ALBERT

Description: Green hydrogen and derived electrofuels are attractive replacements for fossil fuels in applications where direct electrification is infeasible. While this makes them crucial for climate neutrality, rapidly scaling up supply is critical and challenging. Here we show that even if electrolysis capacity grows as fast as wind and solar power have done, green hydrogen supply will remain scarce in the short term and uncertain in the long term. Despite initial exponential growth, green hydrogen likely (≥75%) supplies 〈1% of final energy until 2030 in the European Union and 2035 globally. By 2040, a breakthrough to higher shares is more likely, but large uncertainties prevail with an interquartile range of 3.2–11.2% (EU) and 0.7–3.3% (globally). Both short-term scarcity and long-term uncertainty impede investment in hydrogen end uses and infrastructure, reducing green hydrogen’s potential and jeopardizing climate targets. However, historic analogues suggest that emergency-like policy measures could foster substantially higher growth rates, expediting the breakthrough and increasing the likelihood of future hydrogen availability.

Description: Scaling up Carbon Dioxide Removal (CDR) is an urgent priority, as are efforts to rapidly reduce emissions, if we are to meet the temperature goal of the Paris Agreement. Scenarios for limiting warming to well below 2°C involve removing hundreds of billions of tonnes of carbon dioxide (CO2) from the atmosphere over the course of the century. Drawing together analysis across several key areas, this report is the first comprehensive global assessment of the current state of CDR.

Description: The IPCC Assessment Reports offer the scientific foundation for international climate negotiations and constitute an unmatched resource for climate change researchers. However, the assessment cycles take multiple years. As a contribution to cross- and interdisciplinary understanding across diverse climate change research communities, we have streamlined an annual process to identify and synthesise essential research advances. We collected input from experts on different fields using an online questionnaire and prioritised a set of ten key research insights with high policy relevance. This year we focus on: (1) looming overshoot of the 1.5°C warming limit, (2) urgency of phasing-out fossil fuels, (3) challenges for scaling carbon dioxide removal, (4) uncertainties regarding the future of natural carbon sinks, (5) need for join governance of biodiversity loss and climate change, (6) advances in the science of compound events, (7) mountain glacier loss, (8) human immobility in the face of climate risks, (9) adaptation justice, and (10) just transitions in food systems. We first present a succinct account of these Insights, reflect on their policy implications, and offer an integrated set of policy relevant messages. This science synthesis and science communication effort is also the basis for a report targeted to policymakers as a contribution to elevate climate science every year, in time for the UNFCCC COP.

Description: Scenarios from integrated assessment models play a central role in helping policymakers envisage pathways to limit global warming to well below 2 °C. We demonstrate that many models maintain a preference for inefficient combustion, in particular by relying on coal and bioenergy. In contrast to recent evidence from innovation studies, scenarios are optimistic on deployment of lumpy energy-systems technologies, such as carbon capture and storage, while insufficiently reflecting empirically observed innovation dynamics in more granular technologies such as solar photovoltaics. Our analysis shows that two key options for rapid decarbonization remain systematically undersampled in models that underpin IPCC scenarios: A) strong growth in intermittent renewables, in particular solar PV, together with electrification of sectors; and B) widespread adoption of efficient end use technologies enabling high service provision at low levels of energy demand. A combination of continued PV growth and sector coupling with low to medium energy demand (a corridor of 250 to 500 EJ of primary energy) would render carbon neutrality by 2050 feasible, thus enabling near-term cost-effective climate change mitigation and reducing the need for carbon dioxide removal in the 2nd half of the century. Models would benefit from updated cost assumptions, higher resolution on granular end-use technologies, higher resolution on sector coupling, and an overall consideration of demand-side solutions. Such updates – of which some are starting to be explored by modeling teams - are likely to demonstrate that some mitigation pathways are cost saving, rather than costly.

Description: A rapid phase-out of unabated coal use is essential to limit global warming to below 2°C. This review presents a comprehensive assessment of coal transitions in mitigation scenarios consistent with the Paris Agreement, using data from more than 1500 publicly available scenarios generated by more than 30 integrated assessment models. Our ensemble analysis uses clustering techniques to categorize coal transition pathways in models and bridges evidence on technological learning and innovation with historical data of energy systems. Six key findings emerge: First, we identify three archetypal coal transitions within Paris-consistent mitigation pathways. About 38% of scenarios are ‘coal phase out’ trajectories and rapidly reduce coal consumption to near zero. ‘Coal persistence’ pathways (42%) reduce coal consumption much more gradually and incompletely. The remaining 20% follow ‘coal resurgence’ pathways, characterised by increased coal consumption in the second half of the century.. Second, coal persistence and resurgence archetypes rely on the widespread availability and rapid scale-up of carbon capture and storage technology (CCS). Third, coal-transition archetypes spread across all levels of climate policy ambition and scenario cycles, reflecting their dependence on model structures and assumptions. Fourth, most baseline scenarios – including the shared socio-economic pathways (SSPs) - show much higher coal dependency compared to historical observations over the last 60 years. Fifth, coal-transition scenarios consistently incorporate very optimistic assumptions about the cost and scalability of CCS technologies, while being pessimistic about the cost and scalability of renewable energy technologies. Sixth, evaluation against coal-dependent baseline scenarios suggests that many mitigation scenarios overestimate the technical difficulty and costs of coal phase- outs. To improve future research, we recommend using up-to-date cost data and evidence about innovation and diffusion dynamics of different groups of zero or low-carbon technologies. Revised SSP quantifications need to incorporate projected technology learning and consistent cost structures, while reflecting recent trends in coal consumption.