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Could Bitcoin Emissions Push Global Warming Above 2 °C?

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matters arising
1Institute for Climate Protection, Energy and Mobility, Berlin, Germany. 2Institute for Future Energy Consumer Needs and Behavior,
RWTH Aachen University, Aachen, Germany. 3These authors contributed equally: Lars Dittmar, Aaron Praktiknjo. e-mail:;
In a recent commentary, Mora etal.1 hypothesize that cumulative
GHG emissions of Bitcoin alone could amount to ~231.4 GtC
within the next 16 yr (on the basis of their median scenario),
pushing global warming above 2 °C. To put these numbers in con-
text, the carbon budget of ~231.4 GtC is equivalent to ~63 yr of
emissions from global power generation at the rate observed in
2017 (that is, ~3.7 GtC)2. Bitcoin mining is undoubtedly electricity
intensive. However, the electricity demand scenarios calculated by
Mora etal. seem unlikely, as Bitcoin-related emissions would entail
a tripling of global electricity generation within the next five years
(see Supplement). We regard infrastructure bottlenecks and soar-
ing electricity prices as barriers to such growth levels. For example,
global electric power capacity increased by only ~ 17% over the past
five years.
The conclusions of Mora etal. on Bitcoin-related GHG emis-
sions are mainly based on estimated electricity consumption for
Bitcoin mining in 2017 and the extrapolation of this value to year
2100 at constant energy intensities and emission factors. To esti-
mate Bitcoin electricity consumption in 2017, Mora etal. assume
that each Bitcoin block was randomly mined on hardware included
in a self-compiled list of 62 devices. As this list contains many old
devices with high energy intensities, the resulting average hardware
energy intensity and electricity consumption of Bitcoin mining
are approximately ten times higher than other estimates (see the
Supplementary Information)3.
More importantly, we believe that the analysis of Mora etal. is
flawed because their methodology ignores fundamental constraints
imposed by the transaction-processing capacity of the Bitcoin net-
work. The diffusion scenarios presented by Mora etal. for Bitcoin
transactions eventually assume ~314.2 billion Bitcoin-related cash-
less transactions per year. The corresponding throughput of roughly
~10,000 transactions persecond would be at least two orders of
magnitude higher than Bitcoin’s current transaction limits. The
maximum transaction rate for Bitcoin is constrained by the effec-
tive block size and the block interval, both of which are defined
in the Bitcoin protocol4. While the effective block size defines the
maximum number of transactions per block, the block interval sets
the pace at which blocks are added to the blockchain. The current
block interval is set to 10 min, whereas effective block size rose from
1 MB to 4 MB megabyte in August 2017 as a result of the Segregated
Witness (SegWit) protocol upgrade. Before SegWit, the theoretical
maximum throughput had been estimated at 7 to 10 transactions
persecond, depending on the size of the transaction. After SegWit
implementation, the maximum was estimated to be 20 transactions
Mora etal. neither mention Bitcoins transaction limit nor outline
how it will be resolved to make their projection plausible. Instead,
the applied methodology circumvents the scalability problem by
implicitly reparameterizing the Bitcoin protocol to decrease the
block interval and increase the number of blocks until the result-
ing transactions match the number of projected transactions. As
the authors sample blocks from their base-year estimates, results
are equal to those obtained from scaling electricity consumption
in 2017 using projected transactions. Transaction growth is implic-
itly the sole driver for the electricity growth scenarios presented by
Mora etal. However, neither in a reparameterized Bitcoin protocol,
nor in the current protocol, is electricity consumption proportional
to the transaction rate. Instead, Bitcoins electricity consumption is
exclusively proportional to the hashrate, which is the computational
capacity of the Bitcoin network. Hashrate growth, in turn, is driven
by complex and mutually dependent relationships between mining
rewards, transaction fees, hardware energy efficiency, electricity
prices and the Bitcoin market price6. Increases in throughput capac-
ity, such as with SegWit, translate to a proportional decrease in elec-
tricity consumption per transaction, as the electricity consumption
of blocks does not scale with the transaction rate.
