No large coastal city will become flooded on a permanent basis. Building levees is just too easy and cheap relative to cost of giving up on a city, just ask medieval Dutchmen. By the way, the scientific consensus for predicted sea level rise in the worst temperature growth scenario is still less than 1 meter by 2100. That’s less than the difference between low and high tide. Some areas will get flooded (eg large parts of Florida Everglades), but 1 meter is really not a big deal.
Similarly, there is no reason to be very concerned about crops: we already are able to grow crops in a very wide variety of climates, and we have cultivars specially selected for local climate conditions. While climate change is very fast on geological scale, it’s rather slow on human scale, which gives us plenty of time to adjust our crops and farming patterns.
This is the biggest reason why climate change is not an existential threat: we are not going to sit on our thumbs, and watch the steamroller slowly ride over us, at speed of 1 cm per day. That’s not going to happen: mitigating the problems associated with climate change is rather simple, relative to other problems our societies solve on a regular basis, and we have a lot of time for it.
> No large coastal city will become flooded on a permanent basis. Building levees is just too easy and cheap relative to cost of giving up on a city, just ask medieval Dutchmen.
Levees don't work in south Florida. Well, they work to stop water that comes in horizontally above ground level, but in south Florida floods usually come in by bubbling up through the porous ground.
Yes. Miami needs to move a few meters straight up. This is quite possible. Galveston, TX [1] and Chicago [2] did that a century ago. Miami Beach is raising some main roads, finally. Here's Miami's flood zone map.[3]
Worldwide, cities on river deltas face problems. Mostly in Asia. New Orleans is the only US city built on sand flatland at the mouth of a huge river. Asia has several of those.
New York is building a seawall around lower Manhattan. The West Coast isn't that vulnerable because the coast is mountainous. Even in areas of LA that look flat, go a few blocks inland and you're up 10m or so above sea level. The parts of SF built on fill may have problems.
This isn't the end of the world. But some cities will need rebuilding.
It appears that in the case of Galveston and Chicago, the government paid to raise the streets and sidewalks, and it was up to private property owners to deal with it themselves.
In the USA, is that even possible anymore? I've been to both Galveston and Chicago, and you can see oddities here and there in some neighborhoods. In many cases, homes were not actually raised - the main floor became a basement and above it new doors were made into the existing walls!
In a lot of locations, you cannot have a basement and get flood insurance. So what poorer people did in Galveston and Chicago is no longer an option.
A few meters? That's the scenario where there's some runaway global warming and all the poles melt, right? Actual observed sea level rises are measured in millimeters per year. Historical trends can't lead to Miami needing to move several meters up unless you're talking about, like, 1000 years from now.
There are some problems with the assumption of a flooding crisis. The historical record from tide gauges have been retroactively altered over time, to make apparent level rises in modern times worse and level rises in older times less so (this seems to be a common theme with data from climatologists - they rewrite historical datasets to make the magnitude of changes seem larger).
Additionally at some point they switched to satellites and stopped using tide gauges but it's not clear that's more accurate and may actually be less accurate (but it did make the rises seem larger, so there's a conflict of interest there). In particular, NOAA and NASA disagree by a large amount on what the actual level of rise is. NOAA say it's about half what NASA say it is.
You can't look at historical trends because it's not rising linearly. Most of the warming and melting will happen in the last decades of this century. That's part of what makes it easy to underestimate.
But you are right that it will keep rising for a thousand years or more. But now at that timeframe we're talking 6-12 meters or more.
This is all in the fairly conservative public estimates that so far have underrepresented the pace and scale of change.
Will happen, according to academic models that have been frequently wrong in the past. Projecting prior trends forwards doesn't get you anywhere near meters of rise, that's my point. And no they have not so far under-represented the pace and scale of change, far from it. That's the kind of revisionist history that makes arguments about climatology fruitless. How can we even debate the accuracy of such forecasts when the past is inverted like that? Here's the sort of thing that was actually predicted, from an AP news report in 1989:
UNITED NATIONS (AP) _ A senior U.N. environmental official says entire nations could be wiped off the face of the Earth by rising sea levels if the global warming trend is not reversed by the year 2000.
Coastal flooding and crop failures would create an exodus of ″eco- refugees,′ ′ threatening political chaos, said Noel Brown, director of the New York office of the U.N. Environment Program, or UNEP.
He said governments have a 10-year window of opportunity to solve the greenhouse effect before it goes beyond human control.
As the warming melts polar icecaps, ocean levels will rise by up to three feet, enough to cover the Maldives and other flat island nations, Brown told The Associated Press in an interview on Wednesday.
The most conservative scientific estimate that the Earth’s temperature will rise 1 to 7 degrees in the next 30 years, said Brown.
It's thirty years later now and the temperature rise since then has been at the very lowest end of the most conservative estimate (which was itself so wide that it was basically useless and hardly an estimate at all).
We're going to have sea level rise in the region of 1-2 metres by end of the century, and 5-10 longer term.
Levees are expensive, and not always viable. It depends on the geography, the wealth of the city / county, the porosity of the ground, etc.
Some places will be sure to use levees, some won't.
With regards to crops, we don't know the outcome. If the Gulf stream stops or some regions dry out it could greatly affect crop yield, especially over the short-term. And that's all that matters for starvation to occur. The term year average yield isn't as important as this year's harvest.
Similarly, there is no reason to be very concerned about crops: we already are able to grow crops in a very wide variety of climates, and we have cultivars specially selected for local climate conditions. While climate change is very fast on geological scale, it’s rather slow on human scale, which gives us plenty of time to adjust our crops and farming patterns.
This is the biggest reason why climate change is not an existential threat: we are not going to sit on our thumbs, and watch the steamroller slowly ride over us, at speed of 1 cm per day. That’s not going to happen: mitigating the problems associated with climate change is rather simple, relative to other problems our societies solve on a regular basis, and we have a lot of time for it.