Laurent Drouet

Scenarios towards limiting global mean temperature increase below 1.5 °C

The 2015 Paris Agreement calls for countries to pursue efforts to limit global-mean temperature rise to 1.5u2009°C. The transition pathways that can meet such a target have not, however, been extensively explored. Here we describe scenarios that limit end-of-century radiative forcing to 1.9u2009Wu2009m−2, and consequently restrict median warming in the year 2100 to below 1.5u2009°C. We use six integrated assessment models and a simple climate model, under different socio-economic, technological and resource assumptions from five Shared Socio-economic Pathways (SSPs). Some, but not all, SSPs are amenable to pathways to 1.5u2009°C. Successful 1.9u2009Wu2009m−2 scenarios are characterized by a rapid shift away from traditional fossil-fuel use towards large-scale low-carbon energy supplies, reduced energy use, and carbon-dioxide removal. However, 1.9u2009Wu2009m−2 scenarios could not be achieved in several models under SSPs with strong inequalities, high baseline fossil-fuel use, or scattered short-term climate policy. Further research can help policy-makers to understand the real-world implications of these scenarios.Scenarios that constrain end-of-century radiative forcing to 1.9u2009Wu2009m–2, and thus global mean temperature increases to below 1.5u2009°C, are explored. Effective scenarios reduce energy use, deploy CO2 removal measures, and shift to non-emitting energy sources.

A multi-model assessment of the co-benefits of climate mitigation for global air quality

We present a model comparison study that combines multiple integrated assessment models with a reduced-form global air quality model to assess the potential co-benefits of global climate mitigation policies in relation to the World Health Organization (WHO) goals on air quality and health. We include in our assessment, a range of alternative assumptions on the implementation of current and planned pollution control policies. The resulting air pollution emission ranges significantly extend those in the Representative Concentration Pathways. Climate mitigation policies complement current efforts on air pollution control through technology and fuel transformations in the energy system. A combination of stringent policies on air pollution control and climate change mitigation results in 40% of the global population exposed to PM levels below the WHO air quality guideline; with the largest improvements estimated for India, China, and Middle East. Our results stress the importance of integrated multisector policy approaches to achieve the Sustainable Development Goals.

Trade-offs between energy cost and health impact in a regional coupled energy?air quality model: the LEAQ model

This letter presents a methodology for an integrated energy?air quality model in a cost and impact trade-off framework, applicable at the regional scale. ETEM (the Energy Technology Environmental Model) minimizes the energy cost at a given level of sectoral emissions. An efficient, reduced-order Eulerian air quality model (TAPOM-Lite) simulates some consecutive days where the meteorological conditions are favorable to the occurrence of an ozone episode. A health impact function has been developed to perform the feedback from ozone concentrations to the energy cost. The decomposition optimization problem is solved using an Oracle-based technique. We report on an implementation for the Grand Duchy of Luxembourg, varying the parameters of the impact function.

The WITCH 2016 Model - Documentation and Implementation of the Shared Socioeconomic Pathways

This paper describes the WITCH - World Induced Technical Change Hybrid - model in its structure, calibration, and the implementation of the SSP/RCP scenario implementation. The WITCH model is a regionally disaggregated hard-linked model based on a Ramsey type optimal growth model and a detailed bottom-up energy sector model. A particular focus of the model is the modeling or technical change and RnD investments and the analysis of cooperative and non-cooperative climate policies. Moreover, the WITCH 2016 version now includes land-use change modeling based on the GLOBIOM model, and air pollutants, as well as detailed modeling of the transport sector and the possibility for stochastic modeling. This version has been also used to implement the Shared Socioeconomic Pathways (SSPs) set of scenarios and RCP based climate policies to provide a new set of climate scenarios. In this paper, we describe in detail the mathematical formulation of the WITCH model, the solution method and calibration, as well as the implementation of the five SSP scenarios. This report therefore provides detailed information for interested users of the model, and for understanding the implementation of the different “worlds of the SSP.

Accounting for Uncertainty Affecting Technical Change in an Economic-Climate Model

The key role of technological change in the decline of energy and carbon intensities of aggregate economic activities is widely recognized. This has focused attention on the issue of developing endogenous models for the evolution of technological change. With a few exceptions this is done using a deterministic framework, even though technological change is a dynamic process which is uncertain by nature. Indeed, the two main vectors through which technological change may be conceptualized, learning through R&D investments and learning-by-doing, both evolve and cumulate in a stochastic manner. How misleading are climate strategies designed without accounting for such uncertainty? The main idea underlying the present piece of research is to assess and discuss the effect of endogenizing this uncertainty on optimal R&D investment trajectories and carbon emission abatement strategies. In order to do so, we use an implicit stochastic programming version of the FEEM-RICE model, first described in Bosetti, Carraro and Galeotti, (2005). The comparative advantage of taking a stochastic programming approach is estimated using as benchmarks the expected-value approach and the worst-case scenario approach. It appears that, accounting for uncertainty and irreversibility would affect both the optimal level of investment in R&D –which should be higher– and emission reductions –which should be contained in the early periods. Indeed, waiting and investing in R&D appears to be the most cost-effective hedging strategy.

