CO2 Concentration Changes
Do Not Drive Sea Levels
From about 7000 years ago to 2000 years ago, or from the Mid- to Late-Holocene, atmospheric CO2 concentrations varied between only about 260 and 270 parts per million, or ppm. Such low CO2 concentrations are believed to be “safe” for the planet, as they are significantly lower than today’s levels, which have eclipsed 400 ppm in recent years. These high CO2 concentrations are believed to cause dangerous warming, rapid glacier melt, and catastrophic sea level rise.
And yet, despite the surge in anthropogenic CO2 emissions and atmospheric CO2 since the 20th century began, the UN’s Intergovernmental Panel on Climate Change (IPCC) has concluded that global sea levels only rose by 1.7 mm/yr during the entire 1901-2010 period, which is a rate of less than 7 inches (17 cm) per century. A new paper even suggests the global trend is better represented as closer to 1.3 mm/yr, or about 5 inches per century:
McAneney et al., 2017 “Global averaged sea-level rise is estimated at about 1.7 ± 0.2 mm year−1 (Rhein et al. 2013), however, this global average rise ignores any local land movements. Church et al. (2006) and J. A. Church (2016; personal communication) suggest a long-term average rate of relative (ocean relative to land) sea-level rise of ∼1.3 mm year.”
According to Wenzel and Schröter (2014), the acceleration rate for the sea level rise trend since 1900 has been just +0.0042 mm/yr, which is acknowledged by the authors to be “not significant” and well within the range of uncertainty (+ or – 0.0092 mm/yr) to put the overall 20th/21st century sea level rise acceleration rate at zero.
Further complicating the paradigm that contends changes in CO2 concentrations drive sea levels is the fact that ice core evidence affirms CO2 levels remained remarkably constant (fluctuating around 255 to 260 ppm) during the same period that there was an explosively fast rate of sea level rise — between 1 and 2 meters per century (about 10 times today’s rates) — between 12,000 to 8,000 years ago. Sea levels rose by ~60 meters during those 4,000 years while CO2 levels effectively remained constant.
And casting even more doubt on the assertion that variations in CO2 drive sea level rise is the fact that there is robust paleoclimate evidence to suggest that today’s mean sea levels as well as today’s sea level rise rates are both relatively low (from a historical standpoint) and also well within the range of natural variability. Nothing unusual is happening to sea levels today. For even though we have evidence that modern CO2 concentrations (~405 ppm) are historically high relative to the last 10,000 years, we also possess a growing body of evidence that modern sea levels are still about 1 to 2 meters lower than they have been for most of the last 7,000 years.
The fundamental problem for the CO2-rise-causes-sea-level-rise paradigm, then, is that rising CO2 concentrations have not been correlated with rising sea levels for nearly all of the last 12,000 years. In fact, the opposite has been observed during the last 2,000 years, or during the Late Holocene: CO2 levels have risen (gradually, then rapidly) while sea levels have fallen overall, with recent changes so modest (inches per century) that they do not override the overall trend. In the 8,000 years before that, sea levels rose rapidly while CO2 concentrations remained flat. Simply put, the supposed anthropogenic “signal” in sea level rise trends has largely gone undetected — a point that has been affirmed by more and more scientists.
Listed below are a collection of 35 scientific papers published since 2014 that indicate sea levels were, on average, about 1 to 2 meters higher than they are now throughout the Mid-Holocene (7,000-2,000 years ago) and even into the last millennium, with lower-than-now sea levels largely confined to the Little Ice Age period (~1300 to 1900 AD). Links to the papers are embedded in the authors’ names and the regional locations for mean sea level are notated.
Dechnik et al., 2017 (Tropical Western Pacific)
[I]t is generally accepted that relative sea level reached a maximum of 1–1.5 m above present mean sea level (pmsl) by ~7 ka [7,000 years ago] (Lewis et al., 2013)
Zondervan, 2016 (Great Barrier Reef, Australia)
Preserved fossil coral heads as indicators of Holocene high sea level on One Tree Island [GBR, Australia] … Complete in-situ fossil coral heads have been found on beach rock of One Tree Island, a small cay in the Capricorn Group on the Great Barrier Reef. Measurements against the present low-tide mark provide a [Holocene] high stand of at least +2.85 m [above present sea levels], which can be determined in great accuracy compared to other common paleo sea-level record types like mangrove facies. The sea level recorded here is higher than most recent findings, but supports predictions by isostatic adjustment models. … Although the late Holocene high stand has been debated in the past (e.g. Belperio 1979, Thom et al. 1968), more evidence now supports a sea level high stand of at least + 1- 2 m relative to present sea levels (Baker & Haworth 1997, 2000, Collins et al. 2006, Larcombe et al. 1995, Lewis et al. 2008, Sloss et al. 2007).
