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Global climate action is the grand challenge of the 21st century. Large reductions in greenhouse gas emissions are needed, with net-zero CO 2 emissions by mid-century a requirement for many scenarios that restrain global warming below 1.5 °C by 2100. This will require massive deployment of renewables such as ground-based solar and wind, increased long-distance grid transmission capacity, and electrification of much of the global economy. Increased electrification, coupled with rising standards of living in developing countries, will drive ever-larger electricity demand to 2050 and beyond. And the intermittency, land-use, and transmission requirements of ground-based solar and wind present challenges to large-scale deployment to meet Net Zero targets. Space-based solar power (SSP) presents an enticing alternative, and with full reusability of upcoming heavy launch vehicles and modular SSP architectures, the economics of deployment are expected to become favorable in the coming decades. Efforts exist today to deploy demonstrators this decade, with initial production systems by 2050. However, deploying SSP at the scale required to address rising, global electricity demand will itself require orders-of-magnitude greater launch frequencies. If heavy launch frequency does not increase quickly enough, due to environmental concerns, launch site competition, or other bottlenecks, the dropping cost of launch will not be sufficient to enable SSP for global impact this century. A space elevator (SE) development program like that proposed by the International Space Elevator Consortium (ISEC) offers an alternative delivery mechanism for scaling SSP beyond 2050, hedging the risk of reliance on a single delivery system while reducing the time required for large-scale SSP deployment. To de-risk possible futures in which SSP is a major part of the global energy mix this century, a dual space access architecture is proposed, leveraging the strengths of heavy launch and SEs together. Such an architecture would secure the future for green energy on Earth, in 2050 and beyond. • Net-zero CO 2 emissions by 2050 required for many climate scenarios with < 1. 5 °C warming. • Massive deployment of renewables and scale-ups of long-distance transmission required. • Space-based solar power (SSP) is becoming economically viable as an enticing alternative. • Reusable heavy launch must scale-up rapidly to deploy SSP at scale for net-zero. • A space elevator development program would de-risk delivery of SSP at scale. [ABSTRACT FROM AUTHOR]

Efforts to enhance greenhouse gas (GHG) emission reduction in East Asia play a pivotal role on both global and regional scales in advancing climate mitigation strategies. This study aimed to better constrain anthropogenic CO 2 emission estimates by expanding the network of near-surface in-situ stations for CO 2 observations across South Korea. To achieve an optimal CO 2 network design, we conducted an Observing System Simulation Experiment (OSSE) coupled with the Stochastic Lagrangian Transport model (STILT), utilizing meteorological data from the Korean Integrated Model (KIM). Our inversion setup incorporated two CO 2 emission datasets with a 0.1o resolution: EDGAR v6 for prior emissions and GRACED for truth emissions. A uniform model-mismatch error of 3 ppm was introduced across sites. The effectiveness of the existing five in-situ stations, termed the base network, in South Korea was evaluated to gauge their ability to constrain CO 2 surface flux estimates. However, the findings revealed a reduction in flux uncertainty of only 29.2%, which fell short of the desired uncertainty reduction goal. In this base network, the Lotte World Tower (LWT: 37.5126°E, 127.1025°E) in Seoul and the Anmyeondo (AMY: 36.538576° N, 126.330071° E) site in Taean county stood as major contributors, with estimated reductions of 17.48% and 6.35%, respectively. Consequently, we proposed and developed an extended network, identifying seven candidate sites based on consideration of logistical factors, existing infrastructures, and proximity to the emission source regions. An incremental optimization scheme ranked their contributions, resulting in an additional 25% reduction, bringing the total to 54.13%. However, it is noteworthy that diminishing returns (ranging from 13% to less than 0.1%) were observed with an increase in station count mainly due to the possibility that adding a station earlier in the sequence might render subsequent stations redundant. Despite this, the proposed CO 2 network successfully reduced uncertainty in emissions, narrowing the gap with the objectives of the Global Greenhouse Gas Watch (G3W). • Designing CO 2 near-surface observation network over South Korea. • New stations selected considering logistic factors, existing infrastructures, and proximity to emission sources. • The base network was able to reduce 29.18% of the uncertainty in CO 2 emissions. • Extending network, by adding new seven candidate sites, led to a total uncertainty reduction of 54.13%. [ABSTRACT FROM AUTHOR]

