Ice nucleation in the atmosphere has a complex impact on the climate, altering the way clouds interact with solar radiation and hence modifying Earth's radiative budget, as well as affecting precipitation and cloud lifetimes . The role that organic aerosol play in the nucleation of ice is still an active area of debate , but some studies suggest that glassy organic aerosol (at least single-component glassy aerosol) can act as a heterogeneous nuclei for ice clouds . Ice nucleation arising from wildfire smoke plumes in the free troposphere has been observed , with the mechanism thought to be from soot (from flaming combustion) or from inorganic components and minerals naturally present in biomass . As the outer shell of BBOA can exhibit viscosities commensurate with those of a glass even at high RHs, we speculate that the organic aerosol component of biomass burning plumes might represent an additional mechanism towards ice nucleation, with resulting climatic impacts. In terms of liquid cloud droplet nucleation, the presence of the hydrophobic outer shell in a BBOA particle would also likely reduce the particle's surface tension compared to if it were to comprise only a well-mixed single phase . Hence, this phase separation behavior could increase the ability of BBOA to nucleate liquid cloud droplets , thereby indirectly affecting Earth's interaction with solar radiation.