Note that three articles were published in response to this one (linked as 'Matters Arising' in the top part of the article), and they all appear to criticize the methodology that was used here.
The key objections from the first such article [1] are as follows (quoted verbatim, though the article itself obviously contains more details):
> First, the use of transactions as the driver of future Bitcoin emissions is questionable, given the tenuous correlation between transactions and mining energy use...
> Second, all three Bitcoin adoption scenarios designed by Mora et al. represent sudden and improbable departures from historical trends in Bitcoin transactions...
> Third, Mora et al. applied outdated values for mining rig efficiencies and electric power CO2 intensities, which inflated their estimated 2017 Bitcoin energy use and CO2 emissions values considerably.
> Fourth, by analytical design, Mora et al. applied 2017 per-transaction energy use and CO2 emissions values in all future years, multiplied by annual transactions... This decision effectively held both mining rig efficiency and grid CO2 intensities constant for the next 100 yr... This unprecedented choice ignores the dynamic nature of mining rig and power grid technologies and violates the widely followed practice of accounting for technological change in forward-looking energy technology scenarios...
> Fifth, in constructing their scenarios, Mora et al. committed key errors when analysing adoption rates within their 40-technology comparison pool...
One thing that is interesting though is that it seems like BTC mining would increase with the price of BTC. If each BTC is more valuable, it becomes more feasible to use more energy on mining rigs. Am I wrong?
The key objections from the first such article [1] are as follows (quoted verbatim, though the article itself obviously contains more details):
> First, the use of transactions as the driver of future Bitcoin emissions is questionable, given the tenuous correlation between transactions and mining energy use...
> Second, all three Bitcoin adoption scenarios designed by Mora et al. represent sudden and improbable departures from historical trends in Bitcoin transactions...
> Third, Mora et al. applied outdated values for mining rig efficiencies and electric power CO2 intensities, which inflated their estimated 2017 Bitcoin energy use and CO2 emissions values considerably.
> Fourth, by analytical design, Mora et al. applied 2017 per-transaction energy use and CO2 emissions values in all future years, multiplied by annual transactions... This decision effectively held both mining rig efficiency and grid CO2 intensities constant for the next 100 yr... This unprecedented choice ignores the dynamic nature of mining rig and power grid technologies and violates the widely followed practice of accounting for technological change in forward-looking energy technology scenarios...
> Fifth, in constructing their scenarios, Mora et al. committed key errors when analysing adoption rates within their 40-technology comparison pool...
[1] 'Implausible projections overestimate near-term Bitcoin CO2 emissions', available at https://www.nature.com/articles/s41558-019-0535-4