[bjmarte]

Anybody with knowledge and evidence to answer a couple of questions from a very non-expert that were raised in my mind after reading the pdf and then the comments here?

1) It is the statement in the paper true that CO2 loses it's warming effect as concentration goes up?

2) Although I'm fuzzy on the warming, I'm pretty convinced we are killing our oceans. Still a little fuzzy on the exact mechanism though. If the oceans are acidifying from atmospheric CO2 (as opposed to fertilizer runoff or some such) is there evidence of this problem earlier in our planet's history when CO2 levels were much higher?

These are sincere questions hoping for informed answers.