Milwaukee Journal Sentinel

Extreme weather shows shift in rainfall

Heat changing moisture levels across country

- Dinah Voyles Pulver and Kevin Crowe USA TODAY

Over eight days of wild weather in June, the realities of a changing climate grabbed the nation by its shoulders and shook.

In Michigan, a deluge dropped 7 inches of rain in Detroit, swamping highways and stranding cars.

At least 136 daily rainfall records were set during storms across five states along the Mississipp­i River.

Tropical Storm Claudette soaked a swath of the South, flooding homes in Louisiana and in Alabama, where it dropped up to 8 inches of rain and claimed 14 lives.

Meanwhile, the drought-stricken West grappled with soaring temperatur­es that shattered century-old records, prompted heat warnings and ultimately killed more than 200 people.

Wildfires exploded in Montana and scorched the earth in California.

Such events do occur naturally, but rarely have so many struck at once or to such an extreme degree, making it hard to ignore their connection to each other and to a warming world.

Rising temperatur­es and rising oceans have for years been framed as the impending disasters on the crest of climate change. But this year, like few before it, changing rainfall patterns bullied their way into the collective consciousn­ess.

USA TODAY reporters analyzed more than a century of precipitat­ion records from the National Oceanic and Atmospheri­c Administra­tion and a unique collection of snow and rain extremes computed by Alaska-based climate researcher Brian Brettschne­ider.

Reporters read thousands of pages of climate assessment­s, scientific papers, weather reports and government documents. They interviewe­d more than 70 people, including climate scientists, academic researcher­s, local and federal officials, and residents forced from their homes by drought and flood.

Taken together, the reporting reveals a stunning shift in the way precipitat­ion falls in America.

Heat has changed how moisture moves across the country. Scientists say it alters the flow of the jet stream, extends droughts, and increases evaporatio­n from land and from bodies of water, including the Atlantic and Pacific oceans, the Great Lakes and the Gulf of Mexico.

East of the Rockies, more rain is falling and it’s coming in more intense bursts. In the West, people are waiting longer to see any rain at all.

Readings from hundreds of rain gauges across the continenta­l U.S. tracked for more than 100 years reveal a noticeable inflection point before the turn of the 21st century.

Of 285 weather stations, 44% get at least one more top rainfall event per year now than they did three decades ago, based on data compiled by Brettschne­ider. That means what used to count as the top three wettest rainfalls of the year now happen at least four times a year.

Nineteen places doubled their previous number of days of extreme precipitat­ion – from three a year to six.

As deluges grow in frequency and severity, annual precipitat­ion has increased for more than half the nation. At some point over the past three years, 27 states – all east of the Rocky Mountains – experience­d their highest 30-year average since record keeping began in 1895, according to a USA TODAY analysis of NOAA data.

A dozen states, including Iowa, Ohio and Rhode Island, saw five of their 10 wettest years in history over the past two decades.

At the opposite extreme, eight states – including five in the West – had at least three record-dry years in the same time period. That’s double what would be expected based on historical patterns.

As states rack up records for rainfall, flooding, droughts and wildfire, it’s becoming clear our country was built for the climate of the past.

Roads, bridges, sewer systems and entire communitie­s that decades ago seemed safe from fire and flood now lie within one or both danger zones.

An October report by the nonprofit First Street Foundation warned that one-fourth of the nation’s “critical infrastruc­ture,” including roads, utilities, airports and emergency services, now faces flood risk from rainfall and sea level rise, as do 1 in 7 residentia­l properties – about 12.4 million.

Heat, lack of humidity, and wind are combining more frequently to enhance the risk of wildfire. Climate Central, a nonprofit research organizati­on, looked at 17 Western states and found parts of New Mexico now have at least 60 additional days when the fire risk is more extreme than 50 years ago.

Parts of 11 other states, including Arizona, California, Colorado, Oregon and Texas, saw more than a 100% increase in these “fire weather days.”

These calamities displace families, claim lives and leave officials from coast to coast conflicted over which crisis to plan for next and how to pay for it all.

NOAA reported at least 133 “billiondol­lar disasters” in the decade ending in 2020, double the previous decade, at a cost of more than $867 billion. Meanwhile, the annual average number of flood claims paid by FEMA also doubled between 1997 and 2020, to 52,000.

Scientists say it’s too late to stave off some of the climate change-driven precipitat­ion extremes we’re experienci­ng today. But the nation could take steps to reduce greenhouse gas emissions that amplify the weather extremes and take more aggressive measures to reduce flood risk.

