Uncertainties in macroeconomic assessments of low-carbon transition pathways - The case of the European iron and steel industry

The climate targets agreed in Paris 2015 render deep decarbonization of energy- and emission-intensive industries crucial. Policy makers are interested in the macroeconomic consequences of such decarbonization pathways and often rely on integrated modelling studies. However, the underlying modelling assumptions and uncertainties often remain unquestioned or invisible, although they may govern the models' results. For the case of a zero-process emission pathway of the European iron and steel industry, we demonstrate how different assumptions on different “layers” of uncertainty influence results. We show that effects strongly depend on technology choice, prevailing macroeconomic states as well as regional characteristics. The underlying socio-economic development and the climate policy trajectory seem to play a less important role. Particularly, we find that the choice of model, i.e. which macroeconomic theory strand it arises from, influences the sign and magnitude of macroeconomic effects and thus should be well understood in terms of appropriate interpretations by both modelers and policy makers. We emphasize that model assumptions should be transparent, results sought as to be robust across a range of possible contexts, and presented together with the conditions under which they are valid. To that end, co-design and co-production in research would support its relevance and applicability.