Medium Emissions Scenario Research Articles

Impacts on cooling energy consumption due to the UHI and vegetation changes in Manchester, UK

Climate change projections estimate a rise of approximately 3°C by the 2080s for most of the UK (medium emissions scenario at 50% probability level, 1961–1990 baseline). Warming is a particular concern for urban areas due to urban densification and the Urban Heat Island (UHI) effect.To counteract the UHI, one adaptation strategy for urban areas is increasing the proportion of greenspace, such as parks, street tree plantings, and green roofs. This research employed an interdisciplinary approach to measure and model fine-scale microclimate changes due to greenspace and explore the implications for building energy demand in Manchester, UK. Both the modelled and measured microclimate data informed development of a series of weather files for building energy modelling of three commercial building types.For a scenario adding 5% mature trees to the urban case study, the combination of microclimate modelling and data analysis estimated a maximum hourly air temperature reduction of nearly 1.0°C under peak UHI conditions and wind speed reductions up to 1.0m/s. These results were used to change the weather files in the building energy modelling, which estimated a reduction of 2.7% in July chiller energy due to the combination of reduced UHI peak hours and eight additional trees shading a three-storey shallow plan building. Energy savings increased to 4.8% under a three-day period of peak UHI conditions.

Impacts of climate change on marginal nights for road salting

Spreading salt on roads costs UK highways authorities millions of pounds each year. As temperatures rise under climate change, the number of nights with freezing temperatures are projected to fall, potentially reducing salting costs. However, this may also mean more nights drop close to freezing, rather than falling comfortably below zero. These ‘marginal nights’ often require a judgement call as to whether salting is required. The analysis presented here considers how climate change is projected to affect the number of marginal nights at nine locations in England in the near-term (2020s). Synthetic temperature timeseries from the UK Climate Projections 2009 weather generator are used to calculate frequencies of marginal nights in the current and potential future climate. The results show a reduction in the average number of marginal nights for all locations under the median estimate of the medium emissions scenario. The full range of results shows that, despite the reduction, marginal nights will still occur, and in some years the frequency will exceed the baseline. This serves as a reminder that, even under a warmer climate, there will be cold periods that require roads to be salted.

Attribution of mortality to the urban heat island during heatwaves in the West Midlands, UK.

BackgroundThe Urban Heat Island (UHI) effect describes the phenomenon whereby cities are generally warmer than surrounding rural areas. Traditionally, temperature monitoring sites are placed outside of city centres, which means that point measurements do not always reflect the true air temperature of urban centres, and estimates of health impacts based on such data may under-estimate the impact of heat on public health. Climate change is likely to exacerbate heatwaves in future, but because climate projections do not usually include the UHI, health impacts may be further underestimated. These factors motivate a two-dimensional analysis of population weighted temperature across an urban area, for heat related health impact assessments, since populations are typically densest in urban centres, where ambient temperatures are highest and the UHI is most pronounced. We investigate the sensitivity of health impact estimates to the use of population weighting and the inclusion of urban temperatures in exposure data.MethodsWe quantify the attribution of the UHI to heat related mortality in the West Midlands during the heatwave of August 2003 by comparing health impacts based on two modelled temperature simulations. The first simulation is based on detailed urban land use information and captures the extent of the UHI, whereas in the second simulation, urban land surfaces have been replaced by rural types.Results and conclusionsThe results suggest that the UHI contributed around 50 % of the total heat-related mortality during the 2003 heatwave in the West Midlands. We also find that taking a geographical, rather than population-weighted, mean of temperature across the regions under-estimates the population exposure to temperatures by around 1 °C, roughly equivalent to a 20 % underestimation in mortality. We compare the mortality contribution of the UHI to impacts expected from a range of projected temperatures based on the UKCP09 Climate Projections. For a medium emissions scenario, a typical heatwave in 2080 could be responsible for an increase in mortality of around 3 times the rate in 2003 (278 vs. 90 deaths) when including changes in population, population weighting and the UHI effect in the West Midlands, and assuming no change in population adaptation to heat in future.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-016-0100-9) contains supplementary material, which is available to authorized users.

