Water levels are running dangerously low in reservoirs across the U.S. Southwest. Declining flows in the Gila River have pushed levels to below 1 percent of capacity in Arizona’s San Carlos Reservoir
The Western U.S. is grappling with an extended drought. Nikk Ogasa explores the possibility that this continued dryness (and the fires and other hazards associated with it) could be our new climate change induced reality…
Kearny, Ariz., is a town on the brink. Located at the foot of the Dripping Spring Mountains in eastern Arizona, this small community of 2,000 people sources its water from the Gila River, a verdant waterway that snakes by the southern edge of town.
But in March, the snowpack feeding the river had dropped to precipitous levels: It was just 1 percent of its historic norm for that time of year. The Gila River water commissioner slashed Kearny’s allotment of river water by some 85 percent. And in April, town officials announced that “Zero Day” was approaching, at which point the taps would run dry.
“We need rain,” says Norm Warren, a lifelong Kearny resident. He owns the only large grocery store within a 45-minute drive of the town. Without tap water for refrigerator cooling systems, Warren says he won’t be able to store perishable products like meats and fresh produce.
Kearny’s dilemma foreshadows a crisis building across the American Southwest. Since 2000, the region — which includes Arizona, New Mexico, California, Utah, Colorado and parts of northern Mexico — has endured a historic “megadrought,” or a period of severe dryness that persists for decades. Scientists say it’s the driest this region has been in 1,200 years.
“We’re 27 years into it, and it shows no signs of letting up,” says Brad Udall, a water and climate researcher at Colorado State University in Fort Collins.
Scientists point to two factors causing the drought — rising temperatures and declining precipitation. Heat from human-caused climate change creates a thirsty atmosphere that is more effective at drying out the landscape, says Kevin Anchukaitis, a dendrochronologist who runs the University of Arizona Laboratory for Tree-Ring Research in Tucson. As for the lack of rain, many researchers wonder if it is simply a stroke of bad luck.
But a controversial study published in Nature in 2025 suggests something far more ominous: Humankind has disrupted a naturally occurring climate cycle in the Pacific Ocean that historically ushered episodes of wet weather into the Southwest. If that’s true, Udall says, things are not looking good for places like Kearny. Other researchers worry that the megadrought may be locked in place for the foreseeable future…
[Ogasa unpacks both the more traiditional analysis and the new hypothesis– that human behavior has disrupted the Pacific Decadal Oscillation, or PDO, an alternating climate pattern in which areas of warmer and cooler than normal surface waters switch their positions on a timescale of many decades…]
… “The conventional wisdom suggested that the PDO could shift any given year, and we [wouldn’t] have to worry about drought [after that],” says climate scientist Jeremy Klavans of the University of Miami.
But he and colleagues weren’t so sure. They dug into that assumption, analyzing more than 500 simulations of the PDO from a dozen major climate models. They examined how the PDO shifted — and stabilized — in the presence of outside forces such as volcanic eruptions, solar variation and levels of greenhouse gases and aerosols.
Their finding: Greenhouse gas and aerosol emissions had effectively hijacked the behavior of the PDO over the last 50 years by altering atmospheric temperatures, the team reported in 2025 in Nature.
Ballooning concentrations of industrial aerosols — which can have an atmospheric cooling effect — probably pushed the PDO to increasingly favor its warm phase starting in the 1950s, the researchers say. But in the 1980s, clean air legislation decreased aerosol emissions even as greenhouse gas levels continued to rise and warm the atmosphere. That combination drove the PDO toward its cool phase, making drought conditions more likely in the Southwest. Instead of being a rare event, drought “becomes kind of commonplace,” Klavans says….
… the current climate models may actually be underestimating the potential duration of the ongoing megadrought, based on those findings, says study coauthor Victoria Todd, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo.
That could be bad news for the American Southwest, Udall says. Even if people stopped emitting greenhouse gases today, planet-warming carbon dioxide will continue to accumulate in the atmosphere, locking the PDO and megadrought into place, potentially for decades. If the emerging science is right, then the Southwest is going to keep getting drier and drier, Udall says. “No question about it.”
Warm Phase (1977-1998): During the PDO’s warm phase, the Pacific jet stream (red arrow) moves south over North America, drawing wet weather patterns into the Southwest.
Cool phase (1999–now): When the PDO switches to its cool phase, the Pacific jet stream (blue arrow) moves north, diverting wet weather patterns out of the Southwest and making drought more likely.
