Science and Implementation Plan: Chapter 2

Rapid Climate Change

The ice of polar ice sheets contains within it an incomparable record of past climate changes. Recent results from analysis of the Greenland Ice Sheet Project II (GISP2) ice core in central Greenland show that the climate of the most recent 8000 years has been anomalously stable and friendly to humans compared to the previous 100,000 years, when exceptionally large climate changes occurred in as little as 1 to 3 years. These climate changes were more profound than any in recorded human history, vastly exceeding, for example, the Little Ice Age, which peaked in the mid-1700s and caused extensive abandonment of farms in northwestern Europe as well as severe problems for humanity elsewhere around the world. Understanding such changes and assessing the possibility that they could recur are obviously of human interest. We do not yet know to what extent they were global or local events, and whether they started in the North Atlantic or elsewhere.

A similar ice core from the Southern Hemisphere is urgently needed to determine whether these rapid changes extended globally. Existing Antarctic cores with long records were drilled in regions where snow accumulation is too slow to record abrupt climate changes. The only area for a core capable of providing a long annual-resolution history of Southern Hemisphere climate lies in the interior of West Antarctica, where compressed snow layers are thick enough to allow absolute dating of annual signals. The ability to resolve annual layers in these cores enables scientists, for the first time, to identify the precursory climatic parameters and the response-time-scales of other parameters. Fine time resolution of various key climatic parameters, such as carbon dioxide, oxygen and hydrogen isotope ratios, will permit the separation of causes from effects. Reliable absolute dating will permit comparisons of records from Greenland and West Antarctica and indicate which parameters were changing globally and how fast they were changing. This information will be critical in directing scientists toward the mechanisms responsible for rapid climate change and is a crucial step in the development of a predictive capability to anticipate future climates and to mitigate undesirable consequences of those changes.