Climate tipping points are moments where small changes lead to dramatic shifts in the climate system, resulting in significant consequences for the environment and human societies. The transition from the African Humid Period (AHP) to dry conditions in North Africa serves as a powerful example of such tipping points in recent geological history.
There are two main types of climate tipping points that have been identified by researchers. The first type involves processes slowing down at an increasing rate, making it difficult for the climate to recover from disturbances until a transition occurs. On the other hand, the second type is characterized by a flickering between stable humid and dry climates shortly before the transition takes place.
In a study published in Nature Communications titled “Early warning signals of the termination of the African Humid Period(s),” researchers analyzed lake sediments obtained through scientific deep drilling in the Chew Bahir Basin in eastern Africa. These sediments provided insights into the past 620,000 years of climate history in the region.
The study revealed that at the end of the AHP, there were at least 14 dry events in the Chew Bahir sediments, each lasting 20-80 years and recurring at intervals of 160±40 years. This was followed by a transitional phase starting in 6,000 BC, during which seven wet events occurred in addition to the dry events. These high-frequency extreme wet-dry events represent a pronounced ‘climate flickering’ that can be observed in climate models and earlier environmental records from the region.
The findings suggest that transitions with flickering are characteristic of the North African region. Similar transitions from humid to dry climates were also observed in older sections of the sediment cores, indicating that such shifts are not solely due to human influence. While some argue that human activity may accelerate the end of the AHP, the study provides evidence that natural climate transitions have occurred in the past, influencing human settlements in the region.
Although human activities may exacerbate climate change, it is essential to recognize that natural climate tipping points have occurred throughout history. The transition from the AHP to dry conditions in North Africa serves as a reminder of the profound impacts that climate shifts can have on ecosystems and societies. The traces of settlement in the Nile valley at the end of the African Humid Period highlight how human populations have been influenced by such transitions, attracting millions of tourists to the region each year.
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