It's not common sense to everyone. I don't believe in global warming. Every single thing that the rabid environmentalists say has been seen in the past. Before industrialization even.
My favorite example was in the 80's there was a breed of frog that was known for being susceptible to changes in the environment. They nearly went extinct. The environmentalists blamed global warming and other pollutants.
Then the very next year there were a billion of the **** things.
It's how nature works. Tons of predators eat all the frogs. Frogs nearly die out, predators have nothing to eat, they die out. Then without the predators, the frogs population grows. With all the frogs, there are more predators born and survive....
Heck, in a tousand or two or twenty years, our north and south poles will swap. The magnetic field does this every billion or so....
Global warming (In it's current state of panic) is just that. A panic. Sure, I am positive that we have an effect. The question is to what extent really. Remember the "ZOMG HOLE IN THE OZONE!!!!!"? We as a world put out more CFC's than when it was first noticed. Guess what. It never changed size after we noticed it and it grew. We didn't change. Mother nature did.
There is a metric crapton of information we don't know yet and some that we know is wrong (Always is something).
Should we be concerned about pollution and stuff? You bet. Fear for our lives because of global warming? I'm not so convinced.