I'll answer with a question: Has artificial anything ever been good for the environment?
I think I would say it is unwise. Bad is subjective. It may be good for some things and bad for others.
Use of dry ice or silver iodide would have really small direct effect on the environment. If they work they could cause problems (too much rain one place or too little at another), but it is questionable whether they really work or not.
No, but it's not good either, it basically does nothing
Manipulating the weather basically (artificial weather).
