The mid-20th century "hiatus" in GMST increase was not the result of a decrease in solar output. Where do you get this stuff? In reality, TSI was just reaching the Modern Maximum at about that time. The flat-lining from 1945 (not the '30s) to 1975 was a result of increased albedo due to air pollution and combined negative phases of the PDO and AMO.

Again, solar output is very stable.