2. Literature Review
The literature studying the impact of climate related risk on the fiscal sector is relatively small but growing. There are two main lines of research and relevant hypotheses: 1) how do climate and weather variables affect sovereign risk or sovereign default, and 2) how do climate related and weather events affect the fiscal budget. An alternative classification of the relevant literature could be in terms of transition and physical risks. Transition risks refer to those associated with adjusting to a low-carbon economy, while physical risks are those emanating from adverse weather events.
In one of the first papers focusing on the impact of extreme weather events on budget balances in a panel of countries, Lis and Nickel (2010) find that the change in the budget balance as a percent of GDP following an extreme weather event is relatively modest at 0.23%. However, the impact increases up to 0.47% when they focus on the developing economies in their sample of 138 countries in total. Moreover, they find that for warmer countries, which tend to be more vulnerable to extreme weather events, the fiscal impact is larger. The authors use panel fixed effects, instrumental variables fixed effects, and GMM estimation in a panel of 138 countries over the period from 1985 to 2007, with the change in the budget balance as a dependent variable and different definitions of extreme weather events as the independent, while controlling for a set of macroeconomic, budgetary and political variables.
Melecky and Raddatz (2011) use a panel vector autoregression model to analyze the impact of three different types of disaster shocks on government expenditures, revenues, and deficits. More specifically, using annual data from 1975 to 2008 on high- and middle-income countries, the authors find that the three types of disaster shocks, namely geological, climatic and other disasters, have a negative impact on both output and deficit levels by leading to higher expenditures and lower revenues. This effect is greater for the lower-middle income countries of their sample. Interestingly, they also find that higher debt levels (associated with deficit deteriorations) signal better ability to borrow in capital markets rather than a constrained fiscal position. The authors also show that countries with stronger financial or insurance markets are able to better cope with the negative impacts on output from disaster shocks, although in different ways. These qualitative differences are worth exploring further as they have important policy implications.
Crifo et. al. (2017) find that environment, social and governance (ESG) indicators are important in explaining sovereign credit risk. Specifically, using data on 23 OECD countries over the period from 2007 to 2012 and employing a panel IV methodology with country and time fixed effects, they show that a higher ESG rating has a negative effect on sovereign bond spreads. However, the effect of these extra-financial metrics while significant, is not as important as credit ratings.
Kling et. al. (2018) use a panel ordinary least squares model linking sovereign bonds yields to measures of climate vulnerability and social preparedness, while controlling for standard macroeconomic variables. Using data for countries on the V 20 group of climate vulnerable countries the authors find evidence of a significant positive impact of climate vulnerability measures, such as dependency on natural capital or water dependency, on sovereign borrowing costs. Social preparedness on the other hand is associated with a negative impact on sovereign yields. Additionally, using a logistic model, they find evidence of a negative correlation between climate vulnerability and access to capital markets.
Bachner and Bednar-Friedl (2019) develop a computable general equilibrium model for Austria to analyze the impact of climate change on public budgets. The authors consider three climate scenarios with a model base year of 2008 and trace the impact in ten sectors of the economy for a 2 Celsius increase in temperature by 2050. They show that the overall effect of climate change on GDP, welfare, and budgets is negative. Moreover, as climate change related events are likely to require additional government aid, other publicly provided services are impacted negatively. When considering counterbalancing instruments and policies, they identify different channels with which climate change impacts affect public budgets. Higher capital taxes and cuts in transfers reduce welfare losses, while an increase in labor and output taxes has the opposite effect. Additionally, an increase in foreign borrowing reduces welfare losses more so than employing domestic counterbalancing policies, but at the expense of higher deficit and debt.
One of the first papers to study the effect of climate change on sovereign credit ratings is that of Cevik and Jalles (2020). Using a sample of 67 advanced and developing economies over the period from 1995 to 2017 and three estimation methodologies (OLS, binary-choice model, and 2SLS with instrumental variables), they examine the relationship between climate vulnerability and climate resilience on credit ratings, controlling for standard macroeconomic and fiscal variables. Their results based on the whole sample indicate that on average a 1% increase in climate vulnerability lead to a 0.23% drop in credit worthiness, while an increase of 1% in climate resilience leads to a 0.09% in credit rating. An important part of their analysis is then done by splitting the sample between advanced and developing economies. In line with other studies, the effects mentioned above are different in the two groups. More specifically, in advanced countries the effect of climate change vulnerability becomes insignificant, while in developing countries the effect is amplified. Climate change resilience is significant in both groups but the effect is again much larger for developing countries. Clearly, as the authors point out, these differences have significant implications for policy both at the national but also supranational levels. It will also be interesting to examine who and if this pattern changes as more countries may become climate vulnerable.
