Cloud drops and ice crystals form in the atmosphere with aerosols as nuclei. The clouds in turn have a large greenhouse effect on the planet and a much larger cooling effect by enhancing the planetary albedo (the Albedo effect) and the net global cooling effect, the cloud-radiative forcing, as determined from satellite radiation budget measurements is about -18 (±5) Wm-2. Thus we can conclude that the aerosol-cloud-radiative interactions have a large net cooling effect of about 18 Wm-2. The problem we are now facing with respect to climate change is the role of anthropogenic aerosols in the anthropogenic radiative forcing.. Based on satellite data and emission inventories, we have increased aerosol concentrations in the atmosphere by about 50% to 100%. Climate models estimate that the cooling from the aerosols (including their effect through aerosol-cloud interactions) is about -1.2 Wm-2, which seems very small compared with the 18 Wm-2 from all(natural and anthropogenic) aerosols. Intense efforts to understand this aerosol-cloud-radiation interaction has led to a major reassessment of our understanding of aerosols effect on climate. We now know, that aerosols, directly through their radiative effects and indirectly through their interactions with clouds and precipitation, influence the dynamics of the atmosphere and the ocean at scales ranging from an individual cloud to tropical hurricanes, monsoonal circulation and the inter-tropical convergence zones. They also have large impacts on tropical sea surface gradients, which in turn impact the Hadley circulation. Thus what started out to be an aerosol-radiation problem has matured into a full blown problem in understanding the general circulation of the atmosphere. My talk will take a travel through this exciting and intellectually stimulating journey.