is sizable relative to other central banks ( the bank of england ’ s cbps portfolio currently totals approximately gbp 20 billion whereas the size of the ecb ’ s cspp portfolio amounts to eur 278 billion at amortised cost as at 4 june 2021 ), the ecb ’ s cspp portfolio is far smaller than the pspp portfolio, which stands at eur 2. 4 trillion at amortised cost as at 4 june 2021. 41. evidence regarding the capacity of the market to correctly price green bonds is currently still mixed. some papers point to the existence of a positive carbon premium whereby investors demand a compensation for holding securities issued by carbon - intensive companies. see, for example, alessi, l., ossola, e. and panzica, r. ( 2019 ), “ the greenium matters : greenhouse gas emissions, environmental disclosures, and stock prices, ” working papers in economics and finance, no 2019 - 12, joint research centre, european commission. however, when a premium exists, it seems to only reflect the transition policy risk. see van der ploeg, f. ( 2020 ). “ macro - financial implications of climate change and the carbon transition ”. ecb. in addition, some other papers find either a negative premium or no or little premium. see, for example, tang, d. y. and zhang, y. ( 2020 ), “ do shareholders benefit from green bonds? ” journal of corporate finance, vol. 61 ; zaghini, a. ( 2020 ), “ the covid pandemic in the market : infected, immune and cured bonds ” ( 2020 ), covid economics, vetted and real - time papers, issue 50, cepr press. 42. at present, seven countries in the euro area issue green government bonds. in total, green debt ( also including green bonds issued by suprananational institutions, regional bonds and agencies ) currently only represents 1. 4 % of the ecb ’ s pspp portfolio. this share is in line with its market capitalisation. 43. forward - looking metrics, including measures of sovereign issuers ’ alignment with the paris agreement, are still being developed for commercially available sustainability data. furthermore, the methodology for analysing and reporting the carbon impact of sovereign bonds is comparatively less advanced than for other types of fixed income instruments ( including corporate bonds ). currently, data providers mostly follow a production - based approach. under

( 2021 ), “ the conference messages in light of the g20 presidency programme ”, 4 june. 9. ecb and esrb ( 2020 ), “ positively green : measuring climate change risks to financial stability ”, june. 10. see de guindos, l. ( 2021 ), “ shining a light on climate risks : the ecb ’ s economy - wide climate stress test ”, the ecb blog, 18 march. 11. see allen, t., et al. ( 2020 ), “ climate - related scenarios for financial stability assessment : an application to france ”, working paper series, no 774, banque de france. 12. see lagarde, c. ( 2020 ), “ climate change and the financial sector ”, 27 february. 13. while there is widespread consensus about central banks ’ potential role in mitigating the consequences of climate risks, a number of concerns have also been raised. some refer to the possible interference with the primary mandate, others to the politicisation of monetary policy and the danger of mission creep, with potential negative ramifications for central bank independence and monetary policy effectiveness. see, for example, cochrane, j. ( 2020 ), “ challenges for central banks ”, october. 14. this includes various members of the ecb ’ s governing council. see, for example, knot, k. ( 2021 ), “ getting the green deal done : how to mobilize sustainable finance ”, 11 february ; villeroy de galhau, f. ( 2021 ), “ the role of central banks in greening the economy ”, 11 february ; de cos, p. h. ( 2021 ), “ economic and financial policy geared to climate goals ”, 25 february ; weidmann, j. ( 2021 ), “ climate risks, financial markets and central banks ’ risk management ”, 2 june. 15. see ngfs ( 2021 ), “ adapting central bank operations to a hotter world : reviewing some options ”, march ; villeroy de galhau, f. ( 2021 ), ibid. 16. see hauser, a. ( 2021 ), “ it ’ s not easy being green – but that shouldn ’ t stop us : how central banks can use their monetary policy portfolios to support orderly transition to net zero ”, 21 may ; bank of england ( 2021 ), “ options for greening the bank of england ’ s corporate bond purchase scheme ”