We are proud to share that our TipESM Researchers have published a new paper on 9 October 2025:

Bourgeois, T., Tran, G. T., Jeltsch-Thömmes, A., Schwinger, J., Fröb, F., Frölicher, T. L., Blenckner, T., Torres, O., Negrel, J., Keller, D. P., Oschlies, A., Bopp, L., and Joos, F.: Mapping the safe operating space of marine ecosystems under contrasting emission pathways, Biogeosciences, 22, 5435–5462, https://doi.org/10.5194/bg-22-5435-2025, 2025.

Anthropogenic greenhouse gas emissions cause multiple changes in the ocean and its ecosystems through climate change and ocean acidification. These changes can occur progressively with rising atmospheric carbon dioxide concentrations, but there is also the possibility of large-scale, abrupt, andpotentially irreversible changes, which would leave marine ecosystems with limited opportunity to adapt. Such changes, either progressive or abrupt, pose a threat to biodiversity, food security, and human societies. However, it remains notoriously difficult to determine the exact limits of a “safe operating space” for humanity.

In this study, the authors have mapped, for a variety of ocean impact metrics, the crossing of limits, which are defined using the available literature and to represent a wide range of deviations from the unperturbed state.

The authors have assessed the crossing of these limits in three future emission pathways:

These scenarios are simulated by the latest generation of Earth system models and large perturbed-parameter ensembles with two Earth system models of intermediate complexity. Using this comprehensive model database, they have estimated the timing and warming level at which 15 different impact metrics exceed four limits, along with an assessment of the associated uncertainties.

They have found that under the high-emissions scenario, the greatest severity of impacts is expected, with high probability of longer marine heatwave durations, loss of Arctic summer sea ice extent, expansion of undersaturated ocean areas with respect to aragonite, and a decrease in plankton biomass.

The probability of exceeding a given limit generally decreases clearly under a low-emissions scenario. Yet, exceeding ambitious limits for steric sea level rise, Arctic summer sea ice extent, Arctic aragonite undersaturation, and plankton biomass is projected to be difficult to avoid (high probability) even under the low-emissions scenario. Compared to the high-emissions scenario, the scenario including a temporary overshoot reduces, with high probability, the risk of exceeding limits by the year 2100 for marine heatwave duration, Arctic summer sea ice extent, strength of the Atlantic meridional overturning circulation, aragonite undersaturation, global deoxygenation, plankton biomass, and metabolic index.

The study highlights the urgent need for ambitious mitigation efforts to drastically minimize extensive impacts and potentially irreversible changes to the world’s ocean ecosystems.