Dark deeds of definitions?

In comments on the sea ice post, both Rob Dekker and Chris Randles has queried an apparent change to the definition of “ice free” as applied to the Arctic. As any fule kno, the definition of “ice free” usually used is “less than a million square km” (1MSK) in order to account for the misc pockets of stuff that will hang around Greenland. FWIW, I’m not sure how useful this defn is, or whether it will survive closer analysis as we get closer to the event, but we’re decades away now so it hardly matters.

Except, there’s an unclarity. Is it 1MSK for a single year (maybe not; there could be a freak year); averaged over 5 years (generally the way things get done); or “for at least five consecutive years”? The latter appears to be what the AR5 SPM says (figure SPM.7 caption): The dashed line represents nearly ice-free conditions (i.e., when sea ice extent is less than 10^6 km2 for at least five consecutive years). For further technical details see the Technical Summary Supplementary Material {Figures 6.28, 12.5, and 12.28–12.31; Figures TS.15, TS.17, and TS.20}. RD and CR point out that earlier drafts (including the final draft) don’t quite say this, that the “five consecutive years” is new. OTOH, in the “final” draft what becomes SPM.7 is SPM.6, so it wasn’t really final; and the dashed line seems to be absent entirely, rather than being redefined.

Also, SPM.7 shows a 5-year-running-mean of sea ice, so when things cross the dashed line, that shows that a 5-year-mean is below 1MSK. So the text, about “consecutive” years, would appear to be wrong anyway.

Perhaps I should go off and read chapter 12 which ought to be the source for this. Figure 12.30 just has the line at 1MSK, and of course the careful language “nearly ice-free Arctic Ocean”. And some text:

A nearly ice-free Arctic Ocean (sea ice extent less than 1 × 10^6 km2 for at least 5 consecutive years) in September before mid-century is likely under RCP8.5 (medium confidence), based on an assessment of a subset of models that most closely reproduce the climatological mean state and 1979–2012 trend of the Arctic sea ice cover. Some climate projections exhibit 5- to 10-year periods of sharp summer Arctic sea ice decline—even steeper than observed over the last decade—and it is likely that such instances of rapid ice loss will occur in the future. There is little evidence in global climate models of a tipping point (or critical threshold) in the transition from a perennially ice-covered to a seasonally ice-free Arctic Ocean beyond which further sea ice loss is unstoppable and irreversible.

So I’m not sure there is anything terribly nefarious in there. Would anyone more closely involved care to comment?

All of this is just an excuse for more pix. Here’s the refuge des Bans, one of the lower down (2000 m) huts and therefore beloved of day walkers. My apologies for not taking it when it was in the sun.

Nice rocks though:

DSC_6146

But its not all rocks and ice:

DSC_6134

Comments

  1. #1 C Stoudt
    2016/09/20

    FWIW from an ocean and atmosphere perspective, ice free would mean no moderation between the ocean/air interface. I don’t really know what that would look like on a basin scale, but it would impact water mass formation and the amount of energy transported from the atmosphere into the ocean. I think you could argue that it doesn’t matter whether minimum concentration falls below a certain amount for x amount of years. What matters is that the Arctic basin as a whole is behaving more and more like the seasonal ice zone. I know that’s not really quantitative but I think it’s a more accurate description of an “ice free” Arctic.

  2. #2 See Noevo
    2016/09/21

    Is Arctic sea ice increasing?

    [It usually does, once it has passed the minimum -W]

    https://notalotofpeopleknowthat.wordpress.com/2016/09/15/arctic-ice-growing-rapidly/#comments

  3. #3 Rob Dekker
    United States
    2016/09/21

    William, I think it was the pictures in this post that made me realize that you are not serious about this change in definition.

    And in a way, you may be right even though the re-definition was wrong as you state correctly.

    After all, if there was any nefarious intent, then inquiring about this with the IPCC authors will not lead anywhere. And if this addition of “five consecutive years” was not nefarious, then we will fix it in the next IPCC (AR6) reports. Either way, I don’t think it matters much what we do now.

    [I’m not sure it is a “change”, in the way that you’re thinking. It is more of a late-minute addition, that doesn’t seem to have been thought through carefully. In particular, there’s the way the description of the figure (5-year-running-mean) and the caption (5 consecutive years) don’t match -W]

  4. #4 verytallguy
    In the aether
    2016/09/21

    By strange coincidence, I’ve been having a discussion similar point at Curry’s with her guest author Greg Goodman, aka climategrog.

    Aside from the obvious crapness of the guest post itself, Greg has a couple of remarkable comments where he claims the choice of definitions of “positive feedback” and “anomaly” are indeed Dark Deeds . He posits a conspiracy to “misrepresent ” science; a ” convention that systematically imposes a predetermined conclusion” no less.

    https://judithcurry.com/2016/09/18/is-the-arctic-sea-ice-spiral-of-death-dead/#comment-812704

    https://judithcurry.com/2016/09/18/is-the-arctic-sea-ice-spiral-of-death-dead/#comment-812726

    (the thread doesn’t make a lot of sense, as several of my comments were moderated; Curry allows a lot of slack to most, including conspiracy theorists, but for whatever reason doesn’t allow the ‘c’ word itself. Why she promotes such dross remains a mystery)

    [Many better people that GG are confused about feedback, and how you can have “positive feedback” in an overall stable system. Moyhu has some good posts on this recently, e.g. https://moyhu.blogspot.co.uk/2016/08/climate-feedbacks-and-circuits.html -W]

  5. #5 crandles
    2016/09/21

    I would agree last minute blunder seems much more likely than any nefarious intent. Also agree if it gets copied into AR6 there is plenty of opportunity for review so that it should get corrected.

