Clouds could be made more reflective and oceans fertilised to increase carbon dioxide absorption under ideas to be discussed at Australia's first high-level climate engineering conference later this month.
International interest in climate engineering – also known as geoengineering – is increasing as efforts to curb the world's emissions of greenhouse gases continue to falter.
Scientists said the event was an important step for Australia into the controversial geoengineering debate but expressed grave concerns some proposed technologies could have dangerous and far-reaching side effects.
Advertisement: Story continues below
The two-day science symposium, starting in Canberra on September 26, is being hosted by the Australian Academy of Science and the Australian Academy of Technological Sciences and Engineering.
Among the more controversial ideas being discussed is the injection of sulphur particles into the stratosphere to reflect sunlight and slow global warming.
Other technologies include fertilising oceans to increase uptake of carbon dioxide and spraying aerosols into the atmosphere to increase the reflectiveness of clouds.
But the meeting will also cover relatively benign ways to pull greenhouse gases from the atmosphere, including planting more trees and using climate-friendly agricultural techniques.
Speaker at the event Graeme Pearman, a respected climate scientist and former CSIRO chief of atmospheric research, told brisbanetimes.com.au it was a "very significant first step".
"It needs to be made clear that no one really wants to do this," Dr Pearman said.
"Some of the options are potentially dangerous, but we need to be prepared to act if we have to and we need to be assured that others will not act imprudently or in regional interest alone.
"It is my view we can only be assured of this by having these discussions out in the open."
Global emissions of greenhouse gases from burning fossil fuels hit an all-time high last year, according to the International Energy Agency.
Dr Pearman said the meeting was timely given slow global action to cut emissions and the observed changes in the climate. Also, private companies were already being set-up to "capitalise" on some geoengineering technologies.
In early 2009, German scientists dropped six tonnes of dissolved iron into the south-west Atlantic to fertilise a 300 square kilometre area. But scientists reported only a "modest" amount of CO2 had been soaked up.
Later this year, a team of academics in Britainare to test equipment that could spray particles 20 kilometres up into the atmosphere using a hose tethered to a balloon.
Geoengineering has gained prominence since Britain's Royal Society published a report in 2009 calling for more research into the area.
An international conference of 165 international scientists, including Dr Pearman, was also held in Asilomar in California last March and was part-funded by the Victorian Government.
The final report from the conference included a set of five principles to promote "responsible conduct of research on climate engineering".
Last November the UN Convention on Biological Diversity, to which Australia is a signatory, called a global moratorium on any geoengineering experiments that could affect biodiversity, but its effectiveness has been questioned.
Roger Gifford, chair of the AAS National Committee for Earth System Science, who will open the event, said Australia needed to be part of any global decisions, especially on how geoengineering was governed.
"Whether it is to squash some of these proposals or encourage certain aspects, Australia needs to be involved in the research and the global decision-making," he said.
Dr Gifford said it was "pretty much inevitable" that the globe would warm by 2 degrees above their pre-industrial levels.
"Everyone is aware that fiddling with the global energy balance directly could carry as many risks and potential unknowns as humanity's current collective fiddling with the greenhouse gas composition of the atmosphere has," he said.
In relation to geoengineering measures to block the sun's rays, Dr Gifford said: "Almost everyone in climate science is saying that if it comes to this then the world really is in a desperate shape climatically."
Also invited to speak at the Canberra meeting is author Clive Hamilton, professor of public ethics at Charles Sturt University, who is a strong critic of the principles and motivations behind many geoengineering technologies.
He fears some policy makers might see embracing geoengineering as an alternative to switching from fossil fuels to renewable energy.
"Anyone who has observed the politics of climate change knows that governments are keen to find alternatives to imposing deep emissions cuts,'' said Professor Hamilton, who is writing a book on geoengineering.
"If geoengineering appears to be an alternative to mitigation then governments will grab it if they can."
The Canberra conference, which costs $240 to attend, aims to "develop a southern hemisphere perspective" on geoengineering.
David Karoly, a leading atmospheric scientist at the University of Melbourne, said there was a perception the southern ocean was a preferred region to carry out ocean fertilization. This could have serious implications for marine biodiversity in the region, he said.
Professor Karoly warned cloud-whitening technologies and pumping sulphur particles high into the atmosphere could have global and regional impacts by changing rainfall patterns and damaging the ozone layer.
Falling sulphur particles and depleted ozone had additional human health impacts, he said.