curvature. This is a genuinly relativistic property. It was argued in [@buchert:darkenergy] that it is this possibility which is needed for an explanation of Dark Energy through backreaction today, provided the initial conditions are appropriate.

The scaling solutions (\[backreactionparameter\]) can be employed to represent generic features of backreaction– or curvature–dominated cosmologies (while density fluctuations must not be large). Such cosmologies may significantly deviate from a standard Friedmann cosmology with regard to the temporal evolution of their parameters. We note that, even if deviations in the volume scale factor $a_{{\cal D}}$ at a final time may not be large, deviations in in its history, i.e. its time–derivatives, in particular its second time–derivative related to the cosmological parameters, may be large (this insight is a result of a detailed analysis in Newtonian cosmology [@bks]).

Let us make a general remark concerning the solution subspace of the scaling solutions given above. We appreciate that the polynomial nature of (\[prescription\]), together with the form of the integrability condition (\[integrability\]), implies that any linear combination of these solutions provides a new solution. In particular, one can always add a constant curvature term to a particular solution. We also infer that only the case $r=0$ ($n=-2$) 