Search

This global spatially explicit (0.5 by 0.5 degree) analysis presents the nitrogen (N) and phosphorus (P) inputs, processing and biogeochemical retention and delivery to surface waters and river export to coastal seas according to the five shared socioeconomic pathways (SSP). Four systems are considered: (i) human system; (ii) agriculture; (iii) aquaculture; (iv) nature. Exploring the changes during 1980–2015 and 2015–2050 according to the SSPs shows that the natural nutrient sources have been declining in the past decades and will continue to decline in all SSPs in future decades due to massive land transformations, while agriculture, human sewage and aquaculture are becoming increasingly dominant (globally up to 80% of nutrient delivery). More efforts than those employed in any of the SSPs are needed to slow down the global nutrient cycles. One of the drivers of the proliferation of harmful algal blooms is the tendency towards increasing N:P ratios in global freshwaters and export to the global coastal seas; this is the result of increasing N:P in inputs in food production, more efficient biogeochemical retention of P than of N in river basins, and groundwater N legacies, which seems to be most pronounced in a united world that strives after sustainability. The diverging strategies to achieve UN Sustainable Development Goals 14 (life below water), 2 (zero hunger) and 6 (clean water and sanitation) therefore require a balanced management system for both N and P in all systems, that accounts for future nutrient legacies.

Limiting warming to well below 2°C requires rapid and complete decarbonisation of energy systems. We compare economy-wide modelling of 1.5°C and 2°C scenarios with sector-focused analyses of four critical sectors that are difficult to decarbonise: aviation, shipping, road freight transport, and industry. We develop and apply a novel framework to analyse and track mitigation progress in these sectors. We find that emission reductions in the 1.5°C and 2°C scenarios of the IMAGE model come from deep cuts in CO2 intensities and lower energy intensities, with minimal demand reductions in these sectors’ activity. We identify a range of additional measures and policy levers that are not explicitly captured in modelled scenarios but could contribute significant emission reductions. These are demand reduction options, and include less air travel (aviation), reduced transportation of fossil fuels (shipping), more locally produced goods combined with high load factors (road freight), and a shift to a circular economy (industry). We discuss the challenges of reducing demand both for economy-wide modelling and for policy. Based on our sectoral analysis framework, we suggest modelling improvements and policy recommendations, calling on the relevant UN agencies to start tracking mitigation progress through monitoring key elements of the framework (CO2 intensity, energy efficiency, and demand for sectoral activity, as well as the underlying drivers), as a matter of urgency. Key policy insightsFour critical sectors (aviation, shipping, road freight, and industry) cannot cut their CO2 emissions to zero rapidly with technological supply-side options alone. Without large-scale negative emissions, significant demand reductions for those sectors’ activities are needed to meet the 1.5–2°C goal.Policy priorities include affordable alternatives to frequent air travel; smooth connectivity between low-carbon travel modes; speed reductions in shipping and reduced demand for transporting fossil fuels; distributed manufacturing and local storage; and tightening standards for material use and product longevity.The COVID-19 crisis presents a unique opportunity to enact lasting CO2 emissions reductions, through switching from frequent air travel to other transport modes and online interactions.Policies driving significant demand reductions for the critical sectors’ activities would reduce reliance on carbon removal technologies that are unavailable at scale. Four critical sectors (aviation, shipping, road freight, and industry) cannot cut their CO2 emissions to zero rapidly with technological supply-side options alone. Without large-scale negative emissions, significant demand reductions for those sectors’ activities are needed to meet the 1.5–2°C goal. Policy priorities include affordable alternatives to frequent air travel; smooth connectivity between low-carbon travel modes; speed reductions in shipping and reduced demand for transporting fossil fuels; distributed manufacturing and local storage; and tightening standards for material use and product longevity. The COVID-19 crisis presents a unique opportunity to enact lasting CO2 emissions reductions, through switching from frequent air travel to other transport modes and online interactions. Policies driving significant demand reductions for the critical sectors’ activities would reduce reliance on carbon removal technologies that are unavailable at scale.

