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Abstract Increasing the albedo of urban surfaces, through strategies like white roof installations, has emerged as a promising approach for urban climate adaptation. Yet, modeling these strategies on a large scale is limited by the use of static urban surface albedo representations in the Earth system models. In this study, we developed a new transient urban surface albedo scheme in the Community Earth System Model and evaluated evolving adaptation strategies under varying urban surface albedo configurations. Our simulations model a gradual increase in the urban surface albedo of roofs, impervious roads, and walls from 2015 to 2099 under the SSP3‐7.0 scenario. Results highlight the cooling effects of roof albedo modifications, which reduce the annual‐mean canopy urban heat island intensity from 0.8°C in 2015 to 0.2°C by 2099. Compared to high‐density and medium‐density urban areas, higher albedo configurations are more effective in cooling environments within tall building districts. Additionally, urban surface albedo changes lead to changes in building energy consumption, where high albedo results in more indoor heating usage in urban areas located beyond 30°N and 25°S. This scheme offers potential applications like simulating natural albedo variations across urban surfaces and enables the inclusion of other urban parameters, such as surface emissivity. 

Abstract Urbanization changes Earth's climate by contributing to the buildup of atmospheric greenhouse gases and altering surface biophysical properties. In climate models, the greenhouse aspect is prescribed with urbanization and emission trajectories embedded in socioeconomic pathways (SSPs). However, the biophysical aspect is omitted because no models currently simulate spatially explicit urban land transition. Urban land is typically warmer than adjacent natural land due to a large urban‐versus‐natural land contrast in biophysical properties. The lack of biophysical representation of urbanization in climate models raises the possibility that model projection of future warming may be biased low, especially in areas with intense urban land expansion. Here, we conduct a global sensitivity study using a dynamic urban scheme in the Community Earth System Model to quantify the biophysical effect of urban land expansion under the SSP5‐RCP8.5 scenario. Constant urban radiative, thermal, and morphological properties are used. We find that the biophysical effect depends on land aridity. In climate zones where surface evaporation is water‐limited, the biophysical effect causes a significant increase in air temperature (0.28 ± 0.19 K; mean ± one standard deviation of nine ensemble pairs;p < 0.01) in areas where urban expansion exceeds 5% by 2070. The majority of this warming signal is attributed to an indirect effect associated with atmospheric and land feedback, with the direct effect of land replacement playing a minor role. These atmospheric feedback processes, including solar brightening, soil drying, and stomatal closure, act to enhance the warming initiated by surface property changes of urban land replacement.