    Therefore it may well not be important enough to push the question of whether there are any lessons to be learnt for IPCC processes. Despite that, it still leaves a feel of it shouldn’t have happened without some discussion and leaving a trace in the change documentation and that someone has probably blundered. Ah well, mistakes happen and we shouldn’t want to crucify someone for an unimportant innocent mistake.

  6. #6 Mal Adapted
    2016/09/21

    crandles:

    we shouldn’t want to crucify someone for an unimportant innocent mistake.

    Unless we’re professional AGW-deniers, who would have the credulous believe there are no innocent mistakes, and that the intent of thousands of scientists throughout the 200-year history of climate research can only be nefarious.

    What a world 8^(!

  7. #7 Hank Roberts
    think I need a small vacation ...
    2016/09/21

    https://www.technologyreview.com/s/602421/the-growing-problem-of-bots-that-fight-online/

    They’re assiduously editing Wikipedia

    [Fun. However, In general, bots revert each other a lot: for example, over the ten-year period, bots on English Wikipedia reverted another bot on average 105 times, which is significantly larger than the average of 3 times for humans (https://arxiv.org/ftp/arxiv/papers/1609/1609.04285.pdf) misses the obvious – that the average bot makes far more edits than the average human. It also doesn’t match what I know of bots on wiki. Sadly the paper provides zero examples of what they’re talking about, so it is impossible to check -W]

  8. #8 See Noevo
    2016/09/21

    Re: #2:

    Me: “Is Arctic sea ice increasing?”
    William Connelly [sic -W]: “It usually does, once it has passed the minimum”

    I realize the Arctic ice will increase as we head into winter. What I meant was
    Is Arctic sea ice more expansive *year-round* since 2012?

    [That’s… not a very sensible question, since it can be answered by your own graph; and the answer is clearly “no” -W]

    https://notalotofpeopleknowthat.wordpress.com/2016/09/15/arctic-ice-growing-rapidly/#comments

  9. #9 Mitch
    Oregon
    2016/09/21

    I am fascinated how people act as if a scientific definition is like a legal definition. If there is a more useful definition, change it. I personally think the 5-year average makes the most sense.

  10. #10 David Appell
    United States
    2016/09/22

    I recently asked a well-known NSIDC scientist why they consider SIE < 1 Mkm2 to be "ice-free." They said

    "It’s because we think some ice may still remain along the northern coast of Greenland and within the Canadian Archipelago for a bit longer than the Arctic Ocean."

    Ice clinging to harbors and islands isn't that important, compared to the entire Arctic ocean, and could well last much longer, as ice often does around lakes and ponds. The "changes/benefits" to an ice-free Arctic ocean are for oil exploration and transport ships, and those don't depend on localized harbor conditions. Last year at the AGU meeting an NSIDC scientist told me they get calls all the time from companies asking about ice conditions and forecasts in the Arctic Ocean.

  11. #11 Rob Dekker
    2016/09/22

    The addition of “five consecutive years” to the definition of “ice-free” is not just wrong in the context of that SPM.7 figure, it is also entirely unnecessary.

    If they really wanted to get “five consecutive years” into that caption, they could have written :

    “The dashed line represents nearly ice-free conditions (i.e., when sea ice extent is less than 10^6 km2) for at least five consecutive years.”

    instead of the change in definition they implemented with :

    “The dashed line represents nearly ice-free conditions (i.e., when sea ice extent is less than 10^6 km2 for at least five consecutive years).”

    Now, this change in definition was propagated all through the IPCC documents, with 2 occurrences in the Summary for Policy Makers, 2 more in the WG1 Technical Summary, and at least a dozen places in the full WG1 report.

    If this were just a not very well thought out last-minute addition, it sure left scars all through the reports.

  12. #12 Hank Roberts
    in the cracks
    2016/09/22

    I don’t get why you think this is a change.
    Yes, it’s a definition.

    Each paper considered for that IPCC report will have defined its terms.

    Where is a source for considering one single such year to be a threshold event? And what would happen then?

    And would the IPCC have to back off if the next year wasn’t ice-free?

    It’s climate, not weather.

    Was there some threshold event expected to take place when the arctic had an ice-free summer, that has to be put off now until there are five consecutive years?

    Well, yes — major investment in oil drilling, for example, it’d be foolish to install a five-year drilling rig until, you know.

  13. #13 crandles
    2016/09/23

    >”I don’t get why you think this is a change.
    Yes, it’s a definition.

    Each paper considered for that IPCC report will have defined its terms.”

    OK, then show us a paper that defined its term as requiring 5 consecutive years.

    Fig 12.31 on page 1091 of chapter 12 says
    “Figure 12.31 | (a–d) First year during which the September Arctic sea ice extent falls below 1 × 10^6 km2 in CMIP5 climate projections”

    Fig 2.1 of the synthesis report says “Change in Northern Hemisphere September sea-ice extent (5 year running mean)”
    then later this was wrongly clarified by adding
    “The dashed line represents nearly ice-free conditions (i.e., when September sea-ice extent is less than 10^6 km2 for at least five consecutive years)….”

