Climate change – a central banking perspective

A BIS paper titled “Green Swan 2 – Climate change and Covid-19: reflections on efficiency versus resilience” initially caught my attention because of the reference to the tension between efficiency versus resilience. This tension is, for me at least, one of the issues that has tended to be ignored in the pursuit of growth and optimised solutions. The papers mainly deal with the challenges that climate change creates for central banks but I think there are also some insights to be drawn on what it means for bank capital management.

A core argument in the paper is that challenges like climate change and pandemics ….

“… require us to rethink the trade-offs between efficiency and resilience of our socio-economic systems … one way to address this issue is to think about buffers or some necessary degree of redundancy for absorbing such large shocks. Countries build FX reserves, banks maintain capital buffers as required by regulators, and so on. Perhaps similar “buffers” could be used in other areas of our societies. For example, could it be time to reassess our production systems, which are meant to be lean and less costly for maximum efficiency?”

The paper draws on a (much longer and more technical) BIS research paper titled “The green swan: Central banking and financial stability in the age of climate change”. Both papers contain the usual caveat that the views expressed do not necessarily reflect those of their respective institutions. With that warning noted, this post draws on both papers to make some observations about what the papers say, and what this means for bank capital management.

There is a lot of content in the combined papers but the points that resonated the most with me were

1. Climate change shares some of the features of a Black Swan event but is better thought of a distinct type of risk which the authors label a “Green Swan”.
2. Green swan problems are created in part by choices we have made regarding the value of efficiency over resilience – part of the solution lies in rethinking these choices but this will not be easy.
3. Climate change is a “collective action” problem which cannot be addressed by individual actors (including banks) operating independently – market based solutions like a carbon price may also be insufficient to bring about a solution that does not involve an unacceptable level of financial disruption.
4. Scenario analysis (including stress testing) appears to be one of the better tools for dealing with climate change and similar types of risk – but it needs to be used differently (by both the supervised and the supervisors) from the way it is applied to conventional risks.

I am not an expert on climate change modelling, but Chapter 3 of the second paper also has what looks to be a useful overview of the models used to analyse climate change and how the outputs of these models are used to generate economic impacts.

Black, white and green swans

Climate change clearly operates in the domain of radical uncertainty. As such it shares some common elements with “black swan” events; in particular the fact that conventional risk models and analysis are not well suited to measuring and managing the potential adverse impacts. It is equally important however to understand the ways in which climate change differs from a classic black swan event. There is a longer list but the ones that I found most relevant were:

1. Predictability – Black Swans are, by definition, not predictable whereas the potential for adverse Climate Change outcomes is well understood even if not universally accepted. The point is that understanding the potential for adverse impact means we have a choice about what to do about it.
2. Impact – Black Swan events can have substantial impacts but the system can recover (e.g. the GFC has left a lasting impact but economic activity did recover once the losses were absorbed). The impacts of climate change, in contrast, may be irreversible and have the potential to result in people dying in large numbers.

Given the conceptual differences, the authors classify Climate Change as a distinct form which they label a “Green Swan”. To the best of my knowledge, this may be the first time the term has been used in this way. That said, the general point they are making seems to be quite similar to what other authors have labelled as “Grey Rhinos” or “Black Elephants” (the latter an obvious allusion to the “elephant in the room”, a large risk that is visible to everyone but no one wants to address).

A typology of swans

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Categorising climate risk

The papers distinguish two main channels through which climate change can affect financial stability – physical risks and transition risks.

Physical risks are defined as

… “those risks that arise from the interaction of climate-related hazards […] with the vulnerability of exposure to human and natural systems” (Batten et al (2016)). They represent the economic costs and financial losses due to increasing frequency and severity of climate-related weather events (eg storms, floods or heat waves) and the effects of long-term changes in climate patterns (eg ocean acidification, rising sea levels or changes in precipitation). The losses incurred by firms across different financial portfolios (eg loans, equities, bonds) can make them more fragile.

Transition risks are defined as those

“… associated with the uncertain financial impacts that could result from a rapid low-carbon transition, including policy changes, reputational impacts, technological breakthroughs or limitations, and shifts in market preferences and social norms.

