25.11.2025: Ocean Circulation and Climate Dynamics Colloquium

When?  Tuesday 25 November 2025 at 13:00 (1:00 pm)

jointly with RD2’s “Current Topics in Marine Biogeochemistry”

Where?   Lecture Hall, Building 8, Wischhofstr. 1-3 and online
via Meeting link:https://geomar.webex.com/geomar-en/j.php?MTID=ma73a9dd4db0f5cb6275b471e1c5e6005

Meeting number: 2789 008 5026
Password: nhPGUfGj553

Abstract:

Abstract:

Carbon dioxide removal (CDR) could help to tackle the enormous mitigation challenges that have accumulated. CDR will be necessary to reach net zero emissions in sectors that are difficult or impossible to de-carbonize, and it might be the only way to return the Earth system to a less dangerous state once a “safe” temperature threshold has been exceeded. From an Earth system perspective, the efficiency of CDR and the reversibility of the Earth system are key to assessing CDR as a mitigation option. The former is an important factor for estimating the overall cost, while the later indicates if and on what timescale the desired effect of CDR - a reversal of climate change - could be achieved. In this talk, I will introduce and discuss different flavors of defining the concepts of reversibility and efficiency and present recent results from simulations with the Norwegian Earth system model. In line with many other modelling studies, these results show that global mean surface air temperature is reversible on a multi centennial timescale for moderate magnitudes of overshoot, while Earth system components with a large inertia (e.g., deep ocean properties, sea level rise, and many aspects of the global carbon-cycle) show changes that are irreversible on millennial timescales. I will also present results from less idealized simulations with a semi-realistic deployment of ocean alkalinity enhancement (OAE), which indicate that the contribution of CDR to a reduction in atmospheric CO₂ and a reversal of climate warming will likely be very limited. Hence, rapid emission reductions remain our best option to prevent dangerous anthropogenic interference with the climate system.

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