You May Be Denying Climate Change, But The US Military Isn’t
Writing in the Pittsburgh Post-Gazette in a recent Op-Ed, Rear Adm. David Titley (Ret.) — who was initially a climate skeptic — worked on a Navy task force to study the issue, which he calls “an accelerating threat to national security.”
So we’d look at, for example, rising sea levels. This century, global sea levels are projected to rise several feet. Naval bases and installations around the world — along with the communities that support them — will be affected, and we need to plan for that.
Climate change affects military readiness, strains base resilience, creates missions in new regions of the world and increases the likelihood that our armed forces will be deployed for humanitarian missions. In many cases it also threatens our infrastructure and affects our economy. And our continued reliance on the fossil fuels whose consumption leads to climate change ties our nation’s hands on the world stage and tethers us to nations that do not always have our best interests at heart.
But you, keep going on denying it, people. Or you’d have to admit you’re wrong.
Click here for reuse options!Copyright 2014 Liberaland
By: William
retired military , former cop, lifelong gym rat and doting grandfather alive and living in Maine
25 responses to You May Be Denying Climate Change, But The US Military Isn’t
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mea_mark July 10th, 2014 at 15:54
I wonder how many people deny climate change just because they don’t want to admit they are wrong? It sure seems like a silly reason to continue to do damage to the environment that will effect humanity for so many more generations to come.
Tommy6860 July 10th, 2014 at 17:38
What you call being “wrong” is more “hubris”, and it is obvious to what political affiliation those deniers belong. The general ignorance that buys into the denier fantasy refuse to get beyond being the low information voter base.
Robert M. Snyder July 10th, 2014 at 19:20
I became concerned about “peak oil” at least a decade ago, and I have explained the concept to numerous friends and acquaintances. I strongly agree that we need to reduce our dependence on fossil fuels for reasons of sustainability and to increase energy independence.
I have a BS degree in Computer Science. I worked in a Biomechanics research lab for 5 years after graduating college. I have no special knowledge of climatology, but I do have some familiarity with how measurements are taken and analyzed. Those five years in the lab taught me that it is very difficult, and usually expensive, to acquire data that is free of artifacts.
I have read a lot of articles about climate change and sea level change. At this point I have to say that I just don’t know what to believe. Of course the climate is changing, and of course sea level is changing. But what are the magnitude and direction of the change?
I spent a couple of days trying to find out how sea level is measured. Until recently, sea level was measured almost exclusively using tide gauges located at various places around the world. Tide gauges are usually attached to piers. Of course, piers can and do experience movement from year to year. Scientists correct for these movements by placing typically ten benchmarks (fixed markers) at various points near the tide gauge. Each year, a surveyor visits the site and uses half of the benchmarks to determine the exact height of the tide gauge. The next year, the surveyor uses the other half of the benchmarks. Assuming the benchmarks do not move, scientists can use the survey data to determine the amount by which the pier has risen or fallen. This allows then to correct the raw data obtained from the tide gauge.
But there are problems with this system. In some cases, the benchmarks can move. One of the tide gauges is located on a pier at a US Naval Reserve Compound in Baltimore, very close to Fort McHenry. Here’s a web page describing the site:
http://tidesandcurrents.noaa.gov/stationhome.html?id=8574680
One of the benchmarks is a round brass plate that was epoxied to a horizontal concrete slab that is adjacent to the sea wall. Here are some photos of the benchmark that were taken by geocaching enthusiasts:
http://imgcdn.geocaching.com/benchmark/daec3854-c4c0-47f2-a0f8-9339c951bdaf.jpg
http://imgcdn.geocaching.com/benchmark/15609dd1-3a81-4397-a794-87aa7a2de4b8.jpg
http://imgcdn.geocaching.com/benchmark/84afc97c-eed8-4092-b879-d2ef3d76285a.jpg
It appears to me that the slab supporting this benchmark has experienced movement. Another one of the benchmarks is attached to the base of a large tower supporting a light. This is presumably more stable that teh concrete slab. But the best benchmarks are probably the ones created by driving a steel rod into the ground “to refusal”, meaning until it hits something very solid, typically 20 feet below the surface.
My point is that it is very difficult to obtain really good data. When we are measuring sea level rise in millimeters per year, we have to be very certain that our instruments are extremely well calibrated. Calibrating a tide gauge requires correcting for vertical movement of the pier.
You can find photos of tide gauges located in other locations, and in other countries. In many countries, the tide gauges are not as well constructed and maintained as they are in Western nations. Data coming from various countries is of varying quality.
But there are many other factors affecting the data quality. One big factor is sparseness. Before the advent of satellite technology, sea level was only measure along coastlines. That leaves wide expanses of ocean (2/3 of earth’s surface) for which we have virtually no historical data.
