Earth & Sky has a few interesting articles about recent developments in our understanding of how aerosols affect our weather.

I saw this one which explains a little more about haze first.  It turns out that the bulk (2 thirds or so) of haze is not caused by the visible particles you can see in exhaust but is instead caused by the invisible aerosols which quickly merge with other compounds in the air to cause the haze.  After reading that article I looked through some of their older related articles. 

I’ve heard of this before but it is something good to keep in mind.  Aerosols cool the planet by reflecting sunlight back into space.  This means that as we clean up the pollution we spew into the atmosphere we have to consider how reducing the aerosols will affect the global climate.  Michael Mishchenko at the Goddard Institute of Space Studies in New York has performed a study that shows that aerosols have reduced by 20 percent since 1991.  That could explain why the Earth is warming faster than climate models had predicted.  At least, if they didn’t take into account the effect of reducing the aerosols.  Another article at Earth & Sky mentions that scientist Lorraine Remer of the Goddard Space Flight Center has shown that aerosols counteract 20 - 30 percent of greenhouse gas warming.

Mark Jacobson at Stanford University has stated that aerosols also tend to slow down the wind which reduces evaporation and therefore rain.  He says that in California the aerosol pollution reduced the water supply by about two to five percent.