Rothlisburger and Brady vs Manning and Romo?

Somebody explain to me how we can possibly compare QB stats between the Peyton Mannings of the world and Tony Romo's, who get to play their games in a comfy dome, to the likes of Brady and Rothlisburger who have to play outdoors, in the rain and snow and freezing cold. Look at last night, while Peyton Manning is throwing 5 TD's in his dome, Rothlisburger is playing in a swamp, or Brady in 10 degrees. And to add to it, the NFL schedules most of Indy's outdoor games in Sandiego, or Jacksonville in the late seadon when it gets cold. You would have to think that if a cold weather, outdoor QB can break old Peytons records, he actually shatters them, it's like comparing apples and oranges.