Climate change and N2O emissions from South West England grasslands: A modelling approach

Unravelling the impacts of climate change on agriculture becomes increasingly important, as the rates and magnitude of its effects are accelerating. Current estimates of the consequences of climate change on nitrous oxide (N2O) emissions remain largely uncertain; there is a need for more consistent and comprehensive assessments of this impact. In this study we explored the implications of two IPCC climate change projections (high and medium emissions scenarios) on N2O emissions from South West England grasslands for the time slices of a baseline, the 2020s, the 2050s and the 2080s, employing a process-based model (SPACSYS). The model was initially calibrated and validated using datasets collected from three grassland sites of the region. Statistical analysis showed that simulated results had no significant total error or bias compared to measured values. We found a consistent increase in N2O emissions of up to 94% under future climate change scenarios compared to those under the baseline, and warming rather than precipitation variability was the overriding factor controlling the N2O rise. Modelling fertilizer forms showed that replacing ammonium-nitrate fertilizers with urea or slurry significantly reduced N2O emissions (c. 30%). Our study highlights the urgent necessity to adopt viable N2O mitigation measures now in order to avoid higher emissions in the future.

Potential future fisheries yields in shelf waters: a model study of the effects of climate change and ocean acidification

Abstract. We applied a coupled marine water column model to three sites in the North Sea. The three sites represent different hydrodynamic regimes and are thus representative of a wider area. The model consists of a hydro-biogeochemical model (GOTM-ERSEM-BFM) coupled one way upwards to a size-structured model representing pelagic predators and detritivores (Blanchard et al., 2009). Thus, bottom-up pressures like changing abiotic environment (climate change, chemical cycling) will have an impact on fish biomass across the size spectrum. Here, we studied three different impacts of future conditions on fish yield: climatic impacts (medium emission scenario), abiotic ocean acidification impacts (reduced pelagic nitrification), and biotic ocean acidification impacts (reduced detritivore growth rate). The three impacts were studied separately and combined, and results showed that sites within different hydrodynamic regimes can respond very differently. The seasonally stratified site showed an increase in fish yields (occurring in winter and spring), with acidification effects of the same order of magnitude as climatic effects. The permanently mixed site also showed an increase in fish yield (increase in summer, decrease in winter), due to climatic effects moderated by acidification impacts. The third site, which is characterised by large inter-annual variability in thermal stratification duration, showed a decline in fish yields (occurring in winter) due to decline in the benthic system which forms an important carbon pathway at this site. All sites displayed a shift towards a more pelagic-oriented system.

Model-Based Assessment of Climate Change Impact on Isaac River Catchment, Queensland

Isaac River catchment, which is located within Fitzroy basin in Central Queensland, Australia is mostly a semi-arid region, sparsely populated, but rife with economic activities such as mining, grazing, cropping and production forestry. Hydro-meteorological data over the past several decades reveal that the catchment is experiencing increasing variability in precipitation and streamflow contributing to more severe droughts and floods supposedly due to climate change. The exposure of the economic activities in the catchment to the vagaries of nature and the possible impacts of climate change on the stream flow regime are to be analyzed. For the purpose, SWAT model was adopted to capture the dynamics of the catchment. During calibration of the model 12 parameters were found to be significant which yielded a R2 value of 0.73 for calibration and 0.66 for validation. In the next stage, six GCMs from CMIP3 namely, CGCM3.1/T47, CNRM-CM3, GFDL-CM2.1, IPSLCM4, MIROC3.2 (medres) and MRI CGCM2.3.2 were selected for climate change projections in the Fitzroy basin under a very high emissions scenario (A2), a medium emissions scenario (A1B) and a low emissions scenario (B1) for two future periods (2046-2064) and (2080-2100). All GCMs showed consistent increases in temperature, and as expected, highest rate for A2 and lowest rate for B1. Precipitation predictions were mixed-reductions in A2 and increases in A1B and B1, and more variations in distant future compared to near future. When the projected temperatures and precipitation were inputted into the SWAT model, and the model outputs were compared with the baseline period (1980-2010), the picture that emerged depicted worsening water resources variability.

Sustainable grassland systems: a modelling perspective based on the North Wyke Farm Platform.

