Concern around the carbon footprint of Bitcoin is not holding back blockchain developers from leveraging the technology for action on climate change. Whilst blockchain is enabling individuals, companies and even cities to manage their carbon emissions, the social and environmental costs and benefits of doing so remain unclear. This July saw the release of the University of Cambridge's Bitcoin Electricity Consumption Index (CBECI), an online tool providing real-time conjectures around the electricity requirements of the Bitcoin network. The prestige afforded towards Cambridge is likely to propel the CBECI model ahead of the popular Digiconomist tool, which released its Bitcoin Energy Consumption Index in 2017. Despite the apparent advancement, the increasingly complex modelling of Bitcoin's energy requirements is yet to provide any further clarity. The CBECI analysis, for example, suggests that total power consumption, at the time of writing this, falls within a range of between 21 Twh and 146 Twh. To put that in perspective, those figures equate to somewhere between the energy consumption of Yorkshire and Poland 1. The network's energy requirements are as erratic as Bitcoin's price, depending as much on local weather events near remote Chinese hydroelectric plants, as the efficiency of energy-intensive servers that facilitate the Bitcoin blockchain 2. Bitcoin's computationally-demanding infrastructure enables digital payments to be validated via a decentralized, automated 'Proof of Work' (PoW) consensus protocol. For Bitcoin, the validation of transactions requires 'miners' using dedicated servers to solve hash puzzles in order to add valid entries to a shared database, and to secure new Bitcoins as a reward. The difficulty of these puzzles