The hypothesis that human emissions have disrupted the PDO could be put to the test this year. That’s because scientists are predicting a historically strong El Niño, a Pacific climate pattern characterized by months of warmer than normal sea surface temperatures in the eastern equatorial Pacific. El Niños often bring wet conditions to the Southwest — and they have been known to force the PDO into a different phase. For example, the 1976–1977 El Niño helped push the PDO into a warm phase for nearly a quarter of a century.
But a powerful El Niño in 2015 wasn’t able to force the switch for more than a few years. That suggests the PDO may be slowly changing, Klavans says. “Something’s different here.”
Even if the current El Niño is strong enough to force the PDO into a warm phase, no one should expect the megadrought to go away any time soon, Seager says. “We’re talking about something that’s been going on for a few decades now. Even one very wet winter is not going to be enough to restore Colorado River reservoirs to where they would preferably be.”…
… Even in the best-case scenarios, the Southwest never returns to the wet years of the 1980s and ’90s, when lakes Powell and Mead reached maximum capacity numerous times, the researchers reported in 2023 in npj Climate and Atmospheric Science. The findings instead suggest that, regardless of what the PDO does, the region will face a far drier climate than it did in its recent past. In other words, even if the megadrought were to end, the Southwest faces an uncertain future when it comes to water, according to the study.
Communities need to prepare for the future by improving their water conservation efforts and infrastructure, Anchukaitis says. Those practices will grow only more crucial as the Southwest’s population continues to balloon: Utah, Texas, Nevada, Colorado and Arizona are among the 10 fastest growing states by population this decade, according to a 2024 report by the University of Virginia’s Weldon Cooper Center for Public Service.
Even if wet weather returns, Anchukaitis says, the cities of the Southwest shouldn’t fall into complacency. “[More rain] doesn’t mean that … megadroughts aren’t going to come back,” he says. “Maybe it buys us some time to ease systems into a new way of thinking.”…
As we pray for rain, we might recall that it was on this date in 2006 that NASA recorded th largest ozone hole in the atmosphere to date. From September 21-30, the average area was 10.6 million square miles, as measured by the Ozone Monitoring Instrument on NASA’s Aura satellite. At the worst point, a record low of 1.2 Dobson Units compared to a 125 DU non-hole reading. For the past several decades, each year during the Southern Hemisphere Spring (Northern Hemisphere Autumn) chemical reactions due to chlorine and bromine man-made compounds in the atmosphere cause the destruction of ozone in the stratosphere over the southern polar region… all contributing to the phenomenon discussed above.
False-color view of total ozone over the Antarctic pole. The purple and blue colors are where there is the least ozone, and the yellows and reds are where there is more ozone. (source)
… and it’s likely, climate scientists Matthew Barlow and Jeffrey Basara suggest, to get more uncomfortable still…
… Although heat waves are a natural part of the climate, the severity and extent of the heat waves so far this year are not “just summer.”
A scientific assessment of the U.S. heat wave estimates that heat this severe and long-lasting was two to four times more likely to occur today because of human-caused climate change than it would have been without it. This conclusion is consistent with the rapid increase over the past several decades in the number of U.S. heat waves and their occurrence outside the peak of summer…
… Although heat waves are a natural part of the climate, the severity and extent of the heat waves so far this year are not “just summer.”
A scientific assessment of the U.S. heat wave estimates that heat this severe and long-lasting was two to four times more likely to occur today because of human-caused climate change than it would have been without it. This conclusion is consistent with the rapid increase over the past several decades in the number of U.S. heat waves and their occurrence outside the peak of summer…
At the peak of the last ice age, some 20,000 years ago, when the Northeast U.S. was under thousands of feet of ice, the globally averaged temperature was only 10.8 F (6 C) cooler than now. So, it is not surprising that 2.2 F (1.2 C) of warming so far is already rapidly changing the climate.
Countries promised in 2015 as part of the Paris Agreement to keep warming well under 2 C, but current government policies around the world won’t meet those goals. Temperatures are on pace to continue rising, with the increase likely to more than double again by the end of the century.
