the Air Vent

Because the world needs another opinion

Are Climate Models Spatially Consistent?

Posted by Jeff Id on June 29, 2012

An interesting link left by Curious on the open thread. I will read later. –Jeff

h/t Curious, HR at Watts Up tips and notes:

Click to access cpd-8-2409-2012.pdf

Climate of the last millennium:ensemble consistency of simulations and reconstructions
O. Bothe, J. H. Jungclaus, D. Zanchettin, and E. Zorita

Are simulations and reconstructions of past climate and its variability comparable with each other? We assess if simulations and reconstructions are consistent under the paradigm of a statistically indistinguishable ensemble. Ensemble consistency is assessed for Northern Hemisphere mean temperature, Central European mean temperature and for global temperature fields for the elimate of the last millennium. Reconstructions available for these regions are evaluated against the simulation data from the community simulations of the climate of the last millennium performed at the Max Planck Institute for Meteorology.

The distributions of ensemble simulated temperatures are generally too wide at most locations and on most time-scales relative to the employed reconstructions. Similarly,an ensemble of reconstructions is too wide when evaluated against the simulation ensemble mean.Probabilistic and climatological ensemble consistency is limited to sub-domains and sub-periods. Only the ensemble simulated and reconstructed annual Central European mean temperatures for the second half of the last millennium demonstrates consistency.

The lack of consistency found in our analyses implies that, on the basis of the studied data sets, no status of truth can be assumed for climate evolutions on the considered spatial and temporal scales and, thus, assessing the accuracy of reconstructions and simulations is so far of limited feasibility in pre-instrumental periods.

6 Responses to “Are Climate Models Spatially Consistent?”

  1. No. To properly consider spacial impacts models would have to have a moist air/ocean module, dry air/ice module and a mixed module that considers transitions. The moist air/ocean area expands and contracts and has totally different physics than the dry or mixed conditions.

  2. lucia said

    Capt. Dallas–
    You are describing what you think is required for the models to get the right answer. The abstract seems to be saying one model doesn’t even get get the same answer as the other ones.

    Obviously, if they all got the right answer, they would all also get the same one. But currently, even if one model (or some) are getting the right answer, they disagree with others. So clearly others are getting the wrong one. And we don’t know which is right. The other possibility is they are all wrong– and disagree with each other too.

    • Yes, without starting with a solid foundation, there would be dozens of different answers. For the models to approach a correct answer they would have to correctly consider different aspects of the system. An ocean only model would not give you a correct answer, but a consistent answer if the physics are correct. A land only would not give you a correct answer but a consistent answer if the physics are correct. The correct answer should be between the two models. If the models are coming up with a variety of answers considering one surface or the other, then the physics are not correct.

      Now I have cheated and made my own crude model, but if you use a moist air model and a radiant model, you will get the correct answer. The problem then would be the spacial considerations of what is land, what is water and what is mixed. Each have different physics.

      So finding the right starting point, that thermodynamic frame of reference you think I am using incorrectly, leads to building a more informative model.

      Pretty interesting as well, I still have to fine tune the salinity impacts and figure CO2 impacts on thermal conductivity, but it is getting there.

  3. Kenneth Fritsch said

    I have been studying (or as an amatuer I should use perhaps the term “looking at” here) consistencies of proxies/reconstructions in the same or proximate locations. It is those proxy variations that make me wonder why little attention has been paid to these inconsistencies in proxy responses. It would appear that the conclusion must either be that the proxies are invalid thermometers or that, given the localized variations in temperatures that these proxies are supposed to be measuring, placing reasonable uncertainty limits on a mean regional or global temperature would require huge numbers of proxies.

    • timetochooseagain said

      Lack of nearby agreeing proxies means one of two things, both of which are problematic for current climate science ™:

      1. The Rossby Radius of Deformation doesn’t lead to smoothing out of near surface temperature variations over long distances and things like GISS’s extrapolation over the poles are wrong.

      2. Proxies are not good thermometers.

      Now, actually, the first being true would not be too surprising. The Rossby Radius is inversely proportional to the Coriolis Parameter (which makes Arctic extrapolation on that basis really bizarre) and works best when there is minimal turbulent diffusion, ie mostly above two kilometers (which makes the extrapolation odd in general). Nevertheless, let us suppose that actual, as opposed to proxy “temperatures”, are smoothed over long distances, even in the Arctic and even in the boundary layer. That leaves the second possibility. Either way, as you say:

      “given the localized variations in temperatures that these proxies are supposed to be measuring, placing reasonable uncertainty limits on a mean regional or global temperature would require huge numbers of proxies.”

  4. Brian H said

    Obviously, the ensemble of many stupids is smart. The very foundation of Climate Science!

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