Knowing about the past is one thing, the future is much more difficult (if not impossible). We can project with our models what conditions will be like in the future. With that, there will be margins of error. Anything we do now will fall within those margins of error, so anything we have done will be of unknown consequence.
In addition to the vast costs measurable in dollars, there will be unmeasurable costs. How do you measure the losses to people's (especially the masses) ability to freely choose how their efforts are spent? Aesthetics are also important. I drove by Palm Springs recently. The wind farms there are a blight on a huge area. Unlike powerlines, you can't bury a windmill.
There are other problems. Unless we cede authority to global powers, how does anything get done? Who is forced to comply and who is exempted for whatever reason? How is that force effected? What are the intangible costs of those things?