Munging The Sea Level Data

Guest Post by Willis Eschenbach
(Note: In 2025 I revisited this issue in a post here. Same conclusion.

mung
/mənj/ [pronounced “munge”]
verb
INFORMAL•COMPUTING
gerund or present participle: munging
to manipulate (data)
EXAMPLE: “you could do what anti-spammers have done for years and mung the URLs”

For more than a decade now, I’ve been wondering about a couple of questions.

First, why does the satellite-based sea-level data show that the sea level is rising so much faster than the rise measured at tidal stations on the coastlines around the world? Records from tidal stations show a rise on the order of a couple of mm per year, a rate which is little changed over the century or so for which we have adequate records. But the satellite record (Figure 1) shows a rise of 3.3 mm/year. Why the large difference?

Second, why does the satellite-based sea-level show such significant acceleration? As mentioned above, the sea-level records from tidal stations, which are much longer, show little or no acceleration. But the satellite record claims that the rate of sea-level rise is increasing by about a tenth of a millimeter per year. That amount of acceleration would double the rate of sea-level rise in about thirty years. Again, why the large difference?

To start with, here’s what the satellite data says, according to the University of Colorado Sea Level Research Group.

Figure 1. University of Colorado sea level data, showing the trend and acceleration. Note that the graph shows no overlap between the individual satellite records. SOURCE: UCSLR Group

I got to thinking about these questions again this week, so I went to NOAA and got their Excel spreadsheet showing the full dataset for each of the four satellites.

I plotted up the NOAA data. But unlike the Colorado data above, I included the full overlap between the individual satellites. I then looked at the rate of sea-level rise shown by each of the four satellites separately. Figure 2 shows that result.

Figure 2. NOAA sea level data, showing the trend of each of the full individual satellite records and the overall trend. SOURCE: NOAA Excel Spreadsheet

Well, go figure … seems like after all these many years of wondering, I finally have an answer to my two questions. The trend is so large and the acceleration is so great for a simple reason. The two most recent satellites show trends that are significantly larger than the earlier two satellites. The first two satellites agree quite well, but they both show a much smaller trend than the latter two satellites. And neither half of the satellite record shows any acceleration.

Now I freely admit, I’m just a guy with no scientific training at all. I took Physics 101, Chemistry 101, and one year of Calculus in college, and that’s it. But the beauty of science is that it’s all about the facts and the evidence, and not about the qualifications of the person presenting the facts. What you see above are the facts as given by NOAA, and I’ve linked to the source of those facts above. And it seems to me that those facts are more than sufficient to entirely discredit the satellite sea-level record.

So if you have an explanation for those facts, fine. But don’t bother busting me because you think I’m not qualified to present and discuss the facts. “The Captain”, my great-grandfather who was a Mississippi riverboat captain, used to say “If you have to hang your diploma on your living room wall, there was something wrong with your education”.

And to return to the issues at hand, why does the NOAA data show an overall trend which is 0.3 mm per year smaller than the Colorado data? It’s because the Colorado data contains what is called the “GIA”, and the NOAA data doesn’t.

“GIA” stands for the “glacial isostatic adjustment”. There’s a description of it on the Colorado site here. It relates to the changes in the earth’s overall shape due to the melting of the huge and immensely heavy ice sheets from the last glaciation.

According to that page, the GIA is “independently estimated from models at -0.3 mm/yr (Peltier, 2001, 2002, 2009; Peltier & Luthcke, 2009)”.

Now, I’ve been programming computers since 1963, coming up on 60 years now. As a result, I’m very aware that a computer model is nothing more than a physical realization of the beliefs, understandings, and in particular the misunderstandings of the person programming the computer. Since Mr. Peltier has been intimately involved in programming all four of the model realizations listed on the Colorado site, their claim that the four models are “independent” is laughable. What we have is one man’s claim that he can calculate the GIA.

What effect does the GIA have? The Colorado site says (emphasis mine):

Prior to release 2011_rel1, we did not account for GIA in estimates of the global mean sea level rate, but this correction is now scientifically well-understood and is applied to GMSL estimates by nearly all research groups around the world. Including the GIA correction has the effect of increasing previous estimates of the global mean sea level rate by 0.3 mm/yr.

So there’s the missing 0.3 mm/year, applied by “nearly all research groups” … I guess NOAA didn’t get the memo.

For me, the claim that a computer model can calculate the changing of the total volumes of all of the world’s various ocean basins to the nearest 0.3 mm per year of sea level … well, let me just say that it strains credulity far beyond the breaking point and leave it at that. Here’s why.

For the land portion of the calculation, these “independent” computer models must be using GPS altitudes. By using split-phase GPS and repeated measurements, these can be as accurate as ± 10 mm or better, an amazing scientific feat … but that’s a far cry from a tenth of a millimetre, and that’s just on land. Not only that, but we don’t have GPS measurements all over the land. They’re concentrated in the US and Europe, with only spotty coverage elsewhere.

