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Comment by Animats | Hacker News Reader

For the Western US, the problems aren't so bad. There's a coastal mountain range along most of the California coast. In LA, a few places such as Venice/Marina Del Ray may need seawalls, but except for a few areas areas, three blocks inland is at least 100 feet above sea level. LAX is 121 feet above sea level.

The SF bay has more problems than the coast. Parts of San Francisco may need seawalls, and bayfront development such as Redwood Shores needs to be stopped. Google HQ is in trouble; they're on fill and only 10' above sea level. But once you're south of US101/CA237, you're OK in most of Silicon Valley.

In the southeastern US, things are potentially much worse. There's no coastal mountain range. Florida is barely above sea level now. Miami floods regularly. New Orleans is partly below sea level already.

A big question is what this does to Mississippi River flooding. A higher sea level means less river flow and more upstream flooding.

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I'm really not convinced Miami will be around in 20 years. The floods are worse every year. Miami Beach doesn't just flood, it shuts down. There will come a time when sea level rise and hurricane season will collide in such a way that it won't be practical to rebuild.

Miami Beach is 4' above sea level on limestone. The slightest acceleration in seal level rise will doom the city. Maybe when the mega mansions on Palm Island become unserviceable people will take things seriously.

People say it could take another 100 years for the sea level to actually consume the land, but that's really not necessary. Just look at New York post Hurricane Sandy. Crippled parts of the city for months. When you get a storm like that, combined with higher tides and more regular flooding it seems like game over because they're just won't be enough time to rebuild before the next flood.

As someone who lives in Miami your comments come across as hilariously exaggerated

recent Elizabeth Kolbert new yorker piece on miami and flooding http://www.newyorker.com/magazine/2015/12/21/the-siege-of-mi...

The basic problem is the limestone. Because of the limestone, seawalls are essentially useless as the water goes underneath through the porous ground. I think very likely the comments only seem exaggerated to you because it's difficult to imagine with all the people around you driving fancy cars and buying expensive condos, like pre-cupernican difficult.

No one knows how long miami has, but I would bet it's closer to 20 years than 100 years. To be quite honest, I hope it happens sooner rather than later as maybe something like that will start to wake people the fuck up. Doubtful though. There's always another rationalization.

You're second paragraph is a cruel wish on the lives of millions. You wish this cruelty for the petty purpose of being on the right side of an argument

He's not wrong though.

There is this strange idea, particularly in the US, that we can buy our way out of the problems caused by sea level rise. That's (somewhat) true in some cases, but Miami is not one of them. The ground is simply too porous. You'd have to pull some Dubai-level shit and build a second Miami Beach next to the original and move everyone over.

South Florida will almost undoubtably be the first area in the United States where wealthy people are materially impacted by sea level rise. And because the foundation is so porous it won't take 100 years before areas become untenable. Flooding that last a few days starts to last weeks.

It really doesn't take much.

> He's not wrong though

I have yet to a shred of evidence for this 20 year theory

Why would the place you live in have any baring on your knowledge of the effects of sea levels rising? You aren't handed a geotechtonics degree when you move there.

The idea that Miami will be gone in 20 years and not 200 is a ridiculous one. I live here on an island by the sea, I guess that doesn't make me a geotechtonista but it gives me some perspective other people in their basements in middle America might not have.

That's a good point. What high sea levels look like in practice is more frequent flooding. This happens long before total immersion.

For Hurricane Sandy, if the 14th St power substation had been protected, and subway and train tunnels equipped with flood gates (that was supposed to happen after 9/11 as an anti-terrorism measure) the damage would have been much more localized. The appropriate role for government here is to toughen up the infrastructure. New York has a plan.[1]

We just have to write off Miami Beach and parts of New Orleans. New Orleans has higher ground nearby, but Miami doesn't.

There are some tricks used in urban areas subject to river floods. Here's the Tamshui River as it flows through Tapei.[2] The river is bordered by broad parks, and the park is bordered by a freeway raised on a berm. That's all for flood control. During floods, the parks are underwater. Massive floodgates block roads under the freeway. (There are emergency stairs for people caught on the wrong side.) The river bridges are all high enough to bridge any flood. After each flood, the parks need some maintenance, but they have few structures and the ones they have are very solid. San Jose has a similar, but smaller, arrangement for the Guadalupe River. (Yes, that's why there are such nice trails and bike paths in downtown San Jose.)

[1] http://www.nyc.gov/html/sirr/downloads/pdf/final_report/Ch3_... [2] https://en.wikipedia.org/wiki/Tamsui_River#/media/File:Dansh...

I wouldn't even give NYC 20 years. A direct hit from a category-3 hurricane would decimate that city. The building codes were only updated in 2008 to withstand hurricane winds. It's really only a matter of time

ACK. If we are good at anything, then of the optimism bias.

We constantly overestimate our abilities while we underestimate the problems that can emerge.

Combined with our rather low ability to think in systems theory enough, to actually understand the system we are living in...

Bad combo...

I think the idea is to look at the actual problem causing climate change.

Unless your post was satire. Putting seawalls up everywhere that might be affected seems like the wrong message to take away from the article.

No, I'm serious. I assume the problem won't be fixed globally, so we have to look at it locally. For the Western US, it's not that bad. Southeastern US, not so much. The northeastern US has populated low-lying areas; the low-value ones need to be evacuated and the high-value ones, like Manhattan, protected. Even Manhattan isn't very flat; seawalls only need to go up to 30th St or so.