Beirne et. al. (2021a) study the effects of climate related risks on the pricing of sovereign bonds in a panel of 40 advanced and emerging economies using quarterly data from 2002 to 2008. Their findings indicate that both the immediate impact of climate risks (climate vulnerability) and resilience to climate risk have an important effect on the cost of foreign borrowing. They find the former to be more important than the latter. This affects disproportionally emerging economies many of which are more vulnerable to climate risks and may thus face a double challenge.
Focusing on six Southeast Asian economies which are more prone to climate stress, Beirne et. al. (2021b) estimate the links between climate vulnerability and resilience and sovereign bond yields. They use monthly data over the period from 2002 to 2018 and take two estimation approaches: country specific OLS regressions and a fixed effects panel model. Both approaches lead to the same main conclusion, namely that climate vulnerability has a significant positive impact on sovereign bond yields, while climate resilience has a negative but smaller effect. Reinforcing their results of their previous work stated above, the authors also point out how a vicious cycle can manifest in countries that face a higher climate risk. Higher sovereign yields increase the cost of borrowing needed to finance adaptation and resilience investment and a worsening of public finances.
A slightly different in focus but still related work is developed by Kling et. al. (2021) who focus on the impact of climate vulnerability on cost of debt and equity financing for private firms, as well as access to capital. The authors develop panel regressions and structural equations models with firm level data on 15,265 firms in 71 countries over the period from 1997 to 2017 and different measures of climate vulnerability based on the ND-GAIN index. They find that while climate vulnerability increases the cost of debt, the effect is insignificant for the cost of equity. The effect of the former also has an indirect effect through a negative impact on access to financing. This work to again emphasizes the uneven effects that countries who are more climate vulnerable will face despite the fact that they have not contributed by as much to climate change. This is an important point the authors make and deserves attention at the policy level, especially as climate policy should focus more on international cooperation.
Kizys et. al. (2021) further provide evidence of a positive relationship between temperature and sovereign bond yields. Using daily observations on 31 countries over the period from 1980 to 2020 and different maturities, the authors use panel regressions and find that on average a 10℉ increase in temperature leads to a 0.22 to 0.85 basis points increase in yields. Moreover, the also provide evidence of a non-linear, and more specifically quadratic, relationship between temperatures and bond returns.
Semet et. al. (2021) examine the relationship between sovereign bond spreads and ESG indicators. The authors identify 21 ESG metrics from a long list of relevant variables as the ones having the greatest impact on sovereign bond spreads. Their analysis covers the period from 2015 to 2020 and is based on 67 countries. Their results indicate that the environmental pillar is the most important one, followed by the governance and lastly the social pillar when looking at the whole sample. However, when looking at high vs. middle income groups, the transition risk is greater in the former group whereas the physical risk is greater in the latter. Finally, using a logit model they examine whether ESG indicators can predict a country’s credit rating, and find that the environmental is not significant.
Boehm (2022) constructs a measure of temperature anomalies, i.e. deviations from average temperatures, using monthly data on 54 emerging economies over the period from 1994 to 2018. He then examines the relationship between sovereign creditworthiness and temperature anomalies and precipitation. His findings, using OLS panel regressions, indicate that higher temperature anomalies lead to increases in sovereign risk in countries that are either warmer and/or lag with respect to different measures on institutional development. Finally, the author highlights the importance of a recurring pattern, namely that countries such as the ones in this sample (i.e. emerging economies) stand to experience more negative impacts of climate change (proxied by increases in temperature anomalies in this paper), even though they have not contributed the same to global CO2 emissions as more advanced economies. Therefore, in terms of policy recommendations, the focus should be on strengthening institutions and improving climate resilience by investing in adaptation strategies.
Building on their previous work
1 Cevik and Jalles (2022a) use a sample of 98 advanced and developing countries over the period from 1997 to 2017 to re-examine the relationship between sovereign bond yields and spreads and the ND-GAIN measures of climate vulnerability and resilience. The authors confirm their previous findings showing climate vulnerability as having a positive impact on both yields and spreads, whereas climate resilience has a negative one. Once again, this study also finds that the effects are greater in developing countries.
Cevik and Jalles (2022b) are perhaps the first to examine the relationship between climate change and sovereign defaults. The authors use a panel of 116 countries over the period from 1995 to 2017 and estimate the probability of sovereign default based as a function of climate vulnerability and resilience. Using a logit model in their baseline specification, they provide evidence of a strong positive impact of climate vulnerability of the probability of default, while climate resilience has a negative one. As in most previous studies, this one also finds evidence of differences among high and low-income counties, with the impact of the latter group being greater.
