Sea Level Data In Monthly Format
Guest post by Bob Tisdale
In this post I have also provided comparisons to scaled NINO3.4 SST anomalies. As could be expected, some of the rises and falls are related to ENSO events. The step changes also appear to be direct responses to El Nino events. I am not, however, implying that Sea Level variability is only impacted by ENSO.GLOBAL SEA LEVEL
The monthly Global Sea Level data from December 1992 to March 2009 is illustrated in Figure 1. The late 1995 spike in the sea level data stands out similarly to the way the 1997/98 El Nino stands out in global temperature data.
http://i31.tinypic.com/op5nw1.png
Figure 1
Figure 2 compares Global Sea Level to scaled NINO3.4 SST anomalies. The peak in late 2005 is not directly related to an El Nino. The impacts of the 1997/98 and the 2002/03 El Nino events, however, can be seen in the Global Sea Level data.
http://i31.tinypic.com/2mrgo5x.png
Figure 2
MONTHLY SEA LEVEL FOR THE ATLANTIC, INDIAN, AND PACIFIC OCEANS
As preliminary notes, the annual variability in the Atlantic and Indian Ocean Sea Level data can be clearly seen in the monthly data. The Pacific data is noisier, which masks an annual signal.
Note how the smoothed Atlantic Sea Level data, Figure 3, appears to rise in steps. The first step is in 1995. This should be a rebound from the Mount Pinatubo aerosol effects.
http://i27.tinypic.com/zs4m0.png
Figure 3
The scaled NINO3.4 SST anomaly data has been added in Figure 4. The smoothed Atlantic Sea Level data rises again in 1997, which should be a response to the 1997/98 El Nino. Are the rises in 2003 and 2005 also responses to the 2003/04 and 2004/05 El Nino events?
http://i32.tinypic.com/t8nrch.png
Figure 4
The raw and smoothed Indian Ocean Sea Level data, Figure 5, show a major step change in 1998 and a curious increase in trend in 2004.
http://i31.tinypic.com/25qzrdi.png
Figure 5
The 1998 upward step in the smoothed Indian Ocean Sea Level data appears to be a lagged response to the 1997/98 El Nino. Refer to Figure 6. The 2004 change in trend does not appear to be ENSO related. Was there a shift in Indian Ocean cloud cover in 2004?
http://i31.tinypic.com/1415glt.png
Figure 6
Following the significant increase from 1998 to 2002, the Pacific Ocean Sea Level, Figure 7, has been relatively flat since 2002. The rise in Pacific Sea Level slowed after 2002, and Pacific Sea Level has declined since 2006.
http://i31.tinypic.com/hsta3q.png
Figure 7
In the comparison with NINO3.4 SST anomalies, Figure 8, note how the Pacific Ocean Sea Level surged upward in mid-1996, one year before the 1997/98 El Nino. Does this indicate that there was a sudden rise in ocean heat content in the year leading up to that El Nino? Does this confirm the findings in my post “Did A Decrease In Total Cloud Amount Fuel The 1997/98 El Nino?” It does seem to show that the 1997/98 El Nino was fueled by a short-term change (one year) in the ocean heat content of the Pacific.
http://i28.tinypic.com/2enn4lk.png
Figure 8
ATLANTIC, INDIAN, AND PACIFIC OCEAN COMPARISONS
Figure 9 is a comparison of Sea Levels for the Atlantic, Indian, and Pacific Oceans. Note how one dataset always appears to be out of phase with the variations of the other two. Rarely do the sea levels of all three oceans rise or fall in unison.
http://i30.tinypic.com/2wh2k9f.png
Figure 9
The SST anomalies for the Atlantic, Indian, and Pacific Oceans are illustrated in Figure 10. There are significant differences between the SST and Sea Level curves. (I can’t see any reason to compare the individual ocean sea level and SST data.)
http://i32.tinypic.com/2gxl5ja.png
Figure 10
SOURCE
Sea Level data is available through the University of Colorado at Boulder webpage:http://sealevel.colorado.edu/index.php
Specifically:http://sealevel.colorado.edu/results.php
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<blockquoteCarl Chapman (02:54:31) :
Bob,
But, the water has to come from somewhere that has a higher air pressure, and the sea level at that place must fall. When you take the global average, they cancel out because moving water from one place to another can’t affect the average. There’s still the same amount of water. I can see where the 9.948 came from. One atmosphere of pressure holds up a column of water about 9 metres high, so 1 millibar equates to about 9 mm.
