ENSO as an Emergent Constraint on the Pattern Effect

Abstract As the spatial pattern of warming in sea surface temperatures evolves, it leads to changes in Earth's net radiative feedback and effective climate sensitivity. The magnitude of the change in feedback attributable to changes in regional temperature patterns is known as the “pattern effect”. This pattern effect has been mostly attributed to variability in low cloud radiative effect (CRE), and exhibits significant variance in models while being poorly constrained from observations. Here we use ENSO as an emergent constraint on the pattern effect. We find strong linear relationships between modeled ENSO feedbacks and their respective pattern effects, especially for net CRE. Observed ENSO feedbacks lie within the middle of the model ensemble and suggest a pattern effect magnitude of 1.00 +/- 0.35 W/m^2/K when calculated relative to preindustrial conditions. Model-simulated pattern effects also exhibit similar spatial distributions as the pattern diversity of ENSO, hinting at similar physics governing the two phenomena.