SEA LEVEL: Rise and Fall – Part 5: Bending the Trend

By Kip Hansen — Re-Blogged From WUWT

USA Today shouts: “Rise in sea levels is accelerating along U.S. coasts, report warns”.   Many other media outlets have repeated the story:  The Guardian, The Hill, and U.S. News and World Report.   All of these make the same claims:

The report’s key message “is a clear trend toward acceleration in rates of sea-level rise at 25 of our 32 tide-gauge stations,” said Virginia Institute of Marine Science emeritus professor John Boon in a statement. “Acceleration can be a game changer in terms of impacts and planning, so we really need to pay heed to these patterns.”


“Although sea level has been rising very slowly along the West Coast, models have been predicting that it will start to rise faster,” the marine science institute’s Molly Mitchell said.”

The National Oceanic and Atmospheric Administration  also has warned about sea level rise acceleration. It has noted that by the end of the century, global sea level is likely to rise at least one foot above 2000 levels, even if greenhouse gas emissions follow a relatively low pathway in coming decades.”…. “On future pathways with the highest greenhouse gas emissions, sea level rise could be as high as 8.2 feet above 2000 levels by 2100,” NOAA warned.” …. “Mitchell said that “seeing acceleration at so many of our stations suggests that – when we look at the multiple sea level scenarios that NOAA puts out based on global models – we may be moving toward the higher projections.”

[ Note:  My West Coast counterpart, Willis Eschenbach, has covered part of this story in an earlier essay today titled: Accelerating The Acceleration, and he does so in his own inimitable mathematical style.  You won’t find much duplication here as I hit it from a different angle. — kh ]

All of the media pieces say “according to a new report.”   There is no new report. The link goes to Virginia Institute of Marine Science (VIMS) website, the page of their U.S. Sea-Level Report Cards.  There was a report last year, which is self-published by VIMS, and is not, as far as I have been able to determine, peer-reviewed.

The news stories all stem from this press release issued by VIMS and written by one of their co-authors, David Malmquist.   And the true source of the data and the “report”?  VIMS emeritus professor John Boon, who retired in 2002 yet still puts out reports claiming Sea Level Rise Acceleration.

How much acceleration?  Let’s look at the data that prompted this news item from KTVU television in San Francisco, California:


Here past of what they say:

“Researchers at Virginia Institute of Marine Science (VIMS) issued their annual report card which looked at tide-gauge records for 32 coastal locations, stretching from Maine to Alaska. The analysis included 51 years of water-level observations, from January 1969 through December 2019.

“The key message from the 2019 report cards is a clear trend toward acceleration in rates of sea-level rise at 25 of our 32 tide-gauge stations,” said VIMS emeritus professor John Boon.” 

The KTVU report is one of the few that give numbers to back up these claims (kudos to KTVU):

“San Francisco’s rate of sea-level rise last year was 1.91 millimeter, and Alameda saw a yearly increase of 1.10 millimeter. The sea-level acceleration rate measured at 0.03 mm and 0.05 mm, respectively at those tide-gauge stations. Researchers projected that if this continues, sea level in San Francisco and Alameda will be almost .5 feet higher in 2050 compared to 1992. “  [ emphasis — kh ]

[Technical Note:  All acceleration numbers should be in units of mm/yr/yr or, alternately,  mm/yr2 both in the news pieces and in my essay –kh ]

Let’s look at this in the image provided in VIMS’ report card:


Sorry to make that image so BIG, but if I had not, you wouldn’t have been able to see the Sea Level Rise Acceleration at all.  It is those little orange bars right above the zero line.   Note that the official NOAA specification for tide gauges states that the estimated accuracy for tide gauge monthly means is +/- 5 mm.  I have added that range on the chart for your convenience — but I had to stretch the height of the chart to fit it in, because, for the mathematically inclined, the estimated error range for tide gauge monthly means (and thus the above annual trends as well) is 200 times the size of the reported acceleration for the Alameda tide station and more than 300 times of the acceleration for San Francisco.

How does Boon et al. manage to measure these infinitesimal acceleration rates in spite of the oversized known measurement error range?  Like this:


Since at least as early as 2012, Boon and his team at VIMS have been trying to convince the world that “sea level is accelerating!”  They do it by bending the trend line….and then, like all good climate scientists, extending their trend line into the far future.  Of course to do so successfully, they have to have a data set that is not too long — so in this case they start all of their calculations in 1969. The chart above though labeled “Anyport, USA” is in fact the data for Sewells Point (Norfolk), VA.  The real NOAA chart looks like this:


Boon et al. obscure the data by throwing a “decadal signal” on top of the actual measured data, and then, using their own proprietary formulas, calculate a quadratic trend line for the data segment 1969-2019.  They have been doing this since 2012 — so let’s see how their acceleration predictions have worked out.

