#megadroughts

Excerpt from this USA Today story:

Megadroughts – defined as intense droughts that last for decades or longer – once plagued the Desert Southwest. In fact, from the 9th to the 15th centuries, at least a dozen medieval megadroughts occurred across the region, scientists said.

Now, a study suggests that because of the drying influence of climate change, megadroughts could return to the region.

Megadroughts are defined more by their duration than their severity. They are extreme dry spells that can last for a decade or longer, according to the National Oceanic and Atmospheric Administration.

They've parched the West, including present-day California, long before Europeans settled the region in the 1800s.

How do scientists know how wet or dry it was centuries ago? Though no weather records exist before the late 1800s, scientists can examine paleoclimatic "proxy data," such as tree rings and lake sediment, to find out how much – or little – rain fell hundreds or even thousands of years ago.

If scientists can understand why megadroughts happened in the past, it can help better predict whether, how and where they might happen in the future, the new study said.

"In our paper, we present the first comprehensive theory for what caused historical megadroughts, which happened during the medieval period but not after about the year 1600," said study lead author Nathan Stieger of Columbia University's Lamont-Doherty Earth Observatory. "We find that they were caused by severe and frequent La Niñas, a warm Atlantic Ocean, and a net increase in energy from the sun."

Megadroughts lead to noteworthy decreases in precipitation, soil moisture and water levels. November 2, 2025 by EarthTalk Leave a Comment   By Shashwat Mishra Dear EarthTalk: What (and where) are megadroughts and what’s their relation to climate change? — Kory Smith, Providence, RI Megadroughts are severe droughts that last for decades and affect entire regions,even millions of square miles.…

Megadroughts Brought by Climate Change a Challenge for Texas Ranchers

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Arthur Uhl III has been ranching for 30 years and routinely has the same lament: “It doesn’t rain enough.”

Uhl, who works on his family’s San Angelo-area ranches, needs the rain to grow the grass that feeds his livestock. But in a region that’s prone to megadroughts, he’s had to make changes for sustainability’s sake.

“We meter all of our groundwater posts, for one thing,” he said.…

Excerpt from an article from the Arizona Republic, authored by one of my friends, Ian James:

Since 2000, the West has been stricken by a dry spell so severe that it ranks among the biggest "megadroughts" of the past 1,200 years. But scientists have found that unlike the decades-long droughts of centuries ago, this one has been supercharged by humanity's heating of the planet.

Researchers analyzed the dry and wet cycles that have swept across western North America over centuries by examining the ancient records inscribed in the growth rings of trees.

Cores extracted from thousands of trees enabled the researchers to reconstruct soil moisture and examine the West’s hydrological history, including long droughts that appear as sets of narrow growth rings running through the wood.

Using data from trees at 1,586 sites across the region, from Montana to northern Mexico, the scientists identified four other intense droughts, in the late 800s, the mid-1100s, the 1200s and the 1500s.

The driest 19-year period struck in the late 1500s, and the second-worst drought of that duration has afflicted the region since 2000.

The research team, led by scientists at Columbia University’s Lamont-Doherty Earth Observatory, also used 31 climate models to estimate the influence of higher temperatures unleashed by climate change from 2000 through 2018.

They found the region’s average temperature during those years was 1.2 degrees Celsius (2.2 degrees Fahrenheit) hotter than it would have been without human-caused warming, and they estimated climate change was responsible for 47% of the drought’s severity.

The scientists concluded that in fueling the drought, global warming has turned what would otherwise have been a relatively moderate event into one of the most severe megadroughts since 800 A.D.

The findings, published April 17 in the journal Science, add to the growing body of research revealing major challenges for the American West as the planet heats up with the burning of fossil fuels.

As temperatures rise, the region is being ravaged by more dangerous heat waves and more intense wildfires. And the hotter, drier conditions of the past two decades offer a preview of how climate change will continue to complicate efforts to manage water in the arid West, where rivers and groundwater basins were already being over-pumped before rising temperatures piled on added pressure.

News from Hal Lindsey Media Ministries

In 1835, Charles Darwin was in the midst of one of his famous voyages aboard the HMS Beagle. He and his party were near Concepción, Chile, when the area was struck by a massive earthquake. Historians estimate it to have been an 8.2 magnitude quake.

Darwin wrote that the quake “came on suddenly, and lasted two minutes, but the time appeared much longer.” As someone who has been through earthquakes…

Megadroughts & Climate Change: Prof Toby Ault (February 2016).

Megadroughts explained.

Associated Press, October 7, 2016

Already dealing with parched conditions, the American Southwest faces the threat of megadroughts this century as temperatures rise, says a new study that found the risk is reduced if heat-trapping gases are curbed.

Oppressive dry spells lasting at least two decades have gripped the Southwest before, but scientists said future megadroughts would be hotter and more severe, putting a strain on water resources.

The study, published in the journal Science Advances, is the latest to find that droughts more extreme than what is currently being experienced could become more common as the planet warms.

Using computer modeling, researchers calculated that there is a 70 to 90 percent chance the Southwest will experience a megadrought this century.

If precipitation is below normal, the risk jumps to 99 percent--”virtually certain,” said lead researcher Toby Ault of Cornell University.

The Colorado River basin, which spans parts of Arizona, California, Colorado, New Mexico, Nevada, Utah, Wyoming and Mexico, has been in the midst of a historic drought for the past 16 years. Lake Mead is now surrounded by a distinctive white mineral “bathtub ring” showing the 130-foot drop in water levels since the beginning of the regional drought.

California, which is entering a sixth year of exceptional dryness, imposed mandatory statewide cuts on water usage last year that left brown lawns and fallowed fields. Restrictions have since eased with local water districts taking control of conservation efforts. On Wednesday, state regulators said some water districts are not conserving enough.

The new forecasts of a future megadrought are “scary for sure,” said Jonathan Overpeck, a University of Arizona climate scientist who wasn’t involved in the research.

Based on studies of tree rings and other data, past megadroughts in the Southwest have lasted between 20 and 35 years.