Tisdale on 2011 sea level changes

1ST Quarter 2011 Sea Level Anomaly Update And An Initial Look At The Impacts Of ENSO On Global Sea Level

Guest post by Bob Tisdale

It’s been more than two years since my last Sea Level anomaly update using the data from the University of Colorado Sea Level Research Group . I visit their website regularly, but each update seems to be an extension of the monotonous 3.22 mm per year linear trend with another wiggle or correction that keeps it at or near that trend. That aside, since it has been two years and since there have been significant El Niño and La Niña events since then, I felt it would be good to update the Sea Level anomaly graphs at my blog.

There’s another topic that prompted this post: The University of Colorado’s recently updated webpage included a discussion of how sea levels should start to rise again in response to the ebbing of La Niña conditions in the tropic Pacific, 2011_rel2: GMSL and Multivariate ENSO IndexBut the graph they included did not appear to go along with the description, so I’ve also discussed detrended sea level and the Multivariate ENSO Index (MEI) in this post.

Let’s get the Sea Level update portion out of the way first.

SEA LEVEL UPDATE – MONTHLY DATA

Figure 1 illustrates the global Sea Level anomalies on a monthly basis, from January 1993 to March 2011. I started with the Global Sea Level (2001 rel2) with the seasonal signal included. The data also includes Inverse Barometer and Glacial Isostatic Adjustments. I converted it to monthly data, then determined anomalies from the monthly averages of the base period, which was the entire term of the data, 1993 to 2010. And as discussed earlier and illustrated in Figure 1, the global sea level anomaly data seems simply to follow the linear trend with some minor multiyear divergences.

Figure 1

I followed the same routine for the Atlantic, Indian, and PacificOcean data, Figures 2, 3, and 4, respectively. The Atlantic data appeared to have flattened from 2005 through 2008, but it swung back up in 2009. The Indian Ocean data is noisy, being impacted by ENSO and the phenomenon known as the Indian Ocean dipole, and it seems to be continuing its rise without any multiyear decreases in trend. The Pacific Ocean Sea Level data, however, appears to have flattened since 2006, though it does make a rise and fall in response to the 2009/10 El Niño and the 2010/11 La Niña. How long will it continue to rise at the reduced rate?

Figure 2

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Figure 3

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Figure 4

And, for those interested, Figure 5 is a spaghetti graph that compares the Global Sea Level anomalies and the data for the three major basins. All have been smoothed with 12-month running-average filters to reduce the noise.

Figure 5

SEA LEVEL UPDATE – ANNUAL DATA

Some readers prefer annual data. I’ve presented the Global, Atlantic Ocean, Indian Ocean, and Pacific Ocean data on an annual basis in Figures 6 though 9.

Figure 6

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Figure 7

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Figure 8

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Figure 9

NOTE ABOUT KNMI CLIMATE EXPLORER

KNMI has added the University of Colorado Global Sea Level anomaly data to its Climate Explorer on the Monthly climate indices webpage. They also have the ocean basin and sea subsets that are presently available through the University of Colorado’s Regional Sea Levelwebpage. The updating at the Climate Explorer can occasionally lag the University of Colorado, so the data at KNMI as of this writing is still 2011_rel1. But there is a wonderful benefit to using the KNMI Explorer for that sea level data: KNMI presents it on a monthly basis.

DETRENDED GLOBAL MEAN SEA LEVEL VERSUS ENSO INDEX

Before we begin, I want to clarify two things. I am not questioning the University of Colorado’s prediction that Sea Levels will rise again shortly in response to the ebbing La Niña event in the following discussion. And I am also not implying that my findings show an error with the Sea Level data. This discussion presents a multiyear divergence between an ENSO index and the detrended Global Sea Level anomalies that I find interesting.

The University of Colorado Sea Level Research Group has recently added a discussion of the impact of ENSO on Sea Level. Refer to their 2011_rel2: GMSL and Multivariate ENSO Index webpage. To explain the recent decline in Sea Level, they provide the following illustration, Figure 10, and discussion:

The Multivariate ENSO Index (MEI) is the unrotated, first principal component of six observables measured over the tropical Pacific (see NOAA ESRL MEI, Wolter & Timlin, 1993,1998).  To compare the global mean sea level to the MEI time series, we removed the mean, linear trend, and seasonal signals from the 60-day smoothed global mean sea level estimates and normalized each time series by its standard deviation. The normalized values plotted above show a strong correlation between the global mean sea level and the MEI, with the global mean sea level often lagging changes in the MEI. Since the MEI has recently sharply increased (coming out of a strong La Niña), we expect the global mean sea level estimates to also reverse their recent downward trend and begin to increase as the La Niña effects wane.

Figure 10

Detrended Global Sea Level Anomalies in Figure 10 mimic the MEI data, but I don’t know that I’d call it a strong correlation. In fact, the correlation coefficient for those two datasets is only 0.44. So let’s detrend the monthly Global Sea Level anomalies, standardize the data, and compare them to the MEI data, Figure 11. (Note that the MEI is a standardized dataset, but the University of Colorado standardized it again for their graph, so I did too.) My Figure 11 is a reasonable reproduction of the University of Colorado graph, Figure 10. They presented 6-week averages of the sea level data, and I’ve presented it on a monthly basis.

Figure 11

Now let’s smooth both datasets with a 12-month running average filter, Figure 12. The detrended and standardized Global Sea Level anomalies definitely do not always follow the ENSO index. And it doesn’t appear that any other method of scaling the two datasets will provide better results, but let’s try two more.

Figure 12

For Figure 13, I did not standardize the detrended Global Sea Level anomalies, but I scaled the MEI data based on a linear regression analysis. That doesn’t help. All that seems to do is emphasize the differences between the two datasets, especially the two Bactrian camel-like humps in the detrended Sea Level data compared to the three moderate El Niño events between 2002 and 2007.