Assab (2023) studies how the urban heat island (UHI) effect and the urban forest cover can affect sovereign yields. The UHI effect refers to the higher land temperatures in urban areas as opposed to rural ones, as a result of human activity. The analysis is done for 68 countries over the period from 2008 to 2020. The author provides evidence of a negative impact of UHI on sovereign yields, which can be mitigated by the positive impact of urban forest. Moreover, the positive impact of urban forest cover is greater in countries with higher fiscal decentralization. The latter implies the importance of local policies when it comes to adaptation strategies. The impact of the UHI effect as well as of the urban forest cover deem more attention from researchers and should be further explored.
Cheng et. al. (2023) center their analysis on transition risks and examine whether these are reflected into the pricing of sovereign bond yields, as well as whether policies that address these risks can have a mitigating effect on sovereign bond pricing. The authors estimate a panel model with country and time fixed effects where sovereign yields are a function of a constructed measure of transition risks and a set of macroeconomic and fiscal control variables. Their results, based on a sample of 25 countries during the period from 1995 to 2018, indicate that there is a positive relationship between transition risks and sovereign bond yields, while policies aimed to address such risks can have a negative effect.
Along the same lines, Collender et. al. (2023) also focus on transition risks and how these impact sovereign yields and spreads. Their sample includes 39 countries over the period from 1999 to 2021. The authors break down transition risks into three main components: CO2 emissions, natural resources rents, and renewable energy consumption. These together with a set of macroeconomic control variables are used to explain sovereign yields and spreads in a panel setting over both the entire sample but also in two country groups (advanced and developing economies). Their results show a positive relationship between CO2 emissions and borrowing costs in both country groups. The impact of natural resources rents and renewable energy consumption is however different among the two groups. While lower natural resources rents are associated with lower borrowing costs in advanced economies, the relationship is reversed for developing ones. As for renewable energy consumption, the link is indirect for advanced economies but again reverses for developing ones.
Klusak et. al. (2023) use machine learning to simulate the impact of climate change, as proxied by rising temperatures due to higher CO2 emissions, to sovereign credit ratings. Their analysis, based on 109 countries, results in sovereign credit ratings that internalize the impact of climate change. These climate- adjusted ratings lead to substantial credit downgrades as early as 2030. However, if countries follow the Paris Climate Agreement and commit to following policies consistent with the 2℃ target of temperature increases, the impact can be substantially reduced and even eliminated. The authors also quantify the monetary impact of downgrades driven by climate change for both the sovereign and corporate debt. Under a scenario consistent with stricter climate policies the additional borrowing cost for sovereign debt is estimated to be from US$45 to $64 billion, whereas it rises to US$105 to $203 billion under a “business as usual” scenario. Similarly, for corporate debt the above ranges are US$10 to $17 and US$35 to $61 billion under the two scenarios. As the authors point out, the model should be extended to include political instability due to climate change, transition, and litigation risks.
An interesting question examined in Saxena and Singh (2023) is whether markets reward countries whose governments participate in climate agreements. To answer this, the authors examine the relationship between sovereign yields before and after participation in climate agreements using a difference-in-differences approach. Focusing on the Kyoto Protocol and the Paris Agreement, they find that investors indeed favor governments that participated in these agreements, with the effect being stronger in the case of the Kyoto Protocol. The role of incentives, which may be the reason why these effects are different, is an open question which the authors emphasize.
Sun et. al. (2023) revisit the relationship between climate risks and sovereign ratings. The authors employ a generalized logit ordered model with climate vulnerability and readiness as the two main explanatory variables, together with standard macroeconomic variables shown to affect sovereign ratings. In addition, a random forest model is used to compare the importance of the two climate variables relative to the other indicators. In line with previous study, their results show that climate vulnerability has a significant negative effect on sovereign ratings, while climate readiness a positive one. Both impacts are found to be higher for developing and high-damage countries.
Overall, the above literature review revealed that there is a strong link between sovereign risk and climate variables. Different authors have used different proxies for sovereign risk (e.g. yields on sovereign bonds, sovereign ratings) and several ways to proxy for climate change (e.g. rising temperatures, composite measures of resilience/vulnerability). The findings are fairly consistent across studies: the impact of climate related variables on sovereign risk is positive but there are important differences among different economies such as developed vs. developing. Therefore, we conclude that there is research space for further examining the possible uneven impact of climate related variables on sovereign risk by using an econometric approach that allows us to focus on non-linearities and to examine whether the relationship changes at percentiles other than the median (tail-dependence).