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Saturday, December 22, 2012

Meaningful Estimation of the Global Climate Trend

Arguably, one of the most contentious issues in recent decades has been the so-called "global warming" controversy. It seems like everyone and his uncle has an opinion about it, albeit virtually no one has a clear understanding of what, specifically, global warming actually means. Before you can debate such an issue, you have to define its meaning unambiguously. This is what I mean to do in this post.

It should be clear from the start that any global trend on Earth must be a time dependent function that has been averaged over the surface of the globe, as well as averaged over any inherent cyclical-time component. If this is not clear, consider the absurdity of claiming the existence of a global-warming trend by referring to the daily temperatures recorded between January and July in New York City!

In order to eliminate from the consideration of long-term global trends those cyclical daily and seasonal variations, our database must comprise information that has been averaged over the Earth's daily spin about its polar axis and its annual orbit about the sun. This involves the averaging of available temperature measurements both globally with respect to circles of latitude and annually with respect to time. Moreover, the order of such surface and time averaging may be significant, but I leave such details to reputable climatologists, assuming we can find them.

Once such a corpus of time- and surface-averaged global temperatures has been compiled and assembled, we can plot the temperature as a function of calendar year. The resulting best-fit temperature versus time line will undoubtedly be a curve with numerous multiyear fluctuations. At such a point of analysis, we would have to consider what primary causes could account for such fluctuations. One obvious potential cause, given that our sun is the principal source of the Earth's energy, is the known 11-year cycles of maximum/minimum sun spots. There may be others. Such influences would have to be discounted, too, before any long-term trends could be revealed by our compiled data. As a consequence, I think that trends of less than about a decade's duration could not be meaningful.

I think it is becoming obvious how complex this long term global concept really is. At the very least, I would hazard a guess that even brilliant minds such as Al Gore, the putative inventor of the internet, careful observer of endangered polar bears, and failed Presidential candidate, might not know squat about whether or not we are in an extended trend of global warming, especially one that supersedes multi-millennial-duration cycles of the recurring ice-ages. Nor can we even begin to consider what part, if at all, of any possible lasting trend could be attributable to humanity's activities.

Warm regards to one and all.

Post 1,938 Meaningful Estimation of the Global Climate Trend

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