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News Release 09-166

The Arctic Offers More Evidence of Human Influences on Climate Change

Recent, sudden and dramatic Arctic warming was preceded by almost 2,000 years of natural cooling

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Photo of researchers taking a sediment core from a lake in Alaska.

Researchers (R.S. Anderson, A. Werner and T. Diagle) take a sediment core from the bottom of Goat Lake in south-central Alaska, which is 50 meters below the surface.

Credit: Darrell Kaufman, Northern Arizona University


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Darrell Kaufman summarizes study results.

Credit: National Science Foundation, Northern Arizona University

 

Darrell Kaufman explains Arctic sensitivity to climate change.

Credit: National Science Foundation, Northern Arizona University

 

Darrell Kaufman explains importance of lake evidence.

Credit: National Science Foundation, Northern Arizona University

 

Darrell Kaufman explains complexities of study.

Credit: National Science Foundation, Northern Arizona University

 

Darrell Kaufman discusses future studies.

Credit: National Science Foundation, Northern Arizona University

 

Illustration showing how a wobble in axis of rotation caused at least 1,900 years of cooling.

How a wobble in the Earth's axis of rotation caused a cooling trend that lasted at least 1,900 years.

Credit: Zina Deretsky, NSF


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Photo of tree cored in Alaska to retrieve its tree rings, which reflect historical temperatures.

Coring tree: A hemlock tree is bored by a researcher (T. Daigle) in south-central Alaska. The width of the annual rings of trees can be used to infer past changes in growing season temperatures.

Credit: Darrell Kaufman, Northern Arizona University.


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Photo of a sediment core from a lake in Alaska showing multiple layers of volcanic ash.

A new sediment core from Cub Lake in south-central Alaska shows multiple layers of volcanic ash. Sediment cores from lakes in volcanically active regions reveal information about past climate change as well as the eruptive histories of volcanoes.

Credit: Darrell Kaufman, Northern Arizona University


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Photo of sharp-crested ridges of glacial debris that descend into Upper Greyling lake in Alaska.

The previous extent of a glacier that feeds Upper Greyling Lake in south-central Alaska is marked by the sharp-crested ridges of debris (lateral moraines) that descend into the lake. Glacial history is combined with other evidence, such as lake-core evidence, to reconstruct climate history.

Credit: Darrell Kaufman, Northern Arizona University


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Cover of September 4 Science magazine.

The researchers' findings appear in the Sept. 4, 2009, issue of Science magazine.

Credit: Copyright 2009 AAAS


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