One of the more insidious dangers of climate change is rising sea level. With so much of human society concentrated near oceans around the world, even small local increases in sea level could have disastrous consequences.
That’s why Professor Andrew Parnell is examining sea-level past and present in Dublin and at points around the world, and he is using the power of statistical analysis to help predict the rate of future change. Professor Parnell, who is Hamilton Professor at Maynooth University, has analysed data from lake sediments (which can tell us about where the sea was in the past) and historical records from tide gauges at various points in North America, but the data are messy and noisy, and this is where powerful methods in statistics can help to see the key patterns.
“Throughout the 20th century we can see a 1.7mm rise per year in global sea level - which was bad - but in the last 20 years or so, that has risen to 3.3mm per year. Those numbers may not sound much, but even a small change in sea level is magnified locally by tides and storms, so it can cause a lot of damage.”
“We use a technique in statistics called Gaussian processes, which is used in machine learning and Artificial Intelligence and it allows you to add in multiple types of data,” explains Professor Parnell. “That means we can examine data from fossils, from tide gauges and from other sources such as satellites and apply fancy maths to calculate rates of change with less uncertainty.”
He and his team at Maynooth are now applying the techniques to the A4 (Aigéin, Aeráid, agus athrú Atlantaigh) project led by Dr Gerard McCarthy to measure sea-level change in Ireland, and they are part of the PREDICT project, which is supported by SFI, to better understand environmental changes in Dublin Bay.
“One of the current questions we are looking at is why one of the tide gauges along the Liffey is showing an enormous rise in water level, as much as 10 times the global average,” he says. “This is in contrast to the measurements at Howth, which are much less dramatic, so we want to see is there some environmental factor in the Liffey that could be having an effect.”
By gathering and understanding information at local, national and international levels, Professor Parnell hopes to build a more realistic picture of sea-level rise. “When you analyse the numbers, it’s sobering to see the changes, and the statistics we are using will allow us to work out the rate of change into the future, which is very important to know.”