Research Identifies Early Signs of African Humid Period’s End

The shift from the African humid period (AHP) to arid conditions in North Africa stands out as a prominent example of climate tipping points in recent geological records. These tipping points occur when minor disturbances provoke significant, nonlinear reactions in the climate system, leading to a transition to a distinctly different climate state, often with profound implications for ecosystems.

This transition in North Africa resulted in the disappearance of grasslands, forests, and lakes that were favorable for human habitation, compelling human populations to relocate to regions such as mountainous areas, oases, and the Nile Delta.

This discovery holds significant implications for researchers, highlighting how rapidly and extensively climate change can impact human societies.

Understanding the Two Types of Tipping Points in Climate Science

Climate scientists delineate two primary forms of tipping points: In the first type, processes decelerate at an accelerating pace, making climate recovery from disturbances challenging until a transition occurs. The second type involves oscillations between stable humid and dry climates shortly before the transition.

These insights are detailed in a paper titled “Early warning signals of the termination of the African Humid Period(s),” published in Nature Communications.

Martin Trauth elaborates on the distinct early warning signals for each type of tipping point, emphasizing the importance of studying and comprehending them to predict potential future climate tipping points induced by human activities. While the first type manifests a reduction in variability, autocorrelation, and skewness, the second type exhibits contrasting fluctuations, sometimes hindering the detection of an impending tipping point.

In a large-scale endeavor led by Martin Trauth and collaborators from the Universities of Cologne, Aberystwyth, and Addis Ababa, researchers scrutinize lake sediments retrieved through scientific deep drilling in the Chew Bahir Basin, a former freshwater lake in eastern Africa.

Analyzing Lake Sediments from the Chew Bahir Basin

collaborators from the Universities of Cologne, Aberystwyth, and Addis Ababa, researchers scrutinize lake sediments retrieved through scientific deep drilling in the Chew Bahir Basin, a former freshwater lake in eastern Africa.

“For this study, we examined six shorter (9 to 17 meters) and two long (292 meters) drill cores, providing insights into the climatic history of the region spanning the past 620,000 years,” elucidates Dr. Verena Förster-Indenhuck from the University of Cologne.

“At the conclusion of the African Humid Period (AHP), our analysis of the short cores from Chew Bahir revealed a series of at least 14 dry events, each lasting 20-80 years and recurring at intervals of 160±40 years,” notes Trauth.

Oscillations in Wet and Dry Conditions

“As the transition progressed, commencing around 6,000 BC, we also observed seven wet events alongside the dry episodes, exhibiting similar durations and frequencies. These rapid oscillations between extreme wet and dry conditions constitute a notable ‘climate flickering,’ replicable in climate models and evident in earlier environmental records from Chew Bahir. This suggests that flickering transitions are inherent to the region.”

Further validating this observation is the similarity of transitions found in older sediment core sections. Notably, the shift from a humid to dry climate approximately 379,000 years ago closely mirrors the end of the African Humid Period.

“This resemblance is intriguing as it occurred naturally, during a period when human impact on the environment was minimal,” remarks co-author Prof. Stefanie Kaboth-Bahr from Freie Universität Berlin.

Thus, evidence contradicts the notion of human activity hastening the demise of the AHP, as proposed by American colleagues. However, it is undeniable that the climate transition profoundly affected the region’s inhabitants, evident in the remnants of settlements in the Nile valley that continue to attract millions of tourists annually.

Read the original article on: Phys org

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