This is a totally fair point. The price of carbon emissions should reflect their true cost.
> PoW does not pollute nor emit greenhouse gases.
I'm not sure whether you're saying PoW doesn't directly emit greenhouse gases, or that the carbon footprint of PoW mining is zero.
So you are okay with someone mining bitcoins if they do so using Solar energy?
Well there are two separate issues.
The first is that the price of hydrocarbons doesn't include the externalised cost of CO2 emissions, leading to market distortion. In a perfect world we would fix that, and see what shakes out.
If the combined effect of carbon taxes and high energy demand makes energy so expensive that people cannot afford the basics, then the next step is effectively one of rationing. If proof-of-waste miners are outbidding poorer people for energy they need to heat their homes (or the equipment to generate it), it might be necessary to ringfence energy production for providing a reasonable standard of living. If there is any excess then the miners and other discretionary users can compete to buy it.
All that is my understanding of how to employ market forces to most efficiently allocate energy resources to people that need it, whilst protecting the climate. But I don't know if we can get all that agreed in time, and I'll support anything that reduces unnecessary CO2 emissions quickly.
Why? How about we regulate things that pollute instead, like burning coal. PoW does not pollute nor emit greenhouse gases.