
Rising Seas Will Erase More Cities by 2050, New Research Shows - uptown
https://www.nytimes.com/interactive/2019/10/29/climate/coastal-cities-underwater.html
======
jefftk
Summary: elevation estimates using data from SRTM [1] are too high in built-up
areas, because unlike with LIDAR data it's not able to tell the difference
between "this is high ground" and "this is low ground with a building on it".
Which means many coastal urban areas are more vulnerable to sea level rise
than people had previously estimated.

They try to get a better estimate by building a more complex model, and
calibrate it using LIDAR where that's available. This lets them say not just
"things are worse than we thought" but "these specific parts of these
populated areas are at risk".

[1]
[https://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Missi...](https://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Mission)

~~~
GrumpyNl
Where does this fit in?
[https://news.ycombinator.com/item?id=21310972](https://news.ycombinator.com/item?id=21310972)

~~~
jefftk
If ice cliffs in the Antarctic won't collapse catastrophically that decreases
our estimate for how quickly the sea is likely to rise, which is certainly
good news!

But we're still going to get some rise, and accurate elevation modeling is
important for figuring out what effects that's likely to have.

Roughly, you can think of these as two disconnected efforts: get the best
estimate you can of the distribution of possible future sea levels, and get
the best estimate you can of the impact of different sea levels on humanity.
Your link is the former, this link is the latter.

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poutine
To put this in context we're talking about 4 to 5 mm per year of sea level
rise on average globally for the next several decades.

Some areas will be more and some less as sea level rise isn't uniform (for
instance isostatic rebound on the west coast of Canada will result in a net
sea level drop in some areas).

Mitigation will be key as even if we eliminated carbon emissions completely
today there's already committed warming in the system that will result in sea
level rise through the century. We're just talking about how many extra mm per
year on top of the 3-4mm or so that it is now.

~~~
peter303
The rise has been 3 mm a year (1/8 inch) since 1990 or about 4 inches.

[http://sealevel.colorado.edu/](http://sealevel.colorado.edu/)

This has been averaging millions of measurements of satellite altimeter over
oceans. That is considered more accurate than tidal gauges which are subject
to local changes such subsidence near river mouths.

The 3 mm is a combination of land glacier melt and water thermal expansions. I
have heard talks all over the map as to which factor is more dominant.

So 4-5 mm a year in the near future is not too off.

~~~
poutine
I liked table 1 as a nice summary from a referenced paper in the above paper,
found here:

[https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014...](https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014EF000239)

Their data suggests thermal expansion is the primary culprit.

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itcrowd
Here's a summary of the paper I gave before when a NYT piece covered it
yesterday.

For USA and Australia, high-resolution/precision lidar-based maps are
available of coastal areas. For other regions of the world it is not the case
(or severely limited). However, gaining an insight into the elevation of land
is crucial to determine a region's vulnerability to sea-level rise. NASA’s
SRTM has almost global coverage of elevation levels, but is known to be too
low resolution to be meaningful for this application (esp. in urban areas). A
neural network was trained on the USA lidar data to augment the SRTM data
(i.e. make the resolution higher). The network was verified on the Australian
lidar dataset (and they got a good match; the model was already published
elsewhere before [1]). The point of this paper was to then have the newly-
derived elevation maps be exposed to sea-level change. This is where the maps
with flooded cities come from [which were in the NYT article].

[1]
[https://www.sciencedirect.com/science/article/abs/pii/S00344...](https://www.sciencedirect.com/science/article/abs/pii/S0034425717306016)

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wsc981
Makes you wonder when coastal property prices start plummeting. And when banks
stop granting mortgages for buying coastal homes. I don’t believe this is
happening yet.

~~~
rectang
Is there a way to short these real estate investments and fleece climate-
change-denying ideologues who are keeping coastal property values high? Do
well by doing good! :D

~~~
badfrog
If there was, you'd probably be paying a lot to hold the position for 30
years.

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auto
Slightly unrelated, but first author on this paper is Scott Kulp, an
acquaintance and fellow ACM member from my undergrad days, and above and
beyond one of the smartest people I've ever met in my life. As in, double
majored in Math and Comp Sci in undergrad, completing it in three years while
looking dreadfully bored in every lecture we had together, smart.