A rapid and ambitious transition to lower emissions, for example, would obviously be desirable from the perspective of addressing climate change but might also mean that a large fraction of proven reserves of fossil fuel cannot be extracted, becoming “stranded assets”. The write down of the value of these assets may have potentially systemic consequences for the financial system. This transition might occur in response to policy changes or by virtue of some technological breakthrough (e.g. problem of generating cheap energy by nuclear fusion is solved).

Efficiency versus resilience

I started this post with a quote from the first (shorter) paper regarding the way in which the Covid 19 had drawn attention to the extent to which the pursuit of efficiency had made our economies more fragile. The paper explores the ways in which the COVID 19 pandemic exhibits many of the same features that we see in the climate change problem and how the global response to the COVID 19 pandemic might offer some insights into how we should respond to climate change.

The paper is a useful reminder of the nature of the problem but I am less confident that it offers a solution that will work without some form of regulation or public sector investment in the desired level of redundancy. The paper cites bank capital buffers introduced post GFC as an example of what to do but this was a regulated outcome that would most likely not be acceptable for non-financial companies in countries that remain committed to free market ideology.

The Economist published an article on this question that offered numerous examples of similar problems that illustrate the propensity of “humanity, at least as represented by the world’s governments … to ignore them until forced to react” .

Thomas Friedman’s article (“How we broke the world”) is also worth reading on this question …

If recent weeks have shown us anything, it’s that the world is not just flat. It’s fragile.

And we’re the ones who made it that way with our own hands. Just look around. Over the past 20 years, we’ve been steadily removing man-made and natural buffers, redundancies, regulations and norms that provide resilience and protection when big systems — be they ecological, geopolitical or financial — get stressed. We’ve been recklessly removing these buffers out of an obsession with short-term efficiency and growth, or without thinking at all.

The New York Times, 30 May 2020

Managing collective action problems

The second paper, in particular, argues that it is important to improve our understanding of the costs of climate change and to ensure that these costs are incorporated into the prices that drive the resources we allocate to dealing with the challenge (e.g. via a carbon price or tax). However one of its key conclusions is that relying on markets to solve the problem is unlikely to be sufficient even with the help of some form of carbon price that reflects a more complete account of the costs of our current carbon based economy.

In short, the development and improvement of forward-looking risk assessment and climate- related regulation will be essential, but they will not suffice to preserve financial stability in the age of climate change: the deep uncertainty involved and the need for structural transformation of the global socioeconomic system mean that no single model or scenario can provide sufficient information to private and public decision-makers. A corollary is that the integration of climate-related risks into prudential regulation and (to the extent possible) into monetary policy would not suffice to trigger a shift capable of hedging the whole system again against green swan events.

The green swan: Central banking and financial stability in the age of climate change; Chapter 5 (page 66)

Using scenario based methodologies to assess climate related risks

Both papers highlight the limitations of trying to measure and understand climate change using conventional probability based risk management tools. The one area they do see as worth pursuing is using scenario based approaches. This makes sense to me but it is also important to distinguish this kind of analysis from the standard stress testing used to help calibrate capital buffers.

The standard application of stress testing takes a severe but plausible macro economic scenario such as a severe recession and determines what are the likely impacts on capital adequacy ratios. This offers a disciplined way of deciding how much capital surplus is required to support the risk appetite choices a bank has made in pursuit of its business objectives.

A simplistic application of climate based stress testing scenarios might take the same approach; i.e. work out how much the scenario impacts the capital and ensure that the buffer is sufficient to absorb the impact. That I think is not the right conclusion and my read of the BIS papers is that they are not advocating that either. The value of the scenario based modelling is to first get a handle on the size of the problem and how exposed the bank is to it. A capital response may be required but the answer may also be to change the nature of your exposure to the risk. That may involve reduced risk limits but it may also involve active participation in collective action to address the underlying problem. A capital management response may be part of the solution but it is far from the first step.

