AMOC variability, a key factor in emission reduction scenarios

Abstract

The climate system response to emission reduction shows time dependencies when evaluated in terms of global mean sur- face temperature (GMST). The Atlantic meridional overturning circulation (AMOC) variability may be forcing a non-linear behaviour on GMST response to emission reduction. In this study, emission reduction is evaluated with eight starting actions times on three equilibrium climate sensitivities (ECS), using the PLASIM-GENIE intermediate complexity Atmosphere and Ocean global climate model. Under these CO2 reducing scenarios, AMOC collapses in six out of the twenty-four simulations performed. The effect of the AMOC collapse in the emission reduction scenarios is a transient faster response (cooling) in the short term compensates with a slower response to emission reduction in the forthcoming decades. In non-collapsing scenarios, the emission reduction response might have initial conditions dependencies with the AMOC variability.