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Journal articleAtoufi A, Zhu L, Lefauve A, et al., 2025,
Three-layer stratified exchange flows: hydraulically controlled transition to turbulence
, JOURNAL OF FLUID MECHANICS, Vol: 1016, ISSN: 0022-1120 -
ReportZachariah M, Saeed F, Clarke B, et al., 2025,
Climate change intensified heavy monsoon rain in Pakistan, exacerbating urban floods that impacted highly exposed communities
, Publisher: Centre for Environmental Policy -
Journal articleToumi R, Sparks N, 2025,
The Hurricane Damage Index (HurDI)
, Journal of Catastrophe Risk and Resilience, Vol: 03, ISSN: 3049-7604Statistical hurricane risk assessments make long-term multi-decadal stationary climate assumptions, but there is large hurricane variability in the risk. It would be useful to also better estimate the “current” risk. The hurricane damage index (HurDI), is proposed as a measure of the underlying non-stationary risk. The HurDI is defined as the normalised annual average damage calculated with a stochastic wind only model, a single damage function, and uniform exposure across the continental U.S. The stochastic model is climate conditioned by weighting the historical basin hurricane counts, potential intensity, and tracks. The weights are chosen to give the best persistence forecast for each parameter for the next five years. There has been a substantial increase of the hurricane risk as measured by the HurDI. In 2024, the index was at a record high of 188, with a reference value of 100 in 1989. The HurDI is a dynamic view of risk based on the hurricane variability only and can be compared to U.S. property catastrophe reinsurance rates. There are periods of varying difference between the rates and the HurDI reflecting the volatile market cycles.
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Journal articleRoulston M, Kaivanto K, Toumi R, 2025,
Tracking evolving views of the 2024 Atlantic hurricane season with an expert prediction market
, Weather, Vol: 80, Pages: 277-280, ISSN: 0043-1656Before the 2024 Atlantic hurricane season began, the consensus was that it would be one of the most active seasons in history. However, a prolonged quiet period during late August and early September possibly led forecasters to question these predictions, before later activity fulfilled the season’s high expectations. The CRUCIAL initiative ran a ‘prediction market’ during 2024 which allowed experts to bet on the number of hurricanes. Prices in this market provide an insight into how views changed during the season. Prediction markets can efficiently aggregate the judgements of multiple experts and provide more up-to-date information than periodically issued forecasts.
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Journal articleWidana Arachchige EL, Zhou W, Toumi R, et al., 2025,
Projected tropical cyclone genesis and seasonality changes in the Northern Hemisphere under a warming climate
, npj Climate and Atmospheric Science, Vol: 8, ISSN: 2397-3722The impact of global warming on future tropical cyclone (TC) development is substantial; however, the predictability of TC genesis remains uncertain. In this study, we investigate projected changes in TC genesis on a regional scale over the North Atlantic (NA) and western North Pacific (WNP) ocean basins, focusing on TC seasonality through bias-corrected model simulations. Our study unveils a weakening of peak TC genesis (August-October; ASO) at lower latitudes under a high-emission scenario, along with a strengthening of TC peak (July-September; JAS) at higher latitudes. Most importantly, positive vertical velocity (ω) in the mid-troposphere (500 hPa) plays a dominant role in weakening the TC peak in the tropics, while weak vertical wind shear (VWS) in the subtropics facilitates TC development. Our study elucidates the impact of climate change on the regional environment and the ensuing possible changes in TC seasonality, offering essential insights into future projected TC genesis in the Northern Hemisphere.
