from CO2 Science: The authors write that “satellite altimetry measurements since 1993 have provided unique information about changes in global and regional mean sea levels,” suggesting a mean rate of rise of 3.2 mm/yr for global sea level over the period 1993-2012 (Boening et al., 2012; Cazenave et al., 2012), which “notably exceeds the estimate of 1.8 mm/yr sea level rise for the 20th century (Bindoff et al., 2007).”
So which rate is closest to the truth?
What was done
In a study designed to answer this question, Jevrejeva et al. (2014) say they “renew the global sea level [GSL] reconstruction by Jevrejeva et al. (2006), using monthly mean sea level data collected by the Permanent Service for Mean Sea Level (PSMSL) covering the observations from 1807 to 2010,” thereby improving the GSL reconstruction by increasing data coverage “by using many more stations, particularly in the polar regions, and recently processed historic data series from isolated island stations,” as well as by extending the end of the reconstruction from 2002 to 2009.
What was learned
Quoting the five researchers, “the new reconstruction suggests a linear trend of 1.9 ± 0.3 mm/yr [7.5 inches per century] during the 20th century” and “1.8 ± 0.5 mm/yr [7 inches per century] for the period 1970-2008.”
Global sea level reconstruction since 1807, blue shadow represents 5 and 95% confidence interval
What it means
Although some regions have recently experienced much greater rates of sea level rise, such as the Arctic (3.6 mm/yr) and Antarctic (4.1 mm/yr), with the mid-1980s even exhibiting a rate of 5.3 mm/yr (Holgate, 2007), this newest analysis of the most comprehensive data set available suggests that there has been no dramatic increase – or any increase, for that matter – in the mean rate of global sea level rise due to the historical increase in the atmosphere’s CO2 concentration.[Therefore, there is no evidence of any human influence on sea levels]
The paper:
Trends and acceleration in global and regional sea levels since 1807. Global and Planetary Change 113: 11-22. Jevrejeva, S., Moore, J.C., Grinsted, A., Matthews, A.P. and Spada, G. 2014.
We use 1277 tide gauge records since 1807 to provide an improved global sea level reconstruction and analyse the evolution of sea level trend and acceleration. In particular we use new data from the polar regions and remote islands to improve data coverage and extend the reconstruction to 2009. There is a good agreement between the rate of sea level rise (3.2 ± 0.4 mm·yr− 1) calculated from satellite altimetry and the rate of 3.1 ± 0.6 mm·yr− 1 from tide gauge based reconstruction for the overlapping time period (1993–2009). The new reconstruction suggests a linear trend of 1.9 ± 0.3 mm·yr− 1 during the 20th century, with 1.8 ± 0.5 mm·yr− 1 since 1970. Regional linear trends for 14 ocean basins since 1970 show the fastest sea level rise for the Antarctica (4.1 ± 0.8 mm·yr− 1) and Arctic (3.6 ± 0.3 mm·yr− 1). Choice of GIA correction is critical in the trends for the local and regional sea levels, introducing up to 8 mm·yr− 1 uncertainties for individual tide gauge records, up to 2 mm·yr− 1 for regional curves and up to 0.3–0.6 mm·yr− 1 in global sea level reconstruction. We calculate an acceleration of 0.02 ± 0.01 mm·yr− 2 in global sea level (1807–2009). In comparison the steric component of sea level shows an acceleration of 0.006 mm·yr− 2 and mass loss of glaciers accelerates at 0.003 mm·yr− 2 over 200 year long time series.
Full paper with figures is available here: http://www.sciencedirect.com/science/article/pii/S0921818113002750#f0015
Nick Stokes says:
Greg,
“In theory glacial rebound can not be accelerating. This means there is a problem somewher”
In theory it isn’t. The left side of Fig 10 shows that. The right side shows how that is affected by data gaps (I’m not sure why). I think Fig 11 reflects that.
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Thanks Nick .
Whatever way you dice it the effect is clearly shown in figure 7 and the figures stand. A notable part of the supposed acceleration comes from a GAIA adjustment that should not cause any acceleration. If this is due to changes in data length, the whole idea of including that early part and fitting a quadratic becomes very dubious.
After this mysterious “acceleration” concentrated around 1880, there is a very constant rise and NO acceleration. What their detailed work shows is that this is an artefact,
0.001 mm/yr^2 +/- ??? means NO acceleration.