Prieto et al., 2016 (Argentina, Uruguay)
Analysis of the RSL [relative sea level] database revealed that the RSL [relative sea level] rose to reach the present level at or before c. 7000 cal yr BP, with the peak of the sea-level highstand c. +4 m [above present] between c. 6000 and 5500 cal yr BP [calendar years before present] … This RSL [relative sea level] curve was re-plotted by Gyllencreutz et al. (2010) using the same index points and qualitative approach but using the calibrated ages. It shows rising sea-levels following the Last Glacial Termination (LGT), reaching a RSL [relative sea level] maximum of +6.5 m above present at c. 6500 cal yr BP [calendar years before present], followed by a stepped regressive trend towards the present.
Hodgson et al., 2016 (East Antarctica)
Rapid early Holocene sea-level rise in Prydz Bay, East Antarctica … The field data show rapid increases in rates of relative sea level rise of 12–48 mm/yr [1.2 to 4.8 meters per century] between 10,473 (or 9678) and 9411 cal yr BP in the Vestfold Hills and of 8.8 mm/yr between 8882 and 8563 cal yr BP in the Larsemann Hills. … The geological data imply a regional RSL [relative sea level] high stand of c. 8 m [above present levels], which persisted between 9411 cal yr BP and 7564 cal yr BP [calendar years before present], and was followed by a period when deglacial sea-level rise was almost exactly cancelled out by local rebound.
Dura et al., 2016 (Vancouver)
In northern and western Sumatra, GIA models predict high rates (>5 mm/year) of RSL [relative sea level] rise from ∼12 to ∼7 ka [12000 to 7000 years ago], followed by slowing rates of rise (<1 mm/year) to an RSL [relative sea level] highstand of <1 m (northern Sumatra) and ∼3 m (western Sumatra) between 6 and 3 ka [6,000-3,000 years ago], and then gradual (<1 mm/ year) RSL fall until present.
Spotorno-Oliveira et al., 2016 (Brazil)
At ~7000 cal. years BP the sea level in the bay was approximately 4 m below the present sea level and the upper subtidal benthic community was characterised by fruticose corallines on coarse soft substrate, composed mainly of quartz grains from continental runoff input. The transgressing sea rapidly rose until reaching the ~ +4 m highstand [above present] level around 5000 years BP.
Lee et al., 2016 (Southeast Australia)
The configuration suggests surface inundation of the upper sediments by marine water during the mid-Holocene (c. 2–8 kyr BP), when sea level was 1–2 m above today’s level.
Yokoyama et al., 2016 (Japan)
The Holocene-high-stand (HHS) inferred from oyster fossils (Saccostrea echinata and Saccostrea malaboensis) is 2.7 m [above present sea level] at ca. 3500 years ago, after which sea level gradually fell to present level.
May et al., 2016 (Western Australia)
Beach ridge evolution over a millennial time scale is also indicated by the landward rise of the sequence possibly corresponding to the mid-Holocene sea-level highstand of WA [Western Australia] of at least 1-2 m above present mean sea level.
Mann et al., 2016 (Indonesia)
Radiometrically calibrated ages from emergent fossil microatolls on Pulau Panambungan indicate a relative sea-level highstand not exceeding 0.5 m above present at ca. 5600 cal. yr BP [calendar years before present].
Clement et al., 2016 (New Zealand)
In North Island locations the early-Holocene sea-level highstand was quite pronounced, with RSL [relative sea level] up to 2.75 m higher than present. In the South Island the onset of highstand conditions was later, with the first attainment of PMSL being between 7000–6400 cal yr BP. In the mid-Holocene the northern North Island experienced the largest sea-level highstand, with RSL up to 3.00 m higher than present.
Long et al., 2016 (Scotland)
RSL [relative sea level] data from Loch Eriboll and the Wick River Valley show that RSL [relative sea level] was <1 m above present for several thousand years during the mid and late Holocene before it fell to present.
Chiba et al., 2016 (Japan)
Highlights: We reconstruct Holocene paleoenvironmental changes and sea levels by diatom analysis. Average rates of sea-level rise and fall are estimated during the Holocene. Relative sea level during Holocene highstand reached 1.9 m [higher than today] during 6400–6500 cal yr BP [calendar years before present]. The timing of this sea-level rise is at least 1000 years earlier in the Lake Inba area by Holocene uplift than previous studies. The decline of sea-level after 4000 cal yr BP may correspond to the end of melting of the Antarctic ice sheet.
