Fossil fuel CO2 Emissions in China (2015–2023) Inferred from Co-emitted NO2 Observations

Accurate quantification of China’s fossil fuel CO2 (FFCO2) emissions interannual variations is critical for climate policy evaluation. However, bottom-up inventories have exhibited increasing discrepancies. Here, we estimate 2015–2023 FFCO2 emissions over China using the Regional multi-Air Pollutant Assimilation System (RAPAS), integrating in-situ observations of co-emitted NO2 and grid-specific CO2-to-NOx ratios. National total FFCO2 averaged 11.5 ± 1.5 PgCO2·yr⁻¹, with over 45% from North (NC) and East China. Emission intensity (per GDP) exhibited a southeast-to-northwest increasing gradient, aligning with economic development patterns. Interannually, emissions showed a notable upward trend during 2015–2017 driven by NC and Central China, then stabilized during 2018–2023 amid policy interventions and COVID-19 disruptions, contrasting with sustained growth in widely used bottom-up inventories. Total annual growth averaged 189.6 TgCO2·yr-1 (1.6%). NC grew fastest at 73.0 TgCO2·yr⁻¹, while Southwest China declined slightly. Emission intensity fell 5.6% annually, with the largest drops in Southwest China (8.9%). This observation-constrained dataset clarifies spatiotemporal dynamics and policy impacts, supporting targeted strategies for China’s carbon goals. FFCO2_NOx_Emissions_2015-2023.nc Contains the optimized monthly fossil fuel CO₂ (FFCO₂) and NOₓ emissions over China during 2015–2023. NO2_SRUFCONC_2015-2023.nc Contains the optimized daily surface-layer NO₂ concentrations over China during 2015–2023.