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

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


Abstract

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.

Keywords: global warming; instrumental bias; sampling errors.

Index Terms: 1616 Global Change: Climate variability (1635, 3305, 3309, 4215, 4513); 4513 Oceanography: Physical: Decadal ocean variability (1616, 1635, 3305, 4215).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 420733 bytes)

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