There is a candid, honest, and informative article by Josh Willis that appeared in the newsletter U.S. Clivar Variations. It is

Is It Me, or Did the Oceans Cool? A Lesson on Global Warming from my Favorite Denier (Link) by Josh K. Willis of the Jet Propulsion Laboratory of the California Institute of Technology.

It is worth reading. The article chronicles his experience with correcting the error in his original analysis, but also in presenting us with an effective summary of the current science and engineering of diagnosing ocean heat content. He presents two informative figures in the article, which are reproduced below.

Sea level thermal expansion graph
© unknown

Argo ocean floats
© Argo Project

There are two major conclusions that are evident from these figures:
  1. In Figure 2, the wide distribution of the profiling floats provides very good spatial coverage of the oceans except for the highest latitudes
  2. As discussed in Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bulletin of the American Meteorological Society, 84, 331-335, it is the change in ocean heat content that provides the most effective diagnostic of global warming and cooling. Thus unless further checks on the upper ocean measurements find errors, there has been no significant ocean heating since mid-2003. This means that we now have 5 1/2 years without global warming as measured by this climate metric.