If the price of Bitcoin continues to climb, the total energy consumption of the system will increase proportionally at least until 2020 when block reward halves. It is not unlikely that at this point the price of Bitcoin will have increased so much that energy consumption will be unsustainable in a way that Bitcoin will be opposed by a large proportion of global society (we are still below 1% of total electricity consumption but a 10-fold price increase could change that quickly).

I see the same options that are laid out in [this article](https://arstechnica.com/tech-policy/2017/12/bitcoins-insane-energy-consumption-explained/):

1. Bitcoin will be abandoned and people just use something else
2. the protocol is changed to reduce the block reward earlier than 2020
3. the protocol is changed to exchange Proof-of-Work for something else (maybe Delegated Proof-of-Stake?)

since 2 and 3 will almost certainly result in a fork, they are related to 1. I feel that a solution will have to be found, I'm just wondering if I missed another option and which of the options is most likely.