So Bob, what about the land area! You have seemingly forgotten/ignored the fact that pressure changes over land as well as the oceans. You have correctly stated that increases air pressure reduces ocean level locally and decreased air pressure increases it, this is why the inverse barometer should be used. I hope the guys at UC are kind to you.
Florida has been there before! The land area of Florida has shrunk by more than 50% over the past 12,000 years as sea levels rose after the last ice age ended. See the University of Florida geological study at; “edis.ifas.ufl.edu/document_uw208”
Dumb question: If the Indian Ocean has gone up an inch, shouldn’t the other oceans go up a bit as well (perhaps after a delay?) After all, they are somewhat connected.
On a previous thread, sea level measurements were given an uncertainty of 4mm. I assume this is from satellites. That’s about 12 picoseconds (really double as it is round trip time) assuming they use radar. 25 ps. And assuming you know the location of the satellite to within 4mm. The ocean is seldom flat, tides and weather bounce things around, the moon tugs on the satellites, and atmospheric propagation delay varies by a whole lot more than 25ps. Measuring ocean levels to that claimed precision would be like claiming to measure land surface temperatures to 0.1C with a bunch of uncalibrated and poorly sited measuring stations.
Oh, wait …
Mary Hinge: You wrote, “So Bob, what about the land area! You have seemingly forgotten/ignored the fact that pressure changes over land as well as the oceans. You have correctly stated that increases air pressure reduces ocean level locally and decreased air pressure increases it, this is why the inverse barometer should be used. I hope the guys at UC are kind to you.”
This should be directed to Carl Chapman, not to Bob. You’re quoting Carl, not Bob. I did not state, mention or imply, “that increases air pressure reduces ocean level locally and decreased air pressure increases it…” Air pressure never came up in MY post or MY comments.
And I would think the guys at UC would appreciate my post. All I did was reformat their data so that I could compare it to NINO3.4 SST anomaly data. Nothing contraversial there. Just some wiggle matching.
Regards
OT but interesting, and probably correct.
Regards, Allan
‘Surge in global temps since 1977 can be attributed to a 1976 climate shift in the Pacific Ocean’
Wednesday, July 22, 2009 – By Marc Morano – Climate Depot
A new peer-reviewed climate study is presenting a head on challenge to man-made global warming claims. The study by three climate researchers appears in the July 23, 2009 edition of Journal of Geophysical Research. (Link to Abstract)
Full Press Release and Abstract to Study:
July 23, 2009
Nature not man responsible for recent global warming
Three Australasian researchers have shown that natural forces are the dominant influence on climate, in a study just published in the highly-regarded Journal of Geophysical Research. According to this study little or none of the late 20th century global warming and cooling can be attributed to human activity.
The research, by Chris de Freitas, a climate scientist at the University of Auckland in New Zealand, John McLean (Melbourne) and Bob Carter (James Cook University), finds that the El Niño-Southern Oscillation (ENSO) is a key indicator of global atmospheric temperatures seven months later. As an additional influence, intermittent volcanic activity injects cooling aerosols into the atmosphere and produces significant cooling.
“The surge in global temperatures since 1977 can be attributed to a 1976 climate shift in the Pacific Ocean that made warming El Niño conditions more likely than they were over the previous 30 years and cooling La Niña conditions less likely” says corresponding author de Freitas.
“We have shown that internal global climate-system variability accounts for at least 80% of the observed global climate variation over the past half-century. It may even be more if the period of influence of major volcanoes can be more clearly identified and the corresponding data excluded from the analysis.”
Climate researchers have long been aware that ENSO events influence global temperature, for example causing a high temperature spike in 1998 and a subsequent fall as conditions moved to La Niña. It is also well known that volcanic activity has a cooling influence, and as is well documented by the effects of the 1991 Mount Pinatubo volcanic eruption.
The new paper draws these two strands of climate control together and shows, by demonstrating a strong relationship between the Southern Oscillation and lower-atmospheric temperature, that ENSO has been a major temperature influence since continuous measurement of lower-atmospheric temperature first began in 1958.
