#aridification

Excerpt from this story from Daily Kos:

The Southwest, scientists tell us, is undergoing the worst drought in at least 1,200 years. That’s based on tree-ring analysis for the Upper Colorado River Basin that reaches back to 762 C.E. But one study published in June says it’s even worse than that. “The reconstruction reveals a second-century drought unmatched in severity by the current drought or by well-documented medieval period droughts in the UCRB,” the authors state.

That’s the kind of scientific knowledge that some foes of taking serious preventive and ameliorative action to address climate change like to twist into support for their stance. See, they say, the climate is always changing, making action futile, even harmful since it requires broad—and they claim, unnecessary—societal transformation. You may remember that many such critics not so long ago were saying climate change is a hoax, not a crisis.

It’s a truism that the climate is always changing. But those past Southwest megadroughts occurred centuries before humans started pouring carbon emissions into the atmosphere. The politicians, plutocrats, and pundits who spout the climate-is-always-changing defense of inaction depend on an inaccurate understanding of what this has wrought during the industrial age of the past 250 years. The rapidity of what’s now happening is unprecedented in the previous hundreds of thousands of years, possibly longer.

The details of how the situation will play out in the American Southwest is unknown. But many scientists believe the region is undergoing long-term aridification. A few millenniums ago, aridification in the basin lasted for 4,000 years. If we humans don’t get our carbon emissions under control, and very, very soon, the possibility lurks that that distant dry stretch could be short by comparison. But the variables aren’t easy to parse.

The river flow has dwindled so far that officials have been concerned that Lake Powell and Lake Mead, the nation’s two largest reservoirs, already are at their lowest level since they were dammed many decades ago. Officials are concerned that the levels are so low the Glen Canyon Dam and Hoover Dam might not be able to generate any electricity.

What if the dust bowl happened again?

Cuz reading on it, it sounded like a nightmare!

Lasted EIGHT FUCKING YEARS!

The flexibility and ability to adapt to changing climates by employing various cultural innovations allowed communities of early humans to survive through a prolonged period of pronounced aridification.

The early human techno-tradition, known as Howiesons Poort (HP), associated with Homo sapiens who lived in southern Africa about 66 000 to 59 000 years ago indicates that during this period of pronounced aridification they developed cultural innovations that allowed them to significantly enlarge the range of environments they occupied.

Eric Richins, owner of Big Water Boating, surveys water levels and fish on Lake Mead, where he has led tours for two years.(Allen J. Schaben / Los Angeles Times)

Excerpt from this LA Times story:

Lake Mead, a lifeline for 25 million people and millions of acres of farmland in California, Arizona, Nevada and Mexico, made history when it was engineered 85 years ago, capturing trillions of gallons of river water and ushering in the growth of the modern West.

But after years of an unrelenting drought that has quickly accelerated amid record temperatures and lower snowpack melt, the lake is set to mark another, more dire turning point. Next month, the federal government expects to declare its first-ever shortage on the lake, triggering cuts to water delivered to Arizona, Nevada and Mexico on Jan. 1. If the lake, currently at 1,068 feet, drops 28 more feet by next year, the spigot of water to California will start to tighten in 2023.

The crisis, said Eric Kuhn, former general manager of the Colorado River Conservation District, can no longer be ignored. “According to Merriam-Webster, a drought is a temporary condition,” he said. What is happening, he suggested, is something more permanent and troubling. “This is aridification.”

Excerpt from this story from National Geographic:

Water levels usually peak in May at Folsom Lake in California, rising as Sierra Nevada snowpack melts away and courses down to the reservoir, near Sacramento.

But this year, the drought that has gripped much of the U.S. West is already so strong that the lake is only half as full as normal. Instead of water, fields of purple lupines line vast swaths of dry lakebed.

Folsom Lake’s situation is emblematic of the deepening drought across the western United States. As of May 6, 67 percent of the region was in a state of “severe” drought or worse; a stunning 21 percent is already in “exceptional” drought, the worst category in the U.S. Drought Monitor’s framework. At Lake Mead, one of the two major reservoirs of the Colorado River, which some 40 million Americans depend on, water levels are creeping toward a threshold that would trigger the first official shortage declaration for the basin.

The situation is unlikely to improve in the near future, scientists say, as 2021 shapes up to extend the “megadrought” that researchers have found to be gripping the region mostly unabated since 2000.

The region would have been in a state of drought regardless, “but it’s really climate change that pushed this event to be one of the worst in 500 years,” says Ben Cook, a climate scientist at Columbia’s Lamont Doherty Earth Observatory.

