These abrupt change are some to think about, but they take place over generational periods. They do not happen over night.
Guest essay by Dr. Don J. Easterbrook
Dept. of Geology, Western Washington University, Bellingham, WA
The results of oxygen isotope measurements from ice cores in the Greenland and Antarctic ice sheets several decades ago stunned the scientific world. Among the surprises from the cores was the recognition of multiple, late Pleistocene, extraordinarily abrupt, intense periods of warming and cooling. The most precise records of late Pleistocene climate changes are the ice cores of the Greenland Ice Sheet Project (GISP) and the Greenland Ice Core Project (GRIP). These cores are especially important because the ages of the ice at various levels in the core have been measured by counting annual layers in the ice, giving a very accurate chronology of climatic fluctuations determined by measurement of annual layers.
Figure 1. Oxygen isotope fluctuations in the GISP2 Greenland ice core. Red = warm periods, blue = cold periods. Up on the vertical…
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