More clouds both drastically reduce energy input from the sun and simply slow release of what energy there is trapped in the lower troposphere, but the long term effect would be a fall in average temperature because of the
significantly reduced input power but the atmosphere's ability to cool is aided by air current circulation whereby the
warmer air rises above those low clouds and that infra - red is more easily re-emitted into space, whereby the low clouds now block that re-emission from hitting the
ground again to any significant degree.
IF back radiation existed and if there was some 333 w / m ^ 2 of back radiation beating down on the
ground, the black marble slaps should be
significantly warmer than the white marble slaps at night or on cloudy days.