Many people wrongly assume that the ocean is like a big bathtub where the surface is perfectly flat and the “bathtub ring” is the same elevation everywhere. But this is simply not the case. Sea level varies from place to place, and from season to season at the same place. In some places, sea level is thought to be falling from year to year, while in other places it is thought to be rising from year to year.
Seasonal and long-term changes can be caused by changes in prevailing winds and ocean currents. And the apparent sea level measure by tide gauges can also be affected by vertical movement of the earth’s crust. Crustal movements can be on the same order of magnitude as estimated sea level changes (i.e. 2-3 mm/yr).
In a NASA press release dated July 7, 2005, Lynn Chandler of the Goddard Space Flight Center said “For the first time, NASA has the tools and expertise to understand the rate at which sea level is changing, some of the mechanisms that drive those changes and the effects that sea level change may have worldwide. Although scientists have directly measured sea level since the early part of the 20th century, it was not known how many of the observed changes in sea level were real and how many were related to upward or downward movement of the land.”
So the best available data, the satellite data, only covers the past ten years. Data from before 2005 indicates the apparent sea level at each tide gauge. But this data is not corrected for vertical movements of the earth’s crust.
Personally, I believe that it is wise to take seriously the possibility of global warming and sea level rise. But I think there is a lot of room for error in the data, so we have to be careful. I like solar and wind energy technology, and I ma happy to see that technology getting better and more affordable. I would like to see all countries gradually move away from fossil fuels.
I do not like being called a “denier” when I raise questions about the data. I honestly think that the data are ambiguous. I care about the planet. I try to conserve energy whenever I can. I’ve been recycling for decades. I avoid using perticides and herbicides in my garden and my lawn. I keep my tires inflated and avoid unnecessary trips. A lot of my neighbors do the same things. These all seem like common sense ways to reduce our personal footprints.
But if you’re asking me to accept as FACT the proposition that the global sea levels are rising, you’ve lost me. I just don’t think the data are good enough to support that conclusion, at least not yet.
Roctuna July 10th, 2014 at 21:26
At least you’re using your education (public?) to investigate an issue and try to have an informed opinion. The points you make about tidal stations and data are good ones. You pointed out the technique of using benchmarks and multiple measurements of relative sea level change. This statistical method is applied at each station and data is gathered from thousands of stations. This page at NOAA shows you in map view.
http://tidesandcurrents.noaa.gov/sltrends/
By taking mutiple measurements at each point a mean sea level is determined at that point and local trends can be determined such as this
http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8518750
or this
http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8665530
You are correct that satellite data has more accuracy and precision but the trends in the older data are strong. This is the latest technology to take advantage of GPS to make thousands of measurements per year automatically, which should make the tidal guage trends even more robust
http://www.chalmers.se/en/news/Pages/New-tide-gauge-uses-GPS-signals-to-measure-sea-level-change.aspx
Over geologic time, from the Pleistocene on back, we can identify and map ancient coastlines and determine sea level rise and fall with great precision. Factors such as tectonic uplift or subsidence, loss or gain of ocean volume due to cooling or heating of the water, gravitational forces of the moon and sun, and other factors are included in determining relative sea level trends. It’s not just one data set or even one type of data. I don’t know what to tell you other than as a geoscientist with some modest experience in this subject, global rise in average sea level is undisputed in the geoscience world. As some people would say, the force is strong in this one.
This NOAA site is just really cool to play with. Which coast area would you like to flood today? Use the viwer. Obe, you’ll love this.
http://www.csc.noaa.gov/digitalcoast/tools/slrviewer
Robert M. Snyder July 11th, 2014 at 03:16
Thank you for taking the time to give me such a thoughtful and informative reply. As someone who dabbles in robotics and sensors, I think the Chalmers approach is really neat.
It is my understanding that the satellites use radar to measure distance to the water. Time of flight of radio waves would be influenced by atmospheric effect such as clouds, humidity, and dust, right?
One thing that frustrates me is that I cannot seem to find any data on the precision and accuracy of these various types of instrumentation. How are the satellites calibrated, and what level of precision and accuracy can they achieve?
When a satellite passes over a mountain range, it will experience a greater gravitational force than when it passes over open water. That would tend to pull the satellite down to a slightly lower elevation. The satellite has mass, and there is no atmosphere to act as a damper, so any vertical movement is going to set up vertical oscillations of the satellite. Assuming the satellite passes over different land masses on each orbit, it would take some pretty complex calculations to determine the satellite’s instantaneous displacement from its own mean altitude.
The radar signal presumably has a known, fixed aperture. So each elevation reading represents a fixed-size region of the water’s surface. Suppose that on one day the water is placid, on a second day the water has 2 meter high swells, and on a third day it has cresting 5 meter high waves. Will the satellite obtain the same elevation reading on all three days?
I am sure that the scientists have explored all of these questions and many more. I am raising these issues because my experience in the lab, collecting real-time force and pressure data from human subjects during rapid movements, has taught me that it is very easy for systematic errors to creep into the data, in spite of rigorous attention to detail.
