Ocean warming underestimated

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Accurate estimates of global ocean warming are required to understand contributions to observed sea‐level and energy budget changes and to constrain empirical estimates of climate sensitivity. Our analysis finds that modeled hemispheric ratios of SSH (sea surface height) changes are consistent with highly accurate altimetry observations but remarkably inconsistent with in‐situ based hemispheric ratios of OHC (ocean heat content) changes. Adjusting the poorly constrained SH (southern hemisphere) OHC change estimates to yield an improved consistency with models, produces a previously unaccounted for increase in global upper‐OHC of 2.2‐7.1 x 1022 J above existing estimates for 1970 to 2004 (Figure 5, upper inset).

For perspective, these adjustments represent more than double the 1970‐2004 heat storage change for all non‐ocean (terrestrial, cryospheric and atmospheric) heat reservoirs combined (Rhein et al., 2013), and highlights the importance of accurately estimating ocean temperature changes. By contrasting hemispheric changes in an attempt to quantify the impact of SH observation deficiencies, our analysis should motivate further work to improve estimates of global OHC change.

QUANTIFYING UNDERESTIMATES OF LONG‐TERM UPPER‐OCEAN WARMING

Durack, P. J., P. J. Gleckler, F. W. Landerer and K. E. Taylor (2014) Quantifying underestimates of long term upper‐ocean warming. Nature Climate Change, 4 (11), pp 999‐1005. doi: 10.1038/nclimate2389