least 70 people died. Tens of thousands had to leave their homes.

Less than two weeks after Harvey, Hurricane Irma became the strongest Atlantic storm ever. Irma led to a mass evacuation of millions of people in Florida after it flattened several islands in the Caribbean. It also killed at least 50 people. 

What made these storms so intense? Scientists are now trying to figure that out—including what role, if any, climate change may have played.

“People always want to know is it climate change or is it not?” says Katharine Hayhoe, a climate scientist at Texas Tech University. “The answer is, it’s in between.”

While climate change didn’t necessarily cause Harvey or Irma, many scientists say, it likely made an already bad situation worse, deepening the storms’ impact.

Hurricanes form over warm oceans, drawing their destructive power from the hot moist air evaporating upward. Over the past century, the Earth and its oceans have gotten warmer, creating more opportunities for tropical storms and hurricanes. 

Most scientists say the planet is getting warmer because of a rise in greenhouse gases. Some of these gases occur naturally; others are produced by human actions. For example, the burning of fossil fuels like oil and coal—mostly from cars and power plants—creates carbon dioxide, the main greenhouse gas.

Greenhouse gases let sunlight through but also trap heat in the atmosphere, acting like a greenhouse. In the past century, Earth’s average temperature has risen about 1.5 degrees Fahrenheit (see graph). And for three years straight, the planet has broken its record for highest global average surface temperature, according to NASA. 

Harvey didn’t behave like a typical hurricane, meteorologists say, because it continued to gain momentum even as it neared shore. Harvey also stayed intact for several days on land, and its punishing 115-mile-per-hour winds and rain were concentrated in the same area. Storms usually move steadily inland or back out to sea, so their damage is spread out.

What made these storms so intense? Scientists are now trying to figure that out. They're looking at many factors, including what role, if any, climate change played.

“People always want to know, Is it climate change or is it not?” says Katharine Hayoe, a climate scientist at Texas Tech University. “The answer is it’s in between.”

Climate change didn’t necessarily cause Harvey or Irma. But many scientists say it likely made a bad situation worse.

Hurricanes are some of the most destructive storms on Earth. They form over warm oceans, drawing their power from the hot moist air evaporating upward. Over the past century, the Earth and its oceans have gotten warmer. That's created more opportunities for tropical storms and hurricanes.

Why is the planet getting warmer? Most scientists say it’s due to a rise in greenhouse gases. Some of these gases occur naturally; others are produced by human actions. For example, the burning of fossil fuels like oil and coal creates carbon dioxide, the main greenhouse gas. Emissions from cars and power plants increase the levels of these gases.

In theory, greenhouse gases act like a greenhouse. They let sunlight through but also trap heat in the atmosphere. The higher the build-up of greenhouse gases, the warmer the planet gets. In the past century alone, Earth’s temperature rose about 1.5 degrees Fahrenheit. And for three years straight, the planet has broken its record for highest global average surface temperature, according to NASA.

Harvey didn’t behave like a typical hurricane, meteorologists say, because it continued to gain strength even as it neared shore. Harvey also stayed intact for several days on land. And its punishing 115-mile-per-hour winds and rain were concentrated in the same area. Storms usually move steadily inland or back out to sea. This spreads out their damage. 

Some scientists say Harvey’s last-minute power surge and its onshore duration can be tied to water temperature. The Gulf of Mexico, where Harvey formed, was warmer than usual due to searing summer air temperatures. That heat transformed Harvey from a thunderstorm with strong winds into a major hurricane in roughly 48 hours, a day or two faster than is typical.

Irma formed in the Atlantic off Africa’s coast. The ocean was warmer than average and the storm grew to massive proportions—reaching 425 miles across—as it moved west. The heat helped the hurricane’s winds swirl at more than 185 miles per hour for a record 37 straight hours at its peak.

Climate change also likely contributed to Harvey’s record-breaking rainfall, scientists say. Warmer air holds more water, so mega storms tend to dump more rain as global temperatures rise. In Harvey’s case, Houston got nearly 52 inches of rain in five days—more than the city usually gets in a year. So while scientists don’t tie Harvey directly to climate change, many say it made the hurricane much more potent.

“Harvey was not caused by climate change,” scientist Stefan Rahmstorf told The Washington Post. “Yet its impacts—especially the extreme rainfall—very likely worsened due to human-caused global warming.”

