Surprising Clouds Forming Due to Lead in Air

Brian Handwerk
for National Geographic News
April 19, 2009

Lead in the air is causing clouds in odd conditions—in conditions typically too warm and dry for cloud formation—according to scientists who've "bottled" clouds and even grown their own.

Driven mainly by industrial lead-dust emissions, lead-heavy clouds could change weather patterns and might actually help fight global warming, the study suggests.

Researchers collected cloud samples atop a Swiss mountain and found that about half of their ice crystals contained lead. Then, by building artificial clouds in laboratory chambers, the team determined that lead actually causes ice crystals to form.

Clouds formed in warmer, drier air when lead was present, the team found. The element "supercharges" the dust particles at the cores of most cloud crystals, according to the new study.

(Related: "Mysterious Clouds More Common Due to Climate Change?")

Change in the Weather?

As our world warms and becomes drier, these leaded clouds may drive unpredictable changes in rain and snowfall, the researchers speculate.

Since the 1940s, scientists have known that seeding clouds with lead can hasten ice-crystal formation and precipitation, said atmospheric chemist Dan Cziczo of the U.S. Department of Energy's Pacific Northwest National Laboratory.

"But this is the first time we've found that lead in the environment, inadvertently added by human activities like burning coal, is having the same effect," he said.

"What we need are follow-up studies to explore how this might change precipitation patterns," Cziczo noted

Global Warming Fighter?

The leaded clouds may have a silver lining.

The "extra" clouds form lower in the sky, according to the team's computer simulations. Lower clouds allow more of Earth's heat to escape into space.

Even so, leaded clouds shouldn't be seen as quick fixes for global warming, the researchers say.

"This just highlights how complicated the climate system is," Cziczo said.

And though humans put less lead into the atmosphere than they did during the 20th-century heyday of leaded gasoline, lead emissions could hit lofty heights again if coal plants proliferate without stringent controls.

Findings published online today in the journal Nature Geoscience.




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