I was reading a sign high on the wall behind the bar:
‘Only genuine pre-war British and American whiskeys served here’
I was trying to count how many lies could be found in those nine words, and had reached four, with promise of more …”
Dashiell Hammett, “The Golden Horseshoe”
Google News occasionally throws up some obscure postings that I would never otherwise come across. A recent example was a letter to an editor of a Scottish newspaper (not my usual reading material) declaring that “Climate change is not man-made”. The letter itself is uninteresting – a basic confusion between weather and climate seguing into a NIMBY-ish rant about windmills. Ho hum.
However, in one of the comments from a “Dr John Cameron, St Andrews” (posted 9/Oct/2012), there was this unrelated pseudo-factoid:
As regards the catastrophic sea level rise in the Pacific, it became obvious some 20 years ago that results from island tide gauges did not support computer predictions. Scientists from Flinders University in Adelaide set up new, modern, tide-gauges in 12 Pacific islands to test whether there was in fact any evidence of sinking. Recently the whole project was abandoned as there had been no sign whatsoever of a change in sea level at any of the 12 islands for the past 16 years.
Now this is specific enough to probably actually refer to something real, but doesn’t pass the sniff test for something that might actually be true. Scientists don’t set up monitoring stations only to get the answer they want and then stop monitoring if it doesn’t happen. This only happens in the fevered imaginations of conspiracy theorists. So I was intrigued enough to investigate what this actually referred to…
The easiest way to look for this is to search for the exact string – specifically the second sentence. Google comes up with 1000 or so very close antecedents – particularly with the “new, modern, tide-gauges in 12 Pacific islands” section. The links are to comment threads on partisan websites, the standard climate ‘skeptic’ blogs, and even a mention on SkepticalScience. The comments stretch back around 5 years. Some of the examples give an actual source for the remarks (unlike Dr. Cameron’s version) – one Dr. Vincent Gray – a well known pseudo-skeptic. Some even cite the newspaper article they appeared in – a error-ridden puff piece by Lawrence Solomon at the Canadian Financial Post. Curiously, that online version of the article doesn’t have a publishing date – though secondary sources suggest it was published on Oct 26th 2007. The lack of a date means that people quoting it often claim that this is a ‘recent’ claim.
Going back a little further, Gray made similar claims in a July 2007 article:
A claim that Pacific Islands were sinking led to an investigation by Flinders University, Adelaide, which replaced all the tide gauges in 12 Pacific islands to attempt to find out whether it was true. The attempt has now been abandoned as a failure, as none of the 12 islands showed any significant change since 1991. The team tried to save face by claiming that all showed an upwards “trend” because the 1998 hurricane caused a temporary depression in the ocean. Since 1998 all have remained flat, and the main island of contention, Tuvalu, actually rose last year.
This is referenced to an actual report from the Australian Bureau of Meteorology about the “South Pacific Sea Level and Climate Monitoring Project” (SPSLCMP), dated November 2006. Now we are getting somewhere!
There are some obvious signs of confusion in the Gray/Cameron statements. Firstly, the Australian National Tidal Facility (which installed and monitored the tide gauges starting in 1991) used to be managed by Flinders University in Adelaide – but the facility was transferred to the National Tidal Centre run by the Bureau of Meteorology … in 2003!
Second, the SPSLCMP has been rolled out in stages starting in 1991: the third stage terminating in Dec 2005 – and they are now in stage IV. This might be the source of Gray’s claim that the project had been abandoned, though even the report he cited clearly states that the phase IV was started in January 2006 and was slated to continue at least another 5 years (at that time). The ‘last 16 years’ is a clue that the Cameron statement was obviously written in 2007 not 2012.
Finally, annual reports from SPSLCMP are available through to June 2011 – indicating a project that is very much ongoing and one that was not ‘abandoned’ before 2007.
So none of the statements that Gray (and Cameron) made about the project itself were true (either in 2007 or in 2012). But what about the sea level trends?
This is even odder. The report Gray cites states clearly that relative sea level trends (1992/3/4 to 2006) at all stations were positive (2.7 to 8.1 mm/year for the 11 of the 12 stations with long enough records). The 12th station at FSM was only installed in 2001 and the trends were very noisy (though positive). The Jun 2006 SPSLCMP report goes further and applies corrections for platform movement and the inverted barometer effect, concluding that trends ranged from 1.7 to 7 mm/year at the 11 longer stations. Note that these trends may include a component of subsidence/uplift of the islands themselves and so are the numbers most relevant for local planning (not eustatic sea level change). But so much for not finding a trend!