The US as a whole is in good shape; much of the US is way above sea level. Russia, which has almost no useful coastline, will be fine.

I appreciate your observations. I may be defeatist it seems too late to stop climate change. The last time political gridlock at the federal level was this bad, the U.S. had a Civil War, so I find it hard to envision a federal solution that happens soon enough. So instead, I'd like to know, "What comes next?"

You can't fix it "locally". Without global solution the sea level will just go higher and higher, and you will have to relocate all major coastal cities in a matter of centuries. Seawalls by themselves can only delay the inevitable.

NYC alone has real estate price of ~$1 trillion.

In light of how hard of a problem the global solution is (stopping greenhouse gas emissions), which one do you think is cheaper and easier? The global solution costs trillions of dollars as well, and has much more difficult coordination problems.

The local solution in this context at least has the benefit of having well defined goals where individual agents act out of there own easy to understand best interest. i.e: My house in Florida is flooding- I'm going to move to a different state. i.e: New York City is flooding and I'm a property developer- I'm going to build high rises somewhere close to NYC but at +30 m elevation.

Well, as they say, when you find yourself in a hole, the first thing to do is stop digging. That is, the "local solutions" are at best interim measures to give us more time (while we hopefully tackle the root cause). They don't "solve" anything.

If your house in Florida is flooded and you move to Montana, you merely avoided the problem. I'm not saying it's wrong of you; it's the rational action for an individual. But it didn't solve anything any more than refugees fleeing Syria have solved the problem of war in Syria. And, just like Syria, some people will have to foot the bill this way or that.

I think this understates the magnitude of the problem. Humanity has had pretty constant coastlines for our entire history. If we get accelerating sea level rise we'll have to keep rebuilding our urban infrastructure every decade or three.

The cost of maintaining sea walls will affect the value of land protected by the walls, and if levels continue to rise it will make land elsewhere more competitive. So I think local solutions will have global effects - effects of moving people and stuff around. It's not like sea level rises are going to be sudden and unexpected; they will be priced in if and when they have economically measurable effects.

I don't think there are any real problems directly caused by global warming in rich countries. Price information, including insurance costs, will be enough.

Second order effects like changes in the viability of crops may affect food security (but I expect climate change to make crops more viable elsewhere, or a different production mix), and economic (but warming related) migration will be a continuing and increasing challenge. International migration of farmers is probably the biggest problem I see.

International coordination of action is not going to happen or make any real difference without threat of military force, and I don't buy the idea that the problems will be acute and obvious enough to justify that. You can't fight tragedy of the commons without an overarching authority which we don't have. Countries will cheat for local gain. Global climate change politics is mostly a waste of time unless people are willing to start wars over failures to curb emmissions, and I just don't see it. People are much more willing to start wars over migration pressures, so I think that's what we'll see.

You forget - the ones who get displaced, the poor, the third world - they are going to blame the west squarely.

That negative sentiment will take on a life of its own.

The poor and those in the third-world already blame the west for many of their problems. This changes nothing.

Yes you most definitely can fix it locally, at least for some locales. Point in case: Netherlands.

So, we finance seawalls with money no one has, but what happens when most of those buildings can withstand hurricane winds. What then? Rebuild all of them?

The assumption underlying a lot of the recommendations for actions in response to climate change is that the overwhelmingly dominant factor is CO2 emissions, and that reducing CO2 emissions is the only and/or best way to walk back from the consequences. Neither is true. For one, CO2 emissions reductions may not be realistically possible with our current technology and geopolitical situation. More importantly, there are other factors at play (such as soot changing the albedo on snow/ice covered arctic areas) and it's likely that there are dynamic effects at play which cannot simply be walked back by reducing CO2 atmospheric concentrations.

It's very likely that we're already locked into a certain level of sea level rise over the next few hundred years due to the breakup of antarctic ice sheets. This may not be something we can stop even if we could reduce atmospheric CO2 to whatever level we chose tomorrow. We need to look at ways of mitigating the impact of climate change and environmental change (whatever the cause) in the future even as we look at ways to try to reduce the negative impact of human activity on the climate and biosphere in general.

There are far too many people who look at pollution and climate change through an essentially religious lens. As though CO2 emissions are sin, and the only thing to do when caught sinning is to stop sinning, or at least sin less. This is an incredibly immature way to handle the complex relationship between mankind and Earth's environment.

Building sea walls is not a very good solution, we need to find a way to move melt water to the deserts instead. There is a very large amount of dry land that could consume a large portion of ice sheets as groundwater.

This assumes that climate change problems are local (in fairness, maybe the parent comment just happens to be focusing on those particular issues), but it may well create global economic and security crises, including wars.

Other than concern for the welfare of billions of people, who will buy your products? How will technology, education, and economic development spread in the developing world or even in the wealthy ones, when so many resources are spent on surviving climate change? Look what a blow the Great Recession and a couple of minor wars was to so many people; this would be much worse.

#bandaidfix

Seawalls are a bandaid fix, yes, but they're probably a reality we'll have to deal with at this point. We may have passed the point of inevitability for this rise in sea level -- barring, as the article suggests, any unforeseen stabilizing or countervailing forces to balance out the loss of the ice sheets.

Basically: seawalls aren't the solution, but they're probably part of how we cope with whatever degree of sea-level rise is already bound to happen at this point.

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