The Chinese government has announced ambitious carbon reduction goals to address climate change, however, there has been limited scientific attention to the achievement of deep decarbonization in regions with insufficient economic development. Moreover, the complex impacts of climate change mitigation on energy system, environment and economic development remain unclear in Northwest China. Here we construct a comprehensive evaluation model system to evaluate the effects of different climate mitigation pathways in Qinghai, Ningxia, Gansu and Xinjiang provinces. Results show that the four provinces need to vigorously increase the share of electricity that consumed in final energy to 53.1–60.0% and 52.9–62.0% for 2 °C and 1.5 °C target, respectively, and reduce total energy demand to 11.6–44.4 Mtoe and 8.2–34.1 Mtoe in 2050. Meanwhile, the CO 2 emissions for their energy systems will reach peak by 2025 at lower values. Moreover, the synergies of CO 2 reduction are most conducive to abating SO 2 pollution and also contributing to decreasing PM 2.5 concentrations. Additionally, the GDP losses in 2050 fluctuate from 5.0 to 21.7 billion USD in the 2 °C scenario to 11.5–52.7 billion USD in the 1.5 °C scenario. Our study provides practical guidance on achieving carbon reductions in less developed regions of China and lays foundations to promote decarbonization of energy systems in other provinces. • Realizing climate goals requires low-carbon energy systems led by electricity. • Energy-related carbon emissions in Northwest China will peak by 2025. • More ambitious climate and clean air policies are needed for air quality improvement. • Economic loss shows an upward trend in the future under climate targets. [ABSTRACT FROM AUTHOR]

The depth and breadth of the climate crisis is well known, all sectors, industry, government and the individual have the potential to reduce emissions to slow or stop catastrophic climate change. To determine and evaluate the (revealed) preferences of the public in reducing their personal carbon emissions, a conjoint analysis survey, using the PAPRIKA (Potentially All Pairwise RanKings of all possible Alternatives) method, was distributed to the public in a city in the south of England (Southampton). Knowledge of the deep-seated preferences of the public makes a fundamental contribution to future climate actions because it enables publicly acceptable system change to be developed. Results showed the public were unwilling to make large-scale lifestyle changes, even if they would cause large emission reductions. There was a clear preference for making relatively easy, convenient changes to behaviour rather than making more difficult personal lifestyle changes involving diet and transportation. A significant value-action gap is evident, with the public showing high awareness of the seriousness of climate change but showing an unwillingness to make deep cuts to their personal emissions. Demography and personal factors had a relatively low influence over preferences with trends generally staying the same across demographic groups, aside from income brackets. Participants believed that reductions in emissions should come from a 'group effort' from all levels of government, business, environmental groups and individuals. Few participants placed themselves as individual drivers of carbon emission reduction. In order to reduce emissions some form of intervention needs to be made, as the public are not personally willing to make large-scale reductions in carbon emissions, regardless of their environmental awareness or demography. • Public's views on approaches to carbon reduction investigated via conjoint analysis. • Preference for low intensity, 'easy' behaviours not challenging lifestyle changes. • Demographic & personal factors have low influence on carbon reduction preferences. • High awareness of severity of climate change, impacts/priority; also high anxiety. • Desire to consume & "carry on as normal" outweighs self-reported concerns/attitudes. [ABSTRACT FROM AUTHOR]

