This report presents cost-effective greenhouse gas emission reduction pathways for major emitting economies to keep global warming below 1.5 °C or well below 2 °C, as projected from least-cost scenarios of integrated assessment models in the IPCC AR6 scenario database.
Exploring greenhouse gas emission reduction levels and budgets using the IPCC scenario database
Achievement of the global climate goal of the Paris Agreement depends on the collective action by individual nations. This is reflected in the nationally determined contributions (NDCs). To ensure continued progress, the Paris Agreement established a ratcheting process in which the NDCs are evaluated and countries are encouraged to submit more ambitious NDCs. Parties submitted new NDCs by 2021 and will be required to submit updated NDCs by 2025. In this context, greenhouse gas reduction targets for 2035 and 2040 become increasingly important.
Cost-effective reductions can be explored with recently developed long-term low greenhouse gas emission pathways from global integrated assessment models. For this study, we used least-cost mitigation scenarios from the scenario database of the latest IPCC’s Sixth Assessment Report. The focus is on five major emitting economies (China, the EU-27, India, Japan and the United States) and the world as a whole. We have downscaled the original emission pathways at the regional level for these five major economies and further harmonised the emission data with their national inventory data.
Crucial to the Paris climate goal: higher 2040 greenhouse gas reduction targets per country
Our findings are that, in order to keep global warming to 1.5 °C with a limited overshoot, the least-cost greenhouse gas reductions by 2040, for the EU-27, Japan and the United States, are projected at between around 70% and 100%, relative to 2015 levels. For China and India, this is 65%–80% and 30%–75%, respectively. When comparing the reductions relative to 1990 levels, countries that have experienced a decline in emissions since 1990, such as the EU-27, need to achieve higher reductions (76%–96%, instead of 68%–95%). Note that these projections are solely based on least-cost considerations. When it comes to deriving emission levels, such an assessment of cost-effective reductions should be complemented with an assessment of equity considerations. In general, equity approaches lead to higher reduction targets for China, the EU-27, Japan and the United States, and to lower reduction targets for India.
For the EU-27, if only scenarios reaching climate neutrality by 2050 are included, reductions of 84%–97% below 1990 levels are needed by 2040 to meet 1.5 °C
The European Advisory Board on Climate Change recently published its advice on an EU climate target for 2040 of 90%–95%, relative to 1990 levels, based on the reduction range of 88%–95%. Narrowing down the selection of scenarios to those that achieve the EU’s existing reduction target of climate neutrality by 2050, as was done by the Advisory Board, results in cost-effective reductions of 84% to 97%. Based on equity principles equality, responsibility and capability, we found EU emission reductions excluding LULUCF of 79%, 95% and 97%, respectively.