Global organic and inorganic aerosol hygroscopicity and its effect on radiative forcing.

The climate effects of atmospheric aerosol particles serving as cloud condensation nuclei (CCN) depend on chemical composition and hygroscopicity, which are highly variable on spatial and temporal scales. Here we present global CCN measurements, covering diverse environments from pristine to highly polluted conditions. We show that the effective aerosol hygroscopicity, κ, can be derived accurately from the fine aerosol mass fractions of organic particulate matter (ϵ) and inorganic ions (ϵ) through a linear combination, κ = ϵ ⋅ κ + ϵ ⋅ κ.