    So the science quoted in AR5 seems to be working on either first year or average of 5 years. Then at a late stage a clarification was added indicating 5 consecutive years when it was really a 5 year average. Then that 5 consecutive years has spread to various locations apparently without any documentation of such changes.

    5 consecutive years may make sense for oil industry but this is WG1 reporting on the science (not impacts, adaptation,…). This should stick to the science referenced not pull things out of the air.

  14. #14 Phil Hays
    Unclear - a problem for fuzzy logic from a signal processing pov
    2016/09/23

    Consider the future of sea ice as a cloud of possible courses. Consider that real world isn’t often definable as fixed “yes” or “no”, but is usually in some fuzzy state. Example: the chance of rain today might be near 10%.

    The sea ice median path looks something like a decline to 1×10^6 km^2 somewhere around 2050. Or something similar. However, there is considerable spread to the course due to random variability (aka: weather).

    Possible individual paths for sea ice area minimum might include spikes down to 1×10^6 km^2 followed by two decades above this. Or might decline to just above or just below 1×10^6 km^2, and stay there for two decades or so. Or perhaps even longer time periods. And of course, lots of other possible paths.

    A consistent definition of “ice out” for the purposes of decision can’t be just a one year fixed threshold, but needs to have spread to it, either as a time window or as smoothed amplitude, or ideally both. At least, that is how I would view it if I was trying to detect this state while doing signal processing.

    A single year fixed threshold would not allow for consistent comparison between models, and between a model and reality. So yes, I don’t like the “old definition” of Arctic Ocean ice out. However, I’m not sure if I could sell the one I’d like, which would be a probability statement: Based on a function fitted to simulation of sea ice declines, and the past history of measured sea ice extent/area/volume, the probability of ice out state currently is n%,.

    And yes, I have not done the hard work of trying to find a reasonable function. Too much data, too little time, too many other demands on it.

  15. #15 crandles
    2016/09/23

    AR5 should only report on existing science, but there is no reason we cannot discuss what we think the definition should be.

    >”Based on a function fitted to simulation of sea ice declines”

    First though was why simulation rather than actual? Yes simulations of future may be important to identify likely future changes in trend if you want to try to forecast several years in advance. Different simulations currently have very different levels of ice from actual and different rates of decline so they somehow need adjusting to actual historic trend as well as level of ice. Fortunately despite the variety of ice levels and rates of decline the pattern of declining rate of decline as ice free seems robust across large proportion of simulations. Thus it may not be impossible to adjust the simulations to match actual data.

    Anyway that all seems rather complex so why not just use trend of actual data?

    If the rate of decline is quite steep at the time we approach 1m km^2 then 5 year average might be quite late in recognising when nearly ice free conditions are likely to
    recur with sufficient frequency so perhaps a 3 year average would be better in these circumstances.

    However if the rate of decline is very slow, random fluctuations could cause a 5 year average to judge it as having occurred and then later reverse that decision. But the longer period average make the problem above worse.

    Thus you might want to use a longer period average the slower the rate of decline appears to be. However how much longer for what rates of decline does not seem to have obvious answers and looks a bit messy.

    If concerned that a long period average would judge it too late then it might be better to use something like when the ten year trend line of September average extent has clearly (95% probability) crossed to below 1m km^2. What is wrong with this suggestion?

  16. #16 Hank Roberts
    in the cracks
    2016/09/23

    > show us a paper that defined its term
    > as requiring 5 consecutive years.

    I do homework help, sometimes, but only with a note from your teacher explaining why you’re particularly needy.

    You can read the cited papers yourself.

  17. #17 Phil Hays
    Unclear - a problem for fuzzy logic from a signal processing pov
    2016/09/24

    “First though was why simulation rather than actual?”

    The question indicates that I didn’t write a good explanation of what I’m proposing.

    I’m proposing to use both simulation results and measurements to generate a function that will assign a value on an ongoing basis to the value of the fuzzy logic variable “ArcticSeaSummerIceFree”, rather than comparing current sea ice extent/area/volume to a fixed threshold for a day/week/month/year returning a Boolean, or below a fixed threshold for some time period again returning a Boolean, or any similar function returning a Boolean. A useful function for “ArcticSeaSummerIceFree” would be understandable in the context of probability. In other words, an answer of 0.50 would mean that the odds of being currently at the Arctic Sea ice free state would be 50%. Current value is very close to zero.

    Wiki: https://en.wikipedia.org/wiki/Fuzzy_logic

    Fuzzy logic is a method of dealing with decisions to messy problems. This is a messy problem. Fuzzy variables are sometimes probability statements, as probability is a subset of fuzzy logic.

    Your last statement is a fuzzy logic statement expressed as a probability. I like it better than a fixed threshold for one year’s minimum.

    Similar fuzzy logic computations could provide a better estimate of Arctic Ice Out year, regardless of how defined.

    Practical problems include that climate is politically charged, so while this might be useful, it might be attacked as hard to understand. A fixed threshold has the advantage of being simple.

  18. #18 Rob Dekker
    United States
    2016/09/24

    Hank, if you have found any scientific reason to add “5 consecutive years” to the definition of “nearly ice free” then please do your homework and present it.
    Don’t patronize others to do it for you.

    The fact is that there is not a single scientific paper that adds “five consecutive years” to the definition of “nearly ice free”.

