(Press-News.org) The transition from the African Humid Period (AHP) to dry conditions in North Africa is the clearest example of climate tipping points in recent geological history. They occur when small perturbations trigger a large, non-linear response in the system and shift the climate to a different future state, usually with dramatic consequences for the biosphere. That was also the case in North Africa, where the grasslands, forests, and lakes favored by humans disappeared, causing them to retreat to areas like the mountains, oases, and the Nile Delta. This development is of particular relevance for researchers, not least because it is an impressive example of how quickly and extensively climate change can affect human societies.
Climate researchers have identified two main types of tipping points: With the first type, processes slow at an increasing rate and the climate has a hard time recovering from disturbances until a transition occurs. The second type is characterized by a flickering between stable humid and dry climates that occurs shortly before the transition. “The two types of tipping points differ with regard to the early warning signals that can be used to recognize them,” explains Martin Trauth. “Researching and better understanding them is important if we want to be able to predict possible future climate tipping points caused by humans. While the slowdown seen in the first type of tipping point leads to a decrease in variability, autocorrelation, and skewness, the flickering in the second type leads to the exact opposite – and, in some cases, to the impending tipping point not being recognized.”
In the large-scale project, led by Martin Trauth together with colleagues from the Universities of Cologne, Aberystwyth, and Addis Ababa and funded, among others, by the German Research Foundation (DFG), researchers are analyzing lake sediments obtained by means of scientific deep drilling in the Chew Bahir Basin, a former freshwater lake in eastern Africa. “For the current study, six shorter (9 to 17 meters) and two long (292 meters) drill cores were evaluated, which can be used to reconstruct the past 620,000 years of climate history in the region,” explains Dr. Verena Förster-Indenhuck from the University of Cologne.
“At the end of the AHP, we observed at least 14 dry events in the short cores from Chew Bahir, each of which lasted 20-80 years and recurred at intervals of 160±40 years,” says Trauth. “Later in the transitional phase, starting in 6,000 BC, seven wet events occurred in addition to the dry events, which were of a similar duration and frequency. These high-frequency, extreme wet-dry events represent a pronounced 'climate flickering' that can be simulated in climate models and can also be observed in earlier climate transitions in the environmental records from Chew Bahir. This indicates that transitions with flickering are characteristic of this region.”
The fact that very similar transitions can also be found in the older sections of the sediment cores also supports this. In particular, the changeover from humid to dry climate around 379,000 years ago looks like a perfect copy of the transition at the end of the African Humid Period. “This is interesting because this transition was natural, so to speak, as it occurred at a time when human influence on the environment was negligible,” says co-author Prof. Stefanie Kaboth-Bahr of Freie Universität Berlin. Thus, there are many arguments against human activity leading to an accelerated end of the AHP, as proposed by American colleagues. Conversely, people in the region where undoubtedly affected by the climate tipping: The traces of settlement in the Nile valley at the end of the African Humid Period attract millions of tourists to the region every year.
The study on the web:
Martin H. Trauth, Asfawossen Asrat, Markus L. Fischer, Peter O. Hopcroft, Verena Foerster, Stefanie Kaboth-Bahr, Karin Kindermann, Henry F. Lamb, Norbert Marwan, Mark A. Maslin, Frank Schaebitz, Paul J. Valdes, 2024, Early warning signals of the termination of the African Humid Period(s), Nature Communications, DOI: https://doi.org/10.1038/s41467-024-47921-1
Images:
Drill site 2A_credit_Verena_Foerster: Scientific deep drilling in Chew Bahir, southern Ethiopia. Photo: Dr. Verena Förster-Indenhuck
Ethiopia_ChewBahir_2014_Dust Storm_credit_Verena_Foerster: Dust storm on the surface of the remote Chew Bahir Basin, a salt pan in southern Ethiopia, near the drill site of the Chew Bahir records spanning 620,000 years. Photo: Dr. Verena Förster-Indenhuck
Contact: Martin H. Trauth, Professor of Paleoclimate Dynamics
E-Mail: martin.trauth@uni-potsdam.de
Phone: +49 331 977-5810
Media information 07-05-2024/ No. 032
Matthias Zimmermann
University of Potsdam
Press and Public Relations Department
Am Neuen Palais 10
14469 Potsdam
Phone: +49 331 977-1474
Fax: +49 331 977-1130
E-Mail: presse@uni-potsdam.de
Internet: www.uni-potsdam.de/en/presse
END
WESTMINSTER, Colorado – 7 May 2024 – An article in the latest issue of Invasive Plant Science and Management provides new insights on a northern hydrilla (Hydrilla verticillata) subspecies (lithuanica) and its establishment outside the Connecticut River. Considered among the “world’s worst” aquatic weeds, northern hydrilla hinders recreational activities by forming dense canopies. If unchecked, it has the potential to displace native species and host a bacterium that produces ...
