IPCC 2001:

> All reconstructions indicate that the direct effect of variations in solar forcing over the 20th century was about 20 to 25% of the change in forcing due to increases in the well-mixed greenhouse gases.

See more at:

* [RealClimate](http://www.realclimate.org/index.php/archives/2006/09/the-trouble-with-sunspots/comment-page-2/#sthash.kno2Hydq.dpuf)

hth