If you have never heard of global dimming, this (part 1, part 2) should bring you up to speed. The latest news is that, according to the recent studies, the trend of reduction in solar radiation observed from 1961 to 1990 could be reversing. Things are getting brighter. One of the possible consequences is that "the 'dimming' may have lead to a slight negative radiative forcing, somewhat masking the global warming signal; the reversal [...] may have removed this masking effect and lead to the signal being more obvious in the 1990s." Could we possibly have underestimated global warming? But lets not go too fast. RealClimate warns us to be cautious with this new data until it's studied more.