SummaryThe North Wyke Farm Platform (NWFP) provides data from the field‐ to the farm‐scale, enabling the research community to address key issues in sustainable agriculture better and to test models that are capable of simulating soil, plant and animal processes involved in the systems. The tested models can then be used to simulate how agro‐ecosystems will respond to changes in the environment and management. In this study, we used baseline datasets generated from the NWFP to validate the Soil‐Plant‐Atmosphere Continuum System (SPACSYS) model in relation to the dynamics of soil water content, water loss from runoff and forage biomass removal. The validated model, together with future climate scenarios for the 2020s, 2050s and 2080s (from the International Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES): medium (A1B) and large (A1F1) emission scenarios), were used to simulate the long‐term responses of the system with three contrasting treatments on the NWFP. Simulation results demonstrated that the SPACSYS model could estimate reliably the dynamics of soil water content, water loss from runoff and drainage, and cut biomass for a permanent sward. The treatments responded in different ways under the climate change scenarios. More carbon (C) is fixed and respired by the swards treated with an increased use of legumes, whereas less C was lost through soil respiration with the planned reseeding. The deep‐rooting grass in the reseeding treatment reduced N losses through leaching, runoff and gaseous emissions, and water loss from runoff compared with the other two treatments.

Prediction of groundwater‐induced flooding in a chalk aquifer for future climate change scenarios

AbstractCurrent climate change models for the southeast UK predict changing rainfall patterns, with increased incidence of extreme events. The chalk aquifer in the UK and northern France is susceptible to groundwater‐induced flooding under such conditions. In this methodological study we apply a frequency domain analysis approach to the chalk aquifer to derive a transfer function between effective rainfall and groundwater level from 7 years of monitoring data from the North Heath Barn site, near Brighton. The derived transfer function was calibrated and validated against monitoring data and then used to predict groundwater level for rainfall models for high, medium and low emission scenarios from the UKCP09 database. The derived transfer function is most closely comparable to the linear aquifer model, despite evidence for both matrix and fracture or karst water flow in the chalk, with transmissivity and unconfined storativity at the catchment scale of 1548 m2 day−1and 1.6 × 10−2. The application of the transfer function to UKCP09 rainfall data suggests that groundwater‐induced flooding may be about four times more frequent by 2040–2069 compared with 1961–1990 and seven times more frequent by 2070–2099. The model data also suggest an increase in the duration of groundwater minima relative to the reference period. Compared to deterministic modelling which requires detailed knowledge of aquifer heterogeneity and processes, the transfer function approach, although with limitations, is simpler, incorporating these factors into the analysis through frequency and phase coefficients, and thus may have the potential for groundwater risk assessment in other areas. Copyright © 2015 John Wiley & Sons, Ltd.

Modelling the combined impacts of climate change and direct anthropogenic drivers on the ecosystem of the northwest European continental shelf

The potential response of the marine ecosystem of the northwest European continental shelf to climate change under a medium emissions scenario (SRES A1B) is investigated using the coupled hydrodynamics-ecosystem model POLCOMS-ERSEM. Changes in the near future (2030–2040) and the far future (2082–2099) are compared to the recent past (1983–2000). The sensitivity of the ecosystem to potential changes in multiple anthropogenic drivers (river nutrient loads and benthic trawling) in the near future is compared to the impact of changes in climate. With the exception of the biomass of benthic organisms, the influence of the anthropogenic drivers only exceeds the impact of climate change in coastal regions. Increasing river nitrogen loads has a limited impact on the ecosystem whilst reducing river nitrogen and phosphate concentrations affects net primary production (netPP) and phytoplankton and zooplankton biomass. Direct anthropogenic forcing is seen to mitigate/amplify the effects of climate change. Increasing river nitrogen has the potential to amplify the effects of climate change at the coast by increasing netPP. Reducing river nitrogen and phosphate mitigates the effects of climate change for netPP and the biomass of small phytoplankton and large zooplankton species but amplifies changes in the biomass of large phytoplankton and small zooplankton.

Will the Bagmati Basin’s Future Hydrological Change be linked with Global Climate Change Patterns?

The impact of climate change on society is one of the most serious challenges of this century. Observations have shown that the Earth’s hydrologic cycle has intensified during past century as the Earth’s temperatures have increased. Such change in hydrology will affect nearly every aspect of human well being, from agricultural productivity and energy use to flood control as well as municipal and industrial water supply. This study therefore, focuses on using climate projection data (precipitation and temperature) from an ensemble of 16 Global Climate Models (GCMs) and Thornthwaite Monthly Water Balance Model (TMWB) to assess changes in the basin hydrology in a high altitude mountainous Bagmati basin of Nepal. This region is considered as one of the most disaster (landslides and flood) prone basins in Hind-Kush-Himalaya due to the summer monsoon. The assessments were conducted for short (2020-2029), medium (2060-2069) and long (20902099) terms relative to the base period of the 1990-1999 in high (A2), medium (A1B) and low (B1) emission scenarios. According to GCMs the basin is expected to witness higher temperatures from about 2oC (B1) to 4.5oC (A2) and receive higher precipitation from about 7% (B1) to 20% (A2) in 2099. The increased precipitation is primarily expected to occur during the monsoon season, suggesting a wetter monsoon. The results from TMWB modeling show generation of higher runoff,