While this summer is likely be one of the hottest on record, it is important to realize that it may also be one of the coldest summers of the future…
* Jane Austen, in a letter to her sister dated 18th September, 1796
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As we chill, we might recall that it was on this date in 1922, the day before his 19th birthday, that Ralph Samuelson invented water skiing. Samuelson had already mastered aquaplaning (riding on a sheet of wood while being pulled by a powerboat) but wanted a summer equivalent of snow skiing. He had unsuccessfully tried barrel staves and snow skis before succeeding with 8 foot long pine boards, the front tip of which he bent up (by boiling them in his mother’s kettle). His first successful outing, on a wide portion of the Mississippi River near Lake City, Minnesota, involved starting on an aquaplane, then stepping off onto the skis.
Samuelson didn’t patent his invention, nor was his work sufficiently publicized at the time to prevent U.S. Patent 1,559,390 for water skis from being subsequently issued, on October 27, 1925, to prolific inventor Fred Waller, who marketed his product as “Dolphin Akwa-Skees.” (Waller also invented Cinerama, which he used to publicize his skis…) Still, Samuelson, who became a turkey farmer, was a guest of honor at a water skiing 50th anniversary in 1972, and was inducted into the Water Ski Hall of Fame in 1977. His slightly-modified second pair (the first pair broke) still exists, and are on display at the Lake City Chamber of Commerce.
Flash floods in the Libyan city of Derna were the most deadly climate disaster of 2023, killing 11,300 people
The estimable Jonathan Watts on the (painfully) pivotal year just ended…
As historically high temperatures continued to be registered in many parts of the world in late December, the former Nasa scientist James Hansen told the Guardian that 2023 would be remembered as the moment when failures became apparent.
“When our children and grandchildren look back at the history of human-made climate change, this year and next will be seen as the turning point at which the futility of governments in dealing with climate change was finally exposed,” he said.
“Not only did governments fail to stem global warming, the rate of global warming actually accelerated.”…
The bright side of this clear dichotomy is that young people may realise that they must take charge of their future. The turbulent status of today’s politics may provide opportunity,” he said.
Veteran climate watchers have been horrified at the pace of change. “The climate year 2023 is nothing but shocking, in terms of the strength of climate occurrences, from heatwaves, droughts, floods and fires, to rate of ice melt and temperature anomalies particularly in the ocean,” Prof Johan Rockström, the joint director of the Potsdam Institute for Climate Impact Research in Germany, said.
…
Aquino [Francisco Eliseu Aquino, a professor of climatology and oceanography at the Federal University of Rio Grande do Sul and the deputy director of Brazil’s polar and climatic centre] said human influence – through the burning of fossil fuels – had also created “frightening” dynamics between the poles and the tropics. Cold wet fronts from the Antarctic had interacted with record heat and drought in the Amazon to create unprecedented storms in between. Floods in southern Brazil killed 51 people in early September and then returned with similarly devastating force in mid-November.
Aquino said this “record record” was a taste of what was to come as the world entered dangerous levels of warming. “From this year onwards, we will understand concretely what it means to flirt with 1.5C [of heating] in the global average temperature and new records for disasters,” he said.
This is already happening. This year’s deadliest climate disaster was the flood in Libya that killed more than 11,300 people in the coastal city of Derna. In a single day, Storm Daniel unleashed 200 times as much rain as usually falls on the city in the entire month of September. Human-induced climate change made this up to 50 times more likely.
Forest fires burned a record area in Canada and Europe, and killed about 100 people in Lahaina on Maui island, the deadliest wildfire in recent US history, which happened in August. For those who prefer to calculate catastrophe in economic terms, the US broke its annual record of billion-dollar disasters by August, by which time there had already been 23.
…
…as science has proved beyond any doubt, global temperatures would continue to rise as long as humanity continues to burn fossil fuels and forests.
In the years ahead, the heat “anomaly” and catastrophes of 2023 would first become the new norm, and then be looked back on as one of the cooler, more stable years in people’s lives. As Hansen warned, unless there is radical and rapid change, failure will be built into the climate system…
As we face facts, we might recall that it was on this date in 1870 that Congress authorized the formation of the U.S. weather service (later named the Weather Bureau; later still, the National Weather Service), and placed it under the direction of the Army Signal Corps. Cleveland Abbe, who had started the first private weather reporting and warning service (in Cincinnati) and had been issuing weather reports or bulletins since 1869, was the only person in the country at the time who was experienced in drawing weather maps from telegraphic reports and forecasting from them. He became the weather service’s inaugural chief scientist– effectively its founding head– in January, 1871. The first U.S. meteorologist, he is known as the “father of the U.S. Weather Bureau,” where he systemized observation, trained personnel, and established scientific methods. He went on to become one of the 33 founders of the National Geographic Society.
