Implications of overshoot for climate mitigation strategies

Temporary climate overshoot—especially for 1.5 °C—is now unavoidable. In this Perspective, we show how overshoot emerged in mitigation pathways over the past three decades, from a modelling device for exploring stringent climate goals to an inevitable feature of scenarios. Depending on its extent, overshoot affects the pace and feasibility of emissions reductions, the distribution of socio-economic outcomes, and climate risks in time and space. We show that the magnitude and consequences of overshoot depend not only on biophysical characteristics and model assumptions but equally on scenario design and social and institutional factors. We outline priorities for a new generation of models and scenarios that integrate different climate sciences, supporting robust climate strategies in a world of overshoot.