Start by over half a century of FAILure of catastrophist predictions - complete failure, none have come to pass. And look at the behaviour of types like David Sleazuki who removes his web pages when challenged on facts, he and alGore jet around spewing CO2 and leaving lights on in mansions - hypocrites.
What did you say about ‘credibility’? Having fun yet?
Then go to friendsofscience.org for explanations and links to solid data and research.
And my page wclimate.pdf on moralindividualism.com, to which I will add basic physics of ‘greenhouse gas’ molecules showing CO2 cannot cause much warming.