Chapter 5 is about processes of making mitigation policy choices, largely in Annex 1 countries, from the immediate post-Kyoto period up to 2008. Although there had been some debate about difficulties in reducing emissions in the pre-Kyoto period, it was during this following phase that more clarity emerged about the choices and contestations policymakers faced in practice and the institutions that shaped them. These ranged from deciding where mitigation decisions should be taken, in existing or new departments or ministries; what the overall approach should be and what types of policy should be preferred; to how reducing emissions relates to objectives in other policy areas and what to do about perceived trade-offs. The politics of making collective mitigation choices, and how those choices were influenced, started to become more tangible, whilst climate mitigation was subject to a range of politicisations in a deliberative sense.

This chapter takes the Philippines as a case to elucidate the direction and speed of electricity system transition under a vertically unbundled, competitive wholesale market model, with a focus on changes in the complementary elements of the electricity system. The study employed the analytical framework based on the grid paradigm presented in Chapter 3. The results showed that despite institutional development consistent with systems based on renewable-energy-sourced electricity (RES-E), delays in infrastructure development in high-voltage backbone and interconnection transmission grids and restrictive RES-E policy have stimulated investments in new coal power plants and deterred transitions to RES-based systems. Energy security concerns about the perceived growth of electricity demand and depletion of domestic gas fields motivated the government to use natural gas as additional generation fuel rather than balancing power. Energy oligarchs capitalised on the moratorium on new coal plants to supply ancillary services from fully depreciated coal power, investing in large-scale battery energy storage systems and gas power assets, and increasing economic gains. These factors are likely to direct the Philippines towards a natural-gas-based electricity system, combining the flexible paradigm in the RES-based system with a few clean dispatchable capacities.

This chapter presents an analysis of changes in the elements of the electricity system in Vietnam, elucidating the direction and speed of electricity system transitions under conditions of vertical bundling and underdeveloped markets. The study employs an analytical framework based on the grid paradigm presented in Chapter 3. The results showed that disorderly and abrupt electricity sector reform and underdeveloped infrastructure have impeded transitions towards renewable-energy-sourced electricity (RES-E) systems; however, the study suggests that natural gas can bridge the change in generation between coal and RES-E. Despite feed-in tariffs for RES-E and internal and external landscape changes, such as negative implications of coal power plants, the pledge to Global Coal to Clean Power Transition Statement and net-zero emissions, international credit restrictions, and high-voltage backbone transmission grids, RES-E projects are deemed less bankable owing to uncertain, abrupt, and disorderly policy intervention. Coal and gas inertia are reinforced and a fuel shift to gas will be accelerated despite national security concerns over increasing dependency on imported natural gas. Past commissions to coal and gas power will direct the electricity system towards ammonia-biomass co-firing and hydrogen power to mitigate asset stranding once these technologies become commercially available on a large scale.

Climate-related stranded assets have attracted attention owing to growing concerns over the negative impacts of decarbonisation on the value of assets of carbon-intensive industries and the economy-wide knock-on effects of massive value destruction within the fossil fuel industry. However, the propagation of climate-related transition risk to the electricity sector through both financial and non-financial networks has been under-investigated. A literature review was conducted to extract theoretical causal channels and to identify bottlenecks on the ground. In theory, the financial sector revalues the costs of capital and financial assets and employs various measures to transfer the risk. On the ground, few energy and electricity companies have stepped into the early retirement of existing capacity even though major private banks, institutional investors, and export credit agencies worldwide are changing engagement with them. Chinese state banks’ continuous financing of coal power remains a barrier to the early retirement of new capacity. Financial approaches to individual companies can change these behaviours only when they are synchronised with changes in the electricity system and when accessibility to critical minerals, metals, and technologies for flexible and dispatchable generation capacity is ensured. The research incorporates empirical evidence to update the analytical framework used.

