Explanation:

Aerosols are suspension of particles in the atmosphere via both human-made and natural sources. E.g. Volcanic and desert dust, sulphate from coal. They offset warming from greenhouse gases because they send some of the sun's radiant energy back to space exerting a cooling influence on Earth's climate.
A good monsoon, which is produced by the difference in temperature between land and sea, is thus weakened by aerosol accumulation.