Figure 13

Last, for Figure 14, let’s assume that the “Super” 1997/98 El Niño was the only ENSO event during the period that was strong enough to overcome the year-to-year noise in the Sea Level data, and that the evolution phase of that El Niño event should be “cleanest” since the decay phase in the sea level data includes the aftereffects of the El Niño. Then we can scale the MEI data and shift it down so that the leading edges of the two datasets align during the evolution of the 1997/98 El Niño. Now, note how the Detrended Global Sea Level anomalies diverge from the MEI data during the decay phase of the 1997/98 El Niño. Then they rise, remaining well above the ENSO index data through 2005, when they start to drop until they realign again during the decay phase of the 2009/10 El Niño. Interesting, isn’t it? It’s something that needs to be investigated further.

Figure 14

Detrending the Atlantic and Indian Ocean datasets and comparing them to the MEI data that has been scaled to the response to the 1997/98 El Niño does not seem to shed any light. Refer to Figure 15 for the Atlantic Ocean data and Figure 16 for the Indian Ocean data. But the detrended Pacific Ocean data, Figure 17, has a response that’s similar to Global data, so it might hold the key.

Figure 15

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Figure 16

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Figure 17

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A NOTE ABOUT THE ENSO INDEX

Someone is bound to ask why the detrended Pacific sea level data precedes the MEI data. Let’s replace the MEI data with scaled NINO3.4 Sea Level (not Sea Surface Temperature) Anomalies, Figure 18. The detrended Pacific Sea Level anomalies do not lead the NINO3.4 Sea Level Anomalies. Keep in mind that I used the MEI data because the University of Colorado used it, not because it was the right ENSO index to use with Sea Level data.

Figure 18

As illustrated in Figure 19, the NINO3.4 region Sea Level anomalies precede the NINO3.4 SST anomalies and the Multivariate ENSO Index data. And they should. The NINO3.4 Sea Level data captures the Kelvin waves and the subsurface temperature anomalies traveling from west to east across the equatorial Pacific, which lead the response of the NINO3.4 Sea Surface Temperatures and many of the additional variables used in the Multivariate ENSO Index.

Figure 19

CLOSING

The answer to what causes the multiyear divergence of the detrended global sea level anomalies from the ENSO index might rest in the process of ENSO and the significant redistribution of warm waters from the tropical Pacific following the 1997/98 El Niño event. Then again, mass from glacial runoff is also a major contributor to Sea Level. Did it temporarily increase for a few years after the 1997/98 El Niño? For now, I’ll treat the decade-long divergence as a curiosity, but I’ll keep looking for an explanation.

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68 thoughts on “Tisdale on 2011 sea level changes

  1. Bob, can you comment about the recent paper by Church claiming that sea level rise is accelerating? http://www.springerlink.com/content/h2575k28311g5146/fulltext.pdf

    Another question. I look at tidal guage data such as this, http://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.shtml?stnid=680-140

    and the rate appears to be 1.74 (as per Holgate), so where is the 3mm/yr coming from? Why the discrepency? Seems some are questioning the accuracy of satelite data. Maybe an article about this to clear up what the true rate of sea level is and if it is or is not accelerating.

  2. Jr wrote: “and the rate appears to be 1.74 (as per Holgate), so where is the 3mm/yr coming from? Why the discrepency?”

    LexingtonGreen comment:
    And then there is that upward adjustment the Colorado folks put in to factor for volume increases or some such thing that I have now forgotten how to factor into whatever chart I am looking at.

    Anyhow, not sure were to post it but I thought this was funny today from the campaign trail:

    Huntsman tweeted: “To be clear. I believe in evolution and trust scientists on global warming. Call me crazy.”

    OK, Huntsman, you are crazy to believe the BS on the global warming front.

  3. The mass being lost from Greenland, Antarctica, and glacial melt along with thermal expansion easily explains the divergence that Bob finds only as “curiosity”. Of course, these things are all related to a longer-term warming of the planet beyond any short-term ENSO effects, but I suppose that’s not what skeptics like to hear.

  4. Bob
    Another extremely useful article updating us all as to what is going on.
    I always enjoy reading the thoroughness of your evaluations.
    Thank you

  5. jrwakefield: I haven’t read Church and White (2011). Hopefully, someone else will answer your question. With respect to Sea Level graph you linked for Sydney, Australia, is there a link on that page to the data in the graph?

  6. So, essentially, all the “missing” water is on vacation in the Indian Ocean. Probably quite nice this time of year though.

  7. R. Gates says: “The mass being lost from Greenland, Antarctica, and glacial melt along with thermal expansion easily explains the divergence that Bob finds only as ‘curiosity’.”

    Apparently, you didn’t notice that the divergence was temporary. The detrended Global Sea Level data diverges from the ENSO index after the 1997/98 El Nino but returns during the 2009/10 El Nino.

  8. “jrwakefield says:
    August 18, 2011 at 1:35 pm

    and the rate appears to be 1.74 (as per Holgate), so where is the 3mm/yr coming from? Why the discrepency? Seems some are questioning the accuracy of satelite data. Maybe an article about this to clear up what the true rate of sea level is and if it is or is not accelerating.”
    ======

    I’ll be interested to see what Bob Tisdale and others say. The 3.22 is mm/yr is from overlapping (in time) measurements from three different satellites with similar characteristics that cover about 20 years. Numbers around 1.8 are from tidal gauge data that goes back a little over a century. About 8 years of data from a different satellite (Envisat) are close to the tidal gauge data … or maybe less depending on what adjustments one chooses to use. I believe there were/are altimeters on three other satellites GFO, GOCE, and ERS2. I haven’t been able to track down values yet. Tracking down the data has proved not to be as easy as one might think.

