The last 12,000 years show a more complex climate history than previously thought

Oct 4, 2022

An international team of researchers from Germany, the United Kingdom, Switzerland, Canada and France reveal the complexity of temperature trends over the past 12,000 years.

The new study highlights the importance of including regional climate variability in climate models. For example, in the high latitudes, solar radiation and ice extent played an important role in climate changes during the Holocene. A scientist stands in front of the Greenland ice sheet (Jakobshavn Isbræ Glacier). Copyright: Vincent Jomelli

We rely on climate models to predict the future, but models cannot be fully tested as climate observations rarely extend back more than 150 years. Understanding the Earth’s past climate history across a longer period gives us an invaluable opportunity to test climate models on longer timescales and reduce uncertainties in climate predictions. In this context, changes in the average surface temperature of the Earth during the current interglacial Epoch, the Holocene (approximately the past 12,000 years), have been thoroughly debated over the past decades. Reconstructions of past temperature seem to indicate that global mean temperature showed a maximum around 6,000 years ago and has cooled until the onset of the current climate crisis during the industrial revolution.

Climate model simulations, on the other hand, suggest continuous warming since the start of the Holocene. In 2014, researchers named this major mismatch between models and past climate observations the “Holocene Temperature Conundrum“.

In this new study, scientists used the largest available database of past temperature reconstructions extending back 12,000 years to carefully investigate the geographic pattern of temperature change during the Holocene. Olivier Cartapanis and colleagues find that, contrary to previously thought, there is no globally synchronous warm period during the Holocene. Instead, the warmest temperatures are found at different times not only in different regions but also between the ocean and on land. This questions how meaningful comparisons of the global mean temperature between reconstructions and models actually are.

According to the lead author Olivier Cartapanis, "the results challenge the paradigm of a Holocene Thermal Maximum occurring at the same time worldwide”. And, while the warmest temperature was reached between 4,000 and 8,000 years ago in western Europe and northern America, the surface ocean temperature cooled since about 10,000 years ago at mid-high latitudes and remained stable in the tropics. The regional variability in the timing of maximum temperature suggests that high latitude insolation and ice extent played major roles in driving climate changes throughout the Holocene.

Lukas Jonkers, co-author of the study and researcher at the MARUM – Center for Marine Environmental Sciences in Bremen, Germany, says “Because ecosystems and people do not experience the mean temperature of the Earth, but are affected by regional and local changes in climate, models need to get the spatial and temporal patterns of climate change right in order to guide policy makers”. Thus, the new work by Cartapanis and colleagues presents a clear target for climate models as the ability of climate model to reproduce Holocene climate variations in space and time, will increase confidence in their regional projections of future climate change.

Media contact:

Olivier Cartapanis; CEREGE, Aix Marseille Université, CNRS, IRD, INRAE, Coll. France, Technopole Arbois, 13545, Aix en Provence Cedex 4, France ([Bitte aktivieren Sie Javascript])

Original paper:

Olivier Cartapanis, Lukas Jonkers, Paola Moffa-Sanchez, Samuel L. Jaccard, Anne De Vernal: Complex spatio-temporal structure of the Holocene Thermal Maximum. Nature Comunications 2022. DOI: https://doi.org/10.1038/s41467-022-33362-1

Participating institutes:

- MARUM - Centre for Marine Environmental Sciences, University of Bremen
- CEREGE, University of Aix Marseille (France)
- Department of Geography, University of Durham (UK)
- Institute of Earth Sciences, University of Lausanne (Switzerland)
- Geotope, Université du Québec à Montréal (Canada)

MARUM produces fundamental scientific knowledge about the role of the ocean and the ocean floor in the total Earth system. The dynamics of the ocean and the ocean floor significantly impact the entire Earth system through the interaction of geological, physical, biological and chemical processes. These influence both the climate and the global carbon cycle, and create unique biological systems. MARUM is committed to fundamental and unbiased research in the interests of society and the marine environment, and in accordance with the Sustainable Development Goals of the United Nations. It publishes its quality-assured scientific data and makes it publicly available. MARUM informs the public about new discoveries in the marine environment and provides practical knowledge through its dialogue with society. MARUM cooperates with commercial and industrial partners in accordance with its goal of protecting the marine environment.

This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 897046 to OC. LJ is funded through the German climate modelling initiative PALMOD, funded by the German Ministry of Science and Education (BMBF). The research program of AdV is supported by the Natural and Engineering Research Council (NSERC) of Canada.