Research would also be needed to determine whether such nano-particles could be effectively distributed, given the complex interplay of forces in the atmosphere, and how much cooling might be achieved at the planet's surface.
It is also unknown whether the amount of particles neededabout 1 trillion kilograms per year or 10 million tonnes over 10 yearscould be manufactured and deployed at a reasonable cost.
However, Keith notes another study, which looked at the cost of putting natural sulphates into the stratosphere.
"You could manipulate the Earth's climate at large scale for a cost that's of the order of $1 billion a year. It sounds like a lot of money, but compared to the costs of managing other environmental problems or climate change, that is peanuts."
"This is not an argument to do it, only an indication that risk, not cost, will be the deciding issue," he adds.
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 modeling 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.
Keith stresses that whether geoengineering technology is ever used, it shouldn't be seen as a reason not to reduce man-made greenhouse gas emissions now accumulating in the atmosphere.
|Contact: Hollie Roberts|
University of Calgary