DURBAN, South Africa (AP) - Brighten clouds with sea water?
Spray aerosols high in the stratosphere? Paint roofs white and plant light-colored crops? How about positioning "sun shades" over the Earth?
At a time of deep concern over global warming, a group of scientists, philosophers and legal scholars examined whether human intervention could artificially cool the Earth - and what would happen if it did.
A report released late Thursday in London and discussed Friday at the U.N. climate conference in South Africa said that - in theory - reflecting a small amount of sunlight back into space before it strike's the Earth's surface would have an immediate and dramatic effect.
Within a few years, global temperatures would return to levels of 250 years ago, before the industrial revolution began dumping carbon dioxide into the air, trapping heat and causing temperatures to rise.
But no one knows what the side effects would be.
They could be physical - unintentionally changing weather patterns and rainfall. Even more difficult, it could be political - spurring conflict among nations unable to agree on how such intervention, or geoengineering, will be controlled.
The idea of solar radiation management "has the potential to be either very useful or very harmful," said the study led by Britain's Royal Society, the Washington-based Environmental Defense Fund and TWAS, the academy of sciences for the developing world based in Trieste, Italy.
Environmentalist Silvia Ribeiro, of the Canada-based ETC-Group, said geoengineering should be outlawed before it gets off the ground.