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AGU: Geophysical Research Letters

 

Keywords

  • global warming
  • instrumental bias
  • sampling errors

Index Terms

  • Global Change: Climate variability
  • Oceanography: Physical: Decadal ocean variability

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L01610, 5 PP., 2007
doi:10.1029/2006GL027834

How much is the ocean really warming?

Viktor Gouretski

Klimawissenschaften, Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven, Germany

Klaus Peter Koltermann

Intergovernmental Oceanographic Commission, UNESCO, Paris, France

We use a global hydrographic dataset to study the effect of instrument related biases on the estimates of long-term temperature changes in the global ocean since the 1950s. The largest discrepancies are found between the expendable bathythermographs (XBT) and bottle and CTD data, with XBT temperatures being positively biased by 0.2–0.4°C on average. Since the XBT data are the largest proportion of the dataset, this bias results in a significant World Ocean warming artefact when time periods before and after introduction of XBT are compared. Using bias-corrected XBT data we argue reduces the ocean heat content change since the 1950s by a factor of 0.62. Our estimate of the ocean heat content increase (0–3000 m) between 1957–66 and 1987–96 is 12.8·1022 J. Because of imperfect sampling this estimate has an uncertainty of at least 8·1022 J

Received 10 August 2006; accepted 20 November 2006; published 12 January 2007.

Citation: Gouretski, V., and K. P. Koltermann (2007), How much is the ocean really warming?, Geophys. Res. Lett., 34, L01610, doi:10.1029/2006GL027834.

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