In conclusion, we consider the work of Mora etal. to be a timely
and interesting starting point for a discussion of the carbon emis-
sions attributable to Bitcoin. However, given the structural limita-
tions of the applied methodology, an enhanced scientific analysis is
required to determine Bitcoin-related emissions and their contribu-
tion to global warming.
Online content
Any methods, additional references, Nature Research reporting
summaries, source data, statements of code and data availability and
associated accession codes are available at
Data availability
The authors declare that all data supporting the findings of this
study are available in the article, the Supplementary Information
and in ref. 1.
Received: 21 November 2018; Accepted: 19 June 2019;
Published online: 28 August 2019
1. Mora, C. etal. Bitcoin emissions alone could push global warming above
2 °C. Nat. Clim. Change 8, 931–933 (2018).
Could Bitcoin emissions push global warming
above 2°C?
Lars Dittmar 1,3 and Aaron Praktiknjo 2,3
arising from Mora, C. etal. Nature Climate Change (2018)
Content courtesy of Springer Nature, terms of use apply. Rights reserved

Supplementary resources (3)

... The idea is simple: a higher number of transactions involving Bitcoin and Ether increases significantly the energy/electricity required to validate these transactions. Such perspective has been questioned by some technical works (Dittmar and Praktiknjo, 2019;Masanet et al., 2019;Schinckus et al., 2020Schinckus et al., , 2021 explaining that the number of transactions can actually be increased in a block computationally validated by the blockchain technology. These studies suggested (but did not provide empirical evidence) to study the electricity consumed by the blockchain technology in relation to the dynamics of its hashrate (i.e. the network's computational power) required to validate these transactions and not in relation to the trading volumethe novelty of this article is to provide an empirical analysis about the potential link between hashrate and energy consumption. ...
... validation of a block of transactions) are strongly related to the hashrate, as the higher hashrate, the higher computational power required for a new block to be mined\validated is. In other words, a higher hashrate implies a higher electricity consumption (Dittmar and Praktiknjo, 2019;Masanet et al., 2019) so that the baseline function can be summarized as follows: ...
... The existing literature acknowledges that an increasing number of transactions (trading volume) dealing with Bitcoin and Ether have an environmental impact through the high consumption of electricity required to validate these transactions. This perspective has been questioned by some technical works (Dittmar and Praktiknjo, 2019;Masanet et al., 2019;Schinckus, 2020 claiming that the validation (mining) is not operated on the transactions themselves but instead at the computational block level (each block compiling several transactions). Given the fact that the number of transactions can be increased in a block, a more sophisticated analysis is required. ...
Purpose Given the growing importance of cryptocurrencies and the technique called “SegWit” that allows to compile more transactions in a mined block, the electricity consumed per block might potentially decrease. The purpose of this study is to consider that the difficulty to mine a block might be a better indicator of the Bitcoin\Ether’s electricity consumption. Design/methodology/approach This study applies the vector error correction model to investigate data related to primary energy consumption and electricity production, supply and consumption for Bitcoin and Ether hashrates from 2016M1 to 2021M5. Findings The hashrate (difficulty of solving the cryptographic problem related to the validation of a transaction) is found to have a positive cointegration with energy and electricity consumption. Despite the launch of the Segregation Witness (SegWit) mechanism allowing blocks to handle a higher number of transactions per block, this Bitcoin and Ether growing need in electricity has significantly been increasing since October 2019. Originality/value The major contribution of this study is to investigate a more relevant indicator, namely, hashrate (computational difficulty to solve cryptographic enigma associated with cryptocurrencies-related transaction). The approach of this study can be justified by the fact that there exists a technical solution consisting in increasing the number of transactions per blocks so that less electricity might be required to validate a transaction.
... At the time of writing, the difficulty in the Bitcoin network requires a block hash with 76 leading zeros, yielding an expected number of hash operations of roughly 7.56 · 10 22 -requiring an aggregated network hash rate in the ballpark of Exa hashes per second. On the one hand, this massive amount of computational resources (and therefore energy) is considered a significant environmental problem [84,150] which has sparked research efforts into alternative consensus mechanisms [241], e.g., Proof-of-Stake (PoS) [26] or hybrid trust models such as Ripple [16,236] and Stellar [5,162]. However, these alternative approaches require more trust assumptions than PoW-based consensus [67,112], making it unlikely that Bitcoin will shift away from PoW. ...
