Overshoot pathway fingerprints persist after global temperature stabilization

Assaf Shmuel, Annika Högner, Niklas Schwind, Vassili Kitsios, Carl-Friedrich Schleussner

Exceedance of global warming thresholds under overshoot, peak and decline pathways may leave regional climate legacies that persist even after global temperature stabilization. This study examines whether such overshoot pathway fingerprints remain detectable after stabilization at similar global warming levels by comparing two multi-century CMIP6 simulations with different magnitudes and characteristics of temperature exceedance. Using machine learning classifiers and statistical tests on regional multivariate climate data, we show that overshoot pathways leave detectable regional fingerprints. Regional climate states remain distinguishable between pathways, even when global temperatures stabilize. Comparisons with transient pre-overshoot periods at similar global warming levels further indicate that some regional differences will not reverse to their transient pre-exceedance state. These findings underline that the consequences of overshoot pathways cannot be assessed from global mean temperature trajectories alone. Evaluating possible impacts and risks from temporary exceedance of global warming of 1.5 °C requires attention to persistent regional fingerprints, including changes in the distribution and spatial structure of climate variables after stabilization.