The Panama Canal has become a vital link in the web of global trade, especially that trade that connects Asia and the U.S. U.S. commodity export and import containers account for 73% of Panama Canal traffic, representing about $270 billion in cargo. That trade is now constrained, as water shortage has reduced the Canal’s throughput…
For months, the global shipping community has been closely watching the Panama Canal, as a severe drought has threatened water levels and forced the Panama Canal Authority to enact restrictions on the maximum weight and size of vessels that can transit its waters. The impact of the Panama Canal Authority’s restrictions has been negligible, as lower shipping demand offset any vessel weight restrictions–until now…
It takes almost 200 million gallons of water for every ship to transit the Panama Canal. And, in a drought, that’s become a problem. The Panama Canal operates with a lock system that is fed via freshwater drawn from Lake Gatun. The water flows from the lake, the high point of the canal, down through the lock system and is then discharged to sea. While the canal’s newer locks can recycle about 60% of its water, it still requires a tremendous amount of water for every ship to pass through.
At this time of year, the lake’s average water level should be around 87 feet, but the lake currently sits at 81.8 feet and is forecasted to remain at or near that level through January. To make matters worse, the lake is only receiving 70% of the intake it needs (largely from rain) to satisfy the canal’s water usage.
To combat this, about a year ago the Panama Canal Authority began limiting the draft of vessels (the distance between the waterline and the deepest point of the boat) that are using the canal. The current draft limit is 44 feet (from a normal 50 feet). A lot of factors influence the draft of a vessel but the number one factor which can be controlled most readily is the vessel’s weight. For every one foot of draft reduction, a container ship has to reduce its weight by the equivalent of 300-400 TEU (at 14 tonnes of cargo). Therefore a six-foot reduction in draft equates to 1800-2400 TEU of reduction in vessel capacity.
As the reduction in vessel draft proved to not be enough to manage Lake Gatun water levels, the Canal Authority began to limit the daily transits of vessels. The canal normally sees 34 planned transits per day. This has been reduced to 24 transits and is forecast to reduce to 18 by February 1, 2024…
Consequently, shipping companies are faced with a thorny choice: They can risk waiting for days, pay a big fee to jump the line (currently running at $4-4.5 million per passage), or avoid the canal entirely by taking a longer route… any of which increase the cost of transit– a cost that likely to show up in prices…
… Shipping companies are set to incur heavy losses due to the bottleneck. Maersk, which is the second-largest shipping company in the world, said it was working to ensure the backlog did not disrupt its deliveries. “We follow the guidance from the Panama Canal and adapt our intake on relevant services in advance of the departure at origin. Maersk remains committed to minimizing disruptions to our operations,” it said in a press release. The Danish company moves more than four million TEU (Twenty Foot Equivalent Unit) vessels every year. In 2021, it saw its revenues reach $62 billion. Maersk added that the low water levels in the Panama Canal were a stark reminder of the climate crisis, and its ripple effect on global supply chains.
There is still no estimate of how much the Panama Canal jam will cost shipping companies, but the situation is a reminder of the 2021 crisis in the Suez Canal in Egypt. In that case, shipping companies suffered multi-billion dollar losses when the Ever Given container ship got stuck and blocked access to the canal…
As we deal with drought, we might recall that it was on this date in 1982 that a soil sample taken in Times Beach, Missouri, was found to contain 300 times the safe level of dioxin (c.f. Agent Orange). A byproduct of the manufacture of hexachlorophene (banned in 1972) by NEPACCO (the North Eastern Pharmaceuticals and Chemicals Company), the dioxin was meant to be stored securely onsite, but was eventually improperly disposed of in a trench in the facility, and by a local waste handler.
Times Beach– well over 2,000 residents– was completely evacuated and relocated early in 1983. The land that was once Times Beach is now Route 66 State Park. One building from the town still exists: the park’s visitor center was once a roadhouse from Times Beach’s glory days and was the EPA’s headquarters for the area.
A sign warning buyers of the water situation is displayed across from a property for sale in Rio Verde Foothills, Arizona, on February 24, 2023
Between AD 1275 and 1300, the Anasazi, a civilization that had thrived in the canyonlands of the Four Corners area of the American Southwest for a thousand years, simply vanished, abandoning their urban centers, their irrigated lands, their sacred enclosures. Their descendants, the Hopi and Zuni, tell of a time of drought, the end of the rains. Without food in the desert, one can live for a fortnight; without water, perhaps a day. The collapse of the Anasazi occurred in a single generation.
