Rising Sea Levels – by How Much, and Why? A Current Commentary.
The following was published in the journal Science Progress recently, of which I am an editor. Since this blog typically covers issues of environment and energy, I am including the present topic, which I hope will be of interest to its regular readers, and indeed to anyone else with concerns about the direction of “the changing climate”.
Introduction.
The term “sea level rise” normally refers to an increase in the global mean sea level (GMSL), caused by an increase in the volume of water in the Earth’s oceans, primarily as a result of thermal expansion, the addition of further water from the melting of land-based ice sheets and glaciers, and to a smaller degree from changes in land-water storage, including the transfer of groundwater that has been pumped from aquifers1. As measured on the local scale (Section 4), sea levels may be higher or lower than the global mean value, as a result of various factors, including land subsidence, glacial rebound, tectonic effects, and the influence of currents, local temperatures, winds, tides, storms, and variations in local barometric pressure2 among the particular locations where the measurements are being made. There is strong evidence that the GMSL is increasing, and as a result of long response times from various components of the climate system, this process may continue over the course of centuries3. It has been estimated that more than half of the observed sea level rise during the 20thcentury was due to global warming4. According to satellite altimetry measurements, the GMSL is currently5,6 increasing by 3.2 ± 0.4 mm yr-1, which is about double the rate determined to have prevailed throughout the 20th century6, and it has been predicted that, for each degree Celsius rise in the mean global temperature (MGT), over the next two millennia an increase in the GMSL of at least 2.3 m can be expected7.
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