Lead-containing aerosols are highly efficient propagators of atmospheric ice formation, according to a study published online in Nature Geoscience. The findings provide insight into the influence of the large quantities of lead present in the atmosphere before the switch to unleaded fuel last century.
Daniel Cziczo and colleagues examined the ability of lead to generate ice crystals in artificial clouds. They found that lead particles generated nearly half of the ice formed. Furthermore, analysis of residues from atmospheric ice revealed that a third of ice-forming particles contained lead, suggesting that lead triggers ice formation in natural conditions. They estimate that if lead was present in all ice-forming particles, ice production would increase, and more sunlight would be reflected back to space.
The authors suggest that post-industrial emissions of particulate lead may have offset a proportion of the warming attributed to greenhouse gases.