I am particularly skeptical of historical tide gauge readings. Tide gauges are located along shorelines. Every shoreline would become a hillside if the water level were lowered by twenty feet. Objects located on hillsides have a tendency to move downward over time, thanks to the unrelenting acceleration of gravity. Gravity always pulls in the same direction, so we cannot assume that the movements of tide gauges and benchmarks will be random.
Global sea level rise is estimated to be 2-3 mm/yr based largely upon historic data from tide gauges. Even if we rule out crustal movement, it is not difficult to imagine that tide gauges and their associated benchmarks might be sinking a couple of millimeters per year with respect to the center of the earth.
Coastline are constantly experiencing wave action, wind action, and erosion. In cold climates there is also frost wedging.
Has anyone ever looked at the relative, annual movement of the ten benchmarks that are typically associated with a given tide gauge? If these benchmarks are moving relative to one another, then they are not anchored to bedrock. And of course bedrock can move also. But if movement is occurring, the material that supports the tide gauge and benchmarks could be experiencing a very gradual slump.
Since gravity acts in the same direction everywhere on earth, this could cause a systematic error that looks like sea level rise, but is actually tide gauge and benchmark subsidence.
The satellite data and data from Chalmers-type systems calibrated by GPS should help to resolve this question. But I still don’t trust the historical tide gauge data.
I would really like to see a comparison of currently obtained readings from the various types of instrumentation systems. If conventional tide gauge data, GPS-corrected tide gauge data, and satellite date were all collected separately by independent observers with no knowledge of each other’s findings, and then compared, would all three systems produce the same results? I strongly suspect that the conventional tide gauges would show greater sea level rise than the other two systems, because of the factors I described above.
I am always open to learning. If you know of any websites or publications that might give me a better understanding of the precision and accuracy of these instrumentation systems, please send me links.
Thanks.
Roctuna July 11th, 2014 at 09:02
You’re welcome. The ranters gotta rant and the haters gotta hate and when they post on this site, their minds are already closed. It’s fun to point out their ignorance, yank their chains a little bit and move on. When someone wants to discuss a subject, that’s refreshing.
You’re asking a lot of questions way out of my area of expertise. I do know that radar frequencies can be tuned to be unaffected by atmospherics. I’m sure there’s more to it than that. I would suggest you dig deeper at NOAA about how they gather and analyze data. As for the satellites, try NASA, JPL (they handle all robotic missions), the European Space Agency, Popular Astrophysics? I do know this page also has links that might be helpful to you
http://www.usno.navy.mil/
Back to sea level. I think you’re operating under a few misconceptions. Geoscientists don’t “rule out” things like local or tectonic movement (up or down), thermal expansion/contraction of the water, etc. they factor it in. The statistical approach of collecting large volumes of data to calculate the mean is exactly how things like weathering, erosion, and localized changes are accommodated. All of that’s in the error bar that shows the range of variation. There are large bodies of data available to determine the impact of those factors. I suspect the comparative studies you’re looking for have been done and I’ll surmise the trends agree. The tidal gauge data will have a wider “error bar”. I leave it to you to find those studies.
Coastlines are not flooded hillsides. The Atlantic coast of the US dips into the ocean at about one quarter to one half a degree of slope. That’s about 25-50 feet per mile. The Pacific coast is a bit steeper, about 3-4 degrees, sometimes a bit more. There are many areas where the shoreline is steeper, but not in the US. Sea level was as much as 450 feet or so lower in the Pleistocene when so much water was taken up in ice on the continents. As the polar ice sheets have melted, especially in the northern hemisphere, sea level has risen because there’s more runoff into the ocean basins, plus melting glaciers and bergs. Also as the atmosphere warms (I hear that’s controversial) some of that heat is transferred to the ocean causing thermal expansion. All of that combined puts us in what geologists call a transgressive cycle, meaning shorelines are migrating landward. We’ve been in one since the retreat of the big glaciers but the rate of transgression has been accelerating in the last century.
Last link is a very up to date treatment of the coastal systems in the Carolinas and the effect of rising sea level. These concepts can be applied with some modification along most of the Gulf Coast and Atlantic Coast. Good luck in your researches.
http://www.geology.ecu.edu/NCCoastsinCrisis.pdf
mel897 July 16th, 2014 at 15:17
“I have no special knowledge of climatology” I think this is germaine Robert. One can obtain a degree in computer science without actually knowing a lot about science… it’s my specialty too. However, I have enough faith in the process that when the vast majority of scientists who actually do have expertise in the field support a finding, we ignore it at our peril.
Robert M. Snyder July 16th, 2014 at 15:51
The more I learn about the science, the more questions I have. Over the weekend, a few of us were discussing how satellites measure sea level. None of us had any idea how high the satellites are located above the earth. So this morning I did some research.
