Oceanic Carbon Cycling Response to Global Temperature Changes

Project Information

CYCLOCARB

Grant agreement ID: 897046

DOI

10.3030/897046

Project closed

EC signature date 24 March 2020

Start date 1 April 2020

End date 1 May 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 277 061,76

EU contribution

€ 277 061,76

Coordinated by

UNIVERSITE D'AIX MARSEILLE
France

Periodic Reporting for period 1 - CYCLOCARB (Oceanic Carbon Cycling Response to Global Temperature Changes)

Reporting period: 2020-04-01 to 2023-03-31

Summary of the context and overall objectives of the project

Anthropogenic changes to the Earth's carbon cycle pose significant environmental and societal challenges for the coming centuries. The increasing levels of atmospheric CO2 are already impacting the climate and the ocean's carbon cycle, resulting in rapid global warming, rising sea levels, and ocean acidification, all of which have adverse effects on human societies.

To forecast the future, we rely on climate models; however, these models cannot be thoroughly tested as climate observations typically span less than 150 years. Geological records that reveal evidence of past climate and carbon cycle variations offer a unique way to contextualize ongoing changes and evaluate the performance of climate models over timeframes surpassing the instrumental record of the past few decades.

The CYCLOCARB project aims to assess the interactions between global climate changes and the ocean's carbon reservoir in the past. By utilizing a specialized database of paleoenvironmental indicators, the project provides new insights into carbon cycling and global temperature changes. The CYCLOCARB project has successfully described global and regional temperature variations, shedding light on the underlying processes involved, particularly the differing sensitivity of oceanic and continental surfaces to climate drivers and feedback mechanisms.

Additionally, studying carbon cycle indicators in the ocean based on microfossils obtained from sediment cores revealed a strong correlation between atmospheric pCO2 variations and physical and biological exchanges between the ocean's surface and its depths on glacial-interglacial timescales.

Therefore, the results of the CYCLOCARB project provide clear benchmarks for climate models, as their ability to accurately replicate past climate variations in both space and time will increase confidence in their regional projections of future climate change.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

A comprehensive database was created to gather information on various indicators used to study the ocean's past climate. These indicators include measurements of sea surface temperature, as well as stable isotopes of marine organisms and carbon content in sediment. Advanced computer algorithms were used to analyze the data and organize the database. This comprehensive resource, used in conjunction with other databases, has facilitated the study of both carbon cycling and past climate.

By studying the isotopic composition of marine organisms called foraminifera, we discovered two different patterns of carbon distribution during the last glacial cycle. We found that during colder periods, there was an increase in the biological process known as the "biological pump," which influences carbon dioxide levels and global temperature over the past 150,000 years.
Cyclocarb also investigated temperature patterns during the Holocene period, a time of great interest in paleoclimate research. Contrary to previous beliefs, we found that there was no globally synchronized warm period during the Holocene. Instead, the warmest temperatures occurred at different times and in different regions, including both land and ocean areas. These findings suggest that factors such as sunlight exposure at high latitudes and the extent of ice cover played significant roles in shaping climate changes throughout the Holocene.

This study provides a clear benchmark for climate models, as their ability to accurately reproduce Holocene climate variations in both space and time will enhance confidence in their regional projections of future climate change.

The study was published in an open-access scientific journal Nature Communications https://doi.org/10.1038/s41467-022-33362-1) and received widespread attention from the scientific community and the public. The research results were presented during the 14th International Conference on Paleoceanography (ICP14) in 2022 and gained coverage in news outlets, blogs, and social media platforms. The study's impact has been significant, with multiple citations and a high ranking among all research outputs tracked by Altmetric.

The researchers implied in the CYCLOCARB project are continuing their work and plan to present their findings at another conference in Paris. They are also preparing other research articles for publication, which has led to new collaborations with other institutions and laboratories in Europe. The article will be published in an open-access journal, ensuring broad access to the scientific community and the public.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The quantification of the carbon budget of the climatic system over time led to new estimations of the net disequilibrium in carbon cycling across an entire glacial cycle, a major scientific advance when compared to existing estimations for the LGM only. The soft tissue pump impact on the pCO2 over glacial/interglacial was quantified. The dynamic of the budget and the soft tissue pump variations will facilitate identifying the processes implied and their consequences on glacial-interglacial climate cycles and might affect the design of numerical simulation of the last glacial cycle. Ultimately, the results obtained during the CYCLOCARB project will support the understanding of modern carbon cycling, which informs policymakers on carbon emission management policies.

The study of Holocene temperature patterns at a global scale provides a clear benchmark for climate models, as their ability to accurately reproduce Holocene climate variations in both space and time will enhance confidence in their regional projections of future climate change. The results challenge the validity of comparing global mean reconstructions with numerical simulations to evaluate model skills and highlight the importance of regional processes such as sea ice. Moreover, the study will contribute to addressing the “Holocene Temperature Conundrum” that fueled numerous studies in the recent decade, casting doubt on climate model skills.

Thus, the CYCLOCARB project contributes to ameliorating climate projection for the 21st century and beyond, and the results obtained could be used by decision-makers and researchers to initiate policies, research, and technical solutions for adaptation and mitigation based on regional specificities.

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