    Which makes the point that this change in definition is not founded in science.

  19. #19 Russell Seitz
    Cambridge MA
    2016/09/24

    It’s up to NOAA to move past the animated controversy about moving ice , and settle the question by integrating Deep Space Climate Observatory data into annually averaged multispectral albedo maps of polar brightness trends

  20. #20 Phil Hays
    Casino Royal
    2016/09/25

    Rob,

    http://onlinelibrary.wiley.com/doi/10.1002/2016GL070067/abstract

    The implication is that a fixed threshold for one year will be likely be passed multiple times.

    A fixed threshold for the average of sea ice minimums over five years is a better definition.

  21. #21 Rob Dekker
    United States
    2016/09/25

    Phil, that paper by Jahn et al does not even suggest a change in definition for nearly “ice free” (from the standard 1 M km^2), let alone that an average over five years is “better”.

    However, the paper does find an uncertainty in timing (due to internal variability) of some 20 years.
    Interestingly enough that uncertainty suggests that a change in definition to the ‘average over five years’ will likely occur at least 10 years AFTER the first occurrence of the first ice free summer. And likewise, it suggests that the current IPCC definition “five consecutive years” below 1M km^2 will likely occur at least 20 years after the first time summer sea ice dips below 1 M km^2 in the Arctic.

    Mmmm. For which $4 trillion/year industry is it a BETTER if the IPCC definition of “ice free” occurs 5, 10 or 20 years later ?

  22. #22 Rob Dekker
    United States
    2016/09/25

    Sorry. That last sentence should read as follows :

    For which $4 trillion/year industry is it a “better definition” if the IPCC declares an ice free Arctic 5, 10 or 20 years later than the definition used by climate scientists ?

  23. #23 Phil Hays
    Signal Processing Geekdom
    2016/09/25

    Definitions are political things as well as scientific things. My point of view in this discussion is signal processing, not politics. The IPCC original definition, one year below a threshold, is a less than optimal definition from the point of view of signal processing. Jahn et al (1) and supporting documents seems to have enough information to enable computation of such a function.

    An optimal function, from my point of view, would return an accurate current probability of the ice free September Arctic state, not a Boolean (True/False) value. You could convert this to a Boolean if you wanted, at a threshold of interest. A shipper planning trips through the Arctic in September might want 95% ice free, or even higher. Non-ideal but better functions might be Boolean, and would hopefully return fewer false positives and negatives, and would hopefully have a narrower spread in decision time, and would hopefully have the decision time close to the 50% probability point in time. Better is a value judgment at some level, as there are always trade-offs.

    Table 1(1) for MM “Monthly Mean” gives a range of 2032 to 2053. For a 5YRM “5 Year Running Mean” gives a range of 2040 to 2054, however that is for the first year of a 5 year period, so the detection is 5 years later, or from 2045 to 2059. The spread in time is 21 years for the first, and 14 years for the second. The earliest detection for the MM is 13 years before the earliest detection for 5YRM. The last detection for the MM is 6 years later. This is based on a 40-member ensemble. By my point of view, 5YRM is a better decision function than MM because of the smaller spread in time.

    There are inherent trade-offs between robust detection, ideal detection and quick detection of a signal. The center or most likely first detection time is delayed from a mean of 2042.5 for MM to 2052 for the 5YRM, 9.5 years later. If the warming stopped with a mean September sea-ice extent of around 2×10^6 km^2, we would be falsely detecting an ice free Arctic Ocean every decade or so for as long as climate was stable at that state. For the Moderate Emission case, MM might give the first decision in 2032, and continue to periodically “recover” to a not “sea ice free” state until past 2100. MM is not robust, I have a preference for robust detections over quick detections. More robust functions have fewer false positives and false negatives.

    I have not computed the time of the ideal detection point for the model ensemble, so this section is less emphatic that others. It seems fairly clear that MM is more likely to be early. Until I have a good estimate of the ideal detection time, I can’t say for sure if the 5YRM is closer or the MM is closer. However, I suspect that 5YRM is a little too late, someplace around 2.5 years last just based on how it is computed. If this is correct, then the 5YRM is probably preferred as is probably closer to the ideal detection time.

    Table 1(1) for 5CY “5 Consecutive Years” gives a 16 year spread in time, and would also have fewer false negatives. I’d weakly prefer the 5YRM to 5CY, but both are better than MM. 5CY has a lower spread in time, is likely more robust, and is (less certain) closer to the ideal detection time than MM. 5CY has a larger spread in time than 5YRM, is probably more robust than 5YRM, and is probably later from the ideal detection time than 5YRM.

    Table1(1) also has 10 Consecutive Years, which would have fewer false negatives, but has a 24 year spread in time, as well as a longer delay. Looks less promising than 5YRM or 5CY.

    I know, TL:DR seems very likely, but thanks if you did read it.