According to the three researchers, ENSO-related warming during El Niño conditions is caused by a stronger Hadley Cell circulation moving warm tropical air into the mid-latitudes. During La Niña conditions the Pacific Ocean is cooler and the Walker circulation, west to east in the upper atmosphere along the equator, dominates.
“When climate models failed to retrospectively produce the temperatures since 1950 the modellers added some estimated influences of carbon dioxide to make up the shortfall,” says McLean.
“The IPCC acknowledges in its 4th Assessment Report that ENSO conditions cannot be predicted more than about 12 months ahead, so the output of climate models that could not predict ENSO conditions were being compared to temperatures during a period that was dominated by those influences. It’s no wonder that model outputs have been so inaccurate, and it is clear that future modelling must incorporate the ENSO effect if it is to be meaningful.”
Bob Carter, one of four scientists who has recently questioned the justification for the proposed Australian emissions trading scheme, says that this paper has significant consequences for public climate policy.
“The close relationship between ENSO and global temperature, as described in the paper, leaves little room for any warming driven by human carbon dioxide emissions. The available data indicate that future global temperatures will continue to change primarily in response to ENSO cycling, volcanic activity and solar changes.”
“Our paper confirms what many scientists already know: which is that no scientific justification exists for emissions regulation, and that, irrespective of the severity of the cuts proposed, ETS will exert no measurable effect on future climate.”
—
McLean, J. D., C. R. de Freitas, and R. M. Carter (2009), Influence of the Southern Oscillation on tropospheric temperature, Journal of Geophysical Research, 114, D14104, doi:10.1029/2008JD011637.
This figure from the McLean et al (2009) research shows that mean monthly global temperature (MSU GTTA) corresponds in general terms with the Southern Oscillation Index (SOI) of seven months earlier. The SOI is a rough indicator of general atmospheric circulation and thus global climate change. The possible influence of the Rabaul volcanic eruption is shown.
Excerpted Abstract of the Paper appearing in the Journal of Geophysical Research:
Time series for the Southern Oscillation Index (SOI) and global tropospheric temperature anomalies (GTTA) are compared for the 1958-2008 period. GTTA are represented by data from satellite microwave sensing units (MSU) for the period 1980–2008 and from radiosondes (RATPAC) for 1958–2008. After the removal from the data set of short periods of temperature perturbation that relate to near-equator volcanic eruption, we use derivatives to document the presence of a 5- to 7-month delayed close relationship between SOI and GTTA. Change in SOI accounts for 72% of the variance in GTTA for the 29-year-long MSU record and 68% of the variance in GTTA for the longer 50-year RATPAC record. Because El Niño-Southern Oscillation is known to exercise a particularly strong influence in the tropics, we also compared the SOI with tropical temperature anomalies between 20°S and 20°N. The results showed that SOI accounted for 81% of the variance in tropospheric temperature anomalies in the tropics. Overall the results suggest that the Southern Oscillation exercises a consistently dominant influence on mean global temperature, with a maximum effect in the tropics, except for periods when equatorial volcanism causes ad hoc cooling. That mean global tropospheric temperature has for the last 50 years fallen and risen in close accord with the SOI of 5–7 months earlier shows the potential of natural forcing mechanisms to account for most of the temperature variation.
Received 16 December 2008; accepted 14 May 2009; published 23 July 2009. [End Abstract Excerpt]
Bob Tisdale (02:41:11) :
Allan M R MacRae: You wrote, “If you have time, please plot seasonal (monthly) sea level vs the seasonal CO2 sawtooth data, and let us know what you find… Suggest you use Mauna Loa CO2 and Pacific Ocean.”
The CO2 curve shows an almost constant rise with a seasonal signal, while the Sea Level curve shows significant year-to-year variability.
http://i29.tinypic.com/vytoqw.png
*************
Thank you Bob. I’ve always found it interesting that CO2 and sea level both have a clear seasonal cycle.
I think we understand the driver of the seasonal CO2 cycle, which ranges from almost 20ppm in the far North to near-zero at the South Pole. It is the dominance of the larger Northern Hemisphere landmass and its seasonal photosynthetic cycle, reducing CO2 in the NH summer and increasing in the NH winter.
