Giant Mirror

Being that my homepage always opens to Reuters, I am able to get the latest news/oddly enough items. Opening the page just a few minutes ago, something shocked me that is being considered as a plausible solution to global warming. The idea is this: lets place a 3000 tonne mirror-like structure out into space in order to reflect some of the suns rays away from the earth. Allow me to ponder this thought for a moment. Someone wants to take 100 space shuttle flights over 100 years to assemble a giant mirror up in space to combat a problem we are facing now. Gee, don't let everyone immediately jump on that bandwagon. What are the potential hazards of this giant structure orbiting around earth, covering the suns rays?? - It could fall out of orbit and come crashing down out of the sky, killing thousands of people, it could inhibit plant growth/farming if the mirror stays over an area for an extended period of time, it could shift the seasons, it could be hazardous for other space missions in the future, etc etc. There are numerous potential hazardous things that could result from placing a giant mirror into space. Not a good idea. At best this ginormous orbiting object could ward off the suns rays for a short period of time, resulting in temporarily lower temperatures. I'm just glad that I will not be around when this mirror starts its orbit.