Cities are a major source of greenhouse gas emissions (GHGs), but they can play a significant role in climate change mitigation by adopting and implementing GHG emission reduction plans, policies and measures. Circular economy measures are recognized to contribute significantly to decarbonization. However, in the literature there is a lack of quantitative analyses on circular measures in cities and their impact on urban GHG emissions. The paper aims to contribute to the literature on the relation between circular cities and climate change mitigation by focusing on circular interventions applicable in three high-impact sectors in cities: energy systems, mobility and built environment, in order to investigate their impacts in terms of emission reductions and contribution to decarbonization. The study covers four cities around the world accounting for more than 10 million of inhabitants and 2,000 km2 of metropolitan area: Bogotá, Colombia; Genoa and Milan, Italy; Glasgow, UK. The methodology uses a Global Trade Analysis Project (GTAP) modelling approach to develop production and consumption-based emission baselines for the four cities and to assess impacts of selected circular measures in the three sectors on the baselines. According to the in-depth analysis of the four considered urban contexts, the majority of the emissions generated by activities carried out within the urban borders are emitted outside the borders in the form of emissions scope 3, thus demonstrating how today's cities are large consumers of goods produced outside their borders, requiring the use of a consumption-based approach for emissions inventory. The results on the modelling of the GHG reduction impact of circular measures show that there is a relevant emission reduction potential in Scope 1 and 2 emissions in cities and highlight the need to prioritize decarbonization of electricity supply in order to ensure relevant emission reductions across the three sectors. The results also demonstrate the potential to reduce supply-chain Scope 3 emissions through urban measures. [Display omitted] • Four different urban contexts around the world are taken in account. • Three sectors are investigated: energy, mobility and built environment. • A consumption-based emission accounting method is used to assess the effective impact of cities. • Impacts of different GHG emission reduction interventions are evaluated for each city. [ABSTRACT FROM AUTHOR]

Carbon capture, utilization, and storage (CCUS) is a crucial technology for global climate mitigation. To implement large-scale CCUS, decisions about where and how to build a CO 2 transportation network are urgently required. However, previous studies are limited in proposing the economical transportation network for CCUS that considered comprehensive risks from socio-economic, geographical and geological factors. Here, we develop a pipeline layout planning model to investigate the cost-effective and reliable transportation network for CCUS. Results show that to meet the annual CO 2 emission reduction target of 654 million tons for CCUS in the coal-fired power sector under China's carbon neutral goal, pipelines with a total length of 17,589 km need to be constructed. The emission sources can be transported in pipelines with an average radius of 58 km, and with diameters of 8, 12, and 16 inches. Northeast, north, and northwest China are the main areas suitable for pipeline construction. • Northeast, North, and Northwest in China are vital areas for capture, transport, and storage. • Five large-scale pipeline network groups can be constructed in China. • Pipeline construction is greatly affected by a variety of practical factors. [ABSTRACT FROM AUTHOR]

Cities are a major source of greenhouse gas emissions (GHGs), but they can play a significant role in climate change mitigation by adopting and implementing GHG emission reduction plans, policies and measures. Circular economy measures are recognized to contribute significantly to decarbonization. However, in the literature there is a lack of quantitative analyses on circular measures in cities and their impact on urban GHG emissions. The paper aims to contribute to the literature on the relation between circular cities and climate change mitigation by focusing on circular interventions applicable in three high-impact sectors in cities: energy systems, mobility and built environment, in order to investigate their impacts in terms of emission reductions and contribution to decarbonization. The study covers four cities around the world accounting for more than 10 million of inhabitants and 2,000 km2 of metropolitan area: Bogotá, Colombia; Genoa and Milan, Italy; Glasgow, UK. The methodology uses a Global Trade Analysis Project (GTAP) modelling approach to develop production and consumption-based emission baselines for the four cities and to assess impacts of selected circular measures in the three sectors on the baselines. According to the in-depth analysis of the four considered urban contexts, the majority of the emissions generated by activities carried out within the urban borders are emitted outside the borders in the form of emissions scope 3, thus demonstrating how today's cities are large consumers of goods produced outside their borders, requiring the use of a consumption-based approach for emissions inventory. The results on the modelling of the GHG reduction impact of circular measures show that there is a relevant emission reduction potential in Scope 1 and 2 emissions in cities and highlight the need to prioritize decarbonization of electricity supply in order to ensure relevant emission reductions across the three sectors. The results also demonstrate the potential to reduce supply-chain Scope 3 emissions through urban measures. [Display omitted] • Four different urban contexts around the world are taken in account. • Three sectors are investigated: energy, mobility and built environment. • A consumption-based emission accounting method is used to assess the effective impact of cities. • Impacts of different GHG emission reduction interventions are evaluated for each city. [ABSTRACT FROM AUTHOR]

