The reduced pollution would probably reduce at least some of the health care costs. Plus we spend way too much on wars and killing people ("defense"). Use some of that money first.
Yes. It would be tragic to cut out polluting forms of energy production that destroy rivers and lives.
That's not first and foremost CO2, though. Many other forms of pollution tend to be far worse to local environment. Addressing those might involve things like catalytic converters on ships and the like.
That money has to come from somewhere. It could be spent on healthcare, getting people clean water, etc.
To me that would be a tragedy.