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Our common future ocean in the Earth system – quantifying coupled cycles of carbon, oxygen, and nutrients for determining and achieving safe operating spaces with respect to tipping points

Periodic Reporting for period 2 - COMFORT (Our common future ocean in the Earth system – quantifying coupled cycles of carbon, oxygen, and nutrients for determining and achieving safe operating spaces with respect to tipping points)

Reporting period: 2021-03-01 to 2022-08-31

Human-induced forcing has instigated an unprecedentedly rapid and pervasive change of the Earth system and climate. Ocean biogeochemical climate is altered due to the progressing uptake of heat and CO2 (carbon dioxide) caused by human activity. The drivers include biogeochemical fluxes from land: river loads, atmospheric deposition, land-atmosphere greenhouse gas fluxes. Consequently, enhanced stratification, changes in global circulation, acidification, and loss of oxygen with the potential spreading of dead zones have already been observed globally. Additionally, ocean extreme events associated with these changes are expected to become more frequent and intense. Particularly dangerous are changes that, once a critical threshold or tipping point (TP) is reached due to external forcing, they accelerate strongly, and occur much faster than the rate of forcing. Past research has dealt mainly with Earth system tipping elements associated with low probability/high impact of risk events. In contract, COMFORT focuses on likelihood and quantification of ocean related high probability/high impact of risk tipping points, their impact on the wider Earth system, and provides the framework for taking optimal action to limit damage. The overall objective of COMFORT is to close knowledge gaps for key ocean tipping elements within the Earth system under anthropogenic physical and chemical climate forcing through a coherent interdisciplinary research approach. The project aims to provide added value to decision and policy makers in terms of safe marine operating spaces, climate mitigation targets, and feasible mitigation pathways. It focuses on the triple threat of (1) warming, (2) deoxygenation, and (3) ocean acidification, and how to optimally deal with it.

The following specific objectives are addressed (CT=core theme, WP= work package; Figure):
1. Identify climate-induced ocean TPs and attribute them to processes (CT1, WPs 1-2).
2. Quantify related impacts and establish multi-dimensional safe operating spaces (SOS) (CT2, WPs 3-4).
3. Provide respective mitigation targets and options, as well as projected mitigation pathways (CT3, WPs 5-6).
4. Integrate stakeholder knowledge and provide new results including data to users (CT4, WPs 7-10).
The research and dissemination/communication activities in the four Core Themes (CTs) and the ten work packages (WPs) have been delivered according to plan. In WP1, a substantial number of new observations and model simulations identified new change points, abrupt changes, and regime shifts in the physical and biogeochemical environment . In WP2, considerable new insights in extreme events such as marine heatwaves and compound extreme events (simultaneous extreme changes of temperature, pH value, and dissolved oxygen) have been provided. In WP3, a new classification of ecoregions was developed as well as a new method for analysing the impact of ocean warming on fish stocks. Also, a robust regional coral bleaching thermal threshold was determined. Important new results in WP4 were new quantifications on disappearing and novel ecological conditions and a safe-operating-space approach for safeguarding North Atlantic cod stocks. WP5 quantified the efficiency of CDR (carbon dioxide removal) methods including Earth system feedbacks and the role of CDR in the specification of critical environmental thresholds. In WP6, the robustness of Earth System Models (ESM) projections on ocean change was systematically assessed and the problematic role of overshoot scenarios for climate variations was quantified.

Concerning cross-cutting issues, progress has been made on stakeholder engagement, data set collation/compilation, communication/dissemination, project management, and following ethical rules. A suite of new peer-reviewed publications was achieved including papers in high-impact journals. COMFORT was among the most productive EU projects (CINEA funded) concerning material cited in the 6th Assessment Report of the Intergovernmental Panel on Climate Change (Working Group II). COMFORT also organised a policy event on tipping points together with the two other relevant projects that originally responded to the same call for proposals. The project website was continuously updated. A lot of effort and attention was placed on open access publishing.
The CT1 provided a new framework on the most crucial regional hotspots and time windows for tipping elements as well as tipping points related to warming, de-oxygenation, and ocean acidification.

The CT2 provided knowledge of the potential impact caused by the occurrence of climate-induced tipping points through a framework of “if” and “then”. A major progress has been made in assessing climatic impacts on a suite of organisms from plankton to commercially exploitable fishes. For this, a series of case studies have been carried out.

The CT3 provided the presentation of concrete mitigation targets and pathways to avoid dangerous impacts on the ocean realm by avoiding the crossing of critical thresholds for tipping points. The results should represent both: new forcing scenarios and new projections concerning pathways for a sustainable future of ocean ecosystems. CT3 explored a series of mitigation scenarios with complex Earth system models in order to determine potential options in climate policies. In view of the problems associated with Negative Emissions Technologies on one side, and the difficulties in achieving greenhouse gas emission reduction targets, societies may have to plan for a world with substantially more abrupt and extreme climate events.

In CT4, existing stakeholder knowledge has been combined with COMFORT recent results and new information has been provided to decision makers, policy makers, scientists, the IPCC writing teams, and the general public. The CT4 provided an optimal use and usefulness of the prospective COMFORT results of CTs 1-3 within the stakeholder communities.

In summary, COMFORT work has already contributed to a larger awareness of the scientific community, policy makers and the public concerning potential damage from imminent ocean tipping points due to warming, ocean acidification, and deoxygenation. An example is the tipping point policy event organised by CINEA and a joint policy brief ( In the final phase of the project four synthesis papers (one per CT) are expected to emerge forming COMFORT’s legacy. These papers are expected to help to make efforts towards limiting the damage of increased greenhouse gas emissions to the marine ecosystems and contribute to the IPCC report and a follow-up of the Paris agreement guided by scientific guardrails.

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