Interesting article on sun spots, how they work and the historical impact on climate.
Today’s climate change consensus is that man-made greenhouse gases are warming the world and that we must act to curb them to reduce the projected temperature increase estimated at probably between 1.8C and 4.0C by the century’s end. But throughout the 20th century, solar cycles had been increasing in strength. Almost everyone agrees that throughout most of the last century the solar influence was significant. Studies show that by the end of the 20th century the Sun’s activity may have been at its highest for more than 8,000 years. Other solar parameters have been changing as well, such as the magnetic field the Sun sheds, which has almost doubled in the past century. But then things turned. In only the past decade or so the Sun has started a decline in activity, and the lateness of cycle 24 is an indicator. [From Ray of hope: Can the sun save us from global warming? - Independent Online Edition > Science & Tech]