onsdag 18 november 2009

The Weather in Målilla and Global Climate

                          Kuno Schröder measuring the temperature since 2004 in Målilla.

In Part II Mathematics of Turbulence of my book with Johan Hoffman Computational Turbulent Incompressible Flow from 2007, we show in Chapter 13 Turbulence and Chaos that turbulent fluid dynamics is
  • short-time pointwise predictable
  • long-time pointwise unpredictable
  • long-time mean-value predictable
illustrated by the temperature variation in the little idyllic village of Målilla  in the county of Småland  in southern Sweden, for which data are available from the Swedish Institute of  Meteorology SMHI since 1860. Målilla has the Swedish record high of 38 degrees Celcius from 1948, before global warming was invented...  

We see, as we all know, that the daily temperature can only be predicted a couple of days ahead, to a meaningful tolerance, while the monthly or even better yearly mean-value can be predicted years ahead to a meaningful tolerance.

These are also features of climate dynamics, which is a form of weather dynamics on large space-time scales, but long-time prediction is difficult because of the complexity of the modeling.

We are thus pleased to see that our book, written before we lifted our horizon to climate dynamics, directly connects to the crucial question of accuracy and reliability of climate models. We see these connections in particular in the recent  text by HK Climate.

We also note that Nowcast reports from a weathercasters poll that only 19% agree to the statement that global climate models are reliable in their projections for a warming of the planet. If weathercasters don't believe in climate models, and they should know since they have a lot of experience, who could believe? Believers should answer one simple question and maybe take a look at the comparison between model prediction and real outcome.

Even Swedish Radio P1-Morgon Nov 20 reports on alarmism skepticism represented by Richard Lindzen and John Christy claiming that climate models exaggerate climate sensitivity
because they are programmed to do that. Mass illusion and hysteria, according to Lindzen, who is quite out-spoken...

2 kommentarer:

  1. Your first three paragraphs are perfectly correct. Your fourth, "These are also the features of climate dynamics, which is also a form of weather dynamics only on larger space-time scales" is wrong.

    You have already conceded that chaotic dynamics are "long-time mean-value predictable". We define climate prediction precisely as the prediction of such predictable long term statistics.

    (There is a discipline of predicting two month to eighteen month prognostics that calls itself "climate prediction" that is essentially weather prediction of the slower dynamics of the ocean. It is dominated by heuristics and has demonstrated very limited value at best. If your criticism is with this field I agree with you. Indeed some of the most vocal IPCC critics like Gray and Landsea come from this tradition. But this is NOT the sort of climate prediction taht the controversy is about.)

    The decadal to millenial time scale falls neatly into the class of in-principle-predictable statistics. Whether the predictions are useful in practice is another matter, but that is, you will acknowledge, an entirely different argument.

    Regardless, it is clear that anthropogenic forcing must have SOME impact on the dynamics. Are you saying it is impossible to apply reason to any extent whatsoever about such impacts?

    If so, if the available information about the impact of emissions really is absolutely nil, then the risk of substantial alteration of the atmosphere is unbounded and the rational policy is to avoid such alteration with the most extreme rigor.

    Normally people arguing against climate science oppose regulation of emissions, but this has always seemed to me logically inconsistent. I expect it from politicians and journalists, but not scientists.

  2. Thanks for the comment. I have changed the wording to better express
    what I wanted to say.