Guest “For once, it’s not worse than previously thought” by David Middleton
But it’s still disastrous … Because models …
Some past sea levels may not have been as high as thought, says a study of rising and falling land masses
But even scaled-down estimates, if applied to today, would be disastrous
BY KEVIN KRAJICK | AUGUST 9, 2021
One of the current mysteries of climate science surrounds the widely accepted evidence that global sea levels were up to 6 to 9 meters higher than they are today during the planet’s last natural warm period, about 128,000 to 117,000 years ago. And during this so-called last interglacial period, temperatures were only 1 or 2 degrees Celsius warmer than in pre-industrial times – marks that we will surpass by the end of the century, if not earlier. Such a flood could only have been caused by the collapse of the Greenland and / or Antarctic ice sheets. If that happens now, it will drown much of the human world. But at least so far, the models of future sea level rise usually fluctuate by a meter or so within the next 100 years. What are we missing and how much should that scare us?
In a new study, a team at Columbia University’s Lamont-Doherty Earth Observatory believe they have an answer: They say researchers studying evidence of past sea levels along different coasts may not have accurately corrected the country’s long-term ups and downs itself. Based on new sophisticated measurements taken in the Bahamas, as well as new methods of data analysis, the researchers made lower – if still frightening – estimates for the most recent interglacial. They say the seas were at least four feet taller than they are today – roughly in line with most current models for the next 100 years.
[…]
They combined these results with hundreds of different models showing how the isostatic rebound of glaciers might have moved through the earth and converted the calculations into global sea level. This led to the new, lower estimates.
[…]
Columbia Climate School
This is undiminished clump slate:
They say the seas were at least four feet taller than they are today – roughly in line with most current models for the next 100 years.
Sea level reconstructions over the past 100-200 years show an increase in sea level of 1.6-1.9 mm / year.
Figure 1. Jevrejeva et al., 2014 (red) and Church & White, 2011 (green).
The total rise in sea level over this period is roughly the length of an Estwing rock needle
Figure 2. J14 vs. CW11. 310 mm is less than the length of an Estwing rock pick. The green curve is the pentadal (5 year) average of CW11. The red curve is the pentadal mean of J14. The y-axis of CW11 is shifted up 100mm to connect J14.
J14 starts 60 years earlier than KW11 and captures the sinking sea level at the end of the Neoglaziation and the Little Ice Age. We can see that J14 and CW11 go together pretty well from 1880-1930 and then again from about 1993; but they are very different from 1930-1993. J14 shows an acceleration to 3.2 mm / year from 1929-1963 and then a deceleration to less than 1 mm / year from 1963-1993, after which it accelerates again to about 3.2 mm / year.
Figure 3. J14 vs. CW11. Which is the geologist’s choice? Black curve = J14. Green curve = CW11.
Jevrejeva et al., 2008 (J08) and Jevrejeva et al., 2014 (J14) indicate that the acceleration, if any, began 150-200 years ago, which coincides with the end of the neoglaciation and fluctuation (~ 60- Year cycle) is available. Church & White, 2006 (CW06) and Church & White, 2011 (CW11) also point to the acceleration of the 19th century; but also claim a more recent acceleration, presumably due to anthropogenic global warming. This SLR acceleration is harmless in the worst case.
If this acceleration were maintained in the 21st century, sea levels would be 310 ± 30 mm higher in 2100 than in 1990, which overlaps the central projection area of the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC TAR). [Church et al., 2001].
KW06
310mm from 1990-2100 is less than 3mm / year … Not a huge acceleration and far from being 1.2m and “roughly in line with most current models for the next 100 years”.
Apart from the fact that Doctor Evil suddenly melts the Greenland ice sheet with a “space laser”, it would be physically impossible for the sea level to rise another 1.2 m “in the next 100 years”.
In order for the sea level to rise by 850 mm by the end of this century, it would have to accelerate to a speed of ~ 20 mm / year from 2081 to 2100. This is almost double the Holocene transgression.
Figure 4. “You can’t get there from here.”
The sea level rose by about 100 m during the Holocene Trangression.
Figure 5. Global increase in seal level during the Holocene Transgression. MWP 1A occurred at ~ 14.6 kya. Note that the error bar is ± 12 meters. Older is right.
(Siddall et al., 2003)
This catastrophic sea level rise, including boogie man Meltwater Pulse 1A, came at a time when the earth had much more ice to melt than it does today.
Having fun with sea level
Here J14 is drawn to the same vertical scale as the Statue of Liberty …
Figure 7. Lady Liberty has nothing to fear from the Adjustocene Sea. What is it? Can’t see the sea level trend? It’s right down there at sea level … between the water and the base of Liberty Island. (Junk Science from National Geographic: How Long Will It Take For Sea Levels To Reach Half The Statue Of Liberty ?, Anthony Watts)
References
Church, JA, and White, NJ (2006). “An Acceleration of Global Sea Level Rise in the 20th Century”. Geophysics. Res. Lett., 33, L01602, doi: 10.1029 / 2005GL024826.
Church, JA, White, NJ, 2011. “Sea Level Rise from the Late 19th Century to the Early 21st Century”. Survival geophysics. http://dx.doi.org/10.1007/s10712-011-9119-1.
Jevrejeva, S., JC Moore, A. Grinsted and PL Woodworth (2008). “The recent global sea level acceleration started over 200 years ago?” Geophysics. Res. Lett., 35, L08715, doi: 10.1029 / 2008GL033611.
Jevrejeva, S., JC Moore, A. Grinsted, AP Matthews, G. Spada. 2014. “Trends and Acceleration in Global and Regional Sea Levels since 1807”. Global and planetary change. % vol 113, 10.1016 / j.gloplacha.2013.12.004 https://www.psmsl.org/products/reconstructions/jevrejevaetal2014.php
Siddall M, Rohling EJ, Almogi-Labin A, Hemleben C, Meischner D, Smelzer I, Smeed DA (2003). “Sea level fluctuations during the last ice age cycle”. Nature 423: 853-858
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