    My take on all this FWIW (probably not much) No one actually knows the “true rate of sea level rise” much less its first derivative — rate of sea level rise. We do have reason to believe that current sea level rise is low — 20 or 30 cm a century. AR4 manages to conjure up future rates about twice that, but the material there looks to me to be typical “climate-crap” (i.e. an op-ed disguised as a scientific analysis). Not that they are necessarily wrong, but I think serious skeptics with equivalent time and funding could probably come up with an equally plausible argument that sea level rise is being overestimated.

  9. Tisdale on 2011 sea level changes
    Posted on August 18, 2011 by Anthony Watts
    1ST Quarter 2011 Sea Level Anomaly Update And An Initial Look At The Impacts Of ENSO On Global Sea Level
    Guest post by Bob Tisdale

    “It’s been more than two years since my last Sea Level anomaly update using the data from the University of Colorado Sea Level Research Group . I visit their website regularly, but each update seems to be an extension of the monotonous 3.22 mm per year linear trend with another wiggle or correction that keeps it at or near that trend.”

    Taken a relevant depth of 1000 m for each delta of 0.1 ° Cel. (at T = 19° Cel.) the global height of the sea level must rise by ~23 mm because of the volume change of the water. That’s about 230 mm per 1.0 ° Cel. A linear fit of the hadcrut3 data from 1993 to 2010 reads 0.0167° per year. This corresponds with a delta of (0.0167° * 230 mm) 3.84 mm per year. This suggests that the sea level rise is a result of the global warming for that time intervall.

    But one can see on your Fig. 4 and Fig. 5 for the last 10 years your linear trend is no longer valid, and this is in agreement with the hadcrut3 data for this time interval.

    V.

  10. R. Gates says:
    August 18, 2011 at 2:25 pm

    The mass being lost from Greenland, Antarctica, and glacial melt along with thermal expansion easily explains the divergence that Bob finds only as “curiosity”. Of course, these things are all related to a longer-term warming of the planet beyond any short-term ENSO effects, but I suppose that’s not what skeptics like to hear.

    ======

    Let’s see what AR4 has to say “Near-global ocean temperature data sets made available in recent years allow a direct calculation of thermal expansion. It is believed that on average, over the period from 1961 to 2003, thermal expansion contributed about one-quarter of the observed sea level rise, while melting of land ice accounted for less than half. Thus, the full magnitude of the observed sea level rise during that period was not satisfactorily explained by those data sets, as reported in the IPCC Third Assessment Report.” http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-5-1.html

    Please feel free to acknowledge that you find pontificating on subjects that you don’t actually know much about to be an entertaining hobby. (I can’t think why it entertains you, but it takes all sorts I suppose).

  11. Don K, thanks. Seems rather strange that the tidal guages show half what the satelites show, that some how the very year the satelites started to take measurements sea level also doubled, Don’t like co-incidences. There must be something fundementally wrong with the satelite data. I just cannot see the in situ tidal data, which has been the same for the past 100 years, magically wrong the day satelites started to measure.

  12. Nature does not do straight lines, it operates on curves.
    If you cannot see the curve before or after the linear slope of sea level, then you don’t have sufficient data to know where it’s been, how long it has been doing this, or where it’s going next.
    Take all those graphs and throw the sloped ruler lines out.
    Now what do we have?
    The Pacific and the Atlantic diverged and went in opposite directions.
    Can anyone say for certain that the two will once again merge on base course, or whether the Atlantic will soon follow the lead of the Big Pacific?

  13. Don K says:
    August 18, 2011 at 3:55 pm
    R. Gates says:
    August 18, 2011 at 2:25 pm

    The mass being lost from Greenland, Antarctica, and glacial melt along with thermal expansion easily explains the divergence that Bob finds only as “curiosity”. Of course, these things are all related to a longer-term warming of the planet beyond any short-term ENSO effects, but I suppose that’s not what skeptics like to hear.

    ======

    Let’s see what AR4 has to say “Near-global ocean temperature data sets made available in recent years allow a direct calculation of thermal expansion. It is believed that on average, over the period from 1961 to 2003, thermal expansion contributed about one-quarter of the observed sea level rise, while melting of land ice accounted for less than half. Thus, the full magnitude of the observed sea level rise during that period was not satisfactorily explained by those data sets, as reported in the IPCC Third Assessment Report.” http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-5-1.html

    _____
    It is likely that the IPCC fairly well underestimated the contribution from the melting ice in Antarctica and Greenland in the last report (since it was not considered significant) and that will be one of the big changes in the next report. This article sums the situation up pretty well I would say:

    http://www.nature.com/climate/2010/1004/full/climate.2010.29.html

    And this chart nicely shows the last IPCC projections versus what more recent ranges of estimates show:

    http://www.nature.com/climate/2010/1004/fig_tab/climate.2010.29_F1.html

    Somewhere around 120-125 cm rise in the ocean levels by 2100 seems to a a good mid-range estimate now…more than double the last IPCC estimate, as Greenland and Antarctica look to accelerate their contributions of melting ice mass to the oceans.

  14. Bob, why factor in the glacial isostatic adjustment ?? Most people out in the real world want to know by how much sea level is actually rising relative to the land they live on. Just the facts – no contrived bells and whistles.

    The “scientists” who provide this information, are now clearly not a conduit to this data. You probably don’t need me to tell you your business, but I think you should be the alternative, more credible conduit to the real world data.

  15. Thanks as always for your work Bob.

    “Then again, mass from glacial runoff is also a major contributor to Sea Level. Did it temporarily increase for a few years after the 1997/98 El Niño? ”

    I have searched for it a few times, but it has vanished from my google fu, but I remember a report of a conference on Greenland glacial melt in 2007-8 about a British team which reported that “the melting stopped like someone turned a tap off”. Things got very shouty on the conference floor by all accounts…

  16. “jrwakefield says:
    August 18, 2011 at 4:01 pm

    Don K, thanks. Seems rather strange that the tidal guages show half what the satelites show, that some how the very year the satelites started to take measurements sea level also doubled, Don’t like co-incidences. There must be something fundementally wrong with the satelite data.”