    (1) http://dx.doi.org/10.1002/2016GL070067

  24. #24 Hank Roberts
    in the cracks
    2016/09/25

    > which … industry …?
    Freight Forwarding

    Sea ice decline and 21st century trans-Arctic shipping routes
    First published: 20 September 2016
    DOI: 10.1002/2016GL069315

    Abstract

    The observed decline in Arctic sea ice is projected to continue, opening shorter trade routes across the Arctic Ocean, with potentially global economic implications. Here we quantify, using Coupled Model Intercomparison Project Phase 5 global climate model simulations calibrated to remove spatial biases, how projected sea ice loss might increase opportunities for Arctic transit shipping. By midcentury for standard open water vessels, the frequency of navigable periods doubles, with routes across the central Arctic becoming available. A sea ice-ship speed relationship is used to show that European routes to Asia typically become 10 days faster via the Arctic than alternatives by midcentury, and 13 days faster by late century, while North American routes become 4 days faster. Future greenhouse gas emissions have a larger impact by late century; the shipping season reaching 4–8 months in Representative Concentration Pathway (RCP)8.5 double that of RCP2.6, both with substantial interannual variability. Moderately, ice-strengthened vessels likely enable Arctic transits for 10–12 months by late century

  25. #25 Rob Dekker
    United States
    2016/09/26

    I am glad that Phil’s analysis confirms my suspicions that a change in definition of “ice free” from the standard used by scientists (1 M km^2) significantly delays the year that the IPCC could call the Arctic “ice free”, easily by as much as 2 decades.

    Also, since there is no scientific need to change the definition used by scientists to describe developments in the Arctic, these findings only emphasize the strange (dark, and what now looks like deliberate deeds of definition) that occurred during the Stockholm session.

    Let us summarize :
    We know this change happened during the 36th session of the IPCC in Stockholm, because the addition “after 5 consecutive years” is NOT present in the June 7 ‘final draft SPM’ as prepared by WG1 :
    https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/drafts/WG1AR5-SPM_FD_Final.pdf
    and it IS present in the ‘approved SPM’ after the September 23-26 session :
    http://www.ipcc.ch/meetings/session36/p36_doc3_approved_spm.pdf

    And there seems to be no record of this change in the “differences” document that IPCC member countries signed off on during the Stockholm session :

    http://www.ipcc.ch/meetings/session36/p36_doc4_changes_underlying_assessment.pdf

    So the point I was trying to make, and the question that comes with it is :
    WHEN exactly was this change in definition made, WHO changed it, under WHICH IPCC procedure, and WHY does it not show up in the “changes” document from the Stockholm session ?

  26. #26 Phil Hays
    Casino Royal
    2016/09/26

    There is a math error in my previous post. When pointing out that a 5 year moving average is better than a single year threshold, I’m off by one. The fifth year is 4 years after the first year, not 5 years later. Conclusion that a 5 year moving average is a better definition is slightly stronger by correcting this error. Please accept my apologies.

  27. #27 Rob Dekker
    United States
    2016/09/27

    Phil, WG1 appears to agree with your suggestion of using the 5-year running mean for projections. Figure SPM.7 shows a 5-year-running-mean of sea ice, so when things cross the dashed line, that shows that a 5-year-mean is below 1MSK.

    But the point is : You don’t have to change the definition of “nearly ice free” for that. In fact, figure SPM.7 was just fine with the ‘final draft’ definition. It showed exactly what you wanted to convey (that the 5-year running mean projects ice free conditions before mid-century for the RCP 8.5 emission scenario).

    So there was no need to change the definition.

    Even more fundamental, “ice free” or “nearly ice free” tells something about the amount of ice. It does not say anything about any time frame, and that is a good thing, since it allows us to add a timeframe independently. For example, you can say things like “if the current volume trend continues, we will see “ice free” conditions by 2016 +/- 3 years” and “the early holocene has nearly “ice free” conditions in September” and “during the early Pleocene, the Arctic was largely ice free in summer.
    None of these things make any sense any more if you add some timeframe (like “5 consecutive years” or “the 5-year running mean”) to the definition of “ice free”.

    If you are not convinced yet, then try to serve a “nearly empty” glass of beer to a customer in your local pub, under the argument that it is not “nearly empty” until after he orders 5 drinks.
    See how that goes…

  28. #28 Russell the Stout
    Obviousville
    2016/09/27

    The answer to “When did the arctic become ice free in summer?” is “The first time it occurred.”
    The answer to “When did the arctic become ice free in summers?” is “The second year it happened.”

  29. #29 Phil Hays
    Signal Processing Geekdom
    2016/09/27

    No need to change the definition, see the “Relativity of Wrong”.

    The current definition isn’t bad, it just can be improved. And is clearly OK for various “Obviousville” sorts of reasons.

    Let me start with a slightly better definition, 5CY. It is better, as it will have fewer false negatives, but isn’t better as will have the same number of false positives. It is better because the spread in decision time is smaller.

    Better is 5YRM. It is better, as it will have fewer false negatives and positives. It is better because the spread in decision time is smaller. It is better because it is closer to switching at the 50% odds of ice free (Ice free as defined as less than threshold) point.

    Still better is a current probability of the ice free September Arctic state. This should give more advance warning that an ice free September is becoming possible, should allow for different action thresholds other than 50%, should have even fewer false positives and negatives.

  30. #30 Phil Hays
    Opps.
    2016/09/27

    I’m not consistent on “positive and negative”.

    5CY. It is better, as it will have fewer false “sea ice free” decisions, but isn’t better as will have the same number of false “sea ice not free” decisions. It is better because the spread in decision time is smaller.

  31. #31 Rob Dekker
    United States
    2016/09/28

    Also interesting is that none of the reviewers from none of the countries involved requested a change in definition after the IPCC SPM final draft version :
    https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/drafts/WGIAR5_FGD_FinalDraftSPMComments.pdf

    Which leaves it as a mystery as to how this change in definition came about.