From what I can gather, the newest satellites capable of measuring sea level are Jason-1 and Jason-2, launched in 2001 and 2008, respectively. They are located 1,336 kilometers (1.336 billion millimeters) above the earth.
Using data from these satellites, scientists estimate that global mean sea level is rising by 2.28 millimeters per year. Measuring a one millimeter in a 1.336 billion millimeter distance requires an accuracy better than one part per billion.
Analogy: Two reams (1000 sheets) of copier paper are about 4 inches tall. A stack of paper containing a million sheets would be 333 feet tall. A billion sheets would be 63 miles tall. If I told you that I had an instrument that could measure the height of the stack (63 miles) so accurately that it could detect the removal of a single sheet of paper, wouldn’t you be just a little bit skeptical?
Jason-2 uses RADAR to measure the distance. RADAR is affected by water vapor and liquid water in the atmosphere. Another instrument onboard the satellite measures atmospheric moisture so that the RADAR data can be corrected. The satellite’s position is influenced by the moon’s gravity as well as the earth’s non-uniform gravitational field. (Gravity is stronger above mountain ranges). The atmosphere is very thin at 1336 km, but it still causes drag, so the engineers occasionally fire booster rockets to restore the satellite’s altitude. Also, the earth is not a perfect sphere. It is wider at the equator.
So as you can see, there are many factors which can affect the accuracy of the satellite altimeter data. I have great respect for the engineers and scientists who design and operate these systems. But I am more than a little skeptical about whether they can accurately measure sea level with millimeter precision.
The CNES website says “Radio waves transmitted and received by an altimeter do not travel in a vacuum. Signals passing through Earth’s atmosphere may be subjected to path delays, thus introducing errors into measurements. For example, large amounts of electrons at altitudes near 400 km, dry air and water vapour all generate errors ranging from a few centimetres to more than 2 metres. To achieve the extreme level of accuracy required, we have to identify the source of these perturbations and then calculate the necessary corrections. Special instruments on board the satellite are designed to measure physical parameters for this purpose. After corrections, the satellite-to-ocean range can be estimated with an accuracy of 2 centimetres. Since the aim is to estimate sea level precisely with respect to a terrestrial reference, measurements must also be independent of the satellite. For this reason, we need to know the satellite’s exact orbital position. Since the altimeter only measures the range from the satellite to the sea surface, called R, we have to calculate the sea-surface height with respect to a terrestrial reference (see diagram). To do this, we must first define an arbitrary reference surface. Since the sea depth is not known accurately everywhere, we use a regular, imaginary surface that is a raw approximation of the shape of the Earth, which is a sphere flattened at the poles. This surface is called the reference ellipsoid, which allows us to calibrate data precisely and uniformly. The satellite’s altitude with respect to the reference ellipsoid, called S, is calculated with an accuracy of 3 cm using the satellite’s orbital parameters and precise positioning instruments”
So it would appear that there is an uncertainty of 3 cm in the altitude of the satellite, and 2 cm in the distance from satellite to sea surface. This equals a worst-case error of 5 cm.
But Jason-1 was launched in 2001, so we have only 13 years’ worth of data. The estimated sea level rise of 2.28 mm/yr would mean 3 cm of rise in 13 years. So the estimated rise over the 13 year period is less than the margin of error in the measurements.
Random measurement error can be reduced by taking lots of measurements and averaging. But this does not reduce systematic error. For example, if the satellite’s altitude is off by 2 cm, then every measurement taken by the satellite will be off by 2 cm, and averaging will not change the result.
I am not saying that the satellite data is a sham. I think the technology is amazing and the data are already changing our understanding of ocean dynamics.
I am simply questioning whether the altimetry data are sufficiently accurate to confirm or refute the proposition that global mean sea level is rising.
http://www.cnes.fr/web/CNES-en/1091-altitude-and-sea-surface-height.php
http://www.cnes.fr/web/CNES-en/1092-correcting-to-improve-accuracy.php
mea_mark July 10th, 2014 at 15:54
I wonder how many people deny climate change just because they don’t want to admit they are wrong? It sure seems like a silly reason to continue to do damage to the environment that will effect humanity for so many more generations to come.
mea_mark July 10th, 2014 at 15:54
I wonder how many people deny climate change just because they don’t want to admit they are wrong? It sure seems like a silly reason to continue to do damage to the environment that will effect humanity for so many more generations to come.
Tommy6860 July 10th, 2014 at 17:38
What you call being “wrong” is more “hubris”, and it is obvious to what political affiliation those deniers belong. The general ignorance that buys into the denier fantasy refuse to get beyond being the low information voter base.
Robert M. Snyder July 10th, 2014 at 19:20
I became concerned about “peak oil” at least a decade ago, and I have explained the concept to numerous friends and acquaintances. I strongly agree that we need to reduce our dependence on fossil fuels for reasons of sustainability and to increase energy independence.