UCSF-led study finds artificial intelligence is as good as a physician at prioritizing which patients need to be seen first.
Emergency departments nationwide are overcrowded and overtaxed, but a new study suggests artificial intelligence (AI) could one day help prioritize which patients need treatment most urgently.
Using anonymized records of 251,000 adult emergency department (ED) visits, researchers at UC San Francisco evaluated how well an AI model was able to extract symptoms from patients’ ...
NEW YORK, NY - May 7, 2024 – On World Asthma Day 2024 the message is clear: "Asthma Education Empowers." The Forum of International Respiratory Societies (FIRS), of which the American Thoracic Society is a founding member, stresses the crucial role of education in empowering people with asthma to manage their condition effectively and to know when to seek medical assistance.
FIRS also urges health care professionals to enhance their awareness of the preventable morbidity and mortality from asthma and of the published evidence on effective asthma management, so they are equipped to provide reliable information and optimal treatment for their patients.
Asthma ...
A growing number of states and territories in the United States have legalized medical and recreational cannabis use. As such, recreational cannabis has been associated with a lower perception of risk of harm in the general U.S. population.
However, in women of childbearing age, evidence has shown that cannabis use may increase the risk of adverse reproductive and perinatal health outcomes. Furthermore, research on the perception of risk from using cannabis among vulnerable populations such as those with disabilities is lacking.
Using data from the 2021 National Survey on Drug Use and Health, researchers from Florida ...
Some of the final work of a late University of Virginia School of Medicine scientist has opened the door for life-saving new treatments for solid cancer tumors, including breast cancer, lung cancer and melanoma.
Prior to his sudden death in 2016, John Herr, PhD, had been collaborating with UVA Cancer Center’s Craig L. Slingluff Jr., MD, to investigate the possibility that a discovery from Herr’s lab could help treat cancer.
Eight years of research has borne that idea out: Herr’s research into the SAS1B protein could lead to “broad and profound” new treatments ...
SAN ANTONIO — May 7, 2024 —Southwest Research Institute (SwRI) has helped determine the viability of pressure relief valves for liquid natural gas tanks in the event of a train derailment for the Federal Rail Administration (FRA). The report from the FRA shows that a study conducted by SwRI demonstrates that the pressure relief valves work as designed to prevent overpressurization and explosion if a derailment occurs.
“The pressure relief valves on tanks that transport liquid ...
The air inside all personal vehicles is polluted with harmful flame retardants—including those known or suspected to cause cancer—according to a new peer-reviewed study published in Environmental Science & Technology. Car manufacturers add these chemicals to seat foam and other materials to meet an outdated federal flammability standard with no proven fire-safety benefit.
“Our research found that interior materials release harmful chemicals into the cabin air of our cars,” said lead author Rebecca ...
Jonah Berger and Olivier Toubia used natural language processing to understand what drives academic success. The authors analyzed over 20,000 college application essays from a large public university that attracts students from a range of racial, cultural, and economic backgrounds and found that the semantic volume of the writing, or how much ground an application essay covered predicted college performance, as measured by grade point average. Essays that covered more semantic ground predicted higher grades. Similarly, essays with smaller conceptual jumps between successive parts of ...
A study finds that most engineering PhD graduates will never secure a tenure-track faculty position. Over the past 50 years, the number of full-time faculty positions in US universities has steadily declined while production of science and engineering PhD graduates has nearly doubled. Siddhartha Roy and colleagues analyzed data on PhD graduates and tenure-track and tenured faculty members across all engineering disciplines from 2006–2021. The average annual likelihood of securing a tenure-track faculty position in engineering during this 16-year period was 12.4%. The likelihood of securing a tenure-track faculty position was 18.5% in ...
In the scientific literature, a citation acts as a mechanism to signal prior knowledge, enhance credibility, and protect against plagiarism. But it also gives credit to the individual or team who established or discovered the knowledge in question, and citations have thus emerged as a metric to measure the impact of a work or researcher. However, when a discovery or technique becomes common knowledge, scientists often stop bothering to cite it. Thus, the most impactful work is often undercited. Albert-László Barabási ...
