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Title: Non‐Monotonic Feedback Dependence Under Abrupt CO 2 Forcing Due To a North Atlantic Pattern Effect

Effective climate sensitivity (EffCS), commonly estimated from model simulations with abrupt 4×CO2for 150 years, has been shown to depend on the CO2forcing level. To understand this dependency systematically, we performed a series of simulations with a range of abrupt CO2forcing in two climate models. Our results indicate that normalized EffCS values in these simulations are a non‐monotonic function of the CO2forcing, decreasing between 3× and 4×CO2in CESM1‐LE (2× and 3×CO2in GISS‐E2.1‐G) and increasing at higher CO2levels. The minimum EffCS value, caused by anomalously negative radiative feedbacks, arises mainly from sea‐surface temperature (SST) relative cooling in the tropical and subtropical North Atlantic. This cooling is associated with the formation of the North Atlantic Warming Hole and Atlantic Meridional Overturning Circulation collapse under CO2forcing. Our findings imply that understanding changes in North Atlantic SST patterns is important for constraining near‐future and equilibrium global warming.

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Author(s) / Creator(s):
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Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Geophysical Research Letters
Medium: X
Sponsoring Org:
National Science Foundation
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