Climate Stress Testing: What Banks and Investors Need to Know

Climate Stress Testing: What Banks and Investors Need to Know

Climate stress testing is a way for banks, investors, and supervisors to examine how climate-related risks could affect financial performance under different future scenarios. It does not try to predict the future perfectly. Instead, it asks: what could happen to loans, portfolios, assets, capital, and profitability if climate risks become more severe or if the transition to a low-carbon economy happens quickly or disorderly?

For beginners, the key idea is simple: climate stress testing turns climate risk into a financial-risk exercise. It helps financial institutions understand how floods, heatwaves, carbon prices, regulation, energy transition, and market repricing could affect credit risk, market risk, operational risk, insurance risk, and investment value.

What Is Climate Stress Testing?

Climate stress testing is a forward-looking risk analysis. A bank or investor takes one or more climate scenarios and tests how those scenarios could affect financial exposures.

The Network for Greening the Financial System, or NGFS, explains that climate scenarios are not exact forecasts. They are plausible pathways that help policymakers, financial institutions, researchers, and businesses explore climate impacts and assess adaptation and mitigation strategies. The NGFS short-term scenarios technical documentation, published in 2025, describes the NGFS as a group of 144 central banks and supervisors and 21 observers as of 11 March 2025.

In practice, a stress test may ask questions such as:

• What happens to mortgage portfolios if flood risk increases?

• What happens to energy-sector loans if carbon prices rise?

• What happens to equity portfolios if markets suddenly reprice high-emission companies?

Physical Risk vs Transition Risk

Climate stress testing usually focuses on two major risk types: physical risk and transition risk.

Physical risk comes from the direct effects of climate change, such as floods, storms, droughts, wildfires, sea-level rise, and heatwaves. These risks can damage property, disrupt supply chains, reduce productivity, and affect borrowers’ ability to repay debt.

Transition risk comes from the shift toward a lower-carbon economy. It can include climate regulation, carbon pricing, new technologies, changing consumer behavior, litigation, and investor pressure. A company in a high-emission sector may face higher costs, lower demand, or asset write-downs if the transition accelerates.

The Bank of England’s climate scenario work has explored the resilience of UK banks and insurers to both the physical impacts of climate change and the transition to a net-zero economy. Its Biennial Exploratory Scenario used Early, Late, and No Additional Action scenarios, based on NGFS scenarios.

Why Banks Need Climate Stress Testing

Banks are exposed to climate risk through their borrowers, collateral, sectors, and geographies. For example, a bank may lend to companies in energy-intensive industries, finance real estate in flood-prone locations, or hold collateral that could lose value under severe weather events.

The European Central Bank’s 2025 analysis extended the EU-wide stress test by adding climate risk analysis for non-financial corporations. It incorporated both transition risk and acute physical climate risks into credit risk assessment using top-down models. The ECB found that both types of climate risk can have a moderate but consequential effect on banks’ capital ratios.

This is important because banks may look resilient under a traditional macroeconomic stress test but show different vulnerabilities once climate risk is included.

Why Investors Need Climate Stress Testing

Investors also need climate stress testing because portfolios can be exposed to sectors, assets, and companies that may be affected by climate transition or physical damage.

For example, an investor holding utilities, oil and gas, real estate, agriculture, transport, or insurance companies may want to understand how different climate pathways affect earnings, asset values, cost of capital, and long-term valuation.

Climate stress testing can help investors compare companies, assess portfolio concentration, identify high-risk sectors, test net-zero alignment, and understand whether current market prices reflect climate risk.

What Data Is Needed?

A climate stress test usually needs several types of data. These include emissions data, sector classification, geographic location, asset-level exposure, loan maturity, collateral information, company financials, energy use, transition plans, and scenario assumptions.

This is one reason climate stress testing is difficult. Climate data is still developing. The Basel Committee’s 2025 voluntary disclosure framework for climate-related financial risks acknowledges that the accuracy, consistency, and quality of climate-related data are evolving, and that users should consider disclosures holistically, including the strengths and shortcomings of the information.

In simple terms, climate stress testing is powerful, but it depends heavily on data quality and assumptions.

How a Climate Stress Test Works

A basic climate stress test follows a logical process.

First, the institution chooses a climate scenario, such as an orderly transition, delayed transition, or severe physical risk scenario.

Second, it maps exposures by sector, geography, borrower, asset class, or portfolio.

Third, it translates climate shocks into financial variables, such as default probabilities, asset values, revenue, costs, or credit losses.

Fourth, it calculates the impact on capital, profitability, liquidity, or portfolio value. Finally, it uses the results to improve risk management, strategy, disclosures, and decision-making.

The NGFS published an updated 2025 guide to climate scenario analysis, reflecting progress in scenario design, data, and modelling over the previous five years.

Common Beginner Mistakes

A common mistake is thinking climate stress testing gives one exact answer. It does not. It produces a structured view of possible outcomes under defined assumptions.

Another mistake is focusing only on long-term risks. The ECB notes that acute weather events, abrupt policy shifts, and rapid market repricing can occur at short notice and affect financial institutions’ balance sheets.

A third mistake is treating climate risk as separate from normal financial risk. In reality, climate risk often appears through familiar channels: credit losses, market losses, collateral damage, business disruption, and capital pressure.

Conclusion

Climate stress testing helps banks and investors understand how climate change and the low-carbon transition could affect financial resilience. It connects physical risk, transition risk, scenarios, exposures, and financial outcomes.

In simple terms: climate stress testing asks how climate shocks could affect money, risk, capital, and value. For banks and investors, it is becoming an essential tool for understanding future risk rather than reacting too late.