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ReportZachariah M, Ceballos-Bonilla LI, Sepúlveda-Berrío J, et al., 2025,
Growing exposure and uncertain rainfall trends highlight the critical need for climate resilience in Colombia and Venezuela
, Publisher: Centre for Environmental Policy -
Journal articleOluleye G, McLaughlin S, Steen E, et al., 2025,
Blending interventions to achieve green hydrogen cost competitiveness for industrial decarbonisation
, International Journal of Hydrogen Energy, Vol: 144, Pages: 1343-1357, ISSN: 0360-3199Industrial decarbonisation can be supported by green hydrogen as a fuel and feedstock, but its cost remains too high to compete with natural gas. In this study, the achievement of cost competitiveness for green hydrogen is examined through a combination of internal interventions, including the reduction of electrolysis costs via waste heat sales to district heating networks and the use of curtailed wind, alongside external interventions such as market-based policies and sustainability-linked bonds. A novel temporal market penetration assessment model has been developed and applied to evaluate the impact of these interventions, both individually and in combination, on achieving cost parity. The methodology has been implemented in a UK case study to assess these dynamics within the energy landscape and policy framework. The findings indicate that cost reductions of 17.5 % can be achieved through hydrogen from curtailed wind, while waste heat utilisation contributes a 24.7 % reduction. Existing policy measures are found to have the potential to lower costs by 39 %. A total cost reduction of 78 % is observed when interventions are blended, with green hydrogen from curtailed wind projected to reach cost parity with natural gas by the mid-2030s under high natural gas price scenarios. The feasibility of blended interventions in facilitating the industrial adoption of green hydrogen is thereby demonstrated.
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Journal articleYang Y, Toumi R, 2025,
Large dynamic contributions to tropical cyclone precipitation with increasing sea surface temperature
, Environmental Research Letters, Vol: 20, ISSN: 1748-9326 -
Journal articleYe H, Favero S, Tyrrell H, et al., 2025,
Progress and Challenges in Electrochemical Glycerol Oxidation: The Importance of Benchmark Methods and Protocols
, CHEMCATCHEM, Vol: 17, ISSN: 1867-3880 -
Journal articleDavids D, Grant N, Mittal S, et al., 2025,
Assessing a mixed hydrogen economy for resilient net-zero using energy system modelling
, International Journal of Hydrogen Energy, Vol: 138, Pages: 1092-1103, ISSN: 0360-3199Low-carbon hydrogen will play a key role in the portfolio of alternative fuels towards climate targets. However, there are gaps in determining how deploying different hydrogen colours and production pathways contributes to achieving climate goals in a jurisdiction, including the economic impact on the energy system, the wider system, and the impact on the final energy mix. This work is the first to perform a detailed analysis of the interrelation between blue hydrogen, green hydrogen (onshore and offshore produced) and other hydrogen colours using an energy system model. Results show that for scenarios where blue hydrogen and green hydrogen are not deployed, green hydrogen is not deployed, blue hydrogen is not deployed, and blue hydrogen, onshore and offshore green hydrogen are deployed, have energy system costs 0.94 %, 0.32 %, 0.06 % and −0.1 % respectively from a reference with the base hydrogen types, blue and only onshore green available. Our optimum 'Mixed Hydrogen Economy' scenario has lowest decarbonisation costs by 2050 when net-zero emissions is achieved and ensures diversity of energy supply to boost energy security. Results emphasise the hydrogen economy is most pronounced when all available and sustainable hydrogen production options are deployed. The findings contribute towards evaluating the impact of hydrogen deployment in low-emissions scenarios.
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ReportKew S, Drost Jensen C, Björnsson H, et al., 2025,
Climate change drives record-breaking heat in Iceland and Greenland challenging cold adapted ecosystems and societies
, Publisher: Centre for Environmental Policy -
ReportZachariah M, Reid K, King A, et al., 2025,
Mixed rainfall trends highlight the importance of climate adaptation in coastal New South Wales
, Publisher: Centre for Environmental Policy -
Journal articleFuertes E, Konstantinoudis G, van der Plaat D, et al., 2025,
Vulnerability to pollen-related asthma hospital admissions in the UK Biobank: a case-crossover study
, Allergy, ISSN: 0105-4538 -
Journal articleTheokritoff E, Lejeune Q, Costa HP, et al., 2025,
Climate overshoot implications for local adaptation planning
, Climate Policy, ISSN: 1469-3062As global warming increases, the topic of overshoot, understood as the temporary exceedance of the 1.5°C limit of the Paris Agreement, is gaining prominence both in scientific and political spheres. However, overshoot and its implications for adaptation in the short – and long-term remain unexplored. In this Perspective, we reflect on the current use of global climate scenarios and local impact projections in science-based adaptation planning. The risks arising from overshoot scenarios in relation to the transgression of limits to adaptation and impact irreversibility are highlighted. We find that the prospects of potential long-term impact reversibility may have limited relevance in most adaptation decision-making contexts, indicating that it might be peak warming, rather than a long-term outcome, that determines adaptation needs and costs. While overshoot may not be relevant for short-term planning, it should be considered for long-term plans and policies, for example for infrastructure-based measures and for irreversible impacts such as sea-level rise. Key insights from adaptation practitioners in four diverse urban vulnerability contexts (Bodø, Lisbon, Nassau, Islamabad) are presented on how these risks are perceived and integrated (or not) into local planning and policy-making. We find that current adaptation planning must be extensively evaluated against a wider set of future global climate outcomes to incorporate risks of transgression of local limits to adaptation and overshoot. To this end, data gaps on adaptation limits and impact reversibility need to be filled and capacity building needs on climate scenarios, overshoot and related concepts for local adaptation practitioners should be addressed.