  32. #32 Hank Roberts
    in the cracks
    2016/09/28

    You’ve never said why you think this is a “definition” — what about this is a “definition” — what is defined by the earlier wording versus the later wording? what line is drawn, what difference in what consequence is apparent to you?

    It seems you believe there’s some red light/green light change that was going to happen the first year, and now won’t happen until the fifth year — but what is it that won’t happen now until the fifth year?

    Has Stoat or someone got a bet going on what year the Arctic will be considered free of sea ice in the summer(s)?

  33. #33 Hank Roberts
    2016/09/28

    I know there’s this sort of thing:
    http://barentsobserver.com/en/arctic/2014/11/expert-predicts-ice-free-arctic-2020-un-releases-climate-report-04-11

    —-excerpt follows—-

    By 2020, one would expect the summer sea ice to disappear. By summer, we mean September. … (but) not many years after, the neighboring months would also become ice-free.”

    Wadhams later clarified that by “ice-free” he didn’t exactly mean the Arctic was going to look like the Baltic Sea in summer. The scientific definition of “ice-free” is complicated. It is basically based on the amount of ice found in a number of grids when looking at the Arctic from space.

    An “ice-free” Arctic, as defined by scientists, would remain full of floating ice in the summer, but the ice would be broken up enough that a ship could push through it….
    —–end excerpt—–

    Link to the scientific definition is in the original.

  34. #34 Russell the Stout
    Far from the Gore Box
    2016/09/28

    My above comment was based on a certain annoyance with widespread behaviors suggesting a belief that the map is the territory. The increased plausibility of commercial shipping is concrete enough for me, so thank you, Hank.

    The first time I became interested in Arctic ice research I assumed the U.S. navy had mapped some of the evidence, and was dismayed to find it classified. I’m unsure if more than the “Gore box” has been declassified; it’s hard to get a straight answer, and I don’t know how much the old data adds to what we have now.
    http://nsidc.org/data/docs/noaa/g01360_upward_looking_sonar/gorebox.gif
    from
    http://nsidc.org/data/docs/noaa/g01360_upward_looking_sonar/background.html

  35. #35 Hank Roberts
    in the cracks
    2016/09/29

    I thought I recalled another round of declassification beyond the Gore Box but haven’t found it.

  36. #37 Phil Hays
    Exxon watching
    2016/09/30

    Ok, not exactly Exxon, but another corporate cheat.

    http://www.wsj.com/articles/disclose-or-not-to-disclose-wells-fargo-woes-shine-light-on-a-knotty-problem-1475161015

    [Paywalled. What’s the problem it shines a light on? Something so public doesn’t need idiot regulations to force disclosure -W]

  37. #38 Hank Roberts
    in the cracks
    2016/09/30

    It’s an ankle-high paywall. Just paste the string into Google:
    disclose-or-not-to-disclose-wells-fargo-woes-shine-light-on-a-knotty-problem-1475161015
    then click on the result from that search.

    —–excerpt—–
    a real-life window on the often-knotty question of deciding when a piece of information is “material” and so must be disclosed to investors. In part, that is because the rules are complex and not always well understood—many observers think materiality can be determined simply by crunching the numbers, but that isn’t always the case.

    Wells Fargo didn’t disclose anything publicly about its “cross-selling” abuses or looming settlement with regulators before the pact was announced Sept. 8—including in its second-quarter Securities and Exchange Commission filing weeks earlier, on Aug. 3. Three Democratic senators who grilled the bank’s chief executive last week now have asked the SEC to investigate whether Wells Fargo misled investors by failing to disclose the issue sooner.

    While the bank’s management had known since 2013 that some employees had created deposit and credit-card accounts for customers without their knowledge, the accounts were a tiny portion of Wells Fargo’s business. The settlement, which included a $185 million fine, was less than 1% of last year’s earnings. The matter was “not a material event,” Chief Executive John Stumpf told a Senate panel last week.
    ——end excerpt——

    You can see the parallels to the petroleum industry.
    Or not.

    [Ah, thanks. I was answering for “do they need to disclose it now?” Clearly, in any sane world, they wouldn’t, since it is public; in the pointless world of pols, lawyers and blame, they will have to waste everyone’s time and scarce resources doing so; and all the people who ought to complain about companies being forced to waste scare resources, won’t.

    I’m a bit confused about the proposed timeline. Clearly WF weren’t going to announce anything to the public about abuses before they knew they existed. As to whether they needed to disclose whilst talking to the regulators; meh; you might just as well blame the regulators for not disclosing it. I have no time for grandstanding pols -W]

  38. #39 Phil Hays
    Exxon Watching
    2016/09/30

    WF knew long before it was public, as 2013 was before September 8, 2016. And good reasons to suspect that the management of WF knew long before that.

    Does that clear up your timeline question?

    [Only leaving where you got the info from; citations are always good -W]

    Is covering up misdeeds always acceptable, even if you get caught?

    [Covering up misdeeds is not “acceptable”, although whether it rises to the level of being interesting in a wider context is context dependent -W]

    Under current law, identity theft is a crime if a person does it. Jail time kind of crime.

    [You’ve lost me there. I’m not paying the kind of attention to this that you seem to be. But before you expend to much energy enlightening me you might wish to inquire why we’re discussing this at all -W]

    Is firing the grunts that created accounts in people’s names without their knowledge and consent enough? Or should the management that knew or should have known take any of the fallout?

