As a metaphor for the uncomfortable truths this drought has laid bare, the body in the barrel is grimly apt.
Sometime in the mid-1970s or 1980s, someone dumped a metal boat containing the remains of a male gunshot victim into Lake Mead. At that point, the barrel sank through hundreds of feet of cold Colorado River water before settling to the muddy bottom of the nation’s largest man-made reservoir.
Now the lake is emptier than ever, and the consequences of those actions decades ago are no longer hidden. The water level has plummeted, leaving ghostly calcium deposits along the rocky shores of the lake. On Sunday, police say, boaters spotted the rusted remains of the barrel and its occupant in a sun-scorched stretch of exposed mud.
Homicide victims were not what scientists at the Intergovernmental Panel on Climate Change had in mind in 2001 when they warned of “imaginable surprises” that an altered climate could produce. But the historic mega-drought that has drained Lake Mead of its water and secrets meets its definition: a surprising and unpredictable event that nonetheless falls within the realm of disturbing new possibilities for a warmer world.
This drought, the worst on record, is the result of many factors, some of which are coincidences of nature and others, the result of human activity.
Average summer temperatures in California are 3 degrees higher now than they were in the late 19th century. Less snow falls, which means the volume of water feeding streams and reservoirs is 15-30% less than it was in the mid-20th century.
There have been stretches of dry years in this part of the world since the climatological records. But global warming has escalated the current dry spell into disaster territory.
Humans aren’t the only ones who need more water. Parched vegetation and soil must now also compete with a thirstier sky, thanks to atmospheric changes brought on by decades of steadily rising temperatures.
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A warmer atmosphere holds more water, and the warmer it gets, the more water it needs, regardless of the need on the ground. In a study published last month in the Journal of Hydrometeorology, researchers analyzing 40 years of data found that the atmosphere in the continental US now demands a higher proportion of water than before, especially in the West.
The effect is not linear: as the planet warms, the sky becomes even thirstier.
“As the climate warms, that pull of water from the Earth’s surface into the atmosphere becomes essentially more forceful,” said study leader Christine Albano, a hydrologist at the Desert Research Institute in Reno.
That increasing force means that more water is needed today than it was 40 years ago to provide plants with the same level of hydration. The Rio Grande region that covers parts of Colorado, New Mexico and Texas now needs 8% to 15% more water to get the same irrigation output, the researchers calculated. The effect is a little smaller in California but it’s still there, Albano said.
More than half of this increased thirst was due to rising temperatures, the authors found. Other factors included changes in humidity (26%), wind speed (10%), and solar radiation (8%).
Unlike earthquakes and hurricanes, the onset of a drought cannot be fixed in a day or an hour. “It’s one of these creeping disasters,” said John Abatzoglou, a UC Merced climatologist who worked on the study with Albano.
Drought manifests itself in several different ways that don’t always occur at the same time: decreased rainfall, low groundwater and stream levels, thirsty crops, insufficient community supplies, or distressed ecosystems.
“When it starts to feel really bad is when all those types of drought are essentially happening at the same time. And that’s where we are now,” said Faith Kearns, a scientist at the California Water Resources Institute in Oakland.
It didn’t get this way all at once. The western United States is in the hottest and driest 23-year period in at least the last 1,200 years, said Park Williams, a climate scientist at UCLA.
Thanks to a combination of higher temperatures and insufficient rainfall, the soils of southwestern North America were drier between 2000 and 2021 than in any other 22-year period since the 19th century, surpassing a similarly arid period in the late 16th century. , Williams and colleagues. reported in a study published this year in Nature Climate Change.
Williams has updated the data to include the current year through March. Even if we get an average amount of rainfall over the summer, 2022 will join 2002 and 2021 as the three driest years in the last century, and most likely the driest since the 18th century, she added.
“We’ve had three of these ‘driest in the last 300 years’ years in the last two decades,” he said.
In their study, Williams and colleagues determined that rising temperatures were the single largest factor in the current megadrought, accounting for 42% of the overall responsibility. “The usual bad luck” reduced rain and cloud cover, he said. But without climate change, the natural fluctuations of the past few decades would not have qualified as a megadrought, the authors wrote.
Furthermore, the most comparable megadrought in the historical record, that late-16th-century event, began to fade as it entered its third decade.
That’s not happening this time.
“This drought that we’re in now, instead of showing any signs of going away, it doubled last year and then doubled again this year,” Williams said. “This drought is being harder now than ever.” Temperatures remain high. The rain is not falling yet. There are no signs that relief is coming soon.
Recovering from this drought will take more than a single wet winter. Given dry conditions on land and increased demand on the atmosphere, we will likely need several seasons of heavy rainfall to make up for the current water deficit, Albano said.
California gets up to 50% of its annual precipitation from atmospheric rivers that redistribute water vapor from the tropics to the poles. These rivers are expected to become more erratic as the climate changes, with fewer storms that are much more intense and destructive. Global warming is also disrupting the El Niño cycle, again concentrating rainfall into fewer, more aggressive storms.
Predicting exactly when those things will happen is just as impossible as knowing when the next earthquake will strike.
There are likely to be years wetter than this at some point, climate scientists say, but that doesn’t change the underlying trend toward higher temperatures and drier soils.
“Whatever was normal, it’s not like there’s a lot of normal, it’s certainly changing,” Abatzoglou said. “How do we prepare for this is becoming a really challenging question for all walks of life that depend on water, which is the whole world.”
Just as there has been a fundamental change in average temperature, the public may need to fundamentally reshape their expectations of water availability.
This drought is unprecedented in modern times, but neither is it unforeseen. In that IPCC report from two decades ago, the authors predicted that if we did nothing to stop climate change, we would see exactly the kind of conditions the West is experiencing now: higher average daily temperatures, more heat waves, longer and more frequent. droughts, worse water quality and more forest fires.
Meanwhile, Las Vegas police say they expect to find more bodies as Lake Mead continues to recede. Many facts that people would rather not face are coming to the surface.