Low-emission pathways in 11 major economies: comparison of cost-optimal pathways and Paris climate proposals

In order to evaluate the effectiveness of climate policy, it is important to understand emission trends and policies at the national level. The 2015 Paris Agreement includes (Intended) Nationally Determined Contributions, so-called (I)NDCs, outlining the contribution of different Parties to the overall target of the agreement to limit global mean temperature increase to well below 2xa0°C. Here, we assess emission trajectories and the energy system transition of 11 major economies (in the remainder: countries) projected by integrated assessment models (IAMs) for baseline and cost-optimal 450xa0ppm CO2 eq mitigation scenarios and compare the results with the (I)NDCs. Limiting global temperature increase to below 2xa0°C implies a substantial reduction of the estimated available carbon budget for each country. The national carbon budgets between 2010 and 2100 showed reductions between the baseline and the 2xa0°C consistent mitigation scenario ranging from 52% in South Korea to 95% in Brazil. While in the baseline scenario, the share of low-carbon primary energy sources is projected to remain around 15% (with Brazil being a notable exception, reaching 30%); in the mitigation scenarios, the share of low-carbon energy is projected to increase to over 50% in 2050 in nearly all countries, with the EU, Japan and Canada reaching the largest shares. Comparison with the (I)NDCs shows that in Brazil, Canada, the EU, Mexico (conditional target), South Korea and the USA, the emission reduction targets of the NDCs are closer to the mitigation requirement of the 2xa0°C scenario; in other countries, however, there is still a large gap. The national detail of the indicators adds to the literature on low-carbon emission pathways, assists the assessment of the Paris Agreement and provides support to national policymakers to identify focus areas for climate policy in the coming years.

Delineating Spring Recharge Areas in a Fractured Sandstone Aquifer (Luxembourg) Based on Pesticide Mass Balance

