Earth is a closed system, so the shade cloth on Earth would simply warm up and reradiate the absorbed energy as infrared. Reflective mylar would see a portion of the reflected sunlight (which would have warmed the atmosphere upon entry) trapped by the greenhouse effect.
Earth is is not even close to a closed system. There's a giant thermonuclear explosion factory in space that pumps insane amounts of energy into our system. If earth was a closed system it could not harbor life as entropy increased.
