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Letters to Nature

Nature 403, 756-758 (17 February 2000) | doi:10.1038/35001556; Received 7 June 1999; Accepted 8 December 1999

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Temperature trends over the past five centuries reconstructed from borehole temperatures

Shaopeng Huang1, Henry N. Pollack1 & Po-Yu Shen2

  1. Department of Geological Sciences, The University of Michigan, Ann Arbor, Michigan 48109-1063, USA
  2. Department of Earth Sciences, The University of Western Ontario, London, Ontario, N6A 5B7, Canada

Correspondence to: Henry N. Pollack1 Correspondence and request for materials should be addressed to H.N.P. (e-mail: Email: hpollack@umich.edu).

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For an accurate assessment of the relative roles of natural variability and anthropogenic influence in the Earth's climate, reconstructions of past temperatures from the pre-industrial as well as the industrial period are essential. But instrumental records are typically available for no more than the past 150 years. Therefore reconstructions of pre-industrial climate rely principally on traditional climate proxy records1, 2, 3, 4, 5, each with particular strengths and limitations in representing climatic variability. Subsurface temperatures comprise an independent archive of past surface temperature changes that is complementary to both the instrumental record and the climate proxies. Here we use present-day temperatures in 616 boreholes from all continents except Antarctica to reconstruct century-long trends in temperatures over the past 500 years at global, hemispheric and continental scales. The results confirm the unusual warming of the twentieth century revealed by the instrumental record6, but suggest that the cumulative change over the past five centuries amounts to about 1 K, exceeding recent estimates from conventional climate proxies2, 3, 4, 5. The strength of temperature reconstructions from boreholes lies in the detection of long-term trends, complementary to conventional climate proxies, but to obtain a complete picture of past warming, the differences between the approaches need to be investigated in detail.

  1. Department of Geological Sciences, The University of Michigan, Ann Arbor, Michigan 48109-1063, USA
  2. Department of Earth Sciences, The University of Western Ontario, London, Ontario, N6A 5B7, Canada

Correspondence to: Henry N. Pollack1 Correspondence and request for materials should be addressed to H.N.P. (e-mail: Email: hpollack@umich.edu).