The “greenhouse effect” does not comment on how much of the sun’s radiation reaches the earth. It is a function of how much is re-radiated back into space from the earth. Exactly the way a glass greenhouse works.
The “greenhouse effect” as a physical phenomenon is well confirmed. Whether the earth is presently in the first stages of an increased greenhouse effect and whether that effect is being caused by humans is an entirely different question.
The total radiation does have an effect on the Greenhouse effect as well. Less total shortwave radiation means less longwave radiation from the surface being absorbed by Greenhouse gases, and a change in the greenhouse effect itself.
No Sherman, physicists have recently published numerous papers showing that the effect does not exist, and would violate several physical laws.
Its basically the same as all the leftist chicken little scares, like the old ozone depletion canard that has finally been completely demolished by the real data.
People love to be taken for a ride.