40 Years of Rising CO2 … 1940 to 1979. Officially CO2 measurements only started in the 50s, but I think one can extrapolate backwards.

CO2 didn’t have much effect. The Temperature trend over those 40 years was -0.026C per decade. About -0.1C for the 40 years.

http://www.woodfortrees.org/plot/hadcrut4gl/from:1940/to:1979/plot/hadcrut4gl/from:1940/to:1979/trend/plot/esrl-co2/from:1940/to:1979/offset:-300/plot/esrl-co2/from:1940/to:1979/offset:-300/trend

Lets take a look at the same graph without the CO2 part.

http://www.woodfortrees.org/plot/hadcrut4gl/from:1940/to:1979/plot/hadcrut4gl/from:1940/to:1979/trend