What do you think are the largest drivers of the seasonal cycle in sea level measurements?
Sorry Bob, got a bit mixed up with the cut and paste so apologies.
I will redirect my question to Carl and ask why he has omitted 25% of the Earth’s surface in his calculation?
Sea Level Rise; A Major Non-existent Threat Exploited by Alarmists
By Dr. Tim Ball Monday, July 6, 2009
Sea level is not level. This is a surprise to most people and enough to make claims of changing level questionable. For example, it is different at each end of the Panama Canal yet the Pacific and Atlantic Oceans are connected at the both ends of the Americas. Sea level varies with changes in atmospheric pressure. It can rise up several meters over very large areas under large low-pressure systems. This is a factor in dramatic sea level rise when hurricanes approach land. It can vary with winds piling it up in one area and removing it in another. It varies with variations in crustal density.
Hotdog, looks like Florida will be a great place for crabbing and fishing. Getting rid of all those selfish beach dwellers!
Hi folks, I’m a geologist from Turin, NW Italy.
20 years ago, back at university, a professor of mine (a senior geologist, with almost 40 years spent working in the field, mainly in Quaternary researches) was telling us that, in the geological record, most of the changes in sea level (“eustatic” movements) were caused by changes in the rate of plate tectonics, i.e. the rate of sea floor spreading.
With a faster spreading, the middle oceanic ridges will “bulge” (they rise up to 3000 m from the bottom of the ocean), moving upward the floor of the oceans and displacing a larger volume of water, thus leading to a rising sea level.
During periods of tectonic “pause”, a slower spreading will lead to a faster cooling of the whole oceanic ridges (they are made of basalts), causing them to “shrink”, reducing their volume and so leading to a fall in the sea level.
Thanks to satellite measurements, now we can measure the rate of continental drift and ocean spreading (IIRC, in the Atlantic it’s more or less 20 – 40 cm/year) at least back to the early ‘80s.
We have also some “proxy” data to measure the rate of tectonic activity: the number and magnitude of earthquakes worldwide, the number and magnitude of volcanic eruptions and so on, more or less like the sunspot number to measure the Sun’s activity.
Well, it could be really interesting to compare the rate of tectonic spreading vs. sea level, just to see if there’s some correlation…..
Not to mention that a faster tectonic spreading means more geothermic heat released from the floor of the ocean: time ago, I’ve read something about researches correlating the El Nino events with increased tectonic and magmatic activity in the Nazca plate (and showing a really GOOD correlation).
Just my 2 cents
PS sorry for my English, I wish it could be more fluent…
Amyone, I have heard that the SL satelite measurements are partially calibrated by tide guages. If this is true then the guages selected could invest a bias. Has this been studied, and if so what are the results?
Fascinating info as always.
Sea level varies by so many different factors. I’m seeing:
• the moon’s gravity
• localized air pressure variations
• currents affect distribution of seawater / pooling affects currents / containment affects pooling
• geographical containment: the shape of each basin and the size of inflow / outflow to adjacent basins
• salinity affects volume / glacial meltwater affects salinity / volcanism affects glacial meltwater
• localized temperature expansion and contraction affects volume
• solar gain: less cloud cover = more heating
• earth’s 23 degree tilt, 24 hour day, 365.25 day year / majority of land in northern hemisphere affects solar gain
• volcanic aerosols cause pronounced cooling effect especially at low or high latitudes
• new research suggests that cloud cover is influenced by cosmic rays
• cosmic ray intensity influenced by variations in the height of earth’s atmosphere which is unusually low possibly due to very low solar output which reduces the atmospheric volume by reducing atmospheric solar heating
• changes in each basin’s size, shape, and interface to other basins due to plate techtonics, volcanism and many other factors
• biological inputs such as large algae blooms might influence the system, fertilizer runoff influence algae blooms
• possible human-caused inputs: runoff pollution / sewage and other ocean dumping, runoff heating caused by pavement and roofs, particulate pollution affects air clarity, mercury pollution caused by coal burning affects ocean biology
• the entire water cycle affects sea level: clouds are key
What other factors influence sea level?
