Clean Air Might Intensify Global Warming

Yeah it's actually pretty well-established that aerosols (like sulfur dioxide [SO2], not like the aerosols from hairspray cans) block sunlight and cause global dimming and cooling.  That's actually thought to be the primary cause of the slight global cooling between 1940 and 1975.  Though there is still some uncertainty as to exactly how much of a cooling effect anthropogenic aerosols have.  But models that incorporate both aerosol cooling and CO2 warming are the most accurate.

So that is a bit of a problem.  We want clean air, but by cleaning the air, we reduce this cooling effect, thus causing further warming.  There are also the people who argue the planet hasn't warmed all that much - it would have warmed significantly more by this point if not for these SO2 emissions.

The geoengineering proposal to pump a bunch of SO2 into the atmosphere is viewed by climate scientists as a last ditch desperation measure if CO2 emissions reductions are insufficient.  It's basically if we have to choose between catastrophic climate change and pumping a bunch of SO2 into the atmosphere, the latter may be the better choice.  But it's a dangerous proposition.  It will likely cause acid rain, probably have very negative consequences for plant life (reduced sunlight reaching the surface), solar energy will become ineffective, and who knows what other unexpected side effects will occur.  Geoengineering is always a risky proposal.  That's why pumping CO2 into the atmosphere, which is really just another type of geoengineering, is such a problem.  It's just a bad idea to mess with the Earth's climate system.  So the best solution is obviously to stop messing with it, stop pumping so much CO2 into the atmosphere, and hopefully if we succeed we can avoid catastrophic climate change.  But if not, these more radical measures may become necessary.