This paper focuses on transformational processes in a post Paris agreement context. It uses IMACLIM-R, an E3 (Environment–Energy–Economy) model allowing for the integration of urban forms, transport dynamics, environmental policies and behaviors. Building upon the study of a set of local low carbon experiments throughout the European Union (EU), the paper explores two contrasted stylized scenarios of the low carbon transition in Europe. It highlights that carbon pricing policies are useful guides for transition but cannot achieve the ambitious objective without significant transition costs. It shows that low carbon experiments in the transport and energy sectors are critical dimensions of complementary measures in favor of green infrastructures. Broadening and upscaling low carbon experiments helps overcome the inertias of the transport sector by fostering radical changes in infrastructures, thereby introducing deep transformations in mobility behavior. This can then generate positive macroeconomic outcomes, even though they are also dependent on specific financial support, calling for a renegotiation of the social contract based on specific fiscal reforms and measures to secure funding for these initiatives. The paper concludes with some research avenues for improving this preliminary work and calls for a better understanding of the complexity of the socio-economic patterns of both the transition and the conditions for an effective implementation.

The successive versions of the GTAP databases are provided with GTAPAgg, a programme that computes values of the series of the database for any regional and sectoral aggregation. A 'self-trade' issue arises from the fact that GTAPAgg aggregates the several series concerned with international trade, like any other series, by simply summing them up : the resulting series include a share of exports and imports happening between the aggregated regions, which should rather be treated as economic flows internal to the region resulting from the aggregation process. This paper details a method that aims at solving this shortcoming, and discusses the importance of doing so. A first section puts the research question into context and discusses its likely importance when using GTAP as a calibration dataset for computable general equilibrium modelling. A second section details the analytics of the method proposed to correct the aggregation process, in the broader framework of a programme extending GTAPAgg to the production of national account matrixes in the standard United Nations format. An appendix provides the code of the extended aggregation programme developed.