>At current levels, bitcoin uses very roughly 0.1% of global electricity but electricity only represents 25% of fossil fuels emissions so current PoW contribution to global emissions = 0.025%, ie a rounding error.

How does this argument make sense? Let's split up the world's energy consumption into 0.025% emission sized chunks in some arbitrary way we choose. Does nothing then make any difference, since everything is just a rounding error? The question is, does bitcoin provide value for the emissions it generates? For what it's worth, estimates seem to put the current usage at around 0.6% of total worldwide energy consumption.