Advertisement

newsTexas

'Loading the dice': Climate change could make hurricanes more devastating, scientists say

Harvey-like storms are likely to happen more often and hurricanes in general are expected to cause more damage as a result of climate change.

Editor's note: This story was originally published on Aug. 24, 2018 a year after Hurricane Harvey hit the Gulf Coast.

Rain was falling when climate scientist Phil Klotzbach gave a speech in Houston two weeks before Hurricane Harvey devastated the Texas coast last August.

Just 3 inches fell that night, according to the Colorado State University researcher, but water had already started flooding his hotel’s parking garage and creeping toward the lobby.

Advertisement

"I can't imagine what it's going to be like when there's actually a hurricane," Klotzbach texted his wife.

Breaking News

Get the latest breaking news from North Texas and beyond.

Or with:

Phil Klotzbach is a research scientist in the Department of Atmospheric Science at Colorado...
Phil Klotzbach is a research scientist in the Department of Atmospheric Science at Colorado State University, and he studies hurricanes and the forecasting of hurricanes.(Courtesy of Phil Klotzbach)

Soon after, Klotzbach and the rest of the country saw what would happen when as much as 60 inches of rain inundated that vulnerable stretch of coast — more than 80 deaths and at least $125 billion worth of damage, a dollar figure surpassed only by Hurricane Katrina.

Was it merely a cyclical climate event, an act of God or a man-made catastrophe? Scientists across the world started trying to answer those questions almost immediately after the storm.

Advertisement

At least five peer-reviewed scientific papers have been published in the last year looking at how global warming has affected and changed the probability of a storm of this scale. And more research is in the pipeline seeking to provide the broadest possible understanding of Harvey.

So far, a couple of things are becoming clearer: Harvey-like storms are likely to happen more often and hurricanes in general are expected to cause more damage as a result of climate change. And that could put more lives at risk in the nation’s fifth largest metro area that is also home to more than a fourth of the country’s petroleum refining capacity.

What role did we play?

Both people and important infrastructure like oil refineries are moving more and more to...
Both people and important infrastructure like oil refineries are moving more and more to coasts, which could mean greater devastation in the next major storm.(Spencer Platt / Getty Images)
Advertisement

"By the standards of the average climate during 1981-2000, Harvey's rainfall in Houston was 'biblical' in the sense that it likely occurred around once since the Old Testament was written," climate scientist Kerry Emanuel, of Massachusetts Institute of Technology, wrote in a journal article last year.

His research calculates that what had been a one in 2,000-year event for the city of Houston, could become a one in 100-year event by the end of this century, if little is done to slow greenhouse gas emissions. Those emissions — mainly from the burning of fossil fuels — have led to the current global warming crisis.

A multinational team from the U.S., England and the Netherlands determined climate change made the storm 15 percent more intense and also made it 1 ½ to 5 times more likely to occur.

"This analysis makes clear that extreme rainfall events along the Gulf Coast are on the rise," according to that research published in Environmental Research Letters.

Scientists from Lawrence Berkeley National Laboratory in California concluded that climate change likely increased the chance of a Harvey-like storm by 3 ½ times, according to their paper in the journal Geophysical Research Letters.

“Further, precipitation accumulations in these areas were likely increased by at least 18.8 percent,” wrote authors Mark D. Risser and Michael F. Wehner.

Increasing temperatures in 2017 — the third hottest year on record — also played a role, since most of the excess heat is absorbed by the world’s oceans.

Ocean temperatures last summer, both globally and in the Gulf of Mexico, were the highest on record, according to another multinational team, led by Kevin E. Trenberth of the National Center for Atmospheric Research. Ocean heat provides fuel for hurricanes.

Advertisement

"The increase in strength and size [of Harvey] meant that even after landfall, its circulation extended well out over the Gulf, where a continual flow of moisture fed and prolonged the storm, long after most storms would have died," according to the paper published in the journal Earth's Future.

MIT climate scientist Kerry Emanuel is widely respected for his research on global warming's...
MIT climate scientist Kerry Emanuel is widely respected for his research on global warming's effects on hurricanes. He's also one of the scientists to have studied how climate change could have influenced Hurricane Harvey.(Courtesy of Kerry Emanuel)

Emanuel’s research estimated climate change likely increased the odds of a storm like Harvey sixfold, slightly more than the other studies. Different approaches to the research yielded different numbers, he said, but all the papers found a significant increase in the chances of a storm of this scale.

