A paper recently published in the journal Weather finds that global summer average sunshine [solar short-wave radiation that reaches Earth's surface] dimmed during the period 1958-1983 [prompting an ice age scare], but markedly increased from 1985-2010. The increase in summer average sunshine between those two periods is 6 Watts per square meter, which dwarfs the alleged effects of CO2 by more than 5 times. [Alleged CO2 effect from 1958-2010 was calculated using the IPCC formula 5.35*ln(389.78/315) = 1.14 Watts per square meter]. At one measurement site [De Bilt], summer sunshine increased from 1985-2010 by 15 Watts per square meter, more than 23 times the IPCC alleged forcing from CO2 during the same timeframe [5.35*ln(389.78/346.04) = 0.64 Watts per square meter].
The paper states the increase in sunshine reaching the Earth's surface is due to a decrease in aerosols including clouds, which are influenced by both anthropogenic and natural factors, and possibly changes in solar activity.
Full paper here