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Journal articleChen J, Toumi R, Zhang L, et al., 2025,
Radial rainfall pattern changes of intense over‐ocean tropical cyclones under global warming: insights from an MRI HighRes CMIP6 simulation
, Geophysical Research Letters, Vol: 52, ISSN: 0094-8276Tropical cyclone (TC) rainfall is an important hazard. Radial rainfall patterns of intense over‐ocean TCs under global warming are investigated using the MRI HighRes Coupled Model Intercomparison Project Phase 6 simulation with the SSP5‐8.5 high‐emission scenario. These patterns are characterized by four parameters: rainfall at the cyclone center (To), maximum rainfall (Tm), radius of maximum rainfall (Rm), and e‐folding radius (Re). We find Tm strongly correlates (r = 0.8) with a moisture convergence proxy—boundary‐layer maximum wind times column moisture divided by the radius of maximum wind—across differentintensities and under climate change. Under warming, mean Tm and To increase by 8.65%/K and 8.86%/K, while Rm and Re shrink by 1.03%/K and 1.79%/K, respectively. Notably, under warming, Tm exhibits greater sensitivity to TC intensity, and its increases are mainly attributed to column moisture increase.
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Journal articleFu H, Cenedese C, Lefauve A, et al., 2025,
A laboratory analogy for mixing by shallow cumulus convection
, JOURNAL OF FLUID MECHANICS, Vol: 1011, ISSN: 0022-1120- Cite
- Citations: 1
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ReportClarke B, Otto F, Pinto I, et al., 2025,
Effective emergency management prevented larger catastrophe after climate change fueled heavy rains in Central Mississippi river valley
, Publisher: Centre for Environmental Policy -
Journal articleRai U, Chen J, Oluleye G, et al., 2025,
Stochastic optimisation model to optimise the contractual generation capacity of a battery-integrated distributed energy resource in a balancing services contract
, Energy, Vol: 322, ISSN: 0360-5442Popular heuristic approaches applied by demand response aggregators often use conservative tactics and may fall short of the contractual generation capacity of a distributed energy resource (DER) allocation in a balancing services (BS) contract. Hence, the possibility of optimising revenue remains generally unexplored. This research presents a novel framework for aggregators by employing a two-stage stochastic mixed integer nonlinear programming model to tackle site electricity demand unpredictability and the uncertainty of short-term operating reserve (STOR) calls to find the optimal generation capacity of a diesel generator (DG) to contract in STOR service. In the first stage, K-means clustering for innovative segmentation and rigorously categorising half-hourly site electricity demand data into optimal demand bins is employed. In the second stage, the model integrates a behind-the-meter battery energy storage system (BESS) to enhance performance and evaluate scenarios with and without BESS. Additionally, the study evaluates the effects of varying BESS capacities to enhance the contractual capacity of the DG, resulting in significantly improved revenue. A rigorous sensitivity analysis of penalty cost, utilization payment, and storage capacity ensures the robustness of the model across varied conditions. Results show the site revenue increases between 7.91 % and 20.27 % compared to the deterministic MIQCP approach previously employed.
