It has always looked to me like those who believe that humans can have an effect on our global weather have absolutely no idea of how puny we humans are when compared to the energy and power contained in and expended by naturally occurring events.
To get an idea of just how puny we humans are when compared to naturally occurring events have a look at this article.
http://science.howstuffworks.com/environmental/energy/energy-hurricane-volcano-earthquake1.htm