The dust is the ice manufacturer

The dust plays an important role in the formation of ice in the atmosphere. TO New satellite data analysis, published in ScienceIt shows that the dust can make a cloud water drops freeze at warmer temperatures than they would. The finding brings what researchers had observed in the laboratory at the atmosphere scale and can help climatic scientists better future climate changes.

In 1804, the French scientist Joseph Louis Gay-Lussac amounted to approximately 23,000 feet (7,000 meters) in a hydrogen balloon from Paris, without supplementary oxygen, to collect air samples. He pointed out that the clouds with more dust particles tended to have more frozen drops.

In the twentieth century, scientists discovered that pure water can remain liquid even when it cools to -34.5 ° C. but once small amounts of material are introduced, such as dust, freezes at much warmer temperatures.

In 2012, researchers in Germany could finally try this directly in a cloud chamber experiment. They recreated cloud conditions in the laboratory, introduced different types of desert dust and gradually cooled the camera to observe the temperatures at which the drops froze.

For Diego VillanuevaAtmospheric scientist of Eth Zürich in Switzerland and main author of the new study, it was surprising that scientists have discovered these processes in the laboratory, however, no one had examined them in such detail in nature.

The challenges were obvious. To see an ice crystal nucleate, researchers would need instruments in a plane or globe to catch a micrometric size drop in a cloud at the right time. “It’s like Schrödinger’s cat,” he said Daniel KnopfAn atmospheric scientist at Stony Brook University who did not participate in work … “or there is an ice crystal or there is a drop of liquid.”

In the new study, Villanueva and his colleagues analyzed 35 years of satellite data on tops on clouds in the extremes of the northern hemisphere, a region that covers the west of the United States, southern Canada, Western Europe and northern Asia. The researchers wanted to see if the dust influenced whether the clouds were liquid or ice. They focused on the clouds, instead of whole clouds, simply because the tops are visible in satellite images.

Desert dust and cold clouds

Villanueva and his colleagues examined two sets of satellite data that cover 1982-2016, trying to infer microscopic details of cloud peaks, such as the amount of ice crystals or drop sizes. A data set traced whether the top of the clouds were liquid or ice, and the other measured how much dust was in the air at the same time. Although the team examined the global patterns, they focused on the Northern Extropical Belt, where the mixed phase clouds are common and large amounts of dust of the deserts such as the Sahara and the Gobi circulate.

But the “quality of the data set was so poor that everything that came out was basically noise,” Villanueva added. In the end, the researchers focused on a simpler detail: the fraction of clouds with ice in their blouses. “This took me almost 3 years,” Villanueva said.

The analysis revealed that the regions with more dust had more ice clouds. The effect was stronger in summer, when the desert winds raise the greatest amount of dust.

A distinctive pattern arose: an increase of ten times in dust doubled approximately the probability of freezing the top of the clouds. “I would need 100 times more dust to see that freezing becomes 4 times more frequent,” Villanueva explained.

The new work showed that the same processes that researchers have observed microescala in laboratories occur to much larger scales in the Earth’s atmosphere. Even after taking into account moisture and air movement, dust remained the key factor for ice nucleation in most cases, although there are exceptions. In some places, as above the Sahara, few clouds are formed despite the presence of dust, perhaps, the authors suggest, because the movement of large strips of hot air avoids freezing.

“I think the study is quite elegant,” said Knopf. He explained that taking 35 years of satellite data, finding a relationship between dust levels and rates at the top of the frozen cloud, and then demonstrating that it aligns perfectly with laboratory experiments is basically “the nail in the coffin” to demonstrate the role of dust in ice nucleation. Scientists now have robust satellite evidence of dust aerosols that directly affect the freezing of clouds, coinciding with what laboratory experiments had predicted.

The finding has implications for climate modeling. To predict the effects of climate change with greater precision, the models must explain the dust and the ways in which it affects the freezing of the cloud and helps to shape precipitation. Clouds with liquid lid reflect more sunlight and cool the planet, while ice clouds show more sunlight and trap.

However, Knopf said there is more work to do to understand exactly what new observations mean for the understanding of scientists about the climate. “If you really want to know precipitation or climatic impacts [of dust]You really need to know the amount of liquid drops or the amount of ice crystals, ”he said.

Villanueva is motivated to continue looking at clouds and aerosols. In the next 10-20 years, the earth can have drier surfaces due to climate change, which will probably produce more dust aerosols in the atmosphere. He added: “I want to know how the clouds will respond on stage.”

—Saugat Bolakhe (@Saugat_opimist), Scientific writer

Citation: Bolakhe, S. (2025), the dust is the ice manufacturer of the sky, EOS, 106, https://doi.org/10.1029/2025EO250328. Posted on September 5, 2025.

Text © 2025. The authors. CC BY-NC -nd 3.0
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