Nigel Arnell

• University of Reading

The UK has experienced recurring periods of hydrological droughts in the past, including the drought declared in summer 2022. Seasonal hindcasts, consisting of a large sample of plausible weather sequences, can be used to create drought storylines and add value to existing approaches to water resources planning. In this study, the drivers of winter...

The UK has experienced recurring periods of hydrological droughts in the past, including the latest drought declared in summer 2022. Seasonal hindcasts, consisting of a large sample of plausible weather sequences, can be used to add value to existing approaches to water resources planning. In this study, the drivers of winter rainfall in the Greate...

Spatially extensive multi-year hydrological droughts cause significant environmental stress. The UK is expected to remain vulnerable to future multi-year droughts under climate change. Existing approaches to quantify hydrological impacts of climate change often rely solely on global climate model (GCM) projections following different emission scena...

Much research has been carried out on the possible impacts of climate change for UK river flows. Catchment and national-scale studies since the early 1990s are here categorized into four modelling approaches: “top-down” GCM (Global Climate Model)-driven and probabilistic approaches and “bottom-up” stylised and scenario-neutral approaches. Early stu...

Policy, business, finance and civil society stakeholders are increasingly looking to compare future emissions pathways across both their associated physical climate risks stemming from increasing temperatures and their transition climate risks stemming from the shift to a low-carbon economy. Here, we present an integrated framework to explore near-...

The assessment of the impacts of climate change at different levels of global warming helps inform national and international policy discussion around mitigation targets. This paper provides consistent estimates of global and regional impacts and risks at increases in global mean temperature up to 5 °C above pre-industrial levels, for over 30 indic...

The AVOID2 programme provided evidence for UK Government on what might constitute dangerous climate change and the feasibility of avoiding it. The programme quantified some of the benefits of moving from a world that warms by around 4–5°C to one limiting global warming to below or well below 2°C. Whilst there is evidence that this transition is fea...

The aims of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) are to provide a framework for the intercomparison of global and regional-scale risk models within and across multiple sectors and to enable coordinated multi-sectoral assessments of different risks and their aggregated effects. The overarching goal is to use the knowledge...

This paper describes the motivation for the creation of the Vulnerability, Impacts, Adaptation and Climate Services (VIACS) Advisory Board for the Sixth Phase of the Coupled Model Intercomparison Project (CMIP6), its initial activities, and its plans to serve as a bridge between climate change applications experts and climate modelers. The climate...

This chapter reviews recent trends and variability in river flows to the North Sea. The main contributors are the River Elbe and the River Rhine. In addition to these large rivers many smaller rivers also discharge into the North Sea. However, by far the biggest contributor is the Baltic Sea outflow. Observation records for the major rivers drainin...

This paper introduces the special issue of Climatic Change on the QUEST-GSI project, a global-scale multi-sectoral assessment of the impacts of climate change. The project used multiple climate models to characterise plausible climate futures with consistent baseline climate and socio-economic data and consistent assumptions, together with a suite...

Water-related issues are the most prominent amongst the commonly identified impacts of climate change. In particular, water-related extremes, storms, floods and droughts, are the likely most immediate and damaging manifestations of a changing climate. This chapter outlines how research into climate change impacts developed at CEH, introduces the ke...

Environmental change poses risks to societies, including disrupting social and economic systems such as migration. At the same time, migration is an effective adaptation to environmental and other risks. We review novel science on interactions between migration, environmental risks and climate change. We highlight emergent findings, including how d...

This paper reviews the implications of climate change for the water environment and its management in England. There is a large literature, but most studies have looked at flow volumes or nutrients and none have considered explicitly the implications of climate change for the delivery of water management objectives. Studies have been undertaken in...

INTRODUCTION The Working Group II contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC WG II AR5, cf. Field et al. 2014) critically reviewed tens of thousands of recent publications to assess current scientific knowledge on climate change impacts, vulnerability and adaptation. Chapter 3 of the report fo...

The overall global-scale consequences of climate change are dependent on the distribution of impacts across regions, and there are multiple dimensions to these impacts. This paper presents a global assessment of the potential impacts of climate change across several sectors, using a harmonised set of impacts models forced by the same climate and Cl...

Despite significant progress in climate impact research, the narratives that science can presently piece together of a 2, 3, 4, or 5 °C warmer world remain fragmentary. Here we briefly review past undertakings to characterise comprehensively and quantify climate impacts based on multi-model approaches. We then report on the Inter-Sectoral Impact Mo...

This paper presents a preliminary assessment of the relative effects of rate of climate change (four Representative Concentration Pathways - RCPs), assumed future population (five Shared Socio-economic Pathways - SSPs), and pattern of climate change (19 CMIP5 climate models) on regional and global exposure to water resources stress and river floodi...

