Greenhouse gas emissions projections: phase 1 and phase 2 modelling results

2. Introduction

2.1 Background

The Climate Change Act 2019 set ambitious targets that would require Scotland to achieve a 75% reduction in greenhouse gas (GHG) emissions^[4] by 2030 and net zero GHG emissions by 2045. In the Climate Change Plan Update (CCPu), published in December 2020, the Scottish Government described the actions that it proposes to take in order to help ensure that these targets are met.

The CCPu presented "emissions envelopes", which reflect the decarbonisation pathway that each sector would need to achieve in order for the economy as a whole to be on track to reach net zero. The sectoral envelopes collectively add up to the total annual emissions reductions that are required. For each sector in the CCPu, the Scottish Government then defined a range of outcomes which, if achieved, are intended to enable each sector to meet the emissions envelopes. Each outcome is supported by a set of policies that the Scottish Government is proposing to help deliver GHG emissions reductions.

The difference between policies and outcomes is illustrated in Box 1 below.

Box 1: Policies (Phase 1) vs Outcomes (Phase 2) of the CCPu

The Policies of the CCPu are the specific measures the Scottish Government intend to take to reduce GHG emissions. The Outcomes of the CCPu are essentially targets or overarching ambitions that the Scottish Government hopes to achieve.

The Policies are designed with the intention of supporting the achievement of the Outcomes, as shown below. However, the Outcomes may be considered aspirational to a certain extent – as they may not yet have sufficient policy mechanisms to be achieved.

Each suite of Policies is designed to achieve an intended Outcome

Outcome 1

• Policy 1
• Policy 2
• Policy 3

Outcome 2

• Policy 1
• Policy 2
• Policy 3

Outcome 3

• Policy 1
• Policy 2
• Policy 3

The Scottish Government had previously undertaken modelling work to establish a net zero pathway for the Scottish economy, using the Scottish TIMES model, which was used to inform the CCPu. While the TIMES model has a large amount of detail on specific mitigation technologies, it was not designed to assess the impact of the individual policies. Hence a bottom-up assessment of the individual policies was needed alongside the TIMES modelling, to understand the expected contribution of these policies on Scotland's net zero target.

The aim of this research was to produce a yearly estimate of Scotland's business-as-usual or "baseline" greenhouse gas (GHG) emissions from 2019 up to the Scottish Government's targeted net zero date of 2045, and then quantify the impacts of the policies in place under a set of alternative future GHG emissions scenarios. These will be used as an evidence base for future climate change planning within the Scottish Government.

There have been two "phases" to the work, representing two main iterations of the GHG emissions modelling. Phase 1 delivered an initial set of GHG projections, estimating the impacts of the quantifiable policies in the CCPu. That analysis showed that the existing policies in the CCPu are not sufficient for all the intended Outcomes to be achieved. A second iteration of the work (Phase 2) was subsequently carried out, which allowed for further refinements to the modelling, and notably introduced higher levels of ambition for some sectors. In effect, Phase 2 explored what would happen to GHG emissions if the intended outcomes set out in the CCPu were achieved, regardless of whether there are currently enough policies to deliver them.

2.2 Scope of the work

The scope of the work was to:

• Provide projections of sources of emissions and removals of CO₂ in a business-as-usual case for each year from 2019 through to 2045.
• Quantify the impacts of policies in place by providing a set of GHG projections, considering the quantifiable policies of the CCPu.
• Base projections on a bottom-up aggregation of the following sets of information:
• Estimates of the impacts on Scottish source emissions of relevant Scottish Government policies, in particular those in the Climate Change Plan Update (CCPu);
• Estimates of the impacts on Scottish source emissions of key UK Government policies;
• Other significant underlying drivers of emissions (demographic, social, economic) where there is reliable evidence from which to infer long run trends.
• Generate estimates of the emissions reductions that result from each of the policy outcomes as set out in the CCPu and policy papers published since.

The projections are provided for Scotland as a whole and for each of the eight sectors as specified in the recent Climate Change Plan Update – Electricity, Buildings, Transport, Industry, Waste, Land Use Land Use Change and Forestry (LULUCF), Agriculture and Negative Emissions Technologies – and each of their subsectors. The investigation into the LULUCF sector took a slightly different approach to the other sectors (using a sector-specific model), and so is covered separately in Appendix 1.

The projections of emissions and removals consider a range of sensitivities to provide a central case and a reasonable high and low emissions case.