Is this from the Pandorapedia or something? I wasn't aware that we were shown all of the human facilities on the planet or in the solar system. It implies impressive fabrication facilities, sure, but where are we getting replicators from? (Unless this is another extrapolation of their mystery antimatter technology?)It isn't just that though; they have extremely advanced automated manufacturing that approaches Star Trek replicators in capability. The ruggedised lightweight cut-down plant on Pandora can crank out all the equipment they need from mining spoils.
How does cheap energy alone solve this problem? Such a contraption would also be resource- and expertise-limited. Also note that CO2 is only one pollutant, and that we don't really know how mature nanotechnology is in this universe (or how resource-limited it will eventually prove to be).Imagine what the factories on earth can do - and not just that, since relies on fairly mature nanotechnology to work all kinds of other applications should be possible. Including making environmental cleanup much easier (e.g. it literally becomes practical to just suck all the pollution out of the air, hell with that much energy you could just liquify any surplus CO2 and shoot it into space).
I'm not an expert here, I'm just wary of "if cheap energy then X" claims.
One further thing to keep in mind...right now, no DELIBERATE geoengineering project has ever been undertaken, and I just read an article in Science that was essentially arguing "there is no experiment that can successfully model geoengineering, the only way to know what will happen is to try it." A civilization like the one we see in Avatar, heady on unobtainium fumes and diamond-plated fusion reactors, might have tried to suck all the CO2 out of the air and killed half the plant life on Earth for all we know. Which is why no one's trying to suck the hydrogen sulfide out of the air on Pandora, I suppose.
In any case, this is somewhat beside the point. I would argue that aspiring to make a sci-fi film about future Earth that doesn't address environmental problems is borderline irresponsible. Including interstellar travel in your movie shouldn't preclude an environmental message. (And just be glad a lot of Cameron's original ideas about actually showing us Earth-as-total-dustball didn't make it into the finished film. I didn't read any of the weird Pandora-worshipping from the supplemental book into the characters of the film itself, and you'd think such a situation would make it politically impossible for the RDA to do everything they do.)