essential read - "Sea Level Rise is Accelerating, Says Unnerving New Research"
Weather Underground article
https://www.wunderground.com/cat6/sea-level-rise-accelerating-says-unnerving-new-research
Not only is sea level rising, it is rising at an increasing amount each year, found a hugely important study of global sea level published on Monday in Proceedings of the National Academy of Sciences. The paper, Climate-change–driven accelerated sea-level rise detected in the altimeter era, looked at 25 years of satellite-based global sea level measurements taken by four satellites. The researchers found that global sea levels rose by an average of 3 millimeters per year, plus or minus 0.4 mm/yr, but this rate has been accelerating by 0.084 ± 0.025 mm/y2 over the past 25 years. If this acceleration were to continue through the end of the century, global sea level rise between 2005 and 2100 would be about 26 inches (65 centimeters), which is more than double the rise of 11 inches (28 centimeters) that would occur if sea level rise stayed constant at 3 mm/yr.
Uncertainties
There are many corrections that must be made to the 25-year period of the data in order to precisely determine global sea level acceleration. In particular, potential drifts in the instruments over time must be accounted for, as well as changes in water storage on land due to the natural El Niño and La Niña cycle, ice sheet mass loss that might masquerade as a long-term acceleration over a 25-year record, and episodic variability driven by large volcanic eruptions. After correcting for all these factors, the researchers concluded that the probability that the acceleration in sea level rise is zero was less than 1%.
Future sea level rise likely to be higher
The scientists commented that their estimate might represent a conservative lower bound on future sea level change, since rapid changes in the stability of the Greenland and Antarctic ice sheets could be expected to cause higher accelerations of sea level rise in the future. They added: “In contrast, few potential processes exist to suggest that this estimate is too high.”
Predictions of sea level rise from the IPCC and National Climate Assessment
The prediction by the scientists that global sea level rise would reach 26” by 2100 is well within the estimates of sea level rise from the 2013 Intergovernmental Panel on Climate Change (IPCC) report and the Climate Science Special Report from the 2017 U.S. Fourth National Climate Assessment (NCA). According to the 2017 NCA report, global mean sea level rose about 4 - 5 inches (11 - 14 cm) from 1901 to 1990, and about 3 inches (7 cm) in the comparatively brief period since 1990. Here are the four scenarios the report gave for sea level rise (the low end is comparable to a linear extension of the recent rate of 3 mm/year, while the high end is a very-bad-case scenario, including rapid ice loss in Antarctica):
Projected rises in global mean sea level from 2000 to the year shown:
Low: 0.2’ by 2020, 0.5’ by 2050, 1.0’ by 2100
Intermediate: 0.3’ by 2020, 1.1’ by 2050, 3.3’ by 2100
High: 0.4’ by 2020, 1.8’ by 2050, 6.6’ by 2100
Extreme: 0.4’ by 2020, 2.1’ by 2050, 8.2’ by 2100
(with further rises expected after 2100)
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last paragraph
“Like it or not, we will retreat from most of the world’s non-urban shorelines in the not very distant future. Our retreat options can be characterized as either difficult or catastrophic. We can plan now and retreat in a strategic and calculated fashion, or we can worry about it later and retreat in tactical disarray in response to devastating storms. In other words, we can walk away methodically, or we can flee in panic.
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