In order to mitigate effects of climate change, governing entities need to limit carbon dioxide (CO2) in the atmosphere to a concentration yet to be determined. To assist policymakers, this experiment tested selected sensitivities of the land and ocean sinks to a proposed CO2 stabilization scenario of 600 parts per million by 2100. Sensitivities evaluated were the effect of CO2 fertilization on vegetation, the effect of long-lived forests vs. short-lived steppes, and the effect of various ocean circulation rates. All simulations were done with Tethys, a four-box earth-systems model consisting of a vegetation-soil reservoir, ocean, atmosphere, and emissions source. Results are generated through a series of equations written in IDL code, parameterized to simulate key processes in the climate-carbon cycle. Results generated in response to ocean and land sink behavior included peak allowable emissions, CO2 uptake rates in a reservoir, and the maximum amount of allowable emissions to maintain concentrations at 600 ppm. Tethys predicted that the rate of carbon uptake in the oceans will decrease with an increase in circulation time, and that the vegetation sink will cease to exist soon after atmospheric CO2 is stabilized. Simulations suggest that grasslands will absorb more CO2 than forests, a result that indicates a flaw in the model. The carbon cycle sensitivities tested in this experiment determine how much humans can emit and how quickly emissions need to be reduced to meet stabilization goals. Future sink behavior should be incorporated into any plan that seeks to stabilize atmospheric CO2.