I have a BS degree in Computer Science. I worked in a Biomechanics research lab for 5 years after graduating college. I have no special knowledge of climatology, but I do have some familiarity with how measurements are taken and analyzed. Those five years in the lab taught me that it is very difficult, and usually expensive, to acquire data that is free of artifacts.
I have read a lot of articles about climate change and sea level change. At this point I have to say that I just don’t know what to believe. Of course the climate is changing, and of course sea level is changing. But what are the magnitude and direction of the change?
I spent a couple of days trying to find out how sea level is measured. Until recently, sea level was measured almost exclusively using tide gauges located at various places around the world. Tide gauges are usually attached to piers. Of course, piers can and do experience movement from year to year. Scientists correct for these movements by placing typically ten benchmarks (fixed markers) at various points near the tide gauge. Each year, a surveyor visits the site and uses half of the benchmarks to determine the exact height of the tide gauge. The next year, the surveyor uses the other half of the benchmarks. Assuming the benchmarks do not move, scientists can use the survey data to determine the amount by which the pier has risen or fallen. This allows then to correct the raw data obtained from the tide gauge.
But there are problems with this system. In some cases, the benchmarks can move. One of the tide gauges is located on a pier at a US Naval Reserve Compound in Baltimore, very close to Fort McHenry. Here’s a web page describing the site:
http://tidesandcurrents.noaa.gov/stationhome.html?id=8574680
One of the benchmarks is a round brass plate that was epoxied to a horizontal concrete slab that is adjacent to the sea wall. Here are some photos of the benchmark that were taken by geocaching enthusiasts:
http://imgcdn.geocaching.com/benchmark/daec3854-c4c0-47f2-a0f8-9339c951bdaf.jpg
http://imgcdn.geocaching.com/benchmark/15609dd1-3a81-4397-a794-87aa7a2de4b8.jpg
http://imgcdn.geocaching.com/benchmark/84afc97c-eed8-4092-b879-d2ef3d76285a.jpg
It appears to me that the slab supporting this benchmark has experienced movement. Another one of the benchmarks is attached to the base of a large tower supporting a light. This is presumably more stable that teh concrete slab. But the best benchmarks are probably the ones created by driving a steel rod into the ground “to refusal”, meaning until it hits something very solid, typically 20 feet below the surface.
My point is that it is very difficult to obtain really good data. When we are measuring sea level rise in millimeters per year, we have to be very certain that our instruments are extremely well calibrated. Calibrating a tide gauge requires correcting for vertical movement of the pier.
You can find photos of tide gauges located in other locations, and in other countries. In many countries, the tide gauges are not as well constructed and maintained as they are in Western nations. Data coming from various countries is of varying quality.
But there are many other factors affecting the data quality. One big factor is sparseness. Before the advent of satellite technology, sea level was only measure along coastlines. That leaves wide expanses of ocean (2/3 of earth’s surface) for which we have virtually no historical data.
Many people wrongly assume that the ocean is like a big bathtub where the surface is perfectly flat and the “bathtub ring” is the same elevation everywhere. But this is simply not the case. Sea level varies from place to place, and from season to season at the same place. In some places, sea level is thought to be falling from year to year, while in other places it is thought to be rising from year to year.
Seasonal and long-term changes can be caused by changes in prevailing winds and ocean currents. And the apparent sea level measure by tide gauges can also be affected by vertical movement of the earth’s crust. Crustal movements can be on the same order of magnitude as estimated sea level changes (i.e. 2-3 mm/yr).
In a NASA press release dated July 7, 2005, Lynn Chandler of the Goddard Space Flight Center said “For the first time, NASA has the tools and expertise to understand the rate at which sea level is changing, some of the mechanisms that drive those changes and the effects that sea level change may have worldwide. Although scientists have directly measured sea level since the early part of the 20th century, it was not known how many of the observed changes in sea level were real and how many were related to upward or downward movement of the land.”
So the best available data, the satellite data, only covers the past ten years. Data from before 2005 indicates the apparent sea level at each tide gauge. But this data is not corrected for vertical movements of the earth’s crust.
Personally, I believe that it is wise to take seriously the possibility of global warming and sea level rise. But I think there is a lot of room for error in the data, so we have to be careful. I like solar and wind energy technology, and I ma happy to see that technology getting better and more affordable. I would like to see all countries gradually move away from fossil fuels.
I do not like being called a “denier” when I raise questions about the data. I honestly think that the data are ambiguous. I care about the planet. I try to conserve energy whenever I can. I’ve been recycling for decades. I avoid using perticides and herbicides in my garden and my lawn. I keep my tires inflated and avoid unnecessary trips. A lot of my neighbors do the same things. These all seem like common sense ways to reduce our personal footprints.
But if you’re asking me to accept as FACT the proposition that the global sea levels are rising, you’ve lost me. I just don’t think the data are good enough to support that conclusion, at least not yet.
