I would be less ambitious than saving all the humanity. Just saving those who believe me would be much :-]

And that brings to the point of information - how people should be informed or warned? You need big money against Rupert Murdoch's media universe, big determination to counter libertarian think tanks, and inspiring image. Just a book for "echo chamber", or another Hollywood production of "The day after tomorrow" will not do much.

One political strategy would be Winston Churchill's: he was (relatively) marginalized in the 1930s, among other matters because of his "stubborn" anti-Nacism, but when the war did broke out, he was the most suitable leader. In the same vain, Cassandras should not be afraid to look ridiculous, but make they stand and get ready to take a lead. Preparation is the key; disaster capitalists won't give reins for free. As Naomi Klein indicated in "The Shock Doctrine", they know very well how they need to act in a crisis. We should know well as well.