Projecting sea level 300, nah, 1000 years in the future

On the same day that I published the post on the IPCC, the political organization that is mistaken for a scientific organization, an article was published in a Belgian newspaper, titled Belgian expert: “It’s inevitable: large parts of Flanders are going to be under water”, in which exactly the same error was stated (translated from Dutch, my emphasis):

The highborn professor Jean-Pascal van Ypersele is a regular at the United Nations as a climate expert, advises Presidents on the rising sea level and was for many years Vice-President of the IPCC, the Intergovernmental Panel on Climate Change. This is the most important scientific climate panel in the world, that was awarded with the Nobel Prize.

It is an interview with van Ypersele about sea level rise and its influence on the Belgian coastal region. Some excerpts (translated from Dutch):

And those negative effects will also be felt in Flanders. “We can’t prevent large parts of the region will be under water. Within three hundred years, maybe earlier: it will happen. Much of the region doesn’t lie much above sea level.”

Did he really say 300 years?

Luckily, there is some hope … (translated from Dutch):

According to van Ypersele, we can no longer turn back climate change. But trying to halt it is possible: “We can make sure that it is as little as possible. And that the sea level doesn’t rise 5, but only 3 meters.”

How reassuring. When we invest huge sums of money during the next decades, then the people of 10 generations from now will only have to deal with a sea level rise of 3 meters.

But then …

5 meters when we do nothing?!?!

Where did he get this number from? That got me curious. What is the IPCC projection on sea level rise 300 years from now? I couldn’t believe it myself, but there actually is such a projection in chapter 13 of the last IPCC report. This is figure 13 on page 1188:

IPCC AR5 chapter 13 fig. 13

The projections are roughly from 0.4 m to 0.9 m for the low scenarios (< 500 ppm in 2100) and from 1 m to 3 m for the high scenarios (> 700 ppm in 2100). 5 meters, that is almost 2 meters above the range of the most apocalyptic projections from the IPCC report.

Then what to do to avert this catastrophe? (translated from Dutch):

But how to do this? How do we let sea level rise and global warming slow down when we take the car as many times as possible, usually alone, when we burn wood in the fire place and when we travel more and more by plane? When everyone knows that the situation is serious and we are confronted with it more often.

No more driving car or travel by plane, I could somehow get that, but the fireplace statement is a bit curious. Isn’t biomass considered to be, ahem, “climate neutral”? If not, then there will be a bit more to do: most of what we now call “renewable energy” is produced by … burning biomass. Later in the interview also building energy efficient houses and alternative energy are mentioned.

That we are confronted with “it” more often is a puzzling statement, considering that we are talking about a process that, as he acknowledged himself, is taking several centuries to have serious impact. So what are we currently confronted with more often? This was fun to read (translated from Dutch):

Just think of a walk in nature where plants are in bloom which under normal conditions would not be in bloom yet or animals that appear in places where they never were before.

Which is some light-years away from the doomsday scenario of a 5 meters sea level rise and the resulting flooding of the coastal area. Flowers blooming earlier in the year. Hey, we can’t have a clearer sign than that. 😉

I am not really sure what to think of the interview. Those scary projections 300 years in the future are rather unreal.

Firstly, there is the hidden assumption that we would keep emitting at the same rate for the next couple hundred years. Which I find highly unlikely, even if we would fail to implement wind and solar as primary energy sources.

Secondly, our society will undoubtedly be VASTLY different 300 years from now. Imagine what people from the 1700s might think if they would be catapulted in the current time… I can’t imagine that there wouldn’t be any technological progress in the next 300 years in order to adapt to climate change or to prevent the flooding of our coastal region.

Thirdly, without being denigrating to the models, the climate system is a vast, complex, coupled, chaotic system from which we only recently started collecting reliable data. I have no doubt that this system can be modeled with CO2 concentration as its primary control knob, but then I will have my doubts how good it resembles that complex, coupled and chaotic reality. The outcome of the model for temperature will depend on a number of assumptions. On its turn, a modeled sea level rise will depend on a series on assumptions of how for example the Arctic/Greenland/Antarctica/glaciers/thermal expansion will react on this modeled temperature increase. The model outcome of sea level rise therefor will be even less certain and uncertainty will increase with its length. So, just based on these principles, I have my doubts on how reliable these projections of 300 years in the future are.

