Earth’s Climate History based on climate proxy studies:

 Natural climate changes shown below.

 600 to 200 BC        =  Cold period          

 200BC to 600 AD   = “Roman Warming”               

 600 to 900              =   Cold period (aka “The Dark Ages”) 

 900 to 1300            =  “Medieval Warming”     

1300 to 1850           =  “Little Ice Age”     

1850 to date            =  “Modern Warming”     

Manmade CO2 could not have had any meaningful effect before 1940 ... and most likely had little effect after 1940.

Manmade CO2 began a rapid rise after 1940, but average temperatures did not rise for the next 36 years ( average temperatures actually declined from 1940 to 1976 ! )