To further emphasize the importance of including the hydrophobic phase at the surface of BBOA particles, we extend the KM-GAP model to simulate τBrC for three locations within the planetary boundary layer (specifically at 0.5 km altitude and 0°, 40° and 80° latitude; see square symbols in Fig. ). The KM-GAP model shows that τBrC for a phase-separated particle is a factor of 3.0, 4.4, and 50 times larger than a hydrophilic-only particle at these three locations (Fig. ). In addition, a two-phase core-shell particle of BBOA will have an atmospheric lifetime of 0.8, 1.7 and 12 days at these three locations within the planetary boundary layer. In contrast, it has previously been assumed that τBrC is 1 day everywhere in the planetary boundary layer when predicting the climatic effects of BBOA . We conclude that the total BBOA aerosol including the presence of liquid-liquid phase separation needs to be considered when estimating τBrC. Particularly in the planetary boundary layer and at polar regions, the lifetime of BrC and hence its warming effect can be much larger than assumed in previous modelling studies.