Sun Changes and How it May Effect the Climate
The Active Cavity Radiometer Irradiance Monitor Satellite (AcrimSat) monitors the total amount of the sun's energy reaching Earth. It is this energy, called total solar irradiance, that creates the winds, heats the land and drives ocean currents. Some scientists theorize a significant fraction of Earth's warming may be solar in origin due to small increases in the sun's total energy output since the last century. By measuring incoming solar radiation, climatologists are can improve their predictions of climate change and global warming over the next century.
The Active Cavity Radiometer Irradiance Monitor was the first to clearly demonstrate that the total radiant energy from the sun was not a constant. However, the solar variability was so slight (0.1% of full scale) that continuous monitoring by state-of-the-art instrumentation was necessary.
It is theorized that as much as 25% of the anticipated global warming of the earth may be solar in origin. In addition, seemingly small (0.5%) changes in the output of the sun over a century or more may cause significant climatological changes on earth.
The Maunder minimum is the name given to a period of extreme solar inactivity that occurred between 1645 and 1710. Of particular interest is that this period of inactivity corresponds closely to one of the coldest periods of the so-called "Little Ice Age" in Europe, a time of long, cold winters that caused severe hardships in the pre-industrial revolution world.
This has led scientists to extensively study the possible influences of solar activity on terrestrial climate, as well as examine other stars for evidence of activity cycle behavior similar to the Sun's.
For reasons not yet understood, the solar cycle operated at a greatly reduced amplitude during that time. Evidence suggests it did not cease entirely, but the sunspot number—an index representing the total level of sunspot activity at a given time—during the late 1600s was reduced by a factor of 10-20 from its typical value during "normal" cycles. This perplexing aspect of the sunspot record is now known as the Maunder minimum.