 The paper provides a comprehensive analysis of the uncertainty associated with non-CO2 greenhouse gas, NCGG mitigation. It develops three different scenarios of NCGG mitigation, which are used to calculate the corresponding carbon budgets and policy costs. The results show that the 1.5°C and 2°C targets are not achievable if the most pessimistic assumptions regarding NCGG mitigation are taken into account. Furthermore, the paper highlights the importance of understanding the technical limitations of NCGG mitigation, which can help bridge the gap between current and desired emissions levels. This article was authored by Mathijs Hornsson, Charlotte Tabek, Laina Hoagland-Esaxton, and others.