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Climate Cherry Pickers: Falling sea levels in 2010

Posted on 3 October 2010 by John Cook

A proper understanding of climate requires we consider all the data, the full body of evidence. A common rhetorical technique used to portray a skewed picture is the technique of cherry picking. This involves choosing just the select pieces of data that paint a certain picture, even if the full body of evidence gives the completely opposite result. A vivid example of this is a recent post by Steve Goddard which casts doubt on the fact that we've experienced record hot temperatures over the last year, citing falling sea levels in 2010. This is based on the following graph showing satellite measurements of sea levels over 2010:

The satellite data comes from the University of Colorado - you can download the data directly. This data goes back to 1992. Here's what the full body of evidence looks like:

Early in 2010, global sea levels hit the highest levels on record. Realising this fact is not possible when the only data presented is the following:

Of course, there's a lot more that can be picked apart in Goddard's blog post (and readers are welcome to contribute to this process). There's no discussion of why sea levels might be dropping this year (I suspect it has something to do with the switch from El Nino conditions in early 2010 to La Nina conditions in the middle of the year). There is no exploration of what other factors besides air temperature contribute to glacier ice loss - Robert has explained the complexities of why glaciers loss mass here, here and here.

Instead all we are presented with is strong conclusions drawn from a very short piece of climate data. This is taken from a noisy signal showing many ups and downs throughout the long-term trend of sea level rise. A proper understanding of climate deserves much more than this.

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Comments 1 to 50 out of 86:

