Under-preparing for severe climate risks can cost the UK far more than over-preparing, experts warn
Experts in climate, nature, health, national security, and financial risk have joined forces to call for a more integrated approach to government climate and nature risk assessments. In a Comment published in Nature Climate Change, they warn that conflicting advice can give policymakers very different pictures of the severity of the risks ahead, making it harder to judge how seriously to act and how much to spend.
The call comes after a summer that was, provisionally, the UK’s hottest on record, and that ended with almost three-quarters of England in drought. July 2026 was England’s driest July since at least 1836 with 10% of average rainfall. This led to hosepipe bans covering around 30 million people, over 1,100 wildfires, and a winter wheat, oat, and spring barley harvest estimated to be up to 19% below their five-year average.
Deciding how to prepare for climate and nature risks, and how much to spend, draws on two approaches developed for very different purposes. National security assessments consider reasonable-worst-case scenarios, while economic modelling typically focuses on central estimates and cost-benefit calculations. Both inform decisions on fiscal risk, public spending, adaptation, food and security, yet governments generally have no common framework for reconciling them.
Using a reasonable-worst-case approach, a UK national security assessment published in January 2026 concluded with high confidence that global ecosystem degradation and collapse threaten UK security and prosperity. It warned that the world is already experiencing crop failures, intensified natural disasters, and infectious disease outbreaks, and that “every critical ecosystem is on a pathway to collapse”.
Meanwhile, the Office for Budget Responsibility (OBR), which advises Parliament on fiscal sustainability, bases its climate damage estimates on central scenarios rather than reasonable worst cases and can imply that economic consequences are more manageable. In 2024, the OBR estimated that climate damage would leave UK GDP around 5% lower in a scenario where global temperatures rise to just under 3°C by the 2100. Its July 2025 assessment increased that to around 8%, while acknowledging that some potentially severe risks remain difficult to quantify.
The authors say the problem is not unique to the UK. In its 2023 Climate Economic and Fiscal Assessment, New Zealand’s Treasury reported that its modelling suggested the New Zealand economy is “relatively resilient” to more frequent droughts and storms, while the country’s 2023 defence assessment named climate change as one of the two principal challenges to its defence interests. Both fed the same government’s decisions on spending and preparedness, with no shared framework for integrating advice.
Professor Paul Behrens, Oxford Martin School, University of Oxford, said: “Climate risks don’t happen in isolation. This summer’s extreme heat and drought affected farms and food production, put pressure on water supplies and ecosystems, and had consequences for people’s health. Those impacts can ripple out into food prices, infrastructure and the wider economy. Looking at each risk separately can seriously underestimate the overall impact. We need a combined approach where the outputs of risk-assessments and economic modelling can complement one another in a period of increasing crises,”
Drawing on decades of military experience, Lieutenant General (retd) Richard Nugee, of the University of Oxford’s Climate Change and (In)Security Project, describes the importance of a consistent approach to complex risks: “In the military, when planning for future operations or strategies, a well thought through, coherent framework is used to identify all the factors involved, and derive the best, or least-worst, course of action to take. Given the gravity of the consequences of decisions, it is imperative to have a consistent and comprehensive approach that does not underestimate the challenge, and when the situation changes, so does the plan.”
Preparing for higher levels of risk need not mean wasted investment. Where potential damage is severe and irreversible, being under-prepared can cost far more than preparing for events that turn out to be less damaging. Some precautionary measures can also bring wider benefits even if the worst-case scenario never materialises.
Professor Nathalie Seddon, Department of Biology, University of Oxford points to the role nature can play in protecting people from climate extremes: “This summer showed how closely the condition of our rivers, soils and ecosystems is tied to food, water and people’s health. Restoring nature is therefore part of preparing for climate risk. Reconnecting rivers to their floodplains, rewetting peatlands and restoring wetlands can slow and store water, reducing flood peaks downstream while helping landscapes hold water through drought and giving wildlife room to recover. These measures can strengthen the resilience of the interconnected social and ecological systems on which we all depend, across a wide range of possible futures.”
The proposed approach would bring expert analysis alongside model estimates, helping decision-makers account for serious risks that are difficult to quantify. It would also bring climate, nature, food, health, economic and security risks into a shared framework, so risks identified in one area are not overlooked elsewhere.
The paper also identifies “no-regret” actions that are worth taking even if the worst-case scenario never happens. Improving energy efficiency, for example, can cut emissions while delivering other benefits, including greater resilience and reduced exposure to some price and supply shocks.
