Estimation and back extrapolation of CO₂ emissions from the road transport sector: Emissions in ireland, 1990 to 2013

The estimation of CO2 emissions is an important information process in the assessment of climate impacts, mitigation policy development, and assessment of the impacts of previous interventions in various polluting sectors. This investigation comprised the estimation of CO2 emissions from the road transport sector in Ireland using a previously unavailable level of data disaggregation for vehicle mileage as well as using vehicle class specific data and an improved estimation methodology. Estimates of CO2 emissions were carried out for the recent years up to 2013 and these were also back extrapolated to 1990. CO2 emissions were estimated using COPERT software. Historic vehicle fleet data were restructured, annual mileage data were estimated and back extrapolated using a linear regression approach.

The results of this investigation outline the distribution of CO2 emissions across the transport sector in Ireland in 2013. These results also facilitate a comparison of the impacts of the new input data and improved estimation methodology over previous estimates of CO2 emissions. Previous assessments (1990–2012) were shown to have under-estimated the contribution of diesel fuelled passenger cars by more than 38%. Diesel fuelled passenger cars were also shown to account for the majority of CO2 emissions from road transport activities in Ireland in 2013.The results of this investigation highlight the impact of recent trends of increasing numbers of diesel car purchases in Ireland, which has been incentivised by government climate change policy.