Evolution of 21st Century Sea-level Rise Projections

TL;DR

This paper reviews the evolution of 21st century sea-level rise projections, highlighting how estimates have changed over time and discussing the uncertainties and methodological differences influencing these projections.

Contribution

It compiles a comprehensive database of sea-level rise projections to analyze historical trends and methodological variations over four decades.

Findings

Range of upper projections shrank in the 2000s and expanded since 2013.

Upper projections are generally higher than IPCC estimates.

Uncertainty in future sea-level rise remains significant.

Abstract

The modern era of scientific global-mean sea-level rise (SLR) projections began in the early 1980s. In subsequent decades, understanding of driving processes has improved, and new methodologies have been developed. Nonetheless, despite more than 70 studies, future SLR remains deeply uncertain. To facilitate understanding of the historical development of SLR projections and contextualize current projections, we have compiled a comprehensive database of 21st century global SLR projections. Although central estimates of 21st century global-mean SLR have been relatively consistent, the range of projected SLR has varied greatly over time. Among studies providing multiple estimates, the range of upper projections shrank from 1.3 to 1.8 m during the 1980s to 0.6 to 0.9 m in 2007, before expanding again to 0.5 to 2.5 m since 2013. Upper projections of SLR from individual studies are generally higher than upper projections from the Intergovernmental Panel on Climate Change, potentially due to differing percentile bounds, or a pre-disposition of consensus-based approaches toward relatively conservative outcomes.