Sack Lunch Seminar (SLS)

Abstract:
While great efforts have been made to constrain Earth’s climate sensitivity, this global and equilibrium metric provides only limited understanding of transient and regional changes over the coming centuries. Indeed, pronounced spatial and temporal variability of climate change has been observed, and models diverge strongly in transient climate projections even while simulating similar levels of equilibrium warming. Here I discuss new perspectives on the important role of the ocean in setting the pace of global and regional climate changes. Using a range of climate models of varying degrees of complexity, I show that (i) large-scale ocean circulations fundamentally shape the geographic patterns of transient sea-surface warming and ocean heat uptake; (ii) Earth’s distinct climatic zones shape the geographic patterns of atmospheric radiative feedbacks (linking surface warming to top-of-atmosphere radiative response); and (iii) as the patterns of surface warming and ocean heat uptake evolve over time, feedbacks of different strengths are activated in different regions and Earth’s effective climate sensitivity consequently varies. The ocean thus cannot be viewed as a passive, global heat sink under warming; instead, ocean circulations play a fundamental and dynamic role in setting the pace of transient climate change through their regional-scale coupling to atmospheric feedbacks.