This is called radiative heat transfer. D.S.T. must be able to explain these observations, as well as the theories of the Photon Conspiracy explain them, in order to be a useful theory. Space around us is naturally dark.
Free darkness exists everywhere.
Every time a dark sucker operates, it pulls this intrinsic darkness out of all surfaces that are in an unobstructed path to the dark sucker. This intrinsic darkness is bound into the electrons of the surface material. The reason host materials get warmer as they release their intrinsic darkness is that there is a binding energy between darkness and its host material. Sucking out darkness releases that binding energy in the form of heat. The stronger the dark sucker and the duller the surface, the more darkness gets divested from the host surface and the hotter the surface becomes.