Bruno 2

Someone calling himself “Giordano Bruno” is determined to convince us sea level rise isn’t a problem, and in particular it isn’t happening at an increasing rate. He’s at it again at WUWT. I think it’s a self-flattering pseudonym for Albert/Alberto “making up stuff Parker/Boretti,” but let’s set aside his nom de plume and look at his “evidence.”


It consists of this:


For the specific of the United States, the average relative sea level rise is constant at about +1.7 mm/year mostly due to subsidence totaling on average less than 20 centimeters sea level rise by 2,100.

bruno-fig1a

bruno-fig1b

Figure 1 – a, b) Relative sea-level rise for the United States (images from [2] downloaded May 16, 2016) over the time window of data 1930 to 1999 and 1930 to 2014. The relative rates of rise are quite similar, somewhere larger and somewhere smaller, to demonstrate they haven’t accelerated that much. Over this century, the rates of rise of sea-levels haven’t accelerated that much in the United States. Similarly, in every other area of the world where they are measured.


What he’s doing is comparing the linear rate of (local) sea level rise from 1930 through 1999, to that from 1930 to the present (basically, through 2015). He concludes that they’re “quite similar” and that establishes “the rates of rise of sea-levels haven’t accelerated that much in the United States.

I’ve mentioned before that it’s a bad idea to compare trends from two time spans that use most of the same data. In this case the two time spans he considers have 70 out of 86 years (81%) in common, so it’s no surprise they’re “quite similar.” And he doesn’t actually show the differences between rates, he just shows a graph of each and says “quite similar.” How precise!

Here’s a better idea: let’s compare the 1930-1999 episode to the 2000-2015 episode without overlap (the 2nd section is all too brief, but we’ll humor “Bruno”). For each series, I’ll fit a continuous piecewise linear trend — piecewise linear to get a linear slope estimate for each span, continuous so we’re not fitting a “broken” trend. Then I’ll compute the difference between the rates of sea level change during the two separate time spans. I’ll also omit inland stations; I’m not really interested in what’s going on along the St. Lawrence River. I’ll plot the results as dots, using red for rate increases and blue for rate decreases. Here it is:

dr_2000

It’s easy to see that most stations have shown an increase in the rate of sea level rise, especially on the eastern seabord. The largest rate increases (the biggest red dots) are from Cape Hatteras to Cape Cod, part of the “northeast hotspot” identified by Sallenger et al., which “Bruno” doesn’t seem to believe in.

At these stations, the rate of sea level rise has increased from an average of 1.38 mm/yr during the 1930-1999 span, to 2.16 mm/yr during the 2000-2015 span. That’s an acceleration — an additional 0.78 mm/yr. Much of the reason for the low average rate is the local fall of sea level at stations in the far northwest, due to glacial isostatic rebound; here are the actual rates (not rate differences):

rate_2015

If we restrict our attention the the Eastern U.S., the rate of sea level rise has increased from an average of 2.89 mm/yr during the 1930-1999 span, to 4.75 mm/yr during the 2000-2015 span. That’s a sizeable acceleration — an additional 1.86 mm/yr.

As an aside, I wonder why local sea level appears to be decelerating in the far northwest, especially Alaska. It makes me wonder: is it possible that the shrinking of Alaska’s glaciers has increased the rate of glacial isostatic rebound, thereby increasing the rate of sea level fall? I don’t know nearly enough about glacial rebound even to know whether or not such an idea is plausible — but it’s interesting to consider.

Despite “Bruno’s” efforts, not only does the ocean continue to rise, that rise is accelerating. Not only does it threaten coastal areas in the U.S. (especially the east coast), the rate of increase along the eastern seaboard has accelerate even more than in other areas. And despite the ease with which he garners praise from the readers of the WUWT blog, when it comes to his understanding and his analysis of sea level rise, we are not impressed.


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19 responses to “Bruno 2

  1. Robert Way

    Yes Tamino, it is very plausible that accelerating ice losses could be linked to increased GIA.

  2. michael sweet

    Tamino,

    It appears that one of your points is in or near Tampa, Florida. Since I live there, what was the rate of increase in Tampa over the interval 1930-1999 and 2000-2015?

    Thanks for your help.
    Mike Sweet

    [Response: It’s the tide gauge station at St. Petersburg. Rate 1930-1999 is 2.25, rate 2000-2015 is 5.19 (mm/yr).]

    • michael sweet

      A newspaper report today said that the Tampa area has the greatest amount of real estate at risk in the USA from a high storm tide. (I would have thought Miami or New Orelans). 70×2.25 + 15×5.19= 157 mm + 78mm = 235 mm = 9.25 inches total. We are expecting flooding rain from a small tropical disturbance Monday night. This weekend is spring tide so there might be a high tide with the rain.

      There is a seciton of Tampa called Bayshore where there are a lot of very expensive houses on the Bay front. Bayshore Blvd. will certainly flood. It would be interesting to see if the flood is more than 9 inches of water.

      New waterfront houses are always built on a 6 foot (or greater) pad and usually have a sacrifical first floor so they can take 15 feet of flood before the inside of the home is flooded. Older or middle class houses are built on the ground.

  3. Pat Cassen

    The gravitational effect of land-based ice sheets on local sea level is also important; sea level near melting ice sheets and glaciers decreases . Presumably, accelerating ice sheet melting results in faster decrease of sea level. See this interview with Jerry Mitrovica for a nice explanation.

