Mariss
To state that the weather has varied a great deal in previous epochs is doubtlessly true. But that doesn't negate the possibility of human activity causing global warming. I doubt we know enough to know for sure, my guess is that it's having an effect. I really don't think all those scientists are just trying to garner research grants although some probably are. Also the folks who say it isn't happening probably have an interest in doing so as well. If only to assuage their conscience for driving a Hummer. When the best minds out there are saying it's happening you have to consider the possibility that it is.
Donna