This is just one incredibly complex aspect of the overall global climate. Computers cannot possibly model gloabl climate accurately. The complexity of the system is awe-inspiring…
Since I live here that picture is so stupid I would have thought the computer would have refused to create it.
Mary Hinge: You wrote, “So Bob, what about the land area! You have seemingly forgotten/ignored the fact that pressure changes over land as well as the oceans.”
Changes in the air pressure over land areas aren’t going to affect the sea levels. I’m sorry, but I can’t see your point.
Dario (09:53:42) :
Hi folks, I’m a geologist from Turin, NW Italy.
20 years ago, back at university, a professor of mine (a senior geologist, with almost 40 years spent working in the field, mainly in Quaternary researches) was telling us that, in the geological record, most of the changes in sea level (“eustatic” movements) were caused by changes in the rate of plate tectonics, i.e. the rate of sea floor spreading.
With a faster spreading, the middle oceanic ridges will “bulge” (they rise up to 3000 m from the bottom of the ocean), moving upward the floor of the oceans and displacing a larger volume of water, thus leading to a rising sea level.
During periods of tectonic “pause”, a slower spreading will lead to a faster cooling of the whole oceanic ridges (they are made of basalts), causing them to “shrink”, reducing their volume and so leading to a fall in the sea level.
Thanks to satellite measurements, now we can measure the rate of continental drift and ocean spreading (IIRC, in the Atlantic it’s more or less 20 – 40 cm/year) at least back to the early ‘80s.
We have also some “proxy” data to measure the rate of tectonic activity: the number and magnitude of earthquakes worldwide, the number and magnitude of volcanic eruptions and so on, more or less like the sunspot number to measure the Sun’s activity.
Well, it could be really interesting to compare the rate of tectonic spreading vs. sea level, just to see if there’s some correlation…..
Not to mention that a faster tectonic spreading means more geothermic heat released from the floor of the ocean: time ago, I’ve read something about researches correlating the El Nino events with increased tectonic and magmatic activity in the Nazca plate (and showing a really GOOD correlation).
Just my 2 cents
PS sorry for my English, I wish it could be more fluent…
Dario, your English is fine, thanks for this posting.
I always have assumed that “spreading” would lower the ocean levels.
Thanks for correcting this assumption.
Very interesting.
We are talking about incredible area’s here involving massive volumes of ocean floor and water. It’s a very viable theory which can be tested here.
Tom in high and dry Florida (17:48:32) :
The Florida “scare” map gives me a chuckle. I am located on the central west coast about half way between Tampa Bay and Port Charlotte Harbor. I live about 1 mile inland from the Gulf and this map has me in blue. Umm, one slight problem though, the official elevation certificate for my house used for flood insurance has me at 15 feet above sea level. So either the map is a load of crap or sea levels will have to rise over 15 feet for this to be an accurate representation. I believe it is the former.
Don’t worry too much Tom,
Most of the Dutch live 15 meters below sea level.
No problem at all.
Bob Tisdale (02:41:11) “The CO2 curve shows an almost constant rise with a seasonal signal, while the Sea Level curve shows significant year-to-year variability.
http://i29.tinypic.com/vytoqw.png
“
The way to bring out the interannual variability in CO2 is to look at the annually-integrated rate of change. (Recall Dr. Spencer’s WUWT post from a while back – he arrived at a similar result via a similar approach.) There’s a good (but somewhat intermittent) match with LOD, SOI, AAM, T, & SST. (Differencing & annual-integration are necessary for some of these series to see the phase-relationship. For example, LOD needs to be differenced & annually-integrated twice.)
Bob, thanks for pointing my attention towards some new series to investigate. The suppression of the annual cycle in the Pacific is very interesting. This suggests an array of opportunities to learn something very important from the temporal pattern of quantitative spatial contrasts. (This is one of the ways we get around the lack of information contained in global annual averages.)
Note the overall “fear factor” and “Al Gore’s scary movie effect” that control this propaganda about rising ocean levels.
Hansen’s, Pelosi’s, Obama’s, and Gore’s entire propaganda effort is “heat” and “hot air” -> which means that (obviuously) temperatures. Never mind that temp’s actually only went up less than 1/2 of one degree upthrough 1998, and have decreased since 1998 by about 3/10 of one degreee. They don’t want you knowing “numbers” – they want you fearing technology do you give them control of your life and money!!