Intermediary actors are key catalysts in accelerating sustainability transitions. Since 2019, the academic literature on intermediaries and intermediation has expanded rapidly, leading to inconsistent usage, proliferating lists of activities, and questions about their impact on transition processes. These challenges risk making the concept fuzzy and less accessible while limiting its practical relevance. This chapter provides an accessible introduction to intermediaries in sustainability transitions, followed by a historical account of the concept’s development. It then presents empirical examples of intermediaries and their activities, highlighting a key gap: the lack of an explicit theory on why intermediaries exist in transition processes. To address this, we position intermediaries alongside other actors, such as system entanglers, orchestrators, and champions. This chapter concludes by outlining future research directions, emphasizing the need to move beyond individual intermediaries to ecologies of intermediation as transitions accelerate and interact.

Olivine and low-Ca pyroxene compositional distributions show a hiatus between H and L, but not between L and LL. Because H, L, and LL chondrites show systematic changes in many characteristics, they must have formed in close proximity. H/L and L/LL chondrites may be anomalous members of one of the major OC groups or representatives of OC bodies of intermediate composition. A few highly reduced OC are either H chondrites that underwent whole-rock reduction or are members of otherwise-unsampled reduced OC bodies. IIE irons likely represent a fourth, reduced OC group. R chondrites resemble OCs but have more matrix material, higher 17O, and are much more oxidized. H, L, and LL chondrites show increasing degrees of oxidation with petrologic type. The bulk chemical and bulk isotopic compositions of OCs show systematic variations among the four principal groups. Metal-silicate fractionation was a nebular process that may have been caused in part by loss of metal from chondrules. OC oxidation state is heterogeneous on global and kilometer-size scales, and homogeneous on meter and smaller size scales. OC bulk O-isotopic composition is heterogeneous on global size scales and homogeneous on km and smaller size scales.

In the final chapter of this handbook, we reflect on the development of sustainability transitions research (STR) by examining its origins, core focus, achievements, critiques, and future directions. Using the metaphor of a tree, we argue that STR has grown from deep roots in various disciplines to develop a broad crown of research branches, all connected by a shared focus on socio-technical change. The field’s rapid expansion brings both opportunities and challenges. While a common language fosters interdisciplinary collaboration, it also risks rigidity and exclusivity, highlighting a tension between cohesion and fragmentation. Additionally, disseminating STR findings into its foundational disciplines and addressing growing political and social responsibilities remain key challenges. STR forms a robust community while requiring ongoing (self-)reflection. Rather than defining its trajectory, we aim to foster dialogue on STR’s evolution, recognizing that, like a tree, research fields need continuous nurturing to remain vital and productive.

Sustainability transitions research explores how societies transform socio-technical systems towards evolving sustainability goals. This chapter introduces key concepts, development, and significance of this interdisciplinary field. We define sustainability transitions through three core components: socio-technical systems combining technology and social structures, transition processes as multi-dimensional shifts over long timespans, and the evolving, contested nature of sustainability goals. Since its 1990s origins, the field has expanded to include diverse theoretical frameworks and methods. While established frameworks offer valuable tools, emerging research on spatial dimensions, power dynamics, and methodological diversification is crucial for addressing contemporary challenges. This chapter lays the foundation for the handbook, previewing key debates and themes explored in subsequent chapters on theoretical frameworks, transition dynamics, methodologies, and future research directions.

CAI formation began 4.567 Ga ago and ferromagnesian chondrules formed 2-2.7 Ma later. The order of OC parent-body accretion may have been (from earliest to latest) IIE, H, L, LL. Ordinary chondrites formed in the Inner Solar System along with other noncarbonaceous materials. 26Al decay was the primary asteroidal heat source. Ordinary chondrites have been modeled as being a significant component of Earth. Each OC asteroid was subject to major collisions. These are marked by peaks in cosmic-ray exposure (CRE) age distributions: for example, 45% of H chondrites have a CRE age of ~7.5 Ma. The U/Th-He ages of L chondrites are lower than those of H or LL chondrites due to the collisional breakup of the L parent body ~470 Ma ago. The lower maturity of OC asteroidal regoliths compared to lunar regolith is due to OC asteroids’ experiencing a lower micrometeorite flux, lower average projectile velocities, more-significant spallation processes, and having an ultramafic composition. Some OC are associated with abundant non-OC material; these include OC clasts in Cumberland Falls (aubrite), Almahata Sitta (anomalous ureilite), Bencubbin (CBa chondrite), Galim (EH/LL breccia), and Kaidun (carbonaceous-chondrite breccia).