As one would expect, monitoring has continued since 2007, and in the latest report (June 2011), the 11-station trends range from 2.8 to 7.7 mm/year (and +17.0 mm/year at the FSM station). The monthly data series are available here for people to check for themselves. Comparisons with the satellite altimeter records show a reasonable coherence since the West Pacific sea level has risen faster than the global mean (at least partially related to the number of recent La Niña events).
Trends using all data up to June 2011.
Roughly comparable trends (1991-2012) using the satellite altimeter record.
In summary, every piece of concrete information in the Gray/Cameron statement is wrong. They were wrong even in 2007 when the statement was written and even wronger when it was cut-and-pasted without sources in 2012. Yet demonstrating this took a a few hours of googling, a little familiarity with the issues and people, and obviously is not going to be done by every reader. Thus a statement which clearly make no sense goes unchallenged for years and keeps getting regurgitated. Sure, no single statement like this is likely going to change anyone’s mind about anything, but this one and others like it form part of a drumbeat of disinformation, which by repetition, becomes embedded and hard to shift.
A good question would be why I bothered to research a claim in an obscure comment, on an obscure letter to the editor in a regional newspaper I have never read, and I don’t really have a good answer. Clearly, looking for substantive points in newspaper comment threads is a bit of a fool’s errand, but I was still surprised at how completely wrong every single aspect of the comment was. Given that I did look into it, it is worth sharing here – just on the off chance it will save someone else the bother.
* The Golden Horseshoe award, whose name derives from the Hammett quote above, is for spectacular wrongness in the climate discussion, first initiated by SomeAreBoojums, and occasionally revived by the Wabett.
“The spin over Sandy has begun…
[Response:Pun intended? :)]”
Not this time!
Thanks for the chuckle; there’s little enough to chuckle over, in general.
Guys,
Enough with the sea level. The horse is long dead, can we stop beating it?
Reading the post (and there are many), I cannot see much difference. Therefore, I propose that we agree on a few statements and go on:
1. Sea level started rising in the early 20th century, and averaged ~2mm/yr based on tidal gauge data (the exact figure being dependent upon the database and years chosen).
2. After the launch of the TOPEX satelite in 1993, sea levels were observed to rise at a higher rate than previously measured, possibly due to the persistent El Ninos.
3. Starting in 2002, after the launch of the Jason satellites, SLR slowed slightly, again possibly due to the recent La Nina.
Most of the disagreement appears to hinge on the last statement, and whether it is a significant trend change or just a temporary dip. Is this satisfiable to everyone?
RE: 194. Suppose your right Gavin. Well, ‘cept the report you published ends with:
“Historical sea level trends, and even to an extent the current SEAFRAME sea level
trends, would suggest that we could expect sea level rises of less than 0.5m over the
next 50 years, which is considerably at variance to current scientific commentary. It
is possible, therefore, that the effects of recent accelerations in climate change have
not yet started to have a significant contribution to or impact on current sea levels; but
based on international scientific opinion, it is more a case of when, rather than if.”
What do they mean by “variance to current scientific commentary?” I think there is a typo in there too because the last sentence says “scientific opinion”, don’t they mean consensus?
[Response: Working out what people mean by vague and unsourced statements is always difficult. However, 50cm in the next 50 years is quite serious and at the high end of predictions. Acceleration is expected because of both (small) accelerations in thermal expansion and (larger, though more uncertain) accelerations in ice sheet loss – which is indeed a widely held opinion, and indicative that scientists don’t think that linear extrapolations are particularly informative. – gavin]
Dan H, you don’t understand what you are saying. I repeat since you ignore it, MEI index is meaningless for this discussion. You are refusing to acknowledge the science in your redundant posting. You don’t acknowledge the physical processes in the real world, and you didn’t acknowledge that the MEI is not related to sea level rise. There are no variables in the MEI that are for sea level rise. Who cares what the index is, positive, negative or neutral… it has nothing to do with sea level rise.
