Sea Level Rise is Accelerating Dramatically • Watts Up With That?

Image above: The blue Crawley Edge Boatshed is a well-recognized and frequently photographed site in Perth. It is thought to have been constructed in the early 1930s and has since been refurbished. Note that in almost 100 years, it has not been overwhelmed by sea level rise.

The arguments and claims for this being an issue of concern:

Climate Change is causing rising sea levels to accelerate, threatening to displace millions of people.

From NASA:

Global sea level rise is accelerating incrementally over time rather than increasing at a steady rate, as previously thought, according to a new study based on 25 years of NASA and European satellite data.

If the rate of ocean rise continues to change at this pace, sea level will rise 26 inches (65 centimeters) by 2100 — enough to cause significant problems for coastal cities, according to the new assessment by Nerem and colleagues from NASA’s Goddard Space Flight Center in Greenbelt, Maryland; CU Boulder; the University of South Florida in Tampa; and Old Dominion University in Norfolk, Virginia.
Source: https://climate.nasa.gov/news/2680/new-study-finds-sea-level-rise-accelerating.

NASA: Global sea level rise is accelerating incrementally over time rather than increasing at a steady rate, as previously thought, according to a new study based on 25 years of NASA and European satellite data. If the rate of ocean rise continues to change at this pace, sea level will rise 26 inches (65 centimeters) by 2100—enough to cause significant problems for coastal cities. Credit: NASA’s Goddard Space Flight Center/Kathryn Mersmann.

The argument for this being an overhyped issue of little concern:

Sea level rise is not drastically accelerating, and not an imminent threat

Most of the recent alarmism on sea level rise has been due to climate model projections, which foresee a drastic and accelerating increase in sea level rise in the future.

Ocean tide gauge data shows that the sea level trend has not changed in over 100 years, and show no signs of drastic acceleration. In New York City, sea level has risen only 0.94 feet in 100 years, and started well before human carbon dioxide emissions were significant. The trend is unchanged since 1856. All of the perceived acceleration comes from satellite measurements and could be within the range of measurement error.

According to tide gauge data, global sea levels are rising at a rate of about 7-8 inches per century, a rate that has remained steady despite our escalating carbon dioxide emissions, i.e. the cause is probably predominantly natural. We could globally cease all carbon dioxide emissions overnight and sea levels would continue to rise, an inevitability to which we must adapt. There’s simply no drastic acceleration of sea level rise. There is some recent sea level rise that could be called acceleration, but it is small, and short term, and may be due to natural variance.

If we assume that the trend prior to 1950 was natural (humans 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.

Even though it looks like there is some evidence of even stronger acceleration more recently, sea level has varied naturally on multi-decadal time scales, and it is dangerous to extrapolate any short-term trends far into the future.

In a peer-reviewed paper⁴ by well-respected oceanographer, Carl Wunsch, he said:

At best, the determination and attribution of global-mean sea-level change lies at the very edge of knowledge and technology. Both systematic and random errors are of concern, the former particularly, because of the changes in technology and sampling methods over the many decades, the latter from the very great spatial and temporal variability. It remains possible that the database is insufficient to compute mean sea-level trends with the accuracy necessary to discuss the impact of global warming, as disappointing as this conclusion may be.

In an article discussing the measurement capabilities of satellites, author Rud Istvan stated:⁵

There are strong evidentiary reasons to think satellite altimetry does NOT accurately represent SLR change over time. The two most irrefutable observational reasons are:

(1) Satellite altimetry measured trends are about 1.5x higher than differential GPS, (vertical land motion) corrected long record tide gauges (about 3.4 versus about 2.2 mm/yr)

(2) the dGPS tide gauge estimates roughly close, while Jason2 satellite altimetry estimates definitely do NOT. Per my previous above referenced guest post, ‘closure’ is the simple arithmetic that SLR must approximately equal thermosteric rise, as hotter seawater expands in volume, plus ice sheet losses (land based ice when melted adds ocean water), while all other contributions, such as ground water extraction are arguably de minimus.)
Source: http://ocean.mit.edu/~cwunsch/papersonline/Wunschetal_jclimate_2007_published.pdf

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