  1. I have to object to the description of cherry picking as a "rhetorical technique". It is no more a rhetorical technique than is any other logical fallacy. See http://www.iep.utm.edu/fallacy/#Cherry-Picking. Rhetorical techniques are described at another site, http://rhetoric.byu.edu/ -- in addition to in the classic book I keep mentioning, Aristotle's On Rhetoric.
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    Response: I've still got a copy of Aristotle's Rhetoric sitting on my iPad, waiting to be read. Need more hours in the day...
  2. Bahh - it's part of an attempt to persuade, an element of discourse. Any attempt to create a narrative out of raw data (through modeling or even simply graphing) is a communicative act--an attempt to persuade--even if it's directed toward one's self. Cherry-picking even fits the more narrow definition of "effective communication"--people cherry-pick because they know it's a startling (pathetic) way to alter the reader's beliefs, particularly when set up as a counterargument.
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  3. When I saw the title, I wondered how anyone could make such a ridiculous argument -- then I saw who had made it.... A very quick look at the second figure shows 8 previous "sea level falls" similar to the drop since early 2010, over the last 28 years. So something like this happens about once every 3 years. This is so not news.
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  4. Best laugh I've had for a while there John - just loved the Goddard version of the graph (and a clever illustration of the problem too) :)
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  5. There are obvious signs that this graph has been manipulated in such a fashion as to support a preconceived notion. His sample consists of only twelve data points (apparently not grasping that his data set only amounts to less than one third of calendar one year,) further he felt obliged to artificially smooth the twelve data points thereby implying a data set with higher resolution.
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  6. "There's no discussion of why sea levels might be dropping this year (I suspect it has something to do with the switch from El Nino conditions in early 2010 to La Nina conditions in the middle of the year)." The Pacific Ocean has been turning colder recently as part of a regular cycle that has probably been going on since the ocean came into existence. A simple Google search tends to verify your suspicion. Here are just a few websites that came up near the top; take your pick. Adios El Niño, Hello La Niña? Children of the Tropics: El Niño and La Niña El Niño and La Niña Adios El Niño, Hello La Niña? NOAAWatch El Nino / La Nina Headlines
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  7. @MatJ #1 I have to object to you objecting to the description of cherry picking as a "rhetorical technique". Does Aristotle's "On Rhetoric" have a section on nitpicking? :-)
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  8. Interestingly, in a comment, he attributes a "spike in late 2009" to El Nino--yet the subsequent decline must be due to Hansen's perfidy, not to the end of El Nino and the beginning of La Nina. He's not only cherrypicking data, he's cherrypicking explanations, too.
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  9. It's criminal that the best minds we have are forced to spend their valuable time neutralizing the nonsense of the contrarians. Their valuable time would be much more productively utilized if they spent their time on the real challenge awaiting us in the future!
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  10. I don't care that Goddard does not even remotely understand how our climate works. What's important is why Watt still publishes his posts after having stopped him on Arctic sea ice. By the way, even the x axis label is wrong.
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  11. Isn't the heat spike in atmospheric temperatures caused by El Nino from heat being dumped from the ocean into the atmosphere? In which case, it makes sense that sea levels might fall, even whilst sea _surface_ temperatures rise, because the heat is being transferred from lower down. I have no idea if this is correct, I'll check it out...
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  12. @ Bob #9 Agreed; sadly this will not change, as the contrarians consider anything that waste the time of those working against them as a win.
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  13. Riccardo, I'm afraid Goddard is reduced to self-publishing his poetry these days, having fallen off the bottom of the food chain.
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  14. #5" "His sample consists of only twelve data points (apparently not grasping that his data set only amounts to less than one third of calendar one year" Ah, but with such a sample, the graph above and a ruler, one can see the new trend: sea level is falling by 30 mm/yr! Clearly, Goddard must now be considered an alarmist! An yet, he goes on to throw a stone at our own John Cook, observing Current sea level rise rates are much lower than the average for the last 15,000 years. Current trends are more than an order of magnitude lower than Hansen’s forecast. In the-world-according-to-Goddard, trends can simultaneously be both smaller and larger.
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  15. SSTs respond to ENSO cycles. The current la Nina is a very cold one. You can check out the drop here by selecting 'sea surface' (instead of near surface layer ch04). You can see the drop graphically here, and see the indices here.
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  16. Just two points that I know may have an effect (without denying climate change) is when glaciers melt the weight allows the continental land mass to rise in a reflex action. The other issue is when heat leaves one body and enters another the former body will naturally contract as the heat (energy) leaves and the structural atoms slow down their activity due to less energy to drive the activity and move closer together hence contraction. Sea level would therefore fall marginally. The only snags to these two ideas is that I have no idea what data points they use to measure the sea level from outer space and whether the expansion/contraction actually is that massive to give a observable change in sea levels. On the issue of graphs you can make them look even more impressive by simply changing the scales on the x or y axis to heighten the point you wish to make. Take a 1 degree temperature rise over 30 years. If you shorten the x axis and lengthen the y axis you will produce a graph that looks like the Himalayas. Do the opposite and it becomes a flat line which appears to show nothing. Depends on who you want to convince of the facts and how gullible the listeners are I suppose.