    The satellite data could be wrong although “they” appear to try very hard to avoid that. Or the tidal gauge data could be wrong as it depends on knowing with great precision whether and how rapidly the gauges are sinking or rising relative to the (imaginary) geoid — something that is VERY difficult to determine. Or they could both be wrong. Personally, I’m inclined to go with the tidal gauges for now because of the much longer timespan. Even if the satellites are correct, 20 years of data seems to me to be way too short a time to draw conclusions about climate parameters unless one is measuring something where the magnitude of the changes dwarfs the uncertainties. But that’s just me probably.

  17. Andres Valencia: When I remove the last three months of data from the global Sea Level anomalies, the trend only increases approximately 0.04 mm per year, so I would suspect the recent increase is the result of the Glacial Isostatic Adjustment.

  18. Thanks Bob a great review on a very important topic that is difficult to understand. A couple of things I want to tip in:

    You say:
    As illustrated in Figure 19, the NINO3.4 region Sea Level anomalies precede the NINO3.4 SST anomalies and the Multivariate ENSO Index data. And they should. The NINO3.4 Sea Level data captures the Kelvin waves and the subsurface temperature anomalies traveling from west to east across the equatorial Pacific, which lead the response of the NINO3.4 Sea Surface Temperatures and many of the additional variables used in the Multivariate ENSO Index.

    I suggest that the sea level at the equator may be responding to warming of the sea outside the tropics that precedes the warming within the tropics. Its a big pond.

    I could be wrong in this because its not an area that I have taken a strong interest in but one thing that does not seem to get a mention when people talk about changes in sea level is the effect of change in atmospheric pressure and there is plenty of that. The AAO and the AO chart the changing relationship between atmospheric pressure at the poles and the mid latitudes.Over the last sixty years there has been a shift of atmospheric mass from the mid to high latitudes of the southern hemisphere to the rest of the globe. It might be useful to look at the mid to high latitudes of the Southern Ocean separately.It could be that the Southern Ocean has been rising faster than elsewhere. Indeed it might be useful to look at change by latitude specifically so as to see if atmospheric pressure effects can be detected.

    Given the deform-ability of the Earths crust could there be a change in sea level that proceeds from a change in the relationship between atmospheric pressure on land and sea. It might be worth checking the relationship between the hemispheres.

  19. I have a question. The recent Japan earth quake lowered parts of the Japan coast up to 1 metre, how many tectonic events have there been since 1900 and how have these effected the mean global sea level? My guess is, not much, but for someone who can determine that the Glacial Isostatic Adjustment is 0.3 mm, this should be a doddle.

  20. Bob – thanks again for the excellent data analysis.

    My comment is it looks like there might be a solar cycle signal in the data – for example in Fig 17. The problem is you’d have to have about 3 solar cycles worth of data in each of the 3 datasets before you had any chance at a multiple regression. Probably more. But is interesting that the biggest El Nino’s occurred at the solar minima and the biggest departure betweem MEI and GSL corresponding to the solar maximum. I don’t know why the Indian Ocean should be left out of this however.

  21. Thanks Bob and Anthony.

    Don K and jrwakefield,

    Interesting comments. One can’t but be sceptical of a satellite’s ability to measure a pear-shaped-geoid-with-flat-spots. As Bob Carter says, it’s at the limit of human knowledge, or words to that effect.
    As someone who has lived by the sea for over seven decades, I have had a very reliable benchmark on the east coast of Australia for the last five decades and on average, the highest astronomical tides of today are between 8 and 12 inches [20 and 30 cms] lower than they were forty eight years ago.
    This is naturally not the most accurate of measurements but it shows to me that there is no observable sea level rise.

  22. @R. Gates

    “Let’s see what AR4 has to say”

    So, essentially, you reference a IPCC report that is now 4 years old. A report that references even older scientific research, pseudoscientific research and opinion propaganda called grey literature. And you do it, I envision with a straight face, today? Although IPCC don’t deal with science but a few models of a bunch of more models that, according to IPCC, doesn’t include all the potential vital variables. And although you do know, because I’ve read as much, that you know that scientific process is an ongoing process, as in old research getting trumped by new.

    Question is though, why do you still destroy our climate?

  23. jrwakefield: Thanks for the link to the PSMSL webpage. I looked around their website but for some reason I could only find the daily data and I did not want to deal with that. The Sydney Fort Denison2 data gives some interesting trend results for the long-term and satellite-era:

    Or if we smooth the data with an 11-year filter:

    I doubt the rest of the stations would give similar results, but that was an interesting way to start.

  24. “philincalifornia says:
    August 18, 2011 at 4:25 pm

    Bob, why factor in the glacial isostatic adjustment ?? Most people out in the real world want to know by how much sea level is actually rising relative to the land they live on. Just the facts – no contrived bells and whistles.”

    ======

    There are two components to GIA, one controversial, the other uncontroversial, but maybe not entirely correct. The uncontroversial one is that the weight of the glaciers depressed the land underneath them. When the glaciers retreated, the land bounced back. Some of it in the northernmost latitudes is still rebounding/bouncing. So, if you are measuring sea level at Churchill, Manitoba and actual planetary sea level didn’t change at all for a century your tidal gauge at Churchill might tell you that sea level has dropped 80cm or so (I didn’t look up the GIA but I know it is very high). I don’t think anyone has any problem with correcting that out, although I have some doubts that the GIA corrections being made are all that accurate. It’s apparently not easy to compute GIA.

