IIRC, the charge distribution in clouds is caused by friction of the ice crystals within it. Why should there be any charge distribution in the first place? First off - how does friction charge up an object? Then, why should the uneven charge distribution not neutralise itself? The opposite charges in a charged cloud should just attract each other and discharge...not form a coherent structure where the lower side of the cloud is positive and the upper side negative. Thirdly, when electrons arc up from the earth to discharge the positive side of the cloud, what about the net positive charge the Earth now possesses and the net negative charge the atmosphere now possesses? Articles about lightning say that it is mostly made of electrons shooting skywards, so what other mechanism discharges the new Earth-positive and sky-negative distribution?