| State-of-the-art general circulation models (GCMs) are an important and comprehensive tool used to simulate past climate, and also to make plausible projections of future climate. GCMs incorporate a host of physical forcing parameterizations, including: solar radiation, volcanic activity, greenhouse gas concentrations, vegetation, and snow cover.; There are three 1000-year simulations from the GCM ECHO-g used in this thesis; 2 of which are forced runs, differing only in initial conditions. The third is a control run, used to assess model variability, in which greenhouse gas concentrations are held at present-day values.; This thesis is divided into two principal explorations using ECHO-g. The first is a North American reconstruction of the climate of the last 1000 years from borehole data and comparison with ECHO-g data. Boreholes in North America were aver aged together to form ensembles, representing 8 distinct geographic regions. In all 8 regions, the forcing runs, from ECHO-g are in better agreement with borehole thermal profiles than with the control run, illustrating that boreholes are sensitive to the external forcing factors incorporated in ECHO-g. Not only do ECHO-g simulations demonstrate better agreement with borehole data when considering variable external forcing factors, ECHO-g also appears to adequately describe long-term climatic trends at a regional scale.; The second experiment looks in detail at the effect that placement of the bottom boundary has on GCMs' potential to store energy in the subsurface. Results show that the amount of energy may be miscalculated by as much as 1.0 x 1023 Joules over the course of a 110-year simulation with a bottom boundary of 10m, the deepest of present-day GCMs. This is more than an order of magnitude greater than the heat absorbed by both the global continental surfaces and the atmosphere in the last 50 years.; The results of this work can serve as a guideline for future GCM construction, as well as comparison of proxy data and simulations for the purposes of paleclimatic reconstruction and future climate projection. |
