for National Geographic News
A Nobel Prize-winning scientist has proposed a controversial method for protecting Earth from global warming: seeding the atmosphere with sulfur to reflect the sun's rays.
In the current issue of the journal Climate Change, Paul Crutzen of Germany's Max Planck Institute for Chemistry suggests injecting particles of sulfur into the stratospherethe upper layer of the atmosphereto cool the planet and buy time for humans to reduce greenhouse gas emissions.
The sulfur particles would be dropped from high-altitude balloons or fired into the atmosphere with heavy artillery shells, he says.
Once airborne the particles would act like tiny mirrors, bouncing the sun's light and heat back into space.
Crutzen's plan would imitate the cooling effects of volcanic eruptions, which send large sulfur-rich clouds into the atmosphere.
When Mount Pinatubo in the Philippines erupted in 1991, he points out, the huge plume of sulfur cooled the Earth by 0.9 degree Fahrenheit (0.5 degree Celsius) the following year.
A relatively small amount of sulfate could produce a level of cooling similar to that caused by the Pinatubo eruption, according to Crutzen's calculations.
Crutzen, who won the Nobel Prize in Chemistry in 1995 for his work on the ozone layer, stresses that it is still important for nations to cut back greenhouse gas emissions, but extreme measures like this may be necessary to provide more time.
(See National Geographic magazine's "Global Warning: Signs From Earth.")
"I hope that my experiment will never have to take place," he said in an email.
This isn't the first time that scientists have suggested meddling with Earth's climate in order to reduce the impact of global warming.
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