The main factors that can cause an average sea level rise are the thermal expansion of the oceans, the melting of ice sheets and the change in salinity due to the exchange of water masses between the oceans and the freshwater reserves of the territory.
These contributions are commonly attributed to a global climate change induced largely by anthropogenic inputs of greenhouse gases. The absolute sea level also indirectly depends on the deformation of the solid earth. The acceleration experienced by the thermal expansion of the oceans and the melting of glaciers and ice caps in recent decades is linked to the massive input by humans of greenhouse gases into the atmosphere, causing warming.
The scientific community is in fact now unanimous in attributing the cause of the warming and therefore also of the recent rise in sea level to human activities.
Sea-level changes from global to local scales
The study Contemporary sea-level changes from global to local scales: a review, published in the Proceedings.
Mathematical, physical, and engineering sciences, said us: "Sea-level variations spread over a very broad spectrum of spatial and temporal scales as a result of complex processes occurring in the Earth System in response to natural variability of the climate system, as well as to external forcing due to natural phenomena and anthropogenic factors.
Here, we address contemporary sea-level changes, focusing on the satellite altimetry era (since the early 1990s), for which various observing systems from space and in situ allow precise monitoring of sea-level variations from global to local scales, as well as improved understanding of the components responsible for the observed variations.
This overview presents the most recent results on observed global and regional sea-level changes and on associated causes, focusing on the interannual to decadal time scale.Recent progress in measuring sea level at the coast are presented.Finally, a summary of the most recent sea-level projections from the Intergovernmental Panel on Climate Change is also provi ded." Sea level can also be used as zero point for determining altitudes.
By convention, the height above the sea of a municipality is measured from the churchyard of the highest church or from the main square of the place or from the seat of the town hall. Of the three eventualities mentioned, the most certain appears to be the location of the square.