I have written previously about sea level rises [see ‘Merseyside Totemy‘ on August 17th, 2022 and ‘Climate change and tides in Liverpool‘ on May 11th, 2016] and the fact that a 1 metre rise in sea level would displace 145 million people [see ‘New Year resolution‘ on December 31st, 2014]. Sea levels globally have risen 102.5 mm since 1993 primarily due to the water added as a result of the melting of glaciers and icecaps and due to the expansion of the seawater as its temperature rises – both of these causes are a result of global warming resulting from human activity. I think that this is probably well-known to most readers of this blog. However, I had not appreciated that the polar ice caps are sufficiently massive that their gravitational attraction pulls the water in the oceans towards them, so that as they melt the oceans move towards a more even distribution of water raising sea levels further away from the icecaps. This is problematic because the population density is higher in the regions further away from the polar ice caps, as shown in the image. Worldwide about 1 billion people, or about an eighth of the global population, live less than 10 metres above current high tide lines. If we fail to limit global warming to 1.5 degrees Centigrade and it peaks at 5 degrees Centigrade then the average sea level rise is predicted to be as high as 7 m according to the IPCC.
Image: Population Density, v4.11, 2020 by SEDACMaps CC-BY-2.0 Creative Commons Attribution 2.0 Generic license.
Source: Thomas Halliday, Otherlands: A World in the Making, London: Allen Lane, 2022