Bioenergy is the EU's leading renewable energy source at present. Understanding bioenergy's contribution to the future EU energy mix is strategically relevant for mid to long term climate targets. This review consolidates recent projections of both supply and demand dynamics for EU bioenergy to 2050, drawing from resource-focused, demand-driven and integrated assessment approaches. Projections are synthesised to identify absolute ranges, determine cohesion with policy and draw insights on the implications for the scale of development, trade and energy security. Supply side studies have undergone methodological harmonisation efforts in recent years. Despite this, due to assumptions on key uncertainties such as feedstock yields, technical potential estimates range from 9 to 25 EJyr-1 of EU domestically available biomass for energy in 2050. Demand side projections range between 5 and 19 EJyr-1 by 2050. This range is primarily due to variations in study assumptions on key influential developments such as economic competitivity of bioenergy, EU energy efficiency gains within the power sector, flexibility for meeting mitigation targets and technological portfolios. Upper bound technical supply estimates are able meet future demand wholly from the domestic resource base, holding the potential to reduce total EU primary energy import dependency 22% points from the current EU roadmap trajectory. However, due to part of this domestic resource base being deemed economically inaccessible or of insufficient quality, interregional imports are projected to increase from current 4% to 13–76%. Emergence of non-energy applications are projected to compete for at least 10% of the biomass needed to fulfil bioenergy demand in 2050.

Limiting climate change below a given temperature will require fundamental changes in the current energy system, both in the energy supply and the energy demand sectors. Previous global model-based analyses, however, have focused mostly on energy supply transformations. Therefore, in this study we respond to this knowledge gap by analysing the future energy demand projections in both baseline and climate policy scenarios of global models in detail. We examine the projections for the industry, transport and buildings sectors across four models and three different reference scenarios from the Shared-Socioeconomic Pathway framework by applying a decomposition analysis. We compare the projected demand side mitigation efforts to a more detailed, sector-specific, technology-oriented assessment of demand-side abatement potential for the year 2030. Without climate policy, model-based projections show that baseline emissions can grow rapidly in industry and transport sectors, but are also highly uncertain across models. The decomposition analysis shows that the key uncertainty across the global scenarios is the projected final energy per capita. For modellers therefore there lies a challenge to better understand drivers of future energy efficiency and service demand, that contribute to the projected energy demand. This model enhancement would moreover allow to evaluate policy measures that can impact this relation. The technology assessment estimates that in particular in the transport and buildings sector there is a higher potential to reduce demand-side emissions through energy efficiency improvements than implemented in the scenarios. Improved insulation, higher electric vehicle penetration rates and modal shift for example could reduce final energy demand to lower levels in the short term than currently projected, reducing the dependency on fuel switching required in current scenarios to meet the stringent climate targets.

International audience; The influence of climate change on mid-latitudes atmospheric circulation is still very uncertain. The large internal variability makes it difficult to extract any statistically significant signal regarding the evolution of the circulation. Here we propose a methodology to calculate dynamical trends tailored to the circulation of specific days by computing the evolution of the distances between the circulation of the day of interest and the other days of the time series. We compute these dynamical trends for two case studies of the hottest days recorded in two different European regions (corresponding to the heat-waves of summer 2003 and 2010). We use the NCEP reanalysis dataset, an ensemble of CMIP5 models, and a large ensemble of a single model (CESM), in order to account for different sources of uncertainty. While we find a positive trend for most models for 2003, we cannot conclude for 2010 since the models disagree on the trend estimates.

The possibilities and need for adaptation and mitigation depends on uncertain future developments with respect to socio-economic factors and the climate system. Scenarios are used to explore the impacts of different strategies under uncertainty. In this chapter, some scenarios are presented that are used in the ADAM project for this purpose. One scenario explores developments with no mitigation, and thus with high temperature increase and high reliance on adaptation (leading to 4oC increase by 2100 compared to pre-industrial levels). A second scenario explores an ambitious mitigation strategy (leading to 2oC increase by 2100 compared to pre-industrial levels). In the latter scenario, stringent mitigation strategies effectively reduces the risks of climate change, but based on uncertainties in the climate system a temperature increase of 3oC or more cannot be excluded. The analysis shows that, in many cases, adaptation and mitigation are not trade-offs but supplements. For example, the number of people exposed to increased water resource stress due to climate change can be substantially reduced in the mitigation scenario, but even then adaptation will be required for the remaining large numbers of people exposed to increased stress. Another example is sea level rise, for which adaptation is more cost-effective than mitigation, but mitigation can help reduce damages and the cost of adaptation. For agriculture, finally, only the scenario based on a combination of adaptation and mitigation is able to avoid serious climate change impacts.

Reductions in river discharge (water availability) like those from climate change or increased water withdrawal, reduce freshwater biodiversity. We combined two scenarios from the Intergovernmental Panel for Climate Change with a global hydrological model to build global scenarios of future losses in river discharge from climate change and increased water withdrawal. Applying these results to known relationships between fish species and discharge, we build scenarios of losses (at equilibrium) of riverine fish richness. In rivers with reduced discharge, up to 75% (quartile range 4-22%) of local fish biodiversity would be headed toward extinction by 2070 because of combined changes in climate and water consumption. Fish loss in the scenarios fell disproportionately on poor countries. Reductions in water consumption could prevent many of the extinctions in these scenarios