Aerosols, small liquid or solid particles suspended in the air, are found throughout the troposphere and originate from both anthropogenic (e.g. vehicle exhaust) and natural sources (e.g. wildfires). Biomass burning is a significant contributor to aerosol concentrations in most regions of the world. Smoke from biomass burning consists of mostly organic aerosol, referred to as biomassburning organic aerosol (BBOA). For example, smoke sampled from wildfires in the western U.S.A. consisted of > 90% BBOA. BBOA can cause negative health effects. In addition, BBOA contains light absorbing molecules known as brown carbon (BrC) that warm the climate by absorbing sunlight. BBOA also acts as nuclei for liquid cloud droplets and possibly ice clouds, thereby indirectly modifying the climate. As climate change continues, the frequency and intensity of wildfires is increasing in many regions due to rising temperatures and changing precipitation patterns. This should cause the portion of aerosols attributed to biomass burning to grow.