ontributed to 
                the tendency before, and which after, this call

             Units of dt_xi are [xi]/s where [xi] are units of xi

         dt_tr -- real, dimension(:,:,:,:)
             Tracer tendency (see above)  size(dt_tr,4) = number of tracers
	     
     output: 
         dissipative_heat -- real, dimension(:,:,:)
             shape must conform to that of u, v, t, etc
	     units: deg_K/s 
	     
	     (computed when do_conserve_energy = .true.
	      and added to dt_t before tempera