Currently, the information we have on the effects of aerosols in the air is somewhat ambiguous. Quantitative data on the actual amount of temperature and weather change that can be attributed to aerosols is hard to come by, and the result is that there is still debate on seemingly basic matters such as whether aerosols actually bring about global warming or cooling, where in the world aerosol levels are undergoing the most drastic changes, and exactly what percentage of aerosols is the result of humans as opposed to nature.
Aerosols are necessary for cloud formation, and the concentration of aerosols in the atmosphere can affect everything from cloud precipitation and lifespan, to sunrises and sunsets.
In the atmosphere, water droplets cling to aerosol paticles, allowing clouds to form. If there is a higher amount of aerosols, the water has to attach to a greater amount of particles over a wider area. Because the droplets are more spread out, it is harder for them to form clusters that are heavy enough to fall down to earth as rain. Another effect of these smaller water droplets is a greater amount of sunlight reflected away from earth's surface. Because smaller water droplets reflect more light, clouds with a higher concentration of aerosol particles will reflect light back to space without ever allowing it to reach earth- this may result in temperature cooling.