Can we reliably assess climate mitigation options for air traffic scenarios despite large uncertainties in atmospheric processes?

Air traffic has an increasing influence on climate; therefore identifying mitigation options to reduce the climate impact of aviation becomes more and more important. Aviation influences climate through several climate agents, which show different dependencies on the magnitude and location of emission and the spatial and temporal impacts. Even counteracting effects can occur. Therefore, it is important to analyse all effects with high accuracy to identify mitigation potentials. However, the uncertainties in calculating the climate impact of aviation are partly large (up to a factor of about 2). In this study, we present a methodology, based on a Monte Carlo simulation of an updated non-linear climate-chemistry response model AirClim, to integrate above mentioned uncertainties in the climate assessment of mitigation options. Since mitigation options often represent small changes in emissions, we concentrate on a more generalised approach and use exemplarily different normalised global air traffic inventories to test the methodology. These inventories are identical in total emissions but differ in the spatial emission distribution. We show that using the Monte Carlo simulation and analysing relative differences between scenarios lead to a reliable assessment of mitigation potentials. In a use case we show that the presented methodology can be used to analyse even small differences between scenarios with mean flight altitude variations.     

Mathematical properties and constraints representation for bottom-up approaches to the evaluation of GHG mitigation policies

Bottom-up models, including MARKAL, MESSAGE and AIM, are widely used when analyzing the effect of greenhouse gas (GHG) abatement policies. These bottom-up models are mostly formulated as a linear programming (LP) optimization model to find both the minimal cost combination of abatement technologies and energy flows while satisfying demands. It is not unusual that the bottom-up modeling involves a great number of technical, industrial, socioeconomic and environmental constraints. Investigating representative constraints needed for analyzing GHG abatement policies, this study proposes how to implement these constraints in bottom-up modeling.     

Forecasting the impacts of climate change on inland waterways

Inland waterways are vulnerable to climate change as river navigation depends on water levels. Droughts can severely disrupt inland navigation services by reducing water levels either to completely non-navigable ones or to levels that oblige operators to reduce vessel load. We analyse the impacts of droughts induced by climate change using projections of river discharge data provided by eleven different climate model runs. We consider location specific characteristics by focusing the analysis on four specific locations of the Rhine and the Danube where a substantial part of the total freight activity in the European Union (EU) takes place. For the majority of the cases and scenarios considered, a decrease of the number of low water level days is projected, leading to fewer drought related disruptions in the operation of the inland waterway transport system. Although the uncertainties from the climate projections should not be neglected, the navigation sector could benefit from global warming which means that European inland waterways might be one of the few sectors where climate change can have negligible, or even positive, impact. The average economic benefit, for the cases considered, from the decrease of low water levels by the end of the century is projected to be almost €8million annually.     

Modal-split effects of climate change: The effect of low water levels on the competitive position of inland waterway transport in the river Rhine area

Future climate change is expected to affect inland waterway transport in most main natural waterways in Europe. For the river Rhine it is expected that, in summer, more and longer periods with low water levels will occur. In periods of low water levels inland waterway vessels have to reduce their load factors and, as a result, transport prices per tonne will increase. One possible consequence of these higher transport prices is a deterioration of the competitive position of inland waterway transport compared with rail and road transport, and thus a change in modal split. We study this issue using a GIS-based software model called NODUS which provides a tool for the detailed analysis of freight transportation over extensive multimodal networks. We assess the effect of low water levels on the costs of transport operations for inland waterway transport in North West Europe under several climate scenarios. It turns out, that the effect on the modal split is limited. Under the most extreme climate scenario, inland waterway transport would lose about 5.4% of the quantity that is currently being transported annually in the part of the European inland waterway transport market considered. The very dry year of 2003 can be seen as an analogue for this scenario.     

The future tourism mobility of the world population: Emission growth versus climate policy

Much of global passenger transport is linked to tourism. The sector is therefore of interest in studying global mobility trends and transport-related emissions. In 2005, tourism was responsible for around 5% of all CO₂ emissions, of which 75% were caused by passenger transport. Given the rapid growth in tourism, with 1.6 billion international tourist arrivals predicted by 2020 (up from 903 million in 2007), it is clear that the sector will contribute to rapidly growing emission levels, and increasingly interfere with global climate policy. This is especially true under climate stabilisation and “avoiding dangerous climate change” objectives, implying global emission reductions in the order of −50% to −80% by 2050, compared to 2000. Based on three backcasting scenarios, and using techniques integrating quantitative and qualitative elements, this paper discusses the options for emission reductions in the tourism sector and the consequences of mitigation for global tourism-related mobility by 2050. It ends with a discussion of the policy implications of the results.     

