A typology of the temperature response in overshoot, peak and decline pathways

Abstract. As the window to limiting global warming to 1.5 °C closes, mitigation pathways consistent with this limit increasingly rely on temporary temperature overshoot. Despite recent advances in understanding how the Earth system responds to climate overshoot, uncertainty remains about the extent to which overshoot-induced changes can be reversed. Here, we synthesize the key features that determine climate reversibility and the asymmetry between responses to positive and negative emissions, challenging assumptions that net-negative emissions can undo overshoot-induced changes. We propose a typology of temperature responses in overshoot, peak and decline pathways that goes beyond established notions of reversible and irreversible climatic changes, incorporating underexplored climate feedbacks that may arise specifically during negative-emission phases. On this basis, we argue that an irreversible response, as evident from current-generation climate model simulations, cannot be ruled out. A more nuanced characterization and quantification of overshoot dynamics is critical for assessing the feasibility and risks of overshoot-based climate mitigation strategies.