Dr. Hannah Daly:

I thank the Deputy. I could stay with the committee all day to talk on the topic of modelling. I am delighted to talk about it. The Deputy asked about open source modelling, which I will get to. I will first take a step back. The way I see modelling is not as a way to produce a set of answers or a single pathway or set of solutions. It is a process which helps to inform decision-making. I see it a little like producing a map. If we were all at the bottom of a challenging mountain and wanted to figure out the best way to get to the top, there is a potentially infinite number of ways we could do that but some are better than others. The best way depends on our relative skills and the knowledge we have about the pathway forward. It is an iterative process. As we gain more information about what lies ahead, we update our best information, preferences and so on. That is where I want to start. Models do not give any single answer and they are a simplification of reality. However, they are essential for group decision-making and plotting the best way forward.

My area of expertise is energy systems models and that was how we contributed to this process. We used the recently developed TIM to produce a range of different scenarios which would meet different levels of decarbonisation for the energy system, with different assumptions about demand and technology. It builds from a long history of energy systems modelling at University College Cork, led by Professor Ó Gallachóir, and it was a big group effort. There are a number of PhD students and postdoctoral researchers in the group who made critical contributions. The model is currently undergoing peer review. Peer review alone is only one important step. In this world where models are informing policy, it is important not only for the models to be peer reviewed but for them to be open and transparent. We have already published the model in its entirety and made it freely available, including publishing a web application where one can explore the various different scenarios that we developed for the carbon budget committee, the implications for investment, the marginal abatement cost and dozens of different outputs. One can also query the inputs.

As well as for transparency and trust in the process of science and forming this policy process, it is very important to give capacity to national policymaking and academic analysis. The model is under review at the moment. At various stages during the development of the scenarios and the model, we brought it to different experts to get the best data and best assumptions.

One thing I would like to say about the scenarios that we undertook is that the model is called an energy system optimisation model. Given a set of inputs about technology availability, the speed at which technology can change and what fuel prices and demands will be, it outputs the optimum energy system in terms of cost optimisation. At the scale and speed of decarbonisation that these carbon budgets require, the solution is far more led by our assumptions on technology transition than on cost optimisation. It is really about how quickly things can change that determines what is the best solution. For example, someone else could take the model, turn on a bunch of different technology assumptions, assuming that there is breakthrough in something, and it could give a completely different solution. However, it is not about the answer; it about the process.