Here, we provide the methodological summary of our NDC quantifications. If you use this work, please refer to our earlier paper that outlines our methodology:
Meinshausen, M., Lewis, J., McGlade, C. et al. Realization of Paris Agreement pledges may limit warming just below 2 °C. Nature 604, 304–309 (2022). https://doi.org/10.1038/s41586-022-04553-z
Or alternatively, and use this citation below:
Meinshausen, M, J. Lewis, J. Guetschow, Z. Nicholls, R. Gieseke, R, Burdon (2022), NDC factsheets 8th Nov 2022, available at https://www.climate-resource.com/tools/ndcs
Our quantification of the NDCs starts from what countries submit to the official NDC portal at the United Nations Framework Convention on Climate Change. Our primary historical database used is the PRIMAP-hist TP database (which is now another project of ours here at Climate Resource), specifically the dataset PRIMAP-hist TP version 2.4, available at primap.org. Only in a very few cases did we use specific data for a country, for example, if the country reported specific data in its NDC. The underlying data and the country NDCs are publicly available.
Conditional and unconditional, min-max
The Annex I countries - they tend to be the rich industrialised countries - are expected to state their targets unconditionally as none really considers international support should be provided for those countries to meet their targets. They have sufficient historical responsibility and also the capability to reduce their emissions first and foremost. The same also holds for a number of countries that have rich and industrialized economies, such as South Korea, Mexico or China. However, for many so-called developing countries, especially the least developed countries, the international community is expected to provide both technological and financial support. Thus, many of those developing countries will specify an unconditional target, which they implement with domestic resources. On top of that, conditional targets are specified that will be met if financial or technological support is secured. As a short-hand description, the targets that are labelled “conditional” are comprising both the unconditional and the conditional elements of the NDCs. A few countries also state ranges for their targets. For example, the (quite insufficient) targets that Australia previously put forward under the Morrison government, a 26%-28% reduction below 2005 levels by 2030 was stated as a range. In 2022 Australia updated its 2030 NDC target to -43%, which is an important step in the right direction. At other times, the quantification of targets is a bit uncertain, and alternative assumptions of some key underlying assumptions (such as different GDP growth rates in case a country has intensity targets) can lead to higher or lower 2030 emission level projections.
In these factsheets, we provide three different compilations. The first is the unconditional setting, ranging from the minimal to maximal unconditional NDC target. Often that unconditional NDC target is just a single emission level, not a range. The second is the conditional setting, ranging from the minimal to maximal emission level that would be in line with the full implementation of NDCs (full implementation of both conditional and unconditional elements). If the country does only have an unconditional NDC, then only that one is shown. The third setting is the min-max setting, ranging from the highest emission level of the unconditional target to the lowest emission level of the full implementation NDC (conditional and unconditional).
Inter- and extrapolations to 2030.
Our quantification of the NDCs goes through each submitted NDC document and attempts to decipher the quantifiable future emissions for 2025, 2030, and 2050. In just a few cases, countries only submitted 2025 or even submitted only 2035 or even (in one case) 2040 targets. We then employ linear interpolations and extrapolations to derive the 2030 emission level.
Covered and non-covered emissions, and LULUCF
More and more countries present their NDCs as whole-economy targets, that comprise emissions from the energy sector (usually including transport etc), the industrial and process emissions, waste, and agriculture. On forestry, i.e. the so-called land-use, land-use change and forestry (LULUCF) emissions, the countries vary in their coverage. If a country does not include, for example, the agricultural sector, we assume reference level emissions for those non-covered emissions, as they are not subject to the NDC target. We source these reference level emission changes from the SSP5 reference, downscaled to a country-by-country emission level (Guetschow et al., 2021). Sometimes, when countries include LULUCF into their NDC target, and we have a “with measures” LULUCF projection (many countries in fact provide those), then we infer the implicit target for total emissions without LULUCF. For example, in the case of the US, you can see in the factsheets that there is a small thin line below the bold fat one. The bold fat line indicates total emissions without LULUCF and the thin line is the net emission line, i.e. total GHG emissions including the net uptakes that the USA reports for its LULUCF sector. The NDC targets in fact relate, in the case of the USA, to the net total emissions including LULUCF. However, given that countries report natural carbon cycle fluxes as part of their LULUCF emissions (Grassi et al. 2021), this reported LULUCF emission is inconsistent with indicators such as the remaining global carbon budget or global net-zero CO2 years. Thus, our primary reference point in these NDC factsheets are total emissions without LULUCF.
The term 'hot air' was coined when Russia and other countries set themselves such unambitious targets that future emission levels would never overshoot them, even if not a single climate policy is put in place. That hot air was then sold on the international market, leading to a substantial erosion of trust in international emission trading systems at the time of the Kyoto Protocol. Times have moved on and it is not standard practice any more to simply trade hot air. Nevertheless, a few countries, such as Turkey and some developing countries, put forward targets that seem way out of tune with a normal increase of emissions, even if no climate policies are implemented. That means that their NDC targets are almost certainly achieved, and overachieved by a large margin. Not because of emission reductions and climate policies but because of insufficiently ambitious NDC targets. Similar things can be said for Australia and its Kyoto Protocol targets by the way, but that is another story.
In these factsheets, we provide you an option to approximate this 'hot air' effect. You can choose to exclude hot air, in which case we show the future emission levels that are the lower of the two: The NDC targets as the countries states them, or the SSP5-reference emission projections, as downscaled by our collaborator Johannes Guetschow (see Guetschow et al., 2021).
Per-capita emissions are calculated using the median UN population projection, 2022 edition. For international aviation, an approximation has been undertaken by dividing international aviation emissions by the number of people that approximately (before COVID) use international travel. While the total percentage of the world's population being in a plane is roughly estimated at 10-15% in any given year (and probably 80% of humanity have never flown), the fraction of people using international flights is more like 4% or 5%. Hence, per-capita emission levels for international aviation is shown relative to 5% of the world's population.