Projecting the future fine-resolution carbon dioxide emissions under the shared socioeconomic pathways for carbon peak evaluation

Projecting future urban CO2 emissions is of paramount importance in comprehending and addressing climate change, as well as evaluating the impact of various policies on future greenhouse gas emissions. While previous studies on projecting CO2 emissions have primarily focused on large administrative scales, fine-resolution mapping of CO2 emissions is also vital for identifying CO2 emission hotspots and delineating emission reduction responsibilities. In this paper, we projected the future CO2 distribution at a fine-resolution (1 km) under the shared socioeconomic pathways (SSPs) scenario framework, based on which we assessed the peak time, peak volume, spatial distribution, and CO2 emission intensity (emissions per unit building volume) for cities in the Pearl River Delta (PRD) region. We first simulated the future three-dimensional (3D) spatial patterns of cities by using the FLUS-3D model, and then projected fine-resolution CO2 emissions by combining the 3D information and socioeconomic factors. Results show that the total CO2 emissions in the PRD region will reach 180-345 million tons (Mt) by 2030, and 67% of cities in the PRD region will peak CO2 emissions before 2030 under all five SSP scenarios. Three cities (Jiangmen, Zhongshan and Foshan) will witness a continual rise in CO2 emissions after 2030 under the SSP5 scenario. Additionally, we found that the time (2010) to reach maximum CO2 emission intensity of different urban functional types precedes the peak time (2010-2030) of city-level CO2 emissions. This suggests that the escalation in CO2 emissions since 2010 will be primarily driven by urban expansion and population growth, rather than an increase in the CO2 emission intensity of buildings. These findings provide extensive knowledge for future spatial distribution of CO2 emissions and contribute to the construction of lowcarbon cities.