A new study reveals that climate change data from the ancient past can be useful to gain better insights into and better predict climate “tipping points.”
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Existing insights into tipping points, where the climate system exceeds a threshold beyond which large and usually irreversible changes take place, are restricted. The reason is such an event has not taken place in recent times and definitely not since scientists began recording climate data.
Earth System models that are regularly used for climate prediction are taken from the understanding of the chemical, physical, and biological processes that act together to shape the planet’s environment.
Researchers are aware that these models do not offer a comprehensive picture as they fail to simulate familiar climate events from the past.
New research published recently in Proceedings of the National Academy of Sciences and performed by scientists from the University of Birmingham and the University of Bristol shows how knowledge of climate reconstructions from thousands of years ago can help fine-tune Earth System models to offer a more precise knowledge of climate system thresholds.
Climate modelling is the only way we have to predict future climate change, but when models are developed they are only evaluated with weather observations from the past 150 years or so.
Dr Peter Hopcroft, Study Senior Author, School of Geography, Earth and Environmental Sciences, University of Birmingham
Dr. Hopcroft continues, "This means we have no way to verify their predictions of potential abrupt change—the risks of which are only likely to increase as the planet warms. Palaeoclimate records of abrupt climate changes from the deeper past allow us overcome this problem."
As part of the study, the researchers focused on a key example—the “greening” and subsequent quick desertification of the Sahara—which occurred in the mid-Holocene period, nearly 6,000 years ago.
The researchers fed data from fossil pollen and sedimentary records into a standard climate model, thus demonstrating how the model could then predict the Sahara’s transformation into a savannah, which was evident from the increased plant coverage, expansion of lakes, and most significantly the increased rainfall.
The researchers then independently compared their findings with studies of marine sediment records from the region, demonstrating how the model precisely captured a very quick return to the desert conditions over the Sahara.
We now need to apply these methods to other models to test how universal the results might be. But by demonstrating how paleoclimate information can be used to improve the way models can simulate past abrupt climate change, we hope that we can begin to increase our confidence in future projections of abrupt events.
Dr Peter Hopcroft, Study Senior Author, School of Geography, Earth and Environmental Sciences, University of Birmingham
Journal Reference:
Hopcroft, P O & Valdes, P J (2021) Palaeoclimate-conditioning reveals a North Africa land-atmosphere tipping point. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.2108783118.