May 13 2008
Global Sea Levels: Another Hockey Stick
Anthropogenic global warming is expected to bring many changes to the world. According to Wikipedia, “[m]ost of the consequences of global warming would result from one of three physical changes: sea level rise, higher local temperatures, and changes in rainfall patterns.” The most obvious consequence of the three is higher surface temperatures. And this is the consequence that the media focus on the most.
Precipitation changes can also be fairly easily conceptualized. If the addition of greenhouse gases changes the heat distribution of the planet, it is likely that regional weather patterns will change as well. Changes in both temperature and precipitation are easy to understand for everyone. However, the third consequence is more difficult, especially those of us who don’t live near the coast.
Historic Sea Levels
Sea levels have risen since the end of the last ice age, approximately 20 thousand years ago. Most of that rise has been a consequence of the natural warming that has occurred. However, sea levels have been relatively constant over the last 7000 years. A new paper in GRL looks at sea level rise from gauge data, and provides a reconstruction from 1700 through the present.
Satellite records of sea levels show that they have risen about 3 mm per year since 1993. 3 millimeters (3/1000 of a meter) doesn’t sound like a lot. In fact, it sounds like a very small increase. However, as an example consider that in the next 100 years the sea level rise continues at its present rate, and there are no changes in acceleration. In 2108 sea levels will have risen by 0.3 meters, or only about 1 foot.
Recent Reconstruction
Jevrejeva et al. (2008) extend the sea level record backwards from 1850 using three of the longest tide gauge records available: Amsterdam, Liverpool, and Stockholm. Using only 3 measurements to estimate the global sea level is obviously not as good as using 100 gauge measurements. They compensate for this by increasing the error values associated with data points prior to 1850, as can be seen in Figure 1 (borrowed from original).
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According the Jevrejeva, sea levels were relatively constant before 1800. After 1800, there has been a dramatic increase. The rate of change of sea levels has also been increasing. They calculate that the recent sea level acceleration has been about 0.01 mm/yr/yr.
They conclude:
However, oceanic thermal inertia and rising Greenland melt rates imply that even if projected temperatures rise more slowly than the IPCC scenarios suggest, sea level will very likely rise faster than the IPCC projections [Meehl et al., 2007].
References:
Jevrejeva, S., J. C. Moore, A. Grinsted, and P. L. Woodworth (2008), Recent global sea level acceleration started over 200 years ago?, Geophys. Res. Lett., 35, L08715, doi:10.1029/2008GL033611.
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11 Responses to “Global Sea Levels: Another Hockey Stick”
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That makes sense because the leftward side of the graph depicts the Little Ice Age. The current warming is an adjustment from that period.
Little Ice Age, Little Ice Age, Little Ice Age, you can’t suppress the knowledge of the past. Say it over and over like bloody mary until you free your mind from this nonsense.
Actually, if you look at the data, the level has dropped in much of 2007 and is barely above what it was in mid 2006.
http://www.cmar.csiro.au/sealevel/sl_hist_last_15.html
I’m not sure I’d call the last 2000 years a hockey-stick….
http://www.cmar.csiro.au/sealevel/sl_hist_few_hundred.html
Did Jesus Christ cause the seas to rise 2000 years ago?! or was that Moses?
TheWrathofGod:
Scroll all the way down on that page you linked to. That is their reconstruction from gauge data. It only goes back to 1870. This paper attempts to reconstruct it back to 1700 using gauge data, and is shown in the figure in the original post. The “shape” is similar as the temperature hockey stick during that time frame, hence the title of the post.
This article:
http://www.worldclimatereport.com/index.php/2008/05/06/slower-sea-level-rise/#more-323
references 2 recent papers that give 1-1.5 mm/yr rise. This is a lot closer to what a gentleman, reviled by warmers, by the name of Nils-Axel Moerner claims.
Here is one:
http://drs.nio.org/drs/bitstream/2264/646/3/Global_Planet_Change_57_301.pdf
the other one I could only find behind toll gates.
IPCC AR4 SPM says:
Unnikrishnan and Shankar found a regional average of 1.29 mm per year [1.06 to 1.75 mm per yr] and state:
Berge-Nguyen et al. state in their abstract:
Both of the studies basically state that they are in agreement with the IPCC.
Yes, 3 data points is not as good as 100, but three in the same location with at least one being one of the fastest sinking land masses in the world, and another with amongst the highest tides, and another with melting snow because of local recent sea current change, all in the same area, really isn’t saying much about any global trend.
Atmoz:
Please correct me if I am wrong. Are the data from altimeter-derived measurements of global mean sea level rise being used as a “proxy” for heat content in the upper ocean?
If so, then follow-up questions are: With recently reported “cooling” or at the least “no warming” in the upper ocean, is it more likely that the heat has been transported to the deep ocean (more than 3000m) as has been suggested from time to time? Is reliance upon the JASON satellite system in support of heat in the upper ocean misplaced?
[Reply: I don't know the answer to any of those questions. Sorry. ]
Atmoz,
Quoted from IPCC TAR:
“Global average sea level rose at an average rate of 1.8 [1.3 to 2.3] mm per year over 1961 to 2003. The rate was faster over 1993 to 2003: about 3.1 [2.4 to 3.8] mm per year.”
The problem being that from 1993-2003, neither study supports the higher 3mm rate which is probably why they have a substantially lower average than 1.8 (1.29 & 1.5). Consistent but lower. Basically they match the level increase pre 1993.
The adjusted satellite record showing 3.4 mm/yr.
http://sealevel.colorado.edu/
then comes into question. If thermal expansion was a significant contribution to sea level rise while trop and sea were warming (pre-2003), yet Argo data now tells us that there was no warming, and therefor no thermal expansion since 2003, where did all the water come from to make up the difference?? Since 2003 there would not appear to be a large enough warming to add a significant increase to melt over pre 2003.
