Guest geological perspective by David Middleton
There have been at least three recent peer-reviewed papers asserting an anthropogenic acceleration in the rate of sea level rise (SLR): Church & White, 2006 (CW06), Church & White, 2011 (CW11) and Nerem et al., 2018 (N18). N18 only covers the satellite era (since 1993) and might actually be correct, albeit irrelevant. The primary culprits in the SLR acceleration scam are CW06 and CW11. Two other recent peer-reviewed papers clearly shoot down the notion of a recent anthropogenic acceleration: Jevrejeva et al., 2008 (J08) and Jevrejeva et al., 2014 (J14). This post will focus on CW11 (updated through 2013) and J14.
J08 and J14 indicate that the acceleration, to the extent there is one, started 150-200 years ago, consistent with the end of neoglaciation and that a quasi-periodic fluctuation (~60-yr cycle) is present. CW06 and CW11 also note the 19th Century acceleration; but also assert a more recent acceleration, presumably due to anthropogenic global warming. This SLR acceleration is, at worst, innocuous.
If this acceleration was maintained through the 21st century, sea level in 2100 would be 310 ± 30 mm higher than in 1990, overlapping with the central range of projections in the Intergovernmental Panel on Climate Change Third Assessment Report (IPCC TAR) [Church et al., 2001].CW06
310 mm from 1990-2100 is less than 3 mm/yr… Not much of an acceleration.
CW11 is about 100 mm lower than J14. For direct comparison I plotted CW11 on the secondary y-axis with a 100 mm offset.
J14 starts 60 years earlier than CW11, capturing the falling sea level at the end of neoglaciation and the Little Ice Age. We can see that J14 and CW11 match up pretty well from 1880-1930 and then again from about 1993 onward; but they are very different from 1930-1993. J14 exhibits an acceleration to 3.2 mm/yr from 1929-1963 and then a decceleration to less than 1 mm/yr from 1963-1993, after which it accelrates back to about 3.2 mm/yr.
CW11 totally misses this quasi-periodic fluctuation.
Which is right?
Three factors generally control the rate of sea level rise and fall:
- Water temperature and salinity changes (steric).
- Cryosphere changes (glacio-eustatic).
- Changes in the configurations of the continents and ocean basins (isostatic).
Isostatic processes are only relevant to globally averaged sea level changes taking place over thousands to millions of years and can be ignored for the purposes of this exercise.
Water temperature and sea level
When water is heated, it expands. When t cools, it contracts. Earth’s average sea surface temperature has generally been rising since the coldest part of the Little Ice Age, the 1600’s. While the sea surface can warm and cool fairly quickly, it takes more time for that heating and cooling to affect deeper waters. A lag between warming and sea level rise should be expected.
J14 matches up very well with sea surface temperature if a 20-year lag is applied to J14.
According to J14, SLR accelerated from 1.8 mm/yr (1882-1915) to 3.2 mm/yr (1929-1963) about 20 years after the onset of the early 20th Century warming period. It then decelerated to less than 1 mm/yr after the onset of the mid 20th Century cooling period.
Vermeer & Rahmstorff, 2009, concluded that a lag of more than 10 years should be expected in the response of sea level to temperature changes. CW06 also noted a ~20-yr lag between temperature change and SLR rate changes.
Between 1930 and 1960, GMSL rises faster than the quadratic curve at a rate of about 2.5 mm yr−1 (Figure 2c), following (with about a 20 year lag) the 1910 to 1940 period of more rapid global temperature rise [Folland et al., 2001].CW06
J14 exhibits a lagged response to the ~60 year temperature cycle (quasi-periodic fluctuation), CW11 does not. CW11 totally misses the mid-20th century cooling (“The Ice Age Cometh“) effect on SLR. This cooling was so significant that it even halted the rise in atmospheric CO2.
