We examine 20 years (2004–2023) of vertical profiles of winter/spring lower stratospheric ozone inside the Antarctic vortex, based on satellite observations and a chemistry climate model. The observations show increases in the smallest ozone values, as well as trends consistent with a slow recovery from the long-term impact of ozone-depleting substances. The model also shows some reductions in lower stratospheric seasonal Antarctic ozone losses, in broad agreement with the observations.

Atmospheric particles affect climate by absorbing water and forming clouds, but how organic aerosols uptake water remains unclear. Our field measurements in rural eastern China show their hygroscopicity depends more on emission sources – especially biomass burning – than oxidation. Aging increases water uptake from biomass burning, but not from other sources. These results urge models to include source information for better climate predictions.