Four monsoon routes
Kai Qie, Pengfei Yu and colleagues read 9 airborne campaigns with the sectional aerosol model CESM1-CARMA and find that biogenic secondary organic aerosol is about 40% of background stratospheric aerosol outside volcanoes and wildfires. The transport climbs through the monsoons of South America, central Africa, Indonesia-Australia and southern Asia into the upper troposphere and lower stratosphere.[1]
The troposphere-to-stratosphere flux of biogenic organic aerosol is 0.42 to 0.72 teragrams a year. That range is 5% to 90% larger than the volcanic aerosol injection averaged over the past 20 years. Stratospheric aerosols change the global radiative and chemical balance, and this share is living mass inside that balance. For climate, the study reads that mass as a background term fed by biogenic emissions.[1]
Whose account the wide band is
The spread from 5% to 90% depends on the choice of volcanic average as much as on any single figure for the living flux. An alternative reading is that the 9 campaigns weigh some monsoon basins more heavily than a uniform global count would.[1]
The mark to watch is whether a non-volcanic, non-wildfire background account writes this biogenic flux on its own line inside the 0.42 to 0.72 teragram band.[1]