Roctuna July 10th, 2014 at 21:26
At least you’re using your education (public?) to investigate an issue and try to have an informed opinion. The points you make about tidal stations and data are good ones. You pointed out the technique of using benchmarks and multiple measurements of relative sea level change. This statistical method is applied at each station and data is gathered from thousands of stations. This page at NOAA shows you in map view.
http://tidesandcurrents.noaa.gov/sltrends/
By taking mutiple measurements at each point a mean sea level is determined at that point and local trends can be determined such as this
http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8518750
or this
http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8665530
You are correct that satellite data has more accuracy and precision but the trends in the older data are strong. This is the latest technology to take advantage of GPS to make thousands of measurements per year automatically, which should make the tidal guage trends even more robust
http://www.chalmers.se/en/news/Pages/New-tide-gauge-uses-GPS-signals-to-measure-sea-level-change.aspx
Over geologic time, from the Pleistocene on back, we can identify and map ancient coastlines and determine sea level rise and fall with great precision. Factors such as tectonic uplift or subsidence, loss or gain of ocean volume due to cooling or heating of the water, gravitational forces of the moon and sun, and other factors are included in determining relative sea level trends. It’s not just one data set or even one type of data. I don’t know what to tell you other than as a geoscientist with some modest experience in this subject, global rise in average sea level is undisputed in the geoscience world. As some people would say, the force is strong in this one.
This NOAA site is just really cool to play with. Which coast area would you like to flood today? Use the viwer. Obe, you’ll love this.
http://www.csc.noaa.gov/digitalcoast/tools/slrviewer
Robert M. Snyder July 11th, 2014 at 03:16
Thank you for taking the time to give me such a thoughtful and informative reply. As someone who dabbles in robotics and sensors, I think the Chalmers approach is really neat.
It is my understanding that the satellites use radar to measure distance to the water. Time of flight of radio waves would be influenced by atmospheric effect such as clouds, humidity, and dust, right?
One thing that frustrates me is that I cannot seem to find any data on the precision and accuracy of these various types of instrumentation. How are the satellites calibrated, and what level of precision and accuracy can they achieve?
When a satellite passes over a mountain range, it will experience a greater gravitational force than when it passes over open water. That would tend to pull the satellite down to a slightly lower elevation. The satellite has mass, and there is no atmosphere to act as a damper, so any vertical movement is going to set up vertical oscillations of the satellite. Assuming the satellite passes over different land masses on each orbit, it would take some pretty complex calculations to determine the satellite’s instantaneous displacement from its own mean altitude.
The radar signal presumably has a known, fixed aperture. So each elevation reading represents a fixed-size region of the water’s surface. Suppose that on one day the water is placid, on a second day the water has 2 meter high swells, and on a third day it has cresting 5 meter high waves. Will the satellite obtain the same elevation reading on all three days?
I am sure that the scientists have explored all of these questions and many more. I am raising these issues because my experience in the lab, collecting real-time force and pressure data from human subjects during rapid movements, has taught me that it is very easy for systematic errors to creep into the data, in spite of rigorous attention to detail.
I am particularly skeptical of historical tide gauge readings. Tide gauges are located along shorelines. Every shoreline would become a hillside if the water level were lowered by twenty feet. Objects located on hillsides have a tendency to move downward over time, thanks to the unrelenting acceleration of gravity. Gravity always pulls in the same direction, so we cannot assume that the movements of tide gauges and benchmarks will be random.
Global sea level rise is estimated to be 2-3 mm/yr based largely upon historic data from tide gauges. Even if we rule out crustal movement, it is not difficult to imagine that tide gauges and their associated benchmarks might be sinking a couple of millimeters per year with respect to the center of the earth.
Coastlines are constantly experiencing wave action, wind action, and erosion. In cold climates there is also frost wedging.
Has anyone ever looked at the relative, annual movement of the ten benchmarks that are typically associated with a given tide gauge? If these benchmarks are moving relative to one another, then they are not anchored to bedrock. And of course bedrock can move also. But if movement is occurring, the material that supports the tide gauge and benchmarks could be experiencing a very gradual slump.
Since gravity acts in the same direction everywhere on earth, this could cause a systematic error that looks like sea level rise, but is actually tide gauge and benchmark subsidence.
The satellite data and data from Chalmers-type systems calibrated by GPS should help to resolve this question. But I still don’t trust the historical tide gauge data.
I would really like to see a comparison of currently obtained readings from the various types of instrumentation systems. If conventional tide gauge data, GPS-corrected tide gauge data, and satellite date were all collected separately by independent observers with no knowledge of each other’s findings, and then compared, would all three systems produce the same results? I strongly suspect that the conventional tide gauges would show greater sea level rise than the other two systems, because of the factors I described above.
I am always open to learning. If you know of any websites or publications that might give me a better understanding of the precision and accuracy of these instrumentation systems, please send me links.
Thanks.
