Climate overshoot legacy: Distinguishing transient biophysical change from irreversible socioeconomic loss

Current climate policy debates increasingly refer to “overshoot” pathways; temporarily exceeding 1.5°C before returning to safe levels via net-negative emissions. Yet, this conflates geophysical recovery with socioeconomic recovery. Temperature decline does not entail that affected systems, livelihoods, settlements, institutions, recover as a result. Current literature lacks a framework for assessing when, and for whom, overshoot impacts persist as permanent legacies. This paper addresses that gap. We characterise overshoot along its three dimensions that govern system response: magnitude, duration, and rate of change. We distinguish between biophysical hazard persistence: transient hazards that recede with temperature versus persistent hazards that do not, and socioeconomic reversibility: systems that recover post-overshoot versus those that cross thresholds and do not return. Whether a socioeconomic system follows a reversible or irreversible trajectory depends on the determinants of risk: hazard characteristics combined with exposure, pre-existing societal vulnerability and response. Applying this framework to key sectors (e.g. agriculture, health, and coastal systems) we show that societal vulnerability effectively lowers the threshold for irreversibility. The same physical overshoot may constitute a manageable adaptation challenge for high-capacity systems but trigger permanent loss for vulnerable ones. Furthermore, persistent biophysical change compounds this risk by degrading the ecosystems required for carbon dioxide removal, potentially constraining the very mechanisms needed for temperature reversal. The principal danger of overshoot, we argue, lies in the accumulation of irreversible socioeconomic legacies, with direct implications for climate justice and Loss and Damage frameworks.