I think crypto could be regulated in a number of ways to make them more energy efficient. But that is under the remit of national governments.
So let us suppose the UN debates the problem and unanimously calls on national governments to implement controls. Leaving aside the underground, unregulated by design, nature of the beast, how many decades before anything significant can be achieved? The first world climate change conference was in 1979.
It's only really bitcoin that is super wasteful. Some other protocols are pretty efficient - but significantly they are not provably as secure.
And Bitcoin is by far the best known and most popular
If it doesn't all collapse in the next year, what we will see is significantly more efficient mining technology and many thousand times more transactions possible on the same infrastructure. I think it's approaching peak wastefulness
and yet the number of transactions rises inexorably, as does the cost per transaction. And the price and the profile among the public. It's not mainstream yet but as the billboard photo and the adverts on the tube, show, it's getting there.
So how have we got to peak wastefulness? (unless you're returning to the discussion above, which turns 1 on-chain transaction into two in order to introduce lots of intermediary, but less secure, off-chain transactions of dubious utility). What mechanism will lead to the project moving into lower wastefulness? Just more efficient technology? You need 30% a month efficiency improvments just to stand still, that's way outside anything Moores law predicts.
predictions that it will use more energy than the sun in x years are dramatic.
of course. But I can write 30% increase per month until I'm blue in the face and not dent enthusiasm for the project.
It's not unlike the early days of Google when each search used the same amount of electricity as boiling a kettle.
It's hard to know how much of an urban myth that is. Google say
PUE = Power Usage Effectiveness
Google can achieve that because they're centralised and can set strategic direction. Nothing within the Bitcoin project can do so and anyway it's based on individual greed so pretty impervious to any external pressure.