> way ... that doesn't either have horrendous externalities
The CO2 emission externality need have nothing to do with Bitcoin or any other proof-of-work chain. Tax carbon at whatever level makes sense and Bitcoin will adjust. (As I understand it, even currently Bitcoin mining mainly uses renewable energy, because it's cheaper; and it's trending cheaper still.)
The externality is at the power plant, not the use. Banning a use is like basing your server's security on client-side Javascript.
> Tax carbon at whatever level makes sense and Bitcoin will adjust.
> The externality is at the power plant, not the use. Banning a use is like basing your server's security on client-side Javascript.
How would that work? Applying the same carbon tax on farming as on bitcoin? You always need to differentiate on use. Otherwise we could also just have a single income tax and be done with it. However taxing food as much as a Ferrari doesn't really make sense.
The whole purpose of taxing carbon is to reduce carbon emission to the efficient level and shift energy consumers away from uses that are not worth the cost in carbon emission.
Say you're a bitcoin miner powered by a coal plant. A carbon tax is imposed. The price of your power goes up. Your competitors, powered by solar, are unaffected. Maybe you keep going at the higher price; more likely, if the tax was set at anything like the genuine externality, you shut down. Possibly you keep going for a while, winding down your ops at this location but moving any new ones to find affordable power. Sucks to be you if you didn't anticipate the tax (which seems implausible, they won't announce it effective next Monday), but Bitcoin itself will hardly notice.
Say you're a farmer also in coal-plant-land. Aren't farmers powered more by internal-combustion engines than grid power? That should be carbon-taxed too in this world, and that's good: you want farming, where it's climatically most expensive, to shift to less-CO2-costly methods and crops. Farming spends energy on a much wider set of tasks, some of them more essential to the output than others, and some outputs more inelastically demanded than others. For some of them you adjust, for some you continue and pay the higher price. The ones you adjust were not worth the carbon cost; the ones you don't were. You have to charge your customers some amount more, depending on how essential the coal turns out to be in your case. Maybe, like the bitcoin miner, you stop farming, or shift to some sort of less-intensive organic farming; maybe you don't. Either way, it's more likely the right decision for the planet! We stopped pretending that dumping carbon is side-effect free.
You don't "differentiate on use" by politicians and bureaucrats deciding what's naughty or nice. They don't even know! It's an incredibly complicated problem! They further have no real incentive to do it even vaguely right, rather the opposite: any competent politician can look to the public like they're public-spirited while favoring concentrated interests. Was the FDA just stupid for banning the J&J vaccine the other day? No, they're fundamentally misaligned with the public interest.
The CO2 emission externality need have nothing to do with Bitcoin or any other proof-of-work chain. Tax carbon at whatever level makes sense and Bitcoin will adjust. (As I understand it, even currently Bitcoin mining mainly uses renewable energy, because it's cheaper; and it's trending cheaper still.)
The externality is at the power plant, not the use. Banning a use is like basing your server's security on client-side Javascript.