    The controversial component is much smaller. It comes about because the melted waters from the glacial icesheets have found their way into the oceans and their weight is purportedly depressing the ocean bottoms. CU claims to be correcting the sea level rise for this although I’m not sure that the correction is present in all their data. The correction 0.03mm/year isn’t large. I’m not a fan of this correction being made to sea level values. because it seems to reflect a sort of “phantom sea level change” that won’t show up on tidal gauges or satellite altimetry. The problem I perceive is that when using sea level marks from biblical times and before, this second GIA component is going to show up as offsets of a meter or more between analysts who apply the “correction” and those who don’t. It would be better I should think not to include this component in sea level measurements and to incorporate it as a correction to sea volume values in analyses where it is appropriate.

  25. “As someone who has lived by the sea for over seven decades, I have had a very reliable benchmark on the east coast of Australia for the last five decades and on average, the highest astronomical tides of today are between 8 and 12 inches [20 and 30 cms] lower than they were forty eight years ago.”

    =======

    The problem is that neither the ocean or the land will stand still. Measuring sea level is a bit like trying to measure the heights of a grade school class full of active four year olds. You need to take a lot of measurements in a lot of places then average them. For example, Churchill, Manitoba is rising because it is rebounding from the removal of a very thick ice sheet. New Orleans on the other hand is sinking because the sediments it is built on are compacting (pumping of ground water could also be an issue there). Tide gauges in either of those places will not give you an especially good idea of what it going on in the rest of the planet. The PSMSL and Colorado University web sites have reasonable overviews of what is involved http://www.psmsl.org/ http://sealevel.colorado.edu

    You may well be living in an area of local uplift. Other folks aren’t. It appears that on average the oceans are rising between 17 and 33 cm a century with a lot of local variations. And no, we don’t know why the numbers from satellites and tidal gauges are so different. I think everyone would be a lot happier if we did.

  26. Thanks as usual, Bob. I always appreciate the work you do. Sea level is also impacted by production of groundwater from no or slow to recharge aquifers, so called fossil water that has been in the ground for perhaps millions of years. This fossil water is about evenly divided between agriculture irrigation and make up water to evaporative cooling towers, primarily in steam power generation plants. The big players in fossil water production are India, China and USA.

    Water levels in the producing wells have started dropping which decreases the water production until larger pumps are installed and the pumps dropped lower in the well. The lower water production has been dropping for the past few years, especially in USA and China. At peak, the fossil water production, adjusted for some recharge, increased the sea level by 2.6 mm/year.

    JFD

  27. spangled drongo says:
    August 18, 2011 at 6:00 pm

    Don K and jrwakefield,

    Interesting comments. One can’t but be sceptical of a satellite’s ability to measure a pear-shaped-geoid-with-flat-spots. As Bob Carter says, it’s at the limit of human knowledge, or words to that effect.

    =======

    You darn well should be skeptical. However, it’s not prima facia impossible for the satellites to achieve sub mm accuracy in sea level measurements. The satellites do have a pretty good idea where they are and how they are oriented. They average many hundreds of thousands of data points a day. And wherever possible, they use differences between values, not absolute measurements. In short, they use every trick in the book to try to get meaningful sea level data that can be compared over time intervals. They question is whether they are making significant errors that do not average out and that add up over time. We just don’t seem to know for sure.

  28. The satellite measurements of sea level trend have error bars large enough to justify corrections of +/- 5mm/yr. The overlapping satellite trends from competing groups strongly disagree over the last 5 or 6 years. One gives around 3 mm/yr, while the other is closer to 0.7 mm/yr. One obvious ‘correction’ is to adjust the satellite trends to be close to the tidal gauge trend. But then you need to choose your reference tidal gauge(s) wisely.

    Nils Axel Morner has some things to say about the satellite sea level data.

    http://www.telegraph.co.uk/comment/columnists/christopherbooker/5067351/Rise-of-sea-levels-is-the-greatest-lie-ever-told.html

    “One of his most shocking discoveries was why the IPCC has been able to show sea levels rising by 2.3mm a year. Until 2003, even its own satellite-based evidence showed no upward trend. But suddenly the graph tilted upwards because the IPCC’s favoured experts had drawn on the finding of a single tide-gauge in Hong Kong harbour showing a 2.3mm rise. The entire global sea-level projection was then adjusted upwards by a “corrective factor” of 2.3mm, because, as the IPCC scientists admitted, they “needed to show a trend”. “

  29. The satellites probably measure very well. But the global ocean height is a calculation that has to take into account not just the noise of waves but of tidal influences that vary daily, weekly, monthly and longer, I’m sure. Then there is the temperature expansion component, as has been noted, which can be almost nothing to, in the case of the Pacific, a lot. Not to mention the non-spherical orbits of satellites that decay with time, and which earlier required unexpected corrections.

    An error analysis of the satellite data would be very interesting, I mean, the limits of certainty in each portion of the analysis and how the final result can have a certainty as described. The problem of certainty is in the adjustments to individual datapoints, not in the datapoints themselves. Intuitively I cannot see that there is equal accuracy and precision in the accuracy of the level proposed.

    Also, the Indian Ocean has warmed the most of all the oceans. Has the expansion in one ocean added an undiscussed, significant portion to the rise of the global oceans?

  30. If the 1998 divergence between sea level and ENSO was due to glacial melt, then the 2009 reconvergence must be un-melt. Tallbloke’s anecdotal reported research from Greenland may confirm this.

    Colodaro now predict increased sea level linked to an ending La Nina – but it looks like we’re heading back down into La Nina again. So they might be disappointed.

    Sea level is indicative of OHC so this recent decline particularly in the Pacific is important. What does it portend?

  31. Andres Valencia says:
    August 18, 2011 at 4:04 pm

    “One thing I noticed as I updated the Sea Level Research Group, University of Colorado, graph of 2011-07-29 in my page at http://www.oarval.org/ClimateChange.htm is that they have increased the rate from 3.1 to 3.2 ± 0.4 mm/yr.
    I can see no reason for that, given the latest lack of ocean level rising.”