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ReportBarnes C, Lee J-Y, Yang Y-M, et al., 2025,
Climate change made weather conditions leading to deadly South Korean wildfires about twice as likely
, Publisher: Centre for Environmental Policy -
Journal articleChen A, Wang J, Toumi R, et al., 2025,
Impact of tropical cyclone precipitation on fluvial discharge in the Lancang‒Mekong river basin
, Geophysical Research Letters, Vol: 52, ISSN: 0094-8276Tropical cyclone precipitation (TCP) and associated floods have caused widespread damage globally. Despite growing evidence of significant changes in the activity of tropical cyclones (TCs) in recent decades, the influence of TCs on regional flooding remains poorly understood. Here, we distinguish the role of TCs in fluvial discharge by explicitly simulating discharge with and without observed TCP in the Lancang‒Mekong River Basin, a vulnerable TC hotspot. Our results show that TCs typically contributed approximately 30% of annual maximum discharge during 1967–2015. However, for rare and high-magnitude floods (long return periods), TCs are the dominant driver of extreme discharge events. Moreover, spatial changes in TC-induced discharge are closely related to changes in TCP and TC tracks, showing increasing trends upstream but decreasing trends downstream. This study reveals significant spatiotemporal differences in TC-induced discharges and provides a methodology for quantifying the role of TCs in fluvial discharge.
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ReportKimutai J, Dieudonne Nsadisa F, Ayabagabo P, et al., 2025,
High vulnerability and exposure main driver behind Kinshasa’s deadly floods following heavy, but not unusual rainfall
, Publisher: Centre for Environmental Policy -
ReportClarke B, Otto F, Barnes C, et al., 2025,
Extraordinary March heatwave in Central Asia up to 10°C hotter in a warming climate
, Publisher: Centre for Environmental Policy -
ReportZachariah M, Rivera JA, Sörensson AA, et al., 2025,
Consecutive extreme heat and flooding events in Argentina highlight the risk of managing increasingly frequent and intense hazards in a warming climate
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OtherLinden P, Atoufi A, Lefauve A, et al., 2025,
Hydraulic control, turbulence and mixing in stratified buoyancy-driven exchange flows
<jats:p>Buoyancy-driven exchange flows in geophysical contexts, such as flows through straits, often create a partially-mixed intermediate layer through mixing between the two stratified counterflowing turbulent layers. We present a three-layer hydraulic analysis of such flows, highlighting the dynamical importance of the intermediate layer. Our model is based on the viscous, shallow water, Boussinesq equations and includes the effects of mixing as a non-hydrostatic pressure forcing. We apply this shallow-water formulation to direct numerical simulations of stratified inclined duct (SID) exchange flows where turbulence is controlled by a modest slope of the duct. We show that the nonlinear characteristics of the three-layer model correspond to linear long waves perturbing the three-layer mean flow, and predict, in agreement with recent experimental observations in SID, hydraulically-controlled regions in the middle of the duct, linked to the onset of instability and turbulence. We also provide the first evidence of long-wave resonance, as well as resonance between long and short waves, and their connection to transitions from intermittent to fully developed turbulence. These results challenge current parameterisations for turbulent transport in stratified exchange flows, which typically overlook long waves and internal hydraulics induced by streamwise variations of the flow.</jats:p>
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OtherTheokritoff E, Sparks N, Otto F, et al., 2025,
Building a global and rapid event impact attribution framework
<jats:p>While event attribution has made considerable progress in the last two decades, event impact attribution, which calculates the attributable share of impacts from extreme weather events, remains challenging. Impacts result from the interaction between the intensity of hazards, the exposure of affected areas and the vulnerability of individuals, infrastructures and the environment. Across different types of extreme weather events, impacts and world regions, a wide range of datasets and approaches need to be considered to tackle this complex and interdisciplinary field of research.Here, we aim to develop simple methods that can be deployed rapidly and globally to estimate attributable impacts in the aftermath of extreme weather events. We will present initial work on attributing direct economic impacts from tropical cyclones and on an updated global physical asset database used in this context.This initiative produces near-real-time results that can be communicated in a timely manner to a broad audience, raising awareness about the impacts of extreme weather and the role of climate change. It ultimately seeks to provide valuable information on losses and damages and levels of adaptation, which can be instrumental for policymaking, climate justice and preparing societies for future extremes.</jats:p>
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OtherTheokritoff E, Sparks N, Otto F, et al., 2025,
