Climate Change Plan: third report on proposals and policies 2018-2032 (RPP3)

The TIMES Whole System Energy Model

TIMES is a Whole System Energy Model ( WSEM). These models aim to capture the main characteristics of an energy system and are particularly useful for understanding the strategic choices that are required to decarbonise an economy. The Scottish TIMES model is high-level, covering the entire Scottish energy system, as well as non-energy sectors, including agriculture, Land Use, Land Use Change and Forestry, and waste. It contains many thousands of variables covering existing and future technologies, fuels and abatement measures, such as availability, cost and greenhouse gas emissions factors.

The model uses this information to identify the carbon cost-effectiveness of these technologies, fuels and other abatement

measures in order to provide a consistent comparison of the costs of action across all sectors and to develop a least-cost pathway for meeting our climate change targets. The pathway includes a set of suggested technologies, e.g. electric vehicles, fuels, such as biomass, and other carbon reduction measures, including hectares of woodland planted. TIMES also produces a set of emissions envelopes that limit emissions for each sector of Scotland's economy, in a way that is consistent with the least-cost pathway. The system-wide approach taken by the model ensures that the results are internally consistent, for example, there is a fixed amount of each resource available to the model; if more is used by one sector, then less is available to other sectors.

The pathway and envelopes suggested by the model are a guide. While the model is a powerful tool for considering the implications of changes in the energy system and non-energy sectors, it does not give a prediction of the future. Engagement with sector experts to consider the wider implications of the emissions reduction pathway has therefore been an important part of the process of developing the analysis for the Plan. The final model run underpinning the emissions envelopes presented in the Plan reflects these discussions. It should also be noted that the final envelopes are one potential option for achieving our climate change targets, and should not be considered sector targets.

Further detail on the modelling approach taken in the Plan is outlined in the accompanying Technical Annex.

A new approach

Previous reports on proposals and policies ( RPP1 and RPP2) took an alternative approach, identifying abatement associated with proposals and policies and deducting this from the business-as-usual emissions trajectory, that is, the pathway emissions could be expected to follow in the absence of any action on climate change.

TIMES does not work on the basis of deducting abatement from projected emissions; instead, it identifies the most efficient parts of the system to remove carbon and allocates sector envelopes accordingly. Sectors then develop their proposals and policies to ensure their emissions remain within these limits.

The consequence of employing TIMES is that it does not present annual emissions abatement for individual proposals and policies as was the case in the two previous reports on proposals and policies. There is no counterfactual from which to deduct abatement.

Furthermore, attributing abatement to any one sector is problematic when considering the whole energy system. TIMES tells us the amount by which emissions need to fall over time to meet our targets and while it does produce suggested sector envelopes for meeting these targets, these cannot necessarily be translated into abatement by sector. For instance, does a reduction in electricity demand in one sector equate to abatement for that sector or for the electricity generation sector? Similarly does an increase in electric vehicles result in emissions abatement from transport, an increase in demand from the generation sector or a reduction in emissions from refineries? TIMES addresses this challenge by taking a system-wide view.

A constraint associated with the previous approach was that while sectors could individually consider where they could most cost-effectively abate emissions, they could not see how the impacts of their efforts compared on a consistent basis with other sectors. TIMES allows us to identify sectors of the economy that can be decarbonised most cost-effectively and to direct our efforts accordingly.

A further benefit of the TIMES approach is that the resulting pathway and sector envelopes will be internally consistent, so a demand for, say, electricity in one sector needs to be met by increased generation and any fuel required for that additional electricity generation needs to be sourced from finite supplies.

The emissions reduction pathway, when combined with further sector analysis, allows us to identify policy outcomes (such as penetration rates of low emissions vehicles or carbon intensity of energy generated at fixed time points) that need to be delivered across sectors over the 15 year period, in order to meet the statutory targets. Specifying the policy outcomes that need to be delivered, rather than simply stating our proposals and policies, improves transparency and accountability as well as enabling the public to have a better understanding of what we will achieve 'on the ground'. This will also help us in the design, costing and delivery of policies.

Providing a concrete set of policy outcomes also provides a direct link to Scottish Government action. As circumstances change, this means it will be easier to identify when we need to take informed and timely corrective action to ensure the Climate Change Plan stays on track following publication.

In the absence of abatement numbers, the verification of the projected emissions consequences of a particular policy or proposal will be provided by the results of the monitoring framework and the Greenhouse Gas Inventory. The monitoring framework will describe whether the policy outcome has occurred and the Inventory will show whether overall emissions have reduced for the relevant sector as anticipated. This makes it a more robust and more transparent approach than for previous RPPs.