Comments On An E-mail Exchange With James Annan

James Annan and I have been exchanging e-mails over the weekend, and while he clearly is misunderstanding the focus of the papers,

Pielke Sr., R.A., and T. Matsui, 2005: Should light wind and windy nights have the same temperature trends at individual levels even if the boundary layer averaged heat content change is the same?Geophys. Res. Letts., 32, No. 21, L21813, 10.1029/2005GL024407

Lin, X., R.A. Pielke Sr., K.G. Hubbard, K.C. Crawford, M. A. Shafer, and T. Matsui, 2007: An examination of 1997-2007 surface layer temperature trends at two heights in Oklahoma. Geophys. Res. Letts., 34, L24705, doi:10.1029/2007GL031652.

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.

the fact that he is engaging in more-or-lessconstructive debate is encouraging.

I have posted below my edited latest reply to James, as the information should be useful to those have been misled by James’s and Gavin Schmidt’s posts on our paper [James still concludes this is only about the radiative forcing of CO2; James’s statement in the comments that “At least it now seems fairly clear from the recent distraction tactics (eg belatedly trying to convolute the effect of different atmospheric states with that of anthropogenic forcing) that he realises his error” still emphasizes his missing the point on our papers].

Here is my latest e-mail.  With James permission, I would post his also.

E-Mail to James Annan August 23 2009


 I do not reject the figure by Woods. That figure presents the instantaneous radiative flux divergences for the specific vertical profiles used in that analysis. However, it does not have the time integration that would result in the development of a stable boundary layer near the surface.

 To more closely illustrate the actual issue in our papers, as one example, we compute vertical heating rates all of the time in our modeling. As an easily accessible sample, see Fig 8-6 in my modeling book [Mesoscale MeterologicalModeling, 2nd Ed. 2002] for a location in Australia. The rate of cooling is about 0.18K per hour with the largest cooling near the surface. At 1.5 km, it is about an order of magnitude smaller. An alteration in the vertical distribution of this heating will necessarily alter the minimum temperature at 2m.

 What I see is the issue is that you are fixated on the radiative effect of doubled CO2. I agree with you that it is a much smaller effect than other influences on changing the vertical distribution of the heating.  In the Eastman et al 2001 paper , see Figure 8. These results present an integrated analysis of the effect on the vertical distribution of heating on minimum temperatures where both radiative flux divergence and vertical divergence of turbulent heat fluxes are included.

 The radiative effect of CO2 on the minimum temperature is an inconsequential -0.017 C, but it does have an effect. The biogeochemical effect (which alters stomatal conductance and the growth of leaf area and roots during the period of the simulation) is +0.097 C and the land use change is +0.261 C. The later two are significant. Both of the later, we attribute to the addition of water vapor into the atmosphere [and its effect on the vertical profile of the long wave radiative flux divergence] as a result of the greater leaf area.

 Thus the focus on the radiative effect of doubled CO2, which was presented in P&M as just one example of what could alter 2m temperatures, is a diversion from the focus of our paper. Anything which alters the vertical distribution of heating will alter the temperatures at 2m. If the alteration is systematic over years, it will result in a bias in the interpretation of the 2m temperature trends (anomalies) as moving in tandem with the trends (anomalies) higher up.

 I invite you to comment on the core of the three papers [P&M; Lin et al; and Klotzbach et al] instead of the peripheral discussion of TOA and surface radiative heating from the doubling of CO2. The core issue is

“Our results also indicate that the 1.5 or 2 m minimum long term temperature trends over land are not the same as the minimum long term temperatures at other heights within the surface boundary layer (e.g. 9 m), even over relatively flat landscapes such as Oklahoma. For landscapes with more terrain relief, this difference is expected to be even larger.

Therefore, the use of minimum temperatures at 1.5 or 2 m for interpreting climate system heat change is not appropriate. This means that the 1.5 to 2 m observations of minimum temperatures that are used as part of the analysis to assess climate system heat changes (e.g., such as used to construct Figure SPM-3 of Intergovernmental Panel on Climate Change [2007] and of Parker [2004, 2006] study) lead to a greater long term temperature trend than would be found if higher heights within the surface boundary layer were used.”

Your comments on the above conclusion would be where the focus of your weblogs are. If you disagree, discuss why. 

 You are using the discussion of the role of the radiative effect of added CO2 in  directly altering the surface fluxes as an way to divert attention from the actual conclusions of our paper. Indeed, if we accept your interpretation that the direct radiative effect of doubled CO2 is so small, yet the other effects, such as land use change are so much more important even at short time periods, we should take away the message that there is much more to climate change than just changes in the radiative top of the atmosphere forcing due to added CO2.

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