This paper presents an assessment of the effects of climate change on river flow regimes in representative English catchments, using the UKCP09 climate projections. These comprise a set of 10,000 coherent climate scenarios, used here (i) to evaluate the distribution of potential changes in hydrological behaviour and (ii) to construct relationships...

Despite significant progress in climate impacts research, the narratives that science can presently piece together of a 2, 3, 4, or 5 degree warmer world remain fragmentary. Here we briefly review past undertakings to comprehensively characterize and quantify climate impacts based on multi-model approaches. We then report on the Inter-Sectoral Impa...

Available at : Https://www.Isp.Ucar.edu/sites/default/files/Scenario_FrameworkPaper₁5aug11₁.Pdf

This paper presents an assessment of the implications of climate change for global river flood risk. It is based on the estimation of flood frequency relationships at a grid resolution of 0.5×0.5°, using a global hydrological model with climate scenarios derived from 21 climate models, together with projections of future population. Four indicators...

Water scarcity severely impairs food security and economic prosperity in many countries today. Expected future population changes will, in many countries as well as globally, increase the pressure on available water resources. On the supply side, renewable water resources will be affected by projected changes in precipitation patterns, temperature,...

This paper compares the effects of two indicative climate mitigation policies on river flows in six catchments in the UK with two scenarios representing un-mitigated emissions. It considers the consequences of uncertainty in both the pattern of catchment climate change as represented by different climate models and hydrological model parameterisati...

The scientific community is developing new global, regional, and sectoral scenarios to facilitate interdisciplinary research and assessment to explore the range of possible future climates and related physical changes that could pose risks to human and natural systems; how these changes could interact with social, economic, and environmental develo...

Although there is a strong policy interest in the impacts of climate change corresponding to different degrees of climate change, there is so far little consistent empirical evidence of the relationship between climate forcing and impact. This is because the vast majority of impact assessments use emissions-based scenarios with associated socio-eco...

Key Risks at the Global Scale Freshwater-related risks of climate change increase significantly with increasing greenhouse gas (GHG) concentrations (robust evidence, high agreement). {3.4, 3.5} Modeling studies since AR4, with large but better quantified uncertainties, have demonstrated clear differences between global futures with higher emissions...

Although there is a strong policy interest in the impacts of climate change corresponding to different degrees of climate change, there is so far little consistent empirical evidence of the relationship between climate forcing and impact. This is because the vast majority of impact assessments use emissions-based scenarios with associated socio-eco...

Significance Increasing concentrations of greenhouse gases in the atmosphere are widely expected to influence global climate over the coming century. The impact on drought is uncertain because of the complexity of the processes but can be estimated using outputs from an ensemble of global models (hydrological and climate models). Using an ensemble...

Climate change due to anthropogenic greenhouse gas emissions is expected to increase the frequency and intensity of precipitation events, which is likely to affect the probability of flooding into the future. In this paper we use river flow simulations from nine global hydrology and land surface models to explore uncertainties in the potential impa...

Future changes in runoff can have important implications for water resources and flooding. In this study, runoff projections from ISI-MIP (Inter-sectoral Impact Model Intercomparison Project) simulations forced with HadGEM2-ES bias-corrected climate data under the Representative Concentration Pathway 8.5 have been analysed for differences between i...

Quantitative simulations of the global-scale benefits of climate change mitigation are presented, using a harmonised, self-consistent approach based on a single set of climate change scenarios. The approach draws on a synthesis of output from both physically-based and economics-based models, and incorporates uncertainty analyses. Previous studies h...

This paper presents a global scale assessment of the impact of climate change on water scarcity. Patterns of climate change from 21 Global Climate Models (GCMs) under four SRES scenarios are applied to a global hydrological model to estimate water resources across 1339 watersheds. The Water Crowding Index (WCI) and the Water Stress Index (WSI) are...

We compare the characteristics of synthetic European droughts generated by the HiGEM1 coupled climate model run with present day atmospheric composition with observed drought events extracted from the CRU TS3 data set. The results demonstrate consistency in both the rate of drought occurrence and the spatiotemporal structure of the events. Estimate...

This paper presents an assessment of the impacts of climate change on a series of indicators of hydrological regimes across the global domain, using a global hydrological model run with climate scenarios constructed using pattern-scaling from 21 CMIP3 (Coupled Model Intercomparison Project Phase 3) climate models. Changes are compared with natural...

Water scarcity, in particular the dearth of renewable water resources for agricultural, industrial and domestic purposes, severely impairs food security and economic prosperity in many countries today. Ex- pected future population changes will, in most countries as well as globally, increase water scarcity through increased demand. On the supply si...

There is growing international concern at the rise in the severity of impact and frequency of extreme environmental events, potentially as a manifestation of global environmental change. There is a widely held belief that this trend could be linked with a future rise in the migration or displacement of human populations. However, recent approaches...

