[jamesqf]

Originally Posted by Arragonis

Yep - greater extremes than now were in play.

Sure, since there's about a billion years to look at. Now ask yourself whether those extremes would have been pleasant times to live in. Most relevantly, we have an instance of global warming which, as best we can tell from the evidence remaining after ~250 million years, was due at least in part to the burning of large coal beds. That event - the Permian/Tertiary Extinction - killed off some 70% of terrestrial vertebrate species. Being that I am myself a terrestrial vertebrate, I don't care for the prospect.

The rest of the non-CO2 related temperature excursions are largely irrelevant (except as they tell us things about the climate in general), because we KNOW beyond any possible doubt that humans have increased atmospheric CO2 concentrations beyond their normal levels.

Wrong. If it was as simple as that the models predicting temperature would be spot on which they aren't.

But the models ARE pretty much spot on. As for instance Hansen's "Scenario B", which comes fairly close to what actually happened - and comes closer still if you go back and plug in actual CO2 increases instead of the guesses made back in the '80s. And yes, I know you can find some denialist sites that claim Hansen was wrong. If you examine their claims, you'll see that they are lying.

You misunderstand my motives - 1) credibility in the science needs to be rebuilt after some bad episodes.

Not true. Sure, the above denialist sites have tried desperately to use a few out-of-context quotes and such to create an impression of a lack of credibility, but the only people who believe them are the confirmed denialists.

Maybe you don't agree but for example CAGW was not mentioned in the US election...

Why did it need to be mentioned? You had one party running a pair of (excuse my language) effing creationist idiots, backed up by Senate candidates mouthing off about things like "legitimate rape". And notice that they lost :-)

Also 2) it would be useful to know what prevention / mitigation steps may be needed, what will work and what will work best. And 3) the models could be improved

Of course anything can be improved, but if you've just fallen off a cliff, do you really care that a detailed model that takes account of the variability of air resistance with temperature predicts you will impact the ground in exactly 5.328 seconds?

Prof. Mann has never released all of the code citing IPR, and has withheld quite a lot of the data - so it remains a black box.

So why should Mann have to release his work to gratify denialists? Especially when their primary motive seems to be to keep him and other climate scientists so busy responding to their harassment that they won't be able to do actual work? Plenty of similar data is available, and when analyzed shows similar results, which is a far more robust confirmation than picking apart one study that you disagree with.

Again given all of the code and data hasn't been released, how do we know ? Maybe Open Source it ?

Plenty of open source climate code out there. Look up EdGCM, for instance.

Would that be a reference to Professor Muller who thinks other climate scientists were "guilty of fraud" and Al Gore is a "science denier" ? No really he did say that - listen here.

Sure, he thought that. Then he actually looked at the data, discovered that he was wrong, and was honest enough to admit it.