There is a good agreement between the rate of sea level rise (3.2 ± 0.4 mm·yr− 1) calculated from satellite altimetry and the rate of 3.1 ± 0.6 mm·yr− 1 from tide gauge based reconstruction for the overlapping time period (1993–2009). The new reconstruction suggests a linear trend of 1.9 ± 0.3 mm·yr− 1 during the 20th century, with 1.8 ± 0.5 mm·yr− 1 since 1970.
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Maybe I need more coffee. I’ve read this about six times and it seems to say 3.3 ~= 3.2 ~= 1.9 ~= 1.8 where “~=” denotes “approximately equal”. Reads sort of like a computer mistranslation of some oriental language into English. Usually there is some clue that tells me what I’m misreading. but this one utterly defeats me. Can anyone help out?
Greg,
After this mysterious “acceleration” concentrated around 1880, there is a very constant rise and NO acceleration.
No, it isn’t constant rise. That’s best shown in their Fig 15. There are periods of positive and negative acceleration that balance.
http://www.marinelink.com/news/million-rising-level368874.aspx
“There is a huge inertia in the climate system, so even if we stop the warming of our planet now – if we stop emitting greenhouse gases into the atmosphere today – the global sea level will continue to rise for the next few hundred years,” Dr. Jevrejeva explained. “We are facing a colossal challenge – to deal with carbon emissions as soon as possible.”
Jevrejava seems to have some fairly strong warmist tendencies in her comments however she seems very capable of divorcing this from her scientific work. We all have opinions, her ability to remain objective in her work is a refreshing change in this field.
Don K: Usually there is some clue that tells me what I’m misreading. but this one utterly defeats me. Can anyone help out?
Pay more attention to what you are reading: note the periods to which these different figures apply.
Nick Stokes says:
Greg,
After this mysterious “acceleration” concentrated around 1880, there is a very constant rise and NO acceleration.
No, it isn’t constant rise. That’s best shown in their Fig 15. There are periods of positive and negative acceleration that balance.
Sure, Nick I was not suggesting it was a ruler straight line but it’s pretty linear over the century not quadratic. The figures I have quoted from the paper substantiate that: since 1880:
0.001 mm/yr^2 +/- ??? means NO acceleration.
Marcos says:
somewhere on the Colorado University Sea Level site I saw where it says that their numbers are not meant to be used to gauge the relation of sea level to land. I cant seem to find it now…
Indeed it is a ‘climate index’ that is misnamed Global mean sea level. It has less and less to do with the wet type of sea level with each passing year. Except, they don’t put that on the front page, You have to dig down in links about description of data etc.
It’s also “barmometer adjusted”. Just how air pressure is supposed to affect the global mean is not explained. Enquiries are ignored.
Is that the American Standard inches? Or the new alarmist inches? Hard to keep up with changing metrics by alarmists.
Greg Goodman says:
May 21, 2014 at 3:24 am
Pay more attention to what you are reading: note the periods to which these different figures apply.
==========
Actually, Greg I did look at the timespans. But …
“Quoting the five researchers, “the new reconstruction suggests a linear trend of 1.9 ± 0.3 mm/yr [7.5 inches per century] during the 20th century” and “1.8 ± 0.5 mm/yr [7 inches per century] for the period 1970-2008.” That seems not terribly consistent with “(3.2 ± 0.4 mm·yr− 1) calculated from satellite altimetry and the rate of 3.1 ± 0.6 mm·yr− 1 from tide gauge based reconstruction for the overlapping time period (1993–2009)” … unless sea level rise was very low from 1970 to 1993 and very high thereafter.
I suspect that the problem is that I’m comparing stuff that isn’t readily comparable. But I’m not quite sure how. I’ll come back and look at it again in a few days. Maybe it’ll come together then.
The link to the full paper above is not working, but here is another link to the full paper.
http://kaares.ulapland.fi/home/hkunta/jmoore/pdfs/Jevrejevaetal2013GPChange.pdf
I do not think any of the acceleration rates quoted here are valid. The sea level rate since 1870 or, since 1930 when global coverage became large enough, is a roughly a “linear trend”. Jevrejeva did a simple quadratic equation going back to 1807 which should not be thought of as robust (more likely it was just trying to keep in the good books of the climate science bullies).
