Droughts and Mega-Droughts

Drought is the deadliest natural disaster on Earth due to its long duration, wide spatial coverage and direct connection with the food supply for human beings. Drought develops slowly and thus is called a silent killer. This paper reviews the history of research on droughts and mega-droughts. Interannual droughts are in many places driven by the El Nino-Southern Oscillation, multi-decadal mega-droughts are often driven by the Atlantic Multi-Decadal Oscillation, while centennial mega-droughts are often driven by the Global Inter-Centennial Oscillation. More generally, droughts are affected by multiple factors including global sea surface temperature anomalies, local land-atmosphere feedbacks, internal atmospheric variability and external forcings from outside the climate system. Possible future research directions are also suggested.