Sea levels around the globe are rising because of climate change. Temperatures in the atmosphere are going up because of greenhouse gas emissions, causing an increase in the melting of land-ice, and more importantly, raising the temperatures of the oceansâ€™ surface and even deeper waters. As water warms it expands and this is known in the climate and ocean science world as the 'thermal expansion' component of sea level rise in contrast to the land ice component.
Other processes play a role as well. A local lowering of air-pressure of 10 mbar (0.295301 inHG), can cause local sea level to rise up to 10 cm (nearly 4 inches). Changes in ocean-currents, and even changes in the distribution of floating ice-masses like those that are diminishing in the Arctic, can all contribute to variations in sea level rise around the planet.
As these factors vary from place to place sea level rise is not homogeneous (the same) around the planet; there are important local variations.
All these elements are modeled and expressed in the Global Climate Models (GCMs), that are publicly available from the Fifth Assessment Report (AR5) of the Intergovernmental Panel for Climate Change (IPCC). Based on the CMIP5-data (Coupled Model Intercomparison Project Phase 5), the results of 28 models are available and have been used to generate outputs in this app.
There is another critical and sometimes overlooked factor that determines how sea level rise is experienced locally. Land is not always stable but over short and longer periods of time can move up or down. This is usually a slow process but it can be abrupt as a result of an earthquake, but its magnitude can sometimes be comparable to sea level rise in terms of its impact. Thus when land rises, it lowers the rate of sea level rise experienced at that specific coastline, but when land sinks and this can be through tectonic shifts as well as through human induced processes of, for example, landuse change and groundwater extraction, it can exacerbate the local effects of sea level rise.
The app shows a global map of the combined processes of local (absolute) sea level rise and local vertical land movement. The sea level rise values are taken as the median value of an ensemble of 28 GCMâ€™s, under the assumption of the largest greenhouse gas emissions as described by the RCP8.5 scenario in AR5. It also assumes a high climate sensitivity. Both assumptions are made to allow analysis of future impacts from the higher end of the emission concentration pathways which are consistent with current trends in greenhouse gas emissions.
The vertical land movement values were generated from direct observations through continuous GPS (Global Positioning Systems used by the the SONEL program), and from trend analysis of tidal observations (the PSMSL program).
When a location is clicked on the map, the App shows a ruler with five future years (2020, 2040, 2060, 2080 and 2100) and the sea level rise at these years compared to the baseline year of 1995.