Observations confirm projected global mean and regional sea-level trends and accelerations — Australian Meteorological and Oceanographic Society
  1. Schedule
  2. 24(i). Southern Hemisphere oceans variability and change
  3. Observations confirm projected global mean and regional sea-level trends and accelerations

Observations confirm projected global mean and regional sea-level trends and accelerations (#7)

JINPING WANG 1 2 , John A. Church 3 , Xuebin Zhang 2 , Xianyao Chen 4
  1. College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao, Shandong, China
  2. Centre for Southern Hemisphere Oceans Research (CSHOR), CSIRO Oceans and Atmosphere, Hobart, TAS, Australia
  3. Climate Change Research Centre, University of New South Wales, Sydney , NSW , Australia
  4. Physical Oceanography Laboratory, CIMST, Ocean University of China, and Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong, China

The ability of climate models to simulate historical global mean sea level (GMSL) and regional sea-level change since 1900 has been demonstrated1 and the majority of the GMSL rise since 1970 is a result of anthropogenic climate change. However, evaluation of sea-level projections with observations has not been rigorously completed, as the common data period (2007-2018) is short. Here, we evaluate the trend and acceleration of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5)2 sea-level projections with satellite and tide-gauge observations, after minimising the impacts of natural climate variability and correcting for local vertical land motion (VLM). For GMSL, the satellite trend (3.8 ± 0.5 mm yr-1) is consistent with projected trends under three Representative Concentration Pathway (RCP) scenarios (3.9 ± 0.6, 3.8 ± 0.5 and 3.9 ± 0.6 mm yr-1 under RCP2.6, 4.5 and 8.5 respectively)2 during the overlapping period 2007-2018. The observed acceleration over 1993-2018 (0.051 ± 0.051 mm yr-2) agrees with the projections under three RCPs over 2007-2032 within uncertainty range (0.035 ± 0.049, 0.048 ± 0.047 and 0.069 ± 0.048 mm yr-2 under RCP2.6, 4.5 and 8.5 respectively). For 177 tide gauges globally, the weighted mean observed regional trend (3.6 mm yr-1) over all tide stations is similar to the corresponding projections over 2007-2018. The majority of tide-gauge records (81%) have accelerations over 1970-2018, with their weighted mean value (0.066 mm yr-2) lying between the RCP4.5 and RCP8.5 projections, consistent with the observed ongoing growth in green-house gas emissions and the GMSL acceleration. The significant decelerations at four gauges are likely related to nearby regions of accelerating glacier mass loss or changes in groundwater extraction. The results indicate the importance of global mean and regional sea-level projections for future mitigation and adaptation decisions.

  1. Church, J. A., Monselesan, D., Gregory, J. M. & Marzeion, B. Evaluating the ability of process based models to project sea-level change. Environ. Res. Lett. 8, 014051 (2013).
  2. Church, J. A. et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) Ch. 13 (IPCC, Cambridge Univ. Press, 2013).
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