You can explain or justify the costs however you like. That's not the issue. I'm not making any claims as to the suitability of spending more or less into renew

You can explain or justify the costs however you like. That's not the issue. I'm not making any claims as to the suitability of spending more or less into renewables, just pointing the obvious but often forgotten consequence, that every dollar spent here is a dollar you can't spend in another place. Swapping to renewables at once would have an impact that can very easily overshadow any remediation costs. Even tiny cost increases now will produce vast difference 100 years forward due to compounding. Just as a thought experiment, if the costs of switching to renewable energy are >0.72% of GDP, and the remedial costs are around 18T$ (in today's money) in 100 years, you're still better off not switching to renewables.