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The current timeline for expected forcing datasets to be updated for the Coupled Model Intercomparison Project (CMIP). Includes updates expected during the CMIP6Plus project, and those for CMIP7. Datasets included are: Anthropogenic short-lived climate forcings (including CO2and CH4) Open biomass burning emissions Land use Greenhouse gas historical concentrations Stratospheric volcanic SO2 emissions and aerosol properties Ozone Nitrogen deposition Solar AMIP boundary forcing Aerosol optical properties/MACv2-SP&nbsp

A global, independent scientific assessment of Carbon Dioxide Removal

By adopting the Sustainable Development Goals (SDGs), countries worldwide agreed to an agenda for achieving a prosperous, socially inclusive and environmentally sustainable future for all1. This ambition, however, also exposes a critical knowledge gap since science-based insights on how to achieve the 17 SDGs simultaneously are lacking. Quantitative goal-seeking scenario studies could enable exploration of the systems' transformations required to achieve the SDGs, but this requires a clear definition of the "target space". The 169 targets and 232 indicators defined by the international community for monitoring SDG implementation cannot be directly used for this purpose. Here, we define a streamlined set of well-defined, science-based indicators and associated target values that is quantifiable and actionable to make quantitative scenario analysis meaningful, relevant (i.e. reflecting societal goals), and yet simple enough to keep analysis transparent and communicable. The set of 36 targets is based on the UN 2030 Agenda, other existing multilateral agreements and insights from sustainability science and expert assessment, and it includes 2050 as an additional longer-term reference point. Thus, this target space provides a strategic focus to guide the scientific community in developing new global sustainable development pathways.

Mitigation scenario ensembles are becoming an important tool to bring new and robust insights into the transition to net zero. This Perspective unpacks their potential and identifies key steps for better use of scenario ensembles and to foster good practices. As they gain new users, climate change mitigation scenarios are playing an increasing role in transitions to net zero. One promising practice is the analysis of scenario ensembles. Here we argue that this practice has the potential to bring new and more robust insights compared with the use of single scenarios. However, several important aspects have to be addressed. We identify key methodological challenges and the existing methods and applications that have been or can be used to address these challenges within a three-step approach: (1) pre-processing the ensemble; (2) selecting a few scenarios or analysing the full ensemble; and (3) providing users with efficient access to the information.

Long-term scenarios play an important role in research on global environmental change. The climate change research community is developing new scenarios integrating future changes in climate and society to investigate climate impacts as well as options for mitigation and adaptation. One component of these new scenarios is a set of alternative futures of societal development known as the shared socioeconomic pathways (SSPs). The conceptual framework for the design and use of the SSPs calls for the development of global pathways describing the future evolution of key aspects of society that would together imply a range of challenges for mitigating and adapting to climate change. Here we present one component of these pathways: the SSP narratives, a set of five qualitative descriptions of future changes in demographics, human development, economy and lifestyle, policies and institutions, technology, and environment and natural resources. We describe the methods used to develop the narratives as well as how these pathways are hypothesized to produce particular combinations of challenges to mitigation and adaptation. Development of the narratives drew on expert opinion to (1) identify key determinants of these challenges that were essential to incorporate in the narratives and (2) combine these elements in the narratives in a manner consistent with scholarship on their inter-relationships. The narratives are intended as a description of plausible future conditions at the level of large world regions that can serve as a basis for integrated scenarios of emissions and land use, as well as climate impact, adaptation and vulnerability analyses.

The risk of seasonal mismatches between electricity supply and demand is increasing due to expanded use of wind, solar and hydropower resources. Power system planners are thus in search of low-cost seasonal energy storage options. Seasonal Pumped-Storage (SPS) can provide short, medium and long-term energy storage at a relatively low-cost and provides co-benefits in the form of freshwater storage capacity. Here, we present the first global assessment of SPS potential, using a novel plant-siting methodology and high-resolution topographical and hydrological data. Our results show that SPS costs vary from 0.007 to 0.2 $/m3 of water stored, 1.8 to 50 $/MWh of energy stored and 0.37 to 0.6 $/GW of installed power generation capacity. The estimated world energy storage capacity below a cost of 50 $/MWh is 17.3 PWh, approximately 79% of the world electricity consumption in 2017.

