One of the most complex problems of man-made climate change is what our activities are doing to the clouds and rainfall. Certain generalities apply – the warmer it gets, for example, the more energy and moisture there are in the atmosphere and the weather gets more violent.
Another factor is pollution. Traffic, factories and forest fires pump vast quantities of particles into the sky that would otherwise not be there. Around these particles droplets of water form, become clouds and eventually rain falls.
Source: Guardian Environment