Projections of future changes in runoff can have important implications for water resources and flooding. In this study, runoff projections from ISI-MIP (Inter-sectoral Impact Model Intercomparison Project) simulations forced with HadGEM2-ES bias-corrected climate data under the Representative Concentration Pathway 8.5 have been analysed. Projectio...

This study presents the first global-scale multi-sectoral regional assessment of the magnitude and uncertainty in the impacts of climate change avoided by emissions policies. The analysis suggests that the most stringent emissions policy considered here—which gives a 50% chance of remaining below a 2 °C temperature rise target—reduces impacts by 20...

This paper has been accepted by PNAS as: "First look at changes in flood hazard in the Inter-Sectoral Impact Model Intercomparison Project ensemble."

This paper has been accepted by PNAS, as "Multimodel assessment of water scarcity under climate change.".

With this paper we draw conclusions from the contributions to this theme issue that all explored the links between environmental change, migration, and governance. We have three objectives. The first is to identify key themes emerging from each of the papers and to consider their significance. The second is to specify overarching implications of th...

We use a soil carbon (C) model (RothC), driven by a range of climate models for a range of climate scenarios to examine the impacts of future climate on global soil organic carbon (SOC) stocks. The results suggest an overall global increase in SOC stocks by 2100 under all scenarios, but with a different extent of increase among the climate model an...

Interest in the impacts of climate change is ever increasing. This is particularly true of the water sector where understanding potential changes in the occurrence of both floods and droughts is important for strategic planning. Climate variability has been shown to have a significant impact on UK climate and accounting for this in future climate c...

We use a soil carbon (C) model (RothC), driven by a range of climate models for a range of climate scenarios to examine the impacts of future climate on global soil organic carbon (SOC) stocks. The results suggest an overall global increase in SOC stocks by 2100 under all scenarios, but with a different extent of increase among the climate model an...

Executive Summary Extreme impacts can result from extreme weather and climate events, but can also occur without extreme events. This chapter examines two broad categories of impacts on human and ecological systems, both of which are influenced by changes in climate, vulnerability, and exposure: first, the chapter primarily focuses on impacts that...

In this paper, we propose a scenario framework that could provide a scenario "thread" through the different climate research communities (climate change - vulnerability, impact, and adaptation - and mitigation) in order to support assessment of mitigation and adaptation strategies and climate impacts. The scenario framework is organized around a ma...

The influence of the environment and environmental change is largely unrepresented in standard theories of migration, whilst recent debates on climate change and migration focus almost entirely on displacement and perceive migration to be a problem. Drawing on an increasing evidence base that has assessed elements of the influence of the environmen...

We present simulations of the impact of climate change on global water scarcity for five greenhouse gas emissions mitigation policy scenarios and compare them with a business-as-usual emissions scenario. A global water scarcity model is driven by climate change projections from 21 global climate models (GCMs). An aggressive policy scenario that giv...

The country reports were written by a range of climate researchers, chosen for their subject expertise, who were drawn from institutes across the UK. Authors from the Met Office and the University of Nottingham collated the contributions in to a coherent narrative which was then reviewed. The authors and contributors of the reports are as above.

The country reports were written by a range of climate researchers, chosen for their subject expertise, who were drawn from institutes across the UK. Authors from the Met Office and the University of Nottingham collated the contributions in to a coherent narrative which was then reviewed. The authors and contributors of the reports are as above.

Six land surface models and five global hydrological models participate in a model intercomparison project (WaterMIP), which for the first time compares simulation results of these different classes of models in a consistent way. In this paper the simulation setup is described and aspects of the multi-model global terrestrial water balance are pres...

This article presents a review of recent developments in studies assessing the global-scale impacts of climate change published since the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Literature covering six main impact sectors is reviewed: sea-level rise (SLR) and coastal impacts, ocean acidification, ecosystems...

A lack of buy-in by the United States arguably represents the greatest obstacle to tackling climate change. A major new report urges America to take action to cut emissions and begin adapting to climate change.

This article reviews some of the major lines of recent scientific progress relevant to the choice of global climate policy targets, focusing on changes in understanding since publication of the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4). Developments are highlighted in the following major climate system components...

Arnell, Nigel W., 2011. Incorporating Climate Change Into Water Resources Planning in England and Wales. Journal of the American Water Resources Association (JAWRA) 47(3):541-549. DOI: 10.1111/j.1752-1688.2011.00548.x Abstract: Public water supplies in England and Wales are provided by around 25 private-sector companies, regulated by an economic re...

{textlessptextgreatertextless}br/textgreaterThis paper assesses the implications of climate policy for exposure to water resources stresses. It compares a Reference scenario which leads to an increase in global mean temperature of 4 °C by the end of the 21st century with a Mitigation scenario which stabilises greenhouse gas concentrations at around...

