The replacement of natural lands with urban structures has multiple environmental consequences, yet little is known about the magnitude and extent of albedo-induced warming contributions from urbanization at the global scale in the past and future. Here, we apply an empirical approach to quantify the climate effects of past urbanization and future urbanization projected under different shared socioeconomic pathways (SSPs). We find an albedo-induced warming effect of urbanization for both the past and the projected futures under three illustrative scenarios. The albedo decease from urbanization in 2018 relative to 2001 has yielded a 100-year average annual global warming of 0.00014 [0.00008, 0.00021] °C. Without proper mitigation, future urbanization in 2050 relative to 2018 and that in 2100 relative to 2018 under the intermediate emission scenario (SSP2-4.5) would yield a 100-year average warming effect of 0.00107 [0.00057,0.00179] °C and 0.00152 [0.00078,0.00259] °C, respectively, through altering the Earth’s albedo.

Despite the advantages of polycentric structure and its rich literature drawn from cities in industialized countries, little attention has been paid to the study of polycentric urban development in developing countries based on land-use information. With Hangzhou used as a case study, the authors investigate polycentric urban development through an analysis of directions of urban expansion, urban–rural gradients, and growth types. The multidisciplinary methodology employed, based on theories and methods in remote sensing, geographic information systems, and landscape ecology, has been proved to be useful in the morphological study of polycentric urban development. It was found that Hangzhou has expanded in different directions at various speeds, shifting to a polycentric urban pattern through radial expansion. Along the main transportation corridors, the values of the mean patch sizes of urban patches displayed multiple peaks, and the landscape-shape index maintained a horizontal trend in urban fringes, reflecting the formation of polycentricity. Further, as edge growth and spontaneous growth accounted for 40%–50% and 30–40% of urban growth, respectively, and infill growth was responsible for only a small proportion of urban growth, it is suggested that dispersed urban patches have been increasingly agglomerated into big ones, especially along road corridors. Hangzhou's polycentric urban development was shaped both by the planning efforts of the government and by market forces. The municipal government guided the polycentric development through drafting and revising master plans, annexing nearby districts, and establishing development zones. Nevertheless, market forces played an increasingly important role in Hangzhou's polycentric development through the implementation of an urban land market, the inflow of migrant workers, and the relocation of industries.