Danger Dust

At appropriate temperatures, the tops of many clouds can be composed of either ice crystals or liquid water droplets. This difference affects their radiative properties and their precipitation behavior, which are important factors for climate projections or weather forecasting. Villanueva et al. combined observations and laboratory measurements to demonstrate that the proportion of ice-topped clouds is correlated with the abundance of dust particles in them. This confirms a relationship that has long been suggested but never demonstrated.