Monday, January 27, 2014, 4:00PM - 5:00PM
ARC room 620
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 general circulation models (GCMs) diverge strongly in projections of future warming, most strikingly within polar regions. This inter-model spread is due, in part, to different representations of how climate sensitivity (set by feedbacks linking surface warming to top-of-atmosphere radiative response) varies over time. I use a range of climate models, of varying degrees of complexity, to investigate the mechanisms governing time variation of climate sensitivity, and discuss implications for climate prediction. Within fully-coupled GCMs, I show that climate sensitivity depends fundamentally on the geographic patterns of radiative feedbacks and surface warming, and thus it naturally varies in time as the pattern of warming evolves, activating feedbacks of different strengths in different regions. An oceanic GCM is used to quantify the ocean’s role in setting the patterns of transient surface warming, while a variety of idealized atmospheric GCMs are used to explore global and regional climate implications of different spatial patterns of ocean heat uptake. Results suggest that the ocean cannot be thought of as a passive, global heat sink under warming, and instead plays a dynamic role in regulating transient climate change through its regional-scale coupling to atmospheric feedbacks.