Re: 203 Gavin, I have to agree that their summation was subjective, I could clearly see that. I was seriously asking what they thought it was diverging from. I know that Dr. Hansen, as late as 2001, was saying he expected water to be over the West Side Hwy in 20 years (that would be 2021). I believe that would be anywhere from 5 to 10 feet. I image we all know that’s not going to happen so I was trying to figure out who they were referring too. Again, subjective. (okay, the consensus comment was snarky, the consensus survey didn’t come out until 2009 and the SEAFRAME report was from 2006)
I understand from the literature that the various ice sheets on water in the arctic and Ross are melting, but the ice sheet on land over the Antarctic is growing currently, is this not the case? (Mass Gains of the Antarctic Ice Sheet Exceed Losses, Zwally et al, 2008) You asked in 194 how the sea level trend could to go 0, that would do it wouldn’t it (speculation, but there is a probability greater than 0, true?)
[Response: The most recent assessment of mass loss in Antarctica just came out (and we will have a post on this at some point) (King et al, 2012) and suggest +0.19 ± 0.05 mm yr−1 sea-level equivalent. Previous discussions of sea level rise can be found here, here and here. Barring some huge volcano, asteroid impact or other completely unforseen tectonic disaster, there is no conceivable way that sea level will stop rising any time in the next century. None. – gavin]
Re: 205 That was rather definitive, thank you. And I assumed Dr. Hansan’s comments were simply hyperbole. I thought so at the time for what it’s worth, I wish he wouldn’t have said that because it’s been used as a hammer (I’ve been on both sides of the argument, positionally that is). What drew me to this thread was that I did some work with the University of Hawaii with the Micronesian group. I did some initial programming for one of the sites that eventually became part of SEAFRAME, at the time to be setup in the future, so I had an interest). Thank you for your thoughtful responses.
> Cliff Westin … I know that Dr. Hansen …”
Check what you believe; this may help:
http://www.skepticalscience.com/Examining-Hansens-prediction-about-the-West-Side-Highway.html
http://www.globalwarmingart.com/sealevel?lat=40.653&lng=-73.932&zoom=12
Hat tip to Eli T. Rabett, the ‘West Side Highway’ myth was being rebunked: Steve Goddard Drowns in Millard Fillmore’s Bathtub
brief quote from one of many links at the Bathtub page
==== start quote====
How to keep New York afloat
With sea levels rising, once-a-century floods may become once-in-20-years events. One solution: huge storm-surge barriers.
By Moises Velasquez-Manoff, Contributor to The Christian Science Monitor / November 9, 2006
NEW YORK
Like many New Yorkers, Radley Horton often frets about tomorrow’s weather. Unlike many, it’s his job. A scientist at NASA’s Goddard Institute for Space Studies (GISS) and coauthor of a forthcoming study on the effects of climate change in New York City, he is particularly concerned about an often-overlooked aspect of global warming: bigger, stronger storms.
“It’s not a linear relationship,” he says on a subway ride to Manhattan’s South Ferry station, which would be mostly underwater in a Category 2 hurricane….”
=====end quote======
Picture 2012/10/31
Dan H – Questions I have asked that you have not answered:
“Refer to 170, Gavin’s response at 176, plus 174, 175, 178, and 180 (I may have missed some). Do you still insist that SLR is slowing down? If so, how do you explain the strongly supported arguments in 174 and 175?”
Dan: “The increase (SLR) did not continue into the 21st century.” It seems that the great majority of the scientists who study SLR closely completely disagree with you. Can you refer me to a peer-reviewed study that says that SLR increase did not continue into the 21st century? Is the best argument you can muster that these scientists can’t add, as opposed to Dan H, who can?
Charles – the important points about SLR that I can ascertain from the scientific evidence I have seen are that sea level is rising, the rise is accelerating, and that this rise is unprecedented since the end of the last ice age. The best evidence is all pointing in that direction. We also have a very good explanation for the observed SLR – anthropogenic global climate change. Yes, the signal is noisy. There are good explanations for the recent noise. Yes, SLR is geographically uneven – we have good explanations for that uneveness, also. Claims that SLR has “slowed” recently are not well supported (sounds just like “global warming has stopped since [insert recent cherry-picked date here]”). Claims that the observed SLR has been going on for over a thousand years or that the observed SLR is not significant in terms of impact on human societies is hogwash. Please see Atlantic City.
Re- Comment by Hank Roberts — 31 Oct 2012 @ 8:28 PM:
I am not really sure about this but I thought that the problem with New York City is that all of the street drains empty into the ocean and would also have to be blocked from surges. Once blocked any rain would have nowhere to go. Steve
Steve, read that article; it addresses the problem you mention.
