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While air transport decarbonization is theoretically feasible, less attention has been paid to the complexity incurred in various 'transition barriers' that act as roadblocks to net-zero goals. A total of 40 barriers related to mitigation, management, technology and fuel transition, finance, and governance are identified. As these make decarbonization uncertain, the paper analyzes air transport system's growth, revenue, and profitability. Over the period 1978-2022, global aviation has generated marginal profits of US$20200.94 per passenger, or US$202082 billion in total. Low profitability makes it unlikely that the sector can finance the fuel transition cost, at US $0.5-2.1 trillion (Dray et al. 2022). Four radical policy scenarios for air transport futures are developed. All are characterized by "limitations", such as CO2 taxes, a carbon budget, alternative fuel obligations, or available capacity. Scenario runs suggest that all policy scenarios will more reliably lead to net-zero than the continued volume growth model pursued by airlines.

Much recent research on climate change mitigation has focused on carbon intensities, i.e. emissions per unit of economic value, to better understand interrelationships of decarbonization with value. This paper studies large tourism enterprises, which account for a large share of tourism's emissions. Based on annual reports, the paper evaluates greenhouse gas emission and revenue interrelationships for a total of n = 29 large tourism companies including airlines, cruise lines and accommodation businesses. Together, these companies represent about 13% (365 Mt CO2) of global tourism emissions, generating revenues of US$477 billion (in 2019). The paper tracks their total emissions and emission intensities over the period 2015–2019, revealing that large tourism firms are not on track to net-zero. Results show considerable differences in emission intensities between the three tourism subsectors and between individual firms within the subsectors. These findings are discussed against emission reduction needs to mid-century. There is strong evidence that continued growth at industry's expected rates represents an insurmountable barrier to net-zero, contradicting industry narratives of progressively and successfully engaging with climate change mitigation.

There is a consensus that the global tourism system needs to undergo decarbonization and achieve net-zero emissions by mid-century. However, given the anticipated growth in the most energy-intensive subsector of tourism, air transport, achieving this goal seems unlikely. This paper focuses on the role of distance in the global geography of tourism, against evidence that National Marketing Organizations (NTOs) often seek to attract visitors from all over the world. The analysis of data for a sample of 12 NTOs in Europe, the USA and Canada reveals that the number of markets targeted varies between six and 33, with significant differences in the average distance to markets (<4,000 to 8,000 km), as well as emissions per arrival by market (0.2 t CO2 to 2.5 t CO2). For the countries studied, the 17% of the most distant arrivals cause 62% of the emissions. Results also show that more distant markets are more sensitive to disruptions such as COVID-19. These findings have relevance for destination marketing that point to new climate change related roles for NTOs such as rebranding, demarketing, market segmentation, and communication.

Air transport is energy-intense, and considerable attention has been paid to the sector's use of fuel and emissions of greenhouse gases. Commercial aviation is believed to currently emit about 1 Gt CO2 per year, if considering global bunker fuel use (scope 1 in the Greenhouse Gas Protocol). A growing database is becoming available on scope 1-3 emissions; this is, including up- and downstream emissions, and it is now possible to assess the aviation system's carbon intensity more comprehensively. This paper investigates the annual reports of 26 of the largest airlines in the world by market capitalisation, finding that reporting on emissions for scopes 1-3 is still inconsistent and characterised by reporting gaps. Yet, available data suggests that scope 3 emissions are significant (about 30% of scope 1 emissions). These findings have repercussions for the sector's net-zero ambitions, climate governance, consumer choices and air transport finance, as the overall contribution from air travel to climate change remains underestimated. Results suggest that it is in the sector's interest to present robust, transparent, consistent and accurate emission inventories - and to engage with the implications.

Much evidence suggests that the wealthiest individuals contribute disproportionally to climate change. Here we study the implications of a continued growth in the number of millionaires for emissions, and its impact on the depletion of the remaining carbon budget to limit global warming to 1.5 °C (about 400 Gt CO2). To this end, we present a model that extrapolates observed growth in millionaire numbers (1990–2020) and associated changes in emissions to 2050. Our findings suggest that the share of US$2020-millionaires in the world population will grow from 0.7% today to 3.3% in 2050, and cause accumulated emissions of 286 Gt CO2. This is equivalent to 72% of the remaining carbon budget, and significantly reduces the chance of stabilizing climate change at 1.5 °C. Continued growth in emissions at the top makes a low-carbon transition less likely, as the acceleration of energy consumption by the wealthiest is likely beyond the system's capacity to decarbonize. To this end, we question whether policy designs such as progressive taxes targeting the high emitters will be sufficient.

Parking fees and fines represent contested issues in cities, as they conflict with vehicle owners' opinion over 'rights' to public space. As cities have moved to regulate vehicle density by introducing parking fees, a share of drivers may feel compelled to 'cheat', weighing the price of parking fees against the cost of fines, or to simply park illegally outside designated areas. To better understand these interrelationships, this paper considers negotiations of public space as an economic gamble that can be assessed on the basis of parking violations. The study is situated in Freiburg, Germany, and relies on a mixed-methods approach that investigates the views of the regulatory agency and its enforcement officers, as well as registered parking violations (n = 181,735, in 2019). Time-spatial probabilities of being fined when parking illegally are calculated as risks, defined as detection probability per "hexagon-hour", an indicator integrating space and time. Results confirm that in the inner city, it is economically rational not to pay parking fees during 86.1% of hexagon-hours, and in surrounding areas during 99.9% of the time. Findings confirm that urban space can be negotiated in an equilibrium of fees, fines and controls. To make vehicle ownership and use less attractive, the price of parking needs to be high. Fines need to be high in relation to fees, and control densities need to constitute significant detection risks.

