Freeze and Thaw
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What do riverboat captains, 15th century Japanese priests, Swiss churches, and fur trappers have in common? Give up? They all kept records that further confirm global warming. Hi I'm Dave Thurlow and this is the Weather Notebook.

If you think it's been getting warmer in the past 100 years or so, you're not the only one. A group of scientists, led by John Magnuson from the University of Wisconsin, recently tracked the freeze-and-thaw histories of 39 lakes and rivers in nine countries where records go back hundreds of years. The results of the study are in the September issue of Science magazine. The study drew on sources as diverse as newspaper archives, Canadian fur trader records and religious observations.

One of the oldest sources was Lake Constance between Switzerland and Germany, where freeze-thaw records from churches on both sides of the lake date back to the ninth century. Of the 39 bodies of water studied, only one ran contrary to the trend: Lake Suwa in Japan. The lake records kept by Shinto priests - date to 1443. But at the other 38 sites, the study found that over 150 years, ice was freezing more than 8 days later and thawing 9 days earlier.

The strength of this data, Magnuson says, is not what it says about the greenhouse effect, but the almost undeniable evidence that it's been getting warmer for 150 years. In fact, this data corresponds to a 3.2 degree Fahrenheit warming since the start of the industrial revolution, twice what has been generally accepted.

This is yet another example of evidence that points right at a rapidly warming planet. The Weather Notebook is a production of the Mount Washington Observatory.