Given the increasing frequency of weather disasters, “one would think the nation might be galvanized to action,” said Rob Moore, a senior policy analyst with the Natural Resources Defense Council. “And yet we are not incorporat­ing what we know about the future into our decisions about what we build, where we build and how we build as a nation.”

What’s causing it?

The earth has always produced erratic weather patterns. But now the heaviest downpours and droughts are growing more extreme. That trend started in the late 20th century, as the accumulati­on of greenhouse gases like carbon dioxide and methane reached critical levels in the atmosphere.

Climate scientists said these gases trap more of the energy radiating from the planet’s surface, causing the earth to warm.

This warming doesn’t just raise temperatur­es. It intensifies how water cycles between earth and sky.

Heat hastens evaporatio­n. It draws more water into the air where it gathers into systems that can form wetter storms. For every 1.8 degrees Fahrenheit of warming, 7% more moisture is absorbed, said David Easterling, director of NOAA’S National Climate Assessment Technical Support Unit.

It’s one of the reasons behind many of this summer’s rainiest storms, including Hurricanes Henri and Ida, that flooded communitie­s throughout the South and Northeast this August.

For these storms and others throughout the year, much of their moisture comes from the Gulf of Mexico, Great Lakes and Atlantic Ocean.

Gulf waters alone have warmed about 1.3 degrees over the past four decades.

A warmer Gulf contribute­s to more rainfall in hurricanes and tropical storms, but its moisture also helps form wetter storms as far north as Wisconsin, Easterling said.

At the same time, some scientists said rising temperatur­es have altered the summertime movement of the jet stream that transports moisture across the country. Weather systems that used to hustle along get stalled more often now, dumping more rain in one place.

Instead of flowing quickly across the north, the jet stream moves slower and gets bigger, wavy dips that trap high and low pressure systems in place, said Michael Mann, a climatolog­ist at Penn State University and author of the book “The New Climate War.”

The trapped highs and lows in the summertime affect the weather across the country, Mann said. For example, they can produce extreme heat, drought and wildfires in the West and drop huge amounts of rain to the east at the same time.

Scientists can’t say for sure how much of the rain in each storm is directly attributed to the changing climate, Brettschne­ider said, but the shifts become apparent when comparing a sampling of current and older events.

More intense rains

Climate change also has been blamed for fueling the intensity of the storms that unleashed record rainfall and sparked deadly flooding across Tennessee in August.

The day that storm hit started like just another rainy morning in Humphreys County.

Weather forecaster­s had issued flash flood advisories, warning of 2-4 inches of rain, but no one had predicted four times that much or the catastroph­e it would bring.

Typical summer thundersto­rms sweep through at 50-60 mph. But on Aug. 21, a system got caught up with a stalled front and traveled through at only 10-15 mph. Meeting up with a pool of Gulf moisture overhead, it forced storms to rain over the area again and again, dropping more than 12 inches of rain in seven hours in the small city of McEwen.

The total rainfall – 17 inches – broke the state’s all-time record and triggered deadly flooding in Waverly.

Around 7 a.m., Joe Duncan looked outside and saw water rushing through his yard. He gathered his wife, daughter and two grandchild­ren and headed out through knee-high water to pick up his mother so they could evacuate. When they reached her house, Duncan turned around just in time to see his mobile home tilt sideways.

By this time, 9 inches of rain had fallen in six hours, sending Trace Creek out of its banks and raging toward Waverly in a muddy torrent.

Calls started lighting up the

Humphreys County 911 Center.

The debris-filled Trace Creek hurtled toward a pair of bridges east of Waverly – one for U.S. 70 and one for the railroad. Mayor Buddy Frazier and others believe debris lodged at the bridges, creating a temporary dam until the water crashed through and sent a “tsunami” into Waverly.

Duncan’s home slammed against a tree and split into three pieces. He said the nearby home built in the early 1900s also was destroyed.

Twenty people died in the disaster. They’re among 144 flood-related deaths in the nation this year, the second-highest since 1985.

Rising temperatur­es also lengthen dry spells, creating wild swings between downpours and droughts.

The length of time between rain increased by three days on average across the West from 1976 to 2019, according to research published this year by scientists with the U.S. Department of Agricultur­e and the University of Arizona.

The researcher­s also found the longest interval between rains each year increased by 11 days in the West, to 32 days across the region. In the desert Southwest, it increased by 17 days to 48 days.

More dry days and drought

While increasing­ly intense rains fall east of the Rockies, the West experience­s intense drought. Rising temperatur­es and lingering high pressure systems zap greater moisture from soils and plants.

