A comprehensive assessment of socioeconomic impacts of global sea level rise on coastal zones

Global sea level rise caused by climate change is not uniform geographically, which emphasizes the importance of considering relative sea level (RSL) when assessing the risks associated with sea level rise for different regions and scales. However, our understanding of the impacts of relative sea level on coastal zones is still limited since lacking information on relative sea-level change (RSLC) at a high resolution. To address this, we combined VLM from the Global Navigation Satellite System and global mean sea-level trend measured by satellite altimetry to produce global RSL velocity in 0.25-degree spatial resolution during 1993-2022. Our research finds that, 99.30% of the regional RSL rise over the past three decades has been dominated by ocean mass increase and thermal expansion, that is, absolute sea level rises faster than vertical land motion velocity. Besides, the global mean RSL has risen over the past three decades to 2.03mm/yr. Moreover, the average RSL rise rate of tropical island nations is approximately 2.25 times faster (3.75mm/yr) than non-island countries (1.66mm/yr). Additionally, the average RSL rise rate of the Global South (3.53mm/yr) is nearly 12 times higher than that of the Global North (0.30mm/yr). Coastal cities in the Global South, experiencing large population density and significant economic growth, are facing a heightened risk of RSL rise during development, exacerbating existing inequality between the Global North and South and emphasizing the urgent need for sustainable development and adaptation strategies in the Global South.