rewards of new units of currency, will decline given the total supply of bitcoin cannot exceed 21 million. furthermore, the costs of bitcoin mining are enormous. its current annual electricity consumption is estimated by some to be up to 52 terawatt hours, double the electricity consumption of scotland. in comparison, the global visa credit card network ’ s energy use is less than ½ of 1 % of that of bitcoin, despite processing 9000 times more transactions. carstens, a., ( 2018 ), “ money in the digital age : what role central banks? ” see https : / / www. bis. org / speeches / sp180206. htm based on the british retail consortium ’ s payment survey 2016, which surveys the costs that retailers incur for accepting payments, including bank charges, handling charges, infrastructure costs and write - offs ( losses ). link to survey : https : / / brc. org. uk / media / 179489 / payment - survey - 2016 _ final. pdf the reward for each new block halves every 210, 000 blocks ( approximately every 4 years ) and currently stands at 12. 5 bitcoin per block. this regular halving of the block reward results in an exponential slow - down in the growth rate of bitcoin supply. it is estimated that by 2040 99. 8 % of total maximum bitcoin supply will have been generated. for bitcoin energy usage, see : https : / / digiconomist. net / bitcoin - energy - consumption. for scottish energy usage, see http : / / www. gov. scot / topics / statistics / browse / business / energy / eis2018 for visa ’ s energy usage, see their corporate social responsibility report ( 2016 ). all speeches are available online at www. bankofengland. co. uk / speeches virtually non - existent units of account given that they are poor stores of value and inefficient and unreliable media of exchange, it is not surprising that there is little evidence of cryptocurrencies being used as units of account. retailers that quote in bitcoin usually update at very high frequency so as to maintain stable prices in traditional currencies such as us dollars or sterling. the bank is not aware of any business that accepts bitcoins in payments that also maintains its accounts in bitcoin. the policy response even though their prospects of replacing fiat money

climate - and weather - related events that damage property and disrupt trade. transition risks result from the adjustment towards a lower - carbon economy. changes in policies, technologies and physical risks will prompt a reassessment of the value of a large range of assets as costs and opportunities become apparent. the longer meaningful adjustment is delayed, the more transition risks will rise. climate risks also have a number of distinctive elements, which, in combination, require a strategic approach. these include their : breadth, as climate risks affect multiple lines of business, sectors and geographies ; magnitude, as the full impacts of climate risks are large, potentially non - linear and irreversible ; foreseeable nature ; for example the oil and gas industry group convened by the world business council on sustainable development and the institute of international finance for banks. the other channel concerns liability risks. these stem from parties who have suffered loss from the effects of climate change seeking compensation from those they hold responsible. such claims could arise well into the future, as the science and evidence of climate change hardens, though some are already taking action against companies on the grounds of failure to disclose the risks posed to their business models by climate change. all speeches are available online at www. bankofengland. co. uk / publications / pages / speeches / default. aspx dependency on short - term actions given that the size of future impacts will, at least in part, be determined by the actions taken today ; and uncertain time horizon which may stretch beyond traditional business planning cycles. the nature of these risks means that the biggest challenge in climate risk management is in assessing the resilience of firms ’ strategies to transition risks. part of the genius of the private sector - led tcfd is its recognition that disclosure needs to go beyond the static to the strategic. markets need information to assess which companies can seize the opportunities in a low carbon economy and which are strategically resilient to the physical and transition risks associated with climate change. the bank of england has also become increasingly active in such assessments, consistent with our financial stability and prudential mandates. as the supervisor of the world ’ s fourth largest insurance industry, we know that general insurers and reinsurers are on the front line of managing the physical risks from climate change. insurers have responded by developing their modelling and forecasting capabilities, improving exposure management, and adapting coverage and pricing. 8 in the process, insurers have learned that yesterday ’