Sea Level Rise


Sea-level has undeniably been rising for the last 10,000 years, since the end of the last ice age. In the 130 years from 1870 to 2000, global sea level rose by about 200 mm. That’s 8 inches. This works out to about 1.5 mm/yr. Between 1950 (when the anthropogenic signature begins) and 2000, sea level rose about 75 mm (3 inches).

That’s a pretty decent historical record. 

A simple linear extrapolation of this trend gets you to 125 mm by 2100. That is an additional 5 inches or so. I’m not saying that is a good estimate of what will happen, but it’s probably a good starting point. In my view, it is probably towards the low end of what we would expect to see in the next 80 years. In a bay with 6-foot swings in tide twice daily, 5 inches is not going to change anything.


According to satellite data since 1993, the rate is about double the historical rate. If that trend were to continue, sea level will be another 10 inches above today’s level in 2100. This is about the same rate as sea level increased from 1930 to 1950 (before the anthropogenic signature), so this is not an extreme event.

Anything beyond that 5 inches has a high burden of proof on it. The IPCC does have scenarios that have numbers like what you have suggested 2 meters, but there are a lot of worst-case assumptions built into that.

So should we assume 10 inches and stop worrying? No! First, low-lying areas need to be smarter about development. Any area whose infrastructure is less than the high tide level is relying on pumps for drainage and sewage. The good news is that we have proven it can be done in Europe and New Orleans. The bad news is that it is energy-intensive and costly to maintain.




https://wattsupwiththat.com/2018/01/09/sea-level-rise-and-fall-part-4-getting-a-rise-out-of-nothing/ sea-level measurement includes adjustment calculations, e.g. what would the sea-level change have been if the ocean basins had not increased in volume. (WTF?)

https://wattsupwiththat.com/2018/02/04/the-fantasy-of-accelerating-sea-level-rise-just-got-hosed/

 https://wattsupwiththat.com/2018/05/dr-roy-spencer-on-the-sea-level-spat-between-gavin-and-willis/ If we assume that the trend before 1950 was natural (we really did not emit much CO2 into the atmosphere before then) and that the following increase in the trend since 1950 was 100% due to humans, we get a human influence of only about 0.3 inches per decade, or 1 inch every 30 years.

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