Looking further for information on sea level rise along European coasts, I found a presentation by van Ypersele himself on the latest developments on Climate Change (from December 2017). In it this gem:

Sea level rise Belgium – presentation van Ypersele december 2017


An 8 meters sea level rise …





Can this possibly be taken seriously? It is highly unlikely that we will sustain emitting at the current rate for the next say 800 – 900 years and future societies will be completely unrecognizable for us. For goodness sake, we are talking about a time frame from the Middle ages until now!

The names of the investigators (Dendoncker, van Ypersele and Marbaix) seemed familiar. When I followed the link, I recognized the Greenpeace report from 2004. Did that number really come from this report?

Well, yes. This is the accompanying image on page 34:

8 meters sea level rise: Greenpeace report 2004

It starts with the current situation (top image) in which Amsterdam and Rotterdam (in the Netherlands) already seem to be under water…

Hey, that is an interesting starting point! The images depict the area that is below water level, regardless of the flood barriers put in place by the Dutch. While this may say something about the risk of flooding of that land, it says nothing about whether it will be flooded when sea level rises x meters. It indicates the land that will be under water when sea level rises IN CASE there would be no flood barriers (but there are).

In the Greenpeace report, the authors referred to an “average scenario” of the “latest IPCC report” for this 8 meters figure. The latest IPCC report in 2004 was the Third Assessment Report of 2001. Apparently, the authors took the 8 meters value from the SAR IPCC report and van Ypersele took the 8 meters value in the 2017 presentation from the 2004 Greenpeace report. Do I understand it correctly that this value didn’t change since 2001?

Then I found the pièce de résistance at the end of the presentation in the list of useful links:

Presentation van Ypersele December 2017: useful links

A former vice-president of the IPCC who refers to skepticalscience for “excellent responses to contrarian arguments”.

I am not sure what to think about that.


6 thoughts on “Projecting sea level 300, nah, 1000 years in the future

  1. manicbeancounter

    If you look at Figure 13 again there is another issue.
    The High Scenarios shows sea level rise of 1.5 to 6.5m in 2500 for >700ppm CO2.
    Medium scenarios show sea level rise of 0.2 to 2.3m in 2500 for 500-700ppm CO2.
    Low scenarios show sea level rise of 0.5 to 1.0m in 2500 for <500ppm CO2.

    The explanation is the uncertainty range. The greater from the current state of affairs, the greater the uncertainty range. That is the greater tails on the bell-shaped curves, hence the reason for the 500-700ppm have a lower bottom end than for <500 ppm.
    Note the High scenarios lower range is only 30cm a century, and the top end is 1.3m a century.

    What I also find interesting is that under the medium scenarios, Antarctica is gaining ice, hence reducing sea levels, but under the low scenarios has no impact whatsoever.
    A reason the leaking reports is for sceptics to pick up on the obvious errors that the consensus of the world's leading climate scientists is unable to find.


  2. chrism56

    It would be worth checking if Jean-Pascal van Ypersele actually doesn’t travel by air or drive a car, or is he another of the hypocrites who believe it should be other people who have to suffer. I would give strong odds that he is the latter


    1. trustyetverify Post author

      I have absolutely no doubt that he travels a lot. He was the vice-president of the IPCC and, in that function, present at different conferences around the world. I am pretty sure that he didn’t swim to for example Durban or Lima.


  3. Pingback: Sea Level Rise Projections and Policy | ManicBeancounter

  4. poitsplace

    The estimates used by the IPCC assume that CO2 uptake rates will be identical to those seen in the proxies. But in the proxies, atmospheric CO2 levels are caused mostly by equilibrium shifts based on ocean temperature. 95% of the CO2 in the biosphere is dissolved in the oceans and as the ocean warms slightly, the solubility of CO2 in the oceans goes down, releasing CO2. As the oceans cool, the solubility increases and additional CO2 is removed from the air. It’s a bit more complex than that but basically that’s the relationship.

    Using the IPCC’s logic, soft drinks are impossible to make because CO2 would take thousands or perhaps millions of years to dissolve sufficiently. But since such equilibrium shifts are not temperature driven. They’re driven by changes in available CO2. And it only takes a fraction of a second to dissolve the CO2 in your drink. And the absorption rates are so high that 50% of our emissions are being absorbed every year. If we didn’t emit anything, levels of CO2 in the atmosphere would fall rapidly as it was absorbed by the oceans (and new plant growth)



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