Conclusion

I have only scratched the surface of this topic in this post but the two papers it references are worth reading if you are interested in the question of what climate change, and related Green Swan or Black Elephant problems, mean for the banking system and for central banking. There is a bit more technical detail in the appendix below but it is likely only of interest for people working at the sharp end of trying to measure and manage the problem.

I want to dig deeper into the question of how you use stress testing to assess climate change and related types of risk but that is a topic best left for another post.

Tony – From the outside

Appendix – Modelling the impacts of climate change

Section 3 of the longer paper (“Measuring climate-related risks with scenario-based approaches”) discusses the limitations of the models that are typically used to generate estimates of the ecological and financial impacts of climate change scenarios. There is plenty of material there for climate sceptics but it also assists true believers to understand the limits of what they can actually know and how coming to terms with the radical uncertainty of how climate change plays out shapes the nature of our response.

I have copied some extracts from the chapter below that will give you a flavour of what it has to say. It is pretty technical so be warned …

“… the standard approach to modelling financial risk consisting in extrapolating historical values (eg PD, market prices) is no longer valid in a world that is fundamentally reshaped by climate change (Weitzman (2011), Kunreuther et al (2013)). In other words, green swan events cannot be captured by traditional risk management.

The current situation can be characterised as an “epistemological obstacle” (Bachelard (1938)). The latter refers to how scientific methods and “intellectual habits that were useful and healthy” under certain circumstances, can progressively become problematic and hamper scientific research. Epistemological obstacles do not refer to the difficulty or complexity inherent to the object studied (eg measuring climate-related risks) but to the difficulty related to the need of redefining the problem”

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nothing less than an epistemological break (Bachelard, 1938) or a “paradigm shift” (Kuhn (1962)) is needed today to overcome this obstacle and more adequately approach climate-relate risks (Pereira da Silva (2019a)).

In fact, precisely an epistemological break may be taking place in the financial sector: recently emerged methodologies aim to assess climate-related risks while relying on the fundamental hypothesis that, given the lack of historical financial data related to climate change and the deep uncertainty involved, new approaches based on the analysis of prospective scenarios are needed. Unlike probabilistic approaches to financial risk management, they seek to set up plausible hypotheses for the future. This can help financial institutions integrate climate-related risks into their strategic and operational procedures (eg for the purpose of asset allocation, credit rating or insurance underwriting) and financial supervisors assess the vulnerability of specific institutions or the financial system as a whole

Climate-economic models and forward-looking risk analysis are important and can still be improved, but they will not suffice to provide all the information required to hedge against “green swan” events.

As a result of these limitations, two main avenues of action have been proposed. We argue that they should be pursued in parallel rather than in an exclusive manner. First, central banks and supervisors could explore different approaches that can better account for the uncertain and nonlinear features of climate-related risks. Three particular research avenues (see Box 5 below) consist in: (i) working with non- equilibrium models; (ii) conducting sensitivity analyses; and (iii) conducting case studies focusing on specific risks and/or transmission channels. Nevertheless, the descriptive and normative power of these alternative approaches remain limited by the sources of deep and radical uncertainty related to climate change discussed above. That is, the catalytic power of scenario-based analysis, even when grounded in approaches such as non-equilibrium models, will not be sufficient to guide decision-making towards a low-carbon transition.

As a result of this, the second avenue from the perspective of maintaining system stability consists in “going beyond models” and in developing more holistic approaches that can better embrace the deep or radical uncertainty of climate change as well as the need for system-wide action (Aglietta and Espagne (2016), Barmes (2019), Chenet et al (2019a), Ryan-Collins (2019), Svartzman et al (2019)). 

Pages 42 – 43

Embracing deep or radical uncertainty therefore calls for a second “epistemological break” to shift from a management of risks approach to one that seeks to assure the resilience of complex adaptive systems in the face of such uncertainty (Fath et al (2015), Schoon and van der Leeuw (2015)).38 In this view, the current efforts aimed at measuring, managing and supervising climate-related risks will only make sense if they take place within a much broader evolution involving coordination with monetary and fiscal authorities, as well as broader societal changes such as a better integration of sustainability into financial and economic decision-making.

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