1. ABOUT THE DATASET ------------ Title: High-impact low-likelihood climate risks in the UK Creator(s): Nigel Arnell Organisation(s): University of Reading. Rights-holder(s): University of Reading Publication Year: 2026 Description: This data set contains a series of indicators of future climate risk at the regional scale across the United Kingdom, for a suite of high-impact low-likelihood climate scenarios. The indicators cover heat and cold extremes, agricultural risks, wildfire danger and river runoff. The scenarios describe enhanced warming above 4oC, rapid reductions in aerosol emissions, volcanic eruptions, strong Arctic amplification, and major changes to the ocean circulation. Indicators are also calculated for scenarios assuming increases in global average temperature of 3 and 4oC by 2100. The indicators are designed to provide information on the potential high-impact low-likelihood climate risks facing the UK, to aid in adaptation and resilience planning. Cite as: Arnell, N.W. (2026): High-impact low-likelihood climate risks in the UK. University of Reading. Dataset. https://doi.org/10.17864/1947.xxxxxxx. Related publication: Arnell, N.W. et al. (2025) High-impact low-likelihood climate scenarios for risk assessment in the UK. Earth s Future 13, e2025EF006946. Arnell, N.W. et al. (2026) Potential high-impact low-likelihood climate risks in the UK. Under review Arnell, N.W. et al. (2021) Changing climate risk in the UK: a multi-sectoral analysis using policy-relevant indicators. Climate Risk Management 31, 100265 Contact: Nigel Arnell n.w.arnell@reading.ac.uk 2. TERMS OF USE ------------ Copyright 2026 University of Reading. This dataset is licensed under a Creative Commons Attribution 4.0 International Licence: https://creativecommons.org/licenses/by/4.0/.] 3. PROJECT AND FUNDING INFORMATION ------------ Title: Climate Resilience - high impact storylines and scenarios for risk assessment and planning Dates: 2018-2025 Funding organisation: Met Office Grant no.: CR20-4 4. CONTENTS ------------ File listing cri_file_description.pdf description of data file naming convention and format, including list of indicators admin-region-names.csv list of administrative region codes HILL-climate.zip HILL-heat-cold.zip HILL-agriculture.zip HILL_fire-water.zip Zip files containing data files by indicator and scenario 5. METHODS ----------- The climate scenarios are described in Arnell et al. (2025), and the indicators described in Arnell et al. (2021; 2026). Each indicator is calculated at a raw spatial resolution of 12x12km using gridded observed weather data to describe the current (1981-2010) baseline and perturbing the gridded observations using climate change scenarios. Regional average indicators are calculated by taking a weighted average of all the 12x12km grid cells within a region, with weights varying between indicators.