Sea Level to Rise by 1.2 Metres by 2300 – So What?

Guest essay by Andi Cockroft

Firstly let me say that I am not one of the most technical writers you will see here. I regard myself pretty much as a layman despite studying Geology, Mathematics and Computer Science at University.

So you won’t find all the references to papers (well not many), nor exact scientific formulae. I simply write what I have logically deduced. For any who disagree, or have value to add, please use the Comments below.

So my stance is “SO WHAT”!

Published recently in Nature here, is a peer-reviewed paper entitled “Committed sea-level rise under the Paris Agreement and the legacy of delayed mitigation action”

Abstract:-

Sea-level rise is a major consequence of climate change that will continue long after emissions of greenhouse gases have stopped. The 2015 Paris Agreement aims at reducing climate-related risks by reducing greenhouse gas emissions to net zero and limiting global-mean temperature increase. Here we quantify the effect of these constraints on global sea-level rise until 2300, including Antarctic ice-sheet instabilities. We estimate median sea-level rise between 0.7 and 1.2 m, if net-zero greenhouse gas emissions are sustained until 2300, varying with the pathway of emissions during this century. Temperature stabilization below 2 °C is insufficient to hold median sea-level rise until 2300 below 1.5 m. We find that each 5-year delay in near-term peaking of CO2 emissions increases median year 2300 sea-level rise estimates by ca. 0.2 m, and extreme sea-level rise estimates at the 95th percentile by up to 1 m. Our results underline the importance of near-term mitigation action for limiting long-term sea-level rise risks.

I still say “SO WHAT”

And, it seems sea-level rise is selective, perhaps owing to El-Nino events piling up water in the western Pacific:

As a post-war child, growing up in North England, I well remember the days of Rationing (at least the tail-end of it that involved sweeties), spending Farthings and all fine days were outside. I remember being allowed out in the snow for only one day after which it was black with the soot from the satanic mills 30 miles away.

I remember tramping the miles to school through many feet of snow just to get there and find school had been cancelled.

I remember the holidays at the seaside – usually on England’s North West Coast at Blackpool or Morecambe.

I remember riding donkeys on the beach, eating candy-floss (is that cotton-candy?), and paddling in the frigid waters of the Irish Sea. Blackpool Rock, the Fun Fair, the Trams and most spectacularly the Blackpool Illuminations

But even today, I know (so they tell me), that sea-level has risen over 150mm during the past 50 years – but everything remains as I remember it. The tide still comes to the same place in Blackpool. Floods are no better and no worse than they were back then.

When a Nor-Wester comes through, waves can be many metres – wiping out all trace of a meagre 150mm supposed rise.

So In my lifetime, I can’t for the life of me see through personal physical observation that anything has changed.

Again, my memory is working overtime, and for a while during the early 80’s, I worked in Central London on The Embankment in a large multi-storey office-block. Now whoever designed the computer facilities decided that since The Embankment was prone to occasional flooding (esp. 1953), so quite rightly installed the Main-Frame computers on the 3^rd floor – very smart indeed.

Sadly they forgot about the power supply. In those days, main-frames required a very stable power supply without spikes or fluctuations. Most had some smoothing applied to them – In this instance, large “Smoothing Inverters” were installed to ensure the energy was clean. And of course in those days smoothing inverters weren’t the modern solid-state devices we have today, rather they were mechanical devices requiring a large motor turning an attached generator. The idea being the motor would handle any spikes and fluctuations and the generator component would create a nice clean energy source. Not very efficient mechanically or electrically but very good at their intended role.

Shame they had been installed in the basement, so when the first minor flooding took place……..

Only a few years later, the Thames barrier would be constructed and the flood protection through the City raised to prevent further inundations. The Thames Barrier has an expected useful life till around 2030 at least. So for now The Embankment is safe.

Now it’s also true that I moved to New Zealand in the late 1980’s, and I have become much more interested in revising my University interest in geology, simply because one’s attention tends to be periodically and dramatically drawn to the fact that GodZone is tectonically very active. The recent quakes that started with a less well remembered Canterbury event in 2010, with the big tragedy in Christchurch almost exactly 7 years ago where 185 people died. This was followed by Seddon in 2013 and then Kaikoura in late 2016 – and it seems Kaikoura “wasn’t the big one”! All these have me wondering if quakes along the main north-south fault aren’t moving in a progressively northerly direction. Is Wellington next?

But concentrating on GodZone for a while, simply because I know it – although similar “local” effects can and should be investigated all over the globe.

Here though, if the major Hikurangi plate subduction zone that stretches almost the full length of the North Island and part way down the South were to rupture, a magnitude 9 is predicted. Tsunamis would be not only significant, but massive.

As it is, the Kaikoura quake lifted the seabed and coastal areas by up to 2 metres. OK, so it seems to me that Kaikoura is safe from 1.2 metres sea-level rise even if no further uplifting occurs!

See from this map post Kaikoura that not only has vertical movement taken place, but significant horizontal displacement as well. GodZone is indeed a restless place!

Now doesn’t this really mean that sea-level rise is purely a localised event and not to be interpreted globally? Seems logical to me.

Around GodZone, places are rising and places are falling – it is generally related to which Tectonic Plate they sit on – Australia to the West – Pacific to the East.

Dotted around GodZone’s capital Wellington, are small plaques embedded in the pavements simply stating “Shoreline 1840”. These make no real sense at first sight since they are hundreds of metres if not kilometres from the nearest seafront.

