Sorry, it was more for your "opinion" on PoW, not the carbon tax.

> This would immediately make unproductive energy use (cough POW crypto cough) a lot less profitable,

You seem to have just one target in mind that would get hit. Clearly you haven't analyzed the full extent of a "carbon tax" and your following statement seemed very naive. That said, I'm all FOR carbon taxes, it is actually good for Bitcoin and the world.

I don't think there will be a LOT of PoW cryptos, there will be one (or two at most) winner and the others will use a variation of Proof of Proof (by saving state on a PoW chain). I also think that the energy usage curve will plateau soon-ish and energy usage will be somewhat constant or start trending down gradually (as the rewards are tapering off too).