Scientists fear that climate change may cause simultaneous droughts on a global scale, which would have serious food consequences for humanity. A study of climate data from 1901 to 2020 shows a reality different from what has been estimated so far.
The researchers used a network-based approach. They treated the onset of droughts as interconnected events on a planetary scale. When two distant areas enter drought within a short time interval, they are considered synchronized.
This method made it possible to identify recurrent "drought poles", such as Australia, South America, southern Africa and parts of North America. These regions are often affected at the same time as others, but without covering the entire globe.
Simultaneous drought periods covered only between 1.8% and 6.5% of land areas, a proportion well below previous estimates. This research, published in
Communications Earth & Environment, highlights the central role of ocean cycles in this limitation.
Changes in ocean surface temperatures, particularly in the Pacific, play a major role in this limitation. The El Niño-Southern Oscillation phenomenon, for example, creates different regional responses. During El Niño phases, Australia becomes a central drought pole, while other areas experience different conditions. During La Niña periods, droughts are more geographically dispersed. These ocean oscillations thus prevent the emergence of a single, widespread episode.
The impact on crops is significant, but mitigated by this climatic diversity. In major agricultural areas, a moderate drought can increase the probability of poor harvests by more than 25%, even beyond 40% for corn and soybeans. However, since droughts do not occur everywhere at the same time, global food systems can adapt. Rainfall remains the dominant factor for drought severity, but the influence of temperature is increasing in some regions such as Europe and Asia.
By better understanding the interactions between oceans, precipitation and temperatures, decision-makers can target drought poles and develop strategies to stabilize agricultural markets and protect food supplies in the face of global warming.