Tuesday, June 14, 2011

Are sunspots going away?

A press conference today announced three research projects that suggest that our sun's familiar sunspot cycle might be heading toward a major change or even a pause.  You can read good summaries of the findings in this post from space.com and this article on Universe Today; I'll wait while you do that and then give you my first thoughts on this news.

Done reading?  Good.  First, let me state that I am not a solar physicist, and I do not claim to be an authority on the research being done.  So feel free to take my opinions with a grain of salt.

I am skeptical that the prediction of a pause in the solar cycle is indeed coming.  This is for many reasons, including:
My personal takeaway: predicting sunspots involves really complex physics that we don't fully understand (and that may not be predictable!), and I will remain highly dubious of any model until someone gets it right a few times in a row.

Also, the new studies extrapolate currently-observed trends into the future. Extrapolation is always dangerous. Will the trends hold?  Maybe.  Maybe not.  Past performance is no guarantee of future results.  When we don't really understand the physical process behind the trends, extrapolating is fraught with peril.

Don't take this to mean that I think these predictions are worthless.  Quite the opposite; they are crucial.  Bold predictions allow us to test new ideas.  If these scientists are correct and the sunspot cycle comes to a temporary halt, then perhaps we've experienced a breakthrough in our understanding of how the sun's magnetic field works.  And if the predictions are wrong, then we will know that these ideas were not correct (or misinterpreted; there's a slight difference).

However, if these predictions do hold up and the sunspot cycle pauses for some extended time, we do have some idea of what could happen.  In the late 1600s, sunspots all but disappeared for nearly 50 years, in what we now call the Maunder Minimum.  During the Maunder Minimum, global temperatures cooled by about 1 degree Celcius (2 degrees Fahrenheit). 

Should this happen again, we would expect to see a temporary pause in global warming.  Most climate predictions expect a 1 to 2 degree Celcius rise in global temperatures over the next 50 years due to the greenhouse effect.  A new Maunder Minimum on the sun might almost exactly cancel that out, and so average global yearly temperatures might stay about the same for the next half century. (Year-to-year fluctuations and local fluctuations would certainly remain!) 

This would be a mixed blessing.  We might get some breathing room to reduce greenhouse gases while avoiding some of the worst effects of global warming, but this would probably also lessen an already weak societal desire to do something.  And, if over the next half century, we did not reduce greenhouse gas concentrations, when the solar cycle restarted that few degrees of warming would occur in just a few years instead of over several decades, which could be an economic, ecological, and societal disaster.

So, in short, don't panic.  I am dubious that these predictions of a pause or major change to the sunspot cycle will come to pass.  Even if they do, sunspot cycle pauses have happened in the past and we all came through just fine, so there's no reason to worry, let alone panic.  Making these predictions is important to the advancement of science, and even if the predictions are wrong, we will learn something about how the sun works.

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