Sea Level Rise Under Overshoot

Sea Level Rise Under Overshoot (N-SLCT Technical Report 003) is a NASA Sea Level Change Team assessment of how global sea level responds when warming temporarily exceeds 1.5°C. It was written as a companion to UNEP’s Limiting Overshoot report.

Global temperature can come back down after an overshoot, but sea level does not. The report describes sea level rise in three stages. The first is observed rise: satellite altimetry shows the rate has more than doubled since 1993, from 2.1 to 4.3 mm per year. The second is locked in rise: another 10 to 15 cm of global rise by 2050 is largely set regardless of emissions pathway, and observations and model projections agree to within about 3 cm. The third is rise that is yet to unfold: beyond 2050, the amount depends on how high warming peaks and how long it stays elevated. Higher or longer overshoot raises the risk of irreversible changes in the ice sheets and ocean circulation.

The report gives particular attention to Pacific Island nations and other Small Island Developing States, where the effects of sea level rise are already being felt. It concludes that limiting overshoot now delivers benefits that last for centuries.