Evidence: Ice Cores
Long cores through the ice cap on Greenland, like a short section modeled in the exhibition, tell us a lot about the climate of the Northern Hemisphere over the past 110,000 years. For instance, we know from Greenland ice that until fairly recently, the region swung abruptly between warm and cold periods. But for the last 11,600 years, since around the time of the earliest human civilizations, air temperatures remained far more stable.
Today, however, Earth's temperature is rising rapidly. Scientists studying tree rings and sediments from lake and ocean bottoms, among other kinds of evidence, now know that Earth is hotter today than at any time in the last 400 years and probably in the last 1,000 years. The rate of warming has increased dramatically over the past 30 years.