Most modelling studies of this period do not treat ice sheet extent and elevation or CO2 concentration prognostically, but specify them as boundary conditions. (ipcc.ch)
Terrestrial glacial geologists (such as ourselves) can gain information of past glacial behaviour from mapping and dating former ice sheet extents, and determining the rates at which they receded and thinned, [e.g., 16, 17 - 19]. (antarcticglaciers.org)
The uncertainty in the regions affected by high - end climate change during DJF (the Arctic) is mostly due to differences in modelled temperature increases, which are caused by biases in simulated ice sheet extent and snow cover. (rsta.royalsocietypublishing.org)