Climate scientists reconsider the meaning and implications of drought in light of a changing world
UNIVERSITY OF CALIFORNIA – SANTA BARBARA
CREDIT: PUBLIC DOMAIN
Maps of the American West have featured ever darker shades of red over the past two decades. The colors illustrate the unprecedented drought blighting the region. In some areas, conditions have blown past severe and extreme drought into exceptional drought. But rather than add more superlatives to our descriptions, one group of scientists believes it’s time to reconsider the very definition of drought.
Researchers from half a dozen universities investigated what the future might hold in terms of rainfall and soil moisture, two measurements of drought. The team, led by UC Santa Barbara’s Samantha Stevenson, found that many regions of the world will enter permanent dry or wet conditions in the coming decades, under modern definitions. The findings, published in the Proceedings of the National Academy of Sciences, reveal the importance of rethinking how we classify these events as well as how we respond to them.
“Essentially, we need to stop thinking about returning to normal as a thing that is possible,” said Stevenson, an assistant professor in the Bren School of Environmental Science & Management. This idea affects both how we define drought and pluvial (abnormally wet) events and how we adapt to a changing environment.
A drought is when conditions are drier than expected. But this concept becomes vague when the baseline itself is in flux. Stevenson suggests that, for some applications, it’s more productive to frame drought relative to this changing background state, rather than a region’s historical range of water availability.
To predict future precipitation and soil moisture levels, Stevenson and her colleagues turned to a new collection of climate models from different research institutions. Researchers had run each model many times with slightly different initial conditions, in what scientists call an “ensemble.” Since the climate is an inherently chaotic system, researchers use ensembles to account for some of this unpredictability.
The results show a world where certain regions are in permanent drought while others experience perennial pluvial for the rest of the 21st century. The team calculated the year in which average soil moisture will exceed the threshold that defines either a megadrought or a megapluvial. “In other words, at what point do average conditions exceed what we would consider a megadrought if it happened now, [and never return to ‘normal’]” Stevenson said.
The western United States has already crossed this benchmark, and there are other places headed that way as well, including Australia, southern Africa and western Europe. “But, again, that’s if we use today’s definition of a drought,” Stevenson said.
The authors argue that we need to move away from fixed definitions toward a more nuanced account of drought and pluvial. “Our idea of normal is, in a sense, meaningless when ‘normal’ is continuously changing,” Stevenson added.
Climate models indicate that average soil moisture in many regions will continue to drop. That said, the team’s ensembles suggests that soil moisture will continue to experience drought-related variation similar to today, relative to the ever-drier baseline.
The fluctuation highlights the need to consider both long term changes and the usual ups and downs associated with historic droughts and pluvials. “The most important management challenge will be to adjust for the relentless declines in water availability, as this exceeds the expected impact of future megadroughts,” said co-author Julia Cole, a professor at the University of Michigan.
Precipitation patterns, on the other hand, will become much more extreme. Warm air holds more moisture than cold air. So as the atmosphere heats up, it’ll be able to suck more moisture from dry areas and dump more precipitation on wet regions.
“We wanted to consider both precipitation and soil moisture at the same time because that can be important for water management,” Stevenson said. For instance, we will need to adapt infrastructure to more arid conditions in the American West, but that infrastructure will also need to handle more intense rainfall.
“When we talk about being in a drought, the presumption is that eventually the drought will end, and conditions will return to normal,” Stevenson said. “But if we’re never returning to normal, then we need to adapt all of the ways that we manage water with the expectation that normal will continually be drier and drier every year.”
JOURNAL
Proceedings of the National Academy of Sciences
ARTICLE TITLE
Twenty-first century hydroclimate: A continually changing baseline, with more frequent extremes
ARTICLE PUBLICATION DATE
14-Mar-2022
Forgive me for working from memory instead of doing some research — but hasn’t the West and Southwest US experienced a centuries-long drought in the near past? Wasn’t it a 500-year drought?
If my recollection is correct, doesn’t that mean long droughts are normal for that region? The 500-year drought happened when there obviously was no possible human influence on the climate.
Somebody should model that.
It was called the ‘Desert Southwest” when I moved there 50 years ago.
How would you have any possible drought pictures without the Glen Canyon and Hoover Dams!
“In some areas, conditions have blown past severe and extreme drought into exceptional drought. But rather than add more superlatives to our descriptions, one group of scientists believes it’s time to reconsider the very definition of drought.”
They haven’t exhausted the addition of superlatives until they get to “ludicrous drought”.
“,,,,,,,,,,the unprecedented drought blighting the region.”
Right there is where I quit reading because we all know that the SW has had far longer and more severe droughts than anything we have seen in our lifetimes.
What they mean by unprecedented is they have never experienced anything like it since they were born and has they have no understanding of what happened before they were born it truly is unprecedented to them.
What do you expect from an “assistant professor in the Bren School of Environmental Science & Management.”
Somebody once said that if one has to add the suffix “Science” to a word, then it isn’t science.
Even before we start critiquing the wonders of new models there is a more basic question. What have these modelers done to earn our trust? Yeah, that was a rhetorical question because the answer is, “Nothing.”
From the article: ““Essentially, we need to stop thinking about returning to normal as a thing that is possible,” said Stevenson, an assistant professor in the Bren School of Environmental Science & Management.”
That’s one of the more ridiculous things I’ve heard an alarmist say lately.
Here’s a clue, Stevenson: We are living in normal times now. There’s no indication these normal times will change into abnormal times in the future.