But in 1855, an 8.2-magnitude earthquake struck the Wellington region. It lifted the Rimutaka ranges to the north by six metres, caused a 4m-high tsunami in Wellington harbour and uplifted the north-western side of Wellington, up to 1.5m in places.

This created much needed new lands. Wellington’s Airport sits on land uplifted in 1855. And the area continues its relentless march to the skies. So will 1.2 metres sea-level rise bother Wellington? Doesn’t look likely to me.

From: R.J. Beavan N.J. Litchfield (2012) Vertical land movement around the New Zealand coastline: implications for sea-level rise. Institute of Geological and Nuclear Sciences Limited, Lower Hutt

Then again, some researchers insist that sea level inundation is likely all around GodZone. Following government’s publication of their “New Zealand Coastal Policy Statement (NZCPS)”, all Territorial Authorities were required to carry out a coast hazard assessment out to 100 years.

This led to some Territorial Authorities including their expected inundation areas into District Plans. House prices in these areas were hit hard, with some unable to gain adequate insurance. Overnight hundreds of millions of dollars wiped off residents’ life savings. Applications to build in many of these areas was denied, and prime building land became worthless.

Locally in Wellington and surrounding suburbs, tsunami inundation marks have magically appeared on roads around the Region, It seems one side of the new lines represents danger, but one metre away safety! This is Island Bay on Wellington’s South Coast – flat as a pancake!!!

Moving on from GodZone, I see frequent posts from that eminent contributor Willis Eschenbach regarding many of the Pacific Island groups such as Tuvalu, Kiribati, The Solomon’s, Vanuatu etc. and how these coral islands actually resist sea-level rise and incredibly seem to be increasing in size.

So ardent were the claims being made that then President of the Maldives staged the now infamous underwater cabinet meeting back in 2009:

So are coral atolls to disappear? Well an article in National Geographic here suggests not:

….a growing body of evidence amassed by New Zealand coastal geomorphologist Paul Kench, of the University of Auckland’s School of Environment, and colleagues in Australia and Fiji, who have been studying how reef islands in the Pacific and Indian Oceans respond to rising sea levels.

They found that reef islands change shape and move around in response to shifting sediments, and that many of them are growing in size, not shrinking, as sea level inches upward. The implication is that many islands—especially less developed ones with few permanent structures—may cope with rising seas well into the next century.

But for the areas that have been transformed by human development, such as the capitals of Kiribati, Tuvalu, and Maldives, the future is considerably gloomier. That’s largely because their many structures—seawalls, roads, and water and electricity systems—are locked in place.

Their analysis, which now extends to more than 600 coral reef islands in the Pacific and Indian Oceans, indicates that about 80 percent of the islands have remained stable or increased in size (roughly 40 percent in each category). Only 20 percent have shown the net reduction that’s widely assumed to be a typical island’s fate when sea level rises.

Ironically now, the Maldives’ Velana International Airport is undergoing a massive US$400 million extension programme, yet is a mere 2 metres above mean sea level. Seems as though investors don’t believe in sea-level rise!

Speaking of airports, I was quite enthralled at my first ever trip to Holland (yes I know it’s now the Netherlands) in the mid 70’s landing at Schiphol Airport. Number one surprise was seeing police throughout the airport armed with fully automatic weapons – this was at a time of hijacking after all. But secondly, there was a plaque there commemorating the final naval battle with the Spanish that ended their 80-year war. So Schiphol Airport used to be under more than 4 metres of water.

Hendrick Vroom (ca. 1566-1640), Battle of the Haarlemmermeer

But all that changed when King William I decided in 1837 to reclaim the land. In 1839 the Dutch Parliament agreed. Consequently, a big drainage canal was dug and the excavated material used to build a large dyke. By now, the romantic windmills had given way to steam and three large beam engines were used to empty about 800,000,000 tonnes of water. The new Haarlemmermeer was created.

It seems then that The Netherlands found ways to adapt and even steal land from the sea. London likewise found ways to keep the tides at bay. King Canute would have been proud of both.

Given that the doomsayers are predicting Armageddon in 300 years’ time, just how many of our big city buildings will still be around anyhow?

300 years ago, people generally lived on the land. The Industrial Revolution had not yet begun, although the very earliest steam engines began to make a limited appearance – the Revolution would be decades away though. Newton’s Principia had only recently been published and his Opticks was not to appear till 1703.

The Treaty of Union was enacted to form Great Britain in 1707, and wars still raged across Europe. By now the Dutch were allies of Great Britain and fought together against French and Spanish forces.

The Colonies, most especially the Americas were still to engage in the Revolutionary War when the United States of America would be born. It was to be another 100 years for Canada to become a Dominion and did not gain full independence till 1937.

The Napoleonic Wars and the American Civil War were hundreds of years in the future. It was to be 50 years before Benjamin Franklyn carried out his first tentative research into Electricity and over 100 years for Morse to add to the invention of the Telegraph. Automobiles hadn’t even been thought of and flight was definitely for the birds.

Even the bicycle was over a century later with the Laufmaschine (or Velocipede) and the safety bicycle not until the late 19^th Century. Ironically the Wright Brothers ran an early bicycle repair shop!

If you brought a Queen Anne subject into today’s electronic society with airplanes, cars, TV, Radio, Cellphones, GPS and Computers – it would all appear as witchcraft. So what awaits us in 300 years – we cannot even imagine. But unless some other catastrophe overtakes mankind such as Nuclear War or Disease then it seems safe to assume our descendants – if they exist at all – will be well able to cope with a metre or so of water.

So I continue to say – even if the doomsayers are correct – SO WHAT!

Comments please by all means.