The study conducted by a team of researchers led by Martin Trauth from Potsdam confirmed that tipping points in the climate system can be the result of a slow linear development or a flickering with two stable climatic states before a final transition occurs. The researchers analyzed sediment cores from the Chew Bahir Basin in southern Ethiopia, providing a record of 620,000 years of East African climate history. The transition from the African Humid Period to the arid conditions seen today was marked by intense dry and wet events alternating regularly over 1,000 years before a dry climate prevailed around 5,000 years ago. Understanding these tipping points and their early warning signals is crucial for climate change research and modeling.
The transition from the African Humid Period to dry conditions in North Africa serves as a clear example of climate tipping points in recent geological history. These points occur when small perturbations trigger a large, non-linear response in the climate system, leading to dramatic consequences for the biosphere. In North Africa, the disappearance of grasslands, forests, and lakes forced human populations to retreat to areas like mountains, oases, and the Nile Delta. This rapid and extensive climate change has significant implications for researchers studying the effects of climate change on human societies.
Climate researchers have identified two main types of tipping points: slow linear processes that culminate in a transition, and flickering between stable humid and dry climates before a transition occurs. Recognizing early warning signals for these tipping points is crucial for predicting future climate changes caused by human activities. Studying these tipping points can involve analyzing changes in variability, autocorrelation, and skewness in the climate system, allowing researchers to better understand and predict future climate transitions.
In a large-scale project funded by the German Research Foundation, researchers are analyzing lake sediments obtained through deep drilling in the Chew Bahir Basin, providing insights into the region’s climate history over the past 620,000 years. The study revealed a series of dry events at the end of the African Humid Period, occurring approximately every 160 years and lasting 20-80 years each. This climate flickering, characterized by extreme wet-dry events, can be simulated in climate models and observed in earlier climate transitions in the region. The presence of similar transitions in older sediment cores supports the idea that such climate flickering is characteristic of the region.
The researchers noted that very similar transitions, such as the change from humid to dry climate around 379,000 years ago, were also observed in the older sections of the sediment cores. This natural transition, occurring at a time when human influence on the environment was minimal, provides evidence against the idea that human activity accelerated the end of the African Humid Period. However, human populations in the region were undoubtedly impacted by the climate tipping, as evidenced by the traces of settlement in the Nile Valley at the end of the African Humid Period attracting millions of tourists each year. This research highlights the importance of understanding climate tipping points and their implications for future climate change scenarios.
