The global warming ‘hiatus’ and its implications on future sea level rise

Tuesday, 16 December 2014
Veronica Nieves, Josh K Willis and William C Patzert, Jet Propulsion Laboratory, Pasadena, CA, United States
Global sea level rise is one of the most direct and potentially costly impacts of human caused global warming. It is driven by both melting glaciers and ice sheets (which react to the warming atmosphere and ocean), and direct absorption of heat by the oceans. In fact, over 90 percent of the excess heat trapped by greenhouse gases warms the oceans, causing thermal expansion and sea level rise. For this reason the recent warming “hiatus”, or slowdown in the rate of global surface temperature increase, may play an important role in ongoing and future sea level rise. Recent studies based on ocean reanalyses have suggested that the low rate of warming at the ocean surface (which is nearly identical to the rate of global surface temperature increase) is compensated by more rapid warming at depth. We analyzed ocean in situ observations and satellite measurements of sea level independently of these reanalyses, and compared the most recent decade with prior decades to determine whether warming at depth was faster in the past. We find little to no evidence for an increase of the rate of ocean warming at depth in the most recent decade. Our analysis suggests that a weaker external forcing trend might be a stronger key component than the interior exchange in the coupled feedback.