Oliver Broad

Carbon dioxide removal is expected to play a crucial role in counterbalancing residual emissions and limiting temperature rise in line with Paris Agreement targets. Durable temperature stabilisation requires fossil CO2 emissions to be balanced by geological timescale storage – a condition defined as geological net zero (GNZ). Replicable for other countries, our analysis uses the UK as a case study, assessing how different GNZ implementations reshapes energy system pathways and mitigation strategies under strict, progressive, and cumulative policy formulations. We find that GNZ could be reached as early as 2040, delivering lower emission pathways than current carbon budgets prescribe, with savings of 0.9-2.34 GtCO2e between 2030-2050. These outcomes are challenging, vulnerable to disruptions in technology and feedstock supply-chains, and subject to the pace of emissions’ reductions and removals uptake. Yet they reflect earth system emissions accounting principles required to meet stated climate targets, and as such merit increased policy scrutiny.

Carbon dioxide removal (CDR) will be required to support rapid emission reductions and reach net zero emissions. Recent studies have highlighted different global warming impacts of CDR options depending on the durability of their carbon storage. Geological net zero, which demands that residual fossil CO2 emissions are matched by permanent geological storage of CO2, has been identified as one potential policy approach to address these durability differences, as it recognizes the warming risk of delayed CO2 release from less permanent storage. Considering the UK as a national case study, we investigate the effect a geological net zero policy may have on national climate change mitigation strategies. Using the national-scale energy system model UK TIMES, we explore different ways of implementing a geological net zero policy: a strict implementation applied on an annual accounting basis from 2030 forward, a progressive implementation that introduces a more gradual “share” of fossil emissions covered under the policy, and a cumulative implementation to 2050 which allows emissions earlier in the time horizon to be compensated for later. Our initial results suggest extreme difficulty in achieving GNZ, highlighting that the UK is unlikely to be able to able to reach geological net zero before 2040, as more than one decade is required to decarbonize the emitting sectors and significantly scale up removal methods with permanent storage. It is also clear that the speed of change required to achieve even this outcome is significant, requiring rapid and deep phase out of fossil fuel use much earlier than traditional scenarios suggest. We find, however, that progressive and cumulative GNZ implementations can get much closer to solving, and offer more ambitious pathways that significantly reduce the UK's cumulative emissions to 2050 compared to the current UK pathways and emissions targets. We quantify residual emissions and determine the sectors with the highest challenges for full decarbonization and find that the availability of key resource biomass as well as the pace of scaling up carbon capture and storage infrastructure have crucial impact on the feasibility of any geological net zero policy.To our knowledge, this study is the first to assess potential geological net zero policies at national level, providing insights into the opportunities and challenges of faster decarbonization and dependence on geological carbon storage in all sectors of the UK economy. Findings of this study are also relevant for other nations considering more ambitious climate change mitigation policy.

As the UK makes steps to reduce its greenhouse gas emissions to net zero, electric heat pumps are proposed as a solution for heat decarbonisation in the majority of homes. This paper used smart meter data to examine the gas and electricity consumption of 187 homes with air source heat pumps installed under the Green Homes Grant incentive scheme. It was found that 1 year after the installation, 24% of households were still connected to the gas distribution network and that 21% of households still used gas, either for cooking or for heating. We reflect on the implications of this ongoing gas connection and use in the light of the UK’s net zero plans, and discuss how households could be supported by government to fully transition away from using natural gas. Practical application: This paper found that around a quarter of households in a sample of UK homes were still connected to the gas network 1 year after installing a heat pump, with most of these still using gas for cooking or heating. It raises important questions about why a minority of households continue to use gas and whether heat pumps may not meet their needs; makes proposals for practical amendments to encourage electric cooking or incorporate gas disconnection as part of current retrofit policies; and situates the findings within the wider context of meeting the UK’s net-zero targets.

Demand-side energy reductions have so far received less policy support than supply-side net-zero technologies. Here we undertake a demand-focused process for energy scenario analysis, led by policymakers and evaluated through public dialogue. We codesign, describe and model four societal futures that aim to achieve the UK’s 2050 net-zero target. The uniquely close involvement of policymakers leading the project generates markedly different narratives that reflect policymakers’ concerns while still leading to scenarios with reductions in energy demand of 18–45%—exceeding what policies normally suggest. By 2050, technology-focused systems cost 20–100% more than lower-demand ones. While intensive cocreation requires more complex interactions compared with academic-led research, it provides space for important, and otherwise absent, energy demand conversations. This work demonstrates how engaging policymakers to colead energy scenarios can challenge conventional policy assumptions on energy demand while offering an approach to support global climate mitigation efforts.

In recent years, global studies have attempted to understand the contribution that energy demand reduction could make to climate mitigation efforts. Here we develop a bottom-up, whole-system framework that comprehensively estimates the potential for energy demand reduction at a country level. Replicable for other countries, our framework is applied to the case of the United Kingdom where we find that reductions in energy demand of 52% by 2050 compared with 2020 levels are possible without compromising on citizens’ quality of life. This translates to annual energy demands of 40 GJ per person, compared with the current Organisation for Economic Co-operation and Development average of 116 GJ and the global average of 55 GJ. Our findings show that energy demand reduction can reduce reliance on high-risk carbon dioxide removal technologies, has moderate investment requirements and allows space for ratcheting up climate ambition. We conclude that national climate policy should increasingly develop and integrate energy demand reduction measures.

Energy Demand Reduction (EDR) refers to lowering the amount of energy required to provide energy services across mobility, shelter, nutrition or the production of goods and services, among others, with the goal of reducing greenhouse gas emissions. In recent years, global studies have attempted to understand the contribution EDR could make to climate mitigation efforts. Whilst these studies are important to build a global picture, climate targets and policy are necessarily devised at the national level. To address this disconnect, we develop a bottom-up, whole system framework that comprehensively estimates the potential for energy demand reduction at a country level. Replicable for other countries, our framework is applied to the case of the UK where we find that reductions in energy demand of 52% by 2050 compared with 2020 levels are possible without compromising on citizens’ quality of life. This translates to annual energy demands of 40GJ per person, compared to the current OECD average of 55GJ. Our findings show that EDR can reduce reliance on high-risk carbon dioxide removals, moderate investment requirements, and allow space for ratcheting up climate ambition. We conclude that national climate policy should increasingly develop and integrate EDR measures to both articulate national ambition and feeding into international pledges through Nationally Determined Contributions.

Ethiopia is a low-income country, with low electricity access (45%) and an inefficient power transmission network. The government aims to achieve universal access and become an electricity exporter in the region by 2025. This study provides an invaluable perspective on different aspects of Ethiopia’s energy transition, focusing on achieving universal access and covering the country’s electricity needs during 2015–2065. We co-developed and investigated three scenarios to examine the policy and technology levels available to the government to meet their national priorities. To conduct this analysis, we soft-linked OnSSET, a modelling tool used for geospatial analysis, with OSeMOSYS, a cost-optimization modelling tool used for medium to long-run energy planning. Our results show that the country needs to diversify its power generation system to achieve universal access and cover its future electricity needs by increasing its overall carbon dioxide emissions and fully exploit hydropower. With the aim of achieving universal access by 2025, the newly electrified population is supplied primarily by the grid (65%), followed by stand-alone (32%) technologies. Similarly, until 2065, most of the electrified people by 2025 will continue to be grid-connected (99%). The country’s exports will increase to 17 TWh by 2065, up from 832 GWh in 2015, leading to a cumulative rise in electricity export revenues of 184 billion USD.