26 JAN 2026 (MON) 15:35 - 16:05

Comprehensive climate mitigation pathways under urbanization 

Mr LI Shijie 

( Supervisor: Prof Yuyu Zhou )

Abstract:

Climate change, driven by anthropogenic greenhouse gas emissions, is posing a threat to both the natural environment and human society. To mitigate climate change, an increasing number of countries have embarked on climate mitigation actions, making commitments such as energy transformation and net-zero emissions. As an active participant in these efforts, China has announced a reduction in economy-wide net greenhouse gas (GHG) emissions in its 2035 Nationally Determined Contribution (NDC) target, going beyond the scope of carbon dioxide alone. Such pledges require robust evidence on the effectiveness of mitigation actions. Scenario-based abatement quantification is therefore essential for delivering China’s 2035 NDC and long-term net-zero strategy.

Cities are key to addressing climate change. The large population and dense activities in cities directly lead to high energy consumption demands and GHG emissions, accounting for more than 60% of global anthropogenic GHGs. In addition, urbanization also indirectly increases GHG emissions by altering the local thermal environment. Specifically, the urban heat island effect, manifested as higher temperatures in cities compared to suburbs, amplifies cooling demand, driving additional building energy use, fossil-fuel combustion and attendant GHG emissions. More importantly, the process of urbanization is still intensifying. It is estimated that by 2050, 2.5 billion people will live in urban areas. Therefore, reducing urban energy consumption and GHG emissions through comprehensive climate actions has become key to climate mitigation.

In this study, we use the Global Change Analysis Model (GCAM), a comprehensive assessment model, to generate future climate mitigation pathways under multiple scenarios. To comprehend the critical role of cities in climate actions, we conduct research from two perspectives: local thermal environment and GHG emissions. First, we map the impact of the urban heat island effects on building energy consumption. We parameterize key processes in building cooling and heating (heating degree days and cooling degree days) to generate energy consumption and emissions in the building sector up to 2100. This research aids in understanding the potential additional energy consumption burden that urbanization may impose on climate actions. Second, we investigate future GHG emission pathways under varying climate goals. We calibrate historical GHG emissions and establish marginal abatement cost curves for future mitigation technologies. By setting GHG caps, we explore the potential and cost-effectiveness of future sector-level emission reductions. These two analyses together reveal the critical role of cities as energy consumption hotspots and emission hotspots in achieving cost-effective net-zero climate actions.