"Volcano Cure" for Warming? Not So Fast, Study Says

Kate Ravilious
for National Geographic News
August 17, 2007

A controversial theory proposes mimicking volcanoes to fight global warming. But throwing sulfur particles into the sky may do more harm than good, a new study says.

The temporary solution would pump particles of sulfur high into the atmosphere—simulating the effect of a massive volcano by blocking out some of the sun's rays. This intervention, advocates argue, would buy a little time to reduce greenhouse gas emissions.

But as well as cooling the planet, the sulfur particles would reduce rainfall and cause serious global drought, a new study says.

"It is a Band-Aid fix that does not work," said study co-author Kevin Trenberth of the National Center for Atmospheric Research (NCAR) in Boulder, Colorado.

It's just one of several drastic measures proposed to combat global warming, now that most scientists are in agreement that carbon dioxide, primarily from burning fossil fuels, is changing Earth's climate.

Drying Effects

Trenberth and NCAR colleague Aiguo Dai studied worldwide rainfall and streamflow records for the world's largest rivers between 1950 and 2004.

During this period three major volcanic eruptions occurred: Mount Agung in Indonesia in 1963, El Chichón in Mexico in 1982, and Mount Pinatubo in the Philippines in 1991.

It's well known that particles thrown into the atmosphere by volcanic eruptions cause a global cooling effect by reflecting back sunlight.

In the case of Mount Pinatubo, global temperatures dropped by an average of 0.9 degrees Fahrenheit (0.5 degrees Celsius) the following year. But until now, no one had been able to pin down the effect that these volcanoes might have had on rainfall.

By carrying out statistical analysis on rainfall and streamflow records, the researchers were able to detect a significant drying effect after Mount Pinatubo's eruption.

There was less rainfall over land, and a record decrease in runoff and ocean discharge into the ocean from October 1991 to September 1992, the scientists report this week in the journal Geophysical Research Letters.

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