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Neither, I think. I mean, your question seems to rest on an incorrect presupposition about what the paper's about. They're not trying to judge people for their opinions or how they reached them. They're saying "here's a topic with a lot of misinformation flying around; let's see what we can do to make people less likely to be persuaded by the misinformation".
Well, the authors clearly hold that global warming is real and that the evidence for it is very strong. Does that invalidate the paper for you?
Even if you grant that global warming is real that doesn't mean that there also isn't a lot of misinformation on the global warming side.
If I quiz a random number of liberal on the truth as the truth has been found by the IPCC, there are many issues where the liberals are likely saying that specific scenarios are more likely than the IPCC assumes.