Increased greenhouse gas concentrations have brought about an imbalance in Earth’s energy budget that is driving anthropogenic global warming. Well-documented impacts of climate change – including global surface temperature rise, reductions in snow and ice cover, and sea level rise – are the symptoms of Earth’s Energy Imbalance (EEI). The vast majority (>90%) of this excess energy is absorbed by the ocean, with much smaller amounts going into heating of the land, atmosphere and ice cover. Building on recent advances in the satellite and ocean in situ observing systems, the climate community is calling for sustained and improved measurements of EEI to advance our understanding of global climate variability and change. In the first part of this talk I will review the recent science, challenges and observational developments crucial to refining estimates of EEI.
The most direct result of the planetary energy imbalance is increasing ocean heat content, which makes a substantial (~ 40%) contribution to global sea level rise via thermal expansion. This change is exacerbated by mass input to the oceans from melting glaciers and ice sheets. For regional sea level rise, additional processes, such as changes in ocean circulation and vertical land motion can play an important role. In the second part of this talk I will review the science of global and regional sea level change with particular focus on projections over the 21st Century and highlight the very different climate response compared to global surface temperature.