## 4 Discussion and Conclusions
The ETS was driven by coal and gas prices in the First Phase (2005-2007), electricity prices in the Second Phase (2008-2012) [14], a focus on auctioning rather than free allocation in the Third Phase (2013-2020) [15] and a focus on sectors most at risk of relocating their production outside of the EU in the Fourth Phase (2021-2030). Several low-carbon funding mechanisms will be established to support energy-intensive industrial and power sectors, such as the Innovation Fund and the Modernisation Fund [16]. Until 2018, emissions regulated by carbon pricing were covered by a price below EUR 10 per ton of CO\({}_{2}\). However, the report of the High-Level Commission on Carbon Prices states that the price needed to meet the Paris target of a temperature increase \"well below 2 \({}^{\circ}\)C\" is between EUR 40 and EUR 80 per ton of CO\({}_{2}\) by 2020 and between EUR 50 and EUR 100 per ton of CO\({}_{2}\) by 2030. Fortunately, the price has increased exponentially since 2021 and was never below EUR 60 per ton of CO\({}_{2}\) in 2022, which is in line with the Paris target [18]. However, with less stringent climate policies prevailing in many non-EU countries, the Council and the European Parliament reached a political agreement in December 2022 to implement the Carbon Border Adjustment Mechanism (CBAM) to prevent the risk of carbon leakage, which occurs when EU-based companies move their carbon-intensive production abroad, where less stringent climate policies prevail, or when EU products are replaced by more carbon-intensive imports. The CBAM promotes cleaner industrial production in non-EU countries and is aligned with the expiration of the allocation of free allowances to support the decarbonisation of EU industry. The CBAM will come into effect in October 2023 and will ensure that the carbon price for imports is equal to the carbon price for domestic production [17]. The results of this paper show that EU directives are not sufficient, and that each MS should introduce additional local measures. Adopting economic bonuses for countries that achieve relevant results compared to benchmarks may be a solution. These benefits could be additional means to invest in environmentally friendly practices. In contrast, countries that do not support the environmental transition, whose application procedures are too complicated or that are involved in corruption may be subject to economic sanctions. Also, the model would be improved by incorporating policies and other cultural strategies as variables of the model or developing new algorithms considering normalisation and new regressors. The main limitation of this study is that the algorithm does not consider Germany, the largest GHG emitter in Europe [8], as it achieves \(FP_{c}\) values above 0.20 in scenario 3 from 2029, and France, Italy and Ireland, as they have poor significance. Another limitation of this study concerns the availability of data which refer to the period from 2010 to 2020. Infact, some data are missing in the databases before 2010, and the data for the period after 2020 have not yet been published at the time of publication of the manuscript. The impact of newly introduced national and EU measures could be investigated in future studies to adapt the proposed methodology and the accuracy of the algorithm to contribute to a better GHG estimation and to propose additional strategies for the European Union. Conceptualization, A.M., C.P.-A., A.R.S., P.V.S. and G.M. ; data curation, A.M. and C.P.-A. ; formal analysis, A.M., A.R.S. and P.V.S. ; investigation, A.M., C.P.-A., A.R.S. and G.M. ; methodology, C.P.-A. and P.V.S. ; project administration, A.M.; supervision, C.P.-A. and A.R.S. ; writing--original draft, A.M., C.P.-A. and P.V.S. ; writing--review and editing, A.M. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. This study did not report any additional data. The authors declare no conflict of interest.