Governments already plan for some severe risks this way. UK pandemic planning has been built around reasonable-worst-case scenarios.
For climate and nature, the experts say governments should not have to wait for an equivalent shock to find out they were under-prepared.
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Notes to Editors
Paper: Governments must reconcile dissonant climate assessment approaches, published in Nature Climate Change.
Authors:
- Professor Paul Behrens, Oxford Martin School, University of Oxford
- Dr Jesse F. Abrams, Global Systems Institute, University of Exeter
- Professor Hugh Montgomery OBE, Department of Medicine, University College London
- Lieutenant General Richard Nugee CB CVO CBE, former Ministry of Defence climate lead and member of the UK Government's Climate Security Taskforce
- Professor Nathalie Seddon, Department of Biology, University of Oxford
- Sandy Trust, Baillie Gifford & Co
DOI: https://doi.org/10.1038/s41558-026-02736-4
Paper link: https://www.nature.com/articles/s41558-026-02736-4
Publication date: 29/09/26
A note on OBR estimates: The Comment cites the Office for Budget Responsibility’s September 2024 figures. In July 2025 the OBR raised its estimate for a scenario of just under 3°C of warming to around 8% of GDP by the early 2070s, drawing on Network for Greening the Financial System scenarios whose damage function rests on a study retracted by its authors in December 2025 and now under revision. The Comment discusses this.
FAQs
1. What evidence is there that relying on average or central estimates can underestimate the severity of plausible climate outcomes?
The paper cites climate modelling showing a wide range of possible outcomes at the same level of warming. At 2°C, severe outcomes in some sectors can exceed the average projected outcome at 3°C or even 4°C. Further details and supporting evidence can be provided to journalists.
2. What important climate and nature risks can be missing from economic estimates used to inform government decisions?
The paper discusses limitations and omissions including catastrophic risks, climate tipping points, sea-level rise, and damage to ecosystems and human health. The authors can explain what these omissions mean and why they matter for decision-making.
3. Does government already have mechanisms for bringing economic, climate, nature and national security risk assessments together?
The paper acknowledges existing whole-of-government approaches but argues that shared methods for integrating these different forms of evidence into mitigation and adaptation decisions remain lacking. The authors can discuss what currently exists, where they see the gaps and how their proposed framework differs.
4. What would change in practice if government adopted the authors' recommendations?
The authors can explain how confidence-tiered expert judgement, different treatment of no-regret and high-stakes decisions, and a shared framework for interconnected risks could affect decisions about preparedness, resilience and public spending.
Media spokespeople:
Professor Paul Behrens
Professor Paul Behrens is a British Academy Global Professor at the Oxford Martin School, University of Oxford, and an expert on food systems, sustainable diets, climate change and environmental sustainability. His research examines how food systems can be transformed to improve human health, strengthen resilience and reduce environmental impacts in a rapidly changing world.
His work has been published in journals including Nature Food, Nature Sustainability, Nature Energy, PNASand Nature Communications. He is author of The Best of Times, The Worst of Times: Futures from the Frontiers of Climate Science and co-editor of Food and Sustainability. He contributed to the National Emergency Briefing, featured in the People's Emergency Briefing film, and regularly advises policymakers. He was winner of the 2023 Frontiers Planet Prize.
Professor Nathalie Seddon
Professor Nathalie Seddon is Professor of Biodiversity in the Department of Biology at the University of Oxford and Founding Director of the Nature-based Solutions Initiative. Her work focuses on the role of nature-based solutions in social and ecological flourishing and on strengthening the influence of biodiversity science and traditional knowledge on climate and development policy.
She advises governments and the private sector on nature-based solutions and served on the Adaptation Committee of the UK’s Climate Change Committee from 2022 to 2025, where she led its work on the natural environment and agriculture.
Lieutenant General (retd) Richard Nugee CB CVO CBE
Lieutenant General Richard Nugee spent 36 years in the British Army in joint, single-service and international appointments. He led work on the Ministry of Defence's Climate Change and Sustainability Strategic Approach before becoming the MOD's Non-Executive Director for Climate Change and Sustainability in 2021.
He previously served for four years as Chief of Defence People and is currently a Non-Executive Member of the Defence Safety and Environment Committee. He is also a member of the UK Government’s new Ministerial Taskforce on Climate, Nature and Security.
Journal
Nature Climate Change
Article Title
Governments must reconcile dissonant climate assessment approaches
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