Revisiting BCC-SESM parameters sensitivity with BCC-CSM1.1 co₂-concentration-driven simulations

Based on the results of the complex climate model BCC-CSM, the Beijing Climate Center Simple Earth System Model (BCC-SESM) was developed for climate system simulations in Integrated Assessment Models (IAMs). The first version of the BCC-SESM model was based on a high-emissions scenario (ESMRCP8.5) and tends to overestimate the temperatures in low and medium emissions scenarios. To address this problem, this study uses three CO₂-concentration-driven simulations under different RCP scenarios of complex climate models to evaluate parameters sensitivity and their impacts on projection efficacy. The results show that the new version of the BCC-SESM (denoted as BCC-SESM1.1) model based on a medium-emissions scenario experiment (RCP4.5) is more suitable for temperature projections for various climate scenarios. It can well reproduce the original value of complex climate model. At the same time, it also has high predictive efficacies for medium (RCP4.5) and low (RCP2.6) emissions scenarios, although it tends to underestimate for high emissions scenario (RCP8.5). The sensitivity tests for different RCP scenarios shows that the BCC-SESM1.1 has higher efficacy in projections of future climate change than those model versions based on the other scenarios. The projection deviations for the global average temperature by the BCC-SESM1.1 (<2%) are better than the previous BCC-SESM (<5%). In light of recent progress in climate policy, the BCC-SESM1.1 is hence more suitable for coupling with IAMs for the purposes of assessing climate outcomes.