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.