... This statement can be further underlined by the popularity of existing stablecoins, as two of them are among the 30 largest cryptocurrencies by market capitalization: Tether [193] and Dai [185]. In that, stablecoins aim to fulfill two of the three commonly cited functions of money [276] 84 84 Medium of exchange, store of value and unit of account : (1) medium of exchange and (2) store of value, whereas normal cryptocurrencies are only able to fulfill (1). Stablecoins are therefore a fascinating topic of research, as their roots and applications lie in the technical realm of decentralized cryptocurrencies while their goal is inherently economic. ...
Die Erfindung von Bitcoin hat ein großes Interesse an dezentralen Systemen geweckt. Eine häufige Zuschreibung an dezentrale Systeme ist dabei, dass eine Dezentralisierung automatisch zu einer höheren Sicherheit und Widerstandsfähigkeit gegenüber Angriffen führt. Diese Dissertation widmet sich dieser Zuschreibung, indem untersucht wird, ob dezentralisierte Anwendungen tatsächlich so robust sind. Dafür werden exemplarisch drei Systeme untersucht, die häufig als Komponenten in komplexen Blockchain-Anwendungen benutzt werden: Ethereum als Infrastruktur, IPFS zur verteilten Datenspeicherung und schließlich "Stablecoins" als Tokens mit Wertstabilität. Die Sicherheit und Robustheit dieser einzelnen Komponenten bestimmt maßgeblich die Sicherheit des Gesamtsystems in dem sie verwendet werden; darüber hinaus erlaubt der Fokus auf Komponenten Schlussfolgerungen über individuelle Anwendungen hinaus. Für die entsprechende Analyse bedient sich diese Arbeit einer empirisch motivierten, meist Netzwerklayer-basierten Perspektive -- angereichert mit einer ökonomischen im Kontext von Wertstabilen Tokens. Dieses empirische Verständnis ermöglicht es Aussagen über die inhärenten Eigenschaften der studierten Systeme zu treffen. Ein zentrales Ergebnis dieser Arbeit ist die Entdeckung und Demonstration einer "Eclipse-Attack" auf das Ethereum Overlay. Mittels eines solchen Angriffs kann ein Angreifer die Verbreitung von Transaktionen und Blöcken behindern und Netzwerkteilnehmer aus dem Overlay ausschließen. Des weiteren wird das IPFS-Netzwerk umfassend analysiert und kartografiert mithilfe (1) systematischer Crawls der DHT sowie (2) des Mitschneidens von Anfragenachrichten für Daten. Erkenntlich wird hierbei, dass die hybride Overlay-Struktur von IPFS Segen und Fluch zugleich ist, da das Gesamtsystem zwar robust gegen Angriffe ist, gleichzeitig aber eine umfassende Überwachung der Netzwerkteilnehmer ermöglicht wird. Im Rahmen der wertstabilen Kryptowährungen wird ein Klassifikations-Framework vorgestellt und auf aktuelle Entwicklungen im Gebiet der "Stablecoins" angewandt. Mit diesem Framework wird somit (1) der aktuelle Zustand der Stablecoin-Landschaft sortiert und (2) ein Mittel zur Verfügung gestellt, um auch zukünftige Designs einzuordnen und zu verstehen.
... Nonetheless, it is important to note that, since transaction fees currently play only a marginal role in the remuneration of miners, increasing the limit of transactions in the Bitcoin protocol would not increase total energy consumption considerably. Because of this particularity, the 'energy per transaction' metric frequently causes misunderstandings (Dittmar and Praktiknjo, 2019;Sedlmeir et al., 2020;Lei et al., 2021). We will, therefore, consider annual electricity consumption exclusively in this survey. ...
