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Climate Change Experts Weigh In on Why Houston Flooded During Hurricane Harvey

And yes, it has to do with global warming.

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Homes remain flooded as Texas moved toward recovery from the devastation of Hurricane Harvey on September 4, 2017 in Houston, Texas. Almost a week after Hurricane Harvey ravaged the city, some neighborhoods still remained flooded and without electricity. While downtown Houston is returning to business, thousands continue to live in shelters, hotels and other accommodations as they contemplate their future.
Spencer Platt/Getty Images

Editor’s note: A quote from Dr. Andrew Dessler has been updated for clarity.

At this point, there’s been plenty of theorizing on why Houston flooded. The answers are fairly routine: Houston’s flatness, its lack of drainage, and the fact that the unzoned and over-developed metropolitan area contains too much pavement and too little land to soak up rain water.

But for atmospheric scientists, there’s another, far more ominous explanation to consider. In a mere 48 hours, Harvey went from a middling tropical storm, with winds of 45 miles per hour, to a Category 4 hurricane, with winds of 130 miles per hour. When it hit land, it dumped close to 50 inches of rain on Texas, which makes it the biggest rain storm in U.S. history. “There are many explanations for Harvey’s rampage,” Dr. Andrew Dessler, a professor of atmospheric science at Texas A&M in College Station, said. “But human induced climate change definitely made the storm worse.”

Scientists like Dessler, who has been studying climate change for twenty years, have long warned about the impact of global warming. They have patiently explained, over and over, that when too much carbon dioxide is added to the atmosphere, the earth’s heat is trapped, making it harder for energy to be sent radiating into space. According to the scientists, most of that trapped energy goes into the earth’s oceans. If carbon dioxide levels stay the same or get higher, the ocean water itself eventually gets warmer.

Few bodies of water have heated up like the Gulf of Mexico. As a result, when a tropical storm passes over the Gulf, those warm waters become pure fuel for that storm to tap. What’s more, because the temperatures in the atmosphere over the Gulf are also warmer, more ocean water is evaporating and hanging in the air, just waiting to be swept up by a storm and dumped over land as rain.

“We’re not saying that climate change is creating more tropical storms or hurricanes,” said Dr. Daniel Cohan, an atmospheric scientist and professor of environmental engineering at Rice University in Houston. “But what’s becoming clear is that once these storms form, they are likely to become much more intense.” Cohan noted that in the past three years, Houston has been hit by three so-called “500-year storms.” “The chances of that happening by coincidence are just about zero,” he concluded.

Cohan even speculated that global warming was the reason Harvey stalled over southeast Texas. “We know that with climate change, as the world gets warmer, the jet streams are now moving away from tropics and moving closer to the poles,” he explained. “What happened in Harvey’s case is that the jet stream wasn’t out there to push the storm along. It had moved north. I think for that very reason we’ll see more of these hurricanes stall over land, which means more devastating monster rains.”

In early 2005, several months after Hurricane Charley unexpectedly swept across Florida, Cohan was attending an academic conference of atmospheric scientists where a fierce debate broke out over the link between global warming and hurricanes. “Scientists were standing up and heatedly challenging one another, which never happens in one of those kinds of conferences,” Cohan recalled. But now, Cohan acknowledged, that debate is over. “The only question today is just what is coming next,” Cohan said.

As scientists, Cohan and Dessler are too measured to issue particularly dire warnings about the future of hurricanes in the age of global warming. They don’t talk in apocalyptic terms about more hurricanes rampaging up and down the Gulf Coast, causing billions of dollars more in damage. They don’t predict that the federal government might tire of providing disaster relief funds to coastal residents, or that mortgage companies might stop providing loans for their homes and businesses. They don’t mention that someday, coastal lands might largely be uninhabited.

But Cohan did point out that as long as there’s little commitment from countries, especially the U.S., to follow the Paris Climate Accord—which aims to limit the rise in global temperatures to 2 degrees Celsius (or 3.6 degrees Fahrenheit) for the rest of the century—“then our best case scenario is that we’ll have perhaps twice as much warming as we have now. Think of what a hurricane could look like in the Gulf of Mexico with that kind of warming.”

“If Harvey is not a wake-up call for us to reduce the man-made warming of the earth, I don’t know what is,” Dessler added. “It flabbergasts me that people are still denying what’s right before their very eyes.”

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  • anonyfool

    Houston had the opportunity to blunt the effects of flooding but balked at the 400 million dollar price tag, 20 years ago.

    This solution might not have worked in a direct super hurricane hit on Houston with a 15 foot storm surge.

  • Rickey Benson

    There has been global warming and cooling on this planet for millions of years. However, it takes left wing nutcases to claim that this process is now caused by man. They can’t prove it so they make up lies and manipulate data in order to obtain grant money to publish results and findings that the money people want. They have created their own religion. First comes the money then comes the findings. What about the lack of hurricanes in the last 8 years? I am sure it was caused by global warming. Want an explanation for all the rain and flooding. It is simple. The storm was blocked by high pressure ridges that would not allow it to move. So it basically stayed in place and dumped 60″ of rain. Has nothing to do with man made “global warming”. It is called nature.

    • cshorey

      Working in paleoclimatology, we know why the climate changed in the past, and we look at all those natural causal factors today and guess what we see. Orbital forcing should be making us colder. Solar output should be making us colder. Cosmic rays should be making us colder (if they even have an effect). Meanwhile it was predicted in the 1970’s that greenhouse gas warming should warm the troposphere but cool the stratosphere. And that’s exactly what has happened. Please drop the “climate has changed in the past” bit as it only an argument from ignorance of what we really do know. And as for as a storm stalling, would you like me to explain how a warming world causes the jet stream to weaken?

      • Rickey Benson

        I notice that you used the word “guess”. That is your entire position; just one wild ass guess. It is nothing more than an opinion. Mankind cannot control the weather. Just another money grab by the arrogant and the stupid.

        • cshorey

          You don’t read well and don’t get rhetorical phrasing apparently. Want to try to address the actual content of my post, you might get a little more respect, and won’t make me think you’re a complete idiot. Right now that’s my only position I can think of for you.

          • Rickey Benson

            You’re the one that used the word “guess”. Now you want to walk that back. You obviously have a problem with the concept of rational thought.

          • cshorey

            Ha! Hey little Ricky, guess what? You don’t know how to properly read the phrase “guess what “! Would you now like to go for the idiot hat trick, or try replying to the actual content of my post.

          • Rickey Benson

            You may need a refresher in English composition. Try the 3rd grade. There is no question mark at the end of this sentence. So, it is a simple statement that you made. Now you are even attempting to walk that back. I just prefer to think of you as just another dumbass trying to impress other people. I almost feel sorry for you but, I got over that.

          • cshorey

            Strike three at actually understanding and responding. I now think you are in the third grade. And a pretty dumb third grader.

        • Melanie Nelson

          We aren’t talking about “weather”.

    • Jed

      your reasoning is faulty and your evidence is false. carry on.

  • Bethany Brandon

    I personally believe we’re beyond the tipping point for our human epoch anyway. Achieving only a maximum 2-degree C increase over the remainder of this century is beyond our capabilities already. It’s time to work on adaptation to what Nature has shown to be inevitable. The confusion and dissension comes from scientists claiming that since we made this mess, we can fix it — and then explaining how a political accord is the fix. Ha. Time to drop the politics and start planning for how to live in a different, warmer world.

  • Mr-DJ

    It’s a simple calculation:
    50″ = Why

  • Paul Bacon

    With the warming of Gulf waters not only are storms more intense, as mentioned, but also hurricane season is longer.