Here is the chart from the 2012 report:


Boston is shown as having a linear trend of 2.882 mm/yr.  (ignore the ridiculous thousandths of millimeters claim for now).    Here’s NOAA on Boston, showing a rather monotonic steady rise of about 2.8 mm per year since the 1920s.


But, Boon’s 2.88 isn’t all that different.  At the end of 2011, Boon says that Boston has an acceleration of 0.15 mm/yr.  So by 2015, that rate should be 3.482.  Let’s see….in Boon’s 2015 paper:


Ah ha, Boon has shifted to new system of calculation described as “Contoured joint probability density of parameters”, so that instead of simple numerical predictions, we have predictions at “height percentiles”.  But, giving Boon the benefit of the doubt, we’ll look at his mean number (50%) for Boston SLR for 2015, which is now 3.07 mm/yr.   Boon’s 2012 prediction is off by about 15% — relative sea level at Boston, over these four years, only increased by 0.04 mm/yr (if the increase is even in fact real, as it is vanishingly small compared to the know measurement error range).

How about the latest “Report Card” for Boston?  It shows some interesting things.


The chart at the VIMS site is an interactive chart (unlike my modified screen chart above).  Mousing over a data point at the VIMS site gives the numbers I use above and in the following.

There are differences between published Linear Rate data and the chart above, but they are smaller than those for Acceleration data.   The calculated acceleration for Boston does not actually show up in the Linear Rate.  The interactive chart just posted this month shows that Boon found acceleration in 2011 of 0.305 mm/yr at Boston.  Thus, by 2015, four years later, there should have been an increase in the linear rate for the annual single year, 2014, of an additional 1.2 mm — that obviously did not happen.  If we apply the Boon (2012) published acceleration rate of the much lower 0.15 mm/yr for eight years to 2019, it should add 1.2 mm/yr to the linear rate through 2019.   Using Boon’s 2019 Report Card interactive chart, 2011 is shown as 2.93 mm/yr and 2019 is shown as 3.22 mm/yr.  Simple math gives us a difference in linear rates of only 0.29 mm/yr, which, divided by the eight years, reduces to 0.03625 mm/yr — only about one tenth of the 0.305 mm/yr  predicted for 2011 on Boon’s online interactive chart.

Let’s try the 2009 Annual Acceleration Rate of 0.251 mm/yr.  If we hold that constant over ten years, to 2019, it would have meant an Annual Linear Rate for 2019 of  2.411 (in 2009)  plus 2.51 of ten years of Annual Acceleration for an predicted annual Linear Rate in 2019 of 4.921 mm/yr.  The actual calculated annual Linear Rate for 2019 is 3.22.

The point is that the calculated Annual Accelerations are not adding up or showing up over the following years as Annual Linear Rates as predicted by charts such as this:


Let’s take a closer at just the last decade, covered by the Boon et al. reports discussed above:


On the left is the NOAA  Tide Gauge at Boston, the same monthly mean sea level data used by Boon, in the segment on the right.    The past decade shows that mean sea level dropped at Boston  starting at 2010 for five years and then rose again to back up to the same level by the end of 2019.  (There may be some data break at 2009, where there is a sudden shift upwards of almost 10 mm in a single month — don’t know if there was any equipment or location change then.)  While there is no doubt that Mean Sea Level at Boston is rising, there is no change that seems any different than the simple assumption of a continued, monotonic steady rise.  Boon’s use of the solid blue line (decadal signal) and the orange “quadratic trend” obscure and confuse the long-term view, as shown in the NOAA Tide Station chart far above.

Interested readers can download the VIMS 2018 report here and refer to their updates for 2019 here.

Bottom Line:

Boon, although long retired,  and his group at VIMS have been touting sea level rise acceleration for almost a decade now.  It is their thing and apparently they are convinced of its truth.

The past published acceleration rates do not actually appear in their own futures — the rates published in 2012 do not appear in the mean sea level increases in 2019.

Any times series, and any segment of a times series, should show an acceleration (change in rate-of-change — faster or slower) over time, as it is unlikely that any real series of measurements of a natural phenomenon remain exactly constant.  However,  Boon’s Acceleration Rates found for the West Coast in the 2019 reports cards are implausibly small given the known Error Range for Monthly Means for NOAA Tide Gauges and I would not consider them statistically significant and certainly not climatically significant.

Developed areas, anywhere in the world, that have been built within a few feet of today’s Relative Mean Sea Level  and local Mean Higher High Water for their locality are already in imminent danger of being damaged by extreme tides, surges from today’s storms and from tsunamis if in areas prone to such.  These localities need to urgently begin mitigation efforts.

For now, most coastal areas should plan on Relative Sea Level continuing to rise at its long-term rate for their locality and in planning, add on extra leeway in case warming waters begin to rise a bit faster.  No one needs to panic or plan for the near-impossibility of multi-meter sea level rises over the next century.


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