Climate change: evidence review of mitigation options in the Transport sector

Evidence review of potential climate change mitigation measures in the Transport sector.

1 Introduction

1.1 Background

The Climate Change (Scotland) Act 2009 (Scottish Parliament, 2009) created a statutory framework for greenhouse gas ( GHG) reductions in Scotland by setting an interim 42 per cent reduction target for 2020 and an 80 per cent reduction target for 2050 compared to 1990. As of today Scotland is on track to meet this target, with recently published data for 2014 indicating that the 2020 interim target had been met six years ahead of schedule (Scottish Government, 2016). Section 35 of the Act placed a duty on Scottish Ministers to lay before the Scottish Parliament a Report on Proposals and Policies ( RPP), setting out specific measures for reducing GHGs to meet Scotland's statutory targets. The second Report ( RPP2) was published in June 2013 and covered the period 2013 to 2027 (Scottish Government, 2013a). The Climate Change Plan sets out proposals and policies for meeting targets to 2032.

There is increasing recognition that actions designed to reduce GHGs not only mitigate the risks of climate change but might also help or limit the achievement of other societal objectives such as improved air quality, health and energy security (Committee on Climate Change, 2016). Together, these benefits and potential adverse impacts of climate change mitigation might provide additional incentives or potentially disincentives for strong actions to reduce GHG emissions.

A more detailed understanding of such potential co-benefits and adverse side effects is an important part of the foundation underpinning the development of future Scottish Government policies. Information on the impacts of climate change mitigation across the transport sector helps improve understanding of social and economic benefits and the role these could play in helping to create a fair, equal and prosperous Scotland.

The Scottish Government therefore commissioned Aether to provide a synthesis of qualitative and quantitative evidence to indicate the direction and magnitude of the potential wider impacts of climate change mitigation actions in the transport sector, which would be relevant to the Scottish context. Where possible quantitative models and tools were identified, with impacts in terms of equalities evaluated correspondingly. This is the final report of the study.

1.2 Definitions and framing

Climate change mitigation action is typically evaluated in terms of the GHG emissions avoided per unit of expenditure, often expressed as cost per tonnes of CO2 equivalent. The GHG savings will lead to benefits arising from reduced climate change, such as lower sea level rise and less extreme weather. However, these actions usually have other impacts - both positive and negative - beyond the benefits of avoided climate change and the direct financial costs of the mitigation action. These wider impacts are referred to as co-benefits if they are positive and adverse side-effects if they are negative, sometimes jointly referred to as co-impacts. In the transport sector, for example, increased levels of walking and cycling could give rise to a range of co-benefits including the health benefits from increased physical activity and cost savings through reduced hospital admissions. However, adverse side-effects could include a potential increase in cycling related injuries as the number of people who cycle increase.

When considering the financial costs of energy consumption, it can be hard to define the boundary between direct costs or benefits and co-impacts. For example, increased efficiency in vehicles should lead to reduced fuel consumption and hence a reduction in the amount spent on fuel. These energy cost savings are widely treated as a co-benefit in the literature, but they are also often included in the cost-benefit assessments that contribute to the GHG mitigation investment decision - in other words, they are included in the calculation of the cost per tonne of CO2 avoided. It is important to avoid double-counting these benefits. However, changes in energy costs can be treated as co-impacts if they have unintended side-effects, e.g. if they fall disproportionately on particular sectors of society either increasing or decreasing social inequality.

Although most co-benefit studies refer to the wider impacts of climate change mitigation policies, as described above, some address the impacts of non-climate policies, such as air quality legislation, on greenhouse gas emissions. For example, a reduction in the use of diesel vehicles because of air quality concerns could have impacts on carbon savings. There are also studies that take a more holistic view, assessing all the impacts of a technology or policy on an equal basis, including both climate and non-climate impacts. Although some early studies defined co-benefits as 'benefits not related to the primary aim of a policy or action', it is now acknowledged that not all policies or actions have a single primary aim, and it could be better to assess all impacts within a 'multiple objective, multiple impact' framework (Ürge-Vorsatz et al., 2014). A number of papers now refer to 'multiple benefits', including GHG savings alongside other impacts, rather than co-benefits. All these different framings are addressed in this report.

This report places climate change mitigation in a sustainable development framework considering broader environmental, social and economic impacts of action. These wider impacts need to be considered alongside the cost-effectiveness and abatement potential of each mitigation option for greenhouse gas reduction so that climate targets can be met while maximising co-benefits and reducing adverse side-effects.

1.3 Research aim and objectives

The aim of this project is to improve the Scottish Government's understanding of the potential wider impacts for Scotland of climate change mitigation measures in order to support the development of the Climate Change Plan.

The objectives of this project are:

  • To produce a synthesis of qualitative evidence which indicates the direction (positive / negative) and potential magnitude of the potential wider impacts of climate change mitigation actions which would be relevant to the Scottish context.
  • To identify the most robust quantitative models and tools which would enable quantification and, where possible, monetisation of the potential wider impacts of climate change mitigation actions which would be relevant to the Scottish context.

These objectives are underpinned by the following research questions:

1) What is the evidence, both quantitative and qualitative, of potential wider impacts (co-benefits and adverse side-effects) arising from climate change mitigation actions which would be relevant to the Scottish context?

2) Based on a review and synthesis of qualitative evidence: what are the key sources of robust evidence; and what is the balance of evidence, in terms of the direction (positive / negative) and potential magnitude, of those wider impacts relevant to Scotland?

3) Based on a review and synthesis of quantitative evidence: which models and tools are assessed as the most robust to quantify and, where possible, monetise such wider impacts? What quantitative data would be required to apply these models to Scotland? What key assumptions are required?

4) From an equalities perspective, what evidence is there about the potential distribution of wider impacts relevant to Scotland across the population?

5) What are the most significant gaps in research and evidence about potential wider impacts which are relevant to Scotland?


Email: Debbie Sagar

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