Regional responses to oceanic variability constrain global drought synchrony

Abstract

Synchronized droughts threaten global food security, with concerns about increased frequency and duration under climate change. However, their long-term evolution and physical limits remain unknown. We analyze 61 drought networks over 120 years (1901–2020) of Self Calibrating palmer drought severity index (sc-PDSI) data, employing a suite of network synchronization measures and empirical orthogonal functions to unravel the physical drivers and limiters of drought synchrony. Our results show that, contrary to claims that synchronized droughts could affect up to one sixth of the global land mass, the maximum synchronized area fluctuates between 1.84% and 6.5% of the total land mass. Although we observe a strong dependence between drought onset and local crop failures, global drought synchrony is shaped by a dichotomy: temperature trends exacerbate it, while precipitation variability, modulated by sea surface temperature oscillations, limits it. This suggests that although drought hubs are increasing, large-scale synchronization across multiple agricultural regions is less widespread than expected, affecting global food security strategies.