The statistical projection of global GHG emissions from a consumption perspective

Abstract

Projections of future emissions based on current trends are vital to assess the performance of mitigation efforts and to devise mitigation strategies. However, previous studies are uncertain how the persistence and convergence of mitigation efforts may impact future trajectories from the consumption perspective. Here we assume regional convergence over time after finding strong supporting historical evidence and develop a Markov Chain Monte Carlo (MCMC) Bayesian analysis of historical and projected consumption-based emissions during 1995–2050 via a modified Kaya identity. We find global emissions of 21–94 GtCO 2 eq yr −1 by 2050, slightly higher than SSP1-2.6 and encompassing SSP3-7.0, resulting in 1.4–2.9 °C of warming above pre-industrial levels mid-way through the century. The median projection shows a 2028 peak of 42 GtCO 2 eq yr −1 and an annual average decrease of 0.25 GtCO 2 eq thereafter. Future emission decreases result from the interplay between a rapid reduction driven by decreasing consumption-based emission intensities, especially in clothing and transport, and the change of final demand structure (−1.53 GtCO 2 eq yr −1 ) against increases from economic and population growth (+1.33 GtCO 2 eq yr −1 ). This highlights the importance in continually updating projections and considering models that reflect convergence and consumption structure changes, in order to better inform climate policy.