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Getting evidence of long-term temperature changes is hard work. Weather stations change location over the decades, and readings from once-rural recording stations are affected by the shade-throwing buildings or heat-trapping tarmac roads built around them.
Getting evidence of long-term temperature changes is hard work. Weather stations change location over the decades, and readings from once-rural recording stations are affected by the shade-throwing buildings or heat-trapping tarmac roads built around them. Sometimes even the best records are simply lost over time.
So it is with some excitement that climate scientists have come across 114 years' worth of continuous temperature records from a nature preserve 90 miles north of New York City. The recordings of temperature and rainfall, taken at the same rural spot by members of the same family and their friends over more than a century, are a rare chance to look at how temperatures have changed in a place that itself has not.
What do they show? The average annual temperature at the Mohonk Preserve has gone up 2.63 degrees Farenheit (1.46 degrees Celsius) between 1896 and 2006, and the rate of increase has been rising significantly in recent decades, according to a new report by the nature preserve and Columbia University's Lamont-Doherty Earth Observatory , published in the latest edition of the Journal of Applied Meteorology and Climatology.
The temperature increases are particularly clear in the summer. Before 1980, temperatures rarely passed 89 degrees Farenheit (31.6 degrees Celsius) more than 10 days a year. Since then, temperatures have often hit that level more than 20 days a year.
In the winter, the preserve has seen one less day with temperatures below freezing every five years. Since the 1970s, the loss of freezing days has been one every two years.
That amounts to "a powerful confirmation of global warming," according to Columbia University officials.
"It is incredibly rare to have the level of continuity that we have at Mohonk," said Benjamin Cook, a climate modeler at the Columbia University earth observatory. "Any one record cannot tell you anything definitively about climate globally or even regionally. But looking closely at sites like this can boost our confidence in the general trends that we see elsewhere, and in other records."
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