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Enhanced modelling of transport decarbonisation and policy pathways for Ireland
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Date
2023
Authors
O'Riordan, Vera
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
The release of increasing human-induced greenhouse gas emissions and the corresponding global temperature rise has prompted a growing political consensus on a decarbonised future to prevent any sustained economic or environmental harm. Many countries are using energy system modelling tools to develop strategies and policy measures to deliver timely and effective reductions of harmful greenhouse gas emissions across all energy-related sectors. Ireland, with ambitious legally binding carbon budgets, and decarbonisation targets for transport, is a country in the process of assessing and addressing key transport decarbonisation challenges faced by high-emitting countries. This thesis - with its scientific contributions on transport emissions, methodological advancements for transport and multi-sector energy systems simulation modelling, and policy recommendations on how effective measures have been in the past or could be in the future - serves as a small, but novel, piece of this process.
The thesis updates the Irish Car Stock Model to investigate the importance of taxation policy using a novel bottom-up stock simulation approach. The simulation model evaluates the 2008 car tax policy in Ireland and finds that while the policy was effective at reducing CO2 emissions, it had a high cost of carbon abatement, between €1,500 – 2,200 per tCO2.
The thesis develops the Irish Passenger Transport Emissions and Mobility (IPTEM) model, which for the first time, calculates the overall passenger transport demand in Ireland by trip purpose, trip distance, and mode type. The methodological advancement is in the combination of passenger transport demand from all modes of transport and information from the National Travel Survey, national transport providers, and the Irish Car Stock Model. The study finds that 82% of passenger transport demand is met by cars in Ireland, and the main reason for travel is for work (30%), shopping (19%), and companion journeys (16%). The study also finds that 40% of emissions come from journeys less than 8 kilometres.
In Chapter 4, this thesis develops a new model, the LEAP Ireland ASI (Avoid-Shift-Improve) model which projects emissions and demand for passenger and freight transport up to 2030. It is novel in its application of the Avoid-Shift-Improve framework for scenarios focused on reducing the need to travel in the first instance (“Avoid”), then on modal shifting towards increased public transport use and active travel (“Shift”), and then on scenarios focused on improving the fuels used to ones with a lower carbon intensity (“Improve). These scenarios are modelling in combination with one another and the interaction between the policies is also determined.
In Chapter 5, the thesis develops a new methodology for simulation modelling to project carbon dioxide emissions, how different scenarios could reduce carbon dioxide emissions, and how these fit in with sectoral emissions ceilings within carbon budgets. The thesis tracks past sectoral emissions and simulates the mitigation potential of a suite of scenarios for transport, residential, electricity, services, and industry sectors. The LEAP Ireland model developed in Chapter 5 can simulate the impact of additional policies, track policy performance, and simulate mitigation potential. The data sources, methodology, and carbon budget analysis are outlined in this novel simulation modelling framework designed to support countries with their carbon budgeting commitments. This thesis also examines the interaction effect between these policy scenarios and discusses their combinations' synergistic and antagonistic effects.
The contribution of this thesis is the improvements made to the modelling methods and more robust evidence base for developing sound decarbonisation transport policy measures by shifting the focus beyond car efficiency and electrification.
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Keywords
Transport decarbonisation , Energy systems modelling , Modal shift , Irish energy policy , Energy systems simulation modelling , Climate action
Citation
O'Riordan, V. 2023. Enhanced modelling of transport decarbonisation and policy pathways for Ireland. PhD Thesis, University College Cork.