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This year the Halloween Jack-o’-lanterns on Californian doorsteps are likely to be considerably smaller than usual. Like many other crops, pumpkins are suffering from California’s crippling three-year drought, which has cost the state $2.2 billion in 2014 alone. Now a new study shows that it may have been caused by the same atmospheric phenomenon that triggered the devastating decade-long “Dust Bowl” drought of the 1930s.
Starting in 1934, the dust bowl drought left nearly three-quarters of the western United States utterly parched and forced tens of thousands of families to abandon their farms. Using tree ring data, sea surface temperatures and rainfall records, Benjamin Cook from NASA’s Goddard Institute for Space Studies and colleagues have reconstructed the last one thousand years of North American droughts, and shown that the dust bowl drought really was exceptional. The findings, which are published in the journal Geophysical Research Letters, reveal that the dust bowl was around seven times larger than other major North American droughts in the last millennium, and nearly 30 per cent worse than the continent’s next most severe drought, which occurred in 1580.
But Cook and his colleagues also found that the trigger for the dust bowl – a high pressure ridge over the west coast during winter, which deflects rain-laden storms – is also responsible for the current Californian drought, and the 1976 drought (one of the most severe in the state’s history). However, the current drought is unlikely to turn into a repeat of the dust bowl, as better agricultural practices are helping to limit wind erosion and reducing the likelihood of dust storms.