RE: 207::Hank Roberts, you are correct, I amend the 2021 to 2028, I was talking off the top of my head on that one, should have double checked. At this point, I don’t believe that will make a difference that the Hwy will be underwater in 2021 or 2028, the models have been amended since 1988. He did say he’s sticking by his predictions in 2001 so, well, that doesn’t make sense to me. That amount of sea level rise is not predicted as Gavin points out; 50cm in 50 years will not put the hwy under water (as Gavin points out, that’s the upper end of the forecast). I still take that as Hyperbole and not helpful to the discussion.
Craig,
With regards to the arguments about SLR slowing, Hank, Unsettled, and Robin presented an explanation that the slowing was due to the strong La Nina event. See posts 129,130,142,157,163,198, and your example of 174. I have neither agreed nor disagreed with this explanation, as it is plausible. Since you refuse to accept an explanation that I give, why not check out their explanations? Here is the same link to the paper by Steve Nerem that Hank provided in post 157, followed by additional published work by Nerem.
http://sealevel.colorado.edu/content/2011-la-ni%C3%B1a-so-strong-oceans-fell
http://sealevel.colorado.edu/content/there-60-year-oscillation-global-mean-sea-level
http://sealevel.colorado.edu/content/comparison-global-mean-sea-level-time-series-topexposeidon-jason-1-and-jason-2
Can cite a reference that SLR has increased since the start of the 21st century?
@Dan H #200:
I appreciate that this is probably a silly question, but why select February 2002, which is before the TOPEX time series starts, rather than say November or December 2002, closer to the start of that series (wthe very end of 1992), where the values of MEI are at 1.057 and 1.109 respectively?
Well, today’s can…
And the JISAO data shows even more clearly that you are cherrypicking your readings. The temperature anomaly was negative in only one month in 2002 (and then only marginally); the astute reader can guess which month that is.
Are you trying to say that if you adjust for the anomalies caused by El Nino and La Nina moving water from ocean to land or vice versa, sea level rise is slowing down?
Robin,
Feb. 2002, was the start date of the Jason satellite data. When viewing the graph of SLR from U of Colorado, the data switches from TOPEX to Jason-1 at that date. I did not select the data based on JISAO, which was referenced by Unsettled in 198, and the values in the preceding and subsequent months are not all that different.
I have done no adjusting for ENSO anomalies in sea level calculations. Others have made such a claim that the cause for the recently observed decline in SLR can be attributed to such. As I stated to Craig, I make no acceptance or rejection of this explanation. My last statement was simply that the SLR was trending lower in the Jason data (2/02 – 5/10) before the 2011 La Nina occurrence. Afterwards, the SLR fell further. Gavin and I already had a discussion concerning detrended SLR graphs.
re 218, Dan “no analysis needed” H.
Poor DH should read today’s “Short term trends: Another proxy fight” and ponder its implications.
Walter,
Yes. It shows how a flat or slightly negative trend can get lost when lumped together with a longer, positive trend. A similar occurance has been occurring here. Very good analogy. Perhaps the slowing in global temperatures is responsible for the slowing in SLR.
220. another example of missing the point, intentionally, by no-analysis Dan.
Astounding it may be, but “The continuation of the linear trend from August 1975 to July 1997 (green dashed), would have predicted a temperature anomaly in August 2012 of 0.524ºC. The actual temperature anomaly in August 2012 was 0.525ºC.”
Or, for the intentionally obtuse…What slowdown?
Congratulations, Dan H. ! You’ve gone full circle. After muddying the waters on sea level rise, you now link your incorrect statements on sea level to your original incorrect statement on a ‘slowing in global temperatures’.
Just like Abbott and Costello (although they were funnier) http://www.youtube.com/watch?v=sShMA85pv8M&feature=related
Craig,
The “hogwash” that SLR has been going on for over a thousand years was a facetious statement made by Martin, that was misinterpreted by several posters. Yes, I was the one who originally confused Martin and Marco, which led to more confusion.
I presume you are referring to hurricane Sandy coming ashore near Atlantic City. I hope you are not implying that the damage would have been significantly less without the eight inches that the sea level rose during the 20th century. The fact that Sandy came ashore at high tide during a full moon had a bigger impact.
