Historical emissions data were obtained from the ‘Final UK greenhouse gas emissions national statistics: 1990-2019’ (UK Government, 2021a). Provisional emissions data for 2020 was also included (Department for Business Energy & Industrial Strategy, 2021a). The UK provides inventory data to the UNFCCC that includes emissions from Overseas Territories and Crown Dependencies, which are not covered by UK climate policy and are not included in government emission projections. For this reason, we have chosen to use national emissions statistics rather than UNFCCC inventory emissions.
NDC and other targets
For the 2020 target, we took the average emission level across the five years of the UK’s third carbon budget and subtracted the projected level of removals from LULUCF in that year (UK Government, 2019e). LULUCF is projected to provide an accounting contribution of -16 MtCO2e in 2020. For comparability between countries, the CAT presents all targets excluding LULUCF.
The UK government has indicated that achievement of the 2030 NDC target of at least a 68% reduction below 1990 levels will be assessed against historical emissions that include non-CO2 emissions converted into global warming potentials (GWP) from the IPCC’s Fifth Assessment Report (AR5). Consequently, we converted the UK’s 1990 non-CO2 emissions into AR5 GWP before calculating the 2030 emissions level implied by the new target. In addition, the UK Government has specified that the 1990 baseline will also use F-gas emissions from 1995, therefore, the difference between 1990 and 1995 F-gas emissions (converted into AR5 GWP) was added to the 1990 baseline before calculating the implied 2030 emissions level.
As the CAT presents all data across countries in GWP from the IPCC Fourth Assessment Report (AR4), the 2030 emissions implied by the NDC target in AR5 are then converted back into AR4 GWP. This is done by applying the ratio of total emissions using AR5 and AR4 emissions in 2019 to the calculated 2030 emissions using AR5 GWP values. This is done as it is not possible to calculate projected emissions on a gas-by-gas basis, due to the fact that this level of detail is not provided in government projections.
For the UK’s most recent GHG inventory, the methodology used to calculate emissions from peatlands was adjusted to account for the IPCC 2013 Supplement to the 2006 Guidelines for National Greenhouse Gas Inventories: Wetlands (IPCC, 2014). This resulted in significant additional historical emissions (+2% in total GHG emissions in 1990, +3.7% in 2018) and implies that projected LULUCF emissions using the old methodology must be adjusted upwards. By applying the difference in LULUCF emissions in the 2019 inventory (new methodology) and 2018 inventory (old methodology) to projected 2030 LULUCF emissions under current policies, we estimate the level of LULUCF emissions to subtract from the 2030 emissions in AR4 implied by the NDC.
For the UK’s 2035 emissions target, the same methodology was applied as for the 2030 NDC target. As this target includes emissions from international aviation and shipping, these emissions were added to the 1990 baseline. Projected 2035 emissions from international aviation and shipping were then removed from the implied 2035 target emissions level, as these emissions are captured under our IMO and ICAO assessments, and would be double counted if they remained as part of the UK’s total emissions.
For the 2050 net-zero target, we took the upper and lower projections of the CCC’s LULUCF emissions in 2050 (Core Scenario and Further Ambition minus Energy crops, agroforestry & hedges) and added this to the zero emission baseline (Committee on Climate Change, 2019b).
Current policy projections
The current policy projections from 2019 to 2030 were obtained from greenhouse gas emission projections updated annually by the UK Government which were then harmonised to the latest historical and provisional data of 2020 (UK Government, 2020j). The UK’s annual emission projection report presents projections considering future impacts of policy measures enacted as of August 2019 (UK Government, 2020k). For details of the policies included, see Annex D of the BEIS Updated Energy and Emissions Projections 2019 report. The CAT assesses the policies contained in the ‘Existing Policies’ scenario.
As a number of significant policy announcements have been made since August 2019, a quantification of government emission reduction projections has been incorporated into the current policy projection pathways. Projected cumulative emission reductions outlined in the UK Government’s Energy White Paper (230 MtCO2e) were assumed to occur between the years 2023-2032 and a linear increase in annual emissions reductions over this period of 2 MtCO2e per year was assumed.
The level of projected emissions reductions in the government’s Energy White Paper (230 MtCO2e) considerably exceed those outlined in the previously released Ten Point Plan for a Green Industrial Revolution (185 MtCO2e), although it is not explicitly outlined where exactly these additional emission reductions are projected to come from. To account for this level of uncertainty, a range of current policy projections was created, with the emissions reductions outlined in the Ten Point Plan subtracted from the latest government projections, creating the top of the range, while the emissions reductions outlined in the Energy White Paper are subtracted from the latest government projections, creating the bottom of the range.
Planned policy projections
In this update we have chosen not to include a planned policy pathway for the UK. At the time of publication, the UK Government’s 2020 annual emission projections had not yet been released, and we have therefore reverted to the 2019 projections. As this projection does not include the numerous policy announcements of the last 12 months, the planned policy projection (“reference scenario”) is only 5 MtCO2e lower than the current policy projection (“existing policies”). It was felt that including this alongside the two current policy projections amended for COVID-19-related GDP growth estimates would provide a false sense of the extent of policy development.
Once the UK government’s 2020 emissions projections are released, the assessment will be updated, and the planned policy scenario will be included once more.
We applied a novel method to estimate the COVID-19 related impact on emissions in the years following the significant dip in 2020. The uncertainty surrounding the severity and length of the pandemic creates a new level of uncertainty for current and future greenhouse gas emissions. We distil the emission intensity (GHG emissions/GDP) from the pre-pandemic current policy scenario and apply to it most recent GDP projections that take into account the effect of the pandemic.
To capture a wide range, we have used more than one GDP projection. For the range of Post COVID-19 current policies scenarios, we have used the 2021 and 2022 GDP growth rates in the UK Treasury’s April 2021 “Forecasts for the Economy: A Comparison of Independent Forecasts” and IMF GDP growth projections from 2021-2026 (HM Treasury, 2021; IMF, 2021). We then use the GDP growth rates until 2035 that were used as a basis for the original pre-pandemic current policy scenario.
We also considered 2021 and 2022 GDP growth projections from the OECD Economic Outlook Interim Report March 2021, but these fell within the range of those from the UK Treasury and the IMF, so were not incorporated into the analysis.
Global Warming Potentials
The CAT uses Global Warming Potential (GWP) values from the IPCC’s Fourth Assessment Report (AR4) for all figures and time series.