This past summer has proven to be the worst drought California has seen in our generation. Not only were water warnings strictly enforced, leading to neighbor turning on neighbors in the constant battle of lawn watering infractions, but some areas even had to have bottled water services deliver to their homes after running water was shut off in counties of the western state. But researchers don't think that this summer was a fluke, but rather a result of changing atmospheric climate... the same that led to the 1934 drought which was the driest of the millennia.
Recently accepted for publication by the journal Geophysical Research Letters, a journal of the American Geophysical Union, the research lead by NASA's Goddard Institute for Space Studies analyzed the relative intensity and devastation caused by droughts since 1000 AD and found that though the 2014 summer in California was particularly out of the ordinary even in the driest of areas, it did not quite compare to the drought of 1934.
"We noticed that 1934 really stuck out as not only the worst drought but far outside the normal range of what we see in the record" lead researcher Benjamin Cook says. "Dust storms may have dried things out further and kicked 1934 into a really extreme event."
The drought, which affected nearly 72 percent of the western United States, was a culmination of natural phenomena and human-related events in the form of dust storms caused by failed crop planning, researchers say. In fact, the rare and unforeseen drought was approximately seven times larger than droughts of comparable intensity from 1000AD to 2005, as reported by the NOAA records. And it was nearly 30 percent worse than the last record-breaking drought of 1580.
And researchers have found that the emergent conditions found in 1934 were near identical to what they're finding this year. High-pressure ridges lying over the Pacific Coast of the United States exacerbates normal drought conditions by deflecting storms holding much-needed rain water from the western states.
"When you have a high-pressure system there, it steers storms much farther north than they would normally be" Cook says. "With this high pressure sitting there in the winter of 1933 to 1934, it block a lot of the rainfall and storms that you would expect to come into California."
Using models to recreate the conditions of the 1934 drought, researchers were able to analyze the catastrophic events that took place and the preexisting conditions that may have led to the drought's severity, though the study did not find an answer to what causes these high-pressure ridges lying over the western states.
"There's some evidence that maybe it could be forced by changes in ocean temperatures in parts of the Pacific, but by all accounts, it appears to be just a natural mode of variability in the atmosphere" Cook says.
So while the current California drought may be the worst we will see this decade, it is by far not anywhere near as severe as that of 1934. And though similar conditions exist currently, which could potentially cause even worse widespread devastation across the western United States, the researchers assure the public that there are programs in place to hopefully predict and prevent a drought like that of 1934 ever again.
"Now we have the Natural Resources Conservation Service, which helps to limit wind erosion and dust storm erosion; they can reduce the chance of a 1934 event occurring again" Cook says. "[And while preventing these droughts may be a difficult task] it is such an important problem that society must be able to predict these major droughts."