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If you cut a tree and examine the cross-section, you can tell how old the tree was by counting the rings. Scientists have been using a similar technique to learn how the earth’s climate has changed over the ages. But instead of looking at tree trunks, they’re examining ice. I’m Jim Metzner, and this is the Pulse of the Planet.
“Ice cores are sort of like looking at tree rings. Tree rings are annual bands and you can learn things about how trees grew over time. In ice cores, we look for annual layers as we go down in the core. The difference is that ice cores go back farther than tree ring records.”
Ed Brook of Washington State University is a geologist studying ice cores — cylinders drilled out of the sheets of ice covering Greenland and Antarctica. The ice cores are about eight inches in diameter and up to a mile and a half deep. Some of the ice is 400 thousand years old and it’s turning out to be a valuable historical record.
“The basic thing you learn from an ice core is what the climate was like in the past. When we can look at the thickness of annual layers in the ice, we can tell how much it snowed in the past, and that’s a really important indicator of climate, because precipitation rates are really tied in to the climate system. When we go back farther in time we learn a whole host of things about how climate varied naturally in the past and we’ve learned that there were lots of big natural variations, much bigger than humans have experienced or at least been around to record and write about.”
Ed Brook and other scientists are also finding different environmental clues in the ice cores, trapped inside air bubbles. We’ll hear more about these tiny time capsules in our next program.
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