215 Clif W said, “He did say he’s sticking by his predictions in 2001 so, well, that doesn’t make sense to me. ”
Here’s the West Side Highway’s elevation, which appears to vary from 90+ ft to 0 ft.
http://www.livestrong.com/loops/new_york_west_side_highway-kM6DUL97lM/
So Hansen appears correct. If CO2 levels double [and nothing else changes, such as raising the road surface], the highway will likely be under water [in some locations].
218 Dan H said, “Others have made such a claim that the cause for the recently observed decline in SLR can be attributed to such. As I stated to Craig, I make no acceptance or rejection of this explanation.”
Ah, one core of this thread. When provided with additional data, does Dan H modify his position?
No. He simply ignores the data. I stand by, and elevate from hyperbole to nearly universal truth:
“Death, duh.”
Jim,
What is this data which I am supposedly ignoring? How would such data cause me to modify my position?
Dan H – SLR has increased since satellite data has been available. You are the one who has arbitrarily picked a start point (as Gavin pointed out) to suggest a SLR “slowdown.” – “the most recent 10-yr trend is also 2.3mm/yr.” As a matter of fact, on this thread, you have also said, “Overall, the global sea level has been (and continues) to rise at ~ 2mm/yr,” which TOTALLY IGNORES the recent satellite data. You continue to use or ignore data and to cherry pick start and end points as you see fit to try to make your case. The Mitrovica tape, which you refuse to discuss, clearly states the research supporting why SLR has accelerated. Nevertheless, here is a good analysis that shows the recent SLR increase, contrary to your claims, without cherry picking:
http://sealevel.colorado.edu/content/2012rel4-global-mean-sea-level-time-series-seasonal-signals-removed
You are, of course, familiar with that data.
Dan, you have said: “The sun and the oceans are the most influential forces on our climate.” Now you want to avoid acknowledging that ocean phenomena such as El Niño might have any effect on SLR – “I have neither agreed nor disagreed with this explanation”. Brilliant.
Charles – Dan H stated: “Sea levels have risen about 16m in the past 8000 years, just not at a constant rate” earlier on this thread. That’s hogwash.
When you add eight inches of floodwater on top of an already record-high flood, increased atmospheric moisture, increased ocean temperature, and very widespread winds, I would say that hurricane Sandy damage was “significantly” enhanced by global warming and the accompanied SLR. It might be interesting to attempt to calculate the added kinetic energy of an extra 8 inches of wind-driven water spread out over the entire New Jersey and New York coastline. What portion of the early estimated $50 billion of hurricane Sandy damage was caused by this eight inches of water would be hard to say, but just arbitrarily, 1% of that would be $500 million. I guess it comes down to what you consider “significant.” I would consider $500 million significant.
“… Lying is an initiation into the conservative elite. In this respect, as in so many others, it’s like multilayer marketing: the ones at the top reap the reward—and then they preen, pleased with themselves for mastering the game…. Sneering at, or ignoring, your earnest high-minded mandarin gatekeepers—“we’re not going to let our campaign be dictated by fact-checkers,” … is another part of closing the deal.”
http://www.thebaffler.com/past/the_long_con/
hey guys, you’re getting a little boring, obsessing on the ignoranti in your midst. A little knowledge is a dangerous thing.
226 Dan H said, “What is this data which I am supposedly ignoring? How would such data cause me to modify my position?”
My last comment, and yes, I know it’s useless. (Sorry, Susan)
If extra rain pulls water out of the ocean and dumps it on land, then one would expect sea level to drop. Since that water will mostly run back to the ocean, the drop doesn’t “count” and sea level measurements *must* be adjusted to account for the temporary anomaly. You were presented this data repeatedly. Your choices were:
1. Accept the new information and change your position.
2. Deny the accuracy of the information and provide substantiation.
3. Ignore it so your position can remain static.
218 Dan H said, “Others have made such a claim that the cause for the recently observed decline in SLR can be attributed to such. As I stated to Craig, I make no acceptance or rejection of this explanation.”
That’s door #3.
Dan H:
I think we all understand that no amount of data will cause you to modify your position. But it is nice to see you imply it so clearly.
And … what Susan said.