    The answer is that due to recent sea level behavior the actual rate of rise had had declined to 2.8 mm per year using the averaging algorithm they’d employed for years. So they added a 0.3mm per year fudge factor to account for settling ocean basins, thereby changing “sea level” to “sea volume” (without relabeling their graph) which brought the rate of rise up to 3.1mm per year. Then they introduced a “new and improved” averaging algorithm to bring the average all the way back up to 3.2mm per year. The whole episode reeked of “tortured logic” employed to reach a per-conceived answer.

    Although I always do appreciate Bob’s meticulous write-ups, my eyes are now sufficiently glazed over by this one to assure an uncharacteristically swift decent into sleep at this late hour. Goodnight!

  32. If you read this ten year old article by John Daly you will understand all the big problems in using radar technology to measure sea level.
    In fact the problems are so great that the measurements must be corrected by calibrating them with reference to a selection of tide gauges. This of course means that the actual measurement is done by the tide gauges, not by the radar altimeter which only measures short-time fluctuations.
    Am I correct?

    See the article by John L. Daly:

    TOPEX-Poseidon Radar Altimetry:
    Averaging the Averages

    http://www.john-daly.com/altimetry/topex.htm

    Ágúst

  33. rbateman says
    ——–
    Nature does not do straight lines,
    ——–
    Opooop! rbateman has just declared Newton and a whole bunch of other crazy guys to be fools. Apparently light does not travel in straight lines, objects do not naturally travel in straight lines and a whole bunch of other stuff.

  34. Don K says: August 18, 2011 at 8:00 pm
    “..question is whether they are making significant errors that do not average out and that add up over time. We just don’t seem to know for sure.”

    The satellites can at least be “ground truthed” to all the locations on the planet where we have tide gauges which we know are very accurate with respect to the local sea level. It doesn’t matter too much about individual tide gauge sites moving up or down tectonically for example as the sheer number of physical sites we have will show whether the satellites agree with the local physical measurements consistently.

    I would have thought just taking the average of all the tide gauges is going to accurately measure the “global average sea level” anyway. On top of that sea level only matters locally to land masses anyway so is the more important measument anyway.

  35. Satellite orbit = 20,000,000 km. 2 mm = !0 ^-8%. (if my maths is correct)
    Accuracy of measuring method = sorry I don’t know but probably quite high in comparison.

  36. “Doug Proctor says:
    August 18, 2011 at 8:57 pm

    The satellites probably measure very well. But the global ocean height is a calculation that has to take into account not just the noise of waves but of tidal influences that vary daily, weekly, monthly and longer …”

    =====

    Yep, and it’s much worse than that of course. For example, they need to know the satellite orientation because the radar antenna isn’t at the altitude of the satellite’s center of mass and also because if the satellite is tilted the altimeter may be measuring the distance to something further away than the nearest point on the Earth. And floating ice or even heavy rain can introduce biases in the readings for areas where they are present. As far as I can see, honest attempts — many of them quite clever — are made to deal with the many problems

    I haven’t come across an error budget for satellites, but the JSON2 Handbook http://www.osdpd.noaa.gov/ml/ocean/J2_handbook_v1-4_no_rev.pdf contains a wealth of information on the design of that particular satellite.

    My bottom line: There are things to like about satellites for measuring sea level. Much more even coverage than tidal gauges for example. And they don’t really seem to need GIA adjustments — which doesn’t stop the nice folks at CU from making GIA adjustments anyway. But a reasonable person probably should be somewhat skeptical about their accuracy

  37. Maybe the tide guages are right, or maybe the satellites are.

    But if the tide guages are wrong, then they have been consistently wrong for a century or more in which case there is no evidence that sea level rise is accelerating.

  38. That systematic difference between guages and sats has to go bust sometime; the discrepancy is cumulative. Surely one or t’other has to suddenly be discovered to be way off?

    Stein’s Law: If something cannot go on forever, it will stop.

  39. Don K says:
    August 18, 2011 at 7:44 pm

    You may well be living in an area of local uplift. Other folks aren’t. It appears that on average the oceans are rising between 17 and 33 cm a century with a lot of local variations.

    Here’s a daft idea. We pick a few spots that have no isostatic rebound and no sinking issues and use those to determine actual sea level rises. Can these be identified? I don’t know why the likes of New Orleans and Japan would even be included in the measurements?

  40. Note on my last post: A “Per-conceived answer” is a lot like “preconceived answer”, only more dastardly..

    CH

  41. “Agust Bjarnason says:
    August 19, 2011 at 12:12 am

    If you read this ten year old article by John Daly you will understand all the big problems in using radar technology to measure sea level.
    In fact the problems are so great that the measurements must be corrected by calibrating them with reference to a selection of tide gauges. This of course means that the actual measurement is done by the tide gauges, not by the radar altimeter which only measures short-time fluctuations.
    Am I correct?”

    =====

    You’re certainly correct that measuring sea level from a satellite is a daunting task. I don’t think you are correct about the satellite measurements being calibrated against the tidal gauges although it would be astonishing if part of the initial test program for any satellite with an RA didn’t include cross checking its readings against the tidal gauges when it flies near them. I could be wrong, but the material I’ve read on JSON1,JSON2 and Envisat didn’t seem to involve calibration against the gauges

  42. David Schofield says:
    August 19, 2011 at 3:27 am

    ….

    Here’s a daft idea. We pick a few spots that have no isostatic rebound and no sinking issues and use those to determine actual sea level rises. Can these be identified? I don’t know why the likes of New Orleans and Japan would even be included in the measurements?

