...If you remember your geologic timescales the divisions of time on earth run from "eons which split into eras, which break into periods, which divide into epochs and then all the way down to ages." That's from Inverse who note the powers that be decided to call the present age the Meghalayan referring to the drought-caused worldwide collapse of civilizations 4200 years ago rather than the much-championed Anthropocene (human influenced) age.and realized we haven't had a good megadrought post in a while.
Fortunately Physics Today (the membership mag of the American Institute of Physics) had a paper which their blog summarized on August 1.
Unraveling the mysteries of megadrought
First though our standard boilerplate on drought in the U.S.:
1) The Great American Desert was called that for a reason. The weather of the U.S. over the last 150 years is an anomaly in the longer history.
2) The subsidization of row crops, corn in particular, is a political decision that severely distorts investment and thus nutrition outcomes.
And from Physics Today, "Four ways we know pre-Columbian America was plagued by megadroughts":
In the August issue of Physics Today, climate scientists Toby Ault and Scott St. George share a pair of startling research findings. Between roughly 800 and 1500 CE, the American West suffered a succession of decades-long droughts, much longer than anything we’ve endured in modern history. And statistical models suggest that, as the climate warms, such megadroughts are increasingly likely to return.
How can scientists be so sure about the duration and extent of droughts that happened long before the era of instrument-based precipitation records? As Ault and St. George explain, the annual growth rings of ancient trees contain a rich paleoclimatic record of precipitation and soil moisture patterns. The width of a tree ring gives clues as to how well nourished the tree was in a given year. The map shows four western US megadroughts predicted from tree-ring data.
Ring-width analyses provide the most complete set of data on past moisture levels. But researchers have other ways of determining those conditions. Here are four of them:
Underwater tree stumps
Roughly the area of 35 000 football fields, Mono Lake, nestled in the eastern Sierra Nevada, is California’s fourth-largest inland body of water. Before 1940 it was even larger. That year, the city of Los Angeles began diverting water from the lake’s influent streams to provide municipal water. The receding shoreline of Mono Lake exposed two generations of low-lying tree stumps that had been hidden under the surface for centuries.
In 1994, California State University geographer Scott Stine used carbon dating to determine that the stump populations were the remains of trees that had died out around 1100 and 1350, respectively. A simple ring count suggested that at least some of the trees had lived for half a century before drowning under rising lake levels. Together, those pieces of information suggested that twice—once during the late 11th century and again during the early 13th century—Mono Lake dropped to exceptionally low levels for periods of 50 years or more. Stine’s study also yielded evidence of contemporaneous water-level drops in the Osgood Swamp and West Walker River, near Lake Tahoe, and in Lake Tenaya in Yosemite National Park. (S. Stine, Nature 369, 546, 1994.)Droughts which are common can become megadroughts which are not and when it happens it is a pretty big deal.
Archaeological artifacts
During protracted water shortages, societies often have no choice but to alter behavioral habits. During the California drought that lasted from 2011 to 2017, residents who watered their lawns, washed their cars with garden hoses, or committed other unnecessary water-related deeds risked being fined. But archaeological data suggest that those inconveniences pale in comparison with the disruptions suffered by pre-15th-century Native American cultures. Archaeologists can deduce those groups’ population shifts and migration patterns by carbon dating ceramic wares and other artifacts....MUCH MORE
So we try to stay attuned to the signs and have posted quite a bit on the downside of dry.
Previously:
Some of the papers that we've looked at over the years:
Temperature and Precipitation Patterns Associated with the 1950s Drought in the U.S. Southwest
AMO, PDO AND SEVERE DROUGHTS IN THE CONTERMINOUS US: A SOUTHWESTERN PERSPECTIVE
Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States
See also:
"U.S. Private Weather Agencies Predict WEAK El NiƱo in 2014"
Trading the California Drought: Almonds and Water
Projected Price Increases For Foods Affected By the California Drought
California Drought: Why Farmers Are 'Exporting Water' to China
El Nino Won't Come Quick Enough To Break the California Drought
U.S. Drought Monitor August 14, 2012 (and a look at megadroughts)
Ocean changes may trigger US megadrought
From our 2008 post "A Black Swan in Food":
...Donald Coxe, chief strategist of Harris Investment Management and one of my favorite analysts, spoke at my recent Strategic Investment Conference. He shared a statistic that has given me pause for concern as I watch food prices shoot up all over the world.Well we are now at 26 years of near perfect weather for row crops.
North America has experienced great weather for the last 18 consecutive years, which, combined with other improvements in agriculture, has resulted in abundant crops. According to Don, you have to go back 800 years to find a period of such favorable weather for so long a time.
Finally, from March 2015:
"The Economics of the California Water Shortage"
That little red blip at the far right side of the timeline is the current drought.
You could make a reasonable argument that for the last 150 years Californians have been living in a fool's paradise.