I do believe there were plenty of warning signs--- Like when it was exposed that his house uses something like twenty times the energy of a normal home.. or when he bought a second one (by the ocean)... or when they used CGI footage in his film... or his private jet use..
I'll be surprised if he ever turns up in public again, but hey, he managed to create a problem and profit from the solution. It's not his fault anyone actually fell for it.
I've always wondered about the chart in An Inconvenient Truth showing historical temperatures and CO2 levels. Critics have said he presented the sequence (and thus causation) backwards, i.e. he said temperature follows CO2 but the real sequence is CO2 follows temperature. (The causation for that would be, as oceans get warmer, they release CO2 faster than at lower temperatures.) I haven't looked into that aspect of the film carefully enough to know.
Never understood why Conservatives are so hell-bent on ever considering that all of the crap we spew into the air just might.... just 'might' cause a problem someday and then go on to try and find any shred of proof that there really isn't any problem whatsoever so they can ( I guess) feel relieved?