An analysis of nine airborne campaigns and an aerosol model attributes about 40% of background stratospheric aerosol, excluding volcanic and wildfire contributions, to biogenic secondary organic aerosol. Monsoon convection provides routes from several regions into the upper atmosphere. The estimate could change how researchers account for ordinary aerosol loading between major eruptions, but it is a model-supported budget estimate rather than a direct global count.
Air above the weather layer contains aerosol particles even when neither a volcanic eruption nor a large wildfire is feeding it. Kai Qie, Pengfei Yu and colleagues identify a sizeable share of that background as biogenic secondary organic aerosol: particles formed from compounds released by living sources. Their analysis places the annual global share at about 40% outside those exceptional events.[1]
The team combined measurements from nine airborne field campaigns with an aerosol climate model. It identified upward transport through four major monsoon regions. These circulation routes carry surface-derived material into the upper troposphere and lower stratosphere, the part of the atmosphere where the study estimates its background contribution.[1]
The estimated transfer from the troposphere to the stratosphere is 0.42 to 0.72 teragrams of biogenic organic aerosol a year. The paper compares that range with average volcanic aerosol injection over the preceding 20 years and places it 5% to 90% higher. The comparison uses a long-term volcanic average, not the output of every eruption year. Stratospheric aerosols affect radiation and atmospheric chemistry, making their ordinary sources relevant to the background budget.[1]
