This research project assesses biases in traditional, filter-based, aerosol absorption measurements by comparison to state-of-the-art, non-filter-based, or in situ, measurements. We assess biases in traditional absorption measurements for three main aerosol types, including dust and fresh and aged biomass burning aerosols. The main results of this study are that the traditional and state-of-the-art absorption measurements are well correlated and that biases in the former are up to 45 %.