Gary Lackmann, a climate scientist at North Carolina State University, said it’s startling to see so much research on a single storm come together so quickly. He said techniques and technology have evolved, allowing scientists to gather and analyze data faster than ever before.

Advertisement

Much of the research relies on computer modeling, particularly when it comes to the most powerful storms. Those category 4 and 5 hurricanes are so rare that scientists say it would take decades to collect enough data to spot trends.

"If we just wait for classic statistics to tell us when the storms are no-kidding stronger than they used to be, we'll probably be somewhere between 50 and 75 years late,” said David Titley, director of Penn State University’s Center for Solution to Weather and Climate Risk. “It'll take us decades and decades to catch up with the fact that reality is changed."

Climate change affects hurricanes

Areas like Florida's Key West are in more danger from both rising sea levels and major...
Areas like Florida's Key West are in more danger from both rising sea levels and major storms, as the gradually rising coastlines create quicker and more devastating floods.(Rob O'Neal / The Key West Citizen)
Advertisement

Climate scientists are generally cautious when describing the connection between global warming and specific weather. The science and the politics of the subject demand precise language.

In the case of Harvey, scientists used hurricane and climate models and real-world climate data to simulate thousands of storms. Statistical analysis then allowed them to estimate how much global warming has tilted the odds of Harvey or a storm like it hitting the Texas coast.

"You can't attribute a single weather event unambiguously to climate change," Lackmann said. "But what you can do is say, 'Well, how would climate change affect the odds of a certain type of event happening?'"

Scientists often use the term “loading the dice” when describing the influence of climate change on extreme weather.

Advertisement

Long before Harvey, researchers were charting how the changing climate affects hurricanes. And the results were almost universally troubling.

"A review of existing studies ... lead us to conclude that: it is likely that greenhouse warming will cause hurricanes in the coming century to be more intense globally and have higher rainfall rates than present-day hurricanes," the National Oceanic and Atmospheric Administration has determined.

The heating oceans make the hurricanes more powerful, while the heating atmosphere provides more moisture for rain.

The most recent research indicates that climate change would on average increase rainfall from hurricanes, increase the frequency of the strongest hurricanes (categories 4 and 5) and increase sea levels, which add to the threat of storm surges and allow hurricanes to intensify more quickly.

Advertisement

Emanuel called the rapid intensification a “forecaster’s nightmare.”

"The last thing you want as a forecaster is to go to bed with a strong tropical storm and wake up with a Cat. 4 storm," he said.

Scientists also expect the movement of hurricanes to slow in some areas, including Texas. Penn State’s Titley said his research over the summer found early- and late-season slowing of the winds that steer hurricanes along the Texas coast.

Advertisement

That’s good news for inland cities, like Dallas, since it would give storms more time to weaken. But that slower movement would also give storms a greater opportunity dump rain on the coast, which is what happened with Harvey and its record flooding.

Also, researchers expect East Coast hurricanes to form farther north and turn farther north. "You could see much more devastating strikes on Maryland and Virginia and Delaware," said Titley, a retired U.S. Navy rear admiral who led the branch's climate change task force.

There is no consensus about how climate change would affect the total number of hurricanes. Research has suggested that there could be fewer hurricanes or perhaps no more than there are now on average.

Shorter-term weather systems play a larger role the numbers of hurricanes year-to-year. In May, NOAA’s Climate Prediction Center forecasted a near-average Atlantic hurricane season.

Advertisement

That forecast has since been revised downward to below normal. A predicted El Niño is expected to hamper the formation of hurricanes this summer.

Even if climate change doesn’t result in more hurricanes, Emanuel said that’s not as reassuring as it sounds.

"The weak storms don't usually do much damage," he said. "We're, in practice, concerned about the strong storms, and we're more confident about those [increasing]."

Hurricanes of the future

One effect of Hurricane Harvey was the shut down of many major oil refineries along the Gulf...
One effect of Hurricane Harvey was the shut down of many major oil refineries along the Gulf Coast, including ExxonMobil's facility in Baytown.(Tom Fox / Staff Photographer)
Advertisement

How hurricanes act in the future will depend in part on how well the world slows global warming, according to scientists.

The international Paris Agreement seeks to keep post-industrial era warming to “well below” 2 degrees Celsius. President Donald Trump announced last year his intent to pull the U.S. out of that pact.

