The linked article, supported by the associated linked reference, indicates that:
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An overlooked but powerful driver of cloud formation could accelerate the loss of polar sea ice.
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Global iodine emissions have tripled over the past 70 years, and scientists predict that emissions will continue to accelerate as sea ice melts and surface ozone increases.
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Researchers have observed in remote areas of Ireland, Greenland and Antarctica that iodine, which is released naturally from melting sea ice, algae and the ocean surface, may also be a significant driver of new particle formation.
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Based on these results, an increase of molecular iodine could lead to more particles for water vapor to condense onto and spiral into a positive feedback loop."
This newly identified positive cloud aerosol feedback mechanism has not been included in any climate model (including in any CMIP6 model), but could markedly increase polar amplification, and consequently climate sensitivity (possibly even above the CMIP6 Wolf Pack estimates), in coming decades.
Title: "Cloud-Making Aerosol Could Devastate Polar Sea Ice"
https://www.quantamagazine.org/cloud-making-aerosol-could-devastate-polar-sea-ice-20210223/Extract: "An overlooked but powerful driver of cloud formation could accelerate the loss of polar sea ice.
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Now, while studying the atmospheric chemistry that produces clouds, researchers have uncovered an unexpectedly potent natural process that seeds their growth. They further suggest that, as the Earth continues to warm from rising levels of greenhouse gases, this process could be a major new mechanism for accelerating the loss of sea ice at the poles — one that no global climate model currently incorporates.
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The full climate impact of this mechanism still needs to be assessed carefully, but tiny modifications in the behavior of aerosols, which are treated as an input in climate models, can have huge consequences, according to Andrew Gettelman, a senior scientist at the National Center for Atmospheric Research (NCAR) who helps run the organization’s climate models and who was not involved in the study. And one consequence “will definitely be to accelerate melting in the Arctic region,” said Jasper Kirkby, an experimental physicist at CERN who leads the Cosmics Leaving Outdoor Droplets (CLOUD) experiment and a coauthor of the new study.
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Researchers have observed in remote areas of Ireland, Greenland and Antarctica that iodine, which is released naturally from melting sea ice, algae and the ocean surface, may also be a significant driver of new particle formation. But researchers still wondered how molecular iodine grows into a CCN, and how efficiently it does so, compared with other secondary aerosols. “Even though these particles were known to exist, we weren’t able to link a measured concentration in the atmosphere to a predicted formation of particles,” Kirkby said.
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The findings are important for understanding the fundamental chemistry in the atmosphere that underlies cloud processes, Kirkby said, but also as a warning sign: Global iodine emissions have tripled over the past 70 years, and scientists predict that emissions will continue to accelerate as sea ice melts and surface ozone increases. Based on these results, an increase of molecular iodine could lead to more particles for water vapor to condense onto and spiral into a positive feedback loop. “The more the ice melts, the more sea surface is exposed, the more iodine is emitted, the more particles are made, the more clouds form, the faster it all goes,” Kirkby said.
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Clouds generally cool the planet, as the white tops of the clouds reflect sunlight into space. But in polar regions, snowpack has a similar albedo, or reflectivity, as cloud tops, so an increase in clouds would reflect little additional sunlight. Instead, it would trap longwave radiation from the ground, creating a net warming effect.
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In 2019, NCAR’s model projected a climate sensitivity well above IPCC’s average upper bound and 32% higher than its previous estimate — a warming of 5.3 degrees C (10.1 degrees F) if the global carbon dioxide is doubled — mostly as a result of the way that clouds and their interactions with aerosols are represented in their new model.
Brock remains hopeful that future research into new particle formation will help to chip away at the uncertainty in climate sensitivity. “I think we’re gaining an appreciation for the complexity of these new particle sources,” he said."
See also:
He, X.-C. et al. (05 Feb 2021), "Role of iodine oxoacids in atmospheric aerosol nucleation", Science, Vol. 371, Issue 6529, pp. 589-595, DOI: 10.1126/science.abe0298
https://science.sciencemag.org/content/371/6529/589AbstractIodic acid (HIO3) is known to form aerosol particles in coastal marine regions, but predicted nucleation and growth rates are lacking. Using the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we find that the nucleation rates of HIO3 particles are rapid, even exceeding sulfuric acid–ammonia rates under similar conditions. We also find that ion-induced nucleation involves IO3− and the sequential addition of HIO3 and that it proceeds at the kinetic limit below +10°C. In contrast, neutral nucleation involves the repeated sequential addition of iodous acid (HIO2) followed by HIO3, showing that HIO2 plays a key stabilizing role. Freshly formed particles are composed almost entirely of HIO3, which drives rapid particle growth at the kinetic limit. Our measurements indicate that iodine oxoacid particle formation can compete with sulfuric acid in pristine regions of the atmosphere.
