Comment On Real Climate’s Post By Gavin Schmidt – “Ocean Heat Content Increases Update”

There is a post by Gavin Schmidt  on Real Climate on May 21 2010 titled “Ocean heat content increases update” .

Gavin, unfortunately, does not comment about and question the odd jump in the warming earlier in the current decade that is seen in the plot of upper ocean heat data, the Lyman et al 2010 paper, and which he presents in his post. Indeed, the greater warming in the Lyman et al 2010 paper that he accepts unquestionably [which he writes is  "a greater warming than seen in the NODC data and more than even the models"] is due specifically to a short-term jump. Since this is the time that the Argo Network finally achieved global coverage the reason for this jump needs more exploration. However, this jump is not seen in the sea surface temperature data (see from Bob Tisdale’s weblog).

Here is Josh Willis’s response to my query to him on this jump, which is reproduced from my post of December 29 2009 titled

Comment From Josh Willis On The Upper Ocean Heat Content Data Posted On Real Climate

The text of this post is

Real Climate has a post titled  Updates to model-data comparisons which includes a plot of the variations in upper ocean content anomalies from the period 1955 through 2009 .  

I asked Josh Willis the following with respect to the plot in the Real Climate post

My question:

Real Climate has posted a plot of ocean heat content, which we have
 discussed before, that shows a sudden jump in the 2002-2003 time frame;

 This jump is not seen it other metrics, including the surface temperatures
 (which they show) or the lower tropospheric temperatures (e.g. see

 see Figure 7 TLT

 Can you comment on the realism of this jump? Would you be willing to let me
 post your reply, if you do comment?

 Most of their trend agreement with the models is due to this single jump.

Josh Willis’s reply [reproduced with his permission]

There is still a good deal of uncertainty in observational estimates of ocean heat content during the 1990s and into the early part of the 2000s. This is because of known biases in the XBT data set, which are the dominant source of ocean temperature data up until 2003 or 2004. Numerous authors have attempted to correct these biases, but substantial difference remain in the “corrected” data.  As a result, the period from 1993 to 2003 still has uncertainties that are probably larger than the natural or anthropogenic signals in ocean heat content that happen over a period of 1 to 3 years.  However, the decadal trend of 10 to 15 years seems to be large enough to see despite the uncertainties. Because Argo begins to become the dominant source of temperature data in about 2004, the period from 2000 to 2005 is especially worriesome because of the transition from an XBT-dominated estimate of ocean heat content.

You might also comment that there is another easily available estimate besides that of Levitus et al. (the one shown in this blog entry).  The other long-term estimate is from Domingues et al. and can be downloaded from CSIRO:

 What Gavin is also ignoring in his post is that  the rate of  heating has flattened since 2004 even in the Lyman et al 2010 paper. The NODC data even shows cooling.  This is the “missing heat” that Keven Trenberth has discussed (see).

This failure for Gavin to comment on other perspectives is evident in one of the comments on his post. There is an informative comment on May 24 2010 by Alex Harvey which reads

Gavin #60,

I am still left with the impression that you are evading the question of the meaning and significance of the Pielke/Willis/Trenberth exchange.

We all know, of course, Trenberth’s now famous behind the scenes remark that it is a travesty that we can’t account for the lack of recent global warming, and his exclamation that the observing system must be inadequate (which I guess is reference to the satellite radiation budget measurements?). Trenberth later claimed that there is heat missing and that it must lie beneath >700m in the deep ocean and that it may come back “to haunt us”. But Willis then agreed with Pielke that it is probably impossible and that it’s unlikely we’ll find any missing heat below 700m. Pielke Jr spelt it out for us the next day that this means the “missing heat” is probably missing because it has been radiated out into space, or in layman’s terms, because it’s just not there.

Now a few weeks later we find ocean heat has been adjusted upwards by Lyman et al. and we find Josh Willis one of the coauthors. Yet Willis already agreed that he thought the existing measurements were pretty good. Pielke has used Willis’s data to show a decline in OHC since 2003 which doesn’t appear in this the new Lyman et al analysis. (In fact, it looks like Willis has frankly got his own name on two of the curves in your diagram, both the NODC data and the Lyman et al data. Is that right?)

So what is the conclusion for this? There is missing heat below 700M or there isn’t?

Best, Alex

[Response: There is clearly some heating going on below 700m. But this discussion of 'missing' heat is very confused. The satellite records are not good enough to say what the year-to-year imbalance is and so are not able to say whether any heat is missing or not. So what is the 'missing' idea based on? Model estimates - but as I showed above, the estimates of OHC change are in line with the models, and so I don't see why anyone thinks that any heat is missing. If the satellite data were better, there might be something to this, but right now the issues are all in the noise, and thus pretty unresolvable. - gavin]

What Gavin does not comment on is that the upper ocean heat data is a more robust metric to diagnose the global average radiative imbalance than the estimates of the radiative fluxes from satellites. This was shown as early as in the paper

Ellis et al. 1978: The annual variation in the global heat balance of the Earth. J. Climate. 83, 1958-1962

 I discussed the consequences in terms of diagnosing the radiative forcing in

Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335.

Gavin also ignores the excellent paper

Douglass, D.H. and R. Knox, 2009: Ocean heat content and Earth’s radiation imbalance. Physics letters A.

What Gavin Schmidt has done is to present an uncritical assessment of the Lyman et al 2010 paper without questioning the robustness of its findings. I am pleased that at least one commenter on Real Climate recognized  (and was permitted to post) this lack of scientific balance in Gavin’s post.

Comments Off

Filed under Climate Change Metrics

Comments are closed.