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Abstract
Atmospheric CO2 concentrations have risen to almost 1.5x preindustrial values and could increase to nearly 3.9x preindustrial values by the end of the century, leading to innumerable effects on the climate. These impacts are largely associated with the enhanced greenhouse effect, but recent work also highlights plant physiological responses which can strongly influence water cycling. This study explores these plant responses to 2x preindustrial CO2 concentrations by analyzing simulations from the Community Earth System Model versions 1 and 2. We find that leaf area plays an important role in hydrological cycle changes (e.g., precipitation, evapotranspiration, and runoff) through its influence on canopy evaporation which can offset transpiration decreases from reduced stomatal conductance. Compared to Advanced Very High Resolution Radiometer-derived leaf area, CESM2 better captures near present-day magnitudes but potentially overestimates leaf area-CO2 sensitivity, highlighting the need to reduce plant-related biases for future climate research.