It is apparently correct that reduced sunspot activity is correlated with reduced solar irradiance. The Maunder Minimum during the latter half of the 17th century did lead to what was known as the Little Ice Age. However, there is also strong evidence that the rise in greenhouse gases has become the dominant agent affecting global temperature as can be seen in this graph:
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| Courtesy of http://lasp.colorado.edu/images/science/solar_infl/Surface-Temp-w-paleo.jpg |
The golden line with diamonds is the measured or reconstructed total solar irradiance. The solid blue line is the reconstructed global surface temperature. The dashed blue line is the measured temperature in the Northern Hemisphere (NH). One can see that solar irradiance and the reconstructed global temperature follow one another fairly closely. The measured NH temperature also tracks total solar irradiance until the last 40 years when it starts to sharply diverge. This graph shows the recent data at higher resolution:
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| Courtesy of http://www.skepticalscience.com/pics/Solar_vs_Temp_basic.gif |
The divergence is even more clear here since total solar irradiance has been declining as global mean temperature has been rising. One can see on the first chart that there is a very close correlation between solar irradiance and temperature. The effect of the three major volcanic eruptions that are noted caused an immediate drop in solar irradiance and a corresponding drop in temperature. So the implication of the second chart is that there must be at least one other factor that is influencing global mean temperature than solar irradiance and that this factor is overriding the drop in solar irradiance.
If we are indeed entering another Maunder Minimum of solar activity, it at most will give us a temporary reprieve and slow the rise in temperature. It will not cause a long term (i.e., greater than 100 years) cooling and it will not reduce the importance of reducing anthropogenic greenhouse gases.