After exaggerating the 1/2 of one degree increase, and then extrapolating it several centuries until “catastrophe” is “obviously” upon us, they then wave their hands magically and get you assuming that the final temperature will be enough to melt the ice caps. (Reasonable, in its own way, since in the colder extremes, CO2 IS (correctly) much more prominent in reflecting heat radiation than water vapor since the relative humidity is so much less. With very, very little water vapor, an increase in CO2 does increase the reflection of radiation – just not as much as they are getting you to fear.)
So now that they have (the world) convinced that catastropic warming will happen in the far north and south, obviously the ice will melt -> and obviously that will raise sea levels (since the melted ice has to go somewhere -> and so sea levels must rise! (Add to this the “feedback” of black paper on white ice = more open ocean is (wrongly!) theorized to yield more open water that in turn increases the heat absorbded by the ocean and so it melts more ice… (Except that sea ice extents in the real world don’t work this way, as shown by the ice recovery from 2006 to 2007 to 2008 to the record highs sea ice extents of spring 2009!)
Realize also that the simple Mercator projection maps of most classrooms and textbooks make Greenland look twice as large as Brasil … Can you see how he exaggerates the fears of the gullible?)
So the rising sea levels (in actual levels of mm per year) are the result od carefully developed fears that are not based on real world facts.
Dario,
Your English is excellent. My Italian needs much work.
As to continental drift and ocean levels, my initial thought was it would have zero effect. After all, as one ocean basin expands laterally, another must contract. All the continents cannot move away from each other.
However, you bring up a good point about mid-ocean ridges growing as continental plates drift apart. What is needed is a measurement of the ocean basin volume. I think the U.S. Navy has good sea-floor maps, but they may consider the data too valuable militarily to disclose. Perhaps there are other non-military sources of data.
Interesting. However not a word is mentioned about land-rise and land-fall.
.
Such a thing ~does~ happen and is subject to several agencies, two of which are excessive extraction of ground water and gravitational influences caused by the Sun and Moon.
.
I wonder: WHERE are those measurements are being made, and are they in areas of high human occupancy?
.
Are any of them in locations where there is little or no human occupancy?
.
If you get my drift here, this is not unlike the UHI (Urban Heat Island) situation.
.
Just a thought.
Carl Chapman (15:59:20) :
Mary Hinge: You wrote, “So Bob, what about the land area! You have seemingly forgotten/ignored the fact that pressure changes over land as well as the oceans.”
Changes in the air pressure over land areas aren’t going to affect the sea levels. I’m sorry, but I can’t see your point.
—————–
I would have thought that a decrease in atmospheric pressure would permit the water beneath it to expand, not to be supplemented by water flowing in from the sides. In fact, at least on a local scale, this expanded water should flow away to the areas of high atmospheric pressure, where the water has not expanded. Whether there’s a net rise of the surface level or not should depend on the extent of the atmospheric low. I can’t imagine that any of this can be measured so precisely.
To Oliver Ramsay.
History of comments:
Mary Hinge: You wrote, “So Bob, what about the land area! You have seemingly forgotten/ignored the fact that pressure changes over land as well as the oceans.”
Changes in the air pressure over land areas aren’t going to affect the sea levels. I’m sorry, but I can’t see your point.
—————–
Oliver Ramsay wrote: I would have thought that a decrease in atmospheric pressure would permit the water beneath it to expand, not to be supplemented by water flowing in from the sides. In fact, at least on a local scale, this expanded water should flow away to the areas of high atmospheric pressure, where the water has not expanded. Whether there’s a net rise of the surface level or not should depend on the extent of the atmospheric low. I can’t imagine that any of this can be measured so precisely.
My reply to Oliver:
You’re right. A change in air pressure will expand or contract the water in the ocean. The effect is about 1/50 th of the errronous multiplier that the Uni of Colirado use. They use 9.948 mm/millibar, which is the multiplier for moving water from a high pressure area to a low pressure area (no affect on the average). The multiplier that you refer to, for compression of water is roughly 0.202 mm/millibar, which is smaller than the measurement errors.
This is a copy of my original comment.
The alarmists also show a graph from the Colorado Uni showing the sea level rising. I thought that was strange, so I checked and found an error in their adjustment for “inverse barometer”.
