The climate system properties influence the asymmetry in global surface air temperature evolution under changes in carbon dioxide (CO2) concentration, but it remains unclear which properties contribute relatively more significantly. Due to the insufficient samples from the Coupled Model Intercomparison Project phase 6 (CMIP6) experiments, present study utilized output of 45 CMIP6 models and constructed 391 sets of experiments using a two-layer energy balance model that is both rapid and reproducible. The experimental results demonstrate that Equilibrium Climate Sensitivity (ECS), ocean heat capacity, and coefficient of vertical heat exchange in the ocean play primary roles in the asymmetry of Global Surface Air Temperature (GSAT) evolution under fixed CO₂ concentration rise and fall. They mainly achieve this by altering the cooling rate after the peak of GSAT during the CO₂ concentration decline period. Therefore, a deeper understanding of the climate system’s ECS, ocean heat capacity, and coefficient of vertical heat exchange in the ocean may facilitate a more scientifically realistic achievement of the goals of the Paris Agreement.