Some experts on global warming say that sulphates in the upper atmosphere block the sun and cause the earth to cool…so was cleaning up these emissions the wrong thing to do? Suppose we were to stop scrubbing cola powred power plants exhausts-could this reverse global warming?
Well, there are a few problems with such an approach. The most obvious one is that there are other good reasons why we want to clean up these pollutants, e.g., acid rain and health effects. [As a more extreme example, starting a serious nuclear exchange would also probably lead to a cooling effect to counteract the warming but it is obviously not a preferred solution.]
Furthermore, the problem is that the lifetimes of sulfate aerosols and CO2 in the atmosphere are very different. CO2 hangs around for a lot longer. What that means is that CO2 is cumulative…i.e., even if we freeze emissions at the current rates, CO2 levels will continue to rise and hence the warming effect will continue to increase. Whereas, with sulfate aerosols, the lifetime is short enough that the concentration in the atmosphere is roughly proportional to the rate you are putting them into the atmosphere over time. Therefore, even if we held CO2 emissions constants, we would have to steadily increase our emissions of sulfate aerosols.
Thirdly (and not completely independent of these last two points), this is a sort of “swallow the fly to catch the spider” approach to solving the problem. And, to do it well requires much more specific understanding of the exact effects of each of these on climate than it takes to just try to reduce our influence on the climate by cutting back on emissions. (In particular, there are still very large error bars on the climatic forcing due to sulfate aerosols…In fact, the uncertainty here is probably the single largest reason why the warming that we have seen over the 20th century cannot be used to put reasonably tight bounds on the climate sensitivity…and hence to know more accurately how large the warming due to increasing greenhouse gases will be.) It also might lead to unknown consequences that we do not yet appreciate.
And, also, this does not address the issue of ocean acidification caused by the buildup of CO2 in the atmosphere…a problem that we still don’t have a very good understanding of yet but that some think could be almost as serious as the climatic effects.
That said, there was a recent paper by Thomas Wigley in Science proposing that some sort of scheme for injecting sulfate aerosols into the upper atmosphere be considered. However, he was proposing this only as a “stop-gap” measure and was also proposing to do it in such a way that hopefully the negative pollutant effects of these particles when they are in the lower part of the atmosphere would be minimized.
(I think you meant “Swallow the spider to catch the fly”)
Whoops…Thanks, Rysto! I believe I did. That’s the way it usually goes isn’t it? (We need a biologist to find out if there are any spider-catching flies out there.)
mmmm, cola powered plants.
Tasty, but not as intriguing or cute as koala powered plants.
Sulfates have too many negative side effects. But some other, inert material would help a lot. Personally, I think something like silica particulates would work (basically, ultra-fine sand). Direct exposure to humans probably isn’t safe, but the environmental damage would be minimal.
It could be injected into the stratosphere through solar-powered chimneys. Or, even by airplanes (imagine every commercial flight releasing 100kg of particulate). Cumulatively, it would add up.