Implausible projections overestimate near-term Bitcoin CO2 emissions

Abstract

Bitcoin mining is becoming an increasingly energy-intensive process 1,2,3 whose future implications for energy use and CO2 emissions remain poorly understood. This is in part because-like many IT systems-its computational efficiencies and service demands have been evolving rapidly. Therefore, scenario analyses that explore these implications can fill pressing knowledge gaps, but they must be approached with care. History has shown that poorly constructed scenarios of future IT energy useoften due to overly-simplistic extrapolations of early rapid growth trends-can do more harm than good by spreading misinformation and driving ill-informed decisions. 4,5,6 Indeed, the utility of an energy demand scenario is directly proportional to its credibility, which is typically demonstrated through careful attention to technology characteristics and evolution, analytical rigor and transparency, and designing scenarios that align with plausible future outcomes. Regrettably, the Bitcoin CO2 emissions scenarios presented in the recent Mora et al. article 7 lack such credibility and should not be taken seriously by the research and policy communities. We arrived at this conclusion by replicating in detail Mora et al.'s methods, which revealed numerous flaws in the design and execution of their analysis as documented in the Supplementary Information. We describe the five most significant issues below.

Machine Learning the Carbon Footprint of Bitcoin Mining

“…5 Relative to the aforementioned literature, the reported point estimates (and PIs) also represent a downward revision of the results reported by Mora et al (2018) and are broadly in line with figures from Foteinis (2018), reporting global emissions for Bitcoin and Ethereum for 2017 of 43.9 MtCO 2 , or from Stoll et al (2019), reporting annual carbon emissions for Bitcoin mining in 2018 in the range from 22.0 to 22.9 MtCO 2 . Our estimates further revise downward the 2017 estimates provided by Houy (2019) or Dittmar and Praktiknjo (2019), reporting 15.5 MtCO 2 e for 2017, or those from Masanet et al (2019), who reported, for 2017, an estimate of 15.7 MtCO 2 e. What makes them nevertheless worrying is recent evidence, e.g., from integrated weather-climate models (CMIP6), feeding into the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) 2021 reported in Williams et al (2020). According to them, global temperatures may rise as much as 5 • C, prompting the recent global call to urgent policy measures by IMF's Chief Economist Gita Gopinath in Davos (Switzerland, 2020).…”

“…Mora et al (2018) estimated that the 2017 carbon footprint of Bitcoin reached 69 million metric tons of CO 2 equivalent (MtCO 2 e), forecasting a violation of the Paris COP21 UNFCCC Agreement 2 by 2040 due to Bitcoin's cumulative emissions alone. At the heart of the controversy sparked, with various contributions revising downward the projections obtained by Mora et al (2018) (e.g., Houy 2019Masanet et al 2019;Stoll et al 2019), lies the difficulty in measuring the power consumption of the Bitcoin mining network and the associated carbon emissions (De Vries 2018. Bitcoin miners are globally geo-located, facing very different energy costs, and employ hardware with unknown energy intensities.…”

Crypto-Currencies Trading and Energy Consumption

“…In this research, we did not distinguish the proof-of-work based crypto-currencies from the other algorithms based ones -this could be a limitation of our study -but still acceptable since the vast majority of the crypto-currencies are now traded through the energy consuming Proof-of-Work consensus (Goodkind et al 2020), we simply use the data related to the trading of all crypto-currencies in our analysis. Another methodological aspect can be mentioned here: in line with the existing literature, we associated here the electricity consumption with the trading volume of cryptocurrencies -it is worth mentioning that some studies (Dittmar and Praktiknjo 2019;Masanet et al, 2019) claim that the Bitcoin's electricity consumption should be analyzed in relation with the hashrate (i.e. the network computational power).…”

Small NGOs and Agenda-Setting in Global Conservation Governance: The Case of Pangolin Conservation

“…Others noted that TNC failed to criticize oil industries when a massive amount of oil spilled in the Gulf of Mexico (Hari 2010). More recently, researchers warn that cryptocurrency mining is environmentally harmful because of the large amount of electricity required for mining computation (Masanet et al 2019;Mora et al 2018). 16 Leading environmental NGOs have been quiet on this issue so far; Greenpeace even accepts donations via bitcoin until May 2021.…”