The largest effect on global warming by far was caused by the loss of ozone from CFC destruction that allowed the stratosphere to cool off by 1.3 degree C while the troposphere warmed due to more UV light hitting it. One can essentially account for the total warming (0.40 degree C)that was seen in 2000 from ozone loss (+0.315C) plus the natural increase from the 11 year Solar Irradiance cycle (+0.084C). CO2 is clearly not the cause of warming, warming always precedes an increase in CO2. You can read my paper based on the research completed at: