1 part out of every 2,500?
AHHHHH! Global Inferno!
Per usual, not the point. It's the increase that's important. Your comment would only make sense, if CO2 had no effect on temps at historical levels. Since we know that if the earth had no CO2 we'd be degrees colder, your comment is a FAIL. It makes as much sense as saying a drug has wouldn't have much effect because the actual amount in a pill is a small percentage of the total weight, as if the inactive ingredients counted.