Spatial time-dependent reliability analysis of corrosion damage to RC structures with climate change

The environment around concrete structures may be influenced by a changing climate, especially in the long run, leading to an acceleration of deterioration. Therefore, the safety, serviceability and durability of concrete infrastructure may decline at a faster rate than expected. Carbonation-induced deterioration to concrete structures constructed in Sydney, Australia and Kunming, China under a changing climate is investigated in this paper. Two emissions scenarios are considered – RCP 8.5 and RCP 4.5, representing high and medium greenhouse gas emissions scenarios respectively. The spatial time-dependent reliability analysis includes time-dependent climate scenarios and deterioration processes, as well as a large number of random variables and spatial random fields of material properties and dimensions. The surface of concrete structures is discretised into a large number of elements and the likelihood and extent of corrosion damage is calculated by tracking the evolution of the corrosion process of each element using Monte Carlo simulations. The results show that a changing climate could cause the extent of damage to increase by up to 6% for reinforced concrete infrastructure in Kunming. The findings may be used to assess climate adaptation measures in the design stage, as well as a cost–benefit analysis of climate adaptation measures.

Application of LARS - WG downscaling model for building climate change scenarios in the Srepok watershed

There are statistical downscaling methods such as: SDSM, LARS-WG, WGEN…, used to convert information on climate variables from the simulation results of General Circulation Model (GCM) to build climate change scenarios for local region. In this study, we used the LARS-WG model and HadCM3 GCM for two emission scenarios: B1 (low emission scenario) and A1B (medium emission scenario) to generate future scenarios for temperature and precipitation at meteorological stations and rain gauges in the Srepok watershed. The LARS-WG model was calibrated and validated against observed climate data for the period 1980-2009, and the calibrated LARS-WG was then used to generate future climate variables for the 2020s (2011-2030), 2055s (2046-2065), and 2090s (2080-2099). The climate change scenarios suggested that the climate in the study area will become warmer and drier in the future. The results obtained in this study could be useful for policy makers in planning climate change adaptation strategies for the study area.

The relative importance of input weather data for indoor overheating risk assessment in dwellings

The risk of overheating in UK dwellings is predicted to increase due to anthropogenic climate change and local urban climate modification leading to an increased urban heat island effect. Dwelling geometry characteristics such as orientation, aspect, and glazing, and building fabric characteristics such as thermal mass and resistance can influence the risk of overheating. The majority of simulation-based studies have focused on identifying the importance of building characteristics on overheating risk using a small number of weather files, or focus solely on the impact of external temperatures rather than a full set of climatic variables. This study examines the overheating risk in London dwelling archetypes when simulated under different UK climates, both in the present and under ‘hot future’ conditions, with the objective of identifying whether the conclusions drawn from location-specific studies can be generically applied to different cities. Simulations were carried out using the dynamic thermal simulation tool EnergyPlus using 3456 dwelling variants and six different Design Summer Year (DSY) climate files from locations within the UK. In addition, a 2050 Medium Emissions scenario weather file was used to model a particularly hot summer in all locations. The results indicate that weather files can influence the ranking of relative overheating risk between dwelling types, with significant variations in the relative ranking between London, Scotland and the North of England, and the rest of England. These results show that studies examining the overheating risk across the UK need to consider the variability of building performance under regional weather conditions.

