The ocean currently absorbs around 25% of human‑produced CO2, thus slowing down global warming. Climate change, however, is altering this important service. Yet, it is not possible to say exactly how the carbon sink in the ocean will develop in the coming decades, as there is a lack of important scientific data from some of the world's oceans. This is the conclusion of the UNESCO's Intergovernmental Oceanographic Commission in its latest report to which Prof Judith Hauck from the Alfred Wegener Institute contributed.
If the ocean's ability to store CO2 continues to decline in the future, more of the greenhouse gas will remain in the atmosphere and accelerate global warming. This has implications for coastal communities, ecosystems and economies. Despite major scientific advances, there is still considerable uncertainty in estimating how much carbon the ocean actually absorbs each year. According to the latest report by UNESCO's Intergovernmental Oceanographic Commission (IOC), climate models therefore deviate from the actual state by 10 to 20 per cent worldwide, and even more in some regions. The main reasons for these gaps are a lack of data due to limited observations. The physical, biological, chemical and human-influenced processes that influence the ocean's carbon cycle are also not fully understood.
If the ocean's ability to store CO2 continues to decline in the future, more of the greenhouse gas will remain in the atmosphere and accelerate global warming. This will impact coastal communities, ecosystems and economies. Despite major scientific advances, there is still considerable uncertainty in estimating how much carbon the ocean actually takes up each year. Therefore, climate models deviate from the actual state by 10 to 20 per cent worldwide, and even more in some regions, according to the latest report by UNESCO's Intergovernmental Oceanographic Commission (IOC). The main reasons for these gaps are a lack of data due to limited observations. The physical, biological, chemical and human-influenced processes that influence the ocean's carbon cycle are also not fully understood.
These uncertainties have an impact on national climate and adaptation strategies, CO2 targets and projections by the Intergovernmental Panel on Climate Change (IPCC). "At the moment, many climate decisions are based on the assumption that the ocean will continue to absorb large amounts of our CO2 emissions in the long term. However, this may well change in the future," says Prof Judith Hauck from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). The biogeoscientist worked on the IOC report and contributed her expertise on modelling the oceanic carbon cycle and on the feedbacks between carbon and climate, which are changing due to anthropogenic emissions.
To reduce uncertainties in projections and set up effective global climate protection measures, the report identifies five areas where knowledge gaps should be addressed most urgently: the development of the ocean carbon sink in a changing climate, biological and microbial processes, carbon exchange across the land-ocean and ocean-ice interfaces, the impact of human activities on the carbon cycle, and ocean-based climate interventions such as carbon storage, aquaculture or geoengineering.
In concrete terms, this means that global research must strengthen its capacities worldwide and expand them, particularly in regions with limited data, for example via satellites, autonomous platforms and sustainable on-site measurements. This will enable models to better capture physical, chemical and biological processes. Research, socio-economics and politics should work more closely together to link scientific findings with social needs. As IOC Co-Chair Prof Carol Robinson emphasises: “The ocean is our greatest ally in climate protection. But we still don't know exactly how long it can continue to absorb carbon at its current rate.”
About the IOC report
The report by UNESCO's Intergovernmental Oceanographic Commission (IOC) is the most comprehensive assessment of the processes that are important for the uptake and storage of carbon in the ocean to date. 72 authors and 13 reviewers from 23 countries worked together on the report. It identifies research priorities to fill knowledge gaps in order to plan strong global climate protection measures that are needed to strengthen global climate planning. As the impacts of climate change accelerate, strengthening the science base is not only optional, but essential.
Link to the report: https://unesdoc.unesco.org/ark:/48223/pf0000397333.locale=en
