Mineral dust microparticles traveling from deserts to the upper atmosphere play a key role in ice formation in clouds in the northern hemisphere.
This is demonstrated by a study led by the ETH Zurich Institute, which analyzed 35 years of satellite data to understand how this phenomenon affects global climate dynamics.
Ice crystals driven by dust
The scientific team focused on mixed clouds —formed by supercooled water and ice— that appear between 0 °C and -39 °C, especially in regions like the North Atlantic, Siberia, and Canada.
According to the researchers, these clouds react strongly to the presence of ice nuclei generated by desert dust aerosols.
“Where there is more dust, it is much more likely for clouds to freeze at the top,” explained Diego Villanueva, atmospheric physicist and lead author of the study.
Satellites and laboratory: a revealing coincidence
By comparing the frequency of icy clouds with dust levels in the atmosphere, researchers found a consistent pattern: more dust and lower temperatures result in increased ice formation.
This behavior coincides with what is observed in laboratory experiments, validating for the first time the correspondence between experimental microscale and satellite macroscale.
“This is one of the first studies that demonstrates that satellite measurements match what we know in the laboratory,” highlighted Ulrike Lohmann, study co-author.
Climatic impact of cloud glaciation
The way clouds glaciate determines:
- How much sunlight is reflected back into space
- How much water is released as rain or snow
These factors are essential for global climate models, which until now lacked a solid reference on how glaciation occurs on a large scale.
From nanoscale to global atmosphere
The study reveals that nanometric imperfections on the dust surface can initiate the freezing of water droplets, generating ice crystals that expand across kilometers of atmosphere.
This connection between the microscopic and macroscopic opens new research avenues in atmospheric physics and climatology.
Geographical variability of the phenomenon
In areas like the Sahara, cloud formation is limited, and warm ascending currents can inhibit glaciation. In the southern hemisphere, marine aerosols serve similar functions to desert dust, albeit with different effects.
The findings provide a new piece to the puzzle of climate change. “This helps identify one of the most uncertain pieces of the climate puzzle,” Villanueva concluded.
Although further studies are needed to understand the role of factors such as humidity or intensity of ascending currents, this work establishes a measurable relationship between atmospheric dust and ice formation in clouds, which will help improve climate projections on a global scale.
