A recent posting noted that because the Sun is at a solar minimum, the impact of GHG increases in the atmosphere have been less than would otherwise be anticipated. Now, a new report suggests that the Sun is entering an unanticipated, a potentially prolonged period of solar minimum. Some will take a "what, me worry?" attitude in light of this potential "blessing"; others will see it as an opportunity to take corrective action without suffering the full consequences for past activities.
To say that understanding what drives the so-called "eleven year" solar cycle has a ways to go is a statement of the obvious. What we do know is that a weaker solar cycle is accompanied by a slightly dimmer sun, which changes the average temperature on Earth. As noted in the prior post, solar cycles are a variable lot, with consistency not being their strong point. For example, the sun's brightness did not hit an all-time low during the past solar minimum, even though the sun was unusually quiet.
Nonetheless, the decline in solar brightness from 2002 to 2008 as solar activity dwindled probably countered the warming on Earth that would otherwise have occurred due to GHG increases over that period. When the Sun does pick up, we can expect that the impact of GHG emissions will be more severe than it now appears to be.
An interesting thesis on what drive's solar cycles can be found at http://www.nature.com/nature/journal/v471/n7336/full/nature09786.html. However, it should be noted that it is controversial, with critics noting that the speed of the meridional flow, a key factor in the theory, being exactly the opposite to that required by the thesis.