You are assuming unprecedented warming in the future, which is why you are saying we can’t return to normal, but your assumptions have no basis in fact. You are wringing your hands over science fiction. You are living in a false reality. CO2 is not going to cause runaway warming.
What do you expect from a ‘Manager-In-Training?’
I recall 1977 in Utah where we were told by experts that the drought we were in was exceptional and it would take a decade for reservoirs to return to normal levels if only the weather would return to normal. They were releasing water from reservoirs threatened with overtopping by the spring of 1978. By the early 1980s water was being routed down some of the streets (North Temple I think) to reach the Jordan river. Rising levels in the Salt Lake were threatening the UP railroad causeway and the airport.
I have doubts that the climate models will tell us much of anything useful.
The “science” of prophecy rears its addled head yet again. Why is it that, among the infinite possible futures, the ecoloons only chose the worst case scenario for their fantasy predictions?
California has know much longer drought cycles.
Late in the 19th Century John Wesley Powell (2nd director of the USGS) warned the nation that the wet conditions in the SW that was drawing settlers by the droves was abnormal. He has been proven to be correct. We are still not building needed water infrastructure because of Leftist political posturing.
People up to their necks in water can read the same thing about Australia.
Here’s what NOAA’s Climate at a Glance shows for South West Precipitation:
Start on an unusual wet period and end on a naturally dry period and a -0.03 in./decade is the best they can do. Yep, droughts are increasing in the U.S. Southwest.
Always, there is too much ‘future’ guesswork. The rule should be… one wrong guess, and you are GONE. NO GUESSING.
There is no ‘normal’, and there never has been…everything fluctuates. Or maybe there is a normal after all, which is that there is no normal.
“Normal” is precisely what is so terrifying… normality and every aberation from it.
soil moisture changes are so large in some regions that conditions that would be considered a megadrought or pluvial event today are projected to become average.
Shivers!
Meanwhile… Current Colorado snow water snowpack equivalent is at 100% of … (you know… the “N” word)
aberration? abberashion?
I measure precipitation near the middle of section 102 on your map. I had 120% of normal last water year. Presently, I have 160% of Snow Water Equivalent on the ground compared to last year.
“The only thing that is constant is change.”
Thank you, Clyde, for the ultimate truth about both climate and nature.
the Sea of Cortez will flood all of Tucson in 123 years according to the latest study by the Homer Davis Elementary school board in MARCH OF 2022
This is great news! My descendants here in the Phoenix area will own beachfront!
It won’t be any great loss. Also, the illegals will then be coming through that sector by boat rather than on land.
The supposed permanent Texas drought of around 2011 was erased by everything filling up by the following wet years.
The supposed permanent CA drought of 2015 was erased by everything filling up with the following wet years.
Now we’re back to the drier cycle in CA and the hyperbole resurfaces.
This is sure sign of immense rain to soon fill everything up again.
Rain is forecast for California over the next few days.
It appears that she defines “permanent” differently than most do. With continental plates drifting laterally at 10X the rate of sea level rise, nothing is truly permanent on the surface of Earth. Mountain ranges can be leveled to a peneplain in about 50 million years, drastically changing the local climate during the process. Whether it is a careless use of a word, or another example of alarmists attempting to scare uncritical readers, it is inaccurate.
Models are only as good as the assumptions built into them, which usually go unexamined by the likes of Ms. Stevenson.
Nonsense, I agree. A trully quotable line: “it’ll be able to suck more moisture from dry areas and dump more precipitation on wet regions.” What does this even mean? Does she think deserts supply water to ‘wet regions’? Could it be that the oceans add the vast majority of moisture to the atmosphere?
Article edited by Peter Gleick.
Now all we need is a coherent definition of “normal,” a particularly unscientific term.
“Normal” would be the opposite of Nancy Pelosi
> “Maps of the American West have featured ever darker shades of red over the past two decades. The colors illustrate the unprecedented drought blighting the region. In some areas, conditions have blown past severe and extreme drought into exceptional drought.”
I have long complained about the drought labels. They are nothing but alarmist trigger words. Worse, the range tops out at 1 with no recognition of above normal water conditions.
D0 should not even be a thing. D1 is actually merely “Dry” but “Moderate Drought” is so much more headline grabbing reportable. D2 through D4 all need demotions.
This is an example of Exceptional Drought: https://skirose.com/the-mountain-web-cams/
I have a model that predicts you’re all going to die. All studies using this model have proven true to observations, therefore my model is correct.
If I were you, I’d mail your money to me right away to conduct more research, since you won’t be needing it eventually anyway.
I was born in Lodi, CA in 1969. By the time I was seven years old I knew what the word drought meant and I knew that California was in the midst of the worst drought in its history. Now, 45 years later, nothing has changed but this time it’s caused by man made CO2 emissions and they have climate models to prove it.
Perfect substitute for a post-Christian world…climate Change.
Another five minutes I won’t get back.
“The results show a world where certain regions are in permanent drought while others experience perennial pluvial for the rest of the 21st century.”
Mathematical question. Do the results of model runs like this come as a complete surprise (arriving at little or no rainfall or perennial rainforest conditions)? Is it possible to check the complex function of the model for its tendency toward being asymptotic like the hyperbolic function y=1/x. If so, then the model is itself an assumption.
I recall Willis E showing the CO2 theoretical forcing plus feedback equation for T being reducible to a linear equation and wondered if models are amenable to such analysis. Mathematics somewhat rusty at 84.