It looks more likely that sea level from the gauges have been rising at 1.8 mm/yr (with a few times when it goes off-trend like in the 1960s, higher, and especially the early 1990s, lower.
The satellite trend starts in 1993. This was a very low point in sea level most likely due to the cooling from the Pinatubo volcano.
Jevrejeva’s most recent tide gauge data from 2003 to 2009 shows sea level is actually falling
The data will likely become available soon. The comments above the Peltier’s ICE-5G glacial isostatic rebound model which has sea depth decreasing at 0.3 mms/year takes a slight beating in the paper. GPS is producing quite different results in different places (although the global rate is probably close).
figure 8 shows what the “acceleration” really looks like:
http://climategrog.wordpress.com/?attachment_id=944
Fitting a quadratic to estimate an overall “acceleration” seems highly questionable. There is clearly a very punctual change in direction around 1860.
There is a roughly semi-sinusoidal variation with a base period of about 120y on top of an essentially linear rise since 1880.
The periodic form looks about 30 years out of phase with changes in SST. This would suggest an integration process. Perhaps this reflects diffusion of SST into OHC with a slow time constant.
It would be interesting to get the resulting time series in numbers as well as just the pics.
Bill Innis: more likely it was just trying to keep in the good books of the climate science bullies.
Yes, the quadratic fit is highly questionable and it looks a lot like orthodoxy compliance that this got into the abstract, rather than the real result of the study : 1.9mm/y for 20th c. with NO acceleration.
As someone commented recently, it’s a bit like reading Soviet era PRAVDA. You get the govt. line and then try to read between the lines to find out what is really happening.
I give Jevrejeva credit for very fully documenting this work. At least we have enough detail to read between the lines ( and ignore the abstract ).
Greg Goodman says:
May 21, 2014 at 4:10 am
It’s also “barmometer adjusted”. Just how air pressure is supposed to affect the global mean is not explained. Enquiries are ignored.
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I’d guess that it is the individual measurements that are adjusted for barometric pressure, not the final number. Atmospheric pressure does significantly affect sea level (it’s higher when the pressure is low) I don’t recall exactly how much, but in the range of 30cm for very low pressure. Not that an additional foot of sea level rise is likely to concern observers all that much at the heart of a monster storm. Anyway, one of the things on my todo list is to look into where the pressures used to adjust sea level data come from. AFAIK, there are substantial areas of the planet with few or no barometers and I think that it is not currently possible to measure surface atmospheric pressure from a satellite.
“I’d guess that it is the individual measurements that are adjusted for barometric pressure, not the final number. ”
Indeed, which is why it makes no sense producing ib-adj global data . There used to be the option of no-ib but that is no longer available (at least to the public) and requests for a link to it do not even the get courtesy of a reply.
C.U Bolder is (data) massage parlour now. Forget the satellite altimetry.
That’s why I’m very glad to see an up-date from Jevrejeva. Much more informative.
I’ve read the paper. They don’t find there is no acceleration; as said in the abstract
” We calculate an acceleration of 0.02 ± 0.01 mm·yr- 2 in global sea level (1807–2009).”
.02=2/100 or 20/1000 1/1000 of a mm,=1 micron or 1/1000000 meters 20 microns of acceleration per annum is not significant when we pump enough water for irrigation to account for 100 times that.
Gee, WordPress doesn’t like extra spaces. try this:
.02=2/100 or 20/1000
1/1000 of a mm=1 micron or 1/1000000 meters
20 microns of acceleration per annum is not significant when we pump enough water for irrigation to account for 100 times that.
Since they said for the longer period :
“5–95% confidence interval of 0.01–0.04 mm·yr^2 for the 0.02 mm·yr^2 acceleration.”
0.01 mm·yr^2 is probably indistinguishable from zero. (They forgot to give any error estimation for that).
It also fits across 2 1/2 of the circa 60y bumps, that will induce a small “acceleration”. http://climategrog.wordpress.com/?attachment_id=944
What is significant about this paper is that GHG forcing that is supposedly causing exponential, run-away warming, collapse of the polar ice sheets, retreat of the worlds glaciers, etc since around 1960 is not visible at all in the sea level record.
All we see is the same natural variability that there was before 1960.
Don K, Greg Goodman
Section “2.1 Data” contains the sentence “No inverted barometer correction was applied.”
