Letter | Published:

Robust warming of the global upper ocean

Nature volume 465, pages 334337 (20 May 2010) | Download Citation


A large (1023 J) multi-decadal globally averaged warming signal in the upper 300 m of the world’s oceans was reported roughly a decade ago1 and is attributed to warming associated with anthropogenic greenhouse gases2,3. The majority of the Earth’s total energy uptake during recent decades has occurred in the upper ocean3, but the underlying uncertainties in ocean warming are unclear, limiting our ability to assess closure of sea-level budgets4,5,6,7, the global radiation imbalance8 and climate models5. For example, several teams have recently produced different multi-year estimates of the annually averaged global integral of upper-ocean heat content anomalies (hereafter OHCA curves) or, equivalently, the thermosteric sea-level rise5,9,10,11,12,13,14,15,16. Patterns of interannual variability, in particular, differ among methods. Here we examine several sources of uncertainty that contribute to differences among OHCA curves from 1993 to 2008, focusing on the difficulties of correcting biases in expendable bathythermograph (XBT) data. XBT data constitute the majority of the in situ measurements of upper-ocean heat content from 1967 to 2002, and we find that the uncertainty due to choice of XBT bias correction dominates among-method variability in OHCA curves during our 1993–2008 study period. Accounting for multiple sources of uncertainty, a composite of several OHCA curves using different XBT bias corrections still yields a statistically significant linear warming trend for 1993–2008 of 0.64 W m-2 (calculated for the Earth’s entire surface area), with a 90-per-cent confidence interval of 0.53–0.75 W m-2.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    , , & Warming of the world ocean. Science 287, 2225–2229 (2000)

  2. 2.

    et al. Penetration of human-induced warming into the world’s oceans. Science 309, 284–287 (2005)

  3. 3.

    et al. Anthropogenic warming of Earth’s climate system. Science 292, 267–270 (2001)

  4. 4.

    , & Assessing the globally averaged sea level budget on seasonal to interannual timescales. J. Geophys. Res. 113, C06015 (2008)

  5. 5.

    et al. Improved estimates of upper-ocean warming and multi-decadal sea-level rise. Nature 453, 1090–1093 (2008)

  6. 6.

    et al. Sea level budget over 2003–2008: a reevaluation from GRACE space gravimetry, satellite altimetry and Argo. Global Planet. Change 65, 83–88 (2009)

  7. 7.

    & Closing the sea level rise budget with altimetry, Argo, and GRACE. Geophys. Res. Lett. 36, L04608 (2009)

  8. 8.

    et al. An observationally based energy balance for the Earth since 1950. J. Geophys. Res. 114, D17107 (2009)

  9. 9.

    & Revaluation of historical ocean heat content variations with time-varying XBT and MBT depth bias corrections. J. Oceanogr. 65, 287–299 (2009)

  10. 10.

    et al. Global ocean heat content 1955–2007 in light of recently revealed instrumentation problems. Geophys. Res. Lett. 36, L07608 (2009)

  11. 11.

    & Estimating annual global upper-ocean heat content anomalies despite irregular in situ ocean sampling. J. Clim. 21, 5629–5641 (2008)

  12. 12.

    , , & Isolating the signal of ocean global warming. Geophys. Res. Lett. 34, L23610 (2007)

  13. 13.

    & An objective ocean temperature and salinity analysis using covariances from a global climate model. J. Geophys. Res. 112, C02022 (2007)

  14. 14.

    , & Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global scales. J. Geophys. Res. 109, C12036 (2004)

  15. 15.

    & On depth and temperature biases in bathythermograph data: development of a new correction scheme based on the analysis of a global ocean database. Deep-Sea Res. I 10.1016/j.dsr.2010.03.011 (in the press)

  16. 16.

    et al. in Proc. OceanObs’09: Sustained Ocean Observations Inf. Soc. Vol. 2 (eds Hall, J., Harrison D. E. & Stammer, D.) (European Space Agency, 2010)

  17. 17.

    et al. Global oceans: do global temperature trends over the last decade falsify climate predictions? Bull. Am. Meteorol. Soc. 90, S56–S57 (2009)

  18. 18.