    [“or should have known” implies uncertainty on your part absent from your initial sentences -W]

    Is identity theft by a person a crime? [You have stated above that it is. Why are you now unsure? -W] Is it a crime if a group of people (a corporation) does it? [I would assume so. With very few exceptions things-that-are-crimes done by individuals are also crimes if the same things are done by non-state groups (in fact the only exception I know of is trade union immunity) -W] How do you put a corporation in jail? [I assume that deliberate “not thinking”. Of course, you don’t -W]

  39. #40 Phil Hays
    Read #38 for clues.
    2016/10/01

    Citation above.

  40. #41 Rob Dekker
    United States
    2016/10/01

    You guys are venturing off-topic with this Exxon stuff.
    Back to Deliberate Dark Deeds of Definition (of the addition of “for five consecutive years”) in the AR5 WG1 Summary for Policymakers, and various other IPCC documents, here is how the various scientific papers define (nearly) “ice free” :

    Wang and Overland 2009 :
    http://www.pmel.noaa.gov/pubs/outstand/wang3261/wang3261.shtml
    “The distribution of remaining September sea ice for our “nearly sea ice free” definition of 1.0 M km2 is shown in Figure 3d”

    Massonnet et al 2012 :
    http://www.the-cryosphere.net/6/1383/2012/tc-6-1383-2012.pdf
    “The horizontal black line marks the 1 million km2 September sea ice extent threshold defining ice-free conditions in this paper”

    Hezel et al 2013 :
    http://www.the-cryosphere.net/8/1195/2014/tc-8-1195-2014.pdf
    “Sea ice disappearance or ice-free conditions are defined here as when sea ice extent first falls below 1 × 10^6 km2 for at least 5 consecutive years.”

    Stroeve et al 2012 :
    http://onlinelibrary.wiley.com/doi/10.1029/2012GL052676/full
    “the CMIP5 multi-model ensemble mean never reaches ice-free conditions (defined here as less than 1.0 × 10^6 km2), ”

    Need I go on ?
    None of the papers mentions “for five consecutive years”.

    And for good reason. Defining (nearly) “ice-free” as a purely “spatial” metric avoid that you get into “temporal” trouble.

    Nearly “ice free” means exactly that : Nearly without ice. Without time involved.

    Which makes it ever so curious who, when and why IPCC AR5 added “for five consecutive years” to that definition….

  41. #42 Rob Dekker
    2016/10/01

    Hezel et al 2013 DOES mention “for five consecutive years”.
    Other than them, none do.
    Maybe Hezel used IPCC as an authority…

  42. #43 Rob Dekker
    2016/10/01

    Under fig. 3 Hezel et al 2013 also mentions :
    “A horizontal line at 1 × 106 km2 shows the threshold for the Arctic being ice free”
    Which does NOT have the “five consecutive years” attached to it. Seems that Hezel et al is not entirely consistent.

  43. #44 Rob Dekker
    2016/10/01

    Another scientific papers that define “ice free” :

    Kay et al 2011 :
    http://onlinelibrary.wiley.com/doi/10.1029/2011GL048008/full
    “…the year when the first CCSM4 ensemble member became seasonally ice-free (<1 million km2 in September)."

    Note "the year", not "five consecutive years".

  44. #45 Hank Roberts
    in the cracks
    2016/10/01

    Er, how would you prefer to have those words “attached” if not by being defined in the text, as they are?

    I still haven’t figured out what you’re bothered about. What’s the consequence you’re anticipating that’s somehow being put off by waiting for a five year span? Remember it’s one month — September — we’re talking about here.

    You might well argue for defining “ice free” as three consecutive months including September, eh? Why stop at a single month?

  45. #46 Rob Dekker
    2016/10/01

    And another one :

    Mahlstein and Knutti 2012:
    https://www.ethz.ch/content/dam/ethz/special-interest/usys/iac/iac-dam/documents/group/climphys/knutti/publications/mahlstein12jgr.pdf
    “only for sea ice area greater than 1.0 million km2. This threshold will be referred to as nearly ice-free throughout the paper, since the Arctic is largely ice free even though some
    ice remains north of Greenland and Canada”

    They just keep on coming, don’t they ?

  46. #47 Rob Dekker
    2016/10/01

    Dear Hank,
    As even Phil above admits, the difference between “ice free” and the current IPCC definition of “ice free for at least 5 consecutive years” is AT LEAST 2 decades.

    Isn’t that convenient for the fossil fuel industry ?

  47. #48 Rob Dekker
    United States
    2016/10/01

    Hank said “You might well argue for defining “ice free” as three consecutive months..”

    Didn’t you read the argument I made ? :

    Defining (nearly) “ice-free” as a purely “spatial” metric avoid that you get into “temporal” trouble. Nearly “ice free” means exactly that : Nearly without ice. Without time involved.

    [I still don’t understand why this is quite so exciting. “ice free” == “1MSK” is a semi-arbitrary but convenient idea that people are using for the moment. But its more of a political concept than a scientific one. Nothing very interesting happens at 1, as opposed to 1.1 or 0.9. Or even 1.5 versus 0.5. Its a marker. But likely, as we get closer to it, other things will turn out to be more interesting markers. Given that, the “one year or five” is… a change, yes; but a little-remarked change. Will it turn out to be used elsewhere? Only if it turns out to be useful, not otherwise. AR5 doesn’t even use it consistently -W]

  48. #49 Phil Hays
    Bored with the base topic
    2016/10/01

    Dr Connolley correctly points out that the threshold level is semi-arbitrary but convenient. This level doesn’t have a meaning in the lives of almost anyone, as Russell has pointed out. So is the time period, as Hank has pointed out. All of those are correct, simple and good points.

