Cook stoves that produce biochar as well as heat for cooking could help mitigate indoor air pollution from cooking fires and could enhance local soils, while their potential reductions in carbon (C) emissions and increases in soil C sequestration could offer access to C market financing. We use system dynamics modeling to (i) investigate the climate change impact of prototype and refined biochar-producing pyrolytic cook stoves and improved combustion cook stoves in comparison to conventional cook stoves; (ii) assess the relative sensitivity of the stoves' climate change impacts to key parameters; and (iii) quantify the effects of different climate change impact accounting decisions. Simulated reductions in mean greenhouse gas (GHG) impact from a traditional, 3-stone cook stove baseline are 3.50 tCO(2)e/household/year for the improved combustion stove and 3.69-4.33 tCO(2)e/household/year for the pyrolytic stoves, of which biochar directly accounts for 26-42%. The magnitude of these reductions is about 2-5 times more sensitive to baseline wood fuel use and the fraction of nonrenewable biomass (fNRB) of off-farm wood that is used as fuel than to soil fertility improvement or stability of biochar. Improved cookstoves with higher wood demand are less sensitive to changes in baseline fuel use and rely on biochar for a greater proportion of their reductions.