Leonard et al., 2016 (Great Barrier Reef, Australia)
Holocene sea level instability in the southern Great Barrier Reef, Australia … Three emergent subfossil reef flats from the inshore Keppel Islands, Great Barrier Reef (GBR), Australia, were used to reconstruct relative sea level (RSL). Forty-two high-precision uranium–thorium (U–Th) dates obtained from coral microatolls and coral colonies (2σ age errors from ±8 to 37 yr) in conjunction with elevation surveys provide evidence in support of a nonlinear RSL regression throughout the Holocene. RSL [relative sea level] was at least 0.75 m above present from ~6500 to 5500 yr before present (yr BP; where “present” is 1950). Following this highstand, two sites indicated a coeval lowering of RSL of at least 0.4 m from 5500 to 5300 yr BP which was maintained for ~200 yr. After the lowstand, RSL returned to higher levels before a 2000-yr hiatus in reef flat corals after 4600 yr BP at all three sites. A second possible RSL lowering event of ~0.3 m from ~2800 to 1600 yr BP was detected before RSL stabilised ~0.2 m above present levels by 900 yr BP. While the mechanism of the RSL instability is still uncertain, the alignment with previously reported RSL oscillations, rapid global climate changes and mid-Holocene reef “turn-off” on the GBR are discussed.
Sander et al., 2016 (Denmark)
The data show a period of RSL [relative sea level] highstand at c. 2.2 m above present MSL [mean sea level] between c. 5.0 and 4.0 ka BP [5,000 to 4,000 years before present]. After that, RSL drops by c. 1.3 m between c. 4.0 and 3.4 ka BP to an elevation roughly 1 m above present MSL. Since then, RSL has been falling at more or less even rates. … Yu et al. (2007) present evidence for a sea-level ‘jump’ of several meters occurring at 7.6 ka bp [7600 years before present] in SE Sweden, and data suggesting RSL changes with a similar timing and magnitude were obtained for a field site in the southern Gulf of Finland (Rosentau et al., 2013). The suddenness of the RSL change has been attributed to the collapse of parts of the Laurentide Ice Sheet (Blanchon and Shaw, 1995; Carlson et al., 2007), though the global indications and the potential triggers of such a eustatic event remain inconclusive (Törnqvist and Hijma, 2012).
Bradley et al., 2016 (China)
In general, the data indicate a marked slowdown between 7 and 8 kyr BP, with sea level rising steadily to form a highstand of ~2-4 m [above present sea level] between 6 and 4 kyr BP [6000 and 4000 years before present]. This is followed by a steady fall, reaching present day levels by ~1 kyr BP.
Accordi and Carbone, 2016 (Africa)
Then, the skeletal carbonate storage on the shelf reached its maximum 5 to 4 ka BP [5000 to 4000 years before present] (Ramsay, 1995) during a highstand about 3.5 m above the present sea level, when shallow marine accommodation space was greater than at present. … A detailed sea level curve of the last 9 ka BP is reported for the Southern African coastline by Ramsay (1995), who indicates a sea level similar to that of the present (at about 6.5 ka). Ramsay also indicates successive, frequent oscillations below and above the present sea level, between a maximum of +3.5 and a minimum of -2 m. Sea level positive pulses since 7 ka BP are also documented in Siesser (1974), Jaritz et al. (1977) and Norstrom et al. (2012) for the Mozambique coast. Along the Kenyan coast, a sea level stand above the present one during the mid-Holocene is documented in many places along the coast by various authors (Hori, 1970; Toyah et al., 1973; Åse, 1981, 1987; Oosterom, 1988), where the sea level might have reached +6 m above the Kenyan Datum between 2 and 3 ka BP [2000 and 3000 years before present].
Hansen et al., 2016 (Denmark)
Continuous record of Holocene sea-level changes … (4900 years BP to present). … The curve reveals eight centennial sea-level oscillations of 0.5-1.1 m superimposed on the general trend of the RSL [relative sea level] curve [relative sea levels ~1.5 m higher than present from 1400 to 1000 years ago].
Macreadie et al., 2015 (Austalia, Eastern)
[R]esults from other studies … suggest that high-stand, at perhaps 2 m above present msl [mean sea level] was achieved as early as 7000 radiocarbon years BP [before present] (7800 cal. years BP) and that sea-level has exceeded the present value for much of the mid- to late-Holocene [~7000 to ~1000 years ago].