    =====

    One problem seems to be that sea level rise is extremely ill behaved. Over and above the land not standing still, sea level seems to be rising in some places, dropping in others on a fairly long term basis. Obviously that isn’t sustainable forever or you’ll end up with the entirety of the world’s oceans stacked up in a few favored locations. But the misbehavior can sustain itself for quite a while. Which means that you either need to look at the entirety of the world’s oceans — which satellites can do — or look at a long time span — which means sea level gauges that have been around for a long time and have continuous, reliably kept records.

    And it is also very hard to accurately identify tectonic movements. You’d think GPS could solve that and there is some talk of trying to do that. But it’s not as easy as it sounds either. GPSs tend to be better at lat long than elevation and sub millimeter accuracy would be needed. Probably it can be done? And probably it will be done? But as near as I can tell, it isn’t routinely done today.

  43. Bob Tisdale says:
    August 18, 2011 at 6:25 pm
    jrwakefield: Thanks for the link to the PSMSL webpage. I looked around their website but for some reason I could only find the daily data and I did not want to deal with that. The Sydney Fort Denison2 data gives some interesting trend results for the long-term and satellite-era:

    Or if we smooth the data with an 11-year filter:

    I doubt the rest of the stations would give similar results, but that was an interesting way to start.

    ————-

    So if the satelite data is correct, AND the tidal data is correct, the difference between the two would be that the satelite is ONLY showing a portion of some cycle, which is what the Fort Denison 2 graph shows. That being the case, then one CANNOT use the satelite data as a long term (out 100 years) trend, or is any indication of any “acceleration” in the rate of sea level rise. It also means at some point the short term rate will turn and start to drop, as Holgate 2007 noted has happened in the past. Thus, the REAL rate of sea level rise is the linear over all trend of the tidal data, which is around 1.74mm/year. Bearly 6 inches in 100 years. The next IPCC report should be very interesting, if they trend to honesty that is.

  44. Don K says:
    August 18, 2011 at 7:44 pm

    The problem is that neither the ocean or the land will stand still. Measuring sea level is a bit like trying to measure the heights of a grade school class full of active four year olds.

    ————-

    Which is why measurements from stable cratons are as close as you are going to get at measuring sea level, as opposed to land movement. South Australia is one, South Africa is another, south India may be another. There is little tectonic vertical motion at those places. The “Ring of Fire” is out, so is even the east coast of the US. Deposition onto the continental margins is changing the weight of the land mass, depressing it into the asthenosphere. Same with the entire European continent, too much tectonic motion. Even averaging all those locations is not a measure of sea level rise, it’s a measure of the average tectonic motion, a meaningless number. Tectonic motion changes the volume of the oceans, with a fixed volume of water, the average height of sea level changes just because of tectonic alterations of the basins. AGW’s claim is there is more water pouring into those basins because of melting ice. How one measures that is likely near impossible (does anyone really know how much new ice is forming where it’s not being measured?). The the other AGW component of sea level rise is thermal expansion. But it appears the oceans are now cooling, so if anything that should shrink the volume of water in the oceans. The question becomes, which is the dominant sea level motion? My guess would be local tectonic motion is the bigger “problem” (assuming a drop in land) than any over all rate rise.

    This is why there are very few places in the world where there is no tectonic motion, which is why I generally choose Sydney as my example of sea level rise is doing.

  45. Don K says:
    August 19, 2011 at 1:28 am

    Thanks for the link to the JSON2 Handbook Don, I have been looking for something like that for ages.

  46. “jrwakefield says:

    August 19, 2011 at 6:26 amThis is why there are very few places in the world where there is no tectonic motion, which is why I generally choose Sydney as my example of sea level rise is doing.”

    =====

    I was only in Sydney for a few days about 50 years ago, but my impression was that Sydney and Newcastle were on a dissected plateau. Sort of like San Diego’s mesas. Is that really a tectonically stable environment?

    I agree with your point re tectonic stability. Interestingly, the satellites can presumably measure land elevation as well as sea level. I wonder if, when we have a data record longer than 20 years, we might not be able to pin down the tectonics pretty well … even if it turns out, as it might, that the satellites can’t do so well with sea level. I’m assuming that the land returns are usable and are processed and stored. I can’t recall that I’ve ever seen that issue addressed.

  47. Pacific rises, flows into Indian, pacific falls, Indian rises. Simple :)
    Australian Baseline Sealevel Monitoring Project is a good reference. But still, we’re going to need some drastic serious upward movement in all these sea level measures to get to the 1-2m by the end of the century that the catastrophists keep throwing around. It’s going to put the next IPCC report in an awkward spot…all that heat that went in in the latter part of last century might just be working itself out of the system?

  48. Bob Tisdale
    Compliments on your explorations.
    Irrigation/water mining contributes about 25% of sea level rise – and has more than doubled since 1960. This may help with the differences you see.

    Restricting our analysis to sub‐humid to arid areas we estimate the total global groundwater depletion to have increased from 126 (±32) km3 a−1 in 1960 to 283 (±40) km3
    a−1 in 2000. The latter equals 39 (±10)% of the global yearly groundwater abstraction, 2 (±0.6)% of the global yearly groundwater recharge, 0.8 (±0.1)% of the global yearly continental runoff and 0.4 (±0.06)% of the global yearly evaporation, contributing a considerable amount of 0.8 (±0.1) mm a−1 to current sea‐level rise. . . .
    since the 1960s groundwater abstraction has more than doubled (from 312 ± 37 to 734 ± 82 km3 a−1), resulting in an increase in groundwater depletion from 126 ± 32 to 283 ± 40 km3 a−1. . . .
    We estimate the contribution of groundwater depletion to sea level rise to be 0.8 (±0.1) mm a−1, which is 25 (±3) % of the current rate of sea level rise of 3.1 mm a−1 reported in the last IPPC report [Bindoff et al., 2007] and of the same order of magnitude as the contribution from glaciers and ice caps (without Greenland and Antarctica).
    Citation: Wada, Y., L. P. H. van Beek, C. M. van Kempen, J. W. T. M. Reckman, S. Vasak, and M. F. P. Bierkens (2010), Global depletion of groundwater resources, Geophys. Res. Lett., 37, L20402, doi:10.1029/ 2010GL044571.

