2.2.2. Applying Air Pollutant Emissions Data in GCAM-Korea

Air pollutant emissions data obtained from the National Air Pollutant Emissions Service [43] was reclassified to match NIER's activity sources to road transportation modes in GCAM-Korea (see Appendix A), fuels, and provinces in GCAM-Korea; 276 districts excluding Sejong are merged into 16 provinces. Gasoline, LPG, and diesel are aggregated into refined liquids, and CNG is mapped to gas in GCAM-Korea. FRD sources are sub-divided based on their share of energy use that is calculated using the energy consumption survey [44], VKT [45], and fuel efficiency [46] because the sub-classification of FRD sources is aggregated across vehicle type, vehicle size, and fuel type in the emissions inventory. As FRD emissions data for BEVs and FCEVs is currently not available in the emissions inventory, these emissions models are ignored in this study.

The calibration year for GCAM-Korea is 2010. However, emissions data for various years is used for the model's calibration (see Table 2) on account of missing data or data which contradicts energy use as illustrated in Figure 2.

**Table 2.** Year of air pollutant emissions data used for the calibration.

**Figure 2.** Reclassified emissions and energy use in road transportation. Note: Total energy use of road transportation is from the energy balance table in the Yearbook of Energy Statistics [44], and the sectoral share [47–49] is applied to total energy use.

For example, SOx emissions from light-duty 4-wheel vehicles (LDV4W) were notably high only in 2010, while its energy use increased steadily during the study period. As VKT is closely related to energy use, comparing emissions to energy use instead of VKT is suitable under the assumption that there is no big change of technology development or regulations on SOx emissions. In actual fact, there is no big change. The main reason that the calibration year's data is not used is for avoiding overestimation or underestimation of future emissions. If SOx emissions in 2010 are used for calibration, future emissions will be overestimated. Another reason for using different years' emissions data is the absence of data in the calibration year. FRD and PM2.5 emissions from light-duty vehicle 2-wheels (LDV2W) were newly released in 2015 and 2016, respectively.