According to MacFarling-Meure:
The stabilization of atmospheric CO2 concentration during the 1940s and 1950s is a notable feature in the ice core record. The new high density measurements confirm this result and show that CO2 concentrations stabilized at 310–312 ppm from ~1940–1955. The CH4 and N2O growth rates also decreased during this period, although the N2O variation is comparable to the measurement uncertainty. Smoothing due to enclosure of air in the ice (about 10 years at DE08) removes high frequency variations from the record, so the true atmospheric variation may have been larger than represented in the ice core air record. Even a decrease in the atmospheric CO2 concentration during the mid-1940s is consistent with the Law Dome record and the air enclosure smoothing, suggesting a large additional sink of ~3.0 PgC yr-1 [Trudinger et al., 2002a]. The d13CO2 record during this time suggests that this additional sink was mostly oceanic and not caused by lower fossil emissions or the terrestrial biosphere [Etheridge et al., 1996; Trudinger et al., 2002a]. The processes that could cause this response are still unknown.
 The CO2 stabilization occurred during a shift from persistent El Niño to La Niña conditions [Allan and D’Arrigo, 1999]. This coincided with a warm-cool phase change of the Pacific Decadal Oscillation [Mantua et al., 1997], cooling temperatures [Moberg et al., 2005] and progressively weakening North Atlantic thermohaline circulation [Latif et al., 2004]. The combined effect of these factors on the trace gas budgets is not presently well understood. They may be significant for the atmospheric CO2 concentration if fluxes in areas of carbon uptake, such as the North Pacific Ocean, are enhanced, or if efflux from the tropics is suppressed.MacFarling-Meure et al., 2006
J14’s quasi-periodic fluctuations are clearly consistent with ocean temperatures.
Cryosphere and sea level
There are places on Earth that are so cold that water is frozen solid. These areas of snow or ice, which are subject to temperatures below 32°F for at least part of the year, compose the cryosphere. The term “cryosphere” comes from the Greek word, “krios,” which means cold.
Ice and snow on land are one part of the cryosphere. This includes the largest parts of the cryosphere, the continental ice sheets found in Greenland and Antarctica, as well as ice caps, glaciers, and areas of snow and permafrost. When continental ice flows out from land and to the sea surface, we get shelf ice.
The other part of the cryosphere is ice that is found in water. This includes frozen parts of the ocean, such as waters surrounding Antarctica and the Arctic. It also includes frozen rivers and lakes, which mainly occur in polar areas.
The components of the cryosphere play an important role in the Earth’s climate. Snow and ice reflect heat from the sun, helping to regulate our planet’s temperature. Because polar regions are some of the most sensitive to climate shifts, the cryosphere may be one of the first places where scientists are able to identify global changes in climate.NOAA
Glacier mass balance is a way to measure changes in the cryosphere. A glacier with a negative mass balance is losing more ice than it gains annually. A glacier with a positive mas balance is gaining more ice than it loses annually.
Global glacier mass balance has been negative since the end of neoglaciation in the mid-1800’s. When glaciers and ice sheets have negative mass balances, much of the meltwater eventually finds its way to the ocean and sea level rises. Over most of the past 150 years, more glaciers have been retreating (negative mass balance) than advancing (positive mass balance).
Another way to measure glacial advance and retreat is by changes in glacier length. Oerlemans, 2005 climate reconstruction was devised from changes in global stacked glacier length. The following graph overlays atmospheric CO2 and northern hemisphere temperatures on Oerlemans’ stacked glacier length plot.
In the extremely unlikely event that the climate models are right, 90% of the ice loss occurred before an anthropogenic fingerprint could be discerned.
We can see that the 20th Century quasi-periodic fluctuation is also present in Oerlemans’ stacked records of glacial length.
CW11, on the other hand, is not even close…
J14’s quasi-periodic fluctuations are clearly consistent with changes in the rates of glacier retreat CW11 is not.
A bizarre claim in Church & White 2006
The quadratic implies that the rate of rise was zero in about 1820 when GMSL was about 200 mm below present day values. This level is consistent with estimates from bench marks carved in rock in Tasmania in 1840 [Hunter et al., 2003] and the height of ancient Roman fish tanks [Lambeck et al., 2004], which implies virtually no long‐term average change in GMSL from the first century AD to 1800 AD.CW06
That’s simply wrong.
It is plainly obvious that Jevrejeva et al., 2014 is more consistent with climate and cryosphere changes than Church & White, 2011 and, therefore, more likely to be accurate.
I apologize for the total lack of sarcasm in this post and for not finding a clever way to insert horst schist and other geological euphemisms into at least one fracking sentence.
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