Jim,
I have accepted the new information and stated it as a plausible cause for the decline in sea levels over the past 24 months. It is others, such as Craig, who has disputed that SLR has slowed as a result. As I posted previosuly, SLR had slowed prior to the recent La Nina; the increase was 2.5 mm/yr from the launch of Jason-1 until the end of the last El Nino in 2010. While I accept that the recent La Nina has lowered SLR further, the decrease is less than the decrease that occurred prior to its onset. No one has offerred an explanation for the decrease prior to the La Nina.
You seem to attack me for acknowledging the information concerning the recent La Nina, but what about those who deny that SLR has slowed since 2002?
Re- “Comment by Susan Anderson — 3 Nov 2012 @ 10:36 PM:
I agree. To spend the time to produce long, detailed, rebuttals to a troll is making his/her trolling successful. Write very short (e.g. a few sentences) factual responses (e.g. “That is not true, provide evidence). Or just don’t feed the trolls. Steve
So What?
http://www.nature.com/scitable/knowledge/library/modeling-sea-level-rise-25857988
But – seriously — read the linked article.
Think about the point: read the _ads_ surrounding the misinformation PR climate stories.
Think about the audience the _ads_ and the misinformation PR are both designed to convince.
Consider those ads again.
These misinformers are aiming for the niche just above those the Nigerian bank account spammers have targeted. They want people who will believe_almost_anything — and who will vote.
Scary innit? I see Doonesbury for Sunday got there first as usual.
Dan H says in essence – No, no, it wasn’t me, it was people like Craig who got it wrong!
I said nothing about SLR over as short a period as 24 months – NOTHING. You just made that up. That time period is too short to be meaningful for the long-term trends being discussed, which is particularly true for the short end period of a longer sequence. My shortest timeframe was almost 20 years, and the timeframe to which I was referring was that short only because that is the maximum length of time we have been getting that type of satellite data.
You are the only one trying to make arguments about the longer trend based on cherry-picked time frames as short as that.
You have made some pretty outrageous (and unsupported) claims here, so suck it up and accept the criticism that comes with making such claims, and stop trying to blame others for your statements.
Susan – I feel your pain. I have been arguing with “Dan H” about this same stuff for years. He doesn’t quit. He’s right now depositing his droppings of climate-change doubt on the newest post on RealClimate, hoping he can get some new poster there to take him seriously.
“You complain about cherry-picking, then say you only use the data for a 20-year timeframe. Why not use the other data?”
Because there is no satellite data before 1992.
However, if one use tidal gauges, data from 1870 is available. Church, J. A., and N. J. White (2006), “A 20th century acceleration in global sea-level rise”, Geophys. Res. Lett., 33, L01602, doi:10.1029/2005GL024826.
Note the title of the paper. No cherry picking on Craig’s part after all.
> there is no satellite data before 1992.
No matter how often that has been pointed out,
in threads where the “Charles” poster would have seen it,
the “Why not use the other data?” talking point
gets rebunked; seems like old text, maybe an
automated posting triggered by keywords.
in the 21st century a bunch of ocean water was dumped on land causing what some with weak minds interpret as a change in the underlying sea level rise while ignoring the scientific explanation that this change in decadal average is only a temporary change sea level and unrelated to sea level rise. some people have been told this repeatedly in this very thread and still ignore it with posts designed to confuse lay readers. those people ignore the physical processes in the real world and only talk about the trend in the data.
Unsettled,
Exactly! But those weak-minded people keep ignoring this no matter how much it is repeatedly pointed out to them. Those people look only at the trend over the entire period and compare it to the trend from a century ago. Look at the Jason satellite data prior to the recent La Nina.
Dan H said: “The issue is was has [sic] happened in the 21st century.” Actually, there is no scientific issue. The noise is too large in a short time span to determine any statistically significant change in signal. The issue is why somebody would fall for such foolish nonsense, or propound it.
Charles – I have made no statement about your use of a 24-month period, so it is a little curious that you are accusing me of doing such.
And I did post data:
http://sealevel.colorado.edu/content/2012rel4-global-mean-sea-level-time-series-seasonal-signals-removed
I agree that it appears likely that La Niña is responsible for the slightly lower SLR in the past 24 months. In fact, I believe that this supports my point that short-term fluctuations do little to inform us about the longer-term trend. We usually need more data to understand the most recent short-term fluctuations, but that will always be true for every new short-term variation during the most recent time periods. This does not mean that the clearly observed long-term trend is not real or has no explanation.
