Does Gavin Schmidt Understand Boundary Layer Physics?

I want to thank Bryan Sralla for alerting me to the comment by Gavin Schmidt on Real Climate  regarding  our papers 

Klotzbach, P.J., R.A. Pielke Sr., R.A. Pielke Jr., J.R. Christy, and R.T. McNider, 2009: An alternative explanation for differential temperature trends at the surface and in the lower troposphere. J. Geophys. Res., in press


Mahmood, R., R.A. Pielke Sr., K.G. Hubbard, D. Niyogi, G. Bonan, P. Lawrence, B. Baker, R. McNider, C. McAlpine, A. Etter, S. Gameda, B. Qian, A. Carleton, A. Beltran-Przekurat, T. Chase, A.I. Quintanar, J.O. Adegoke, S. Vezhapparambu, G. Conner, S. Asefi, E. Sertel, D.R. Legates, Y. Wu, R. Hale, O.W. Frauenfeld, A. Watts, M. Shepherd, C. Mitra, V.G. Anantharaj, S. Fall,R. Lund, A. Nordfelt, P. Blanken, J. Du, H.-I. Chang, R. Leeper, U.S. Nair, S. Dobler, R. Deo, and J. Syktus, 2009: Impacts of land use land cover change on climate and future research priorities. Bull. Amer. Meteor. Soc., in press.

The questions on Real Climate by Paul Klemencic and Gavin’s comment are reproduced below along with my responses.


Paul Klemencic says:

Paul Klemencic Question #1: Since this post was set up to discuss how to critique a scientific paper, I wonder whether an example from a paper currently in publication might be interesting. The paper accepted by Bulletin of the American Meteorological Society is “Impacts of Land Use Land Cover Change on Climate and Future Research Priorities” by Rezaul Mahmood, Roger Pielke Sr., et. al. A copy of the paper is here:

One of the key findings seems to summarized in this passage:

“The stable nocturnal boundary layer does not measure the heat content in a large part of the atmosphere where the greenhouse signal should be the largest (Lin et al. 2007; Pielke et al. 2007a). Because of nonlinearities in some parameters of the stable boundary layer (McNider et al. 1995), minimum temperature is highly sensitive to slight changes in cloud cover, greenhouse gases, and other radiative forcings. However, this sensitivity is reflective of a change in the turbulent state of the atmosphere and a redistribution of heat not a change in the heat content of the atmosphere (Walters et al. 2007). Using the Lin et al. (2007) observational results, a conservative estimate of the warm bias resulting from measuring the temperature from a single level near the ground is around 0.21°C per decade (with the nighttime minimum temperature contributing a large part of this bias). Since land covers about 29% of the Earth’s surface, extrapolating this warm bias could explain about 30% of the IPCC estimate of global warming. In other words, consideration of the bias in temperature could reduce the IPCC trend to about 0.14°C per decade; still a warming, but not as large as indicated by the IPCC. ”

A couple of quick questions on this result:

1. Is it fair to conclude that every one of the very large number of temperature measurements made on the land would be impacted by a surface boundary layer? Can a direct linear extrapolation be used to estimate the warming bias, as was done in this paper?

[Gavin Schmidt Response: As is being discussed in a number of places, there is a strong possibility of misunderstanding these statements. Changes in the BL structure for whatever reason do not cause the surface temperature trend to be wrong in any respect. If however you wanted to calculate the total heat content trend of the atmosphere (something which has not heretofore been a big requirement), then you would want to take the vertical profile changes into account (and not just in the boundary layer). If however, you are trying to compare observed surface trends to a model then you'd not have to make any corrections since a perfect model would have exactly this same behaviour. - gavin]

Roger A. Pielke Sr. Comment:

Our papers do not indicate that the measurement of the temperature is incorrect. It is the interpretation of the 2m temperatures in terms of the heat content trend above the surface that is the issue. Gavin actually agrees with this perspective, but then ignores its significance.  The use of a global average surface temperature trend to diagnose climate system heat changes introduces a bias in the magnitude of the heat changes.  The GISS communication of a global average surface temperature trend, as a surrogate to describe global warming is quantitatively flawed (e.g. see and see for how the global average surface temperature trend is linked to  climate system heat changes [global warming]).

Paul Klemencic Question #2:

2. It appears that correcting the land reading by the large warm bias in this report would wipe out almost all of the land warming trend. If so, is a stable or cooling land surface trend consistent with satellite measurements over the continents showing warming of the lower and mid-level troposphere?

[Gavin Schmidt Response:This is not evidence that the land surface trend needs to be adjusted if you are comparing like with like. There is plenty of reasons to expect the land surface trend to be faster than the ocean trends - just as is observed. - gavin]

Roger A. Pielke Sr. Comment: Gavin shows that he does not understand the issue raised in the text from the Mahmood et al paper.  There is a significant bias in the use of 2m minimum temperatures as a diagnostic for deeper atmospheric temperature trends and anomalies.  I can only imagine that Gavin superficially read our papers, if he read them at all.  He does clearly inadequately understand boundary layer dynamics.

Paul Klemencic Question #3:

3. The paper seems to conclude that much of the warming bias is due to heat generated from man’s activities other than the GHG forcing. Is the heat released from mankind’s activities enough to explain the warming bias of 0.21 K per decade?

[Gavin Schmidt Response:Really? First off, this isn't evidence that there is a bias in the surface temperature trends. Secondly, I don't think this is related to the direct output of waste heat into the atmosphere. This might be locally important in some regions, but as a global effect (or even just a land effect) it is a couple of orders magnitude smaller than the impact of increased CO2 on the forcing. - gavin]

Roger A. Pielke Sr. Comment: Here Paul Klemencic misinterprets the papers.  While waste heat certainly is another effect that will alter the minimum temperatures, the issue we raise occurs whenever there are stably surface boundary layers. This typically occurs everywhere at night (particularly on clear and light wind nights) and in the high latitudes in the winter.  This happens even in pristine landscapes. Gavin Schmidt, by not reading the papers, or as a result of his lack of knowledge regarding boundary layer dynamics, did not accurately reply to Paul’s question.

Final Paul Klemencic Comment

If you would prefer to defer addressing this issue and answering these questions at this time, I will understand.

Roger A. Pielke Sr. Comment:  Gavin Schmidt should have invited me (or one of our other co-authors to respond). Clearly, however, despite clear evidence of his inadequate lack of knowledge of boundary layer physics, he elected to be the authority on our research papers.  This just further documents that Real Climate does not present balanced viewpoints on research papers, but uses misinformation to seek to discredit them. This is a pity, since Gavin Schmidt, if he would educate himself on the issues we raise, could contribute significantly to a constructive discussion of our papers. So far, he has not done so.

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