The drought in the American Southwest has now entered its twenty-third year– and as Wade Davis explains in an excerpt from his book River Notes: Drought and the Twilight of the American West, the historic drought of the last couple of decades is threatening the Colorado River (on which 40 million Americans and 5.5 million acres of agriculture depend) and raising that specter again…
… We are today in the third decade of a drought that, despite heavy snowpacks in California and parts of the mountain west, remains unrelenting.
Over the last century, the river’s flow has averaged roughly 15 million acre-feet a year, far less than the 17.5 million acre-feet that planners anticipated when water rights were apportioned to the seven states of the basin — Wyoming, Colorado, Utah, New Mexico, Nevada, Arizona, and California — in 1922. In that year, the population of Arizona was roughly 350,000, that of Nevada a mere 80,000. Between 2000 and 2022, the flow of the river dropped to an average of 12 million acre-feet; over the last three years the annual flow has been but 10 million acre-feet. Even as the volume of water coming down the Colorado has dramatically declined, the seven states of the basin continue to clamor for allotments based on flawed assessments established nearly a century ago, exerting rights to consume what the river cannot provide.
As a result, during a drought of historic severity, water consumption has consistently surpassed the total natural flow of the river; altogether since 2000, water use has out-stripped supply by 33.6-million acre-feet (an acre-foot is 325,851 gallons). To meet demand, water has been diverted from the major reservoirs. Lake Mead, last full in 1983, is today down to 28 percent of capacity, 1,040 feet above sea level, the lowest it has been since the floodgates closed in the 1930s. If the reservoir drops below 950 feet, the Hoover Dam will no longer generate hydroelectric power. At 895 feet, the reservoir becomes a deadpool; water can no longer pass through the dam. The river downstream ceases to exist.
The situation at Lake Powell is equally grim. Its capacity is now down to 22 percent. In February 2023, the reservoir dropped to 3,522 feet above sea level, the lowest since the Glen Canyon Dam became operational in 1963. Should the water level drop another 32 feet, which can readily occur in a year, it will no longer be possible to generate electricity that today powers and cools the homes and businesses of 4.5 million citizens. A power outage in Phoenix, coinciding with a two-day heat wave, could result in half the population — 800,000 or more — seeking emergency care in hospitals set up to handle but 3,000 patients. An estimated 12,800 would die. At 3,370 feet, Lake Powell will reach deadpool. The Glen Canyon Dam will be but a concrete plug. Water will cease to flow, cutting off the drinking supply of well over 25 million Americans, including most of those living in Phoenix, Las Vegas, Tucson, and much of the Los Angeles basin.
…ordinary American families are already experiencing shortages that would have been unthinkable in 2006. For decades, the Arizona city of Scottsdale has provided the Rio Verde Foothills, a community of two thousand homes, with access to its municipal water supply, sourced from the Colorado. On January 1, 2023, this supply was cut, a decision made by a city facing its own crisis, leaving the people of Rio Verde no option but to buy water by the truckload at prices that tripled overnight. Those who dug wells discovered that, after years of drought, the water table had fallen by hundreds of feet. Residents have turned to using paper plates and urinating outside, even while coping with monthly water bills as costly as their mortgage payments.
Cities such as Las Vegas have implemented strict conservation measures, banning ornamental grass, limiting water deliveries to golf courses, reducing the size of swimming pools, using recycled water whenever possible. Yet despite these efforts, Las Vegas still uses twice as much water as the average US consumption. Hedging its bets, the city is building a three-mile-long tunnel that will come up at the bottom of Lake Mead, a $1.4-billion drain to ensure that if the reservoir ever runs dry, Las Vegas will get the last drop.
In the end, what Las Vegas and other cities do hardly matters, for the elephant in the room remains agriculture. Fully 80 percent of the water drawn from the Colorado goes to irrigating some 5.5 million acres, most of which is used to grow alfalfa and grass to feed cattle, and not only in the United States. Alfalfa grown in Arizona is exported by the ton to fatten cattle in Asia and the Middle East…
As we dowse, we might spare a thought for Bjørn Helland-Hansen; he died on this date in 1957. A pioneering oceanographer, his studies of the physical structure and dynamics of the oceans and their interactions with the atmosphere were instrumental in transforming oceanography from a science that was mainly descriptive to one based on the principles of physics and chemistry.
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