13.1.1 In light of the ambitious climate change targets, managing the environmental effects that are considered likely to arise from the preferred policy option are likely to present some challenges. The proposal to introduce an overall 50% reduction in ADT is likely to lead to short-term increases in GHG emissions, relative to where they would be in the absence of the policy, even with efficiency measures in place. Medium to long-term, it is more challenging to predict the implications of any increase in emissions and the magnitude of these.
13.1.2 A number of secondary impacts were noted, and included increased pressure on local air quality and potential changes to noise exposure. This has the potential to lead to negative impacts on population and human health. Aircraft noise, through changes in flight numbers and patterns, is likely to remain a key challenge in terms of how the industry can maintain growth whilst addressing concerns on this. Increased pressure on existing infrastructure, and the potential development of new infrastructure to facilitate growth in the industry, is also considered likely to arise and this could lead to a number of environmental impacts. National level implications for a range of environmental receptors, from the effects of climate change being exacerbated through increased aviation activity, were also noted.
13.1.3 The magnitude of the identified impacts will be dependent on a number of factors, such as operational activities, technological developments, current and future mitigation, including that applied at individual airports, and the scale and location of any proposed development. The extent of any increase in passenger numbers will also influence significance, and this is likely to differ depending on how the 50% reduction in the overall tax burden is delivered.
13.2 Mitigation and Recommendations
13.2.1 A key part of the SEA process is the identification of mitigation for adverse effects and opportunities to enhance benefits. As noted early in the assessment process, the potential environmental effects likely to arise from the preferred policy option will impact at differing geographical scales. Some will be trans-boundary and experienced over a larger geographical envelope, whilst other environmental impacts are likely to be realised at a more local level.
13.2.2 There are limitations to the mitigation that can be proposed, because much of this is outwith the scope of the preferred policy option to influence. Mitigation is likely to be best placed and most effective when implemented in a way that reflects these differing geographical scales. For example, international and global mitigation measures to address the impacts of emissions, or within lower tier of plans, programmes and strategies that set out action to meet any challenging new climate change target. Furthermore, local level consideration is likely to be given at project level to any future infrastructure requirements, for example through an EIA.
13.2.3 Throughout this assessment, current and future mitigation measures have been discussed when considering the impacts identified as likely to arise within each SEA topic area. These include the agreement reached on the CORSIA at the ICAO Assembly in October 2016. Whilst the future of mitigation measures such as these and the EU ETS is uncertain, they are likely to remain key considerations to addressing global emissions.
13.2.4 Continued and future action with regards to climate change, set through a range of Scottish Government policies, proposals and strategies is also supported. This has the potential to include new and more testing targets through the current development of a new Scottish Climate Change Bill, alongside a possible shift in the overall accounting framework to one based on actual emissions.
13.2.5 Technical and operational improvements within the aviation industry to reduce GHG emissions, alongside the collaborative effects and aspirational goals agreed within industry on climate change action, are also supported. Significant improvements have been made to date and continued progress will be necessary to continue to improve efficiencies within the industry.
13.2.6 The SEA notes and supports the commitment given by the Scottish Government  to undertake further assessment work on the potential implications for noise levels that may arise through changes in air traffic movements across Scotland.
13.2.7 Airport masterplans will continue to play a key role in stakeholder engagement, providing a mechanism for airport operators to explain how they propose to take forward this strategic framework in the form of airport-specific proposals. Action taken within the industry to establish and maintain effective community engagement as airports continue to expand is supported and encouraged at all times where possible.