"If Al Gore were so profoundly afraid of climate change, he wouldn't fly in a private jet or have a huge mansion with massive electrical consumption. Since he does those things, then he's obviously not convinced that human activity affects climate."
Nobody is claiming that climate change is a threat just because Al Gore says so, so the sincerity of his belief is irrelevant. Politicians are not the ones "selling the world" on climate change; they're the ones being persuaded (to varying degrees) by scientific evidence of a man-made threat, and they're in a position of power to do something about it.
As for what happens when politicians don't pay attention to climate change, just look at Florida: http://www.washingtonpost.com/news/morning-mix/wp/2015/03/09... Their senator and governor don't believe global warming exists, and they're already having to deal with rising sea levels. It's the politicians who don't take action that are harming their constituents, not those who do.