Actually, it's difficult to determine exactly how we're altering the environment. Detailed data about historical weather patterns becomes exponentially less accurate as we step back in time. There isn't any doubt that we've altered the environment. The argument is whether we've altered it enough to make a difference. The problem is NEITHER side has enough accurate data to support either opinion.
It's best to take a neutral position in this matter. The only facts we have is that we're often confident in our opinion, but we're also often wrong, too. Taking one definitive side or the other is just an indication of emotional bias in the argument, and nothing more.