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  17. muoncounter #14: And, of course, the 15,000-year period he uses includes almost all of the sea level rise resulting from the end of the last ice age. The vast majority of this rise was finished by about 7,000 years ago. This is like saying that the four pounds Harry has gained since last year is meaningless because it's less than his average annual weight gain since birth. Goddard has to compare the current rate to the rate over the entire post-glacial period rather than to the rate over the last ~5,000 years because then he'd have to change "much lower than" to "much higher than". That wouldn't be helpful to his position.
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  18. Goddard, FYI.
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  19. And note also please, it seems that Goddard used the SL data to which the inverse barometer correction has not been applied. If true, double fail for Goddard.
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  20. #15: "SSTs respond to ENSO cycles." This is about sea levels. Can ENSO cycles really have any long term effect on sea level? They are, after all cycles, which tend to average out to small change. Switching now to the ENSO thread.
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  21. Goddard has no shame, apparently. Against my better judgment but driven by curiosity stimulated by this thread, I mooched over to his blog and within a moment found him likening teachers to pedophiles.
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  22. #21: Yes, we are subverting their innocence with such filth as 2+2=4 and the like.
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  23. Albatross, if he used the barometer-corrected data, it wouldn't show what he wants it to show, so what good would it do him? I like the comment on Goddard's thread from the guy who's against the metric system. Hilarious. It reminds me of a thread on another denier site where they were arguing that ice sheets like Greenland's must be able to come and go in the relative blink of an eye because the earth is only 6000 years old, after all. It shows you the mindset that science and reason are up against.
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  24. I love those extreme cherry picks. Sea level has not risen for 6 months! It´s almost 8 pm here. Global Warming has stopped for at least 5 hours...
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  25. Not sure about Goddard(he doesn't seem right in this case), but the graph at the top of this post and the one at comment 18 both show the rate of sea level rise to below the mean for most of the past 3 years, meaning the rate of rise has decreased compared to the past rate the past 20 years.
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  26. I love all this stuff about graphs and trends showing declines or slowing or whatever for a few years or months. It's like a commentator on a car race. Oh, my goodness, that last lap was 3 hundredths of a second slower than the previous lap. The fact that the driver in question is lapping the field is irrelevant - because the race is actually won. So we have to find -something- to talk about.
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  27. #25: "meaning the rate of rise has decreased compared to the past rate the past 20 years" Not so. In a time series such as this, small variations do not have a significant impact on the long term trend. Those variations are called noise: In signal processing or computing it can be considered unwanted data without meaning.
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  28. Re: nofreewind (25) If you look at the overall trend lines in the long term data shown in the comment 18 you reference, you can see clearly the upward rise in sea levels, despite the noisy seasonal variations present in the signal. A clear analogy would be to maintain that the sun no longer exists because it disappeared over the horizon at the end of the day. Someone intelligent enough to do data research, construct a graph & post it online as part of a blog would know that to focus on such a short-term variation is meaningless. Except for, apparently, Goddard. The Yooper
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  29. Adelady @26, I love that analogy...very good.
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  30. nofreewind @25 I am no expert but i believe you are reading the graph @18 incorrectly. The rate of change is indicated by the slope of that line, 3.2mm/year over the last 17 years. To get the rate for the last 3 years you would have to draw another line from your start point (Jan 2007) to the end. It appears from eyeballing this that it is almost exactly on the same 3.2mm/year trend. If you start from mid 2007 then the slope (rate of change) is actually greater. Someone please correct me if it is I who am misreading the above graph.
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  31. pbjamm @30, You are reading the graph correctly. Be careful about eyeballing though, best to calc. the OLS line. But, yes, it does seem that if one cherry-picked mid 2007, one could argue that SL rise was accelerating. It may be, but that is way too short a time frame for the trend to be statistically significant, and to draw that conclusion based on such a short window would be misleading. Interesting how you and I and the scientists do not make that mistake, but that the 'skeptics' do repeatedly identify short term windows to find trends (no matter how statistically insignificant) to support their misguided claims. I honestly cannot believe to what lengths some people will go to rationalize their belief that global sea level rise is slowing. Even some very smart people like Pielke Snr have made the same mistake.
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  32. You are right, pbjamm (30). In fact, it looks like the rate over the last 3 years is even higher than the average rate because of the dip in the curve in mid-2007. There's no way that variations over such a short time span would be significant, though, so its really a moot point.
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  33. I agree that the 3 year period is far too short to show anything useful and that choosing mid 2007 as a start date would be cherrypicking. I only mentioned it because of the comments by nofreewind @25.
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  34. pbjamm, Sorry if I was not clear. Your position on this was evident to me, I was not criticizing you :)
