Abstract
It is well established that a collapse or strong reduction of the Atlantic meridional overturning circulation (AMOC) would substantially cool the northern high latitudes. Here we show that there is a possibility that such cooling could be amplified under deliberate CO2 removal and result in a temporary undershoot of a targeted temperature level. We find this behaviour in Earth system models that show a strong AMOC decline in response to anthropogenic forcing. Idealized simulations of CO2 removal with one of these models indicate that the timing of negative emissions relative to AMOC decline and recovery is key in setting the strength of the temporary cooling. We show that the pronounced temperature-fluctuations at high northern latitudes found in these simulations would entail considerable consequences for sea-ice and permafrost extent as well as for high latitude ecosystems.
Highlights
It is well established that a collapse or strong reduction of the Atlantic meridional overturning circulation (AMOC) would substantially cool the northern high latitudes
Since the Paris agreement entered into force in 2016, global anthropogenic carbon dioxide emissions have increased by 5% (0.58 Pg C between 2016 and 2019)[1], in stark contrast to the fact that net zero CO2 emissions are required by around 2050 to meet a 50% chance of keeping the average surface temperature increase to below 1.5 °C2
The phase of positive emissions is limited to 100 years, which is substantially shorter than the period from 1850 to 2100 usually covered in historical and scenario simulations with Earth system models (ESMs)
Summary
It is well established that a collapse or strong reduction of the Atlantic meridional overturning circulation (AMOC) would substantially cool the northern high latitudes. These results suggest that northern high-latitude cooling that is seen when emissions are phased out and that is caused by a strong reduction of AMOC can be amplified if CDR is applied subsequently.
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