Bacterial production and microbial food web structure in a large arctic river and the coastal Arctic Ocean

Globally significant quantities of organic carbon are stored in northern permafrost soils, but little is known about how this carbon is processed by microbial communities once it enters rivers and is transported to the coastal Arctic Ocean. As part of the Arctic River-Delta Experiment (ARDEX), we measured environmental and microbiological variables along a 300 km transect in the Mackenzie River and coastal Beaufort Sea, in July–August 2004. Surface bacterial concentrations averaged 6.7 × 10⁵ cells mL^− 1 with no significant differences between sampling zones. Picocyanobacteria were abundant in the river, and mostly observed as cell colonies. Their concentrations in the surface waters decreased across the salinity gradient, dropping from 51,000 (river) to 30 (sea) cells mL^− 1. There were accompanying shifts in protist community structure, from diatoms, cryptophytes, heterotrophic protists and chrysophytes in the river, to dinoflagellates, prymnesiophytes, chrysophytes, prasinophytes, diatoms and heterotrophic protists in the Beaufort Sea.Size-fractionated bacterial production, as measured by ³H–leucine uptake, varied from 76 to 416 ng C L^− 1 h^− 1. The contribution of particle-attached bacteria (> 3 µm fraction) to total bacterial production decreased from > 90% at the Mackenzie River stations to < 20% at an offshore marine site, and the relative importance of this particle-based fraction was inversely correlated with salinity and positively correlated with particulate organic carbon concentrations. Glucose enrichment experiments indicated that bacterial metabolism was carbon limited in the Mackenzie River but not in the coastal ocean. Prior exposure of water samples to full sunlight increased the biolability of dissolved organic carbon (DOC) in the Mackenzie River but decreased it in the Beaufort Sea.Estimated depth-integrated bacterial respiration rates in the Mackenzie River were higher than depth-integrated primary production rates, while at the marine stations bacterial respiration rates were near or below the integrated primary production rates. Consistent with these results, P_CO2 measurements showed surface water supersaturation in the river (mean of 146% of air equilibrium values) and subsaturation or near-saturation in the coastal sea. These results show a well-developed microbial food web in the Mackenzie River system that will likely convert tundra carbon to atmospheric CO₂ at increasing rates as the arctic climate continues to warm.     

Examining transport futures with scenario analysis and MCA

Climate change is a global problem and across the world the transport sector is finding it difficult to break projected increases in carbon dioxide (CO₂) emissions; there are very few contexts where deep reductions in transport CO₂ emissions are being made. A number of research studies are now examining the potential for future lower CO₂ emissions in the transport sector. This paper develops this work to consider some of the wider sustainability impacts (economic, social and local environmental) as well as the lower CO₂ transport impacts of different policy trajectories. Hence the central argument made is for an integrated approach to transport policy making over the longer term - incorporating scenario analysis and multi-criteria assessment (MCA) - to help assess likely progress against a range of objectives.The analysis is based on work carried out in Oxfordshire, UK. Different packages of measures are selected and two scenarios developed which satisfy lower CO₂ aspirations, one of which also provides wider positive sustainability impacts. A simulation model has been produced to help explore the strategic policy choices and tensions evident for decision-makers involved in local transport planning. The paper argues for a ‘strategic conversation’ (Van der Heijden, 1996) at the sub-regional and city level, based upon future scenario analysis and MCA, discussing the priorities for intervention. Such an approach will help us examine the scale of change and trade-offs required in moving towards sustainable transport futures.     

‘Each flight is different’: Carbon emissions of selected flights in three geographical markets

Air travel is considered the biggest individual climate sin. Avoiding flying, however, seems impossible. In this paper we argue that the flight a passenger chooses can be significant. For this purpose we compared the carbon emissions of selected flights in three geographical markets. We found tremendous differences in the environmental performance of individual flights. Furthermore, we also found that flying with the most modern aircraft or flying non-stop represents, in many cases, the least polluting option. Nevertheless, we were able to show that there are exceptions to this rule. Based on our results, we provide recommendations to the industry and for further research.     

Grand challenges for high-speed rail environmental assessment in the United States

The comprehensiveness of environmental assessments of future long-distance travel that include high-speed rail (HSR) are constrained by several methodological, institutional, and knowledge gaps that must and can be addressed. These gaps preclude a robust understanding of the changes in environmental, human health, resource, and climate change impacts that result from the implementation of HSR in the United States. The gaps are also inimical to an understanding of how HSR can be positioned for 21st century sustainability goals. Through a synthesis of environmental studies, the gaps are grouped into five overarching grand challenges. They include a spatial incompatibility between HSR and other long-distance modes that is often ignored, an environmental review process that obviates modal alternatives, siloed interest in particular environmental impacts, a dearth of data on future vehicle and energy sources, and a poor understanding of secondary impacts, particularly in land use. Recommendations are developed for institutional investment in multimodal research, knowledge and method building around several topics. Ultimately, the environmental assessment of HSR should be integrated in assessments that seek to understand the complementary and competitive configurations of transportation services, as well as future accessibility.     

Climate change modeling and the weather-related road accidents in Canada

The objective of this research is to study the impact of climate change on the hazardous weather-related road accidents in the New Brunswick, Canada. We develop an Exposure to Weather-Accident Severity (EWAS) index multiplying accident and weather severity. The Negative Binomial Regression and Poisson regression models are applied to estimate the spatial–temporal relationship between the EWAS index and weather-related explanatory variables of road accidents. The regression results show that the surface-weather condition, weather, driver’s gender, weather-driver’s age, weather-driver’s experience, and weather-vehicle’s age have strong positive correlation with the EWAS index, while the surface-road alignment and surface-road characteristics have negative relationship with the EWAS index. The climate change model also indicates that the number of accidents declines during snowy and freezing days—most people stay at home and those who travel extra cautious—accidents do occur. The study suggests that the Road Safety Strategy 2015 of the Transport Canada should take a holistic approach to help minimize the incidences of severe road accident during the normal as well as hazardous weather conditions.