PNNL

Abstract

The COP26 Glasgow process resulted in many countries strengthening their 2030 emissions reduction targets and announcing net-zero pledges for 2050-2070. We use four diverse integrated assessment models (IAMs) to assess CO2 emission trajectories in the near- and long-term based on national policies and pledges, combined with a non-CO2 infilling model and a simple climate model to assess the temperature implications of such trajectories. Critically, we also consider the feasibility of national long-term pledges towards net-zero, to understand where the challenges to achieving them could lie. Whilst near-term pledges alone lead to warming above 2°C, the addition of long-term pledges leads to emissions trajectories compatible with a well-below 2°C future, across all four IAMs. However, whilst IAM heterogeneity translates to diverse decarbonisation pathways towards long-term targets, all modelled pathways indicate several feasibility concerns, relating to the cost of mitigation, as well as to rates and scales of deployed technologies and measures.