Sunspots and Climate   Though the connection between sunspot activity and the earth's climate is still being debated, phenomena like the "Little Ice Age" that occurred during the Maunder Minimum from 1645-1715, seem to show evidence of some connection. Sunspots mean the sun is brighter? Even though sunspots are darker, cooler regions on the face of the sun, periods of high sunspot activity are associated with a slight increase in the total energy output of the sun. Dark sunspot areas are surrounded by areas of increased brightness, known as plages. Some parts of the solar spectrum, especially ultraviolet, increase a great deal during sunspot activity. Even though ultraviolet radiation makes very little contribution to the total energy that comes from the sun, changes in this type of radiation can have a large effect on the earth's atmosphere, especially in the chemistry of the outer atmosphere, like the production of ozone and sulfuric acid. Researchers still uncertain According to George Fisher, "It's controversial whether the solar cycle has an effect on the earth's climate. One thing that is known for sure is that solar activity, which is what we call the general feature of having magnetic fields on the sun, changes the sun's luminosity--that is, how much energy is coming out of the sun--on the level of a few tenths of a percent. That could change the earth's climate in this cyclical way, but it's controversial." Complex systems The controversy is due to the complexity of the earth/atmosphere system. It is difficult to disentangle the many factors that contribute to climate change. For instance, are the effects of global warming or ozone depletion more influenced by changes in solar activity? Or possibly by human activity? Dearborn is also cautious about ascribing climate effects to sunspot cycles: "People have speculated, but I don't think the connection is absolute yet....there is some speculation that sunspots result in climate effects, but that's a very, very hard area, and one that requires much more research before we can be certain of climate effects." Who will find out? Currently, there are scientists whose research with this kind of data makes them believe that the Sun has the strongest influence on all climatic changes here on earth--that known climate changes can be shown to correlate to changes in solar activity. Others believe that human activities, such as burning fossil fuels or clear-cutting forests, may also be important, or even more powerful. Everyone agrees that more research into Sun-Earth connection science needs to be done. How does the extra ultraviolet light associated with sunspots affect the atmosphere? Do geomagnetic storms produce chemical reactions the atmosphere? How could you compare the effects of human activities and changes in the sun over time? You might want to think about what type of investigation you'd want to do next. What question would you try to answer? ©Copyright 2001 Regents of the University of California.