Carbon capture, utilization, and storage (CCUS) is a crucial technology for global climate mitigation. To implement large-scale CCUS, decisions about where and how to build a CO 2 transportation network are urgently required. However, previous studies are limited in proposing the economical transportation network for CCUS that considered comprehensive risks from socio-economic, geographical and geological factors. Here, we develop a pipeline layout planning model to investigate the cost-effective and reliable transportation network for CCUS. Results show that to meet the annual CO 2 emission reduction target of 654 million tons for CCUS in the coal-fired power sector under China's carbon neutral goal, pipelines with a total length of 17,589 km need to be constructed. The emission sources can be transported in pipelines with an average radius of 58 km, and with diameters of 8, 12, and 16 inches. Northeast, north, and northwest China are the main areas suitable for pipeline construction. • Northeast, North, and Northwest in China are vital areas for capture, transport, and storage. • Five large-scale pipeline network groups can be constructed in China. • Pipeline construction is greatly affected by a variety of practical factors. [ABSTRACT FROM AUTHOR]

• Distribution effect of carbon-food nexus for Chinese cities were explored. • Several methods built using the spatial decoupling index were proposed. • Chinese cities exhibited varying degrees of the distribution effect over the period. • Driver pattern of carbon-food nexus has changed over the years. Climate change mitigation and food security are sustainable development goals (SDGs) of the United Nations. Despite extensive studies focused on the nexus of different SDGs and corresponding mechanisms, the distribution effect of carbon-food nexus and its driver has received limited attention, hindering policy making for balancing pathways of regional emission reduction and food production improvement. The present study explored the distribution effect (i.e., spatial performance) of carbon-food nexus from multiple perspectives (namely, status quo, drivers, and trend) based on a unique city-level dataset from 2005 to 2017. To this end, we proposed the spatial decoupling index, the corresponding decomposition and nonparametric models for capturing the multi-perspective distribution effects. The results indicated that Chinese cities, categorized by population scale and economic structure, exhibited varying degrees of distributions of carbon-food nexus over the period. Moreover, the driver pattern of carbon-food nexus was noted to have changed, wherein investment efficiency and scale were positive drivers. Furthermore, we showed that a more developed city's economy was statistically significantly associated with higher carbon emission and lower food production. Therefore, related stakeholders should take more actions such as strengthening capital accumulation and joint management of carbon intensity, for improving the distribution effect of the overall city-level carbon-food nexus. [ABSTRACT FROM AUTHOR]

The world needs to rapidly reduce emissions of carbon dioxide (CO 2) emission to stave off the risks of disastrous climate change. In particular, decarbonizing U.S. manufacturing industries is particularly challenging due to the specific process requirements. This study estimates the potential for future CO 2 emission reductions in this important sector. The analysis is a detailed accounting exercise that relies on estimates of emission-reduction potential from other studies and applies those potentials to the manufacturing sector using a bottom-up approach. The actions are grouped into four "pillars" that support deep decarbonization of manufacturing (DDM): Energy Efficiency, Material Efficiency, Industry-Specific, and Power Grid. Based on this bottom-up approach, the analysis shows that an 86% reduction in carbon dioxide emissions from the Reference Case is feasible. No single pillar dominates DDM, although opportunities vary widely by sub-sector. The analysis shows that a strategy incorporating a broad set of elements from each pillar can be effective instead of relying on any single pillar. Some pillars, such as Energy Efficiency and Material Efficiency, have wide applicability; others have key niche roles that are Industry-Specific; the Power Grid pillar requires interaction between grid decarbonization and industry action to switch from fossil fuels to zero-carbon electricity where appropriate. [Display omitted] • Four technological strategies ("pillars") for deep decarbonization of U.S. manufacturing are investigated. • Seven energy-intensive and one non-energy-intensive industries are examined separately. • An 86% reduction in energy related CO 2 emissions is feasible in U.S. manufacturing by 2050. • No single pillar dominates implying a diversified approach to decarbonization is needed. • Some emissions remain in select industries, in particular chemicals. [ABSTRACT FROM AUTHOR]