A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate between glacial periods. The last glacial period ended about 15,000 years ago. The Holocene epoch is the current interglacial. A time with no glaciers on Earth is considered a greenhouseclimate state.
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Glacial and interglacial cycles as represented by atmospheric CO2, measured from ice core samples going back 800,000 years. The stage names are part of the North American and the European Alpine subdivisions. The correlation between both subdivisions is tentative.
Within the Quaternary (about 2.6 Ma to present), there have been a number of glacials and interglacials.
The Penultimate Glacial Period (PGP) is the glacial period that occurred before the Last Glacial Period. It began ~194,000 years ago, and ended 135,000 years ago with the beginning of the Eemian interglacial.
Since orbital variations are predictable, computer models that relate orbital variations to climate can predict future climate possibilities.
Work by Berger and Loutre suggests that the current warm climate may last another 50,000 years. The amount of heat trapping (greenhouse) gases being emitted into Earth's Oceans and atmosphere may delay the next glacial period by an additional 50,000 years.
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