Climate models miss most of the warming coarse dust in the atmosphere

Desert dust dominates the total mass of aerosols in the atmosphere, and the coarse dust particles (diameter D≥5µm) account for a substantial fraction of the dust mass. In contrast to fine dust (D<5µm), which cools the climate system, coarse dust predominantly warms the climate through the absorption of shortwave and longwave radiations. Despite the abundance and climatic importance of coarse dust, global models consistently underestimate their prevalence when compared to measurements. Here, we estimate the global atmospheric loading of coarse dust using a framework that leverages available measurements of atmospheric dust size distributions. We find that the atmosphere contains 16 (9 – 29) Tg of coarse dust, whereas current climate models account for only 4 (2 – 12) Tg, and thus miss the majority of coarse dust when compared to measurements. Accounting for the missing coarse dust indicates that the top-of-atmosphere dust radiative cooling is overestimated, even when compared against similar estimates that constrained dust particles only at emission.