Potential changes of finfish thermal habitat under negative emissions

The Paris Agreement has set out the aim to limit global warming to 1.5°C to reduce the risks of climate change. Yet, global carbon emissions continuously increase, such that the option of “negative emissions” – removing CO₂ from the atmosphere and storing it on land, underground or in the oceans - is discussed to delay the transition to a zero-carbon society. Among the options discussed are pathways where the 1.5°C temperature goal is temporarily overshot, while negative emissions are subsequently applied to return to a “safe” climate state.  

However, such overshoot strategies might have adverse effects. A previous study showed that a delayed removal of CO₂ does not simply lead to a warming while CO₂ is increasing, a cooling while CO₂ is decreasing and a subsequent steady atmospheric temperature but to a trajectory of warming-cooling-warming. As this response is related to the model´s sensitivity of the Atlantic large-scale ocean circulation, the amplitude of the warming-cooling-warming is most pronounced in the North Atlantic. Here, we extend this study to analyse the impact of the warming-cooling-warming trajectory on Finfish species that are commonly used for Aquaculture, that is Atlantic salmon, gilthead seabream and cobia. Via thermal windows of potential growth ranging from optimal to lethal conditions, we identify temporal fluctuations in the extent of optimal habitats. We anticipate that a more pronounced warming-cooling-warming amplitude exacerbates challenges for the considered species, such that northern habitats are threatened more than southern habitats. We analyse this potential north-south divide in terms of economic and ecological consequences.