Tuesday, April 19, 2016

Houston Drowns Again In Epic Flood

This guy for unknown reasons drove into deep Houston
floodwaters Monday and had to be rescued by
a TV reporter doing a live report nearby.  
You've probably seen the news out of the Houston, Texas area, where at least five people have died in massive flooding due to record downpours Monday morning.

More than 11 inches of rain came down on Houston Monday, its rainiest day on record. And that 11 inches came before noon.

Rainfall ranged up to 17 inches in just 12 hours or so, and many areas around Houston reported a foot of precipitation.

News footage showed vast neighborhoods under water. Damage is immense. There's a couple videos at the bottom of this post that you just have to see.

As always with these extreme newsworthy weather events, you get the question:

Was this caused by climate change?

Some would say yes. But, the answer is much more complicated than that. For that matter, so is the question.

The online magazine Slate put out this Tweet Monday: "Houston is flooding - again -- and climate change is a major reason why."

The link to the actual Slate article, written by Eric Holthaus, is correctly more nuanced that the Slate Tweet.

As Holthaus writes:

"Since the 1950s, Houston has seen a 167 percent increase in the heaviest downpours - defined as the umber of days where total precipitation exceeded the heaviest one percet of all local events -- one of the fastes rates of increase anywhere in the country.

That's exactly what's expected to happen as the climate warms, since warmer air can hold more water vapor than cooler air.

An increase in the frequency of heavy rain events has long been considered one of the likeliest consequences of global warming, and a recent comprehensive National Academies report endorsed this link. 

Blocking weather patterns like this weekend's may be happening more often due to climate change, boosting the likelihood of heavy rainfall events, according to a new study published last week."

Two points to consider about Holthaus' writing.

First, the more minor one: If you're going to get a blocking pattern, they're much more likely to happen this time of year, in the spring, than other times of year.

A blocking pattern often happen when cold pools of air in the upper atmosphere get cut off from the jet stream, which steers weather systems generally from west to east across the northern hemisphere.

Picture receding water after a flood. When the water subsides, puddles remain behind. Those are like those cold pools of air that block weather patterns this time of year.

The jet stream retreats more and more to the north this time of year, so, like that receding water leaving those puddles behind, the receding jet stream leaves those cold pools of air behind.

Blocking patterns are not at all unusual in April. Still, Holthaus is absolutely correct when he says  says that the blocking weather patterns have gotten more common.

Another good point Holthaus makes shows that climate change isn't the only thing making the Houston flood worse.

He writes:

"This is at least the fourth major flood in the Houston area in just the past 12 months, with previous flooding events last May, June and October pummeling Texas hard."

(Editor's note: There was also some pretty bad flooding in Texas in December, too)

"The triangle between Dallas, Houston and San Antonio is sometimes referred to as 'flash flood alley' because of its dangerous mix of hilly terrain, sprawling urbanization and frequent heavy downpours, adding to the region's already considerable vulnerability to climate change."

It's true that downpours in Texas are getting more frequent and worse over the past few decades. Simultaneously, the area has been paved over with freeways and parking lots and strip malls and housing developments and so on.

The water can't soak through all that pavement, as it used to soak into the ground. So the water runs off during heavy rain, and the flooding is thereby worse than it otherwise would have been.

But asking whether the event is climate related is the wrong question. As Dr. Marshall Shepherd reminds us, weather is influenced by lots of things, and one of them is often climate change. But teasing out what part of it is climate change is difficult.

Think of a very great Major League Baseball batter who hits a lot of home runs.  Then let's say the batter decides to go on steroids. He now hits even more home runs.

He would have hit a lot of home runs without the steroids, so how do you figure out which home run was caused by steroids and which were caused by his natural talent. You can't tease those apart so easily.

Climate change puts weather on steroids. The weather hits more "home runs" in the form of more and bigger extremes. There would have been a lot of weather extremes anyway, but this just add juice, pardon the pun, to the system.

One of the most iconic videos from Monday's Houston flood has to be the guy who mysteriously drove into a flooded underpass as a television reporter was doing a live standup.

The reporter had to rescue the confused guy:

Drone footage shows huge neighborhoods around Houston under water:

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