If you'll allow me to speak, it's necessary, to stabilize emissions — we're not even talking about cooling — so that the climate stabilizes at a level two degrees warmer than the current climate, for another three centuries, we would need a reduction of 1.8 tonnes of carbon, that is to say the equivalent of approximately five tonnes of CO2 a year per inhabitant of the planet, until 2050-2060, in the event it would be possible to sequester carbon and to use other means to stabilize the amount of emissions. That would mean a doubling of the pre-industrial concentration. That quantity corresponds to roughly half of what is emitted by a Quebecker each year or to one-third of what is emitted by a Canadian in general. That's a relatively imprecise measurement, but that's the order of magnitude that the studies are currently giving us.
On November 7th, 2006. See this statement in context.