Energy cost of mining Bitcoin more than twice that of copper or gold
theguardian.com
theguardian.com
Metal mining has a comparably wide variation in energy intensity, though not mentioned in article. The headline's broad-brush claim deserves skepticism.
All of these "We must stop Bitcoin to save the environment" articles that have been popping up kind of seem like sour grapes.
Also, amount of energy expended is directly proportional to price (x block reward) - if you want to reduce Bitcoin's emissions, short it hard!
Like with every other good in existence, such a tax will affect the amount -- and by which energy source -- it is profitable to produce [1].
If there is a place where it is possible to avoid such an imposition, then production will leak to that location, just like for every other good in existence.
If you think that bitcoin is somehow "different" than all other trivial things that people spend energy to produce, because you think it's stupid, you're opening a can of worms I'm sure you don't want to deal with (deciding how much people "really should like things" compared to their energy cost).
[1] Technically, it will affect the production of hash computations, not bitcoins themselves.