this on agw from a physics professor, page-8

About William Happer.

The lesson is - firstly don't believe everything someone says about themselves - this guy is not a climate scientist. He is a physicist and a radiation specialist (so should know better) but his other affiliations are more relevant here. He is on the Board of the George C Marshall Institute which was established to lobby for Reagan's Star Wars and then for manufacturers of tobacco products. He sounds like he knows nothing about atmosphere or climate, even saying that CO2 levels were much higher than when humans evolved (CO2 was much less than now when humans evolved).

Doesn't mean he's wrong just because he's not a climate scientist (climate scientists can be wrong too). But as with anyone, you have to check what he says is consistent with scientific facts before you pay him any mind.

For starters, he uses an arithmetic progression to estimate how long until CO2 gets to double. But even looking at the CO2 trend any fool can see that it's not a straight line progression. In any case, the amount of CO2 in the atmosphere depends on how much we put there - and we're putting more each year at the moment. It's better to use economic and technological scenarios to project how much more CO2 we'll be shifting up into the air.

As well as that, as others in this thread have pointed out - he doesn't take account of the feedbacks.