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Proxy Methods

Proxy measures are measurements of physical, chemical, or biological processes that depend on the weather, and therefore provide an indication of past climates.

Researcher works with a drill that extracts ice cores from glaciers during the 2003 Antarctic Megadunes expedition.

Ted Scambos & Rob Bauer, NSIDC



Glacial Extent

Ice Cores



Tree Rings

  • The Past Million Years Featured Article The Past Million Years The Past Million Years

    Climate researchers have reliable temperature records from weather stations dating back to about 1850. To study variations in climate that pre-date the advent of weather... More »

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The Past Million Years Last Updated on 2010-12-19 00:00:00 Climate researchers have reliable temperature records from weather stations dating back to about 1850. To study variations in climate that pre-date the advent of weather stations, climatologists rely on reconstructions based on a variety of proxy and direct measurements.   Reconstruction of global temperature changes based on 695 boreholes in the Northern Hemisphere. Blue-shaded area indicates the range of values for various reconstructions. After Pollack and Smerdon 2004.   The historical temperature record based on ice core proxy measures indicates that Earth’s climate during the past million years has been punctuated with about 8 cycles of relatively long, colder periods (glacials) interrupted by relatively short, warmer periods (interglacials). Each of nine interglacial periods correlates with higher concentrations of the greenhouse gases CH4,... More »
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