Some have argued that the universality of the Paris agreement has a cost for its effectiveness: a simple top-down agreement with strict laws would not be feasible, so countries have opted for self-differentiation in their NDC and « name and hypocrisy » to ensure compliance. The success of the Paris Agreement – and thus the global climate change regime – depends on the commitments that major emitters put on the table and implement over the next ten years. To link the ambitions of national climate promises with the level of global warming, we compare the COUNTRIES` CNN with the hybrid CBDR-RC attributions of global scenarios with median warmings of 2100 from 1.2 to 5.1 degrees Celsius (Methods, Fig. 7, 8, Complementary Table 4). We find that the CNNs of Canada, China and Russia are less ambitious than their CBDR-RC hybrid endowments, even in the least ambitious global emission scenario available in 2100 with 5.1 degrees Celsius of warming (Figure 4). While China`s NDC appears to be very unambitious and the latest analysis is correct to suggest a continued decline in Chinese emissions46, China would reach its emissions well before 2030 and could significantly improve its NDCs. India`s current policy also appears to be on track to overtake its NDC47. The NDCs of India, the EU, Brazil, the United States, Japan and China are causing a warming of 2.6 degrees Celsius, 3.2 degrees Celsius, 3.7 degrees Celsius, 4 degrees Celsius, 4.3 degrees Celsius and more than 5.1 degrees Celsius. Aggregate emissions from other economies are oriented with a median warming of 1.7oC. A 32-country (www.climateactiontracker.org/) subset think tank has achieved similar results for CNN in the United States, Russia and the Philippines, higher warming assessments for Ethiopia and Indonesia, and lower warming assessments for Australia, Brazil, Canada, China, Japan, India and the EU. The differences are largely explained by the difference in methodology, which only assesses the compatibility of a country`s efforts with the thresholds of 2 and 1.5 degrees Celsius based on the number of load-sharing approaches that its NDC brings into line with www.climateactiontracker.org/.
However, Brazil`s progress on deforestation is not taken into account in this study, as emissions from land use are not taken into account. Warming assessments and emission trajectories up to 2100 under the CBDR-RC hybrid approach, applied to the 1.5-C scenario and the 2-C scenario for all available countries, are in the additional data1 and can be viewed at: www.paris-equity-check.org/warming-check. Overall, this study is an operationalization of the current agreement to argue over the concepts of actions in order to achieve a common temperature goal. The hybrid approach, with its bottom-up combination of action concepts, reflects the architecture of the Paris Agreement pledge and provides a metric for the ratt-up process. The results of this study provide information on the adequacy of the programming targets contained in current CNN with the Paris Agreement. The bijlectivity between the NDC`s ambition and its temperature assessment is based on the strict monotony of the relationship between the 2030 emissions of the global scenario and the warming of the year 2100. We have selected nine global scenarios every 0.5oC to achieve such a strict monotony at the global level. Emission levels 2030 depend on the NDC temperature assessment of Figure 4, as this is a second-degree polynome adaptation based on assignments derived from the nine selected global scenarios.
A second-degree polynome smoothes variability while maintaining the greater sensitivity of national emission allowances 2030 with lower heating of 2100. If all governments reported NDC in the « 2oC compatible » category, warming could be kept below 2 degrees Celsius with a probability (66% or higher) but not « significantly below 2 degrees Celsius » or less than 1.5 degrees Celsius.