Net-zero emission targets for major emitting countries consistent with the Paris Agreement

Abstract

Over 100 countries have set or are considering net-zero emissions or neutrality targets. However, most of the information on emissions neutrality (such as timing) is provided for the global level. Here, we look at national-level neutrality-years based on globally cost-effective 1.5 °C and 2 °C scenarios from integrated assessment models. These results indicate that domestic net zero greenhouse gas and CO₂ emissions in Brazil and the USA are reached a decade earlier than the global average, and in India and Indonesia later than global average. These results depend on choices like the accounting of land-use emissions. The results also show that carbon storage and afforestation capacity, income, share of non-CO₂ emissions, and transport sector emissions affect the variance in projected phase-out years across countries. We further compare these results to an alternative approach, using equity-based rules to establish target years. These results can inform policymakers on net-zero targets.

Fig. 1. Year when projected emissions reach net zero, per country (number of models representing that country between brackets), for 2 °C and 1.5 °C scenarios, for CO₂ emissions, CO₂ emissions from fossil fuels and cement (energy and industrial processes), and total GHG emissions (Kyoto Gases, including land-use emissions).

Individual models are indicated by symbols, whereas the bars show the minimum–maximum range (enlarged circles: model median). In some cases, individual models show a phase-out after 2100 in the extrapolated data (indicated by an asterisk) or no phase-out at all (#). Diamonds plotted at the 2030 mark indicate a change between the 2 °C and 1.5 °C scenario in terms of a country reaching net zero earlier than, similar to, or later than global average. Vertical dotted lines indicate the global average phase-out year.

Fig. 2. Influence of definitions on projected phase-out years.

Change in projected phase-out years for a all GHG emissions including land use when harmonizing the model projections towards the countries’ land-use emissions estimates, i.e., by adding the absolute emissions difference in 2010 between the inventory data and the model data to the model projections; values smaller than 0 indicate an earlier phase-out when emissions projections of individual models are harmonized to the inventory LULUCF data. b CO₂ emissions when negative emissions from BECCS are allocated to the biomass producer instead of the carbon-storing country (note that results are shown for fewer models, as POLES did not report the required variable agricultural production of energy crops). c The sum of CO₂, CH₄, N₂O and SF₆ emissions when using 100-year global warming potentials from the Fifth Assessment Report (AR5) of IPCC instead of the fourth (AR4). d All GHG emissions when the equity ranges from Robiou du Pont et al. are used instead of the model median for the default cost-optimal approach, noting that the results reported by Robiou du Pont et al. do not go beyond 2100, whereas the cost-optimal scenarios do. Therefore, India and Turkey are not shown for the 2 °C scenario, because the equity range included 2100 (which may actually mean somewhere after 2100), while the cost-optimal median phase-out year was calculated as being beyond 2100 in these two cases. Individual models are indicated by symbols, whereas the error bars show the minimum–maximum range from models (enlarged circle: median). Extrapolated emissions data were used to calculate the phase-out year difference, so as to not introduce a bias when calculating differences in phase-out years. Vertical lines at 0 indicate no difference between the default and sensitivity cases. BRA: Brazil, CAN: Canada, CHN: China, EU: European Union (EU27 + UK), IND: India, IDN: Indonesia, JPN: Japan, RUS: Russian Federation, TUR: Turkey, USA: United States.

Fig. 3. Fifteen explanatory variables vs. phase-out years across the ten countries (colours), the POLES and IMAGE models, and the 1.5 °C and 2 °C scenarios (shapes).

See Supplementary Table 2 for details of how the variables were calculated (units are displayed in the lower left corner of each panel).

Fig. 4. Breakdown of emissions in the phase-out year of total greenhouse gas emissions.

Emissions in the phase-out year of GHG (year indicated per model—focusing on the same two models as in the previous section, for readability), by greenhouse gas (colours) and country (panels), focusing on a country with an average phase-out year (b China), a country with a late phase-out (c India), and two with an early projected phase-out of GHG emissions (a Brazil and d USA). Positive numbers denote remaining emissions of CH₄, N₂O and F-gases (non-CO₂ GHG), and of CO₂ in industry, buildings and transport, whereas negative numbers denote negative emissions in energy supply and in Agriculture, Forestry and Other Land Use (IPCC Category 3). CO₂ from energy supply includes CO₂ emissions from fuel combustion and fugitive emissions from fuels: electricity and heat production and distribution (IPCC category 1A1a), other energy conversion (e.g., refineries, synfuel production, solid fuel processing, IPCC category 1Ab, 1Ac), including pipeline transportation (IPCC category 1A3ei), fugitive emissions from fuels (IPCC category 1B) and emissions from carbon dioxide transport and storage (IPCC category 1C). Negative emissions in this sector result from the use of (BE)CCS.