An inter-model assessment of the role of direct air capture in deep mitigation pathways

The feasibility of large-scale biological CO2 removal to achieve stringent climate targets remains unclear. Direct Air Carbon Capture and Storage (DACCS) offers an alternative negative emissions technology (NET) option. Here we conduct the first inter-model comparison on the role of DACCS in 1.5 and 2°C scenarios, under a variety of techno-economic assumptions. Deploying DACCS significantly reduces mitigation costs, and it complements rather than substitutes other NETs. The key factor limiting DACCS deployment is the rate at which it can be scaled up. Our scenarios’ average DACCS scale-up rates of 1.5 GtCO2/yr would require considerable sorbent production and up to 300 EJ/yr of energy input by 2100. The risk of assuming that DACCS can be deployed at scale, and finding it to be subsequently unavailable, leads to a global temperature overshoot of up to 0.8°C. DACCS should therefore be developed and deployed alongside, rather than instead of, other mitigation options

Technologies for the global energy transition

The availability of reliable, affordable and mature technologies is at the basis of an effective decarbonization strategy, that should be in turn supported by timely and accurate policies. Due to the large differences across sectors and countries, there is no silver bullet to support decarbonization, but a combination of multiple technologies will be required to reach the challenging goal of decarbonizing the energy sector. This chapter presents a focus on the current technological solutions that are available in four main sectors: power generation, industry, transport and buildings. The aim of this work is to highlight the main strengths and weaknesses of the current technologies, to help the reader in understanding which are the main opportunities and challenges related to the development and deployment of each of them, as well as their potential contribution to the decarbonization targets. The chapter also provides strategies and policy recommendations from a technology point of view on how to decarbonize the global energy systems by mid-century and of the necessity to take a systems approach

The co-evolution of technological promises, modelling, policies and climate change targets

The nature and framing of climate targets in international politics has changed substantially since their early expressions in the 1980s. Here, we describe their evolution in five phases-from 'climate stabilization' to specific 'temperature outcomes'-co-evolving with wider climate politics and policy, modelling methods and scenarios, and technological promises (from nuclear power to carbon removal). We argue that this co-evolution has enabled policy prevarication, leaving mitigation poorly delivered, yet the technological promises often remain buried in the models used to inform policy. We conclude with a call to recognise and break this pattern to unleash more effective and just climate policy. This Perspective maps the history of climate targets and shows how the international goal of avoiding dangerous climate change has been reinterpreted in the light of new modelling methods and technological promises, ultimately enabling policy prevarication and limiting mitigation

Clash of Geofutures and the Remaking of Planetary Order: Faultlines underlying Conflicts over Geoengineering Governance

Climate engineering (geoengineering) is rising up the global policy agenda, partly because international divisions pose deep challenges to collective climate mitigation. However, geoengineering is similarly subject to clashing interests, knowledge‐traditions and geopolitics. Modelling and technical assessments of geoengineering are facilitated by assumptions of a single global planner (or some as yet unspecified rational governance), but the practicality of international governance remains mostly speculative. Using evidence gathered from state delegates, climate activists and modellers, we reveal three underlying and clashing ‘geofutures’: an idealised understanding of governable geoengineering that abstracts from technical and political realities; a situated understanding of geoengineering emphasising power hierarchies in world order; and a pragmatist precautionary understanding emerging in spaces of negotiation such as UN Environment Assembly (UNEA). Set in the wider historical context of climate politics, the failure to agree even to a study of geoengineering at UNEA indicates underlying obstacles to global rules and institutions for geoengineering posed by divergent interests and underlying epistemic and political differences. Technology assessments should recognise that geoengineering will not be exempt from international fractures; that deployment of geoengineering through imposition is a serious risk; and that contestations over geofutures pertain, not only to climate policy, but also the future of planetary order

Equity in allocating carbon dioxide removal quotas

The first nationally determined contributions to the Paris Agreement include no mention of the carbon dioxide removal (CDR) necessary to reach the Paris targets, leaving open the question of how and by whom CDR will be delivered. Drawing on existing equity frameworks, we allocate CDR quotas globally according to Responsibility, Capability and Equality principles. These quotas are then assessed in the European Union context by accounting for domestic national capacity of a portfolio of CDR options, including bioenergy with carbon capture and storage, reforestation and direct air capture. We find that quotas vary greatly across principles, from 33 to 325 GtCO2 allocated to the European Union, and, due to biophysical limits, only a handful of countries could meet their quotas acting individually. These results support strengthening cross-border cooperation while highlighting the need to urgently deploy CDR options to mitigate the risk of failing to meet the climate targets equitably