Tracking losses and damages from extreme weather events
<jats:p>While the field of event impact attribution is still relatively nascent, diverse methodologies and datasets are starting to be used to put numbers on the share of additional impacts that occur due to climate change during extreme weather events. The growth of this body of evidence has implications for climate litigation as these studies can be starting points for legal cases centred around specific climate change impacts, such as heat-related mortality or economic costs of extreme weather.As we work towards operationalising a tracker that will provide timely estimates of losses and damages from extreme weather events globally, we aim to present results from our initial rapid studies conducted over the past year. We will reflect on the potential implications of the increasing availability of loss and damage information and the broader need for communication and awareness raising around these issues. We also plan to highlight prevailing methodological challenges and areas of research to be advanced in the near future that are relevant for legal efforts.</jats:p>
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OtherLefauve A, Bassett C, Plotnick D, et al., 2025,
The structure of stratified mixing by shear instability in baroclinically forced shear flows
<jats:p>We present observational data from the mouth of the Connecticut River, a shallow salt-wedge estuary characterised by intense interfacial mixing. The motivation is to better understand, and ultimately predict, density-stratified turbulent mixing driven by shear instabilities at high Reynolds numbers (Re > 10^5). Such processes span an immense turbulent energy cascade across eight orders of magnitude, from coherent instabilities at kilometre scales to the smallest mixing eddies at micrometre scales. Using multi-beam echo-sounding imagery, we reveal the spatial structure and temporal evolution of turbulent mixing with unprecedented detail. During the flood tide, large-scale topography and hydraulics cause the pycnocline to slope, which triggers, through baroclinic forcing, primary shear instabilities in the form of long trains of Kelvin-Helmholtz billows. Our data demonstrate that at Re ~ 5x10^5, mixing occurs primarily by turbulence in the braids connecting the cores of the billows rather than within the cores themselves. This secondary 'braid turbulence' is continuously forced by the secondary baroclinic generation of shear within the sloping braids. This finding challenges the prevailing paradigm built upon direct numerical simulations (DNS) at lower Reynolds numbers (Re ~ 10^3-10^4), where mixing is thought to occur primarily by overturning in the billow cores. This distinction is a significant shift in understanding the high-Re turbulent cascade in mixing hotspots, with potential implications for mixing parameterisations in the coastal ocean.</jats:p>
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OtherLefauve A, Zhu L, Jiang X, et al., 2025,
New insights into experimental stratified flows obtained through a physics-informed neural network
<jats:p>We develop a physics-informed neural network (PINN) to significantly augment state-of-the-art experimental data of stratified flows. A fully connected deep neural network is trained using experimental data in a salt-stratified inclined duct (SID) experiment. SID sustains a buoyancy-driven exchange flow for long time periods, much like an infinite gravity current. The data consist of time-resolved, three-component velocity fields and density fields measured simultaneously in three dimensions at Reynolds number= O(10^3) and at Prandtl or Schmidt number = 700 [1]. The PINN enforces incompressibility, the governing equations for momentum and buoyancy, and the boundary conditions at the duct walls. These physics-constrained, augmented data are output at an increased spatio-temporal resolution and demonstrate five key results: (i) the elimination of measurement noise; (ii) the correction of distortion caused by the scanning measurement technique; (iii) the identification of weak but dynamically important three-dimensional vortices of Holmboe waves; (iv) the revision of turbulent energy budgets and mixing efficiency; and (v) the prediction of the latent pressure field and its role in the observed asymmetric Holmboe wave dynamics. These results mark a significant step forward in furthering the reach of fluid mechanics experiments, especially in the context of stratified turbulence, where accurately computing three-dimensional gradients and resolving small scales remain enduring challenges.References[1] L. Zhu, X. Jiang, A. Lefauve, R. R. Kerswell, and P. F. Linden. New insights into experimentalstratified flows obtained through physics-informed neural networks. J. Fluid Mech., 981:R1, 2024.</jats:p>
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ReportClarke B, Zachariah M, Pinto I, et al., 2025,
Increasing extreme rainfall and rapid urbanisation major drivers behind Gaborone’s deadly floods
, Publisher: Centre for Environmental Policy -
ReportKew S, Pinto I, Philip S, et al., 2025,
Women and girls continue to bear disproportionate impacts of heatwaves in South Sudan that have become a constant threat
, Publisher: Centre for Environmental Policy
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