This paper is a very timely contribution that can be expected to be of broad interest to the Earth System Modelling and Integrated Assessment Modelling community. It deals with the topic of how to accurately assess the Earth system responses to Carbon Dioxide Removal (CDR) methods. It proposes approaches to create a no-CDR baseline against which the Earth system effects of activity-driven CDR can be evaluated, as well as a framework to quantify the direct effect of CDR on atmospheric carbon dioxide as well as the resulting feedbacks. Such a framework is essential for assessing the efficiency of activity-driven CDR in emissions-driven simulations, such as those proposed for CMIP7.