BASIC: A Boosted Aerosol‐Size‐Integrated XCO ₂ Retrieval Algorithm

Accurate retrieval of dry air mole fraction of CO 2 (XCO 2 ) is essential for tracking emissions and supporting mitigation. However, aerosols, especially their particle size distribution (PSD), introduce significant uncertainties via scattering and absorption, yet are often overlooked in current methods. Here we present a boosted aerosol‐size‐Integrated XCO 2 (BASIC) retrieval algorithm that flexibly accounts for aerosol‐induced lightpath modifications. Validation at five TCCON sites in East Asia shows that BASIC reduces RMSE by 30% and 13% compared to standard and bias‐corrected OCO‐2 products, respectively. Moreover, BASIC more accurately reproduces the observed spectra, particularly in the aerosol‐sensitive O 2 A band, outperforming the ACOS algorithm. These improvements highlight the importance of incorporating variable aerosol PSD in retrievals and demonstrate that BASIC enables a more accurate representation of aerosol effects on radiative transfer. Our results suggest that PSD‐aware retrievals can significantly improve the accuracy of satellite‐derived XCO 2 estimates under heavy aerosol loading conditions.