Sea Level Projections vs. Tide Gauge Data

February 28, 2016

Carbon dioxide, climate change, disaster, SEA LEVELS WILL RISE!

You can see all kinds of sea level rise predictions for the 21st century, with over-wrought images of houses and buildings under water.  One of the favorite predictions of the hand wringers is “1.8 meters” of sea level rise for the 21st century.  A major purveyor of this lurid climate-porn prediction is Stefan Rahmstorf (see here, here, and here).

Consider the following points

• 75% of atmospheric anthropogenic CO2 arrived after 1950.
• There has been no obvious acceleration in sea level rise rates since 1950 as seen from tide gauges.
• Extrapolating tide gauge time series to 2100 would give about 15cm of sea level rise between 200o and 2100.
• Projections of 1, 1.8 or 2 meters of sea level rise between 2000 and 2100 would require extraordinary rise rate accelerations.

Let’s compare the sea level data of the 20th century with these wild prediction for the 21st century.  The movie below will show all the tide gauge data sets available from NOAA that extend over at least 75 years.  In each case the trend is extrapolated to 2100.  Additionally, the likely local relative sea levels corresponding to 1 meter and 1.8 meter global sea level rises for the 21st century are shown.

Music is by Mechett and licensed under Creative Commons

The likely local relative sea levels are calculated by by assuming that the global anthropogenic sea level rise would be distributed evenly over the planet.  This assumption may not be entirely accurate but it is a good first approximation. Here is how the calculation is done.

Let

• GSLR (20th century) be the 2oth century global sea level rise
• LSLR (20th century) be a local 20th century sea level rise
• GSLR(21st century) be the projected 21st global sea level rise
• LSLR(21st century) be the projected local 21st century sea level rise

Then
LSLR(21st century) = LSLR (20th century) – GSLR (20th century) + GSLR(21st century)

Say the 2oth century global sea level rise was 18cm and the projected 21st century global sea level rise is 100cm.   And say the local 20th century sea level rise was 18cm at location A, 30cm at location B, and -10cm at location C.  Then the local projected 21st century sea level rises would be

Location A
Projected rise = 100cm = 18cm – 18cm + 100cm

Location B
Projected rise = 112cm = 30cm – 18cm + 100cm

Location C
Projected rise = 72cm = -10cm – 18cm + 100cm

Alarmism at Scientific American (again)

February 24, 2015

Scientific American is such an embarrassment.  It’s sad, because I used to like that magazine.

Once again they are shills for the global warming alarmists, scaring people with wildly exaggerated claims about sea level rise.  This time Colin Sullivan writes that the sea level at New York City could increase by six feet by 2100.

Heat waves and floods caused by climate change could mean disaster for the Big Apple’s five boroughs by the end of the century, with sea levels now predicted by a new report to climb by as much as 6 feet by 2100.

Really?  6 feet by 2100????

First, lets start with a minor point.  Real scientists and science writers usually don’t use “feet,” they use meters.  So why does Scientific American use “feet?”  My guess is that it is some linear combination of the following two reasons: the Scientific America audience isn’t really scientifically literate these days, and “6 feet” sounds like more than “2 meters” (even though it is actually slightly less).

Now, lets get to the major point.  Any responsible journalist writing about sea level rise in at New York City would present the historical data.  There are nearly 150 years of sea level rise data available for The Battery (at the southern tip of Manhattan) from NOAA

Do you notice that the sea level rise is less than 3 mm/year?  Can you detect an acceleration over the past 150 years?  The sea level at the Battery will go up about 22 cm by 2100 at the present rate.  To go up 6 feet (1.83 meters) by 2100 it would have to look something like this…

There is a part of me that wants to heap invective on Colin Sullivan and Scientific American, but I realize that while that may make me feel better, it will not help the situation.  So I will simply ask them, “Why don’t you show the actual historic data?”  It seems like a no-brainer, and anything less is journalistic malpractice.

Deniers and Alarmists

People like me have been branded with the “denier” epithet.  Why this particular word?  We are called “deniers” an ugly attempt to link us with Holocaust deniers.  It is an inaccurate and unfair moniker.

But we tend to call those at the other end of the spectrum “alarmists.”  Is that an unfair accusation?  I don’t think so, and this Scientific American article demonstrates why.  They pretend to be an objective source, but leave out the most pertinent data.  I can only think of two possible reasons for this: they are just stupid, or they want to cause a state of alarm.  I may be charitable in assigning the second motive.  “Alarmist” is an accurate and fair epithet for them.

