Monday, October 20, 2014

Is California's drought worse than the Dust Bowl?

The atmospheric conditions that led to the so-called Dirty Thirties eight decades ago are present today, say researchers.

[CS Monitor] The catastrophic 1934 drought is one of the worst North America droughts on record, and was caused, in part, by an atmospheric condition that may have led to the current drought in California, a new study finds.
The 1934 drought affected about seven times more land area than other large droughts that hit North America between the years 1000 and 2005, and was almost 30 percent worse than the 1580 drought, the second most severe drought to hit the continent in the past 1,005 years.
"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 Ben Cook said in a statement. Cook is a climate scientist at NASA's Goddard Institute for Space Studies in New York City and holds a joint appointment at Columbia University's Lamont-Doherty Earth Observatory.
The same atmospheric phenomenon that emerged during the winter of 1933 to 1934 is also present today. This high-pressure ridge over the West Coast deflects storms holding much-needed rain, and may be causing the current drought crippling California, the researchers said.
"When you have a high-pressure system there, it steers storms much farther north than they would normally be," Cook told Live Science. "With this high pressure sitting there in the winter of 1933 to 1934, it blocked a lot of the rainfall and storms that you would expect to come into California."
It's unclear what causes the atmospheric ridge, however. "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 said.
This ridging pattern has been in place during some of the worst droughts to hit the West Coast, including the 1976 California drought, one of the worst dry spells in the state's history. California's current three-year drought is projected to cost the state $2.2 billion in 2014, and is predicted to continue in 2015, according to a July report from the University of California, Davis. Read More