Sunday, September 07, 2008


For the first time since 1913, an entire calendar month has gone by without the observance of even one sunspot. See here.

Is this important?

It could matter to climate change, both theoretically and empirically. There is growing understanding that sunspots affect cloud formation on earth, and clouds are a big factor in climate modes -- indeed a factor that is not well understood. Better understanding of what determines cloud type and cover will help forecast climate. On the empirical side, "tests" of global warming at the aggregate temperature level essentially take the actual temperature record and adjust it for things like changes in solar radiation, volcanoes, atmospheric particulants, etc. What is left is presumed to be the effect of greenhouse gases. Summarizing very briefly, the "unexplained" temperature deviation from this process does match up reasonably well with the predictions of climate models (that is, the temperature is somewhat higher than it should be, after adjustment for non-GHG effects).

But note that, like so many things, this is a test of a joint hypothesis: that the adjustments are correct, and that the climate models are correct. If the adjustments are wrong, then what appears to be a correct climate model is actually wrong. Since solar activity (sunspots) has been high since 1940, and since that is theoretically and empirically related to warming, could it be that the adjustment to the temperature record for this effect has been too small? That would leave more of the observed warming to be explained by the models.

At any rate, if we are at a real low period for sunspots, and if that continues, we could be in for some cooling.

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