  4. Dave Werth

    Another factor along the west coast north of about the southern Oregon border is subduction zone uplift along the coast. Once the subduction zone earthquake occurs the uplift will release and there will be an immediate relative rise in sea level.

  5. It works for temps too.

    I have calculated the GISTEMP trends for 1880-2014 and 1880-2015 and find that they, too, are quite similar.

  6. Whachamacallit

    I could imagine that the Northwest may be getting some isostatic rebound, but could it also be tectonic activity? After all, Alaska has the most volcanoes of any state. Also, what’s with that sea level rise decrease around Louisiana. Isostatic rebound makes no sense, and it’s not very geologically active.

    • My stab at why SLR rate may be decreasing around La. is that there were high rates pre-AGW due to (1) levee-ing off the silt supply (2) erosion-accelerating canals in the swamps (3) extraction subsidence.

  7. andreas dobbertin

    The local effect of a shrinking ice shield is a reduced gravitational pull, thus resulting in a falling local sea level. A quite counterintuitive phenomenon. Jerry Mitrovica, Harvard, explaines it here : https://www.youtube.com/watch?v=MEjZJ8_W4c4 , at 20:20 . Current state of Greenland mass loss can be found here : http://polarportal.dk/fileadmin/polarportal/mass/Grace_curve_La_EN_20150800.png.

  8. edaviesmeuk

    According to this uplift in SE Alaska is due mostly to ice loss since the Little Ice Age, rather than since the Last Glacial Maximum as I would have guessed:

    http://fairweather.alaska.edu/chris/motyka.pdf

    The references there might give more details.

  9. “Also, what’s with that sea level rise decrease around Louisiana. Isostatic rebound makes no sense, and it’s not very geologically active.”

    I know that subsidence is a big part of the picture in Louisiana, and recall that part of that issue is extraction of fossil fuels. I’m wondering if that contribution is nearly exhausted onshore?

    (Searching…)

    …And the notion finds some support in a review article– doi: http://dx.doi.org/10.2112/SI54-012.1– which states that:

    “… in Louisiana a connection between hydrocarbon withdrawal and subsidence appeared well established by a historical releveling survey line (Shinkle and Dokka, 2004) and a comprehensive land loss survey of the Mississippi River delta and Chenier plains (Britsch and Dunbar, 1993), which both took place in regions containing many hydrocarbon producing fields. The land loss rates were correlated with the rates of fluid withdrawal during hydrocarbon production (Figure 13), which started regionally in the 1950s and peaked in the 1970s (Morton, Buster, and Krohn, 2002).”

    Incidentally, there is indeed a component of glacial isostatic rebound in the picture:

    “The last glaciation of North America loaded much of the northern half of the continent with the weight of the Laurentide Ice Sheet, which caused crustal flexure and subsidence. Outside the margins of the ice sheet, isostatic compensation caused local uplift and the creation of a forebulge. Analyses employing numerical models suggest that the expanse of the forebulge included much of the north-central Gulf Coast (Figure 10). Upon the retreat of the ice sheet during the initiation of the current interglacial period, the loss of ice mass triggered widespread isostatic readjustment, observed as both an uplift of the previously subsiding regions as well as a collapse of the forebulge (Figure 11).”

    The article goes on to say that isostatic subsidence appears to be continuing at a pretty slow, steady rate, so though it exists in Louisiana, it doesn’t look like a good candidate to account for the change in recent decades.

    A better one might be the loss of marshlands: ‘dewatered,’ they subside due to loss of hydrostatic pressure and to speedier oxidation and decay processes. If the rate of marshland loss had slowed, that could help to account for the slowing of subsidence.

    Anyway, good paper if you want to dig in. It’s here:

    http://www.jcronline.org/doi/full/10.2112/SI54-012.1

    Overall, the situation in southern Louisiana is pretty dire:

    http://thelensnola.org/2013/02/21/new-research-louisiana-coast-faces-highest-rate-of-sea-level-rise-on-the-planet/

  10. See NOAA… Thank you…

  11. I was really surprised by the strength of the gravitational effect of land ice on sea level. It’s so strong that the total melt of the Greenland Ice Sheet, which would increase global sea level by an average of 7m, results in zero net sea level increase for Scotland.

    The flip-side to this result is that the melt of Antarctic ice sheets will have a much greater impact them the global average figures suggest.

  12. Can you fit a linear trend to the whole dataset, then a quadratic, then do a partial F-test to see if the quadratic term is justified?

  13. John Mashey

    I assume tamino knows:
    https://en.m.wikipedia.org/wiki/Giordano_Bruno

    But others might want to review that, since using the name is akin to using a Galileo handle, but implying even worse martrydom for science.

    Both names were invoked as comparisons for Murry Salby, Pseudoskeptics exposed in the SalbyStorm.

    Search for Giordano in the PDF of comments for context.

  14. Tectonic effects on sea level rise are generally larger than the effects of glacial melting and unloading in Alaska. The area near the 1964 earthquake in Prince William sound is seeing rapid tectonic subsidence while most of the rest of the coast is seeing uplift. See this little ADN article which has a link to further information: http://www.adn.com/alaska-news/article/southern-alaskan-sea-levels-defy-worldwide-trends/2010/12/28/

    Because coastal Alaska is so geologically active it’s a really bad idea to include sea level observations there with the rest of the U.S. in making averages. It’s very misleading to do so.