Their web site, is http://sealevel.colorado.edu/.
It shows the graph you often refer to.
If you click on this link on that page: mean sea level time series you go to a page where you can choose an option for “Inverted barometer applied”. That gives you the graph that the alarmists like to use, as it shows the sea level still rising.
The first graph shows a decreasing trend since 2006. The second shows an increasing trend. The whole of the second graph has been moved up about 10mm of sea level.
Their first webpage has a link for documentation, which has the formula they use for the adjustment:
Inverted Barometer = -9.948*(1013.3 – global_average_pressure)
It also states “The inverted barometer does not have much apparent effect on the global mean sea level because the ocean as a whole is not compressible.”. However, moving the whole graph up by nearly 20%, and changing the slope of the most recent period is a very apparent effect.
The problem lies in the coefficient in the formula: -9.948 mm/millibar
If the air pressure at one place over the ocean decreases by 1 millibar, the sea level will rise by about 9mm. But, the water has to come from somewhere that has a higher air pressure, and the sea level at that place must fall. When you take the global average, they cancel out because moving water from one place to another can’t affect the average. There’s still the same amount of water. I can see where the 9.948 came from. One atmosphere of pressure holds up a column of water about 9 metres high, so 1 millibar equates to about 9 mm. That’s correct for local effects such as storm surges, but someone mistakenly used it for a global average.
This is the correct calculation, in accordance with the statement that “The inverted barometer does not have much apparent effect on the global mean sea level because the ocean as a whole is not compressible.”:
The compressibility of water is 5.1×10-5 bar-1. The average depth of the ocean is 3790 metres. Both those figures are from Wikipedia but they seem about right. One bar would compress water by a factor of 5.1×10-5 so a millibar would give about 5.1×10-8. Multiplying by 3970 metres gives 0.000202 metres per millibar, which is 0.202 mm per millibar. The formula has 9.948, which is out by a factor of nearly 50.
The formula should be
Inverted Barometer = -0.202 *(1013.3 – global_average_pressure)
I suspect that the adjustment for inverse barometer, when using the correct formula, would be truly insignificant.
I’ve asked them to correct their formula. I’ll let you know what happens.
The other interesting thing is why alarmists go to such lengths to get to the erroneous graph, when the correct one, which you use, is right there on the first page. I think it’s like Simon and Garfunkle said “we see what we want to see, and disregard the rest.
I think this is a very important issue. I couldn’t figure out why alarmists have been saying the sea level is rising, when the University of Colorado says it’s falling, as you have mentioned many times. Now I know that there’s a mistake on their website, causing them to show an erroneous graph that the alarmists are referring to.
Bob Tisdale
Good article. Looking at the ATLANTIC OCEAN SEA LEVEL & SCALED NINO3.4 SST ANOMLAIES graph , I can see the possible effect of 5 EL Ninos. There could be a base rise of the ATLANTIC OCEAN level, independent of the El Nino any way during these periods that is only perhaps amplified by the EL Nino , the extent of which is not clear. I counted at least 8 other sea level peaks , that seem to be unrelated to ENSO. [ like late1995,late 1998, late 1999, 2000, 2001,2003, 2008] .So I think the ocean level rises in the Atlantic are also caused by internal changes like AMO, seasonal warming ,etc.[ as the peaks seem to occur at the latter part of the year]
Regarding sea levels, an interesting article on unusually high tides along the U.S. Atlantic coast recently.
Quote from the article: “Since June, tides have been running from 6 inches to 2 feet above what would normally be expected, even considering seasonal and lunar fluctuations. While local tidal changes are not uncommon, researchers for the National Oceanic and Atmospheric Administration aren’t sure they have ever recorded an event like this one, which is showing up all the way from Maine to Florida.” [bold emphasis added – RES]
The article goes on to state that they are sure it is not due to global warming.
http://www.charlotteobserver.com/local/story/852054.html
That article about NOAA and unusual high tides (that NOAA failed to predict because they do not understand what is going on) is especially good, considering NOAA’s rather “modest” self-proclamation:
“NOAA understands and predicts changes in the Earth’s environment, from the depths of the oceans to surface of the sun, and conserves and manages our coastal and marine resources.”