Tag Archives: tides

Merseyside Totemy

The recent extreme weather is perhaps leading more people to appreciate the changes in our climate are real and likely to have a serious impact on our way of life [see ‘Climate change and tides in Liverpool‘ on May 11th, 2016].  However, I suspect that most people do not appreciate the likely catastrophic effect of global warming.  For example, during the 20th century, the average rise is sea level was 1.7 mm per year; however, since the early 1990s it has been rising at 3 mm per year, and sea levels are currently rising at about 4mm per year according to the Intergovernmental Panel on Climate Change.  It is difficult to translate  statistics of this type into a meaningful format – the graph below helps in recognising the trends but does not convey anything about the impact.  However, I am impressed by a new art installation on the Liverpool waterfront by Alicja Biala called ‘Merseyside Totemy’ which illustrates the percentage of each of three high-risk local areas that will be underwater by 2080 if current trends continue: Birkenhead (centre of photograph), Formby (left) and Liverpool City Centre (right behind tree) [see www.biennial.com/collaborations/alicjabiala].  Perhaps using data for 30 years time rather than 60 years would have focussed people’s attention on the need to make changes to alleviate the impact.

Figure 1 from

Figure 1. Time series of global mean sea level (deviation from the 1980-1999 mean) in the past and as projected for the future. For the period before 1870, global measurements of sea level are not available. The grey shading shows the uncertainty in the estimated long-term rate of sea level change. The red line is a reconstruction of global mean sea level from tide gauges, and the red shading denotes the range of variations from a smooth curve. The green line shows global mean sea level observed from satellite altimetry. The blue shading represents the range of model projections for the SRES A1B scenario for the 21st century, relative to the 1980 to 1999 mean, and has been calculated independently from the observations. Beyond 2100, the projections are increasingly dependent on the emissions scenario. Over many centuries or millennia, sea level could rise by several metres. From https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/faq-5-1-figure-1.html

Climate change and tides in Liverpool

image-20141201-20565-1eoo7rhIf you live within sight of the sea, as we do, then your life is probably influenced, to some degree, by the rise and fall of tides.  In Liverpool, we are lucky to have a particularly long historical record of tidal heights and one of my colleagues, an oceanographer, Professor Ric Williams has used this record to discuss climate variability.  The record was started and maintained between 1768 and 1793 by Captain William Hutchinson whose achievement is commemorated with a fountain in Liverpool’s historic docks, which are a UNESCO World Heritage Site.

A few weeks ago I listened to a talk by Prof Williams, in which he described how there is a rather simple relationship between surface warming and the effect of future emissions of greenhouse gases.  If the predictions of surface warming are plotted as a function of how much carbon is emitted to the atmosphere, rather than time, then a simple response emerges: the more carbon we emit, the warmer it will get. Associated with the surface warming, there is an expected sea level rise from the expansion of the water column augmented by the effect of addition of freshwater from melting of land ice. Watch Prof Williams’ Youtube video to find out more.

Sources:

Woodworth, P.L. 1999. High waters at Liverpool since 1768: the UK’s longest sea level record. Geophysical Research Letters, 26 (11), 1589-1592.

Goodwin, P., Williams, R.G. & Ridgwell, A., Sensitivity of climate to cumulative carbon emissions dues to compensation of ocean heat and carbon uptake, Nature Geoscience, 8,29–34(2015).

Image: http://theconversation.com/our-equation-proves-climate-change-is-linked-to-emissions-34897