University of Calgary

Global warming

September 7, 2010

Stopping global warming

Mt. Pinatubo is an active volcano in the Philippines frequently studied by scientists. Photo credit: Courtesy of the U.S. Geological SurveyMt. Pinatubo is an active volcano in the Philippine's frequently studied by scientists. Photo credit: Courtesy of the U.S. Geological Survey.There may be better ways to engineer the planet’s climate if needed to prevent dangerous global warming than mimicking volcanoes, a University of Calgary climate scientist says in two new studies.

Releasing engineered nano-sized disks or sulphuric acid, a condensable vapour, above the Earth are two novel approaches that offer advantages over simply putting sulphur dioxide gas into the atmosphere, says Dr. David Keith, a director in the Institute for Sustainable Energy, Environment and Economy and a Schulich School of Engineering professor.

Geoengineering, or engineering the climate on a global scale, “is inherently imperfect,” says Keith, who is in the vanguard of scientists worldwide investigating the topic.

“It cannot offset the risks that come from increased carbon dioxide in the atmosphere,” he says. “If we don’t halt man-made CO2 emissions, no amount of climate engineering can eliminate the problems—massive emissions reductions are still necessary.”

Keith suggests two novel geoengineering approaches—‘levitating’ engineered nano-particles and the airborne release of sulphuric acid—in two newly published studies, one he solely authored and the other with scientists in Canada, the U.S. and Switzerland.

Scientists investigating geoengineering have so far looked mainly at injecting sulphur dioxide into the upper atmosphere. This approach imitates the way volcanoes create sulphuric acid aerosols, or sulphates, that will reflect solar radiation back into space—thereby cooling the planet’s surface.

One advantage of using sulphates is that scientists have some understanding of their effects in the atmosphere because of emissions from volcanoes such as Mt. Pinatubo, Keith says.

“A downside of both these new ideas is they would do something that nature has never seen before. It’s easier to think of new ideas than to understand their effectiveness and environmental risks.”

In his study in the Proceedings of the National Academic of Sciences, a top-ranked international science journal, Keith describes a new class of engineered nano-particles that might be used to offset global warming more efficiently and with fewer negative side-effects than using sulphates.

In a separate new study published in the journal Geophysical Research Letters, Keith and international scientists describe another geoengineering approach that may also offer advantages over injecting sulphur dioxide gas.

Releasing sulphuric acid, or another condensable vapour, from aircraft would give better control of particle size, thereby reflecting more solar radiation back into space while using fewer particles overall and reducing unwanted heating in the lower stratosphere, they say.

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