    An imperative for climate change planning: tracking Earth's global energy. Curr. Opin. Environ. Sustainability 1, 19–27 (2009)

  19. 19.

    et al. in Proc. OceanObs’09: Sustained Ocean Observations Inf. Soc. Vol. 1 (eds Hall, J., Harrison D. E. & Stammer, D.) (European Space Agency, 2010)

  20. 20.

    et al. Argo: the challenge of continuing 10 years of progress. Oceanography 22, 46–55 (2009)

  21. 21.

    & How much is the ocean really warming? Geophys. Res. Lett. 34, L01610 (2007)

  22. 22.

    et al. Changing expendable bathythermograph fall rates and their impact on estimates of thermosteric sea level rise. J. Clim. 21, 5657–5672 (2008)

  23. 23.

    , & Factors affecting the quality of XBT data – results of analyses on profiles from the Western Mediterranean Sea. Ocean Sci. 3, 59–75 (2007)

  24. 24.

    et al. World Ocean Database 2005 (ed. Levitus, S.) Ch. 1 (US Government Printing Office, 2006)

  25. 25.

    & Quality control of ocean temperature and salinity profiles – historical and real-time data. J. Mar. Syst. 65, 158–175 (2007)

  26. 26.

    Warming of the Southern Ocean since the 1950s. Science 295, 1275–1277 (2002)

  27. 27.

    & Recent western South Atlantic bottom water warming. Geophys. Res. Lett. 33, L14614 (2006)

  28. 28.

    , & Warming and freshening in the abyssal southeastern Indian Ocean. J. Clim. 21, 5351–5363 (2008)

  29. 29.

    , , & Recent bottom water warming in the Pacific Ocean. J. Clim. 20, 5365–5375 (2007)

  30. 30.

    et al. Simulated and observed variability in ocean temperature and heat content. Proc. Natl Acad. Sci. USA 104, 10768–10773 (2007)

Download references


J.M.L. and G.C.J. were funded by the US National Oceanic and Atmospheric Administration (NOAA) Climate Program Office and NOAA Research. S.A.G., M.D.P. and D.M.S. were supported by the Joint DECC and Defra Integrated Climate Programme DECC/Defra (GA01101). C. Domingues, S. Levitus, T. Boyer, M. Ferrante and D. Trossman provided comments. C. Domingues, S. Levitus, and T. Boyer also provided corrected XBT profiles. This is Pacific Marine Environment Laboratory contribution number 3476 and Joint Institute for Marine and Atmospheric Research contribution number 09-372.

Author information


  1. Joint Institute for Marine and Atmospheric Research, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA

    • John M. Lyman
  2. NOAA/Pacific Marine Environmental Laboratory, Seattle, Washington 98115-6349, USA

    • John M. Lyman
    •  & Gregory C. Johnson
  3. Met Office Hadley Centre, Exeter EX1 3PB, UK

    • Simon A. Good
    • , Matthew D. Palmer
    •  & Doug M. Smith
  4. KlimaCampus, University of Hamburg, Grindelberg 5, 20144 Hamburg, Germany

    • Viktor V. Gouretski
  5. Climate Research Department, Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki 305-0052, Japan

    • Masayoshi Ishii
  6. Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama 236-0001, Japan

    • Masayoshi Ishii
  7. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA

    • Josh K. Willis


  1. Search for John M. Lyman in:

  2. Search for Simon A. Good in:

  3. Search for Viktor V. Gouretski in:

  4. Search for Masayoshi Ishii in:

  5. Search for Gregory C. Johnson in:

  6. Search for Matthew D. Palmer in:

  7. Search for Doug M. Smith in:

  8. Search for Josh K. Willis in:


J.M.L. led the writing and analysis, with writing contributions from G.C.J., J.K.W., M.D.P. and S.A.G., and analysis contributions from S.A.G., V.V.G., M.I., M.D.P., D.M.S. and J.K.W.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to John M. Lyman.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains Supplementary Methods, References, Supplementary Table S1 and Supplementary Figure S1 with legend.

About this article

Publication history






Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.