The technical potential of Great Britain to produce ligno‐cellulosic biomass for bioenergy in current and future climates

AbstractProcess and empirical‐based models that describe lignocellulosic biomass yield of the perennial energy grass Miscanthus (MiscanFor©), short rotation coppice (SRC) trees and shrubs, poplar and willow (ForestGrowth‐SRC) and a number of short rotation forest trees (ESC‐CARBINE), were used to estimate the yield potential for current and future climates across Great Britain (GB). In current climates, modelled yields for all feedstock crops varied between 8.1 and 10.6 Mg dry weight (DW) ha−1 yr−1 with willow SRC and poplar SRF producing the lowest and highest yields respectively. For the medium emissions scenario (UKCP09) in 2050, mean yield for all feedstock crops varied between 7.6 and 12.7 Mg DW ha−1 yr−1 with willow SRC and poplar SRF once again the lowest and the highest recorded yields. There were clear geographical trends within GB. Miscanthus yield was higher than all others in the south‐west (13.1 Mg DW ha−1 yr−1), SRC willow and SRC poplar in the north‐west (12.1–15.8 Mg DW ha−1 yr−1) and in the midlands and south‐east, SRF poplar was the highest yielding (10.5–11.6 Mg DW ha−1 yr−1). These geographical trends changed little with climate out to 2050, with mean yield of each ‘best feedstock’ increasing from 12.7 to 14.2 Mg DW ha−1 yr−1. Out to 2050, SRC declined slightly and Miscanthus and SRF poplar increased as the ‘best feedstock’ option. Except for a few localized examples, only SRF poplar had a higher yield than SRC or Miscanthus. These data suggest that in current and future climates, lignocellulosic biomass plantation species can be selected and optimized for best yield performance in different regions of GB. This modelling framework provides a valuable starting‐point for which to test the performance of new genetic material, as this becomes available and parameterized for the models and socio‐economic scenarios that may impact on the bioenergy industry.

High estimates of supply constrained emissions scenarios for long-term climate risk assessment

The simulated effects of anthropogenic global warming have become important in many fields and most models agree that significant impacts are becoming unavoidable in the face of slow action. Improvements to model accuracy rely primarily on the refinement of parameter sensitivities and on plausible future carbon emissions trajectories. Carbon emissions are the leading cause of global warming, yet current considerations of future emissions do not consider structural limits to fossil fuel supply, invoking a wide range of uncertainty. Moreover, outdated assumptions regarding the future abundance of fossil energy could contribute to misleading projections of both economic growth and climate change vulnerability. Here we present an easily replicable mathematical model that considers fundamental supply-side constraints and demonstrate its use in a stochastic analysis to produce a theoretical upper limit to future emissions. The results show a significant reduction in prior uncertainty around projected long term emissions, and even assuming high estimates of all fossil fuel resources and high growth of unconventional production, cumulative emissions tend to align to the current medium emissions scenarios in the second half of this century. This significant finding provides much-needed guidance on developing relevant emissions scenarios for long term climate change impact studies.

Modelling marine ecosystem response to climate change and trawling in the North Sea

The marine ecosystem response to climate change and demersal trawling was investigated using the coupled hydrodynamic-biogeochemical water column model GOTM-ERSEM-BFM for three contrasting sites in the North Sea. Climate change forcing was derived from the HadRM3-PPE-UK regional climate model for the UK for the period 1950–2100 using historical emissions and a medium emissions scenario (SRESA1B). Effects of demersal trawling were implemented as an additional mortality on benthic fauna, and changes in the benthic–pelagic nutrient and carbon fluxes. The main impacts of climate change were (i) a temperature-driven increase in pelagic metabolic rates and nutrient cycling, (ii) an increase in primary production fuelled by recycled nutrients, (iii) a decrease in benthic biomass due to increased benthic metabolic rates and decreased food supply as a result of the increased pelagic cycling, and (iv) a decrease in near-bed oxygen concentrations. The main impacts of trawling were (i) reduced benthic biomass due to the increased mortality, and (ii) the increased benthic–pelagic nutrient fluxes, with these effects counteracting each other, and relatively small changes in other variables. One important consequence was a large decrease in the de-nitrification flux predicted at the two summer-stratified sites because less benthic nitrate was available. The effects of trawling scaled linearly with fishing effort, with greatest sensitivity to fishing in summer compared to fishing in winter. The impacts of climate change and trawling were additive, suggesting little or no non-linear interactions between these disturbances.

