It may be possible to engineer better ways to control the planet's climate and prevent dangerous global warming than mimicking volcanoes, a University of Calgary climate scientist has opined.
"Releasing engineered nano-sized disks, or sulphuric acid in a condensable vapour above the Earth, are two novel approaches. These approaches offer advantages over simply putting sulphur dioxide gas into the atmosphere," says David Keith, a director in the Institute for Sustainable Energy, Environment and Economy and a Schulich School of Engineering professor.
Keith, a global leader in investigating this topic, says that geoengineering, or engineering the climate on a global scale, is an imperfect science.
"It cannot offset the risks that come from increased carbon dioxide in the atmosphere. If we don't halt man-made CO2 emissions, no amount of climate engineering can eliminate the problems - massive emissions reductions are still necessary," he added.
Nevertheless, Keith believes that research on geoengineering technologies, their effectiveness and environmental impacts needs to be expanded.
"I think the stakes are simply too high at this point to think that ignorance is a good policy," he added.
Keith suggests two novel geoengineering approaches-'levitating' engineered nano-particles, and the airborne release of sulphuric acid-in two newly published studies.
One of study was authored by Keith alone, 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.
Keith says that sulphates are blunt instruments for climate engineering. It's very difficult to achieve the optimum distribution and size of the aerosols in the atmosphere to reflect the most solar radiation and get the maximum cooling benefit.
"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," said Keith.
In his first study, 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.
According to Keith, the distribution of engineered nano-particles above the Earth could be more controlled and less likely to harm the planet's protective ozone layer.
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 an aircraft would give better control of particle size.
The study says this would reflect more solar radiation back into space, while using fewer particles overall and reducing unwanted heating in the lower stratosphere.
The study included computer modelling that showed that the sulphuric acid would quickly condense in a plume, forming smaller particles that would last longer in the stratosphere and be more effective in reflecting solar radiation than the large sulphates formed from sulphur dioxide gas.