Terrestrial plants play a role in regulating carbon and water fluxes by dynamically responding to the environment. Plants are hypothesized to adjust their stomatal opening to maximize the rate of photosynthesis while minimizing water loss from transpiration. However, the universality of this behavior and the responsiveness of stomata to changing environmental conditions is poorly constrained by observations. Changes in stomatal conductance drive changes in both carbon and water fluxes and can alter land surface properties, which can affect climate factors like temperature, water availability and the risk of extreme climate events like droughts, heatwaves, and floods. In global-scale models, stomatal conductance is often represented by an equation that includes an empirically fit stomatal slope parameter. The field observational range of the slope parameter within and across plant types is large, which implies a large variance of plant responses on the Earth system. However, typically a single value is used to represent each plant type in global-scale models, which has implications on the Earth system and our climate projections. We conducted experiments in an Earth system model in which we varied the slope parameter, in our case through the Medlyn stomatal conductance model, for each plant type to evaluate its influences on the Earth system. Here we focus on the differential response of photosynthesis under rising CO₂ with and without the presence of atmospheric feedbacks as well as interactions with dynamic feedbacks of leaf area. We find that the inclusion of a dynamic atmosphere enables the climate to respond differently to a change in the slope parameter and that photosynthetic response is sensitive to temperature changes depending on region. This has implications that the Earth system response to choice of the slope parameter depends on which aspects of the Earth system are allowed to dynamically respond.