Formal detection and attribution studies have used observations and climate models to identify an anthropogenic warming signature in the upper (0–700 m) ocean1,2,3,4. Recently, as a result of the so-called surface warming hiatus, there has been considerable interest in global ocean heat content (OHC) changes in the deeper ocean, including natural and anthropogenically forced changes identified in observational5,6,7, modelling8,9 and data re-analysis10,11 studies. Here, we examine OHC changes in the context of the Earth’s global energy budget since early in the industrial era (circa 1865–2015) for a range of depths. We rely on OHC change estimates from a diverse collection of measurement systems including data from the nineteenth-century Challenger expedition12, a multi-decadal record of ship-based in situ mostly upper-ocean measurements, the more recent near-global Argo floats profiling to intermediate (2,000 m) depths13, and full-depth repeated transoceanic sections5. We show that the multi-model mean constructed from the current generation of historically forced climate models is consistent with the OHC changes from this diverse collection of observational systems. Our model-based analysis suggests that nearly half of the industrial-era increases in global OHC have occurred in recent decades, with over a third of the accumulated heat occurring below 700 m and steadily rising.
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The work of P.J.G. and P.J.D., from Lawrence Livermore National Laboratory, is a contribution to the US Department of Energy, Office of Science, Climate and Environmental Sciences Division, Regional and Global Climate Modeling Program under contract DE-AC52-07NA27344. C.E.F. was partially supported by the US Department of Energy, Office of Science, Office of Biological and Environmental Research, grants DE-SC0004956 (as a member of the International Detection and Attribution Working Group (IDAG)) and DEFG02-94ER61937 and by the National Science Foundation through the Network for Sustainable Climate Risk Management (SCRiM) under NSF cooperative agreement GEO-1240507. G.C.J. is supported by NOAA Research and the NOAA Ocean Climate Observations Program. We thank K. Taylor, B. Santer and J. Gregory for their helpful suggestions concerning our analysis. We acknowledge the sources of observed data used in this study: C. M. Domingues, M. Ishii and M. Kimoto, S. Levitus and T. Boyer, S. Purkey and G. Johnson, D. Roemmich and J. Gilson, S. Hosoda, T. Ohira and T. Nakamura and the International Pacific Research Center. We thank the climate modelling groups (listed in Supplementary Table 1) for producing and making available their model output.
About this article
Meteorology and Atmospheric Physics (2018)