Honestly mate, what ridiculous melodrama.
There are no credible predictions which could lead to human extinction. In fact I would go so far as to say that human extinction as a result of climate change is actually completely impossible.
Worst case, absolute worst case, we see very significant sea level rise, loss of low-lying regions and changes in habitat. And that assumes that faced with such catastophe, we decided to just sit back and let it happen. As opposed to deciding to do something about it - such as truly enormous carbon sequestration plants; algae farms on truly gigantic scale, for example - which of course we would do if things became truly calamitous.
It took one country less than a decade to put a man on the moon when they put their mind to it. And yet we're belng asked to believe that the combined efforts and resources of the entire human race could not find a solution to fix an impending climate catastrophe?
It's a ridiculous suggestion. We are not just going to sit back and watch ourselves become extinct. The reason more is not being done (yet) is because it isn't an impending catastrophe yet, and may well never be. If it becomes so, we'll deal with it.