Scientific publications

Europe's pursuit of net-zero emissions by 2050 is driven by the urgent need to contribute to global climate efforts and enhance its energy security, reducing its reliance on imported fossil fuels. The path to net zero entails a significant, economy-wide uptake of clean energy technologies. However, geopolitical tensions impeding trade, resource unavailability, or sociopolitical factors may give rise to considerable constraints to the uptake of such technologies. Using a diverse model ensemble, we explore the implications of limitations in terms of availability of critical low-carbon technologies such as renewables and batteries, biomass, and carbon capture and storage. Our findings suggest that such constraints could impact mitigation efforts as costlier alternatives become essential, compromise energy security while increasing reliance on fossil fuel imports, and drive cumulative emissions upwards, essentially jeopardising the EU's mid-century climate targets. We underscore the need for resilient energy-system transformations capable of withstanding geopolitical and technological disruptions, including policies prioritising the acceleration of energy efficiency and renewable energy diffusion.

Ammonia, the foundation of fertilizers, grows food that feed 3.8 billion people. While recent efforts focus on ammonia emissions and costs, water use and scarcity risks remain understudied. We quantify water consumption of ammonia production, evaluate exposure to water scarcity for each of the 406 global plants, and trace how fertilizer trade redistributes water stress across supply chains, estimating how many people rely on food grown with fertilizers produced in water-scarce regions. We find that ∼18% of global ammonia output (∼33 Mt NH3 yr–1) experiences at least one month of scarcity annually. The sector’s reliance on 406 large, geographically concentrated plants further heightens vulnerability, as local shortages can cascade globally through highly interconnected trade networks. Five exporters (China, Russia, Egypt, Saudi Arabia, and Qatar) account for half of global fertilizer exports, linking the food security of 637 million people to production under water-stressed conditions. Major importers such as Brazil, the U.S., and India are indirectly exposed to water scarcity in distant basins, with the largest trade routes including Qatar–U.S., Qatar–Brazil, and China–Brazil. We show that water scarcity at ammonia production sites represents not merely a local constraint but a systemic risk to global food systems, highlighting the importance of explicitly incorporating water availability into decarbonization strategies and trade policies.

Hydrogen will play a critical role in decarbonizing diverse economic sectors. However, given limited sustainable resources and the energy-intensive nature of its production, prioritizing its applications will be essential. Here, we analyse approximately 2,000 (low-carbon) hydrogen projects worldwide, encompassing operational and planned initiatives until 2043, quantifying their greenhouse gas (GHG) emissions and mitigation potential from a life cycle perspective. Our results demonstrate the variability in GHG emissions of hydrogen applications, depending on the geographical location and hydrogen source used. The most climate-effective hydrogen applications include steel-making, biofuels and ammonia, while hydrogen use for road transport, power generation and domestic heating should be discouraged as more favourable alternatives exist. Planned low-carbon hydrogen projects could generate 110 MtH2 yr−1, emit approximately 0.4 GtCO2e yr−1, and potentially reduce net life cycle GHG emissions by 0.2–1.1 GtCO2e yr−1 by 2043, depending on the substituted product or service. Addressing the current hydrogen implementation gap and prioritizing climate-effective applications are crucial for meeting decarbonization goals.

Linking existing models to extend energy system and integrated assessment analysis is an increasingly common practice. Despite this, and unlike in the field of environmental and earth sciences, little attention has so far been paid to the details of it, to the trade-offs involved and the way in which the model linking affects the interpretation of the outcomes of the interlinked model system. Our aim in this paper is to first focus on a set of key technical and methodological problems that are common in model linking and suggest how these could be approached in different model linking contexts. We then further explore how model linking may affect the nature of the knowledge produced, and how this should be considered in the model linking process. Reflecting our literature driven assessment of the issues and possible solutions, we compile “a check list” to assist in the process of decision making for model linking.

Energy systems models (ESMs) and Integrated Assessment Models (IAMs) are key tools in developing long-term bottom-up-based transformation pathways. Yet feasibility is typically addressed only after scenario generation, if at all. In this article the authors explore the possibilities for change from the perspective of practitioners of scenario-based studies. We follow the argumentation that this narrow treatment is inadequate and feasibility concerns should be integrated into the entire modelling process—from the design phase of the study to interpretation and communication. With this in mind, the article pursues to offer practical and broadly applicable approaches to systematically embed feasibility considerations into industrial decarbonisation scenario studies; emphasise that feasibility encompasses more than economic viability, including institutional, social, environmental, and technological dimensions; and theoretically show how feasibility assessments can be meaningfully integrated throughout the modelling process. Rather than proposing an entirely new theoretical framework, this study presents a comprehensive and practice-oriented concept based on current literature and developed from the perspective of experienced modellers. It illustrates how feasibility concerns can be systematically addressed across the full modelling workflow.

