Purpose This paper aims to quantify the (syndicated) loan exposure to elevated environmental risk sectors of the banking system in the USA, EU, China, Japan and Switzerland at US$1.6tn and to highlight its importance, which ranges from 3.8 (USA) to 0.5 per cent (China) in terms of total national banking assets. The paper highlights the relevance of exploring prudential policy responses, including a harmonized taxonomy, statistical and reporting framework that could contribute to internalizing the negative externalities associated with climate risks by both banks and their supervisors. Among the prudential supervisory tools, credit registers facilitate the assessment of environmental risk drivers in carbon stress tests. This paper also presents a framework of analysis for the regulatory treatment of climate-related risks. Design/methodology/approach Similarly to Weyzig et al. (2014), this paper uses financial databases on the banks' role as book runners for syndicated loans; that is, as the lead arrangers who also provide a large share of the actual lending. Loans are outstanding on December 31, 2014, and the paper assumes linear amortization of loans issued before that date and with maturity after that date. This study includes the largest banks from the above-mentioned countries with financial information available in SNL Financial and EU banks with financial information available in the ECB database on December 31, 2014. By assessing the relative share of the ten largest (or total reporting if less) banks' exposure to each high environmental risk sector in relation to their total assets, these findings can be extrapolated across sectors in the respective country. Findings This paper quantifies the loan exposure to elevated environmental risk sectors of the banking system in the USA, EU, China, Japan and Switzerland in US$1.6tn, broadly in line with the findings of Battiston et al. (2017) and Weyzig et al. (2014). This paper also explores prudential policy approaches and tools. In addition to the lack of taxonomy of brown vs green, the paper identifies the limitations to assess the risks involved in the transition to a low-carbon economy: supervisory reports that do not make full use of the existing international statistical framework (e.g. EU COREP and FINREP); lack of harmonized reporting requirements of environmental risks; lack of credit registers as tools to perform carbon stress-testing; and supervisors' governance framework that do not internalize environmental risks (e.g. proposed revision of the Basel Core Principles of Banking Supervision). As per the stress-testing, the paper presents two examples. The paper presents a framework of analysis for the regulatory treatment of climate-related risks. The author identifies two critical elements of such framework if prudential regulation of environmental risks is to be considered: the consideration or not of climate risk as credit risk and the impact of environmental risks over probabilities of default over the entire business cycle. Research limitations/implications No internationally accepted official taxonomy of high environmental risk sectors exists. This paper uses Moody's (2015a) classification of sectors according to their environmental risk exposure. This paper's exposures do not reflect the real risk exposure of these institutions and the banking industry as a whole because, as explained in Page 6, these values are without regard to bilateral loans and guarantees and securitizations of loans; in the case of loans to power generation companies, renewable sources are not excluding and, similarly, for the production of electric vehicles, loans are not excluded. Furthermore, this paper does not assess banks' exposures to sovereigns subject to high environmental risks and bonds and equity issued by corporations operating in high environmental risk sectors. Practical implications Contribution to the present policy debate on how to regulate banks' exposure to high environmental risk and how to manage the transition to a low-carbon economy. Social implications This paper can increase awareness of the banking sector transition risks to a low-carbon economy. Originality/value This paper quantifies banks direct exposures to high environmental risk sectors using an ample definition of sectors exposed to environmental risk. The author suggests policy actions to assess the environmental risks. The author defines a regulatory framework for banks to internalize the negative externalities of environmental risks.