Some of the most popular decentralised cryptocurrency networks have drawn widespread criticism for consuming vast amounts of electricity and have thus become targets of regulatory interest. Attempts to influence cryptocurrency network operations via policy in the pursuit of sustainability in the past, however, have been widely unsuccessful. Some were abandoned out of fear of jeopardising innovation while others failed due to the highly globalised nature of decentralised systems. Considering Bitcoin as an archetype for cryptocurrencies with high energy demand, this study takes a bottom-up approach by analysing statements made by Nigerian cryptocurrency users ($N = 158$) concerning their perception of sustainability issues. Three main findings emerged: 1) Despite self-reporting as highly knowledgeable, most participants significantly underestimate the energy demand of Bitcoin. 2) Those who accurately assess the energy demand of Bitcoin are more likely to support measures targeting its energy demand than those who misestimate it. 3) Those who support measures predominantly hold private actors responsible. In light of these findings, it is concluded that the primary task of policy makers in the context of cryptocurrency sustainability is to enforce consumer education.
... In 2018, Mora et al. [24] claimed that bitcoin emissions could push global warming above two centigrades. The analysis and results of the paper by Mora et al. have been debunked at least by Houy [25], Masanet et al. [26], and Dittmar et al. [27]. According to Houy, rational mining limits Bitcoin emissions, and the average of a list of 62 ASIC miners used by Mora De Vries [28] estimated in 2018 that the Bitmain company, with a claimed market share of 70%, could produce up to 6.5 million bitcoin mining machines (Antminer S9) in 2018. ...
According to recent estimates, one bitcoin transaction consumes as much energy as 1.5 million Visa transactions. Why is bitcoin using so much energy? Most of the energy is used during the bitcoin mining process, which serves at least two significant purposes: a) distributing new cryptocurrency coins to the cryptoeconomy and b) securing the Bitcoin blockchain ledger. In reality, the comparison of bitcoin transactions to Visa transactions is not that simple. The amount of transactions in the Bitcoin network is not directly connected to the amount of bitcoin mining power nor the energy consumption of those mining devices; for example, it is possible to multiply the number of bitcoin transactions per second without increasing the mining power and the energy consumption. Bitcoin is not only “digital money for hackers”. It has very promising future potential as a global reserve currency and a method to make the World Wide Web (WWW) immune to cyberattacks such as the Distributed Denial-of-Service attacks. This survey approached cryptocurrencies’ various technological and environmental issues from many different perspectives. To make various cryptocurrencies, including bitcoin (BTC) and ether (ETH), greener and more justified, what technological solutions do we have? We found that cryptocurrency mining might be cleaner than is generally expected. There is also a plan to make a vast renewable energy source available by combining Ocean Thermal Energy Conversion and Bitcoin mining. There are plans to use unconventional computing methods (quantum computing, reversible computing, ternary computing, optical computing, analog computing) to solve some of the issues regarding the vast energy consumption of conventional computing (including cryptocurrency mining). We think using spare computing cycles for grid computing efforts is justified. For example, there are billions of smartphones in the world. Many smartphones are being recharged every day. If this daily recharging period of twenty to sixty minutes would be used for grid computing, for example, finding new cures to cancer, it would probably be a significant breakthrough for medical research simulations. We call cryptocurrency communities to research and develop grid computing and unconventional computing methods for the most significant cryptocurrencies: bitcoin (BTC) and ether (ETH).
... They consume a large amount of computing power and waste energy, as additional electricity is used for computers to perform extra computational work. This can add up to an extremely large amount of excess electricity consumption and environmental detriment [3][4][5]. ...
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... 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). ...
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Building on an economic model of rational Bitcoin mining, we measured the carbon footprint of Bitcoin mining power consumption using feed-forward neural networks. We found associated carbon footprints of 2.77, 16.08 and 14.99 MtCO2e for 2017, 2018 and 2019 based on a novel bottom-up approach, which (i) conform with recent estimates, (ii) lie within the economic model bounds while (iii) delivering much narrower prediction intervals and yet (iv) raise alarming concerns, given recent evidence (e.g., from climate–weather integrated models). We demonstrate how machine learning methods can contribute to not-for-profit pressing societal issues, such as global warming, where data complexity and availability can be overcome.
... The preservation of data integrity via a blockchain-based solution using so-called Proofof-Work (PoW) consensus was examined in [30] and [27], each assuming the robots enjoyed continuous connectivity (CC). PoW consensus is a popular and effective choice in the cryptocurrency industry [23], but it is known to be resource intensive [6], [7] and, in turn, raises new challenges for resource-limited multi-robot information collection. ...
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With 100% segwit transactions, what would be the max number of transaction confirmation possible on a block?
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