Pre-historic Climate Change
This graph is based on ice cores drilled in Vostok, Antarctica. It shows temperature changes near the South Pole, which were more extreme than in the middle latitudes.
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| As recorded in ice cores from Vostok, Antarctica, the temperature near the South Pole has varied by more than 20 degrees Fahrenheit during the last 350,000 years. There have been peaks of warmth approximately every 100,000 years. The temperature and the carbon dioxide concentrations at the south pole parallel each other. The rise and fall of temperatures gives rise to the ice age/interglacial cycle. |
Ice Age/Interglacial Cycle
During the last Ice Age, approximately one-third of all land was covered by glaciers. Glaciers reached as far south as New York City. This huge volume of ice reduced the amount of water in the oceans, which lowered sea level by several hundred feet. As a result, a land bridge joined Siberia to Alaska, making travel between the two continents possible.
El Niño
El Niño is associated with the warming surface layer of the eastern Pacific near the equator. This two to six year cycle has existed for thousands of years. This variation affects the climate, habitats, and economies around the world from year to year.
For example, in the eastern equatorial Pacific, cooler, nutrient-rich water needed to support plankton and fish populations does not rise to the surface during El Niño events. The El Niño event of 1972-73 resulted in a collapse of the Peruvian anchovy fishery.
El Niño strongly affects the atmospheric circulation, leading to a global pattern of climate variations. For example, in 1997 record-breaking rainfall in Florida was likely caused by El Niño. In contrast, when the eastern Pacific water suddenly cooled in 1998, the Florida rainfall gave way to record-breaking drought. Periodic droughts in some regions create economic benefits elsewhere. Increased demand for Kenyan coffee, for example, has been linked to El Niño-related droughts in Brazil and Indonesia.
Younger Dryas – Abrupt Climate Change
Climate can exhibit abrupt shifts over large regions of the world. As the last glacial period was giving way to the current warm interglacial period, average temperatures in Greenland returned to glacial levels for more than 1,000 years. This unusual period, which is called the Younger Dryas, ended abruptly about 12,000 years ago. Evidence from an ice core drilled in Greenland indicates that temperatures there rose approximately 15°F (8°C) in less than a decade.
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