It's huge. There's a phenomenon in Asia, they call it the Asian brown cloud, or more generally it's a continental brown cloud. It's a mixture of soot, carbon dioxide and aerosols. It comes from burning cow dung, wood, and other biomass. It's more often referred to as black carbon. The global estimates run from about 30% to 55% of the strength of the carbon dioxide alone forcing on our climate.
It has five major impacts on the climate. It absrobs solar radiation in the atmosphere, and heats the air by convection. It also absorbs infrared radiation, the solar energy that is absorbed and emitted by our warm planet surface, just like a greenhouse gas. It decreases the reflectivity of snow and ice it lands on, absorbing more solar energy in the process. The small particles get into water droplets, by nucleation, or scavenging, and will heat the water droplets. Lastly, the warming of the lower atmosphere by this form of pollution can evaporate lower atmosphere clouds, which will allow more sunlight through, enhancing warming.
The poverty in Asia means that they can't afford cleaner fuels, and perversely the poorest often suffer most from the haze and smog alerts these clouds lead to.