An Excellent Question!

From here.

how can the variability seen in the numbers calculated by GCMs be assigned to be weather.  If the numbers are weather, then it is clear that it cannot be the correct weather.  If climate is taken to be the average of weather, how can the average of the weather calculated by GCMs be expected to have any fidelity to actual future states of the Earth’s climate systems.

I have long wondered myself, why is it that if climate is average weather, and long term weather prediction is not possible, that the average of unpredictable weather is somehow predictable? The only thing I can think of, is that weather is assumed to be distributed around mean that it is entirely a deviation from, that no matter what the weather is, averaged over a long enough period the same “climate” emerges. This requires, however, that the system somehow “knows” that it needs to make up for when it was too cold or too hot because of weather, with enough of the opposite kind of variation to maintain the mean the same. But if the weather is truly random, how can it possibly be certain that it would, in fact, always tend back to the mean? I suppose one could also allow for the mean over a long enough period to be close to the “climate” but not necessarily there, in which case climate is not perfectly predictable, but within some reasonable limits, can be almost predicted. But the only other problem I can think of with this reasoning, is that the physical processes which determine climate, the crucial feedbacks of clouds and water vapor, are critically dependent on processes involving weather systems, on short timescales. If the behavior of weather systems is not predictable, how can the feedback processes be predicted?

Believe it or not, I really am honestly confused by this, and would like to know. My view has always been that means are determined by their components, not the other way around, and in that way I view climate as determined by the weather, not the other way around, and as a related issue, I would like to know if anyone thinks I am way off base on this.


2 Responses to “An Excellent Question!”

  1. Rob R Says:

    “I would like to know if anyone thinks I am way off base on this”

    So would I.

    I think this is at least partly the question that Spencer and Braswell are investigating.

  2. timetochooseagain Says:

    It just seems to me to be a perfectly reasonable thing to wonder about.

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