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Comment by reddog | Hacker News Reader

>New Orleans will be uninhabitable. The only question is when.

A very, very long time from now. According to the IPCC Sixth Assessment Report sea levels are projected to rise between .57 and 1.25 meters by 2120. So unless you have waves currently lapping against your back porch you, your kids, your grandkids and your great-grandkids will be OK in NO.

For context, sea levels have risen about .3 meters over the last hundred years and we have adapted without city evacuation and relocation.

https://sealevel.nasa.gov/ipcc-ar6-sea-level-projection-tool

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The midway point in the sea level tool you linked is actually 1.41m by 2100. That's 4.6 feet of sea level rise by the end of the century and this is based on our current models where we are continuously discovering more and more positive feedback mechanisms that is accelerating sea level rise. (https://www.science.org/news/2020/11/seas-are-rising-faster-...) Now those levee walls that were originally 13 feet high are now less than 9 feet from the water and no longer really capable of doing the job they were designed for. So we better build bigger walls to keep all the water out, so let's go back and spend billions and billions more to have bigger walls, which by the way encourages more and more people to move into flood prone areas. Then you really set things up for a black swan event where something unexpected causes a levee failure (b/c that's never happened before) and then a bunch of people die.

So maybe you and your kids MIGHT be okay, but your grandkids and your great-grandkids? probably not.

>The midway point in the sea level tool you linked is actually 1.41m by 2100.

No. Not sure where 1.41m is coming from. Take a closer look at the linked NASA site. You will need to click on the link labled "View global projection" (sorry, there isn't a direct link). You will see a graph labeled "Projected Sea-Level Rise Under Different SSP Scenarios". The midpoint highest rise of all seven of the scenarios for 2100 is just .88 meters and that's for the most pessimistic SSP5-8.5 Low Confidence scenario. The more likely scenarios are about 1-2 feet.

Your great-grandkids will be fine.

1.41m by 2100 is the projection for “Grand Isle”, the closest location in the model to New Orleans. Sea level and sea level rise is not uniform worldwide, so local predictions are very important. This is also true for temperature and other climate change impacts, and is one of the biggest improvements in the latest IPCC report.

It looks like all model scenarios agree fairly well out to 2100 both in the global projections and in projections for Grand Isle. Thus, I’d wager good money that New Orleans will see 1-2m sea level rise by 2100 regardless of any climate mitigations we perform.

Grand Isle (which Ida did a number on) is well south of NOLA in Jefferson Parish, and not part of the metro area. It exists for fishing and tourism.

What was the IPCC's expected sea level rise in that time though? 3mm?

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