A simple method to delineate the recharge areas of a series of springs draining a fractured aquifer is presented. Instead of solving the flow and transport equations, the delineation is reformulated as a mass balance problem assigning arable land in proportion to the pesticide mass discharged annually in a spring at minimum total transport cost. The approach was applied to the Luxembourg Sandstone, a fractured-rock aquifer supplying half of the drinking water for Luxembourg, using the herbicide atrazine. Predictions of the recharge areas were most robust in situations of strong competition by neighbouring springs while the catchment boundaries for isolated springs were extremely sensitive to the parameter controlling flow direction. Validation using a different pesticide showed the best agreement with the simplest model used, whereas using historical crop-rotation data and spatially distributed soil-leaching data did not improve predictions. The whole approach presents the advantage of integrating objectively information on land use and pesticide concentration in spring water into the delineation of groundwater recharge zones in a fractured-rock aquifer.RésuméUne méthode simple pour définir des aires de recharge d’un ensemble de sources drainant un aquifère fracturé est présentée. Au lieu de résoudre les équations de lécoulement et de tranport, la délimitation est reformulée comme un problème de bilan massique, assignant à la surface cultivable la masse de pesticide observée annuellement à la source en considérant le plus court chemin. Lapproche a été appliquée au grès de Luxembourg, un aquifère fracturé fournissant la moitié de leau potable du Luxembourg, en utilisant lherbicide atrazine. La prédiction des zones dalimentation est apparue plus robuste lorsqu’elles sont en situation de forte concurrence dans le cas de sources voisines, tandis que les limites des bassins versants des sources isolées sont apparues extrêmement sensibles au paramètre contrôlant la direction de l’écoulement. Une validation à partir d’un autre pesticide a montré une bonne concordance avec le modèle utilisé le plus simple, alors que l’utilisation d’un historique de données de rotation des cultures et des données distribuées de lixiviation des sols n’a pas amélioré les prédictions. L’approche complète présente l’avantage d’intégrer objectivement les informations sur l’occupation du sol et les concentration en pesticide dans l’eau de la source dans la définition des zones de recharge d’un aquifère fracturé.ResumenSe presenta un método simple para delimitar las áreas de recarga de una serie de manantiales que drenan un acuífero fracturado. En lugar de resolver las ecuaciones de flujo y transporte, la delimitación se reformula como un problema de balance de masa asignando la tierra cultivable en proporción a la masa de pesticida descargada anualmente en un manantial del transporte total a un costo mínimo. El enfoque fue aplicado en la Arenisca Luxemburgo, un acuífero en roca fracturada que suministra la mitad de agua potable a Luxemburgo, usando el herbicida atrazina. Las predicciones de zonas de capturas fueron más robustas en situaciones de fuerte competencia entre manantiales vecinos mientras que los límites de la cuenca para manantiales aislados fueron extremadamente sensibles a los parámetros que controlan la dirección de flujo. La validación usando pesticidas diferentes mostraron una buena concordancia con el modelo más simple utilizado, mientras que el uso de datos históricos de rotación de cultivos y datos de lixiviación de suelos distribuidos espacialmente no mejoraron las predicciones. El enfoque presenta la ventaja de la integrar objetivamente la información del uso de la tierra y la concentración de pesticidas en el agua del manantial para la delimitación de las zonas de recarga en un acuífero de rocas fracturadas.ResumoApresenta-se um método simples para a delineação de áreas de recarga de uma série de nascentes que drenam um aquífero fraturado. Em vez de resolver as equações de fluxo e transporte, a delineação é reformulada como um problema de balanço de massa, definindo a área de terreno arável proporcionalmente à massa de pesticida que é descarregada anualmente numa nascente, à custa de um transporte total mínimo. Esta metodologia foi aplicada no Arenito do Luxemburgo, que é um aquífero de rocha fraturada que fornece metade da água de abastecimento do Luxemburgo, usando o herbicida atrazina. As previsões em termos de zona de captura revelaram-se mais robustas em zonas onde há uma forte competição entre nascentes vizinhas, enquanto as fronteiras das bacias de nascentes isoladas se revelaram extremamente sensíveis ao parâmetro que controla a direção do fluxo subterrâneo. A validação, usando um pesticida diferente, revelou um bom ajuste com o modelo mais simples que foi usado, enquanto o uso de dados históricos de rotação de culturas e dados espacialmente distribuídos de percolação no solo não contribuíram para melhorar as previsões. A abordagem geral apresenta a vantagem de integrar objetivamente informação sobre o uso do solo e a concentração de pesticidas na água de nascentes na delineação de zonas de recarga de água subterrânea num aquífero fraturado.

Residual fossil CO2 emissions in 1.5-2 °c pathways

The Paris Agreement—which is aimed at holding global warming well below 2u2009°C while pursuing efforts to limit it below 1.5u2009°C—has initiated a bottom-up process of iteratively updating nationally determined contributions to reach these long-term goals. Achieving these goals implies a tight limit on cumulative net CO2 emissions, of which residual CO2 emissions from fossil fuels are the greatest impediment. Here, using an ensemble of seven integrated assessment models (IAMs), we explore the determinants of these residual emissions, focusing on sector-level contributions. Even when strengthened pre-2030 mitigation action is combined with very stringent long-term policies, cumulative residual CO2 emissions from fossil fuels remain at 850–1,150u2009GtCO2 during 2016–2100, despite carbon prices of US

Setting the System Boundaries of “Energy for Water” for Integrated Modeling

130–420 per tCO2 by 2030. Thus, 640–950u2009GtCO2 removal is required for a likely chance of limiting end-of-century warming to 1.5u2009°C. In the absence of strengthened pre-2030 pledges, long-term CO2 commitments are increased by 160–330u2009GtCO2, further jeopardizing achievement of the 1.5u2009°C goal and increasing dependence on CO2 removal.Residual CO2 emissions from fossil fuels limit the likelihood of meeting the goals of the Paris Agreement. A sector-level assessment of residual emissions using an ensemble of IAMs indicates that 640–950u2009GtCO2 removal will be required to constrain warming to 1.5u2009°C.

Climate policy under socio-economic scenario uncertainty

Modeling Page Kyle,*,† Nils Johnson,‡ Evan Davies, David L. Bijl, Ioanna Mouratiadou, Michela Bevione, Laurent Drouet, Shinichiro Fujimori, Yaling Liu,† and Mohamad Hejazi† †Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, Maryland 20740, United States ‡International Institute for Applied Systems Analysis, Laxenburg, Austria University of Alberta, Edmonton, Alberta, Canada Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, Netherlands Potsdam Institute for Climate Impact Research, Potsdam, Germany Fondazione Eni Enrico Mattei, Milan, Italy National Institute for Environmental Studies, Tsukuba, Japan