Singapore

Historical emissions for the period 2000-2020 were taken from national greenhouse gas inventory data, covering CO₂, CH₄, N₂O and F-gases (Department of Statistics Singapore, 2023). This was supplemented with data from the Fifth Biennial Update Report (BUR5) which provides emissions by sector for years 1994, 2000, 2010, 2012, 2014, 2016 and 2018 (National Environment Agency, 2022).

To estimate emissions for 2021-22, we applied a gas-by-gas approach. For energy CO₂ emissions, which accounted for 93% of Singapore’s emissions in 2018, we applied growth rates for energy CO₂ from the APEC Energy Demand and Supply Outlook, 8thedition for the years 2020/21 and 2021/22 (APEC, 2022). For non-energy CO₂, we used the growth in GDP as a proxy for the growth in non-energy CO₂ emissions, assuming constant elasticity of emissions and GDP (IMF, 2023). For non-CO₂ emissions, we have extrapolated emissions using a five-year average from historic emissions.

For historical years where national greenhouse gas inventory data was not available, i.e., 1990-93 and 1995-99, we also applied a gas-by-gas approach. For energy CO₂ emissions, we applied a linear regression using IEA energy-related CO₂ (IEA, 2023). For non-energy CO₂ and non-CO₂, we extrapolated linearly from historical data points.

A weighted average from the Fifth Biennial Update Report (BUR5) was used to convert HFCs and PFCs from Global Warming Potentials (GWPs) used in the IPPC’s Fifth Assessment Report (AR5) to those used in the Fourth Assessment Report (AR4) as these gases are not reported separately in the Department of Statistics data (Department of Statistics Singapore, 2023). All other gases are converted to AR4 GWPs on a gas-by-gas basis.

Singapore is a city-state with one of the highest population densities in the world and is nearly completely dependent on imports for food. Most of the remaining natural areas are sanctuaries. We therefore do not consider emissions related to LULUCF sector for the analysis, as they are negligible.

Singapore’s updated NDC provides an absolute emissions level (60 MtCO₂e) for 2030 in AR5 GWP (Singapore Government, 2022), which translates to 60.3 MtCO₂e in AR4 GWP. The conversion between AR5 and AR4 is insignificant because Singapore’s emissions are predominantly CO2 (94% in 2020).

Our current policy projection (CPP) for energy CO₂ is constructed using projections from the APEC Energy Demand and Supply Outlook for sectoral CO₂ emissions, energy balance, and energy mix (APEC, 2022). We have adjusted these projections to take into account the most recent developments announced by Singapore’s Energy Market Authority, as follows:

• Total electricity demand was revised upwards consistent with government base case projections outlined in (Energy Market Authority, 2023c). This is 22% higher than APEC projections for electricity demand in 2030.
• Electricity imports were increased to align with the government's targets. The emissions associated with this electricity was excluded from Singapore's domestic emissions, as these will occur outside of Singapore’s borders. Minimum and maximum trajectories for imports were constructed consistent with the government’s projections, which is the difference between our CPP min and CPP max scenarios (Energy Market Authority, 2023a).
• The gap between the increased electricity demand and the increases in solar and electricity imports was assumed to be met by gas-fired generation, consistent with the government’s plans to increase LNG imports and add gas-fired generation capacity (Energy Market Authority, 2022b, 2023d). The historic grid emissions factor (GEF) was applied to this generation.

We derive our current policy projections for non-energy CO₂ and non-CO₂ emissions by applying growth rates to the latest historical data. For non-energy CO₂, we have assumed GDP growth as a proxy for growth in emissions by applying projected IMF GDP growth rates (IMF, 2023). For non-CO₂ emissions, we have applied the growth rate for Singapore’s non-CO₂ emissions from the US EPA Global Non-CO₂ Greenhouse Gas Emission Projections & Mitigation Potential, harmonised to the latest historical year (U.S. Environmental Protection Agency, 2019).

To quantify Singapore’s residual emissions in 2050, when it aims to achieve net zero, we assume that Singapore will maintain its average historical LULUCF emissions until 2050. We estimate LULUCF emissions in 2050 of 0.08 MtCO₂e by taking the average LULUCF emissions for the years 2014, 2016, and 2018 from BUR5 data (National Environment Agency, 2022).

The CAT uses Global Warming Potential (GWP) values from the IPCC’s Fourth Assessment Report (AR4) for all figures and time series. Assessment completed prior to December 2018 (COP24) used GWP values from the IPCC’s Second Assessment Report (SAR).