Historic Texas Rains Lead To Disastrous Floods

Record-Breaking Rainfall In Parts Of Texas Leads To Deadly Flooding. Throughout April and May, parts of Texas experienced record-breaking amounts of rainfall that led to disastrous flooding resulting in deaths, mass evacuations and widespread property damage. On May 25, Gov. Greg Abbott said the rainfall led to the “biggest flood this area of Texas has ever seen,” and on June 1, he declared a state of emergency in 31 counties. [NBCNews.com, 4/18/16; Reuters, 6/3/16, 5/25/16; Houston Chronicle, 6/5/16; Texas.gov, 6/1/16]

Link Between Extreme Rainfall And Global Warming Is Well-Documented

AP Analysis: Climatologists Say Extreme Downpours Are Occurring Twice As Often In Houston Area, Due In Part To Climate Change. The Associated Press reported that Houston “is being overwhelmed with more frequent and more destructive floods” in recent years, which experts are attributing to both global warming-induced extreme precipitation events and “unrestrained” urban development. The AP reported:

Extreme downpours have doubled in frequency over the past three decades, climatologists say, in part because of global warming. The other main culprit is unrestrained development in the only major U.S. city without zoning rules. That combination means more pavement and deeper floodwaters.

[...]

Climate change is increasingly concentrating downpours into smaller areas, with big implications for urban flooding, scientists say. On April 18, one northwest section of Harris County got 4.7 inches in an hour.

Rising average temperatures since 1985 have packed 7 percent more moisture into the atmosphere above Houston, while warmer Gulf of Mexico waters collude in the heavier rains.

Since 1986, extreme downpours - the type measured in double-digit inches - have occurred twice as often as in the previous 30 years, the AP weather analysis showed.

Texas State Climatologist John Nielsen-Gammon said to expect more frequent and bigger downpours. “The odds are twice as high as they have been in the past.” [Associated Press, 5/19/16]

Texas State Climatologist: Increased Ocean Temperatures Are “One Likely Cause” Of More Frequent Heavy Rainfall In The Region. In an interview with Grist, Texas’ state climatologist, John Nielsen-Gammon, stated that “one likely cause” of the increased frequency of extreme downpours in areas of Texas over the last 30 years “is the increase in ocean temperatures from the Gulf of Mexico and tropical Atlantic. That determines how much moisture is in the atmosphere.” [Grist, 5/31/16]

National Climate Assessment: Global Warming Is Leading To More Heavy Downpours In Texas And Most Of The Country. The National Climate Assessment, a flagship report from the U.S. Global Change Research Program on the state of climate science in the U.S., noted in 2014 that global warming has led to more extreme precipitation events in recent decades because warmer air “can contain more water vapor than cooler air.” Data from the report show that heavy precipitation events have increased by more than 10 percent in each decade since the 1970s in the “Great Plains South” region, which includes Texas, Oklahoma, and Kansas. The report projects that “the recent trend towards increased heavy precipitation events will continue” across the country. [National Climate Assessment, accessed 6/6/16]

Studies Suggest Climate Change Causes Extreme Precipitation Events To Persist. A study published in Geophysical Research Letters in August 2015 found that human-caused climate change can lead to prolonged extreme weather, concluding that global warming contributed to “the physical processes that caused the persistent precipitation” in Texas in May 2015. ThinkProgress explained of the study’s findings:

[T]he Geophysical Research Letters study found a much deeper link between human-caused climate change and the Texas floods. I asked the study’s lead author, Simon Wang of the Utah Climate Center, to explain the findings:

Basically, we linked the weather conditions that caused the consecutive and high amounts of rainfall to two main climate sources: (1) El Niño and its enhanced teleconnection owing to the warming Pacific temperature and (2) middle latitude circulation that is becoming increasingly “wavy,” causing the trough (or any ridge for that regard) to stick around for a long time.

The second conclusion — that climate change is causing weather patterns to stall — joins a growing body of research tying the recent jump in extreme weather to a warming-driven weakening of the jet stream and “more frequent high-amplitude (wavy) jet-stream configurations that favor persistent weather patterns,” as a January 2015 study put it.

Slate writer Eric Holthaus also recently noted the link between global warming and “stalled” or “blocked” weather patterns, citing a study by the Potsdam Institute for Climate Impact Research:

The National Weather Service had been warning of the potential for very heavy rainfall in southeast Texas since at least last Tuesday, as a continental-scale blocking pattern—in which an unusually stable jet stream locks weather systems in place—made conditions favorable for a stalled weather front to unload copious amounts of tropical moisture.

[...]

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.

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. [ThinkProgress, 8/13/15; Slate, 4/18/16]

Broadcast Networks Fail To Mention Climate Change In Texas Flood Coverage

ABC, NBC, CBS, And PBS All Failed To Connect Texas Floods To Climate Change. The four major broadcasting networks each covered the Texas floods on many occasions throughout April, May, and June, yet they each failed to even once mention the role of global warming in creating the conditions for extreme rainfall and flooding.*

By Contrast, CNN Meteorologist Noted Increase In Extreme Rainfall In U.S. And Said It Has The “Fingerprints” Of Climate Change. While discussing the Texas floods on the May 30 edition of CNN’s Newsroom, correspondent Errol Barnett asked senior meteorologist Derek Van Dam to explain why “it seems like we talk about flooding in the U.S. more frequently.” In response, Van Dam pointed to research from Climate Central showing that the number of days with extreme rainfall in the U.S. has increased drastically over the last several decades:

Van Dam also noted that Houston’s Free Press Summer Festival was forced to move locations for the second year in a row, stating that the “proof is in the pudding.” He concluded: “We talk about the frequency of heavy rain events on the uptick and, to me, that has climate change written all over it. It's got the fingerprints of it and it seems to be a common theme here in the weather department.”

[CNN, Newsroom, 5/30/16; Climate Central, 4/15/15]

Backslide: NBC And CBS Both Addressed Scientific Link Between Global Warming And Texas Floods Last Year

In 2015, NBC’s Nightly News Said Climate Change Was Exacerbating Texas’ “Weather Whiplash.” In May last year, NBC’s Nightly News featured a report about climate change-induced “weather whiplash” in the United States, including Texas' sudden shift from extreme drought to “crippling floods.” As national correspondent Miguel Almaguer explained, "In Wichita Falls, Texas, it felt like the drought ended overnight. In just three weeks, much of the state has gone from extreme drought to crippling flood. … scientists say climate change is exacerbating the wild swings.”

[NBC, Nightly News, 5/28/15; Media Matters, 6/2/15]

Similarly, CBS Evening News Explained In 2015 That Climate Change Can Lead To “Dangerously Wet” Conditions Like Texas Floods. On the June 1 edition of CBS Evening News, correspondent Kris Van Cleave noted that a study by researchers at Rutgers University found that “climate change in the Arctic is slowing the jet stream over the Northern Hemisphere,” resulting in prolonged weather conditions, including heavier rains and flooding in Texas. As Rutgers climatologist David Robinson explained during the CBS segment: “Everything slows, and with it, weather patterns persist over areas for longer periods of time. That could make a wet situation dangerously wet”:

[CBS, CBS Evening News, 6/1/15; Media Matters, 6/2/15]

*Based on a Nexis search for flood! w/40 (climate or global warming) from April 1, 2016, to June 5, 2016.