At sea, the “independent” models must be using satellite measurements, so we get into the question of the accuracy and precision of the satellite sea level measurements themselves. These measurements are done by bouncing radar waves off of the ocean surface and measuring how long it takes them to return to the satellite. Here, repeated measurements are not possible because the sea level at any point changes constantly, and the satellite is rarely in the same position twice. A recent NASA press release describing the Sentinel-6 satellite, the successor to the Jason-3 satellite, quotes the oceanographer Josh Willis:

Sentinel-6 will orbit about 800 miles up and use radar to measure the surface of the ocean. An instrument on the satellite sends a radar wave down to Earth. The radar bounces off the surface of the ocean and returns to the satellite. By measuring how long it took for the radar to go down and back — and accounting for moisture in the atmosphere which slows the radar down — scientists can measure how far away the surface of the ocean is from the satellite.

In other words, the satellite can tell scientists on Earth how high the oceans are, and how that height is changing over time.

“It’s really kind of an incredible feat of technology,” [Josh] Willis says. “We can accurately measure the water level with an accuracy of 1 inch from 800 miles up.”

An accuracy of 1 inch, that’s 25.4 mm … and they’re claiming they know the annual change in the volume of the oceans from the GIA to the nearest tenth of an mm of sea level height? I know that accuracy is different from precision, and that measurement of changes in length over time (precision) can be an order of magnitude better than the measurements of the length itself (accuracy), but still … sorry, but I’m not buying the GIA claim.

Let me see if I can give you a sense of the difficulty of the satellite measurements of sea level. The satellites orbit at an altitude of about 830 miles, which is about 1.34 billion millimetres. So to measure the change in sea level to the nearest tenth of an mm, we’d need to be able to measure the distance from the satellite to the sea surface to a precision greater than one part in thirteen billion … and that is a hard challenge even in a controlled laboratory setting.

Here are some of the difficulties in that measurement. First is the measurement of the altitude of the satellite itself. Unless we know that to the nearest mm or so for every second of every day, we’re going to get inaccurate answers. Next is the varying composition, temperature, cloudiness, and humidity of the atmosphere. All of these change the time it takes the radar signal to return to the satellite. Then there are the ocean waves, which obviously change the height of the ocean by thousands of mm. Finally, there is “instrument drift”, the inevitable changes that occur to electronic measuring instruments over time.

Net result? Well, the net result can be seen in Figure 2 above, where according to the University of Colorado one satellite says the sea level is rising at 2.5 mm/year, and a mere 8 days after the end of that satellite’s data (the interval between one satellite and the next in the Colorado sea-level record) the successor satellite says it is rising at 4.1 mm/year … no bueno. They’re claiming that in 8 days, the rate of rise jumped by 1.6 mm per year. Note also that there is absolutely no acceleration in either half of the satellite record, just a step-change between satellites. Clearly, they’re not able to measure annual sea-level changes to the nearest millimetre, much less to the nearest tenth of a millimetre.

However, the people working on the project are all true believers. In the same article, Josh Willis is quoted as saying “We know that the oceans are rising because of human-caused interference with the climate.”

Dang humans, always interfering with the climate … for example, our new “Climate Czar”, John Kerry, has 5 houses, a number of cars, a yacht, and a private jet, and he tells us to take the bus to avoid the dreaded “human-caused interference with the climate” … but I digress.

The problem is that starting out with a fixed “scientific” belief like that leads to the people working on the satellite sea-level datasets splicing together what are obviously incompatible satellite results, spreading peanut butter over the cracks so they can’t be seen, and announcing to the world that the satellites show a dangerous acceleration in sea-level rise, so we should all be very worried …

Me, I’ve said for some time that we shouldn’t put any weight on the satellite results. However, I have based this solely on the very large differences in both trend and acceleration between the satellite and the tidal station records, and the known difficulties in satellite measurements discussed above. I investigated this question in several posts, including “Inside The Acceleration Factory” and “Accelerating The Acceleration“

But now, at long last, I have the facts to back up my claim. There’s no evidence of any acceleration in the rate of sea-level rise in either the tide gauge or the shabbily-spliced satellite records. It’s been going up at on the order of eight inches (200 mm) per century for quite some time, and there’s no sign of any change in that rate of rise.

So you’re free to do what Obama and Bill Gates have done—buy seaside property. They proclaim loudly that the sea level is rising dangerously, but like the majority of climate alarmists, their actions belie their words.

My very best wishes to everyone in these most strange of times,

w.

PS—My usual request. To avoid misunderstandings, please quote the exact words you are discussing. I can defend my words, but I cannot defend your understanding of my words.

PPS—My post linked to above, “Accelerating The Acceleration“, earned me a laughable “fact-check” on Facebook by some well-meaning folks who were apparently short on cranial horsepower … now that Facebook has announced it’s taking over as the global arbiter of scientific truth, we’ll see what happens to this post.