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The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the global climate that is projected to weaken under future anthropogenic climate change. While many studies have investigated the AMOC’s response to different levels and types of forcing in climate models, relatively little attention has been paid to the AMOC’s sensitivity to the rate of forcing change, despite it also being highly uncertain in future emissions scenarios. In this study, I isolate the AMOC’s response to different rates of CO2increase in a state-of-the-art global climate model and find that the AMOC undergoes more severe weakening under faster rates of CO2change, even when the magnitude of CO2change is the same. I then propose an AMOC-ocean heat transport-sea ice feedback that enhances the decline of the circulation and explains the dependence on the rate of forcing change. The AMOC’s rate-sensitive behavior leads to qualitatively different climates (including differing Arctic sea ice evolution) at the same CO2concentration, highlighting how the rate of forcing change is itself a key driver of global climatic change.
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Decreased northern hemisphere precipitation from consecutive CO 2 doublings is associated with significant AMOC weakening
Abstract Previous studies found many climate properties such as northern hemisphere (NH) surface temperature and precipitation respond non-monotonically when CO2is increased from 1×to 8×CO2relative to pre-industrial levels. Here, we explore the robustness of the non-monotonicity in the NH precipitation response in 11 coupled climate models. Eight models show a decrease in NH precipitation under repeated CO2doubling, indicating that the non-monotonic response is a common but not universal result. Although common, the critical CO2level where the NH precipitation decrease first occurs differs widely across models, ranging from 2×CO2to 8×CO2. These models also show a prominent weakening in the Atlantic meridional overturning circulation (AMOC) at the same critical CO2level, with the AMOC weakening leading the precipitation decrease. The sensitivities of NH precipitation and the AMOC to CO2doublings are positively correlated, especially when the AMOC weakens beyond 10 Sv. This suggests that the differences in models’ AMOC response can explain their contrasting NH precipitation responses, where models with a large AMOC weakening have decreased NH precipitation. Regionally, this decrease in NH precipitation is the most prominent over the North Atlantic, Europe and the tropical Pacific. Our results suggest that special care must be taken with the use of pattern scaling to inform regional climate decision-making.
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- Award ID(s):
- 2335761
- PAR ID:
- 10557255
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Environmental Research: Climate
- Volume:
- 3
- Issue:
- 4
- ISSN:
- 2752-5295
- Format(s):
- Medium: X Size: Article No. 041005
- Size(s):
- Article No. 041005
- Sponsoring Org:
- National Science Foundation
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