Stalagmites Provide Clues in Changing Rainfall Patterns

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• JIM LEHRER:

  And finally tonight, searching for clues about changes in weather patterns. Tom Clarke of Independent Television News reports from a remote region in southwest Poland.

• TOM CLARKE:

  Deep in a cave, squeezing between rocks and freezing mud isn't exactly where you'd expect to find climate scientists, but you can't attempt to travel back in time to recreate the history of Europe's weather without going to extremes. And trying to film their research is no simple task, either.

  It's definitely quite the squeeze, isn't it?

  Husband and wife team Lisa and James Baldini are paleoclimatologists at Durham University. They're using cave stalagmites to unravel the history of a climate pattern called the North Atlantic Oscillation.

  As the name suggests, it's a weather phenomenon that swings back and forward, like the Pacific's El Nino, only for Europe.

  DR. LISA BALDINI, paleoclimatologist, Durham University: It's got a major impact on European climate. And it's important to know how this has changed in the past.

• TOM CLARKE:

  The NAO's past can inform today's forecasters, who know how crucial the weather pattern is.

• DR. ADAM SCAIFE, Met Office, Hadley Center:

  It's the most important single factor, actually, that determines the year-to-year changes in the weather. When the NAO is positive, in its strong phase, then we have strong westerly winds across the Atlantic. These bring mild wet air off the Atlantic into the U.K. That creates more rainfall, and so we get more flooding during those winters.

  During winters when the NAO is negative, then the winds are much weaker and often the air actually comes from the east. And that can bring cold Siberian air into the U.K. and Northern Europe, and that gives us cold, dry conditions.