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seveneightn9ne
Plug for thisplacewillbewater.com - they have a great map of what 4C warming
will look like and you can also buy biodegradable stickers to post around and
raise awareness if you live in an area that will be underwater.

~~~
adolph
Looks like SpaceX predicts <.5C rise given their Boca Chica launch site.

[https://seeing.climatecentral.org/#12/25.9917/-97.1329?show=...](https://seeing.climatecentral.org/#12/25.9917/-97.1329?show=lockinAnimated&level=1&unit=feet&pois=hide)

[https://en.wikipedia.org/wiki/SpaceX_South_Texas_Launch_Site](https://en.wikipedia.org/wiki/SpaceX_South_Texas_Launch_Site)

~~~
wolfram74
Or that they'll have more than one launch site in 20 years.

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leeoniya
weird how sea level rise is always used as the doomsday scenario rather than
the much more serious threat of delicate ecosystems collapsing and famine that
would affect everyone.

~~~
shawnb576
this!

i'm finding that people - educated, thoughtful, caring people - have real
trouble wrapping their heads around this threat, how serious it is, and how
fast its coming.

these same people are very concerned about plastic pollution. real issue, but
not civilization ending. and if we stopped the major sources tomorrow, we'd be
fine. CO2 does not work this way.

i think it's because people can see and feel plastic. but they look out their
window and things look...fine (apologies to california and other places where
things are not fine)

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pmiller2
> Over all, the research shows that countries should start preparing now for
> more citizens to relocate internally, according to Dina Ionesco of the
> International Organization for Migration, an intergovernmental group that
> coordinates action on migrants and development.

How the hell is Vietnam supposed to prepare for non-existence?

~~~
sithadmin
It doesn't have to? Look at a map of Vietnam, then look at the (relatively
small) portion of Vietnam presented in the article's graphics...

~~~
NeedMoreTea
A "relatively small" portion that's still a major territory loss that includes
everything south of Ho Chi Min, and much of the city - of 10m. I'd say they
have to. Perhaps quickly as these estimates appear to be based on RCP2.6 -
that's the most optimistic track assuming _everyone_ is meeting Paris goals.
Right now, no one is.

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yters
Since the threat is so imminent, are there specific climate change predictions
that have come true?

~~~
lurker458
One of the predictions was that we'd get stronger heat waves in West Europe.
We broke several old records this year. [https://www.bbc.com/news/world-
europe-49100271](https://www.bbc.com/news/world-europe-49100271)

~~~
romaaeterna
But you've been in a warming trend for millennia in Western Europe -- the
Danube and Rhine used to freeze over in the time of Tacitus.

~~~
Xylakant
The Danube and Rhine river froze over in times my parents can remember. A
strong contributing factor to why rivers today don’t freeze any more is that
we’re using them to cool power plants and similar.

~~~
romaaeterna
They froze frequently, and this was not something noted in the 18th century,
before power plants. You had reindeer in the Black Forest in Caesar's time.
Europe was quite a bit colder in historical times.

~~~
SamBam
The current temperature is clearly significantly hotter, and the rate of
change is greater,

There has not been a "warming trend for millennia." The temperature rose
steadily for about 1000 years since the Roman times, up through the Medieval
Warm Period, then cooled steadily until about 1800, and then have shot up
recently.

Take a look at the graph at
[https://en.wikipedia.org/wiki/Medieval_Warm_Period](https://en.wikipedia.org/wiki/Medieval_Warm_Period)

------
brohoolio
Did I just miss the link to the research material?

How much higher will it be? 6 inches? 2 feet?

~~~
luu
I believe the paper is
[https://www.nature.com/articles/s41467-019-12808-z](https://www.nature.com/articles/s41467-019-12808-z).

If I'm reading the paper correctly, the authors don't argue that sea levels
will rise more than previously predicted. Rather, they argue that the
classical technique for estimating impact by using elevation (SRTM) is
overestimating elevation and therefore underestimating the impact of rising
sea levels. The authors claim that their technique (CoastalDEM) also
underestimates the impact of rising sea levels, but reduces the systemic bias
present in previous estimates.

~~~
radford-neal
Thanks for the link. One statement from the paper: "this analysis assumes a
static coastal topography".

This seems like a significant limitation, especially when a lot of the
affected area consists of river deltas (eg, most of Bangladesh, the Mekong
delta in Vietnam). One would expect that a rise in sea level in a delta would
lead to increased silt deposition on the newly-submerged parts of the delta,
reducing the impact compared to a naive calculation, perhaps quite
significantly.

