The rate of global sea level rise doubled during the past three decades

Background

Tracking global mean sea level (GMSL) is important for both global climate monitoring and informing coastal communities’ adaptation strategies. Previous methods of tracking GMSL calculate the average rate of GMSL rise to be 3.3 mm/year based on satellite data over 30 years. However, studies since 2017 have identified a significant acceleration in GMSL rise. Thus, it is important to ensure that current GMSL rate estimates are accurate to inform both local and GMSL rise adaptation strategies. 

Goals and Methods

The authors plotted a GMSL time series using data from the Integrated Multi-Mission Ocean Altimeter Data for Climate Research, which combines observations of sea surface height from multiple satellite missions. They used statistical methods to estimate the rate, acceleration, error, and confidence limits of this time series. The extrapolated confidence limits were compared to different sea level rise scenarios from the IPCC (Intergovernmental Panel on Climate Change) 6th Assessment Report to see which scenarios best match the projections from the observed data.

Conclusions and Takeaways

This study documents that GMSL has risen by 111 mm from 1993 to 2023, with the rate of GMSL rise increasing from 2.1 mm per year at the beginning of 1993 to 4.5 mm per year at the end of 2023. The rate of GMSL rise has more than doubled over the 31-year satellite record, and it is projected to increase further in the coming decades (i.e., 5.0 mm per year by 2030, 5.8 mm per year by 2040, 6.5 mm per year by 2050). Extrapolating the current trajectory of GMSL projects an increase of GMSL by more than 169 mm in the next 30-year period. This scenario most closely aligns with the IPCC’s intermediate or “Middle of the Road” climate scenario, providing coastal communities and governing bodies a target for coastal adaptation efforts.