If the average global temperature rises by 2 degrees, models project that hurricane rainfall would increase by 10 to 15 percent within about 60 miles of the storm, according to the NOAA’s Geophysical Fluid Dynamics Laboratory. Those same models also anticipate an increase in storm intensity of 1 to 10 percent.

The amount of damage caused by the storms is more complicated, said Klotzbach, the Colorado State climate scientist. To a great extent, hurricane damage is increasing because of population growth and development in areas regularly threatened by tropical storms.

Advertisement

The number of people living in U.S. coastal areas grew nearly one-third faster than non-coastal areas between 1960 and 2008, according to risk consulting firm AIR.

The coastal growth also includes critical pieces of the nation’s petroleum infrastructure. When Harvey struck Texas, it shut down more than one-fifth of the nation’s gasoline-refining capacity. Since then, refineries, chemical plants and export facilities have continued to grow, from Corpus Christi to Beaumont.

"We can make problems worse that don't necessarily have anything to do with CO2," Klotzbach said.

Advertisement

Emanuel described it as a “spectacular lemming-like march to the sea all over the world."

"In certain parts of the country, a few inches [of rain] makes no difference," Klotzbach said. "But you see other places like Louisiana or Florida, where the coastlines slope up very, very gradually, a few inches can mean significantly more inundation."

What’s next for Houston?

Advertisement

For those in Houston and surrounding areas, Harvey wasn’t just a single disaster that came and went. The hurricane’s devastation in 2017 followed the destructive Memorial Day and Halloween floods of 2015 and the Tax Day Flood of 2016.

"Some of the structures and homes that flooded in Harvey had been flooded three and four times in the last three years," said Jeff Lindner, meteorologist for the Harris County Flood Control District. “Some of the residents of this area say 'enough is enough. We've got to start getting these [flood control] projects in the ground.'"

More than 40 percent of the people flooded by Harvey were outside the floodplains. The Harris County Flood Control District reported that 154,170 houses were flooded during that storm.

On Aug. 25, the one-year anniversary of Harvey's landfall, Harris County voters will decide on a $2.5 billion bond package to improve flood control. Local officials said money from that bond package — the first since the 1980s — would also unlock another $2 or $3 billion worth of matching federal funds.

Advertisement

Even that number isn’t enough. Lindner said the district estimated it would take about $30 billion to upgrade its 2,500 miles of streams and man-made drainage channels to handle a 100-year rainfall. The flood control district has an annual budget of about $120 million, half of which goes to maintaining its existing infrastructure.

And billions more are on their way from Washington, D.C.

Reaching that flood protection goal will soon get even harder. NOAA is redefining a 100-year rainfall — a storm that has a 1 percent chance of occurring in a given year — for Texas. The new numbers will be based on historic rainfall totals and don’t take into account climate change projections.

Lindner said Harris County’s 100-year storm is now defined as one with 13.2 inches of rain in 24 hours. He expects that to increase to 16 to 17 inches when NOAA’s calculations are finalized.

Advertisement

But in the future, climate change could make those 100-year rainfalls even more common.

"We are recognizing the fact that the current 100-year flood plain maps are maybe not accurate enough,” said Stephen Costello, Houston’s chief resilience officer. "We just recognize what has occurred and acknowledge that we have to do something different than what we've done in the past."

Costello, sometimes called Houston’s “flood czar,” said the city is asking developers to raise the heights of new buildings and is working to solve drainage problems for areas already developed.

Advertisement

However, incorporating climate change calculations into these new plans is a struggle, Lindner said.

"You have the engineering side of the spectrum that needs an exact number so they can design for that number," he said. "The climatologists and the operational engineers — the people who are building stuff — aren't necessarily talking to each other. They're kind of talking past each other."

Despite the scientific consensus about climate change, the political buy-in is a key hurdle, particularly in Texas, where politicians regularly dismiss the seriousness of climate change and the human contribution to it.

U.S. Rep. Lamar Smith, R-San Antonio, chairman of a prominent science committee, wrote a column for the conservative website The Daily Caller in November attacking Emanuel's journal article about Harvey and climate change.

Advertisement

And in 2016, Titley encountered a similar reaction while in Austin on behalf of the Citizens’ Climate Lobby. There, he addressed a group of senior state legislative staffers about extreme weather.

Titley said he couldn’t remember one particularly bold staffer’s name but did recall his reaction.

"Don't you understand? We live in Texas," Titley said, paraphrasing the staffer. "We love extreme weather. Bring it on."