Brian:
Here is an interesting interactive that allows you to show ocean temps at levels from surface down to 5500m. It shows annual, seasonal, and monthly temps.
http://www.nodc.noaa.gov/cgi-bin/OC5/WOA05F/woa05f.pl
Sadly it is only for 2005.
KuhnKat:
Thank you for the lead to the 2005 World Ocean Atlas; I’ll do some “navigating”.
To answer your question, “where did all the water come from”, I suggest the following.
The ARGO system has a depth domain of 2,000 m or 48% of ocean volume (see:
http://wo.jcommops.org/cgibin/WebObjects/Argo.woa/1/wo/sCZrymVtJHXMpc6XImH1mM/6.0.40.4.8.4.1.0.1.3.3
whereas the oceans have an average depth of 3,800 m.
Since “no significant warming or cooling is observed in upper-ocean heat content between 2004 and 2006” as reported by Willis [Lyman] et al. in **In Situ Data Biases and Recent Ocean Heat Content Variability (February 29, 2008)**, heat transport to and thermal expansion of the ocean deep could be the reason for continuing satellite altimeter reports of sea level rise. Such transport was considered by Lyman [Willis] et al. in “Recent Cooling of the Upper Ocean” (October, 2006): “Assuming that the 3.2 (± 1.1) 1022 J was not transported to the deep ocean, previous work suggests that the scale of the heat loss is too large to be stored in any single component of the Earth’s climate system [Levitus et al., 2005]. A likely source of the cooling is a small net imbalance in the 340 W/m2 of radiation that the Earth exchanges with space.”
Hansen et al. in **Dangerous human-made interference with climate: a GISS modelE Study (published May, 2007)** also considered heat transport to the ocean deep: “Note the slow decline of the planetary energy imbalance after 2100 (Fig. 3b), which reflects the shape of the surface temperature response to a climate forcing. Figure 4d in Efficacy (2005) shows that 50% of the equilibrium response is achieved within 25 years, but only 75% after 150 years, and the final 25% requires several centuries. This behavior of the coupled model occurs because the deep ocean continues to take up heat for centuries. Verification of this behavior in the real world requires data on deep ocean temperature change. In the model, heat storage associated with this long tail of the response curve occurs mainly in the Southern Ocean. Measured ocean heat storage in the past decade (Willis et al., 2004; Lyman [Willis] et al., 2006) presents limited evidence of this phenomenon, but the record is too short and the measurements too shallow for full confirmation. Ongoing simulations with modelE coupled to the current version of the Bleck (2002) ocean model show less deep mixing of heat anomalies.”
Nevertheless, Johnson et al. in **Recent bottom water warming in the Pacific Ocean**, J. of Climate. Volume 20. November 2007, reported deep ocean heat as follows:
“Between 3000 m (or 4000 m in the case of P06) and the bottom these estimates of heat flux range from 0.01 W m–2 along 47°N (P01) to 0.06 W m–2 along 170°W south of the equator (P15S). These values are between 5 and 30% of the heating trend of 0.2 W m–2 estimated for the 0–3000 m world ocean heat content change between 1955 and 1998 (Levitus et al. 2005) and between 2 and 10% of the heating trend of 0.6 W m–2 (per unit area of the Earth’s surface) estimated for the 0–750 m world ocean heat content change between 1993 and 2003 (Willis et al. 2004). Thus, abyssal Pacific Ocean heat content variations may contribute a small but significant fraction to the Earth’s heat budget…… The data from these repeat sections suggest that abyssal variations may contribute significantly to global heat, and hence sea-level, budgets. To close ocean heat, sea level, and likely freshwater budgets on interannual timescales, the ocean below 2000 m must be much better sampled in space and time than it has been, or is likely to be, relying on repeat hydrography alone.“
Roger Pielke Sr. took note and the significance of Johnson et al. by writing, “This is an important paper with respect to diagnosing the radiative imbalance of the climate system (i.e. global warming and cooling). Moreover, if heat is being stored in deep depths, this would help explain why sea level continues to rise yet the upper ocean has not been warming in recent year[s]. It also means that the feedback of this heat into the atmosphere is delayed, or even lost for a very long.” (see http://climatesci.org/2008/02/07/deep-ocean-heat-accumulation-a-diagnosis-of-its-magnitude/).
Despite the foregoing and the fact that Willis [Lyman] et al. (February 29, 2008) acknowledge, “It should be noted that SSH is only a proxy for OHCA, as **it contains deep water**, fresh water, and mass signals that are not in upper OHCA.” (emphasis added), they write “Numerous studies (White and Tai 1995; Gilson et al. 1998; Willis et al. 2003; 2004) have demonstrated the strong relationship between altimetric height anomaly and OHCA (or thermosteric sea level anomaly) in various regions and over a wide variety of temporal and spatial scales. Furthermore, wavenumber and frequency spectra of altimetric height are almost identical to those of upper ocean temperature variability (Zang and Wunsch 2001, their figure 6). For this reason, and because satellite altimeters provide near-global coverage during the period in question, altimeter data can be used as a proxy for testing the effects of in situ data sampling on estimates of globally averaged OHCA.”
So, my question remains. Is reliance upon the JASON satellite system in support of heat in the upper ocean misplaced when there may be a case for thermal expansion of the ocean deep?
I have’nt read the paper, but I grew up in the Liverpool area and it is known for having one of the highest tidal ranges in the UK, if not wider. I seem to recall a range of 30 feet or so and the Mersey Ferry landing quays have to be on floating pontoons to accommodate the changing levels.
So I would find it difficult to see how a 0.01mm accelerating sea level rise could be discerned in this respect.