Ocean Heat Uptake Shapes the Pace-And Persistence-Of Climate Warming

April 30, 2026

Emily Newsom

Hosted by Maria Rugenstein

Abstract

The global ocean absorbs most excess heat from greenhouse gas forcing, yet how that uptake governs surface warming from decades to centuries remains unclear. We use ocean heat uptake efficiency (OHUE)—the ratio of ocean heat uptake to global-mean surface temperature change—as a diagnostic of the ocean’s capacity to transport and store heat at depth, and link OHUE variations to ocean dynamics and long-term climate commitment. On multi-decadal timescales, the depth of heat penetration—and thus OHUE—is set mainly by mid-latitude ventilation and upper-ocean stratification. Inter-model differences in OHUE thus map closely to climatological subtropical pycnocline depth. To probe the fate of sequestered heat, we run an idealized abrupt-mitigation experiment that removes radiative forcing and isolates the release of interior, “recalcitrant” heat. In this post-forcing regime, the re-emergence of recalcitrant heat drives residual warming for centuries. However, the efficiency of its return to the surface is roughly halved relative its downward penetration in the forced state—revealing a key asymmetry: heat is taken up at depth far more readily than it is released. Framed in a simple surface energy balance, the magnitude of post-forcing warming depends on the system’s degree of equilibration when forcing stops, quantified by the realized warming fraction (RWF). RWF is largely governed by “ocean pacing”—the ratio of OHUE to the equilibrium climate feedback—a quantity observable from surface fields and predictive of deep-ocean heat content. These results underscore the central role of ocean processes in shaping both transient warming and long-term climate commitment.