If rapid and just transformations to low-carbon societies are to take place, citizens need to obtain the necessary knowledge and skills to critically examine and choose adequate climate policy options. An emphasis on critical climate education research and implementation is therefore required.
Various methods of carbon dioxide removal (CDR) are being pursued in response to the climate crisis, but they are mostly not proven at scale. Climate experts are divided over whether CDR is a necessary requirement or a dangerous distraction from limiting emissions. In this Viewpoint, six experts offer their views on the CDR debate.
Clean energy technological innovations are widely acknowledged as a prerequisite to achieving ambitious long-term energy and climate targets. However, the optimal speed of their adoption has been parsimoniously studied in the literature. This study seeks to identify the optimal intensity of moving to a green hydrogen electricity sector in Greece, using the OSeMOSYS energy modeling framework. Green hydrogen policies are evaluated, first, on the basis of their robustness against uncertainty and, afterwards, against conflicting performance criteria and for different decision-making profiles towards risk, by applying the VIKOR and TOPSIS multi-criteria decision aid methods. Although our analysis focuses exclusively on the power sector and compares different rates of hydrogen penetration compared to a business-as-usual case without considering other game-changing innovations (such as other types of storage or carbon capture and storage), we find that a national transition to a green hydrogen economy can support Greece in potentially cutting at least 16 MtCO2 while stimulating investments of EUR 10–13 bn. over 2030–2050.
The extent to which modelled future pathways support effective policymaking for sustainability transitions has been questioned for a long time, with one major issue being the insufficient integration with the perspectives of policymakers and other stakeholders. One proposal to address this issue has been to set up facilitative dialogues with stakeholders to extend model-based pathways to socio-technical scenarios. This paper presents the results of a first series of such co-creation workshops, where stakeholders discussed bottlenecks for model-based decarbonisation pathways and ways to overcome these bottlenecks through tailored policy mixes. The workshops took place in five countries: Brazil, Canada, Greece, Germany, and the UK, each with a specific sector focus. In all five workshops, it became clear that substantial tensions exist between the “ideal” modelled decarbonisation pathways and the real-world situation on the ground. Also, adverse political framework conditions, uncertainty of future policies and resistance of powerful actors were emphasised as overarching bottlenecks in most workshops. At the same time, in several instances stakeholders pointed out important aspects of transformative trajectories that are not covered by the models. Some challenges and solutions stand out in all countries in spite of the strong diversity of contexts: allocation of capital towards massive investments into low-carbon solutions; infrastructure development for generation and transport of hydrogen, capture and use of CO2 as well as electricity grid and storage adapted to renewable energy solutions; stakeholder and citizen dialogues, where agreement is reached on cornerstones of long-term decarbonisation trajectories; and demand-side measures complementing investments into low-carbon processes.
Mitigation scenarios have become an important element of Intergovernmental Panel on Climate Change (IPCC) reports. We critically assess the curation of the IPCC mitigation scenarios database, with a focus on improving curation and utilisation. The existing method of curation favours particular models, and results may have limited statistical meaning. We draw lessons from experiences with the Coupled Model Intercomparison Project (CMIP) used by the IPCC Working Group I and II communities. We propose that the scientific community takes a more active role in curating the database around policy-relevant knowledge gaps, through an open and peer reviewed process of Model Intercomparison Projects (MIPs) supplemented with individual model studies. The database should be publicly accessible from the time of scenario submission, and actively involve a broad community in developing tools and analysing the database. These suggestions can broaden participation, increase transparency, and enhance the relevance of the database for users.
Understanding how 1.5 °C pathways could adjust in light of new adverse information, such as a reduced 1.5 °C carbon budget, or slower-than-expected low-carbon technology deployment, is critical for planning resilient pathways. We use an integrated assessment model to explore potential pathway adjustments starting in 2025 and 2030, following the arrival of new information. The 1.5 °C target remains achievable in the model, in light of some adverse information, provided a broad portfolio of technologies and measures is still available. If multiple pieces of adverse information arrive simultaneously, average annual emissions reductions near 3 GtCO2/yr for the first five years following the pathway adjustment, compared to 2 GtCO2/yr in 2020 when the Covid-19 pandemic began. Moreover, in these scenarios of multiple simultaneous adverse information, by 2050 mitigation costs are 4-5 times as high as a no adverse information scenario, highlighting the criticality of developing a wide range of mitigation options, including energy demand reduction options.
