Synergistic reductions of CO₂ and aerosols: Navigating mid-term warming risks for 2 ℃ climate futures

Achieving the 2 ℃ climate target requires the coordination of strategies for greenhouse gases (GHGs) and air pollutants mitigation, yet their complex interactions remain insufficiently explored. BCC-ESM1 Earth system model is employed to compare global climate responses under the novel SSP2-com scenario, in which both GHGs and aerosols undergo reduction, with that under the SSP2-4.5 scenario. Moreover, the relative contributions of carbon dioxide (CO₂), sulfur dioxide (SO₂), and black carbon (BC) to future temperature increases are analyzed. Results reveal that compared with the SSP2-4.5 scenario, the SSP2-com scenario can stabilize the end-21st-century temperature rise well below 2 ℃, primarily driven by the reduction of anthropogenic CO₂ emissions. A mid-term warming rebound between 2061 and 2080 is observed due to reduced aerosol cooling. SO₂ reductions result in a weakening aerosol-induced radiative forcing, driving regional warming asymmetries―particularly in northern high latitudes (up to +1.5 ℃ in winter). Compared to CO₂-only mitigation, experiments involving SO₂ reductions also exhibit stronger global precipitation increases, suggesting an acceleration of the hydrological cycle under lower aerosol loading. Energy budget analysis further indicates that SO₂ mitigation results in an increase in net shortwave radiation at the top of the atmosphere by approximately 0.23 W/m² during the mid-term (2061―2080), and consequently leads to an accumulated surface energy gain of about 0.15 W/m². These findings highlight a key trade-off: aerosol mitigation may induce mid-term warming, but remains essential for achieving air quality and climate goals. This work underscores the necessity of balancing mid-term climate―air quality trade-offs with long-term decarbonization, offering actionable insights for policymakers to design integrated pathways align with the Paris Agreement.