Quantifying the potential for reservoirs to secure future surface water yields in the world's largest river basins

Surface water reservoirs provide us with reliable water supply, hydropower generation, flood control and recreation services. Yet, reservoirs also cause flow fragmentation in rivers and lead to flooding of upstream areas, thereby displacing existing land-use activities and ecosystems. Anticipated population growth and development coupled with climate change in many regions of the globe suggests a critical need to assess the potential for future reservoir capacity to help balance rising water demands with long-term water availability. Here, we assess the potential of large-scale reservoirs to provide reliable surface water yields while also considering environmental flows within 235 of the world’s largest river basins. Maps of existing cropland and habitat conservation zones are integrated with spatially-explicit population and urbanization projections from the Shared Socioeconomic Pathways (SSP) to identify regions unsuitable for increasing water supply by exploiting new reservoir storage. Results show that even when maximizing the global reservoir storage to its potential limit (~4.3-4.8 times the current capacity), firm yields would only increase by about 50% over current levels. However, there exist large disparities across different basins. The majority of river basins in North America are found to gain relatively little firm yield by increasing storage capacity, whereas basins in Southeast Asia display greater potential for expansion as well as proportional gains in firm yield under multiple uncertainties. Parts of Europe, the United States and South America show relatively low reliability of maintaining current firm yields under future climate change, whereas most of Asia and higher latitude regions display comparatively high reliability. Findings from this study highlight the importance of incorporating different factors, including human development, land-use activities, and climate change, over a time span of multiple decades and across a range of different scenarios when quantifying available surface water yields and the potential for reservoir expansion

The MESSAGEix Integrated Assessment Model and the ix modeling platform (ixmp)

The MESSAGE Integrated Assessment Model (IAM) developed by IIASA has been a central tool of energy-environment-economy systems analysis in the global scientific and policy arena. It played a major role in the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC); it provided marker scenarios of the Representative Concentration Pathways (RCPs) and the Shared Socio-Economic Pathways (SSPs); and it underpinned the analysis of the Global Energy Assessment (GEA). Alas, to provide relevant analysis for current and future challenges, numerical models of human and earth systems need to support higher spatial and temporal resolution, facilitate integration of data sources and methodologies across disciplines, and become open and transparent regarding the underlying data, methods, and the scientific workflow. In this manuscript, we present the building blocks of a new framework for an integrated assessment modeling platform; the \ecosystem" comprises: i) an open-source GAMS implementation of the MESSAGE energy++ system model integrated with the MACRO economic model; ii) a Java/database backend for version-controlled data management, iii) interfaces for the scientific programming languages Python & R for efficient input data and results processing workflows; and iv) a web-browser-based user interface for model/scenario management and intuitive \drag-and-drop" visualization of results. The framework aims to facilitate the highest level of openness for scientific analysis, bridging the need for transparency with efficient data processing and powerful numerical solvers. The platform is geared towards easy integration of data sources and models across disciplines, spatial scales and temporal disaggregation levels. All tools apply best-practice in collaborative software development, and comprehensive documentation of all building blocks and scripts is generated directly from the GAMS equations and the Java/Python/R source code

Tracing international migration in projections of income and inequality across the Shared Socioeconomic Pathways

The Shared Socioeconomic Pathways (SSPs) represent five narratives of future development used for climate change research. They include quantified projections of socioeconomic variables such as population, income levels, inequalities, and emissions over the twenty-first century. The SSP’s population projections embody explicit, pathway-specific international migration assumptions, which are only implicit in the projections of other variables. In this contribution, we explicitly quantify the effects of international migration on income levels and income inequality across and within countries by comparing the original SSP projections to scenarios of zero migration. Income projections without migration are obtained by removing two effects of migration on income dynamics: changes in population size and remittances sent to origin countries. We base our remittance estimates on migrant stocks derived from bilateral migration flow estimates obtained from a gravity model. We find that, on average, migration tends to make the world richer in all SSP narratives. The nature of migration and remittance corridors is shaped by the specific scenario of future development considered. Depending on the particular SSP narrative and world region considered, the effects of migration on income can be substantial, ranging from −5 to +21% at the continental level. We show that migration tends to decrease income inequality across countries and within country in most destination countries but does not affect within-country inequality in origin countries. This new set of projections is consistent with the interdisciplinary framework of the SSPs, which makes it particularly useful for assessing global climate and sustainable development policy options

An emission pathway classification reflecting the Paris Agreement climate objectives

The 2015 Paris Agreement sets the objectives of global climate ambition as expressed in itslong-term temperature goal and mitigation goal. The scientific community has explored thecharacteristics of greenhouse gas emission reduction pathways in line with the ParisAgreement. However, when categorizing such pathways, the focus has been put on thetemperature outcome and not on emission reduction objectives. Here we propose a pathwayclassification that aims to comprehensively reflect the climate criteria set out in the ParisAgreement. We show how such an approach allows for a fully consistent interpretation of theAgreement. For Paris Agreement compatible pathways, we report net zero CO2 and greenhousegas emissions around 2050 and 2065, respectively. We illustrate how pathway designcriteria not rooted in the Paris Agreement, such as the 2100 temperature level, result inscenario outcomes wherein about 6 - 24% higher deployment (interquartile range) of carbondioxide removal is observed

Secure robust carbon dioxide removal policy through credible certification

Carbon Dioxide Removal (CDR) is a key element of any mitigation strategy aiming to achieve the long-term temperature goal of the Paris Agreement, as well as national net-zero and net-negative greenhouse gas emissions targets. For robust CDR policy, the credibility of certification schemes is essential

Uncompensated claims to fair emission space risk putting Paris Agreement goals out of reach

Addressing questions of equitable contributions to emission reductions is important to facilitate ambitious global action on climate change within the ambit of the Paris Agreement. Several large developing regions with low historical contributions to global warming have a strong moral claim to a large proportion of the remaining carbon budget (RCB). However, this claim needs to be assessed in a context where the RCB consistent with the long-term temperature goal (LTTG) of the Paris Agreement is rapidly diminishing. Here we assess the potential tension between the moral claim to the remaining carbon space by large developing regions with low per capita emissions, and the collective obligation to achieve the goals of the Paris Agreement. Based on scenarios underlying the IPCC's 6th Assessment Report, we construct a suite of scenarios that combine the following elements: (a) two quantifications of a moral claim to the remaining carbon space by South Asia, and Africa, (b) a 'highest possible emission reduction' effort by developed regions (DRs), and (c) a corresponding range for other developing regions (ODR). We find that even the best effort by DRs cannot compensate for a unilateral claim to the remaining carbon space by South Asia and Africa. This would put the LTTG firmly out of reach unless ODRs cede their moral claim to emissions space and, like DRs, pursue highest possible emission reductions, which would also constitute an inequitable outcome. Furthermore, regions such as Latin America would need to provide large-scale negative emissions with potential risks and negative side effects. Our findings raise important questions of perspectives on equity in the context of the Paris Agreement including on the critical importance of climate finance. A failure to provide adequate levels of financial support to compensate large developing regions to emit less than their moral claim will put the Paris Agreement at risk