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steve19
At what point do we first see mass floodings from unusually high tides, such
as during proxigean spring tide? Surely it must be soon if Veitnam will be
underwater in just 30 years time?

~~~
catalogia
Apparently it's already happened.

> _The findings don’t have to spell the end of those areas. The new data shows
> that 110 million people already live in places that are below the high tide
> line, which Mr. Strauss attributes to protective measures like seawalls and
> other barriers._

~~~
ekianjo
So basically we have 110 millions of people living in "dangerous" areas so far
yet nobody was impacted?

~~~
big_chungus
Essentially, yes. The Dutch have been living with this for hundreds of years;
it will cost, but it is certainly possible to construct mitigatory measures.

~~~
code_duck
So the way it affects them is by requiring the expensive construction of
seawalls, drainage and other defensive mechanisms.

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keymone
is there any noticeable effect of earth’s rotation and uneven gravity field on
distribution of sea-level change?

~~~
chris_overseas
Yes gravity, and to a lesser extent rotation, have a (somewhat unintuitive)
impact on how the sea level will change across different parts of the globe.
There's a good overview of this topic here:
[https://www.theguardian.com/environment/ng-
interactive/2018/...](https://www.theguardian.com/environment/ng-
interactive/2018/sep/12/greenland-antarctic-ice-sheet-sea-level-rise-science-
climate)

Edit: video showing gravity changing over time due to melt:
[https://blogs.agu.org/wildwildscience/2016/07/21/gravity-
gre...](https://blogs.agu.org/wildwildscience/2016/07/21/gravity-greenland-
dropping-no-really/)

~~~
7952
The sea level as it stands today is already effected by gravity. And this is
in fact built into the wgs84 datum. So vertical elevation is measured relative
to that assumed sea level after the effects of gravity. And a rise in sea
level would presumably be measured relative to that existing datum.

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klyrs
[https://www.nature.com/articles/s41467-019-12808-z](https://www.nature.com/articles/s41467-019-12808-z)

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arkades
Does anyone have any sources for good projects for the USZ?

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IanDrake
More? I can't think of one that's been erased yet.

~~~
mikhailfranco
Indonesia is moving Jakarta's capital status and government functions to a new
city on Borneo. Of course, they cannot move Jakarta itself, which is also
sinking due to groundwater extraction, and will be flooded unless they build a
costly barrage system. They need to get the Dutch back to show them how (the
Dutch will need a place to move anyway :)

Thailand is also discussing a similar plan to move the capital from Bangkok to
Ayutthaya, the historical capital before the Burmese invasion of 1767.

New York is planning a sea wall system in southern Manhattan - _The Big U_ \-
but what they really need is a truly BIG barrage from Long Island to Staten
Island across the Narrows, and a smaller effort between the island and the New
Jersey mainland. Closing the East River will be more difficult, depending on
how much of the shoreline will be included. By coincidence, the Dutch also
used to control New York.

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tengbretson
Any chance this gets published if it somehow found the opposite to be true?

~~~
nabla9
To answer your conspiratory rhetorical question: Yes it would.

There are some good news from research reported, like "Slowdown in Antarctic
mass loss from solid Earth and sea-level"
feedbacks[https://science.sciencemag.org/content/364/6444/eaav7908](https://science.sciencemag.org/content/364/6444/eaav7908)

Just because there is less good news than bad news, does not make science
biased.

~~~
tengbretson
> To answer your conspiratory rhetorical question: Yes it would.

The accusatory tone of your response only reinforces my concern. It doesn't
even require a "conspiracy" as you gibingly added. If a scientist considering
publishing findings counter to consensus expects to be met with this kind of
reaction from their peers, and shouts of "denier" at large, that's all it
takes to put a finger on the scale to bias what gets published.

~~~
SamBam
You protest too much and show your clear intent.

First, your "Any chance" question was clearly begging the question. The
framing was that you believed the article _wouldn 't_ get published if it went
the other way.

Then, when shown evidence that such articles do, in fact, get published, and
that there is _no_ conspiracy against them, you somehow suggest that... _that_
response will keep scientists from publishing their work?

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ycombonator
They had predicted almost a foot rise in sea level for 2020-25 in 1984. So we
will see what happens. Source:
[https://books.google.com/books/about/Projecting_Future_Sea_L...](https://books.google.com/books/about/Projecting_Future_Sea_Level_Rise.html?id=c1Hls8bvKT8C)

