Image: Graph of "Temperature in central Greenland"
Caption: This figure shows the history of air temperature in central Greenland over the last 100,000 years. The air temperatures were derived from oxygen isotopic measurements on the accumulation of precipitation (i.e., snow and ice) in Greenland ice cores. The figure should be read from the right to the left to follow the logical sequence of time from older events to younger events nearer to modern times.
By examining the layers of snow and ice in Greenland ice cores, and the gases trapped within, scientists can analyze thousands of years of Earth’s climate. Only now are we beginning to realize how quickly climate can change.
For example, an extremely rapid change in climate occurred during a period of time known as the Younger Dryas (YD); a cold climatic event occurring about 13,000 years ago. The Younger Dryas lasted approximately 1,200 years and was a nearly global cooling event that occurred in the midst of a warming trend following the end of the last Ice Age.
What we didn't know until recently was just how quickly the Younger Dryas began and ended. In a period of less than 50 years, the climate of the eastern US, Canada, and much of Europe went from one much like today's world to a much colder climate typical of the Ice Age. The Earth's climate remained cold for about 1,000 years and then abruptly flipped, in as little as 20 years, to warmer conditions.
Data from other paleoclimate archives on land and in the sea show other such abrupt changes in climatic conditions occurring over time periods of 5-50 years.
Research by academic scientists supported by the NSF is currently aimed at identifying and understanding other abrupt climatic events in the geologic record closer in age to modern times.
The bottom line is that the record of Earth's climate shows shifts in climate over very short periods of time that impact eco- and human systems. The Earth has a rich history of natural climate variability (and associated climate impacts) that is useful as a baseline for understanding how our climate operates and how it is changing. Data such as this allows us to collect critical baseline data on Earth’s climate system that will help us understand the range of natural climate variability. Betting on future climates without such baseline data is like investing in a company’s stock without assessing its past performance. It doesn't seem prudent.
Source: The figure is from the 2002 National Academy of Sciences report entitled, "Abrupt Climate Change: Inevitable Surprises" by Richard B. Alley and colleagues.
NSF Funded: yes
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