To address the cumulative effect, this is the same as the sun. There is a balance of heat radiant on the earth and then earth radiates to space. The amount coming to earth is set by the distance to the sun and how reflective the earth is. The amount leaving the earth is set by its temperature (blackbody) and how much is trapped by various mechanisms (reflecting back to the earth again). Therefore, one way to think about it is the excess energy on top of the ones accounted for, like the sun.