Los Angeles underwater

March 24, 2011

There is good news and bad news coming out of California.  The bad news is that the Chicken Littles are clucking about sea level rise.  The good news is that at least some coastal communities are acting sensibly instead of panicking.

We live in trying times.  As our greatest minds peer into the future through their climate models we are only now beginning to understand the appalling fate that awaits us in an overheated, over-carbonized world.  Los Angeles is the latest city to be warned of its frightful destiny.

According to the Los Angeles Times

Sea levels have risen about 8 inches in the last century, and scientists expect them to rise several feet by the end of this century as climate change warms the ocean.

The hardest hit area of Los Angeles would be the Harbor/San Pedro/Long Beach region. As the LA Times notes, global seas rose by about 8 inches during the last century. Let’s see what impact this rise has had along the Harbor area of Los Angeles.  The following animation was made from a detail of a 1912 T. Newman map of Los Angeles county and from a 2011 Google Earth image.  The top half is photoshopped to clearly demarcate the land and water.

I can just hear the Chicken Littles clucking “Sure, the Los Angeles harbor region gained ground during the 20th century.  But that was with only 8 inches of sea level rise.  And everybody knows that the sea level rise rate along the california coast is rapidly increasing due to global warming.”

Not so fast, Mr Little.  Here is the relative sea level at Los Angeles for the last 85 years from the National Oceanic and Atmospheric Administration (NOAA).  Click to see the graph in context at the NOAA website.

Wait a minute, only 0.83 mm per year?  That’s only 83 mm (or 3.5 inches) per century.  And there is no acceleration that I can see.  It is kind of hard to believe there will be “several feet by the end of this century.”

What would be the consequences of “several feet [of sea level rise] by the end of this century?”  The bad news for Los Angeles and California was first revealed in the Pacific Institute’s  “The Impacts of Sea-Level Rise on the California Coast.”    They considered the devastation that will be wrought by a 1.4 meter (4.6 feet) sea level rise (based on the seminal work of Stefan Rahmstorf) during the 21st century.

The Pacific Institute created Hazard Maps of sections of  the California coast that would be inundated by a 100 year flood event with sea levels at their current level and with sea levels 1.4 meters higher.  I have stitched together several of those maps to show the region from the Los Angeles Harbor over to the Seal Beach area.  The light blue areas show the places that the Pacific institute figures would be inundated in a 100 year flood with year 2000 sea levels.  The dark blue areas show the places that they think would be flooded with the same 100 year event and an additional 1.4 meters of sea level.

But with the present, nearly steady, sea level rise rate the sea level will only go up by 0.083 meters (about 3.5 inches)  in 100 years.  Roughly speaking, if there is no acceleration in sea level rise rate near Los Angeles, then only about 6% of the dark blue areas would actually flood.

Sea level rise rates would have to increase unrealistically to get to an extras 1.4 meters in the 21st century.  We are 10 years into the century so far, and the sea level near Los Angeles has gone up only about 8 millimeters.  That leaves 1,392 millimeters to go in the next 90 years.  Here are a few hypothetical of sea level rise rate scenarios for the 21st century that would get us those 1392 millimeters…

These scenarios don’t look very promising, do they?  If we could somehow increase the sea level rise rate in Los Angeles harbor from its present value of 0.83 milimeters per year up to about 15 mm/year (a minor 18 fold increase) overnight, and keep it there for the next 90 years we could reach that target of 1.4 meters of sea level rise for the century.  Or we could try a linearly increasing sea level rise rate that gets to about 30 mm/year  by 2100.  That’s a whopping 36 fold increase from today’s rate by 2100.

Here’s the deal:  The sea level at Los Angeles has an acceleration 0.0019 mm/year/year.  Unless there is a gigantic increase in that rise rate, then the seas will rise by only about 12 cm in this century.  And there is zero indication that the sea level rise rate in Los Angeles has increased a whit in the last 85 years.

The good news

Although the Los Angeles Times article tries to impart a notion of acquiesence to the sea level rise scare by the “conservative city” of Newport Beach, they go on to say…

“…city planners are looking at raising seawalls by a foot or more to hold back the ocean.”

Wow, a whole one foot to protect from 1.4 meters (4.5 feet) of sea level rise.  Seems like the city planners in Newport Beach agree with my assesment more than with the 1.4 meter scare predicted by Mr. Rahmstorf.