Traffic safety is high on the agenda of European governments. Yet, countries including Germany maintain policies that are commonly identified as increasing traffic risks, such as speed limits set too high or trends of greater car motorization and mass. To better understand some of the interrelationships of driver characteristics and car segments, this paper identifies different groups of drivers, based on a representative sample of German automobilists (n = 1211). Psychological instruments used to identify driver segments include the Driver Behavior Questionnaire (DBQ), the Multidimensional Driving Style Inventory (MDSI), and the HEXACO Personality Inventory. Based on k-means clustering, we identified four distinct groups: Risky drivers, Showy anxious-aggressive drivers, Anxious drivers and Calm drivers. Questions focused on socio-demographics, political orientation, and traffic laws are used to describe these psychographic segments. Findings suggest that Risky and Showy anxious-aggressive drivers represent a greater threat to traffic safety than other driver segments for different reasons: they drive more powerful and larger cars, deliberately violate traffic laws – creating unsafe traffic conditions for others –, and oppose legislation making traffic safer, while also voting for parties holding on to the status quo. As their political choices appear dominated by automobile interests, there are widespread implications for society.

Traffic safety is high on the agenda of European governments. Yet, countries including Germany maintain policies that are commonly identified as increasing traffic risks, such as speed limits set too high or trends of greater car motorization and mass. To better understand some of the interrelationships of driver characteristics and car segments, this paper identifies different groups of drivers, based on a representative sample of German automobilists (n = 1211). Psychological instruments used to identify driver segments include the Driver Behavior Questionnaire (DBQ), the Multidimensional Driving Style Inventory (MDSI), and the HEXACO Personality Inventory. Based on k-means clustering, we identified four distinct groups: Risky drivers, Showy anxious aggressive drivers, Anxious drivers and Calm drivers. Questions focused on sociodemographics, political orientation, and traffic laws are used to describe these psychographic segments. Findings suggest that Risky and Showy anxious-aggressive drivers represent a greater threat to traffic safety than other driver segments for different reasons: they drive more powerful and larger cars, deliberately violate traffic laws - creating unsafe traffic conditions for others -, and oppose legislation making traffic safer, while also voting for parties holding on to the status quo. As their political choices appear dominated by automobile interests, there are widespread implications for society.

[EN] Teaching sustainability presents challenges due to the inherent complexity and required behavioral change. A special pedagogical approach is needed. In this paper, we focus on the research question how students' awareness of sustainability issues can be improved significantly in a brief workshop. The presented workshop let the students autonomously addressing problems and possible solutions in small groups – with no patented recipes given, nor any "finger-pointing" from the outside. The educational basis for this workshop is the concept of discovery learning in combination with sketchnoting. This is especially appropriate to present acquired knowledge in a compact and meaningful way, to show relationships and allow schemas to be developed by the participants. This paper also describes the workshop results from several executions and the lessons learned.

Shipping is associated with various environmental impacts, such as pollutants discharged to air and sea. Much of this pollution appears to be unregulated, and global emissions from shipping are expected to more than triple between 2020 and 2050. This paper reviews global, national, regional and port-level legislative approaches that have been implemented to reduce emissions of carbon dioxide (CO2), nitrous oxides (NOx), sulphur oxides (SOx) and particulate matter (PM). Policies are identified on the basis of a systematic review of the literature in combination with a detailed analysis of the respective global, national and local policy initiatives. Findings suggest that many policies are voluntary or, in ports, incentive-based; regulatory approaches are largely limited to Emission Control Areas. Policies also focus on efficiencies, they are not concerned with absolute pollutant and greenhouse gas levels. No policies incentivizing or forcing the transition to zero-carbon fuels were identified. As ports can define limits to pollution, for instance by demanding shore power use, they can significantly affect the clean development of the sector. Further legislation will be needed nationally to counterbalance the lack of supranational ambition on pollutants and climate change mitigation.

The COVID-19 pandemic has led to an unprecedented decline in global air transport and associated reduction in CO2 emissions. The International Civil Aviation Organization (ICAO) reacted by weakening its own CO2-offsetting rules. Here we investigate whether the pandemic can be an opportunity to bring the sector on a reliable low-carbon trajectory, with a starting point in the observed reduction in air transport demand. We model a COVID-19 recovery based on a feed-in quota for non-biogenic synthetic fuels that will decarbonize fuels by 2050, as well as a carbon price to account for negative externalities and as an incentive to increase fuel efficiency. Results suggest that until 2050, air transport demand will continue to grow, albeit slower than in ICAO's recovery scenarios, exceeding 2018 demand by 3.7-10.3 trillion RPK. Results show that synthetic fuels, produced by 14-20 EJ of photovoltaic energy, would make it possible to completely phase out fossil fuels and to avoid emissions of up to 26.5 Gt CO2 over the period 2022-2050.