Lewis et al., 2015 (Australia, Northeastern)
Thick (> 10 cm) fossil oyster visors above the equivalent modern growth suggest higher relative sea-levels in the past (i.e. > 1200 cal. yr BP [prior to 1,200 years before present]). … [D]ata show a Holocene sea-level highstand of 1–2 m higher than present which extended from ca. 7500 to 2000 yr ago (Woodroffe, 2003; Sloss et al., 2007; Lewis et al., 2013). The hydro-isostatic adjustment is thought to account for these 1–2 m sea-level changes [falling] to present levels over the past 2000 yr (Lambeck and Nakada, 1990; Lambeck, 2002). … [R]eliable SLI data such as coral pavements and tubeworms from Western Australia suggest that relative sea-level was 0.86 m and 0.80 m above present at 1060 ± 10 and 1110 ± 170 cal. yr BP [~1100 calendar years before present], respectively (Baker et al., 2005; Collins et al., 2006).
Lokier et al., 2015 (Persian Gulf)
Late Quaternary reflooding of the Persian Gulf climaxed with the mid-Holocene highstand previously variously dated between 6 and 3.4 ka. Examination of the stratigraphic and paleoenvironmental context of a mid-Holocene whale beaching allows us to accurately constrain the timing of the transgressive, highstand and regressive phases of the mid- to late Holocene sea-level highstand in the Persian Gulf. Mid-Holocene transgression of the Gulf surpassed today’s sea level by 7100–6890 cal yr BP, attaining a highstand of > 1 m above current sea level shortly after 5290–4570 cal yr BP before falling back to current levels by 1440–1170 cal yr BP. These new ages refine previously reported timings for the mid- to late Holocene sea-level highstand published for other regions. By so doing, they allow us to constrain the timing of this correlatable global eustatic event more accurately.
Harris et al., 2015 (Great Barrier Reef, Australia)
This hiatus in sediment infill coincides with a sea-level fall of ∼1–1.3 m during the late Holocene (ca. 2000 cal. yr B.P.), which would have caused the turn-off of highly productive live coral growth on the reef flats currently dominated by less productive rubble and algal flats, resulting in a reduced sediment input to back-reef environments and the cessation in sand apron accretion. Given that relative sea-level variations of ∼1 m were common throughout the Holocene, we suggest that this mode of sand apron development and carbonate production is applicable to most reef systems.
Microatoll death was most likely caused by a fall in sea level that stranded the microatolls on the reef flat due to their location in open-water unmoated environments. This suggests that paleo–sea level between 3900 and 2200 cal. yr B.P. was 1–1.3 m higher than present (based on an offset from MLWS tidal level to fossil microatoll elevation; Fig. 2). This paleo–sealevel elevation is similar to the ranges of 1–1.5 m suggested by Lewis et al. (2013) and Sloss et al. (2007) and data from Moreton Bay in southern Queensland of an elevation of 1.3 m (Leonard et al., 2013).
Hein et al., 2015 (Brazil)
In southern Brazil, falling RSL [relative sea level] following a 2–4 m [above present sea level] highstand at 5 to 6 ka [5,000 to 6,000 years ago] forced coastal progradation. … Relative SL [sea level] along the southern Brazil coast reached a highstand elevation of 1–4 m above MSL [mean sea leve] at ca. 5.8 ka [5800 years ago].
Barnett et al., 2015 (Arctic Norway)
Relative sea-level fell at −0.7 to −0.9 mm yr−1 over the past 3300 years in NW Norway. … Prior to 3000 cal yr BP the marine limiting date represents an important constraint for the late Holocene sea-level trend and yields a minimum RSL [relative sea level] decline of approximately 2.2 m over 3200 years when assuming a linear trend. The maximum possible linear decline constrained by the data is approximately 2.6 m in 2800 years, providing an estimated late Holocene sea-level trend of 0.7 to 0.9 mm yr (shown by the grey shaded region in Fig. 8A). [Relative sea level was 2.2 to 2.8 m higher ~3,000 years ago in Arctic Norway]
Engel et al., 2015 (Western Australia)
The foredunes overlie upper beach deposits located up to >2 m above the present upper beach level and provide evidence for a higher mid-Holocene RSL [relative sea level]. … [O]bservations made near Broome by Lessa and Masselink (2006) [indicate] the deposition of backshore deposits up to c. 1.5 m above present MHW [mean high water] between c. 2100–800 cal BP [2100-800 calendar years before present].