A circular economy can contribute to reduce the demand for emission-intensive basic materials and to efficiently decarbonize the industry. However, current energy system models are not able to adequately depict this contribution in industry transformation pathways to guide policy making. To address this gap, we integrated material flow and industry modelling for a circular economy in buildings. Results show that a circular economy in buildings addressing material production, building design, and building use could reduce industrial material production, captured emissions, energy demand and cumulated costs for industry decarbonisation. It reduces particularly the use of hydrogen and carbon capture, which are associated with implementation barriers. The findings imply that a circular economy could contribute to the decarbonisation of the industry sector and that it is necessary to develop new policies that split financial burdens, incentivize collaborations and facilitate the more intense use of buildings.

The transition towards climate-neutral industry is a challenge, particularly for heavy industries like steel and basic chemicals. Existing models for assessing industrial transformation often lack spatial resolution and fail to capture individual investment decisions. Consequently, the spatial interplay between industry transformation, energy availability, infrastructure availability, and the dynamics of discrete investments is inadequately addressed. Here we present a site-specific approach that considers individual industrial sites to simulate discrete investment decisions. The investment decision is modelled as a discrete choice among alternative technologies with their total cost of ownership as the main decision criterion. Process costs depend on the scenario-specific assumptions, such as energy carrier prices, policy instruments and local infrastructures. The age of production units and their reinvestment cycles are considered the main restrictions on the dynamics of the transition. The results provide high spatial resolution to capture the spatial and temporal dynamics of industry transition under varying process and policy assumptions. The presented model and its results can be coupled with energy system models to assess the implications of site-specific industry transition on energy system related research questions. We conduct an exemplary case study for a transformation pathway of the European primary steel production.

Climate-neutral hydrogen is a promising option to replace fossil fuels and reduce greenhouse gas emissions in energy-intensive industries. At the same time, spatial and timely dynamics of hydrogen market diffusion are uncertain. This study simulates the market diffusion of hydrogen-based production routes for the entire European plant stock of primary steel, high-value chemicals, methanol, and ammonia production sites. The model includes a total of 158 plants at 96 sites and explicitly considers hydrogen infrastructure, plant ages, production capacities and reinvestment cycles. Sixteen scenario sensitivities were defined to analyse various future hydrogen and carbon dioxide price pathways. The results show that one investment opportunity remains until 2050 for all plants, while 36% of plants require reinvestment before 2030. The cost-competitiveness of hydrogen-based production varies across products: Methanol and high-value chemicals can only be competitive with hydrogen prices below 60 €/MWh. For steel, a high carbon dioxide price and natural gas-fired direct reduction can mitigate fossil lock-ins using natural gas as bridging option towards full use of hydrogen. The study highlights the risk of reinvesting in fossil technologies without additional policies. The maximum technical hydrogen demand potential is 1000 TWh, but considering techno-economic limitations in the sensitivities, only 64 to 507 TWh can be reached. The planned future hydrogen network matches most reinvestment needs.

This opinion piece discusses six ways, in which the capacity to evaluate progress in SDGs vis-à-vis efforts to mitigate climate change using IAMs is currently being enhanced to offer robust and actionable policy prescriptions that may place climate policy in a holistic sustainable development context.

The reduction of the EU's pipeline gas imports from Russia because of the Russian war against Ukraine has had severe economy-wide implications for the bloc. Using a multisector integrated assessment model (GCAM), we find that a potential complete cut-off of Russian pipeline gas exports to the EU unevenly impacts the energy mix and gas prices across subregions within the EU, depending on their access to alternative gas pipelines and liquefied natural gas infrastructure. The restrictions also affect global gas infrastructure capacity additions, asset stranding, and trade dynamics. Our results show that the Fit-for-55 policy framework already improves the EU's resilience against a cut-off of Russian pipeline gas, while additional improvements in energy efficiency and renewable targets could further soften impacts.

A prospective life cycle assessment was performed for global ammonia production across 26 regions from 2020 to 2050. The analysis was based on the IEA Ammonia Roadmap and IMAGE electricity scenarios model for three climate scenarios related to a mean surface temperature increase of 3.5 °C, 2.0 °C, and 1.5 °C by 2100. Combining these models with a global perspective and new life cycle inventories improves ammonia's robustness, quality, and applicability in prospective life cycle assessments. It reveals that complete decarbonisation of the ammonia industry by 2050 is unlikely from a life cycle perspective because of residual emissions in the supply chain, even in the most ambitious scenario. However, strong policies in the 1.5 °C scenario could significantly reduce climate impacts by up to 70% per kilogram of ammonia. The cumulative greenhouse gas emissions from the ammonia supply chain between 2020 and 2050 are estimated at 24, 21, and 15 gigatonnes CO2-equivalent for the 3.5 °C, 2.0 °C, and 1.5 °C scenarios, respectively. The paper examines challenges in achieving these scenarios, noting that electrolysis-based (yellow) ammonia, contingent on electricity decarbonisation, offers a cleaner production pathway. However, achieving significant GHG reductions is complex, requiring advancements in technologies with lower readiness, like carbon capture and storage and methane pyrolysis. The study also discusses limitations such as the need to reduce urea demand, potential growth in ammonia as a fuel, reliance on CO2 transport and storage, expansion of renewable energy, raw material scarcity, and the longevity of existing plants. It highlights potential shifts in environmental impacts, such as increased land, metal, and mineral use in scenarios with growing renewable electricity and bioenergy with carbon capture and storage.