The very notion that the climate will
amplify CO2 heating by as much as 4.5 times should raise red flags. Without all that extra heat amplification there is no global catastrophe and therefore no drama. There are lots of papers on climate sensitivity and the estimates are all over the map. This should indicate less certainty, not a "the science is settled" attitude.
Rather than acknowledge the uncertainty, climate scientists like Michael Mann appear to be trying to create the illusion that their climate models are more accurate than they really are. For example here is a slide from a 2012 presentation he gave: https://climateaudit.files.wordpress.com/2013/03/hansen1988-...
Notice that he simply lops off the temperatures after 2005 because they don't neatly fit the curve! It's bizarre to see. It's this sort of behaviour from climate scientists that initially piqued my skepticism.
When I first started looking into the CAGW debate with any scrutiny I honestly believed I would find skeptics using fake data pumped out by right-wing think tanks. Instead I found what appears to be fake data pumped out by government agencies. Go figure.
Don't get me wrong - I don't think these individuals are pumping out fake data on purpose. For example, they may believe in global warming so strongly that when the data doesn't show the expected warming they a) wonder why the data isn't showing more warming, b) come up with a plausible sounding reason as to why the data isn't showing more warming, then they c) 'fix' the data via a series of 'adjustments'. Also known as confirmation bias and group-think.
It turns out that a significant portion of the recorded warming is due to these data adjustments. We're talking as much as 20% or more, depending on the data-set. That should also raise some red flags.
Been meaning to get to a better reply. As to sources, in the case of temperature adjustments, it's all there in the mainstream data-sets. I could point you to some skeptical sites that are picking the data apart if you like. There are some newspaper articles on this, all right wing outlets of course. It seems both sides only print the stuff that caters to their audience.