Tuesday, May 21, 2013



These are some of the keywords used in headlines describing the latest puzzle facing scientists in the climate change arena.

    " Scientists are struggling to explain a slowdown in climate change that has exposed gaps in their understanding and defies a rise in global greenhouse gas emissions."


    " The rate of global mean warming has been lower over the past decade than previously. It has been argued that this observation might require a downwards revision of estimates of equilibrium climate sensitivity "


What's Up?

First, I am not a climate change denier, nor am I an advocate.  With a passing familiarity with modeling and simulation, I have always been somewhat skeptical of gospel-like pronouncements in the press of an X degree rise in temperature without a corresponding explanation of the models used, assumptions, estimates, variance, multicollinearity, etc. This is a problem with the press, not the scientists who tend to scrupulously document this sort of thing.  The problem is, no one will read a newspaper or magazine article that is incomprehensible to them.

You won't find a statement like this in the New York Times:

" An ensemble of temperature realizations preserves the correlation structure of different time steps. Hence decadal averages and their associated uncertainties can be calculated which are consistent with the covariance matrix of  observational uncertainty. "

 Models are only as good as the assumptions and data that go into them.

" To estimate the difference in total earth system heat uptake  between the last decades and the 1860-1879 reference period, we first derive annual total heat system content anomaly estimates for 1970-2009 by combining data based estimates for all the major earth system components: ocean, continent, ice, and atmosphere."

So, in a five-page explanation of a small subset of climate modeling, "Energy Budget Constraints", there are some 43 estimates made.  We find estimates of decade internal variability, estimates in total system heat uptake, estimates of upper ocean heat uptake, estimates of abyssal ocean heat uptake, estimates of continental heat uptake, ice melt estimates, estimates of atmospheric heat uptake, and so on and so forth.

These estimates don't necessarily make a model incorrect, but when output no longer matches observations they call it seriously into question.

We don't really need the models

We don't need a model to tell us that there will be a 2 degree rise in temperature to tell us that the less carbon dioxide, chlorinated fluorocarbons, or poly-chlorinated biphenyls we dump into the environment is a good thing.  Yet we must balance actions with consequences both environmental and economic and take a common sense approach.  Ideally what would make environmentally practical solutions the most appealing to consumers would be economic practicality.  

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