    The largest positive contribution to sea level probably comes from ground water mining, which means the extraction of ground water from storage in aquifers in excess of the rate of natural recharge.

    Ch 11 Changes in Sea Level p 657
    (But it was excluded from the evaluation.)

  49. Sea level changes are so slow, they are of no consequence. The mere fact we are here in current numbers is a function of cheap energy and plentiful leisure time, allowing humanity time to develop infrastructures that accommodate our various societies.

    When the current interglacial ends, will sea levels decline; leaving our port cities high and dry?

    R. Gates: Somewhere around 120-125 cm rise in the ocean levels by 2100 seems to a a good mid-range estimate now…more than double the last IPCC estimate, as Greenland and Antarctica look to accelerate their contributions of melting ice mass to the oceans.

    You got to be totally kidding. Assuming there is some linearity in accelerations of global temperatures from all sources (some yet to be discovered) is a false notion. Saddening there is such frantic paranoia in future climate based on the fears that it is humanity to blame and as if humanity could somehow change. The only skeptical attitudes are coming from the circle of AGW disaster mongers. The sky is falling!!!

  50. R. Gates,

    “as Greenland and Antarctica look to accelerate their contributions of melting ice mass to the oceans”

    Look to accelerate their contributions? Sometimes I do doubt your objectivity :)

  51. erl happ says: “I suggest that the sea level at the equator may be responding to warming of the sea outside the tropics that precedes the warming within the tropics. Its a big pond.”

    Erl, you’re right. They’re big ponds. And while I was reading your comment I was thinking of the biggest pond, the Pacific, not the two lesser ones. At times, I would agree with you that it appears as though the warming in the extra-tropics is preceding the warming of the tropics, but there’s also a lot of short-term overturning, where warm subsurface waters that had been distributed poleward during one of the larger ENSO events is returned to the tropics to serve as fuel for another. I can recall a paper by a researcher from Japan who was looking for a subsurface current that carried waters from the KOE area toward the Pacific Warm Pool.

    As you’re aware, Sea level data is difficult to work with because there are so many variables that contribute to it. Many of them have been mentioned by you and others on this thread. That’s way too many variables for me to be concerned about, which is one of the reasons I don’t spend a lot of time analyzing Sea Level data. And of course, like OHC data, we’re looking at a two-dimensional dataset of a three-dimensional variable. So even if we could isolate the thermal component in sea level, we don’t know the depth of the anomalies. Hopefully, with ARGO in place, the resolution of the temperature data at depth will improve. And when they get all of the ARGO bugs worked out, we can hope for a couple of significant ENSO events so we can, during a La Niña for example, determine where the vast volume of warm water carried west by a Rossby wave at 10N goes after it slams into Indonesia. How much is deflected, how much remains trapped, etc.

    Regards

  52. Bob,

    I think there’s a better fit line that goes through -30 in 1994, and about +17 in 2006, and then the slope suddenly flattens out.

  53. George E. Smith says: “I think there’s a better fit line that goes through -30 in 1994, and about +17 in 2006, and then the slope suddenly flattens out.”

    I simply click on a few pull-down menus in EXCEL to create the trend lines and theyr’e created through linear regression analysis performed by EXCEL.

  54. In my reply to Erl Happ above, I noted the difficulties of trying to study Sea Level anomaly data, but one thing is certain, the resolution of the data makes for great sea level .gif animations (6MB):

  55. RGates,

    Taking this rignot paper as a lead
    http://www.agu.org/pubs/crossref/2011/2011GL046583.shtml

    It looks like 100 Gt of melting Greenland ice contributes about 0.27mm to sea level rise.

    From memory the highest estimated mass loss from GRACE data was in 2010 at ~600Gts, that’s 1.64mm. Prior to that most estimates of annual Greenland melt were in the 200Gt range. The idea that the ice sheets account for the difference Bob found seems wrong. Both the timing and magnitude looks all wrong.

  56. I remembered wrong. There was `600Gt greenland loss during summer 2010 which was partly offset by some winter accumulation. Nett change in 2010 was about 450Gt.

    From this graph

    and some rough eyeballing then the contribution to SLR from GRACE looks something like this.

    Year Gt ice loss mm SLR
    2002 150 0.405
    2003 200 0.54
    2004 150 0.405
    2005 200 0.54
    2006 250 0.675
    2007 250 0.675
    2008 250 0.675
    2009 250 0.675
    2010 450 1.215

    You can set the error bars wherever you like and I encourage anybody to workout there own better estimates but it doesn’t look like the mid decade interannual variability is comming from Greenland melt.

  57. HR,

    Could you possibly find a chart with a more alarming y-axis? Probably not. The problem with screwballs like John Cook is that he feels it necessary to fabricate such preposterous charts.

    What we are observing is the planet’s continuing emergence from the LIA. It is natural regional variability. If it were runaway global warming, the warming would clearly be global. But it’s not. It is mostly regional effects.

  58. To appreciate the reliability of the current state-of-the-art sea level measurements from satellite altimetry and global and regional trends derived from them, it may help to take a (sobering) look at

    http://www.aviso.oceanobs.com/en/calval/overview/index.html

    in particular under the header Cross-comparison between satellites, the figure titled
    “Differences of trends of SLA between Jason-1 and Envisat in 2004 and 2010”

    This is just a a sample result in an overview; the French researchers at CLS and CNES are doing much more excellent cal/val work like this.

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