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Our transcription: Another indicator of past climate is "stable oxygen isotopes," which are atomic variations of the element oxygen that do not decay. These isotopes are frozen within the ice itself at the time of its formation. The O-18/O-16 ratio of a snow sample or an ice sample in a core reflects the temperature at which the precipitation formed in a precipitating cloud above. This is preserved in the ice cores, and by measuring continuously the O-18/O-16 ratios using mass spectrometers, one determines summer and winter layers. By providing data about past temperatures, stable isotope analysis has helped answer a long standing question about the ice ages -- whether or not they occur simultaneously in both the Northern and Southern Hemispheres. I think the major contribution of stable isotope analyses in ice cores, if you look at it from a bipolar point of view, the Antarctic and the Greenland ice cores, the results from both records show us that approximately 10,700 years ago the ice age ended in both North and Southern Hemispheres. That wasn't too many years ago that climatologists and meteorologists were even sure that wind systems crossed the Equator.
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