Sea Level Update: Extended Revision Details

I covered the basics of the update yesterday and there has been some interesting discussion so far.  Some of the ideas are mere suggestions and others are based on the information that the Sea Level Research Group (SLRG) has put out on their website.  So I am going to discuss three different aspects of the update.  First will be the Glacial Isostatic Adjustment (GIA) that they are using to justify the 0.3 mm/yr increase in the data.  Then the suggestion that recent La Nina’s have caused the rate of sea level rise to decrease in the recent past.  Finally I will show the acceleration of the new data.

Glacial Isostatic Adjustment:

On the SLRG website there is a page dedicated to explaining why the sea level should be naturally dropping by a rate of -0.3 mm/yr.  This is because some land is rising and some land is decreasing in elevation relative to the Earth’s center as a rebounding effect because the weight of the ice sheets from the last glacial period is no longer present.  That rebound effect goes by different names (most commonly Post Glacial Rebound), but for this article I will use the GIA that they use.

The NASA website that I linked to is very clear that there are many different models used to determine the GIA.  All of this is based on the GRACE measurements.

The Inconvenient Skeptic

One models results for PGR which is the basis for the GIA that is now used in the sea level data.

The red locations are increasing in elevation and the blue are decreasing in elevation in this map.  The heavy red locations are generally the places where the ice sheets were compressing the continents for ~100,000 years during the last glacial period.  This is certainly a clever way to justify an adjustment to the data.

Let’s compare to where the sea level has been changing.

The Inconvenient Skeptic

Map of where the sea level rise has been happening.

This map shows no correlation to the GIA map at all.  This map shows that the change in ocean level is happening where the ocean temperatures have been showing the most change.  The ocean is not like a bathtub and it responds in a vastly more complex way.  Compare the Atlantic Ocean around the southern part of Greenland.

That location is showing high rates of sea level increase, but that also the place that “should” be showing the largest drop in sea level.  The main paper referenced for the GIA (primarily Peltier 2002) clearly states that it is a model based attempt to describe the dynamics of a “spherically symmetric internal viscoelastic structure for the solid Earth.“  This is not the type of work that is of sufficient quality or understanding to justify the type of adjustment to a direct measurement.  The dynamics of the ocean are simply too complex for a simple 0.3 mm/yr blanket adjustment of the type they are performing.  It is simply unwarranted.

The changing currents of the ocean are clearly important to the actual change in sea level.  Anyone familiar with the currents will recognize this from the change in sea level map.  Currents and the temperature of the currents are far more important to the changing sea level.  I see no basis for a GIA that is in excess of 10% the activity that has happened in a 20 year basis.

ENSO and Sea Level:

Somewhat related to the regional MSL map is the topic of ENSO and sea level.  The suggestion that the recent La Nina’s in 2007 and 2010 are the cause of the reduced rate in sea level rise is truly absurd and easy to disprove.  There is certainly some impact to the specific year in question (which is why this might seem plausible), but overall there is no connection between ENSO and the rate of the sea level change.

This is simply based on the fact that the years that had the highest overall rate of sea level change.  According to the new data and the old data, 2001 had the single year highest rate of sea level change from 2000.  The total change in sea level that year was a significant 5.7 mm.  At that highest rate ever recorded of sea level change, it would only take 175 years for the sea level to rise 1 m.  That also happened to be a La Nina year.

The other fact is that the rate since 2005 has been less than 2 mm/yr, but there have been more El Nino that La Nina between 2005-2010.  So while events like the 1998 El Nino do show up, in the year to year sea level change there is very little correlation between ENSO and sea level.  It is a nice distracting idea, but it even undermines the idea of sea level rise if one blames La Nina for a low rate of sea level rise because the converse would also be true and that would blame a high rate on El Nino.  I am sure that was not the intent in that suggestion though.  Blaming El Nino for warming and sea level change would be bad for the Theory of Global warming.

Updated Sea Level Acceleration:

Finally it is time to take a look at how the sea level is decelerating.  They might have managed to get 2010 to not show a drop in sea level with the GIA adjustment, but the anaemic rise of  0.7 mm from 2009 is still not good news for warmists.  At that rate it will take 1428 years for the oceans to rise one meter.

My method is straightforward.  I take a 5-year regression for the sea level for each year.  So the most recent year is 2008 so a linear regression from January of 2006 – December of 2010 is the rate of rise for 2008.  That is why it is the most recent year as 2011 is not yet complete.  Here is how it looks overall for the satellite sea level measurement.

The Inconvenient Skeptic

Rates of sea level change over 5-yr periods from 1992-2010.

The slope of each line can then be used to determine the true acceleration of the sea level.  If you think CO2 is causing the oceans to rise, this might be a good time to stop reading as this is not the result that fits with the theory of global warming.

The Inconvenient Skeptic

The straight line is the regression of the 5-yr rates. That is the definition of "acceleration." It is also negative.

The GIA has adjusted the deceleration of the sea levels from the previous data.  Previously the deceleration was -0.15 (mm/yr2).  That has now changed to:

Current Sea Level Acceleration = -0.13 mm/yr2

This predicts that the sea level will start to drop on average in the year 2028 instead of 2025.  The height of the sea level then will be about 12 mm higher than it is today.  So the deceleration of the sea level continues.  It is good to know that every year the odds of the 1m rise in the sea level by 2100 are getting longer and longer.  Even at the highest measured rate every it would be 2180 before that rise would happen.  At the current rate it will be more than a 1,000 years away.

Posted in Ocean: Sea Level and SST by inconvenientskeptic on May 10th, 2011 at 6:20 am.


This post has 3 comments

  1. John,

    Great work on this interesting topic. Sea-level rise certainly is a low priority “problem” even if it is interesting to track.

  2. Lorne50 May 11th 2011

    Thx for this it is all falling apart the world will die part well done put the paper forward!

  3. Richard111 May 15th 2011

    This sea level change business is another distraction like the global temperature change. Keep everyone arguing while the laws are changed behind your back.
    0.3mm/y is less than an inch in the average lifetime. Even 3mm/y is just over an inch per decade. Six or seven inches in the average lifetime. If we are going to see any part of New York flooded by 2100 then the evidence will be very visible right now.
    I live within 100 yards of a harbour built over 150 years ago. You can still see traces of the original stone steps giving access to the bottom when the tide was out. Now harbour access is controlled by lock gates but the steps reach up to the present quayside level. Even with a local tidal range of over seven metres during spring tides there is no sign water rises above the scum line on the harbour walls.
    Even if the sea does rise above any presently predicted rate there will be plenty of time to adapt and rebuild. Certainly my local harbour would benefit from a facelift. Oh, yes, and we need the jobs too.

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