[hobofan]

YES, we know! If there truly isn't an alternative to PoW, yes then we are pretty much fucked. Quite a few more efficient alternatives are currently being tested (and I guess a lot more are to come), and it looks very promising.

[tim333]

Of the top 8 coins on coinmarketcap I think four don't use proof of work - ripple, cardano, stellar and neo. So there seem to be alternatives.