Sarah Duffy

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Ph.D. Candidate
Department of Economics
University of Oxford

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Hello! I am a PhD candidate in Economics at Oxford. I study the macroeconomic and financial effects of climate change and climate policy. My research combines structural models from international economics and finance with empirical evidence, utilising text based and machine learning methods. Previously, I was a PhD intern at the Bank of England.

I am on the 2025-2026 Job Market!

Research Papers

Climate Change, Adaptation, and Sovereign Risk
Job Market Paper

Abstract Many emerging markets face high borrowing costs and exposure to natural disasters. How will fiscal constraints affect the adaptation to, and therefore the losses from, climate change in such economies? A sovereign default model augmented with natural disasters and endogenous adaptation predicts that i) climate change increases borrowing costs, ii) adaptation reduces borrowing costs, and iii) default risk constrains adaptation. These economies suffer from an `adaptation trap': high borrowing costs restrict adaptation, leading to higher losses from disasters and higher borrowing costs in the future. To test these predictions I construct a novel measure of adaptation using text analysis to identify adaptation expenditures in government budgets. Consistent with the model, I document a robust positive relationship between sovereign ratings and adaptation as well as a positive causal effect of cyclone strikes on default risk that is attenuated by adaptation. The sovereign risk- adaptation channel is quantitatively important in the estimated model. In the Caribbean $10\%$ of GDP losses from cyclones are due to default risk. This loss increases with climate change but can be mitigated by debt relief policies.


The Carbon Premium and Policy Risk Exposure: A Text-Based Approach

Abstract Shifts in climate policy stringency have heterogeneous effects on firms’ profitability. Does the market price this risk? This paper provides new evidence on this question, utilising a supervised machine learning algorithm to construct a firm-level measure of climate policy risk exposure. Firms exposed to climate policy risk have negative abnormal returns on climate policy announcement days. I build a set of such dates and characterize abnormal return responses using Risk Factors discussions in 10-K filings. The algorithm uncovers predictors of policy risk exposure in the text which are used to construct an exposure score for each firm. This exposure score is correlated with emissions, environmental lobbying behaviour, and is predictive out of sample. Higher exposure is not associated with a premium. Green preference shifts are considered as a mechanism to rationalize this result. I find that empirically identified preference shocks can partly explain the lack of a climate policy risk premium.


Work in Progress

Climate Tariffs, Firm Heterogeneity, and Productivity
with Martin Bodenstein, Federico Di Pace, Aydan Dogan and Marco Garofalo

Abstract


Disasters and Global Imbalances
with Andrea Ferrero

Abstract


Market Neutrality and Climate Non-Neutrality
2023 Draft

Abstract Tilting central bank asset purchases towards green bonds - Green QE - has been suggested as a way for central banks to mitigate their environmental impact while supporting the transition to a low carbon economy. I use a two sector E-DSGE model with financial frictions and imperfectly substitutable green and brown bonds to assess this proposal. The model is calibrated to the Euro Area at quarterly frequency, incorporating empirical findings on the brown tilt of the ECB portfolio under the status quo `market neutrality' principle. Green QE is shown to achieve the same macro-stabilization outcomes as brown QE without the corresponding detrimental emissions. Moreover a shift in the ECB portfolio towards green bonds can lead to a substantial emissions decrease, at least in the short run. Turning to the question of transition risk, I show that a green QE rule can protect against the risk of a `green recession' caused by a sudden, unexpected increase in the carbon price.