They are back-of-the-envelop, no feedback modeling nor post-implementation consequences.
They are fine for a sci-fi novel.
As real projects they are insane.
Their real purpose is to help us avoid thinking about the things we already know to do but won't do, because they are inconvenient or unprofitable. Band-aids for cancer.
I am beginning to think our impending financial collapse is our real hope. The harder we crash, the less we will be destroying our environment. Personally, there is a lot to dislike--even fear--about this course of events, but in the long run it offers the best possible outcomes. The Fates are kind.