You seem to be fool yourself. Greenhouse gases bring in long term problems. They remain in the atmosphere for 200 years and cannot be controlled quickly. So if we start reducing greenhouse gases still it will take long time to eliminate existing one from atmosphere.
Contrary Brown cloud is temporary but dangerous. They have immediate effect on glaciers. So if brown cloud keeps building up it can have devastating effect on entire population. The good news is that we can stop production of brown cloud quickly bring in whole thing under control and hence eliminate its effect.
They both are bad for us. One have long term effect and wider area is covered for its devastation. Second one has short term and regional effect but its intensity is high.