“With precipitat­ion you’re only getting half of the picture,” said Daniel Swain, a climate scientist at UCLA and the National Center for Atmospheri­c Research. “When it comes to drought, temperatur­e is increasing­ly important, and temperatur­es are rising a lot.”

Together, the intense heat and longer intervals between rains contribute to the conditions creating more recordbrea­king wildfires in the West.

All but two of California’s 20 largest wildfires in history have happened since 2003.

Oregon had one of its most destructiv­e wildfire seasons on record last year with roughly 2,200 fires that burned more than 1.1 million acres and destroyed more than 4,000 homes.

One of those homes belonged to the Flores family, who lived in the Coleman Creek Estates mobile home park near Medford in the southern part of the state.

Seventeen years old at the time, Julio Bryan Flores woke up the morning of Sept. 8, 2020, looking forward to celebratin­g his mother’s birthday when a neighbor’s call alerted the family to danger, he said.

Soon ash fell from the sky. The entire neighborho­od evacuated. Bryan’s father, who had been away, returned home just in time to get the dog, but not his mechanics tools.

“We could see fires literally starting everywhere,” Bryan said. “We were surrounded by them.”

The family escaped, but the fire destroyed their home and possession­s. When Bryan and his dad returned a week after the fire, “it was a nightmare.”

“There were just the colors white and black everywhere, burned bicycles, destroyed cars, toys left on the street, just burned,” Bryan said.

Once an intense wildfire burns through an area, it leaves the soil hardened and scarred and weakens its ability to absorb water. So when the rains come, they turn dry creek beds into raging rivers, like the one that swept up a Prius near Flagstaff, Arizona, in August and carried it down the street in a viral video.

The atmospheri­c river that swept across the West in late October dropped anywhere from 3 to 13 inches of rain across California, Oregon and Nevada.

Action needed now

Critical steps are needed – and soon – to try to keep downpours from growing ever more intense, correct past mistakes and adapt our surroundin­gs to the new reality, experts said.

Many call for sweeping changes to curtail warming, upgrade stormwater and utility systems, and revamp federal guidelines and standards and stop building in vulnerable places.

“The future is still in our hands,” said Mann.

Two things appear to be true for “pretty much everywhere that’s populated and on land,” Swain said. “Everyone is getting warmer and everyone is seeing, or should see shortly, more intense precipitat­ion events.”

Part of the problem is the nation’s woefully outdated federal precipitat­ion estimates and inadequate flood zone mapping, said Moore of the Natural Resources Defense Council. Neither takes into account recent rainfall increases, much less future projection­s.

“We’re still designing highways and stormwater systems and siting people’s homes without any considerat­ion of what the weather is going to look like in 30, 40 or 50 years,” Moore said.

Changing rainfall amounts and rising sea levels mean the estimates, such as a 1-in-100 year flood or a 1-in-25 year rainfall, just aren’t the same as they used to be.

The NOAA estimates guide government­s, engineers and others when designing infrastruc­ture. A new generation of estimates, called Atlas 14, began in 2002, but has never been completed for the entire country.

One study showed that for Michigan, Wisconsin, Iowa and Minnesota, the historic estimate of a 1-in-100-year storm is now a 1-in-40-year storm, said Daniel Wright, an assistant professor of civil and environmen­tal engineerin­g at University of Wisconsin-Madison. “These sorts of storms are happening 21⁄2 times as often as they should be.”

Labeling storms as a once-in-a-generation occurrence gives people the impression they can’t have another, said Peter Schultz, vice president of climate adaptation and resilience for ICF, an internatio­nal climate change consulting firm.

But that’s not accurate.

“If you have dice and you roll a three, that doesn’t mean the next time you roll the dice you can’t get a three, you absolutely can,” he said. “Nature is still rolling the dice, but it’s not fair dice anymore, it’s dice that are coming out toward those higher numbers.”

“With precipitat­ion you’re only getting half of the picture. When it comes to drought, temperatur­e is increasing­ly important, and temperatur­es are rising a lot.” Daniel Swain Climate scientist at UCLA and the National Center for Atmospheri­c Research

 ?? ERIC SEALS/DETROIT FREE PRESS/USA TODAY NETWORK ?? Heavy rains in Metro Detroit caused massive flooding in homes, streets and freeways June 26.
ERIC SEALS/DETROIT FREE PRESS/USA TODAY NETWORK Heavy rains in Metro Detroit caused massive flooding in homes, streets and freeways June 26.
 ?? GERALD HERBERT/AP ?? Tropical Storm Claudette flooded a neighborho­od in Slidell, La., on June 19.
GERALD HERBERT/AP Tropical Storm Claudette flooded a neighborho­od in Slidell, La., on June 19.

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