When already decommissioned fossil power plants get reactivated to mine bitcoin, I think it's safe to say that a ban of cryptocurrencies would have a significant impact.
I’m aware of only one case where a fossil fuel power plant partnered up with crypto miners. But I’m not denying PoW’s environmental impact, just its comparative scope and scale. Do you think we should ban other technologies reliant on dirty energy, such as motor vehicles? The Internet?
Presumably you believe the benefits outweigh the drawbacks in those cases. If that’s the case, crypto (PoW, really) would then chiefly be guilty of not being sufficiently beneficial to justify its contribution to climate change?
Sadly that won't solve the problem. If 99% of Bitcoin is locked up in sidechains, the free 1% will become the new Bitcoin, so each Bitcoin will be far more expensive. As long as the price of Bitcoin rises faster than the mining rewards reduce, people will keep mining it.
And if you think that people dump a coin just because all the use cases have moved onto new coins, I present for your comment the "Ethereum Classic".
