30's and 40's dust bowl I'd guess. Temps were warmer then than today. That busts the entire thing where US temps are concerned. 1950's were cooler so the charts look more convincing. When temps from the 1930's are included in charts we don't see any warming. Who'd a thunk? Check this out, 50 Non-hockey stick graphs. It depends on who you believe and who you don't believe. http://notrickszone.com/2016/09/27/...n-global-warming-claims/#sthash.VuvhYvBA.dpbs Science does not support the assumption CO2 is increasing global surface temps.