Carbonaceous (CC) and noncarbonaceous (NC) materials have nonoverlapping isotopic compositional ranges. The CC groups include all carbonaceous chondrites, Eagle Station pallasites, and several groups of iron meteorites (IIC, IID, IIF, IIIF, IVB); they likely formed in the Outer Solar System. The NC groups include ordinary, enstatite and R chondrites, Howardites-Eucrites-Diogenites (HEDs), ureilites, angrites, lunar meteorites, martian meteorites, main-group pallasites, the Earth, and the remaining iron groups (IAB, IC, IIAB, IIE, IIIAB, IIIE, IVA); they probably formed in the Inner Solar System. Proto-Jupiter may have accreted rapidly and functioned as a barrier, hindering the radial drift of carbonaceous-chondrite-related materials toward the Inner Solar System, preserving the isotopic dichotomy.

Urban sustainability transitions research has grown into a prominent field since the late 2000s. This chapter traces its historical evolution, offering a concise overview of key debates, defining terms, and examining methodological implications. It explores recent discussions on actors, agency, intermediation, governance, and urban transformative capacities. Drawing on the ‘City of the Future’ project in Dresden, Germany (2015-2022), it illustrates practical applications of research. The chapter concludes with an outlook on emerging priorities and methodological innovations, advocating a shift from short-term, project-based urban research towards long-term real-world laboratories. These would serve as enduring social research infrastructures, fostering sustained partnerships among academia, policymakers, businesses, civil society, and citizens to collectively experiment with and navigate transformative urban change.

Analysing interactions between niches and regimes is critically important for understanding sustainability transitions. What complicates interaction is the fact that sustainability is often understood and pursued differently in regimes compared to niches. That means the aims and criteria for innovation can be different on either side of the interaction. A paradox arises in which interaction will be easiest when there is already good alignment between niche and regime sustainability criteria, but such alignment will by definition not demand very great changes in the regime nor empower more radical niche experiments. In practice, four different interactions coexist: differentiation; co-option; hybridisation; and criticism. These interactions work in both directions, can be interdependent upon one another, and influence wider change processes over time. It becomes problematic to conceive reconfiguration as a single transition process originating in niches and linking to regimes. This is illustrated with an example that contrasts sustainability in the automation regime of the Fourth Industrial Revolution (4IR) with a niche space that we call post-automation. In becoming attentive to niche-regime interactions, so the politics of sustainable transitions becomes clearer.

Tiny presolar grains include C polymorphs, carbides, nitrides, oxides, silicates, metallic Fe-Ni, and organic compounds. Rare CAIs and AOAs contain refractory oxides and silicates. Major phases in type-3 OC include olivine and low-Ca pyroxene with variable FeO/(FeO+MgO), metallic Fe-Ni, troilite, and nearly exclusively within chondrules, crystallites of Ca-pyroxene, rare pigeonite, and tiny grains of merrillite. Whole-rock thermal metamorphism produced secondary phases: orthopyroxene, diopside, chromite, ilmenite, rutile, phosphate, and plagioclase. Diffusion facilitated by metamorphism causes increasing compositional homogeneity in olivine and pyroxene. Some minerals and mineraloids are formed at high shock pressure. These include lingunite and maskelynite from plagioclase; ahrensite, asimowite, poirierite, ringwoodite, and wadsleyite from olivine; akimotoite, bridgmanite, hemleyite, hiroseite, and majorite from orthopyroxene; chenmingite and xieite from chromite; tuite from merrillite; wangdaodeite from ilmenite; and TiO2-II from rutile. Parent-body aqueous alteration produced phyllosilicates, Ni-rich sulfides, Ni-rich metal phases, carbides, oxides, and small calcite crystals.