An evaluation of global atmospheric CO2 simulation by the GEOS-Chem using multiple observations in the period 2010-2020

Atmospheric carbon dioxide (CO₂) in the atmosphere has increased mainly due to anthropogenic fossil fuel emissions, resulting in accelerating global warming and increasing climate variability. Atmospheric chemical transport models are powerful tools for understanding mechanisms between emission/sink and the spatiotemporal distribution of atmospheric CO₂.

We aim to provide information on GEOS-Chem CO₂ simulation to assess the mitigation strategies over East Asia under future emission scenarios. To achieve this, we first need to evaluate the model performance of the global simulation. We investigated trends and characteristics of atmospheric CO₂ from the model with ground-based in-situ observations from the World Data Centre for Greenhouse Gases; (WDCGG), Total Carbon Column Observing Network (TCCON), and satellite observations (e.g., the Greenhouse Gases Observing Satellite; GOSAT, the Orbiting Carbon Observatory 2; OCO-2).

Overall, modeled CO₂ concentrations showed reasonable seasonal, annual amplitudes, and spatiotemporal distributions. They also agreed well with ground-based observations and satellite observations. Our global simulation was highly correlated with in-situ observations (Index of agreement (IOA) ≈ 0.9), and also showed excellent performance (Correlation coefficient (R) > 0.9) compared with satellite observations. Our study provides broad information on global simulation to identify features of monitoring measurements and modeling. We anticipate that our model configuration is capable of studying future emission scenarios in East Asia.