Carbon emission scenarios of China's construction industry using a system dynamics methodology - Based on life cycle thinking

China is currently one of the world's major energy consumers and CO2 emitters. To save energy, and reduce consumption and carbon emissions, China proposed (at the 2020 United Nations General Assembly and Climate Summit) the introduction of stronger policies and measures for CO2 emissions to peak in 2030 and to achieve carbon neutrality by 2060. The construction industry is a major contributor to China's carbon emissions, thus research on energy saving and carbon reduction in this industry is essential. The construction industry is characterized by complex upstream and downstream industrial chains, with different energy consumption at each stage, and a long overall life cycle. We used life-cycle thinking (LCT) to analyze the carbon emissions of the whole life cycle of the construction industry and built a model by using a system dynamics method, which analyzes the carbon emission process of the construction industry at different stages. Combined with the planning and policies implemented by the construction-related departments, we identified the main indicators of policy regulation and control. We used sensitivity analysis to examine the impacts of factors of regulation and control. We also adjusted key indicators and set up different scenarios to simulate the carbon emissions based on the effort to achieve "peak carbon." The results show that the carbon emissions of the construction industry will be reduced by 2060, achieving the goals of "peak carbon" and "carbon neutrality." Although the construction and operation stages individually can achieve peak carbon by 2030, the whole process of the construction industry will reach peak carbon by 2045, 2038, or 2036, depending on specific aspects of the scenario considered. However, the indicators, such as the green building ratio can realize carbon emission reduction at building operation stage for 4%-6%, but cause greater carbon emission for 5%-7% at construction material production and transportation stage-a phenomenon called "policy island." Therefore, the coupling of policies should be a key concern in policy formulation and implementation.