Non‐Monotonic Response of the Climate System to Abrupt CO ₂ Forcing

We explore the climate system response to abrupt CO2 forcing, spanning range 1× 8×CO2, with two state-of-the-art coupled atmosphere-ocean-sea-ice-land models: NASA Goddard Institute for Space Studies Model E2.1-G (GISS-E2.1-G) and Community Earth System (CESM-LE). find that effective sensitivity is a non-monotonic function of in both models, reaching minimum at 3×CO2 GISS-E2.1-G, 4×CO2 CESM-LE. A similar found Northern Hemisphere surface temperature, sea-ice, precipitation, latitude zero precipitation-minus-evaporation, strength Hadley cell. Interestingly, Atlantic meridional overturning circulation collapses when non-monotonicity appears does not recover larger forcings. Analyzing over same slab-ocean versions we demonstrate system’s linked ocean dynamics.