SO2 can’t offset warming – its effect is temporary

Models are only models, of course. But whatever the precise scale of the current aerosol effect, it would be quite wrong to imagine that it can carry on protecting us from the worst as global warming gathers momentum. That is because aerosols and greenhouse gases have different life spans in the atmosphere. Aerosols stay for only a few days before they are washed to the ground in the rain. By contrast, carbon dioxide has a life span of a century or more. If, for sake of argument, we stuck with current emission levels of both aerosols and carbon dioxide, the aerosol levels in the air would stay the same. There would be no accumulation and no increase in the cooling effect. But carbon dioxide levels would carry on rising and produce ever greater warming.