The curve has been corrected for the GIA effect.
Sea level | Environment | The Guardian
ESA cci aerosol cloud cmug fire ghg glaciers ice sheets greenland ice sheets antarctica land cover ocean colour ozone sea ice sea level sst soil moisture. The extension of the sea level CCI activities has started! Submitted by jlegeais on Tue, New paper from M. Passaro et al. Submitted by mablain on Thu, Start: End: Legeais et al. Submitted by jlegeais on Mon, New Arctic and Antarctic weekly gridded sea level product is now available. In this article, we will hear from various Dutch sea level specialists, whose concerns have thus far largely been confined to discussions in their own circles.
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Climate researchers and glaciologists have increasing doubts about the stability of the Antarctic ice cap. Instability here may cause a rapid acceleration in sea level rise, which will have major repercussions for the Netherlands, according to experts studying rising sea levels. In order to keep the seawater at bay, the dikes will need to be raised. As a result, the polders behind them will become relatively deeper, making them more vulnerable and more expensive to maintain. These higher dikes are also a problem in themselves: they prevent natural silting, which means our delta is unable to grow along with the advancing sea.
The experts share one concern: the Netherlands has no Plan B for a scenario in which sea levels rise faster than we accounted for in the Delta Programme. At the same time, there is no proper public debate about this issue, despite the urgent need for one. Not sometime in the future, but right now — because we need to make some important choices today. Especially if you consider how long it takes to develop and implement plans.
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Reducing CO 2 emissions and reinforcing dikes is only half the story. The other stark reality is that even these measures combined may prove insufficient in the long term to preserve the low-lying parts of our country. The other stark reality is that even these measures combined may prove insufficient in the long term to preserve the lower-lying parts of our country. The polder model — in its literal rather than political sense — has its limits, some physical and some more subjective. The physical limits are based on hard science: how quickly will sea levels rise — and how much can we actually handle?
The subjective limits are a question of taste: what kind of country do we want to live in while we still have time to decide? But before discussing projections for the future, we first need to look at the underlying story. Anyone who has been following sea level research recently will have noticed an increase in ice loss on both Greenland and Antarctica. Satellite observations also show that sea level rise is accelerating globally: in the twentieth century, the average speed worldwide was less than 2 millimetres per year; after the turn of the century it had already reached around 3 millimetres and, in the last decade, it has increased to 4.
This acceleration will continue, but it is of course uncertain at what rate. The prospects for the rest of this century appear increasingly sombre. Where the last IPCC report was still calculated using decimetres, more and more studies — including from the Royal Netherlands Meteorological Institute KNMI — are talking in terms of metres, as a worst-case scenario.
This assumes that CO 2 emissions and possible processes that accelerate the melting and calving of ice from the edges of the major ice caps will continue unabated. And when you add a statistical margin for bad luck, you reach the absolute worst-case scenario: a rise in sea levels of centimetres by This upper limit is almost three times what scientists thought possible just a decade ago. Of course, the most unfavourable scenario is certainly not the most likely.
But even one additional metre is a lot of water to deal with. And much more importantly: it will not stop after On the contrary: man is setting a sea level rise in motion that will influence the surface of our planet for millennia to come. It is already fairly certain that the ice caps in Greenland and West Antarctica cannot be preserved over the long term, nor can almost all of the mountain glaciers. If we continue to use fossil fuels at the current rate, global warming could even exceed 4 or 5 degrees. In that case, we will be talking about a sea level rise of about 55 metres. We are clearly failing to achieve that, as confirmed by the latest UNEP Emissions Gap Report which shows a wide gap between promises and actual policy.
Globally we are still very close to business-as-usual emissions — meaning the risks are high that we will exceed various tipping points. What does that mean? In that case, we will be talking about a sea level rise of some 55 metres. The full increase will take a few thousand years, but in this scenario we will start to feel the squeeze much sooner: 2 metres in this century, a further 5 metres in the century after that — to give just a couple of illustrative figures.
One thing is certain: in the Netherlands we no longer hold our future in our own hands.
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We are directly dependent on the success or failure of current international climate policy for our continued existence. And because it is very uncertain whether that policy will really achieve results, experts warn that we as a country must have a fully-fledged plan that also considers the possibility that the Netherlands may not make it and that identifies our alternative options.
He emphasises that there are major uncertainties regarding such issues as the ice loss in Antarctica, for example. Although still less than on Greenland, ice loss there has tripled during the last decade. Is that acceleration set to continue?
In the Netherlands, we seem to have the attitude that we will solve the problems by means of adaptation. In the long run, we may not be able to save the west of the Netherlands. Do policymakers and politicians really have enough interest in and knowledge of the long-term consequences of sea level rise? Katsman previously specialised in sea level research at the Royal Netherlands Meteorological Institute KNMI , and she is an authority in the Netherlands in the research on the underlying science — in other words, the connected chain of processes that result from a warming climate.
Melting ice caps, thermal expansion of ocean water, possible changes in ocean currents and wind patterns: all of these have an influence on sea level development — and all require specialist research.
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That also applies to the specific consequences of rising sea levels for the Dutch delta. How will rivers and soft-sediment coasts react? And for how long will we be able to control the situation? It is time to hear from Marjolijn Haasnoot. She is a senior researcher on climate and water at the Deltares knowledge institute and an expert in sea level adaptation. She is also the main author of Appendix B of the Delta Programme report that was published in September.
This report includes the first-ever look at the impact of new, global sea level scenarios as applied to the Dutch coast by the KNMI.
These new projections suggest that sea levels could rise much faster than was previously thought. How much faster remains uncertain, partly because we do not know how the complex melting processes along the edges of large ice caps will work out. What is certain, says Haasnoot, is that a wait-and-see approach will not be the best strategy. And now is the time to think about it and come up with a good plan — so that we can also implement it in time.
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When it comes to sea level policy, you need to be able to deal with uncertainties. The challenge presented by Deltares was serious: three metres in this century and a further five metres in the next. The creative brainstorming produced four main scenarios: two in which we remain where we are, one in which we move in the direction of the North Sea! As supervisor of the hackathon, Marjolijn Haasnoot cannot of course express a personal preference.
But she does say that the current plan is designed based on an increase in sea level of just one metre, and that she expects there to be a tipping point for our current strategy between one and two metres. After that, major transformative interventions will be required, for which they will be developing alternatives. She also makes a very important point: we need to make a decision.
If we turn the Netherlands into a fort, we will need to build gigantic dikes, but also, and perhaps more importantly, gigantic pumping stations. This is essential, because at some point we will need to pump all of the water from the Rhine, Meuse, Scheldt and Ems — which by that time will be lower than sea level — over those enormous dikes.
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