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1 .This is Scientific American 60-Second Science. I'm Christopher Intagliata. Got a minute?
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2 .It's been a light year for tornadoes in the U.S., just a few dozen so far.
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3 .By this time in 2011, a notoriously deadly tornado year, there had already been more than 120 twisters.
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4 .So why the variability?
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5 .Well, for decades, scientists have hypothesized that tornado frequency may be related to the fluctuation of sea surface temperatures in the equatorial Pacific, known as El Ni?o and La Ni?a.
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6 .But the link wasn't clear in the peak springtime tornado season.
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7 .Because observations of tornadoes and hail tend to be most prevalent where people can see them, meaning the data isn't that comprehensive.
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8 .So researchers took a step back, looking instead at the basic ingredients of tornadoes and hail: factors like wind shear, humidity and temperature.
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9 .During La Ni?a, they indeed saw a boost in the conditions that breed springtime twisters and hail in the southeastern U.S.In El Ni?o years, they saw the opposite.
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10 .The findings appear in the journal Nature Geoscience.
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11 .Study author John Allen, a climatologist at the Earth Institute at Columbia University, says the data might be used to create yearly tornado forecasts, like this one:
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12 ."So the forecast for this spring is a 60 percent chance of being around about normal, because we've got a relatively weak El Nino pattern, which tends to suppress a little bit.
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13 .So we'd probably say that it's going to be at or below normal."
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14 .Insurance companies or governments could use that data to gauge risk, he says！but no forecast can guarantee safety.
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15 ."One tornado will still wreck a house.
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16 .It will still end somebody's life, or destroy their life.
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17 .And this is the thing to remember.
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18 .We're saying there's a lower chance, but even in a quiet year we're still seeing about 800 tornadoes in the United States.
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19 .And you know, if the right conditions match up, a tornado can form anywhere on this planet."
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20 .Thanks for the minute, for Scientific American's 60-Second Science. I'm Christopher Intagliata.
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