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  35. The strategy of the political bunch is to cite short-term events when they favor lower temperatures, flat or dropping sea levels, upward-trending Arctic sea ice, etc., ignore the short-term events that show the opposite (which happen to be more frequent and/or of greater magnitude), ignore the longer term trends, or simply assert the data is unreliable. To me, this sort of thing is extremely transparent, and I don't think one needs to be particularly astute to reach the same conclusion. I'm thinking the people who tend to be mislead by contrarians are those who want to be mislead. So to the question of why raw sea levels dropped this year, it seems to be combination of the seasonal signal (see the seasonal signal removed graph and note the smaller drop), the failure to apply the inverse barometer adjustment, and la Nina developing (not also the 1998 drop), resulting in a short-term downward trend of global average ocean temperatures (thermal expansion component is therefore downward trending). With la Nina firmly in place, expect the "global cooling" meme to return, as 2011 will almost certainly be off record levels.
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  36. Alarming increase in flow of water into seas: http://www.sciencedaily.com/releases/2010/10/101004151700.htm "What we're seeing is exactly what the Intergovernmental Panel on Climate Change predicted -- that precipitation is increasing in the tropics and the Arctic Circle with heavier, more punishing storms."
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  37. Staggering, The Ville, staggering.
    "All told, 18 percent more water fed into the world's oceans from rivers and melting polar ice sheets in 2006 than in 1994, with an average annual rise of 1.5 percent."
     I would venture to use the term 'everlasting gobstoppery', for the first time. (shakes head, wanders away) The Yooper
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  38. I just can't resist to comment. My favourite Steve 'Pixelcounter' Goddard piece is his declaring Hansen's Antarctic ice predictions a failure based on recent trends. On closer examination the Hansen prediction in question appears to be for equilibrium at 2x CO2, i.o.w. somewhere around 2070. We're now in 2010. The completely uncritical reception of this story at WUWT is jaw dropping and very revealing.
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  39. So sea levels are dropping which is further confirmation that the ocean heat content isn't increasing. What does this say about the radiative imbalance recently? It can only say one thing...the earth is as warm as it should be. Maybe even warmer than it should be. Anthropogenic CO2 isn't heating it right now. Its ironic that the author should be criticising cherry picking so agressively and yet in the very same breath mention record hot temperatures.
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  40. Tim TTM - just how sure are you that nothing at all is happening in the deep ocean? Unless you're involved in some measurement project that we've not heard about, I'd be a bit more cautious. Where exactly will the heat to drive the next el Nino come from? El Ninos don't create heat, they only redistribute it. Whatever process has a La Nina like the current one showing lower temperatures is the other side of the el Nino coin. After this La Nina there **will** be an el Nino. Maybe straight away, maybe 3 years. Either way, the heat released will not come from nowhere. Just because we can't identify it now doesn't mean we won't see it then.
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  41. @TTTM: "So sea levels are dropping which is further confirmation that the ocean heat content isn't increasing." Yeah, except Sea Levels aren't dropping. That itsy bisty fact kinda demolishes your whole argument, doesn't it?
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  42. TTTM, look at this graph. Notice, sea level sort of bounces along, upward:
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  43. @adelady I am continually astonished by people's misunderstanding of the energy flow associated with the earth. The earth receives about 385 x 10^22 Joules of energy every year. We had been accumulating somewhere between 5 and 10 x 10^22 Joules every year in our oceans. Not recently though. You can easily see that the earth receives from the sun and radiates away to space many, many times that which it accumulates even at the best of times. In answer to your question or rather to put it into perspective, the heat you speak of could accumulate in a matter of days if not hours.
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  44. TTTM - and by what mechanism "could" you accumulate that heat in days? Can we stick plausible physics?
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  45. In fact I'd overestimated the amount accumulated each year. Its actually less than 1 x 10^22 Joules. So to answer scaddenp, the "mechanism" is a single sunny day puts more energy into the upper ocean than is "accumulated" all year.
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  46. Nope - because you cant cheat Planck's Law. Try again.
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  47. What has Planck's Law got to do with the amount of energy input into the ocean from the sun? On the same day the same energy is radiated out to space minus that tiny portion that accumulates. But the point is that you wondered where the energy comes from ands the answer is that its well and truely there.
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  48. So if the energy required (pick a number) can accumulate in a matter of days, how can an el Nino last for months and months? It doesn't generate its own energy. So where is it coming from, how is it sustained for such a long period, why is it sustained for so long?
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  49. #42 doug_bostrom at 16:47 PM on 7 October, 2010 Notice, sea level sort of bounces along, upward The satellite record shows otherwise. If it goes on like this, in 2100 sea level would be below its present day value by 27.5 cm. Nothing scary, really, although it may kill off some shallow coral reefs by exposing them to air. However, by the year 3000 it would drop by 56.6 m, which is deep ice age. In this case I guess Canada should join the Estados Unidos Mexicanos as soon as practicable, then reclaim Texas, New Mexico, Arizona, California, Nevada and Utah along with parts of Oklahoma, Wyoming, Kansas and Colorado.
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  50. BP #49 It's very poor form to show data without properly attributing the source of the raw data (there's something in the graph title but this is not really good enough). Also poor form is to show a curve fit without explaining the methodology used to fit the curve. I'm happy to do some regression diagnostics to see if the curve fit is justified if you point to the location of the raw data (it's not terribly easy to find from a google search of the graph title).
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