Drought can take many forms. There’s “meteorological drought,” which compares how much rain or snow has fallen compared to a long-term average. There’s “hydrological drought,” which considers how much water flows through streams and rivers and is stored in mountain snowpack and underground aquifers. There’s the drought the soil, plants, and animals feel, called agricultural or ecological drought.

This year, by just about every measure, the West is extremely low on water. Most of California and the Four Corners states are somewhere between 25 and 50 percent of their long-term averages on most of the drought indicators. Snowpack in California on April 1, its usual peak time, hit only 59 percent of its long-term average and has already largely melted away, leaving it at a paltry 15 percent of its average at this date. Soils are parched. The Colorado and Rio Grande rivers are trickling compared to their long-term histories.

Excerpt from this story from InsideClimate News:

The ancient people of Danger Cave lived well. They ate freshwater fish, ducks and other small game, according to detritus they left behind. They had a lush lakeside view, with cattails, bulrush and water-loving willows adorning the marshlands.

But then, the good life became history. As heat and drought set in, the freshwater dried up and forced the ancients to survive by plucking tiny seeds from desert shrubs called pickleweed. Archaeologists know this from a thick layer of dusty chaff buried in the cave's floor.

It might be ancient history. But the past could also become the future, science tells us. In fact, thanks to global warming, regional climate patterns linked to extended periods of heat and drought that upended prehistoric life across the Southwest thousands of years ago are setting up again now.

The climate risk across the Southwest is actually growing, based on Lachniet's recent study of a different cave, about 200 miles across the Great Basin in Nevada.

His geochemical data from Leviathan Cave shows that drought can last 4,000 years—findings that Lachniet's team cross-checked against paleoclimate data from the Arctic and tropical Pacific. In short, the story in the cave data suggests a "worst-case scenario" that could—and probably should—guide planning throughout a region that provides water to 56 million people.

Excerpt from this story from Yale Climate Connections/EcoWatch:

Colorado is no stranger to drought. The current one is closing in on 20 years, and a rainy or snowy season here and there won't change the trajectory.

This is what climate change has brought.

"Aridification" is what Bradley Udall formally calls the situation in the western U.S. But perhaps more accurately, he calls it hot drought – heat-induced lack of water due to climate change. That was the core of research released in 2017 by Udall, a senior climate and water scientist at Colorado State University's Colorado Water Center, and Jonathan Overpeck at the University of Michigan.

Their revelation was that the heat from climate change was propelling drought. "Previous comparable droughts were caused by a lack of precipitation, not high temperatures," the study said. And all the factors at play were having compounding effects on each other that made the situation even worse. Those impacts were being felt most acutely on the biggest water system in the West – the Colorado River Basin.

Without a dramatic and fast reversal in greenhouse gas emissions to slow climate change, Udall and Overpeck said, the additional loss of flow in the basin could be more than 20% by mid-century and 35% at the century's end – worse than currently assumed.

Excerpt from this article from The Revelator:

After nearly two decades of declining water flows into the Colorado River Basin, scientists have decided the word drought doesn’t cut it anymore. We need different terms, they say, to help people fully grasp what has happened and the long-term implications of climate change — not just in the Southwest, but across the country.

The term that’s caught the most attention lately is “megadrought.”

It’s not a new word, but it’s one that’s come sharply into focus in recent months, following a study published this April in the journal Science that found the North American Southwest has experienced an abnormally severe drought over the past two decades — its second driest stretch in 1,200 years.

The researchers, led by A. Park Williams of the Lamont-Doherty Earth Observatory of Columbia University, say this prolonged megadrought — which reached from Oregon and Idaho down to northern Mexico — would likely have been just a bad drought if not for climate change. The increase in temperatures from our burning of fossil fuels supercharged naturally varying conditions, creating one of the worst megadroughts in human history.

The current megadrought in the Southwest is defined not so much by declining precipitation — although that did have an effect too — but by increasing temperatures from climate change.  That’s going to continue to climb as long as we keep burning greenhouse gases.

In a 2018 paper the Colorado River Research Group, which includes Udall and Overpeck, called for new language to describe the scientific reality on the ground. The term “drought,” they wrote, wasn’t accurate.

“Aridification,” they argued, was a more fitting description.

The semantics here are important.

Aridification, they explained, “describes a period of transition to an increasingly water scarce environment — an evolving new baseline around which future extreme events (droughts and floods) will occur.”