A unified modelling framework for projecting sectoral greenhouse gas emissions

Effectively tackling climate change requires sound knowledge about greenhouse gas emissions and their sources. Currently, there is a lack of comprehensive, sectorally disaggregated, yet comparable projections for greenhouse gas emissions. Here, we project sectoral emissions until 2050 under a business-as-usual scenario for a global sample of countries and five main sectors, using a unified framework and Bayesian methods. We show that, without concerted policy efforts, global emissions increase strongly, and highlight a number of important differences across countries and sectors. Increases in emerging economies are driven by strong output and population growth, with emissions related to the energy sector accounting for most of the projected change. Advanced economies are expected to reduce emissions over the coming decades, although transport emissions often still show upward trends. We compare our results to emission projections published by selected national authorities as well as results from Integrated Assessment Models and highlight some important discrepancies. The energy and transportation sectors of emerging and advanced economies are responsible for much of the projected increases in greenhouse gas emissions by 2050 in the absence of policy action, according to a statistical approach that combines economic output, demographic change, and emission intensities.