Roctuna July 11th, 2014 at 09:02
You’re welcome. The ranters gotta rant and the haters gotta hate and when they post on this site, their minds are already closed. It’s fun to point out their ignorance, yank their chains a little bit and move on. When someone wants to discuss a subject, that’s refreshing.
You’re asking a lot of questions way out of my area of expertise. I do know that radar frequencies can be tuned to be unaffected by atmospherics. I’m sure there’s more to it than that. I would suggest you dig deeper at NOAA about how they gather and analyze data. As for the satellites, try NASA, JPL (they handle all robotic missions), the European Space Agency, Popular Astrophysics? I do know this page also has links that might be helpful to you
http://www.usno.navy.mil/
Back to sea level. I think you’re operating under a few misconceptions. Geoscientists don’t “rule out” things like local or tectonic movement (up or down), thermal expansion/contraction of the water, etc. they factor it in. The statistical approach of collecting large volumes of data to calculate the mean is exactly how things like weathering, erosion, and localized changes are accommodated. All of that’s in the error bar that shows the range of variation. There are large bodies of data available to determine the impact of those factors. I suspect the comparative studies you’re looking for have been done and I’ll surmise the trends agree. The tidal gauge data will have a wider “error bar”. I leave it to you to find those studies.
Coastlines are not flooded hillsides. The Atlantic coast of the US dips into the ocean at about one quarter to one half a degree of slope. That’s about 25-50 feet per mile. The Pacific coast is a bit steeper, about 3-4 degrees, sometimes a bit more. There are many areas where the shoreline is steeper, but not in the US. Sea level was as much as 450 feet or so lower in the Pleistocene when so much water was taken up in ice on the continents. As the polar ice sheets have melted, especially in the northern hemisphere, sea level has risen because there’s more runoff into the ocean basins, plus melting glaciers and bergs. Also as the atmosphere warms (I hear that’s controversial) some of that heat is transferred to the ocean causing thermal expansion. All of that combined puts us in what geologists call a transgressive cycle, meaning shorelines are migrating landward. We’ve been in one since the retreat of the big glaciers but the rate of transgression has been accelerating in the last century.
Last link is a very up to date treatment of the coastal systems in the Carolinas and the effect of rising sea level. These concepts can be applied with some modification along most of the Gulf Coast and Atlantic Coast. Good luck in your researches.
http://www.geology.ecu.edu/NCCoastsinCrisis.pdf
mel897 July 16th, 2014 at 15:17
“I have no special knowledge of climatology” I think this is germaine Robert. One can obtain a degree in computer science without actually knowing a lot about science… it’s my specialty too. However, I have enough faith in the process that when the vast majority of scientists who actually do have expertise in the field support a finding, we ignore it at our peril.
Robert M. Snyder July 16th, 2014 at 15:51
The more I learn about the science, the more questions I have. Over the weekend, a few of us were discussing how satellites measure sea level. None of us had any idea how high the satellites are located above the earth. So this morning I did some research.
From what I can gather, the newest satellites capable of measuring sea level are Jason-1 and Jason-2, launched in 2001 and 2008, respectively. They are located 1,336 kilometers (1.336 billion millimeters) above the earth.
Using data from these satellites, scientists estimate that global mean sea level is rising by 2.28 millimeters per year. Measuring a one millimeter in a 1.336 billion millimeter distance requires an accuracy better than one part per billion.
Analogy: Two reams (1000 sheets) of copier paper are about 4 inches tall. A stack of paper containing a million sheets would be 333 feet tall. A billion sheets would be 63 miles tall. If I told you that I had an instrument that could measure the height of the stack (63 miles) so accurately that it could detect the removal of a single sheet of paper, wouldn’t you be just a little bit skeptical?
Jason-2 uses RADAR to measure the distance. RADAR is affected by water vapor and liquid water in the atmosphere. Another instrument onboard the satellite measures atmospheric moisture so that the RADAR data can be corrected. The satellite’s position is influenced by the moon’s gravity as well as the earth’s non-uniform gravitational field. (Gravity is stronger above mountain ranges). The atmosphere is very thin at 1336 km, but it still causes drag, so the engineers occasionally fire booster rockets to restore the satellite’s altitude. Also, the earth is not a perfect sphere. It is wider at the equator.
So as you can see, there are many factors which can affect the accuracy of the satellite altimeter data. I have great respect for the engineers and scientists who design and operate these systems. But I am more than a little skeptical about whether they can accurately measure sea level with millimeter precision.