Correspondence to editor: We agree with the editors that the assumptions behind models of all types, including integrated assessment models (IAMs), should be as transparent as possible. The editors were in error, however, when they implied that the IAM community is just “now emulating the efforts of climate researchers by instigating their own model inter-comparison projects (MIPs).” In fact, model comparisons for integrated assessment and climate models followed a remarkably similar trajectory. Early General Circulation Model (GCM) comparison efforts, evolved to the first Atmospheric Model Inter-comparison Project (AMIP), which was initiated in the early 1990s. Atmospheric models evolved to coupled atmosphere-ocean models (AOGCMs) and results from the first Coupled Model Inter-Comparison Project (CMIP1) become available about a decade later. Results of first energy model comparison exercise, conducted under the auspices of the Stanford Energy Modeling Forum, were published in 1977. A summary of the first comparison focused on climate change was published in 1993. As energy models were coupled to simple economic and climate models to form IAMs, the first comparison exercise for IAMs (EMF-14) was initiated in 1994, and IAM comparison exercises have been on-going since this time.

Scenarios that limit global warming to 1.5 °C describe major transformations in energy supply and ever-rising energy demand. Here, we provide a contrasting perspective by developing a narrative of future change based on observable trends that results in low energy demand. We describe and quantify changes in activity levels and energy intensity in the global North and global South for all major energy services. We project that global final energy demand by 2050 reduces to 245 EJ, around 40% lower than today, despite rises in population, income and activity. Using an integrated assessment modelling framework, we show how changes in the quantity and type of energy services drive structural change in intermediate and upstream supply sectors (energy and land use). Down-sizing the global energy system dramatically improves the feasibility of a low-carbon supply-side transformation. Our scenario meets the 1.5 °C climate target as well as many sustainable development goals, without relying on negative emission technologies.

Human land use activities have resulted in large changes to the biogeochemical and biophysical properties of the Earth’s surface, with consequences for climate and other ecosystem services. In the future, land use activities are likely to expand and/or intensify further to meet growing demands for food, fiber, and energy. As part of the World Climate Research Program Coupled Model Intercomparison Project (CMIP6), the international community has developed the next generation of advanced Earth system models (ESMs) to estimate the combined effects of human activities (e.g., land use and fossil fuel emissions) on the carbon-climate system. A new set of historical data based on the History of the Global Environment database (HYDE), and multiple alternative scenarios of the future (2015-2100) from Integrated Assessment Model (IAM) teams, is required as input for these models. With most ESM simulations forCMIP6 now completed, it is important to document the land use patterns used by those simulations. Here we present results from the Land-Use Harmonization 2 (LUH2) project, which smoothly connects updated historical reconstructions of land use with eight new future projections in the format required for ESMs. The harmonization strategy estimates the fractional land use patterns, underlying land use transitions, key agricultural management information, and resulting secondary lands annually, while minimizing the differences between the end of the historical reconstruction and IAM initial conditions and preserving changes depicted by the IAMs in the future. The new approach builds on a similar effort from CMIP5 and is now provided at higher resolution (0.25◦×0.25◦) over a longer time domain (850–2100, with extensions to 2300) with more detail (including multiple crop and pasture types and associated management practices) using more input datasets (including Landsat remote sensing data) and updated algorithms (wood harvest and shifting cultivation); it is assessed via a new diagnostic package. The new LUH2 products contain > 50 times the information content of the datasets used in CMIP5 and are designed to enable new and improved estimates of the combined effects of land use on the global carbon-climate system.