Catastrophic storms, once rare, are almost routine. Why?
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HOUSTON – While climate change did not cause Hurricane Harvey, it could explain the intensity of this cyclone as well as other catastrophic storms that have hit the United States in recent years, experts say.
Harvey is the latest in little more than a decade of “500-year” and “100-year” floods that once were considered rare.
The storm, a Category 4 hurricane when it initially made landfall last week, has dumped trillions of gallons of water onto southeastern Texas, submerged houses and freeways, driven Houston-area residents from their homes and resulted in more than 20 deaths thus far.
Black publishers impacted
Searches for family, loved ones and associates and co-workers continued throughout the week. Many depended on media to get the word out about missing loved ones.
The National Newspaper Publishers Association blasted an alert to their editors and publishers showing one of their leading publishers, former NNPA Foundation Chairwoman Sonny Messiah-Jiles of the Houston Defender, being rescued by boat along with her family.
Houston Forward Times Publisher Karen Carter Richards, responded to an email from the Trice Edney News Wire saying she was thankful for “God’s Amazing Grace!!!”
She added, “My family and I are good. No water in our homes, we’re safe and dry. My office got a little water but nothing major to even talk about. Keep praying!”
Francis Page, publisher of the Houston Style magazine had not yet been contacted as of the Florida Courier’s press time Wednesday night.
The storm made a second landfall on the Gulf Coast on Wednesday, cutting a devastating path across southeast Texas and southwest Louisiana – even as the sun began to emerge in Houston and some residents returned to their waterlogged homes.
A string of coastal Texas cities was engulfed in water as Harvey came ashore again at 5 a.m. Wednesday just west of Cameron, La.
The Texas National Guard had made more than 8,500 rescues and 26,000 evacuations, Texas Gov. Greg Abbott said Wednesday. He announced he was seeking an additional 10,000 National Guard members from other states to help the 14,000 Texas Guard members who were activated.
Damage to environment
The long-term fallout from Hurricane Harvey is still uncertain. But the Gulf Coast has already taken an environmental punch.
More than one million pounds of air pollution was released in that region as petrochemical plants were forced to shut down by the hurricane and flooding that followed, according to the Environmental Defense Fund. A small percentage of the pollution was attributed to damaged or malfunctioning equipment caused by the storm.
The data were based on regulatory filings with the Texas Commission on Environmental Quality. The pollutants include volatile organic compounds, sulfur dioxide and carcinogens like benzene.
“Air pollution is one of the unseen dangers of the storm,” said Dr. Elena Craft, the EDF’s senior health scientist, putting children and seniors to greater risk of asthma, heart attacks, strokes and other health problems.
EDF officials also said state regulators shut down Houston-area air quality monitors to avoid storm or flood damage, making it more difficult to independently measure air pollution.
A Houston Press story quoted residents living near the Houston Ship Channel as experiencing an “industrial-like stench.” One woman described it as smelling like “burnt rubber with a hint of something metallic thrown in.”
Big storms bigger
Climate change won’t mean more storms overall – but it probably will mean that that biggest storms become even bigger, scientists say.
For example, rising ocean temperatures could be making storms like Harvey bigger than they would be otherwise, said Michael Mann, a climate scientist at Pennsylvania State University. That’s because as the ocean’s surface temperature rises, the atmosphere’s ability to hold moisture goes up.
According to the Clausius-Clapeyron Equation, every 0.5 degrees Celsius of warming means an extra 3 percent or so of moisture in the air. And Harvey grew over an ocean that was 1 to 1.5 degrees Celsius warmer than just a few decades ago, which means there’s around 5 percent more moisture in the atmosphere.
More moisture means a higher chance of heavier rainfall and bigger flooding – both of which, in Harvey’s case, have been wreaking major havoc in the greater Houston area.
“There is a good chance it would have happened anyway,” Mann wrote of Harvey in an email. However, he added, “the impacts were likely greatly amplified by climate change.”
In this altered environment, with heavier rains, storms behave differently, said Kevin Trenberth, a climate scientist with the National Center for Atmospheric Research.
“The storm itself grows a little bit more intense, it gets a little bit bigger and it helps it to last longer,” Trenberth said.
Hurricanes usually start to wane soon after they make landfall, because they’re cut off from the supply of moisture from the ocean. Not so with Harvey, whose size allowed it to stay plugged into its power source in the Gulf.
“That’s a big factor with Harvey … it’s big enough that it still had spiral arm bands that were reaching out into the Gulf and bringing a lot of moisture into the storm,” Trenberth said, which “enabled it to keep going where most storms would have petered out.”
Harvey flooded Houston partly because it stalled over southeastern Texas for days, rather than moving northward, scientists said. While there are some hypotheses that this slowing may be caused by climate change in the Arctic, Anand Gnanadesikan, a climate scientist at Johns Hopkins University, said the two were unlikely to be linked.
Exam ining the dynamics shaping Hurricane Harvey may help researchers get a better handle on climate change, scientists said.
“We’ll see a number of scientific studies analyzing this event,” said Noah Diffenbaugh, a climate scientist at Stanford University. “The rapid development of the tropical cyclone that occurred, the strength of the landfall, the stalling over the coast that produced the very high rainfall totals … these are all going to be questions that we’re going to see scientists try to answer.”
Another idea that may require a revisit? Calculating the risk of such storms in the future.
What does it mean?
Harvey already has been called a 500-year flood, and by the time the storm has dissipated, it may well reach 1,000-year status. But the last decade or two have brought a slew of these supposedly rare storms, including two 500-year floods in the Houston area in 2015 and 2016.
So what exactly does a 500-year storm mean?
“This concept actually comes from hydrology, and it relates a lot more to precipitation than it does to hurricanes or to the storms themselves,” Trenberth said.
It’s a concept typically used in assessing risk for flood insurance. It does not mean that a given storm can happen only once per century or twice per millennium, he added.
It means that, for any given year, in stable climate conditions, a storm of this magnitude has a 1-in-100 (or 500, or 1,000) chance of taking place. So yes, you can, theoretically, have multiple 1-in-100-year hurricanes in a row — it’s just a very unlikely event.
“As long as the climate isn’t changing, you can define these things reasonably well,” Trenberth said. “With climate change … what used to be a 500-year event is becoming a 70-year event or a 50-year event. It doesn’t mean that they’re common, but they’re no longer anything like as rare.”
A critical consideration
As human populations continue to grow in coastal areas, some cities may not be built to handle such extreme “500-year” events, which may happen more often in the future, experts say.
“That’s what the changing climate has done,” Trenberth added. “It means the extremes are greater – and if we don’t adapt to these, if we don’t take them into account, if we don’t build more resilience, we will suffer the consequences.”
Information compiled by Molly Hennessy-Fiske, Amina Khan, Jenny Jarvie, Matt Pearce, and Ann M. Simmons of the Los Angeles Times; Jeff Mosier of The Dallas Morning News (TNS); and the Trice Edney News Wire was used to prepare this report.