Transcript:

Celebrating three decades of Pulse of the Planet, here's a program from our archives.Scientists who predict global warming, point the finger of blame at the increased levels in our atmosphere of carbon dioxide, and other heat-trapping gases. To know what the future really holds in store, we would need to know the make-up of the Earth's atmosphere as it was in the past. Now, a new technique has made that possible. I'm Jim Metzner and this is the Pulse of the Planet.ambience: Ayalik Glacier We're listening to the sounds of a glacier. By actually drilling into glaciers and taking core samples, scientists are being given time capsules of the earth's atmosphere from thousands of years ago. George Woodwell is director of the Woods Hole Research Center."So it's possible to take a core of ice down through a glacier. We can determine from that core, the dates at which various layers in the glacier were laid down. And measuring the carbon dioxide content of gas bubbles in ice, we can thereby determine the amount of carbon dioxide in the air, at the time that the bubbles in the ice in those various layers were made. So we now have a record going back a hundred and sixty thousand years."Over most of the past few millennia, the composition of the atmosphere has not changed greatly. But over the past century, as a result of the spread of industrialization and the intensified use of forests and of fossil fuels, we've increased the Carbon Dioxide content of the atmosphere way above any level that it has reached in the past two hundred thousand years, and probably much longer. So we can expect the Earth to warm as a result. This archival program is part of our thirtieth anniversary celebration. Im Jim Metzner and this is the Pulse of the Planet.