Agreed. It would certainly cause a significant increase in the extinction rate, on the order of hundreds of thousands of times the background rate. (New species will evolve to fill the niches left by extinct species, but that will take millennia.) Also agreed. Or someone ignorant of the effects - which most people are. As I have mentioned in the past, if that is true, and you no longer feel the need to speak of or worry about it - you'll be helping the cause of reducing the long term problem of AGW overall.