On past temperatures and anomalous late-20th-century warmth

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• Amman, Caspar
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• Bradley, Ray
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• Briffa, Keith
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• Jones, Philip
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• Osborn, Tim
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• Crowley, Tom
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• Hughes, Malcolm
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• Oppenheimer, Michael
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• Overpeck, Jonathan
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• Rutherford, Scott
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• Trenberth, Kevin
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• Wigley, Tom

Abstract

Evidence from paleoclimatic sources and modeling studies support AGU's official position statement on climate change and greenhouse gases; namely that there is a compelling basis for concern over future climate changes, including increases in global-mean surface temperatures, due to increased concentrations of greenhouse gases, primarily from fossil fuel burning.More specifically a number of reconstructions of large-scale temperature changes over the past millennium support the conclusion that late-20th century warmth was unprecedented over at least the past millennium. Modeling and statistical studies indicate that such anomalous warmth cannot be fully explained by natural factors, but instead, require a significant anthropogenic forcing of climate that emerged during the 19th and 20th centuries.