Low-income population groups often face high energy poverty risks. This phenomenon can be exacerbated through the implementation of ambitious environmental policies to achieve the energy transition—said policies, such as the application of additional taxes on energy products, may lead to regressive social and distributional impacts on low-income households thus increasing the risk of energy poverty. This study focusses on Greece and combines a qualitative analysis of the EU and Greek policy context and strategic framework for energy poverty as well as related poverty alleviation measures with a state-of-the-art model-based assessment of the equity and distributional impacts of the net-zero transition in the country. We use the GEM-E3-FIT general equilibrium model, expanded to represent ten income classes differentiated by income sources, saving rates and consumption patterns. The new modelling capabilities of GEM-E3-FIT are applied to quantify the distributional impacts of ambitious emission reduction targets and at the same time explore their effects on energy-related expenditure and energy poverty by income class in Greece. The country’s transition to climate neutrality increases modestly the income inequality across income classes, with low-income households facing the most negative effects. However, using carbon tax revenues as lump-sum transfers to support household income and as reduced social security contributions have the potential to boost employment and scale down income inequality in Greece.
The proposed framework is an intuitively obvious one, yet still serves as a climate technology-specific “checklist” to ensure that any newly proposed technologies or products can succeed. There will be continuous changes to the regulations, infrastructures, and political contexts, in which new technologies will be developed, which is why each consideration is not intended as a one-shot “yes/no” process but must rather be continuously reviewed and reconsidered in light of potentially rapid developments.
Climate change and air pollution are two interconnected major risks for human health. For calculations of the health co-benefits, we combine the Global Change Analysis Model (GCAM) with rfasst, a tool designed to calculate a range of adverse health and agricultural effects attributable to air pollution for alternative scenarios. In summary, health co-benefits associated with current policies and nationally determined contributions are relatively small. The results show that to reduce health impacts attributable to ambient air pollution rapidly, additional policy action that is explicitly designed for tackling air pollutant emissions will be needed.
The COP26 Glasgow process resulted in many countries strengthening their 2030 emissions reduction targets and announcing net-zero pledges for 2050–2070 but it is not clear how this would impact future warming. Here, we use four diverse integrated assessment models (IAMs) to assess CO2 emission trajectories in the near- and long-term on the basis of national policies and pledges, combined with a non-CO2 infilling model and a simple climate model to assess the temperature implications. We also consider the feasibility of national long-term pledges towards net-zero. While near-term pledges alone lead to warming above 2 °C, the addition of long-term pledges leads to emissions trajectories compatible with a future well below 2 °C, across all four IAMs. However, while IAM heterogeneity translates to diverse decarbonization pathways towards long-term targets, all modelled pathways indicate several feasibility concerns, relating to the cost of mitigation and the rates and scales of deployed technologies and measures.
Climate change is having profound impacts on human and natural systems. In recent years, there has been growing recognition of the need to address Loss and Damage (L&D) associated with the adverse effects of climate change, particularly in developing countries that are more vulnerable to its impacts. There is a range of studies, examining the concepts, resilience, adaptation and policy options for dealing with climate change losses and damages. This article discusses the actions, research and finance needs in Loss & Damage as well as the approaches to it on some topics such as adaptation, stakeholder engagement, governance and risk transfer.
Our plans to tackle climate change could be thrown off-track by shocks such as the coronavirus pandemic, the energy supply crisis driven by the Russian invasion of Ukraine, financial crises and other such disruptions. We should therefore identify plans which are as resilient as possible to future risks, by systematically understanding the range of risks to which mitigation plans are vulnerable and how best to reduce such vulnerabilities. Here, we use electricity system decarbonization as a focus area, to highlight the different types of technological solutions, the different risks that may be associated with them, and the approaches, situated in a decision-making under deep uncertainty (DMDU) paradigm, that would allow the identification and enhanced resilience of mitigation pathways.
While fossil fuel prices soar during the 2022 global energy crisis, the European Union activates all available fossil-fuel levers and Greece still plans to use natural gas as a transition fuel for delignitisation, with strong concerns over potential exacerbation of energy poverty and hurdles to progress in climate action. This study assesses the trajectory of the Greek electricity mix and its reliance on natural gas under the current policy framework on the one hand, and an ambitious scenario aiming for complete decarbonisation by 2035 on the other. We model these scenarios using an energy system modelling framework, comprising LEAP and OSeMOSYS model implementations for Greece, and use a stakeholder-informed fuzzy cognitive mapping exercise to uncover transition uncertainties. While power generation from natural gas is projected to increase by almost 50% until 2030 under existing policies, the proposed decarbonisation scenario has the potential to achieve complete independence from Russian gas by 2026 while also leading to a cleaner and considerably cheaper power sector. This ‘higher climate ambition’ scenario is found feasible and more robust in case high fossil fuel prices persist post-2022, even if bottlenecks stressed by stakeholders such as community acceptance or technological constraints emerge and potentially constrain the expansion of certain renewable energy technologies. Apart from the added value of stakeholder input in modelling science, as reflected in the impact of barriers Greek stakeholders critically highlighted, our results emphasise that a diversified energy-supply mix alongside bold energy efficiency strategies are key to rapid and feasible decarbonisation in the country.
