Scientists got the first unequivocal evidence of a continuing moderate natural climate cycle in the 1980s, when Willi Dansgaard of Denmark and Hans Oeschger of Switzerland first saw two mile-long ice cores from Greenland representing 250,000 years of Earth's frozen, layered climate history. From their initial examination, Dansgaard and Oeschger estimated the smaller temperature cycles at 2,550 years. Subsequent research shortened the estimated length of the cycles to 1,500 years (plus or minus 500 years).

According to the authors:

* An ice core from the Antarctic's Vostok Glacier -- at the other end of the world from Greenland - showed the same 1,500-year cycle through its 400,000-year length.

* The ice-core findings correlated with known glacier advances and retreats in northern Europe.

* Independent data in a seabed sediment core from the Atlantic Ocean west of Ireland, reported in 1997, showed nine of the 1,500-year cycles in the last 12,000 years.

Considered collectively, there is clear and convincing evidence of a 1,500-year climate cycle. And if the current warming trend is part of an entirely natural cycle, as Singer and Avery conclude, then actions to prevent further warming would be futile, could impose substantial costs upon the global economy and lessen the ability of the world's peoples to adapt to the impacts of climate change.

Source: S. Fred Singer and Dennis T. Avery, "The Physical Evidence of Earth's Unstoppable 1,500-Year Climate Cycle," National Center for Policy Analysis, Policy Report No. 279, September 29, 2005

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