image: Climate risk is higher in pathways reaching a temperature level by the end of the century with climate overshoot, i.e., temporarily exceeding a temperature level and then returning to that lower temperature, as compared to pathways reaching the same temperature level without overshoot. The higher and the longer the overshoot is, the greater climate impacts are expected within social and humanitarian systems.
Credit: Kruczkiewicz et al.
In a Perspective, the authors suggest that the social and humanitarian impacts of overshooting the Paris Agreement’s aspirational goal of a 1.5 degrees Celsius rise in global mean temperature remain largely unknown, despite robust knowledge of physical climate impacts. Andrew Kruczkiewicz and colleagues outline five factors that policymakers and planners should take into account when considering the human impacts of climate overshoot: peak warming and duration of overshoot, localized amplification of effects, timing of arrival, adaptation limits, and dynamics of overshoot reversal. The authors note that emissions levels agreed-upon in theory through international negotiations put the world on track to significantly exceed 1.5 degrees Celsius global mean temperature before the 2050s, likely resulting in decades of climate overshoot. The authors argue that both the magnitude and duration of overshoot must be limited as much as possible and the 1.5 degree warming threshold should remain the target to secure a liveable future. But bringing the temperature back down post-peak could be a bumpy road, with periods of increase, decrease, and stability in global mean temperature, rather than a smooth decline. The authors call for further investigation into the potential impacts post-peak, including assessment and communication of uncertainty related to various scenarios. Different recovery trajectories would have distinct implications for humanitarian needs, disaster risk management including early warning systems, climate finance priorities, and infrastructure development. The authors call for enhanced research on potential human and social impacts of overshoot, improved planning by humanitarian organizations for irreversible changes, and strengthened national climate commitments. According to the authors, understanding how social and economic systems will be impacted during climate overshoot is necessary to identify, tailor, and implement appropriate adaptation and risk reduction strategies in the years and decades ahead. Further, the authors note this work is of increased importance as it coincides with the run-up to COP30 in Brazil, where overshoot and how to address the related risks are of increasing concern.
NOTE: An earlier version of the author’s final manuscript, as accepted for publication by the journal, but prior to copyediting or typesetting, was published on October 18, 2025.
Journal
PNAS Nexus
Article Title
The human and social impacts of climate overshoot
Article Publication Date
18-Nov-2025