As for '4', you have an implicit assumption that I see a lot on HN. No, BTC doesn't have a massive environmental cost. Please re-examine that premise.
Said in a different way to do all financial transactions on the blockchain would use a lot more energy then it currently does.
140TWh out of 170000TWh is about 0.8%. relative impact is bigger than 0.08%. Coal is 36% of the power mix. Under the assumption that most bitcoin mining happens connected to the grid (seems reasonable) and that these grids contain coal powerplants (also reasonable with the exception of Iceland), that 0.08% translates to 0.22% of global coal based emissions. On a global scale, being responsible for 1/500th is a lot (for me at least)
the numbers are more relatable when looking at absolute impact. Assuming a average coal power plant of 600MW (you can find bigger, but this is a representative plant near me[1]). That’s 5TWh/yr per plant. Bitcoin then represents 28 of such coal powerplants running at 100% capacity 24/7. That - to me - seems like a massive amount of CO2 for a niche application.
And if I read your source correctly, that’s just bitcoin
1: https://en.wikipedia.org/wiki/Amercentrale
Coal is about 36%