Understanding long-term organic aerosol (OA) trends and their driving factors is important for air quality management. Our modeling revealed that OA in China increased by 5.6 % from 1990 to 2019, primarily due to a 32.3 % increase in secondary organic aerosols (SOAs) and an 8.1 % decrease in primary organic aerosols (POAs), both largely driven by changes in anthropogenic emissions. Biogenic SOA increased due to warming but showed little response to changes in anthropogenic nitrogen oxide emissions.

Using a one-dimensional radiative–convective equilibrium model, we show that in clear-sky conditions, stratospheric sulfate aerosol forcing weakens with increasing surface temperature while CO₂ forcing varies much less. This effect arises as sulfate aerosol, unlike CO₂, absorbs mainly at wavelengths where the atmosphere is optically thin. It thereby masks the surface emission, which increases with warming. The spectral masking also results in weaker radiative feedback when aerosol is present.