Reinink-Smith, 2015 (Kuwait)
[B]ased on bottle characteristics, glass bottles within the debris zonemwere manufactured mostly between 1940 and 1960 (some as early as the 1920s), indicating high tides were more common in the recent past. … The normal tidal cycle affects only a narrow 0.6–0.7 km-wide band parallel to the coast when the prevailing wind (the Shamal) is from the northwest (Gunatilaka, 1986). Within this narrow zone, washed-up glass bottles were manufactured more recently than ~1960 and are not frosted. None of these new [made after 1960] bottles were found near the beach ridges … [A]ssuming the tidal ranges were similar in the middle Holocene, a rough estimate of the MSL [mean sea level] during the middle Holocene highstand is 5.2 m − 1.7 m = +3.5 m above the present MSL [mean sea level]. … The +3.5 m highstand estimate in northeastern Kuwait derived in this study is also higher than the previously reported maximum estimates of +2 to +2.5 m responsible for other Holocene beach ridges in the Arabian Gulf (Gunatilaka, 1986; Lambeck, 1996; Kennett and Kennett, 2007; Jameson and Strohmenger, 2012). Some beach ridges in Qatar and Abu Dhabi are at elevations of 2–4 m above MSL [present mean sea level] as far as 5-15 km inland (Alsharhan and Kendall, 2003).
Rashid et al., 2014 (French Polynesia)
Upon correction for isostatic island subsidence, we find that local relative sea level was at least ~1.5±0.4 m higher than present at ~5,400 years ago.
Strachan et al., 2014 (South Africa)
During the last 7000 years, southern African sea levels have fluctuated by no more than ±3 m. Sea-level curves based on observational data for southern Africa indicate that Holocene highstands occurred at 6000 and again at 4000 cal years BP, followed by a lowstand from 3000 to 2000 cal years B P. The mid-Holocene highstands culminated in a sea-level maximum of approximately 3 m above mean sea level (MSL) from 7300 to 6500 cal years BP [calendar years before present] and of 2 m above MSL at around 4000 cal years BP. Thereafter, RSL dropped to slightly below the present level between 3500 and 2800 cal years BP. Sea-level fluctuations during the late Holocene in southern Africa were relatively small (1-2 m); however, these fluctuations had a major impact on past coastal environments. Evidence from the west coast suggests that there was a highstand of 0.5 m above MSL from 1500 to 1300 cal years BP [calendar years before present] or possibly earlier (1800 cal years BP), followed by a lowstand (-0.5 m above MSL) from 700 to 400 cal years BP [during the Little Ice Age].
Yamano et al., 2014 (Southwest Pacific Ocean)
Mba Island initially formed around ~ 4500 cal yr B.P. [4500 calendar years before present], when sea level was ~ 1.1 m higher than at present.
Kench et al., 2014 (Central Pacific Ocean)
[T]he mid-Holocene [sea level] highstand is reported to have peaked at approximately +1.1 m above present and was sustained until approximately 2000 years B.P. [before present] in the Marshall Islands.
Hein et al., 2014 (Brazil)
Along the eastern and southern Brazilian coasts of South America, 6000 years of sea-level fall have preserved late-stage transgressive and sea-level highstand features 1–4 m above present mean sea level and several kilometers landward of modern shorelines.
Bracco et al., 2014 (Uruguay)
Highlights: We present a sea level change curve for mid Holocene in Uruguay. Sea level reached 4 m amsl [above present mean sea level] between 6000 and 5500 yr BP [before present]. A rapid sea level fall to about 1 m amsl [above present mean sea level] was inferred for 4700-4300 yr BP. A further sea level increase to about 3 m amsl [above present mean sea level] was inferred after 4300 yr BP. After 4300 yr BP there was a constant sea level a decline.
Holocene Sea Levels Rose Much Faster With Stable CO2 Levels
Khan et al., 2017 (Caribbean)
Only Suriname and Guyana [Caribbean] exhibited higher RSL [relative sea level] than present (82% probability), reaching a maximum height of ∼1 m at 5.2 ka [5,200 years ago]. … Because of meltwater input, the rates of RSL change were highest during the early Holocene, with a maximum of 10.9 ± 0.6 m/ka [10.9 meters per 1000 years, 1.9 meters per century] in Suriname and Guyana and minimum of 7.4 ± 0.7 m/ka [7.4 meters per 1000 years, 0.74 meters per century] in south Florida from 12 to 8 ka [12,000 to 8,000 years ago].
Zecchin et al., 2015 (Mediterranean)
Episodic, rapid sea-level rises on the central Mediterranean shelves after the Last Glacial Maximum: A review … The evidence presented here confirms drowned shorelines documented elsewhere at similar water depths and shows that melt-water pulses have punctuated the post-glacial relative sea-level rise with rates up to 60 mm/yr. [6 meters per century] for a few centuries.
Boski et al., 2015 (Brazil)