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The Maunder Minimum (1645-1715) was a period of time when few sunspots were observed for nearly 70 years, despite careful telescopic studies by multiple observers. This time also corresponded to the European 'Little Ice Age' which brought severe, cold winters to otherwise moderate climates. Scientists now believe that there is a direct connection between sunspot activity and the heating of the atmosphere, which can cause long-term climate changes.
The output of the Sun can vary by up to two tenths of a percent over the 11-year solar cycle. Temporary decreases of up to one-half percent have been observed. Atmospheric scientists say that this variation is significant and that it can modify climate over time. Plant growth has been shown to vary over the 11-year sunspot and 22-year magnetic cycles of the Sun, as evidenced in tree-ring records.
During solar proton events, many more energetic particles reach Earth's middle atmosphere. There they cause molecular ionization, creating chemicals that destroy atmospheric ozone and allow increased amounts of harmful solar ultraviolet radiation to reach Earth's surface. A solar proton event in 1982 resulted in a temporary 70% decrease in ozone densities.
During a large solar storm, a portion of the upper stratosphere in the Polar Regions can lose up to 20 percent of its ozone and cool as much as 3°C, an effect that can last for several weeks. [More]
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