>The November 5, 2008, NASA Earth Observatory article “Correcting Ocean Cooling”… http://earthobservatory.nasa.gov/Features/OceanCooling/…contained the graph of the newly revised Ocean Heat Content on page 4 of the article. It compares the original OHC data to the newly revised data. Figure 1 is that graph.
Using the coordinate capabilities of MS Paint, I “duplicated” the graph of the revised data in Figure 2 so that I could run a few quick comparisons in my post “Revised Ocean Heat Content.”
In the Recent Ocean Heat and MLO CO2 Trends thread at WattsUpWithThat, blogger DJ provided a link to the NOAA National Oceanic Data Center’s upcoming Levitus et al paper on Ocean Heat Content to be published in Geophysical Research Letters.
Figure 3 is the OHC graph from that webpage. Note the Annual data since 2004.5. What happened to the significant drop in 2007 in Figure 1? Have trouble seeing the difference between Figures 1 and 3?
Following the “basin time series” links will bring you to the NODC’s listing of “WORLD” Yearly Ocean Heat Content from 1955 to 2007.
Figure 4 is a comparative graph of the data I created from the Earth Observatory article and the data used in the Levitus et al paper. The two datasets track well until 2007.5.
WHICH IS THE CORRECT DATASET?
As illustrated in Figure 4, the depiction of Ocean Heat Content varies from month to month even from the same data supplier. But there are other recent papers that illustrate Ocean Heat Content. These are illustrated in the manuscript of the Levitus et al (2009) paper “Global Ocean Heat Content 1955-2008 in light of recently revealed instrumentation problems”. Refer to Figure 5, which is Figure S9 in the Levitus et al paper. [Note that the Levitus et al data (red curve) includes the 2008 data in this graph.] Levitus et al, Ishii and Kimoto, and Dominguez et al were all published within a year of one another. All three papers illustrate the same variable, but the data varies significantly between the three datasets. Note the divergence of the Levitus et al data (red curve) in 2003.
A decade from now, when researchers sort out the problems of measuring Ocean Heat Content, when they agree on the methodologies to be used to calculate it, it may serve as a worthwhile measure of climate change. At present it does not.
UPDATE – May 7, 2009
Let me clarify my closing comment about the OHC reconstructions.
Given: El Nino events redistribute heat from the tropical Pacific to the high latitudes so that it can be radiated into space more readily. Let’s say I wanted to analyze the 1997/98 El Nino to the determine how much of that heat was released to the atmosphere and how much was simply redistributed to the extratropical North and South Pacific and to other ocean subsets. Refer to the following graph. It’s the comparative graph of Levitus et al, Ishii and Kimoto, and Domingues et al OHC datasets, Figure S9 in the Levitus et al paper. I’ve highlighted 1997 and 1998. In 1997, the OHC in all three datasets increased, and in 1998, they all decreased. BUT look at the differences in the magnitudes of the changes in 1998. Which dataset depicts the changes correctly? Right now, I don’t have enough confidence in any of them to do the study I’ve suggested.