A global plan to put man-made particles into the atmosphere to deflect the Sun's heat would rapidly lower global 
temperatures until cuts in carbon dioxide emissions took effect, they argued.
They acknowledged concerns about geo-engineering but said multi-national experiments should begin soon before it is too late to reverse climate change or in case a rogue state carried out separate measures.
The environmental scientists, David Keith of the University of Calgary in Canada, Edward Parson of the University of Michigan and Granger Morgan of Carnegie Mellon University, were writing an editorial in the journal, Nature.
They called for governments to establish a multimillion-pound fund for research into the simulated volcanoes and other solar-radiation management techniques for shielding the Earth against sunlight. More on Telegraph