Quantifying underestimates of long-term upper-ocean warming, by Paul J. Durack, Peter J. Gleckler, Felix W. Landerer and Karl E. Taylor and published in Nature Climate Change (DOI: 10.1038/NCLIMATE2389) reports on their research to investigate estimates of the ocean heat content (OHC). While there is a record of measurements for the northern hemisphere, there is a lack of measurements in the south. Historically, the few measurements that were actually made were supplemented by using the northern measurements and interpolating values. Durack, et al. found the data for the southern hemisphere was good since 2004, but the heat content before then was underestimated. This, they concluded, underestimated the actual value of the ocean heat content by about 25%. They stated the amount of heat involved was great:
For our purposes here, what this means is the oceans are more sensitive to global warming than previously thought. It is also more evidence that there has been no warming 'pause,' as is frequently claimed. The amount of heat they cite is exceptional, even spread over 35 years. If we were to take the middle value of their range, that comes out to an average of .13 × 1022 J yr−1. In comparison, all power plants in the world combined generate about 1018 J yr−1, meaning it would take all of our power plants about 1,000 years to generate the amount of energy being absorbed by the oceans every year. That is significant.These adjustments yield large increases (2.2–7.1 × 1022 J 35 yr−1) to current global upper-ocean heat content change estimates, and have important implications for sea level, the planetary energy budget and climate sensitivity assessments.
Incidentally, this was done using real data, not models.
Here are some nice graphics showing the progression of ocean heating from 1955 - 2011.