Rigorous estimates to support the Batchelor-Kraichnan-Leith theory of 2-D turbulence are made for time-dependent body forces acting in all length scales. The main estimate derived under several different assumptions on the smoothness of the force in in space and time, bounds the dissipation wavenumber from above and below in terms of a generalized Grashof number. That estimate is shown to be connected to the energy power low, the dissipation law, and the enstrophy cascade. This is joint work with Prof. Michael S. Jolly (IU) and Prof. Ciprian Foias (Texas A&M).