Regional Responses to Oceanic Variability Constrain Global Drought Synchrony

Hemant Poonia, Udit Bhatia, Vimal Mishra, Rohini Kumar, Danish Tantary Mansoor

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 scPDSI 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.