Which brings us to Dan H – trying to claim that the most recent change in the tail end of any data set somehow is significant to the long-term trend, as you continue to do (I assume to try to cast doubt on the reality of AGCC, since that is what you have always done in the past) is getting old. In a noisy system, noise at the end of a data set is still only noise. That’s like interpreting the observation that each wave recedes means that the tide may have changed after each and every wave, regardless of what our more long-term observations (like the tide charts) are telling us.
How much data is needed to detect a trend? It depends completely on which data set and how much of it you’re testing (and whether you are doing a one-tail or two-tail test, I expect). Look at examples:
One comment on a paper seems to say two decades of data would suffice:
“… climate models … in the last two decades … failed any validation with the much more reliable tide gauge measurements”
Parker, Albert. Comment to Shepard [et al.] Natural Hazards (2012): 1-4.t DOI: 10.1007/s11069-012-0314-2
(that’s a criticism of a paper that assesses storm surge risk for Long Island as it may change with global warming, worth a look since it describes what areas are most at risk: http://dx.doi.org/10.1007/s11069-011-0046-8. Parker didn’t like the notion that warming causes sea level to rise so he claims 20 years of data shows it’s not happening, there.
A different paper says a
“Minimum of 60 years of tide gauge recording are needed to compute a long-term SLR”
Parker, Albert. Oscillations of sea level rise along the Atlantic coast of North America north of Cape Hatteras
And that’s the same Albert Parker, for both of those statements.
Delve deep enough into the details and you might make sense of the way he’s making what appear on the face to be contradictory claims about what the statistics can show.
Point being, if all you want is a talking point without a cite or an understanding — they’re easy to find. That’s why ‘reverse citation’ using Google (finding something after the fact to back up any claim at all) is easy. You can find anything on the Internet whether it exists or not.
Craig,
Only a fool would think that the tide is changing based on every single wave. Also, only a fool would try to compare to differenct datasets without independent confirmation. You may want to read the following about data validation:
http://www.aviso.oceanobs.com/fileadmin/documents/calval/validation_report/insitu/annual_report_insitu_2011.pdf
http://www.oceanobs09.net/proceedings/pp/2A3-Cazenave-OceanObs09.pp.11.pdf
These papers acknowledge the higher rate observed with the Topex satellite, and the slightly lower rate with the Jason satellites, and also gives an in-depth analysis about comparison between tidal gauges. Pay particular attention to Figure 6 in the Cazenave paper. This shows the data observations prior to recent ENSO events. For argument sake, let’s ignore the recent slowing (you should have no problem with this), and assume that the satllite measurments can be directly compared to the tidal gauges. Let’s use the data from the Mitrovica video, which you espouse, for this example. The SLR from 1930-2000 was 2.3 mm/yr, and the rate from 1993-2012 was 3.1. Let us further assume that the previous rate was constant for the 19 years prior to the satellite observations. We arrive at a 0.8 mmm/yr increase over 19 years. If a similar acceleration occurred throught the 21st century, than SLR would reach 6.3 mm/yr by the year 2100. Integrated over the next 88 years, would yield a total sea level rise of ~400 mm (16 in). In order to reach some of the higher projection values, SLR would need to start accelerating soon. Especially to overcome any slower observed in the data.
Dan H, do you realize you said exactly to my pint which is that sea level rise has not changed in the 21 century? the moat recent decadal average does not represent sea level rise so focusing on the last ten years is meaningless. there is no “slower trend”
Dan H. So what?
Dan H – you have a very predictable bag of tricks – you have used this logic again and again. You take a limited data set, with no analysis as to what is happening or why (usually you just deny attribution), and then extrapolate a linear rate of acceleration based on 19 years of data, finally arriving at: “What – me worry?”. Mitrovica puts SLR into perspective. He shows that the recent SLR is anomalous since the last ice age; that SLR accelerated since tide gage data have been available, and that SLR has acceleration has increased again since satellite data has been available. This is not a linear rate of acceleration. He discusses the potential of glacier and icecap melt. Given his evidence, why would SLR NOT continue to accelerate? There are very good reasons why it will. You, however, assume that the present rate of increase, based on 19 years of data, is linear and will continue to be linear. Why? Because, I dunno, it just will?
There seems to be two, at least, problems here. One is the media failing to educate the public about science. The second is that a great many Americans are frightened by the word science. What is the solution? You cannot teach a person how to use a wrench if they do not understand what a nub and bold does for them.
Thanks.