Figure 1 is a copy of the graph of the Ocean Heat Content from page 4 of the article. It compares the original OHC data to the newly revised data. Unfortunately, they failed to document the depths for the data. If they did, I couldn’t find it in the article.
Using the coordinate capabilities of MS Paint, I “duplicated” the graph in Figure 2 so that I could run a few quick comparisons.
In Figure 3, the last few years of revised data have been deleted to make the time spans equal. Linear trends were then added. Note the minor decrease in trend between the original and the revised OHC data.
Figure 4 is a comparative graph of OHC and the Multivariate ENSO Index (MEI). Regrettably, there was no simple way to scale the MEI data to make it easier to compare to OHC, so I simply left it as raw annual data. There does not appear to be a consistent reaction of OHC to ENSO events. Note how, counter-intuitively, the OHC rises and falls in synch with SST during the 1997/98 El Nino. One would expect the OHC to decrease during that El Nino since the tropical east Pacific discharged so much heat into the atmosphere, but the OHC rose. Then the variation in OHC opposes the La Nina that follows, as expected. That specific period was selected because it is not influenced by volcanic aerosols.
The influence of stratospheric aerosols ejected from explosive volcanic eruptions can be seen in Figure 5. It‘s impossible, unfortunately, to draw any conclusions about the relationship between volcanic aerosols and OHC solely on this graph because volcanic aerosols are not the only significant natural variable capable of altering the amount of solar irradiance reaching the surface of the oceans.
More unfortunate is the lack of long-term cloud cover data. The only cloud cover data sets I’ve found begin in 1980 or thereabouts. Refer to Figure 6, which shows a decrease (about 4 to 5%) in global Total Cloud Amount from 1986 to 2000, then an increase (about 2 to 3%) from 2000 to 2005.
In Figure 7 I’ve compared OHC with annual scaled and ranged ERSST.v3 global SST data. Both display increasing trends, but the annual variability of SST far exceeds that of OHC.
Figure 8 illustrates the annual change in OHC. The period of sustained volcanic aerosols from 1960 to the early 1970s clearly suppressed annual variations in OHC.
At the end of my November 11, 2008 post about the Ishii and Kimoto proposed changes to OHC (linked above and below), I commented about the curious coincidence between the number of global ocean data profiles and the rise and fall in ocean heat content. It would be inappropriate for me to make the observation in that post but not in this, so I’ve repeated it here. While the revised OHC data in this post does not have the "hump" in the 1970s, OHC appears to have accelerated since the early 1990s. Oddly, this seems to coincide, though not perfectly in synch, with the surge in the number of readings.
From The Ishii and Kimoto Proposed Update to Ocean Heat Content:
UPDATE (November 14, 2008): Please note that I am not implying any wrongdoing on the parts of those who calculate Ocean Heat Content. I simply found the following to be an odd coincidence, one that should be discussed.
The following is a graph of the number of global ocean data profiles accumulated monthly from 1979 to 2006 by the NCEP Global Ocean Data Assimilation System for a depth of 0-250 Meters from 90S to 90N. It’s odd that in recent years the Ocean Heat Content rises above its previous high in the 1970s, while at the same time the number of subsurface ocean temperature readings increases drastically. Then the Ocean Heat Content peak and decline about the same time as the number of readings.
Number of Global Ocean Data Profiles
The Climate Prediction Center NCEP Global Ocean Data Assimilation System: Monthly Products webpage is here:
The Ocean Heat Content data was extracted from the graph in the above-linked NASA Earth Observatory article.
SATO Index data is available from GISS:
Multivariate ENSO Index data is available from the NOAA Earth System Research Laboratory:
Cloud Amount Graph is part of Figure 1 from Palle et al (2006)“Can Earth’s Albedo and Surface Temperatures Increase Together?” EOS Vol. 87, No. 4, 24 January 2006