Desert dust, created by wind erosion in arid regions, is the main source of ice-nucleating particles (INPs) in the atmosphere, which are crucial for determining the balance between ice crystals and liquid droplets in mixed-phase clouds (MPCs). Without INPs, cloud droplets in MPCs would remain liquid until they reach about -37°C, the temperature at which homogeneous freezing occurs. However, INPs can trigger ice crystal formation earlier, leading to rapid ice growth. This influences precipitation, cloud properties, and the Earth’s albedo (the fraction of incoming sunlight that the planet reflects back into space, influencing its overall climate and temperature).

Earth System Models rely on accurate representations of INP levels to simulate ice crystal concentrations, but uncertainties in these levels lead to discrepancies in modelled climate sensitivity to greenhouse gases. With global warming, more liquid water in MPCs is expected, potentially cooling the planet by increasing cloud reflectivity. However, the extent of this cooling effect, known as negative cloud-phase feedback, is highly uncertain due to gaps in understanding INP behavior.

In dust-rich environments, future increases in dust could lead to more ice crystals at the expense of liquid droplets, reducing cloud reflectivity and causing a warming effect. Current knowledge gaps in the abundance, trends, and properties of INPs, particularly from desert dust, limit the accuracy of climate models.

The CERTAINTY project aims to address these gaps by improving the representation of desert dust’s contribution to ice nucleation in MPCs and its impact on radiative forcing. Using new observational data on dust trends, mineralogy, and other factors, CERTAINTY seeks to enhance our understanding of this critical component of the Earth’s climate system.