Silvicultural strategies for adapting planted forests to climate change: from theory to practice

Adapting forests to climate change involves silvicultural measures such as use of a range of species and the fostering of mixed stands. We tested these in a Sitka spruce forest in southern Scotland, employing the Ecological Site Classification to match suitability of 24 species to six climatic and edaphic variables under values of accumulated temperature and moisture deficit projected for a medium emissions scenario for the present century. Both median and 90<sup>th</sup> percentile values were contrasted. In the first case there was a small change in species suitability with Sitka spruce, noble fir, downy birch, sycamore and aspen being the most suitable species. When the 90<sup>th</sup> percentile values were employed, the suitability of Sitka spruce and similar conifers had declined by the 2050’s due to soil moisture deficits. The actual performance of a range of species in a long-term experiment on a similar, warmer site showed several productive conifers including Sitka spruce that maintained reasonable growth when planted in mixture. Mixed plots were developing into pure stands of the most productive species. Species diversification was the most practical adaptation measure for this forest and should concentrate on areas of the greatest risk like south-facing slopes with free-draining soils.  

Vulnerability of timber in ground contact to fungal decay under climate change

Attack of decay fungi on wood-based material depends primarily on the natural durability of wood, the local climatic conditions, and the likely climatic change. This study investigates the vulnerability of wood and structural timber in ground contact to decay fungi under high and medium emissions scenarios specified by the Intergovernmental Panel on Climate Change, and a future scenario in which the global emissions have been limited to 550 ppm through a range of successful intervention schemes. Nine general circulation models are applied to project the local climates of Brisbane, Sydney, and Melbourne in Australia. It was found that, under the three emissions scenarios, the median decay rate of wood by 2080, relative to that in 2010, could increase up to 10 % in Brisbane and Sydney, but could decrease by 12 % in Melbourne. For timber of less durable wood species 50 years after installation, the residual strength under climate change could be almost 25 % less than that without climate change. The coefficients of variation (COVs) of decay rate of wood are in the vicinity of 1.0 regardless of wood species. For residual strength of timber pole after 50 years of installation, the COVs range from 0.2 to 1.1, depending on the natural durability of timber and the site location. The high COVs due to the variability of natural durability of wood and of climate change, in combination with the likely changes in median residual strength of structural elements, will cause significant structural reliability issues of wood construction and need to be addressed in engineering design codes.

Simulating urban heat island effects with climate change on a Manchester house

This article presents a methodology for determining the internal temperatures of a post-1919 mid-terrace house for the present-day and a future (2050) climate. The Meteorological Office, Hadley Centre regional climate model has been run with urban parameterisation and an improved land-surface scheme with urban heat island forcing and a weather generator to quantify the effect of the urban heat island. Manchester city dry-bulb air temperatures are shown to be of the order of 4 K higher than those for the present-day under a UKCP09 medium emissions scenario. Extreme summer temperature data (99% percentile) are used to produce a cooling design day for use in a building simulation program.1 Loft and wall insulation decreases internal air temperatures by up to 17% and low e glazing with louvres by up to 8%. Internal temperatures for a 2050 climate will exceed existing Chartered Institution of Building Services Engineers thresholds. Practical application: Climate change is an important subject for both the building industry and local authorities. Climate change scenarios produced by the Hadley Centre General Circulation Models (GCM) have been downscaled to the local level for use in a building simulation model.1 This article demonstrates a technique that enables data from a GCM to be used within a building simulation program1 for an urban environment. It also examines the implications of the combined effect of the urban heat island and climate change on the adaptation options available to designers and planners for existing and future buildings.

Modelling the impacts of climate change on upland catchments in southwest Scotland using MIKE SHE and the UKCP09 probabilistic projections

Hydrological models of three upland sub-catchments of Loch Dee, southwest Scotland, are calibrated and validated against observed discharge. Perturbed precipitation and potential evapotranspiration (PET) are generated from UKCIP09 projections for Low, Medium and High emissions scenarios for the 2050s and 2080s for probability levels between 10 and 90%. Annual and monthly PET increases for all scenarios. Central estimates of increases in annual PET are up to 10.7 (2050s) and 15.8% (2080s). Precipitation becomes more seasonal, increasing in winter and decreasing in summer for all but the extreme probability levels. Annual precipitation declines for the lowest (up to 30%) probability levels and increases thereafter (up to 5.8% for the 2050s and 10.3% for the 2080s at the 50% level). Changes in discharge are driven by those for precipitation. Although there is uncertainty in changes in annual discharge, most scenarios increase winter discharges (2050s: up to 24.2%; 2080s: up to 50.9% at the 50% level) and reduce summer flows (2050s: up to 34.2%, 2080s: up to 48.7% at the 50% level). Potential impacts include enhanced winter flooding and lower summer reservoir levels with implications for hydropower. Greater seasonality in discharge may impact fisheries and ongoing recovery from surface water acidification.