The winter of 2023/24 was one of the wettest on record for the U.K., bringing widespread flooding and disruption, contributing to record breaking weather-related insured losses according to the Association of British Insurers.[1] For many in the reinsurance industry, that season underscored just how vulnerable Europe is to prolonged periods of heavy rain.
Understanding how and why winter rainfall is changing is challenging because natural variability masks the signal. But new research through the Willis Research Network shows that a clear climate change signal is now detectable, with important implications for risk and resilience, and on the way we think about the future of winter rainfall across Europe.
We take you through four ways U.K. winter storms are changing, what’s driving these shifts, and why it matters for how we model and manage future risk.
Physics dictates that the amount of moisture the atmosphere can hold increases at 7% per degree of warming
Both dynamical and thermodynamical drivers are expected to change with global warming, although thermodynamical changes are more robust. Physics dictates that the amount of moisture the atmosphere can hold increases at 7% per degree of warming. Changes to dynamical drivers are more complex and uncertain, although models indicate a likely strengthening of the Atlantic jet stream in the winter.
Understanding observed and projected changes in winter rainfall requires understanding both these drivers separately, since they are influenced by different processes.
The goal is not to replace models but to broaden the toolkit, bringing science closer to the realities of risk management.
Why this matters for risk managers, insurers and reinsurers
For reinsurers and their clients, the key message is that winter rainfall is intensifying, and the pace of change is faster than global climate models suggest.
This has several important implications:
- Future projections of rainfall and flooding extremes from global climate models are underestimates and client exposure may be higher than these models imply. How are you testing infrastructure and portfolio decisions against the most recent 10–20 years of observed flood experience, not only against global climate model averages?
- Model-based views of near-term risk may also be underestimates if recent intensification of rainfall has not been incorporated; catastrophe models may need updating. When was your model baseline last reviewed, and how are you engaging vendors to capture observed shifts since the calibration period?
- Recommendations on climate adaptation and flood mitigation will need to account for the underestimation of rainfall intensification in both the near and long term. If I take a 1-in-200 year event from my model, is that really 1-in-200 in 2026, or was it 1-in-200 in 1996?
Footnotes
- The Association of British Insurers. More action needed to protect properties as adverse weather takes record toll on insurance claims in 2024. (2025). Return to article
- Carruthers, J. G., et al. Climate Models Tend to Underestimate Scaling of UK Mean Winter Precipitation With Temperature. (2026). Return to article
- Kahraman, A., et al. Quasi-Stationary Intense Rainstorms Spread Across Europe Under Climate Change. (2021). Return to article
- Manning, C., et al. Projected increase in windstorm severity and contribution from sting jets over the UK and Ireland. (2023). Return to article
- Kahraman, A., et al. Climatology of severe hail potential in Europe based on a convection-permitting simulation. (2024). Return to article
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