Grappling With Reality – A Comment On The Skeptical Science Post By Dana1981 “Modeled and Observed Ocean Heat Content – Is There a Discrepancy?”

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Skeptical Science has a post by dana1981 [where he presents his profile online, but not his name; his photo - sort of - is above - July 24 2012 -  found out from Twitter that is name is Dana Nuccitelli] titled

Modeled and Observed Ocean Heat Content – Is There a Discrepancy?

The short answer is YES. This subject has been discussed in my posts ; e.g. see

Comment On Ocean Heat Content “World Ocean Heat Content And Thermosteric Sea Level Change (0-2000), 1955-2010″ By Levitus Et Al 2012

Jim Hansen’s 1981 Model Prediction Needs Scrutiny

Comments On The Poor Post “Lessons from Past Predictions: Hansen 1981″ By Dana1981 At The Skeptical Science

as well as by Bob Tisdale in his post

Corrections to the RealClimate Presentation of Modeled Global Ocean Heat Content

and in the post by David Evans

The Skeptic’s Case

In the Skeptical Science post by dana1981, he also discusses the issue, and concludes with [highlight added]

In any case, while the OHC issue is not entirely settled in either models or observational data, climate contrarians have exaggerated the possible disrepancy between the two through their standard scientific denial practice of cherrypicking data.  It will be interesting to see how this issue is resolved in the coming years as observational data and climate models improve, and in the forthcoming IPCC Fifth Assessment Report, but in the meantime exaggerating the possible discrepancy is neither constructive nor truly skeptical behavior.

Unfortunately, while he finally (correctly) recognizes that “the OHC issue is not entirely settled in either models or observational data“, he does not seem to recognize his own biases. He has avoided several fundamental issues. His exclusions include:

  • There is no need to diagnose a linear trend in upper ocean heat content, if one can accurately measure the heat content in Joules at two different time periods. This difference can be directly used to diagnose the global upper ocean average energy flux over this time period in Watts per meter squared.  The real world ocean itself does the time and space integration.  Thus, using an eyecrometer, all one needs to do is read off the values in Joules at two different time periods.

I discuss this approach in my paper

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

Since, there are, of course, uncertainties in the ocean measurements, a range around the best estimates is needed. Levitus et al 2012 did that for their study as did Josh Willis in the figure in my paper

Pielke Sr., R.A., 2008: A broader view of the  role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55.

I suspect the uncertainties in the deeper ocean data of Levitus et al 2012 are too small, given the limited spatial coverage at that depth, but, nonetheless this uncertainty needs to be presented.

The next issue is

  • The claim that heat is temporally sequestered in the deeper ocean (a hiatus), avoids the uncomfortable conclusion that this heat is not represented in an global average surface temperature anomaly.

I posted on this, for example, in

Torpedoing Of The Use Of The Global Average Surface Temperature Trend As The Diagnostic For Global Warming

where I wrote that

1.  If heat is being sequestered in the deeper ocean, it must transfer through the upper ocean. In the real world, this has not been seen that I am aware of. In the models, this heat clearly must be transferred  (upwards and downwards) through this layer. The Argo network is spatially dense enough that this should have been see.

2. Even more important is the failure of the authors to recognize that they have devalued the use of the global average surface temperature as the icon to use to communicate the magnitude of global warming.  If this deeper ocean heating actually exists in the real world, it is not observable in the ocean and land surface temperatures. To monitor global warming, we need to keep track of the changes in Joules in the climate system, which, as clearly indicated in the new study by Meehl and colleagues, is not adequately diagnosed by the global, annual-averaged surface temperature trends.

and that

……… if heat really is deposited deep into the ocean (i.e. Joules of heat) it will dispersed through the ocean at these depths and unlikely to be transferred back to the surface on short time periods, but only leak back upwards if at all. The deep ocean would be a long-term damper of global warming, that has not been adequately discussed in the climate science community.

In the paper

Barnett, T.P., D.W. Pierce, and R. Schnur, 2001: Detection of anthropogenic  climate change in the world’s oceans. Science, 292, 270-274

they wrote

“…..a climate model that reproduces the observed change in global air temperature over the last 50 years, but fails to quantitatively reproduce the observed changed in ocean heat content, cannot be correct. The PCM [Parallel Climate Model] has a relatively low sensitivity (less anthropogenic impact on climate) and captures both the ocean- and air-temperature changes. It seems likely that models with higher sensitivity, those predicting the most drastic anthropogenic climate changes in the future, may have difficulty satisfying the ocean constraint.”

The next issue ignored by dana 1981 is that

  • The energy flux value of upper ocean heating (when scaled with respect to its estimated fraction of the total magnitude of global warming; e.g. see Hansen’s 2005 estimates here), regardless of the values selected by dana1981 or his commenters from the models and observations, is significantly less than the radiative forcing claimed in the 2007 IPCC report.

As I wrote in my post

Climate Metric Reality Check #1 – The Sum Of Climate Forcings and Feedbacks Is Less Than The 2007 IPCC Best Estimate Of Human Climate Forcing Of Global Warming

If the magnitude of the IPCC estimates of radiative forcings from human causes are greater than or equal to the sum of the total observed radiative forcings and feedbacks (i.e. the total climate system radiative imbalance), then the feedbacks have actually reduced the effect of radiative forcings caused by human activities.  By contrast, if the magnitude of radiative forcing caused by humans is less than the sum of the total observed radiative forcings and feedbacks than the feedbacks have amplified the human radiative forcings.

In this….reality check, the information that is used is

1. Total Radiative Forcing from Human Causes

The radiative forcings from human causes are provided by the 2007 IPCC Report [see page 4 of the Statement for Policymakers; Fig. SPM.2].

Their value is +1.6 [with a range of +0.6 to +2.4 Watts per meter squared]

This value, as reported in a footnote in the IPCC report, is supposed to be a difference with between current and pre-industrial values (but note that that this is not what is stated in the figure caption).

2. Total Observed Radiative Forcings and Feedbacks

Ocean heat content data can be used to diagnose the actual observed climate forcings and feedbacks [Pielke Sr., R.A., 2003: Heat storage within the Earth system]. Here I will use Jim Hansen’s value for the end of the 1990s of

+0.85 Watts per meter squared

(even though this is probably an overstatement (see)).

Thus, the total observed radiative forcing and feedback of 0.85 W/m^2 lies below the IPCC central estimate of 1.6 W/m^2 for just the human contribution to radiative forcing.  This suggests that the climate feedbacks most likely act to diminish the effects of human contributions to radiative forcing, though it is important to recognize that a small part of the IPCC range (0.6 to 0.85) falls under the observed value from the work of Hansen.

This suggests that, at least up to the present, the effect of human climate forcings on global warming has been more muted than predicted by the global climate models.

This issue was inadequately discussed by the 2007 IPCC report. Climate Science has weblogged on this in the past (e.g. see), but so far this rather obvious issue has been ignored.

Dana1981 inadequately examines this issue. Negative forcing from aerosols could explain an observed lower heating, but this would then indicate the 2007 IPCC SPM WG1 estimate of total radiative forcings has significant errors. However, there is an even more significant concern. Where is the positive radiative feedback from claimed increases in atmospheric water vapor? This is an issue ignored in dana1981′s post.

Finally, it is interesting to read the comments which seek to argue that the issues raised in the posts are not very important. For example, one by Tom Curtis reads

So far as I can see, once we use a correct base lining, the divergence issues become the minor issues discussed already by Dana.

At least dana1981 does ask the question -

Modeled and Observed Ocean Heat Content – Is There a Discrepancy?

The answer is YES.

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