There are multiple ways in which society can theoretically transition from its current carbon-intensive state to a zero-carbon future, ideally fast enough to limit global warming to 1.5oC above pre-industrial levels. Although the carbon budget associated with this temperature is close to being consumed (IPCC 2021), it still remains achievable - just. Furthermore, we know what needs to be done to achieve it, because we know what contributes to CO2 emissions. We need energy sources, whose carbon content results in emissions. Reducing both our demand for energy and its carbon intensity (by increasing the share of zero-carbon fuels in our energy mix) is thus of paramount importance. Some industrial manufacturing processes, particularly in cement production, produce CO2 as a chemical by-product. Capturing that CO2, finding alternative ways to produce cement, or reducing cement demand, is therefore necessary. Our agriculture, forestry and other land use (AFOLU) can be a net source or sink of CO2, so making it a large net sink by enhancing carbon dioxide removals (CDR), for example through afforestation, would help. And we hope to have available a range of human-made CDR technologies and measures, such as bioenergy with carbon capture and storage (BECCS), Direct Air Capture (DAC) and enhanced weathering (EW). Scaling these in an
environmentally sustainable way would enhance our chances of keeping within the carbon budget. Finally, rapid progress in reducing short-lived greenhouse gases, particularly methane, would further help our chances of achieving 1.5oC.
While the Intergovernmental Panel on Climate Change (IPCC) physical science reports usually assess a handful of future scenarios, the Working Group III contribution on climate mitigation to the IPCC's Sixth Assessment Report (AR6 WGIII) assesses hundreds to thousands of future emissions scenarios. A key task in WGIII is to assess the global mean temperature outcomes of these scenarios in a consistent manner, given the challenge that the emissions scenarios from different integrated assessment models (IAMs) come with different sectoral and gas-to-gas coverage and cannot all be assessed consistently by complex Earth system models. In this work, we describe the “climate-assessment” workflow and its methods, including infilling of missing emissions and emissions harmonisation as applied to 1202 mitigation scenarios in AR6 WGIII. We evaluate the global mean temperature projections and effective radiative forcing (ERF) characteristics of climate emulators FaIRv1.6.2 and MAGICCv7.5.3 and use the CICERO simple climate model (CICERO-SCM) for sensitivity analysis. We discuss the implied overshoot severity of the mitigation pathways using overshoot degree years and look at emissions and temperature characteristics of scenarios compatible with one possible interpretation of the Paris Agreement. We find that the lowest class of emissions scenarios that limit global warming to “1.5 ∘C (with a probability of greater than 50 %) with no or limited overshoot” includes 97 scenarios for MAGICCv7.5.3 and 203 for FaIRv1.6.2. For the MAGICCv7.5.3 results, “limited overshoot” typically implies exceedance of median temperature projections of up to about 0.1 ∘C for up to a few decades before returning to below 1.5 ∘C by or before the year 2100. For more than half of the scenarios in this category that comply with three criteria for being “Paris-compatible”, including net-zero or net-negative greenhouse gas (GHG) emissions, median temperatures decline by about 0.3–0.4 ∘C after peaking at 1.5–1.6 ∘C in 2035–2055. We compare the methods applied in AR6 with the methods used for SR1.5 and discuss their implications. This article also introduces a “climate-assessment” Python package which allows for fully reproducing the IPCC AR6 WGIII temperature assessment. This work provides a community tool for assessing the temperature outcomes of emissions pathways and provides a basis for further work such as extending the workflow to include downscaling of climate characteristics to a regional level and calculating impacts.
Current technological improvements are yet to put the world on track to net-zero, which will require the uptake of transformative low-carbon innovations to supplement mitigation efforts. However, the role of such innovations is not yet fully understood; some of these ‘miracles’ are considered indispensable to Paris Agreement-compliant mitigation, but their limitations, availability, and potential remain a source of debate. We evaluate such potentially game-changing innovations from the experts' perspective, aiming to support the design of realistic decarbonisation scenarios and better-informed net-zero policy strategies. In a worldwide survey, 260 climate and energy experts assessed transformative innovations against their mitigation potential, at-scale availability and/or widescale adoption, and risk of delayed diffusion. Hierarchical clustering and multi-criteria decision-making revealed differences in perceptions of core technological innovations, with next-generation energy storage, alternative building materials, iron-ore electrolysis, and hydrogen in steelmaking emerging as top priorities. Instead, technologies highly represented in well-below-2°C scenarios seemingly feature considerable and impactful delays, hinting at the need to re-evaluate their role in future pathways. Experts' assessments appear to converge more on the potential role of other disruptive innovations, including lifestyle shifts and alternative economic models, indicating the importance of scenarios including non-technological and demand-side innovations. To provide insights for expert elicitation processes, we finally note caveats related to the level of representativeness among the 260 engaged experts, the level of their expertise that may have varied across the examined innovations, and the potential for subjective interpretation to which the employed linguistic scales may be prone to.
In a new paper in Nature Energy, Odenweller et al. use uncertainty analysis to derive a probabilistic feasibility space for green hydrogen supply. Their analysis shows 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.