Scenarios are used to explore the consequences of different adaptation and mitigation strategies under uncertainty. In this paper, two scenarios are used to explore developments with (1) no mitigation leading to an increase of global mean temperature of 4 °C by 2100 and (2) an ambitious mitigation strategy leading to 2 °C increase by 2100. For the...

Global hydrological models (GHMs) model the land surface hydrologic dynamics of continental-scale river basins. Here we describe one such GHM, the Macro-scale - Probability-Distributed Moisture model.09 (Mac-PDM.09). The model has undergone a number of revisions since it was last applied in the hydrological literature. This paper serves to provide...

This paper presents a preface to this Special Is-sue on the results of the QUEST-GSI (Global Scale Impacts) project on climate change impacts on catchment scale water resources. A detailed description of the unified methodology, subsequently used in all studies in this issue, is provided. The project method involved running simulations of catchment...

This paper assesses the relationship between amount of climate forcing - as indexed by global mean temperature change - and hydrological response in a sample of UK catchments. It constructs climate scenarios representing different changes in global mean temperature from an ensemble of 21 climate models assessed in the IPCC AR4. The results show a c...

Climate change is expected to produce reductions in water availability in England, potentially necessitating adaptive action by the water industry to maintain supplies. As part of Ofwat's fifth Periodic Review (PR09), water companies recently released their draft Water Resources Management Plans, setting out how each company intends to maintain the...

We present a comparative analysis of projected impacts of climate change on river runoff from two types of distributed hydrological model, a global hydrological model (GHM) and catchment-scale hydrological models (CHM). Analyses are conducted for six catchments that are global in coverage and feature strong contrasts in spatial scale as well as cli...

Scenarios are used to explore the consequences of different adaptation and mitigation strategies under uncertainty. In this paper, two scenarios are used to explore developments with (1) no mitigation leading to an increase of global mean temperature of 4 degrees C by 2100 and (2) an ambitious mitigation strategy leading to 2 degrees C increase by...

http://www.metoffice.gov.uk/climate-change/policy-relevant/obs-projections-impacts

This paper provides a framework for the theme issue by exploring links between environmental change and human migration. We review evidence that demonstrates that millions of people have moved or are likely to move towards and not away from environmental risk and hazard by moving from rural areas to rapidly growing urban areas. Moreover, some peopl...

This paper assesses the relationship between amount of climate forcing – as indexed by global mean temperature change – and hydrological response in a sample of UK catchments. It constructs climate scenarios representing different changes in global mean temperature from an ensemble of 21 climate models assessed in the IPCC AR4. The results show a c...

This paper investigates whether and to what extent a wide range of actors in the UK are adapting to climate change, and whether this is evidence of a social transition. We document evidence of over 300 examples of early adopters of adaptation practice to climate change in the UK. These examples span a range of activities from small adjustments (or...

This paper presents an overview of the methods and results of an assessment of climate change impacts on catchment scale water resources, conducted under the QUEST-GSI (Global Scale Impacts) programme. The project method involved running simulations of catchment-scale hydrology using a unified set of past and future climate scenarios, to enable a c...

Uncertainties associated with the representation of various physical processes in global climate models (GCMs) mean that, when projections from GCMs are used in climate change impact studies, the uncertainty propagates through to the impact estimates. A complete treatment of this 'climate model structural uncertainty' is necessary so that decision-...

We present a comparative analysis of projected impacts of climate change on river runoff from two types of distributed hydrological model, a global hydrological model (GHM) and catchment-scale hydrological models (CHM). Analyses are conducted for six catchments that are global in coverage and feature strong contrasts in spatial scale as well as cli...

Since its launch in 1977, the scientific issues addressed by papers published in Climatic Change have changed considerably. Nuclear winter came and went, and papers have come from an increasingly diverse range of disciplines. Most obvious, of course, has been the emergence to overwhelming dominance of papers concerned with the processes and consequ...

Understanding the impacts of climate change is crucial for adaptation and mitigation policy decisions. This is particularly true for the water sector and flood risk as they have a direct link with climate, and climate change might result in a potentially changed risk to society. Increasingly water managers request probabilistic projections of clima...

Predictions of future climate encompass uncertainties, either due to the specific model implementation or due to the use of different models. In this study we assess the response at the global scale of soil organic carbon (SOC) stocks to the variability of climate inputs derived from global circulation models (GCM). A consistent global data set at...

21st century climate change is projected to result in an intensification of the global hydrological cycle, but there is substantial uncertainty in how this will impact freshwater availability. A relatively overlooked aspect of this uncertainty pertains to how different methods of estimating potential evapotranspiration (PET) respond to changing cli...

IntroductionClimate Change and Hydrological ProcessesEstimating the Impacts of Climate Change in a Particular CatchmentConclusions: Coping with Climate ChangeAcknowledgementsReferences