The freedom flag dickwaving Arksy (I honestly have no idea which is the real one) would say that the only wrong is to stand in the way of an individuals right to act. Removing hindrances on individual action is always right. The initiation of force is the root of all evil. Voluntary action is the only moral solution.
The great thing about climate change is that it's literally impossible to fix in a libertarian utopia. It completely invalidates the world view of the supremacy of the individual, hence so many deniers are from that side of politics.
I'm nowhere near that hardcore. I do think the initiation of force is fundamentally immoral, but I understand that for practical reasons, it's absolutely necessary for a peaceful society. I'm hardly a "proper" libertarian, and I usually find that their complete stubbornness and unwillingness to compromise on anything, even the mildest things that may be against their principles completely trite and annoying. I also find it completely absurd that they spend so much of their efforts on generally unpopular things like legalising drugs, and not on highly popular policies like reducing taxes.
I honestly think it's ok if governments step in to account for externalities where the market can't or won't account for them. I think we should be cautious when we do this, but I don't have a problem with it in principle. I don't mind an ETS in principle either.
Also, despite spending two years under the tutelage of Ian Plimer, who is Australia's leading climate change denier, who spent a fairly considerable amount of lecture time "debunking climate change", I do agree with the mainstream scientific consensus.