Spots Before My Eyes
We donít normally think much about the sun. It rises and sets every day and we pretty much take it for granted unless itís really hot or really cold. There is increasing evidence that maybe we should be paying a lot more attention to Old Sol than we have been. Sunspots, for instance, have been linked to changes in the climate.
Scientists have noted the timing of cold and warm spells in relation to the amount of sunspot activity for a long time and have come to realize sunspot minimums are associated with cold spells. Who hasnít heard of the connection between the Maunder Minimum and the Little Ice Age? Thereís even considerable debate today that sunspots may be the real culprits behind global warming instead of greenhouse gases. So whatís going on here?
Okay, letís talk sun science for a minute. Obviously, the sun is our local star and it radiates energy at a black body temperature of about 5,700 degrees Kelvin (never mind trying to convert to something more recognizable; itís HOT). The sunís energy output varies over time and this variance is reflected in sunspots and solar flares. The more activity there is, the hotter the sun is and the more sunspot and solar flares activity goes on. The less activity, the fewer sunspots and solar flares there are.
Sunspots are relatively dark, sharply defined regions on the solar disc. These regions are relatively cool spots that range in size from an average of 3,700 km across to 245,000 km across. They generally occur in groups of two or more but also occur singly. Sunspots are gigantic magnetic fields that block the flow of internal gases to the surface. Solar flares are solar explosions that spurt up from the chromosphere above sunspots. They are unpredictable and can persist for a few seconds to a few hours.
Here is where it gets interesting. There is a regular cycle of maximum and minimum activity. In the short term, there is an 11-year cycle between a solar maximum and minimum. In longer terms, the sun reverses its magnetic polarity with every solar maximum, which occurs every 22 years. Just to aggravate the situation, there is also a Gleissberg cycle that lasts 90-120 years.
This is a cycle of increasing and decreasing sunspot activity that modulates the 11-year short-term cycle to have a net effect of intensifying long-term warming or cooling. Researchers have matched Gleissberg minimas to the years 1670 (the Maunder Minimum, 1645-1715), 1810, and 1985. All three periods coincided with cool Northern Hemisphere climates. The Gleissberg and Maunder Minimums coincided with the coldest part of the Little Ice Age, a 70-year period when sunspot activity was virtually absent.
That does not mean there is a huge difference between maximum and minimum energy radiation. The solar constant (the measure of its output) varies by only plus or minus 0.22 percent and not all of that effects the climate. Still, the variation in average temperature ranges up to 2.6 Celsius degrees, which can really pack a wallop climatically speaking. Climatic warm periods furthered Viking exploration westward and cool periods caused famine and thousands of deaths in western Europe in the late 1600s. There is documented archeological evidence around the world of the rise and fall of whole civilizations that can be traced to a change in the climate.
So what does this mean to us? For one thing, it might go a long way to explaining the observed pattern of global warming that has been observed the last decades of the 20th century. A new, and therefore somewhat controversial theory suggest that sunspots have a great deal more to do with warming trend we are currently experiencing than the greenhouse gases industry puts into the atmosphere.
Researchers have projected that roughly 78 percent of the rise in temperature between 1885 and 1987 can be attributed to a solar energy radiation increase. Needless to say, there is tremendous argument in the scientific community both for and against this theory but fossil and historical evidence tend to support it rather well.
Another reason to care about sunspots is a prediction. If scientists are correct about the impact of sunspots, we are heading for a new Little Ice Age around the year 2030. Thatís not very long from now and we can use this new knowledge to prepare for a new, colder climate just the way we learned to prepare for El NiŮo events. Some places will be colder and drier, some colder and wetter, other places just the opposite. Understanding what happens where can make survival of our global civilization dependent more on intelligence than on luck. Sunspots; thereís more to them than meets the eye!
Written by Melody L. Higdon, 14 WS/DOPA