Look at it this way we know that PoW is wasteful as hell and because of that causes external issues on a huge scale. If we don't try to work out what those issu

Look at it this way we know that PoW is wasteful as hell and because of that causes external issues on a huge scale. If we don't try to work out what those issues are and how big their impact is how would we ever deal with them? Putting our heads in the sand won't make them go away and the link details their methodology and results if you wish to quibble with them. Particularly as it addresses estimate accuracy directly. More generally the whole external cost of PoW is definitely a case of techno-utopianism meeting the real world and a lot of proponents wanting to put on blinkers even though this study shows that crypto-currency is currently a net social positive. Literally any indication that it has any negative outcomes elicits very strange responses.