The article states that in the conditions of climate crisis aggravation the decarbonisation of the economy acquires the status of a global initiative aimed at achieving zero CO2 emissions by 2050. It is emphasised that this initiative is closely accompanied by legislation, business modernisation programmes and the creation of equal conditions for both domestic producers and exporters of carbon-intensive products (in particular, through the introduction of the carbon border adjustment mechanism - CBAM) and new rules of the world market. The consequences of CBAM implementation into Ukrainian metallurgical enterprises and the development of their foreign economic activity are determined in the example of Metinvest Group (Ukraine) enterprises. The ambivalence of CBAM is proven. It is substantiated that CBAM implementation will not accelerate, but, on the contrary, will slow down the process of decarbonisation, which will eventually lead to the loss of domestic metallurgical enterprises’ competitive position in the European market of metal products. Regarding the need to take transitional measures to decarbonise the metallurgical business (first of all, to ensure proper investment), the decision should be based on the expected decoupling effect - positive dynamics of economic growth while reducing the negative impact on the environment. The estimating method of the decoupling effect has been modified according to the integrated approach. A trend analysis of the integrated decalin effect indicator and its components was performed in Metinvest Group companies (Ukraine). Based on the results of econometric analysis of the impact of investment on greenhouse gas emissions, the author’s model for determining the volume of investment in the process of decarbonisation of metallurgical enterprises for the period up to 2050 is proposed. Comparative analysis is performed regarding investment in the process of decarbonisation under the scenarios by GMK Center, IEA, McKinsey and Roland Berger, as well as the author’s model.