The Horn of Africa is a region in eastern Africa that includes Ethiopia, Somalia, Djibouti, and Eritrea. It is one of the world's driest and most vulnerable regions, facing recurrent droughts, famines, conflicts, and displacement.
But what caused this region to become so arid and unstable?
A new study by researchers from Utrecht University and Ghent University has shed some light on this question by revealing a prehistoric climate tipping point that changed the relationship between temperature and moisture in the Horn of Africa.
How did the researchers discover the tipping point?
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The researchers used a combination of paleoclimate data and numerical modeling to reconstruct the climate history of the Horn of Africa over the past 75,000 years.
They focused on a lake called Chala, which is located on the border between Kenya and Tanzania, near Mount Kilimanjaro.
Lake Chala is a natural archive of climate change, as its water level and chemistry reflect the amount and origin of rainfall in the region.
The researchers collected sediment cores from Lake Chala and analyzed their physical and chemical properties, such as grain size, mineralogy, and isotopes.
They also used a 3D model of the global ocean circulation to simulate how different sources of moisture, such as the Indian Ocean or the Atlantic Ocean, influenced the rainfall patterns in the Horn of Africa.
The researchers found that during the last ice age, between 75,000 and 11,700 years ago, higher temperatures in the Horn of Africa were associated with wetter conditions.
This was because warmer air could hold more moisture from the Indian Ocean, which was then transported by monsoon winds to the region.
However, around 11,700 years ago, when the global climate shifted from glacial to interglacial conditions, something changed.
Higher temperatures in the Horn of Africa were no longer linked to wetter conditions, but rather to drier conditions.
This was because warmer air could also enhance evaporation from the land surface and plants, which reduced the amount of moisture available for rainfall.
The researchers concluded that around 11,700 years ago, the Horn of Africa crossed a climate tipping point, where higher temperatures led to increased drought instead of increased rainfall.
This tipping point locked the region into a dry tropical climate regime that persists until today.
What are the implications and challenges of the study?
The study provided new insights into how and why the Horn of Africa became one of the driest regions in the world, as per Phys.org.
It also challenges some of the assumptions and predictions of climate models that suggest that higher temperatures will bring more rainfall to tropical Africa in the future.
The study has several implications and challenges for various fields of science and society. For example:
It can help improve our understanding and prediction of climate variability and change in the Horn of Africa and other regions that may experience similar tipping points.
It can help inform and evaluate policies and actions to mitigate and adapt to climate change impacts in the Horn of Africa, such as food security, water management, disaster risk reduction, and conflict resolution.
It can also raise new questions and uncertainties about how human activities, such as land use change or greenhouse gas emissions, may affect or trigger climate tipping points in different parts of the world.
