Sea level rise is going to be one aspect of climate change that will be with us for a loooong time.
The rate and amount of sea level rise will be dependent on the rate and amount of continued global greenhouse gas emissions, and this is critical, because the slower sea level rises, the more chance we have to adapt to it. (See the IPCC’s Special Report on Oceans and the Cryosphere for more details if you’re interested).
But even if we aggressively reduce emissions and can limit the global rise of temperature in accordance with the goals of the Paris Agreement, the oceans have already absorbed significant heat, including in the deep ocean (a warmer ocean expands), and ice caps will continue to melt for a while….and by ‘a while’….I mean, very probably centuries.
This is sobering. During the last ‘interglacial’ (the period between ice ages), the temperature was likely 0.5C to 1.0C warmer, and sea level was likely around 6-9 meters higher. And remember, we’re trying to limit this century’s warming to less than 1.5C. If we can’t reduce emissions more than we have pledged to already in the Paris Agreement, we are on track for almost 3C. That implies a lot of potential sea level rise.
Rising oceans will be our reality for many, many generations.
I’m not saying this to ruin your week. Humans have been dealing with changing sea levels since humans have been around.
After the last ice age, when there was a mile of ice on top of Canada (surely even the Canadians were a bit miffed about that), the relatively sudden removal of that ice about 12,000 years ago, started a process called ‘isostatic rebound’. The land that was compressed under the weight of all that ice, started to ‘spring back’, and in fact, is still doing so. Land is actually rising, relative to the ocean, on some of our northern coasts. Sea level rise from human causes is now overtaking that process in many places, but it means that formerly glaciated places will see less relative sea level rise than our more southerly coasts in the Northern Hemisphere.
And, as you might imagine, melting all the ice-age ice that was previously covering North America and northern Asia led to massive sea level rise as the ice age retreated.
The graphic below is from a paper by Fleming et al. (1998) and is a collection of data that reconstructs sea level over the last 20,000 years or so.
A ‘pulse’ of meltwater added almost 30 meters of sea level from about 15,000 years ago to about 14,000. And since then, sea level has risen another 80 meters!
As you can see though, sea level (and also temperature by the way) has been pretty stable for about the last 6-7,000 years. Coincidentally (or probably not), the same period of time when humans have done most of our population growth.
Facing sea level rise then, is both an old and a new problem. Humans have witnessed massive sea level rise, but not much in the modern era when humans began to design civilizations and cities. So what’s particularly new about it is how many people live at the coast and how much fixed infrastructure we have in our coastal cities.
Conservative estimates put around 40% of the global population (almost 3 billion people) living within 60 miles of the coast. Some of our most expensive real estate and most active centers of commerce are also at the coast (e.g. Manhattan, Shanghai, Mumbai, London).
Sea walls and ‘hard armoring’ are possible for a while in some places (see the 16.5 ft wall New York is building), but in other places, it’s too expensive, or the bedrock is porous (e.g. limestone in Miami) which means water will just seep underneath.
But for some nations, it’s not even ‘just’ the major matter of protecting their low-lying cities, it’s their whole survival.
In the Maldives - a nation of over 1,000 small islands in the Indian Ocean - 80% of its land is below 1m (3 ft) above sea level. That’s the kind of sea level rise we could see by the end of this century, let alone beyond. For the Maldives, and some Pacific Island nations, dealing with sea level rise is an existential imperative.
So, while the cost of adapting to sea level rise is aaaaalmost prohibitive. The cost of not doing so would be catastrophic.
A solution: floating cities.
It’s sounds like modern science fiction, but the Maldives are already part-way through constructing a city for 20,000 people that will be entirely afloat. The first residents will move in in 2024.
The design of the city mimics ‘brain coral’, which surrounds and protects the floating city. The Dutch company who is partnering with the Maldives Government has a relatively long history of constructing floating buildings, but this scale and timeline (5 years) is unprecedented.
Power will mostly be solar, air conditioning will be provided by pumping cool sea water up from below, and sewage treatment will provide fertilizer for plants in the floating streets.
No doubt much will be learned from this project and from others currently in the planning stage, and much kudos to this small nation for taking on the task and the expense of getting busy and trying it out.
I really hope this works and can be replicated and improved over time - both for the residents of the Maldives and for all nations who have a coast, but especially those whose entire landmass will disappear.
But I also have a strong suspicion will all be using this technology at some point in the not-terribly-distant future.
Wow.... The whole concept of the floating city is pretty fascinating....!