If you wanted to get pressure data, you could probably use a reanalysis product:
http://www.esrl.noaa.gov/psd/data/gridded/data.20thC_ReanV2.monolevel.mm.html
If we use 1650 as the mid coldest part of the LIA, then would this not indicate an approximate lag in cooling vs drop in sea level (1850), of 200 years? GK
If sea level is increasing at 1.8 millimetres per year and the rate is accelerating at 0.02 millimetres/year/year …
… after 100 years, you get 11 inches of sea level rise.
So, an acceleration rate this high would be an important number.
Its just that it is probably just an artifact of the methodology used. One would need the actual annual sea level numbers produced by Jevrejeva 2014 to see if it is valid number.
One can compare how sea level is changing each year in 3 recent reconstructions to see if it is valid (Jevrejeva 2008, Church and White 2011, Ray and Douglas 2011).
Back to 1900, we could argue there is an acceleration rate ranging from 0.006 mms/year/year to 0.021 mms/year/year. But, you know, I still would say the values are not different than Zero. A constant 1.8 mms/year.
http://s2.postimg.org/guvjasjq1/1900_2009_Sea_Level_Acceleration_Tide_Gauges.png
If we just use the same reconstructions starting in 1960, now the acceleration rates bump up to 0.04 mms/year/year to 0.059 mms/year. Again, hard to tell if this is valid.
http://s28.postimg.org/6xdaibgxp/1960_2009_Sea_Level_Acceleration_Tide_Gauges.png
It is an artefact as I suggested , due to the incomplete cycle.
Here I have run a similar quad fit on a linear model with semi-sinusoidal bumps, like those of the Jevrejeva sea level record.
http://climategrog.wordpress.com/?attachment_id=945
I find it fits an “acceleration” about twice that found in the paper, as well as somewhat underestimating the linear component.
This probably means that their insignificantly positive “acceleration” could in fact be an insignificant deceleration 😉 and their 1.9mm/yr 20th c. trend may be 2.0 mm/yr .
It would require a actual data to do this accurately but I think I’m sufficiently close to establish the principal. Fitting to an incomplete bump like that would produce similar results.
Since we don’t yet know how that last bump will shape up, their method is not wrong. but some appreciation of the fact they are fitting to data with an obvious cycle component and how the fitting period will affect this is important before anyone get too excited about 0.001 mm/yr^2 “acceleration” in sea levels.
Jevrejeva 2014:
” Fig. 15 reveals that during the past 203 years there are
several time periods with positive and negative sea level accelerations,
suggesting that a wide spectrum (from 10 to 100 years) of variability
influences estimates of sea level acceleration, and this leads to uncer-
tainty in the quadratic fitting of the GSL depending on the time period
selected. ”
That little word of caution will of course be totally ignored by the media who will jump on the “catastrophic acceleration” of global sea levels “on the heels” the imminent “collapse” the entire Antarctic ice shelf, due in 200 years.
Bottom line:
The degree of acceleration they found probably masks a very slight deceleration over 20th if this periodic variation is removed. Data please 😉
Bill Innis: Jevrejeva’s most recent tide gauge data from 2003 to 2009 shows sea level is actually falling
The data will likely become available soon.
Do you have a source for that data ? I was not aware that any of the Jevrejeva data was publicly available, even from the 2006 paper.
The problem with “improving” the database by including a large number of long lived stations is the inherent bias toward sites that will be subject to long term subsidence. These sites weren’t originally selected because they were good locations for the monitoring of sea level change. They were selected because they were favorable for the construction of protected port facilities. As a result, they are more likely to have been located in a sheltered bay, inlet, or estuary underlain by relatively recent geologic deposits subject to natural and/or man-induced subsidence. As opposed to relatively more geologically stable sites on exposed rocky coastlines.
I suppose. that is a convenient coincidence for these investigators.
Greg Goodman says:
May 21, 2014 at 8:41 am
I ran WebPlotDigitizer on Figure 3 and got the following results
https://sites.google.com/site/climateadj/jev-2014-data
It doesn’t capture the data exactly (the s.d. is probably lower), but it should be close.
Also the data for the 2006 data is available from climate explorer:
http://climexp.knmi.nl/getindices.cgi?WMO=PSMSLData/gsl&STATION=global_coastal_sea_level&TYPE=i&id=someone@somewhere