All Things Considered host Linda Wertheimer talks with Dr. John Overpeck, the head of the National Oceanic and Atmospheric Administration's Paleoclimatology program at the National Geophysical Data Center. They discuss Overpeck's research, which uses "proxy measurements" to show that the planet is the hottest it has been in 600 years. Some of the things that Overpeck and his colleagues used to reach this conclusion are tree rings, ice cores, lake sediments, and historical documents.
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