Summer drifts from drought to flood

Parts of North Texas, mired in a drought characterized as extreme and exceptional, are flooding under torrential rains. In a drought.

Sound familiar? It should. The Dallas area is just the latest region to suffer drought but flood during a summer of extreme weather, likely caused by human-caused climate change, scientists say. Parts of the world are plunging from drought to deluge.

The St. Louis area and 88% of Kentucky in early July were considered unusually dry, and then the heavens opened, rain fell in biblical proportions, inch after inch, and deadly floods devastated communities. The same thing happened in Yellowstone in June. Earlier this month, Death Valley, in a severe drought, saw near-record rainfall in one day, causing flooding, and is still in a bad drought.

China’s Yangtze River is drying up, a year after deadly floods. China is baking under a record-long heat wave, now in its third month, with a preliminary report of the overnight low temperature dropping to just 94.8 degrees (34.9 degrees Celsius) in the densely populated city of Chongqing . And in western China flooding from a flash downpour has killed more than a dozen people.

In the Horn of Africa, in the midst of a devastating but often ignored famine and drought, nearby flash floods add to the unfolding humanitarian disaster. Europe, which suffered from unprecedented flooding last year, has been battered by record heat exacerbated by a 500-year drought that is drying up rivers and threatening food supplies.

“So we’ve really had a lot of whiplash,” Kentucky Interim Climatologist Megan Szargorodsky said. “It’s really hard to emotionally go through all these extremes and overcome them and figure out how to be resilient in the disaster after the disaster that we’re seeing.”

In just two weeks in late July and early August, the U.S. had 10 rainfall events that are supposed to happen only 1 percent of the time — sometimes called 1-in-100-year storms — Weather Prediction Center chief forecaster Greg Carbin estimated. That’s not counting the Dallas area, a potential 1-in-1,000-year storm that saw some parts receive more than 9 inches of rain in the 24 hours through Monday that ended with several more inches predicted to follow.

“These extremes are naturally getting more extreme,” said National Center for Atmospheric Research climate scientist Gerald Meehl, who wrote some of the first studies 18 years ago on extreme weather and climate change. “This is in line with what we expected.”

The weather bump, “where it suddenly changes to the opposite” extreme, is more noticeable because it’s so strange, said climatologist Jennifer Francis of the Woodwell Climate Research Center in Falmouth, Massachusetts. He is in the middle of a study of the events of the whiplash.

World Weather Attribution scientists, mostly volunteers who quickly scan extreme weather events for a climate change fingerprint, have strict criteria for events to investigate: they must be record-breaking, cause a significant number of deaths, or affect at least 1 million People. So far this year they have been bogged down. There have been 41 events — eight floods, three storms, eight droughts, 18 heat waves and four cold waves — that have reached that threshold, said WWA official Julie Arrighi, the Red Cross Red Crescent’s deputy climate director.

In the United States, many of the major heavy summer rainfalls are traditionally associated with hurricanes or tropical systems, such as last year’s Hurricane Ida that hit Louisiana and then plowed south until it flooded the New York, New Jersey area with torrential rains. record.

But this July and August, the nation has been hit with “an abundance of extreme rainfall events not associated with the tropics,” said Carbin of the National Weather Service. “This is unusual.”

Scientists suspect that climate change works in two different ways.

The biggest way is simple physics. As the atmosphere warms, it holds more water, 4% more for each degree (7% more for each degree Celsius), the scientists said.

Think of the air as a giant sponge, said UCLA and Nature Conservancy climate scientist Daniel Swain. It soaks up more water from dry soil like a sponge “so we see worse droughts in some places,” he said. Then, when a weather system travels further, saturated with this extra water, it has more to drop, causing downpours.

Another factor is the stuck and more wavy jet stream — the atmospheric river that moves weather systems around the world — Woodwell’s Francis said. Storm systems don’t move and just dump huge amounts of water on certain spots. Other places, like China, are stuck with warm weather as cooler, wetter weather moves in around them.

“When that jet stream pattern strengthens, which we’re starting to see happen more often, that’s when we see more of these big events,” Francis said.

When the ground is so hard from drought, water doesn’t seep in as much and runs off faster in the event of a flood, Francis and others said.

That’s going to get worse as climate change gets worse, so it “highlights the type of events that we have to adapt to, that we have to harden,” said Princeton University climate scientist Gabriel Vecchi.

The United Nations Intergovernmental Panel on Climate Change has highlighted what it called dangerous weather disasters as a future threat.

“Honestly how fast and how badly it’s playing out now is a surprise to many of us,” said IPCC report co-author Maarten van Aalst, director of the Red Cross Red Crescent Climate Center in the Netherlands. “It’s scary how quickly it appears before our eyes.”

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Follow Seth Borenstein on Twitter at @borenbears

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