Some scientists say Harvey’s last-minute power surge and its onshore duration can be tied to water temperature. Harvey formed in the Gulf of Mexico. The Gulf was warmer than usual due to blazing summer air temperatures. That heat transformed Harvey from a thunderstorm with strong winds into a major hurricane in about 48 hours. That's a day or two faster than typical.

Irma formed in the Atlantic off Africa’s coast. The ocean was warmer than average and the storm grew massive. As it moved west, it reached 425 miles across. At its peak, the hurricane’s winds swirled at more than 185 miles per hour for a record 37 straight hours. 

Climate change likely also contributed to Harvey’s record-breaking rainfall, scientists say. Warmer air holds more water, so mega storms tend to dump more rain as global temperatures rise. In Harvey’s case, Houston got almost 52 inches of rain in five days. That's more rain than the city usually gets in a year. So while scientists don’t tie Harvey directly to climate change, many say it made the hurricane much more powerful.

“Harvey was not caused by climate change,” scientist Stefan Rahmstorf told The Washington Post. “Yet its impacts—especially the extreme rainfall—very likely worsened due to human-caused global warming.”    

Not all scientists are ready to point the finger at climate change, though. Some say Harvey’s devastation, coming during the peak of hurricane season, would have happened regardless. 

“Given a metro area of 6.5 million people that basically sits in a paved floodplain, crossed by bayous, creeks, and rivers, and the same meteorological situation, we would be seeing a very major disaster even without any human influence on climate,” Suzana Camargo and Adam Sobel, science professors at Columbia University in New York, wrote in Fortune.

As Harvey and Irma wreaked havoc here, extreme weather was ravaging South Asia. Flooding killed more than 1,000 people and displaced millions in India, Nepal, and Bangladesh this summer. Mumbai, India, got as much rain in 12 hours on one August day as it usually gets over 11 days in a typical monsoon. 

Not all scientists are ready to point the finger at climate change though. Harvey came during the peak of hurricane season. So some scientists say its devastation would have happened anyway.

“Given a metro area of 6.5 million people that basically sits in a paved floodplain, crossed by bayous, creeks, and rivers, and the same meteorological situation, we would be seeing a very major disaster even without any human influence on climate,” Suzana Camargo and Adam Sobel, science professors at Columbia University in New York, wrote in Fortune.

At the same time Harvey and Irma were wreaking havoc, extreme weather was ravaging South Asia. Flooding killed more than 1,000 people and displaced millions in India, Nepal, and Bangladesh this summer. Mumbai, India, got as much rain in 12 hours on one August day as it usually gets over 11 days in a typical monsoon. 

Scientists worry these extreme storms are a warning sign for the future. Data shows that rising air and water temperatures could make powerful storms like Harvey and Irma more frequent—a notion that scares people in hurricane-prone regions.

“If this isn’t climate change, I don’t know what is,” Miami Mayor Tomás Regalado told The Miami Herald as his city prepared for Irma. “This is . . .  truly, truly [a] poster child for what is to come.”

Record rainfalls like Harvey’s may also become more common, making flooding more of a threat, experts say. The recent National Climate Assessment—a report by more than 300 scientists detailing the impacts of climate change on the U.S.—concluded that rains have become heavier and more frequent. The study warns that the driving force behind the changes is hotter air from “human-caused warming.”

As scientists search for answers, the Nguyens have started the long process of rebuilding their Houston home—and their lives.

“This has been traumatic,” dad Viet Nguyen says. “But I try to be practical about it and remember what we still have.”

Scientists worry these extreme storms are a warning sign for the future. Data shows that rising air and water temperatures could make powerful storms more frequent, scientists say. People in hurricane-prone regions find that idea scary.

“If this isn’t climate change, I don’t know what is,” Miami Mayor Tomás Regalado told The Miami Herald as his city prepared for Irma. “This is . . . truly, truly [a] poster child for what is to come.”

Record rainfalls like Harvey’s may also become more common. That'll make flooding more of a threat, experts say. Rains have become heavier and more frequent, according to the recent National Climate Assessment. The report, by more than 300 scientists, details the impacts of climate change on the U.S. The study warns that hotter air from “human-caused warming" has driven these changes.

As scientists search for answers, the Nguyen family has already started the long process of rebuilding their Houston home and their lives.

“This has been traumatic,” dad Viet Nguyen says. “But I try to be practical about it, and remember what we still have.”