>The thesis of this "scientific paper" is basically like a couple of tokers sitting around in their parents' basement saying "DUUUUDE... what if the money in our savings account DOUBLED EVERY YEAR?!???
Again this is not a critique of the paper, it is a critique of tokers sitting around in their parent's basement. There is no substance in your criticism to address, it really is just an expression of your feelings toward the paper's author. Aside from the fact that you're just name-calling, the numerical basis you've used for comparison is just wrong.
Now it so happens I have you at a disadvantage: I've actually read the paper. It's closer the tokers sitting around saying, "How can we achieve a 7% annual compound interest rate sustained over ten years with our portfolio," which is roughly what doubling your money in ten years takes. The authors are talking about what it would take to half carbon emissions which would be a 6.6% reduction each year, and they discuss methods for reducing them, which they break down into near term no-brainer, near-term difficult, and long term speculative. As is usual the further out you go the less concrete and certain you can be. This is normal in economic projections that go twenty or more years out.
Now you may disagree with the specific means proposed, some of which are quite drastic (e.g. attempting to recover external costs through inheritance taxes). But there is nothing inherently irrational about starting with a goal -- zero carbon emissions by 2050 -- then asking what it would take to achieve that. Nor is there anything inherently ridiculous with coming up with the answer that it'll take a mix of things, some of which looking twenty or more years into the future we can't predict yet.