Changes in soil management can potentially increase the accumulation of soil organic carbon (SOC), thereby sequestering CO2 from the atmosphere. However, the amount of carbon sequestered in soils can be augmented or lessened due to changes in climate and atmospheric CO2 concentration. The purpose of this paper is to study the influence of climate and CO2 feedbacks on soil carbon sequestration using a terrestrial carbon cycle model. Model simulations consist of observed adoption rates of no-tillage practices on croplands in the U.S. and Canada between 1981--2000. Model results indicate potential sequestration rates between 0.4--0.6 MgC/ha/yr in the Midwestern U.S. with decreasing rates towards the western, dryer regions of the U.S. It is estimated here that changes in climate and CO2 between 1981--2000 could be responsible for an additional soil carbon sequestration of 42 Tg. This is 5% of the soil carbon estimated to be potentially sequestered as the result of conversion to no-tillage in the U.S. and Canada.