The CNES website says “Radio waves transmitted and received by an altimeter do not travel in a vacuum. Signals passing through Earth’s atmosphere may be subjected to path delays, thus introducing errors into measurements. For example, large amounts of electrons at altitudes near 400 km, dry air and water vapour all generate errors ranging from a few centimetres to more than 2 metres. To achieve the extreme level of accuracy required, we have to identify the source of these perturbations and then calculate the necessary corrections. Special instruments on board the satellite are designed to measure physical parameters for this purpose. After corrections, the satellite-to-ocean range can be estimated with an accuracy of 2 centimetres. Since the aim is to estimate sea level precisely with respect to a terrestrial reference, measurements must also be independent of the satellite. For this reason, we need to know the satellite’s exact orbital position. Since the altimeter only measures the range from the satellite to the sea surface, called R, we have to calculate the sea-surface height with respect to a terrestrial reference (see diagram). To do this, we must first define an arbitrary reference surface. Since the sea depth is not known accurately everywhere, we use a regular, imaginary surface that is a raw approximation of the shape of the Earth, which is a sphere flattened at the poles. This surface is called the reference ellipsoid, which allows us to calibrate data precisely and uniformly. The satellite’s altitude with respect to the reference ellipsoid, called S, is calculated with an accuracy of 3 cm using the satellite’s orbital parameters and precise positioning instruments”
So it would appear that there is an uncertainty of 3 cm in the altitude of the satellite, and 2 cm in the distance from satellite to sea surface. This equals a worst-case error of 5 cm.
But Jason-1 was launched in 2001, so we have only 13 years’ worth of data. The estimated sea level rise of 2.28 mm/yr would mean 3 cm of rise in 13 years. So the estimated rise over the 13 year period is less than the margin of error in the measurements.
Random measurement error can be reduced by taking lots of measurements and averaging. But this does not reduce systematic error. For example, if the satellite’s altitude is off by 2 cm, then every measurement taken by the satellite will be off by 2 cm, and averaging will not change the result.
I am not saying that the satellite data is a sham. I think the technology is amazing and the data are already changing our understanding of ocean dynamics.
I am simply questioning whether the altimetry data are sufficiently accurate to confirm or refute the proposition that global mean sea level is rising.
http://www.cnes.fr/web/CNES-en/1091-altitude-and-sea-surface-height.php
http://www.cnes.fr/web/CNES-en/1092-correcting-to-improve-accuracy.php
KABoink_after_wingnut_hacker July 10th, 2014 at 16:22
Not only is the military taking climate change seriously, the insurance companies of the entire world are taking it very, very seriously. They have stopped issuing hurricane and flood insurance in many areas globally.
Conservatives forget that their success is based on having an ignorant and ill-informed base. Anyone who looks around the world at other nations knows this and it’s an embarrassment to all Americans when the world looks at the GOP buffoons.
KABoink_after_wingnut_hacker July 10th, 2014 at 16:22
Not only is the military taking climate change seriously, the insurance companies of the entire world are taking it very, very seriously. They have stopped issuing hurricane and flood insurance in many areas globally.
Conservatives forget that their success is based on having an ignorant and ill-informed base. Anyone who looks around the world at other nations knows this and it’s an embarrassment to all Americans when the world looks at the GOP buffoons.
mel897 July 16th, 2014 at 15:09
I work for an Reinsurance company that underwrites catastrophe insurance. You are exactly right. It was the main topic at our last actuarial conference.
KABoink_after_wingnut_hacker July 10th, 2014 at 16:22
Not only is the military taking climate change seriously, the insurance companies of the entire world are taking it very, very seriously. They have stopped issuing hurricane and flood insurance in many areas globally.
Conservatives forget that their success is based on having an ignorant and ill-informed base. Anyone who looks around the world at other nations knows this and it’s an embarrassment to all Americans when the world looks at the GOP buffoons.
KABoink_after_wingnut_hacker July 10th, 2014 at 16:22
Not only is the military taking climate change seriously, the insurance companies of the entire world are taking it very, very seriously. They have stopped issuing hurricane and flood insurance in many areas globally.
Conservatives forget that their success is based on having an ignorant and ill-informed base. Anyone who looks around the world at other nations knows this and it’s an embarrassment to all Americans when the world looks at the GOP buffoons.
KABoink_after_wingnut_hacker July 10th, 2014 at 16:22
Not only is the military taking climate change seriously, the insurance companies of the entire world are taking it very, very seriously. They have stopped issuing hurricane and flood insurance in many areas globally.
Conservatives forget that their success is based on having an ignorant and ill-informed base. Anyone who looks around the world at other nations knows this and it’s an embarrassment to all Americans when the world looks at the GOP buffoons.
KABoink_after_wingnut_hacker July 10th, 2014 at 16:22
Not only is the military taking climate change seriously, the insurance companies of the entire world are taking it very, very seriously. They have stopped issuing hurricane and flood insurance in many areas globally.
Conservatives forget that their success is based on having an ignorant and ill-informed base. Anyone who looks around the world at other nations knows this and it’s an embarrassment to all Americans when the world looks at GOP buffoons as representative of our nation.
mel897 July 16th, 2014 at 15:09
I work for an Reinsurance company that underwrites catastrophe insurance. You are exactly right. It was the main topic at our last actuarial conference.