 The study by Bjorn et al., 2021, evaluates two different approaches to setting science-based targets, SBTs, one based on absolute contraction and another based on proportional reduction. The authors find that the proportional reduction approach is more consistent with equity-related principles and is better able to conserve a global emissions budget than the absolute contraction approach. However, they do not consider the effectiveness of either approach to conserving sub-global emissions budgets or at meeting other criteria such as transparency and simplicity. Additionally, the authors' characterization of the absolute contraction approach does not accurately reflect how it is used by the science-based targets initiative, SBTI. Finally, the authors do not evaluate the effectiveness of the proportional reduction approach at conserving sub-global emissions budgets. To address this gap, we propose a set of principles that should be met by effective SBT methods and a high-level assessment of SBT methods against these principles. This article was authored by Andres Chang, Alexander Farsan, Alberto Carrillo-Pineda, and others.