Rising Sea Levels and Changing Coastlines

Moving on (at least for the moment) from thinking about river and freshwater flooding I want to reflect on where we are heading in terms of coastal change, rise in sea levels and the impacts this will have on all of us, wherever we are geographically. Sea level rise is not and should not be an issue just for coastal communities. It is an issue in which we all have a stake and should all take note of in moving forward.

Quite recently, a number of papers were published in the Proceedings of the National Academy of Sciences (USA) (see reference list below) which suggested that global sea levels are rising at unprecedented levels and indeed, faster than previously expected. Oceanic thermal expansion as well as ice melt are both contributing to such rise and we are at a point when continued melting is inevitable. All in all, the consensus is that sea levels could rise as much as 3 feet (c.91cm) by 2100 which could have immense political and social consequences.

Past rises in levels are clear. In 2014 the Intergovernmental Panel on Climate Change (IPCC) issued their 5th Assessment Report (AR5) in which they suggested that the mean rate of global average sea level rise was 1.7 mm/yr between 1901 and 2010 and 3.2 mm/yr between 1993 and 2010 (IPCC, 2014). Whilst researching for my recent book about the Naze in Essex I took a keen interest in the topic of sea level rise, partly because the story of the Naze is so intimately connected with the changing coastline and the sea itself. I have experienced first hand the increase in surge tides at the site in recent years and the consequences that has in terms of land management on a small scale. I also saw how the IPCC predictions have gradually changed through the years. The figures in the fourth assessment report (AR4) suggested a rise of anything up to 44cm by 2090 (IPCC, 2007) whereas the fifth assessment suggested anything between 42cm and 98cm by 2100, depending on the scenario (IPCC, 2014). It is true that different areas of the globe are experiencing different figures principally due to fluctuations in ocean circulation. Since 1993, the regional rise rates for the Western Pacific are up to three times larger than the global mean, while those for much of the Eastern Pacific are near zero or negative (IPCC, 2014). Nonetheless the trend is the same and that is – upwards movement.

In the TEDx clip placed at the beginning of this post (if you haven’t already watched it, maybe watch it now) oceanographer John Englander makes it clear that this isn’t a problem that is going to go away. As a civilisation we may have a few hundred or a few thousand years to adapt to it but adapt to it we must. Coastal areas will face immense change geographically, settlements will be abandoned or physically moved and the impacts will be felt inland as the economic and social consequences begin to present themselves.

The other Tedx talk is from Benjamin P. Horton, professor at the Institute of Marine and Coastal Sciences at the  State University of New Jersey, New Brunswick (see below). Horton presents the evidence and critically evaluates past and future scenarios. Note how in Horton’s figures global average rises of up to 2m are considered. His exploration is sobering but I think what is key is that we combine the elements of both talks. The adaptation message of Englander’s talk needs to be combined with the science of Horton’s.

As modern human societies we are generally incredibly poor at looking ahead ore than a few years. Our political systems (at least in the democratic world) are based around terms of a few years and our economies remain doggedly obsessed with the here and now. We don’t like the idea of jam tomorrow if we can at all possible get it today. Consequently anybody who takes a longer term view (and in this I include conservationists and climate scientists as well as most farmers) tends to have their opinion looked at but not seriously considered. The messages are usually dissipated and if acted upon at all, the measures of action are generally half-hearted. With sea level rise we are presented with a scenario that is coming our way whether we like it or not. The effects are measureable and we can prepare to adapt if we want to. It will involve some very tough political actions with difficult social consequences but I would suggest that the alternative consequences as a result of inaction are far worse.

References

Gasson, E., R.M. DeConto, D. Pollard, and R.H. Levy (2016), ‘Dynamic Antarctic ice sheet during the early to mid-Miocene’ in Proceedings of the National Academy of Sciences, Published online before print (February 22 2016) 

IPCC (2007), Fourth Assessment Report (AP4) 

IPCC (2014), Fifth Assessment Report (AP5) 

Kopp,R.E., A.C. Kempd , K. Bittermanne , B.P. Hortonb, J.P. Donnelly , W.R Gehrelsj, C.C. Haya, J.X. Mitrovicak, E.D. Morrowa, and S. Rahmstorfe (2016), ‘Temperature-driven global sea-level variability in the Common Era’ in Proceedings of the National Academy of Sciences, pp. 201517056 http://www.pnas.org/content/early/2016/02/17/1517056113.full.pdf

 Mengel, M., A. Levermann, K. Frieler, A. Robinson, B. Marzeion and R. Winkelmann (2016), ‘Future sea level rise constrained by observations and long term commitment’ in Proceedings of the National Academy of Sciences, 113, 10, 2597-2602, published ahead of print February 22, 2016,doi:10.1073/pnas.1500515113

Rietbroek, R., S.E. Brunnabend, J. Kusche, J. Schroter and C. Dahle (2016), ‘Revisiting the contemporary sea-level budget on global and regional scales’ in Proceedings of the National Academy of Sciences, 113, 6 (6 Feb 2016).

 

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