    My point is a bit harder to make and more subtle. A single day, or month of ice free provides only a little information about the climate of the Arctic. A single event is more weather than climate. Is your concern about Arctic weather, or about climate change in the Arctic?

  49. #50 Hank Roberts
    in the cracks
    2016/10/01

    > the current IPCC definition of “ice free for at least 5
    > consecutive years” is AT LEAST 2 decades.
    > Isn’t that convenient for the fossil fuel industry ?

    No. As, hypothetically, a shareholder, would you want your chosen industry to rush its equipment into an area before it’s going to be predictably safely free of ice year on year, long enough to be useful.

    Inconvenient to have to put that off by a few decades.
    Might prove pointless to go there at all, by then.

    That would be good news, eh? Delay is good, there.

    Yeah, they’re going to be stupid and go there anyhow:
    http://www.nytimes.com/2015/08/30/world/united-states-russia-arctic-exploration.html

  50. #51 Hank Roberts
    in the cracks
    2016/10/01

    http://onlinelibrary.wiley.com/doi/10.1002/2016GL070067/full

    How predictable is the timing of a summer ice-free Arctic?
    First published: 14 September 2016
    DOI: 10.1002/2016GL070067
    Abstract

    Climate model simulations give a large range of over 100 years for predictions of when the Arctic could first become ice free in the summer, and many studies have attempted to narrow this uncertainty range. However, given the chaotic nature of the climate system, what amount of spread in the prediction of an ice-free summer Arctic is inevitable? Based on results from large ensemble simulations with the Community Earth System Model, we show that internal variability alone leads to a prediction uncertainty of about two decades, while scenario uncertainty between the strong (Representative Concentration Pathway (RCP) 8.5) and medium (RCP4.5) forcing scenarios adds at least another 5 years. Common metrics of the past and present mean sea ice state (such as ice extent, volume, and thickness) as well as global mean temperatures do not allow a reduction of the prediction uncertainty from internal variability.

  51. #52 Rob Dekker
    United States
    2016/10/02

    Hank, what I meant was that it would be good for the fossil fuel industry and climate science deniers if an “ice free” Arctic can officially (by the IPCC) is declared 2 decades later.

    William, I understand you are not too excited that this re-definition made it through to AR5. But contrary to your assertion, it has been done pretty consistently in AR5 : Every mention of “ice free” in the SPM, the TS and the full WG1 report has been changed to add “for at least five consecutive years”.

  52. #53 Vinny Burgoo
    2016/10/02

    Rob Dekker, the final drafts of chapters 11 and 12 (dated June 2013) defined a nearly ice-free Arctic Ocean as one where ‘sea ice extent [is] less than [a million] km2 for at least five years’. Those were, I think, the drafts taken to the Stockholm meeting. If so, all that happened was that some quibbler changed the wording to make it totally clear that these were consecutive years and that the revised wording should also be used in the Technical Summary and the SPM.

    You and others have said that this isn’t the usual understanding of what is meant by the Arctic Ocean being nearly ice-free but it looks like AR5’s estimate of when it would likely be ice-free (2040-2060, AKA 2050) was based on the method used in Massonnet et al, and I think that study’s equivalent estimate (2041-2068) used five consecutive years – or five consecutive years of a five-year smoothed mean, anyway.

    If I’ve got that right – and I don’t have the patience (or noodle) to delve into such things very deeply, so you’d better have a look yourself – then they had no choice but to use a definition that included ‘five consecutive years’ or something similar because that is what AR5’s 2050 estimate was all about.

    If I’ve got it wrong – well, yes, it looks like Big Spandex has been up to its tricks again.

  53. #54 Hank Roberts
    in the cracks
    2016/10/02

    > if an “ice free” Arctic can officially (by the IPCC) is declared

    Wait, is the IPCC empowered and expected to make such an official declaration? Since the IPCC report is based on published science, and comes out one to five years or more after the scientific publication, it’d be rather a late declaration, even if they could and did.

    Why and how could the iPCC make any such official declaration?

  54. #55 Rob Dekker
    United States
    2016/10/04

    Vinny, Massonnet et al states :
    “The horizontal black line marks the 1 million km2 September sea ice extent threshold defining ice-free conditions in this paper.”
    It says nothing about “5 consecutive years” and neither does the data indicate that (I think William already pointed out that mistake).

    So it seems highly unlikely that somehow Massonnet et al caused the IPCC to add “for five consecutive years” to the definition of “(nearly) ice free” in a dozen places to the IPCC WG1, two places in the TS, and even two places in the Summary for Policy Makers.

    Something else happened and it was NOT caused by Massonnet et al.

    Whatever it was that caused the IPCC to change definition, it did NOT leave a trace in the “changes” document that was supposed to keep the various documents in check :
    http://www.ipcc.ch/meetings/session36/p36_doc4_changes_underlying_assessment.pdf

  55. #56 Hank Roberts
    in the cracks
    2016/10/05

    So, are you making this as a “tipping point” argument? Is there something you think will irrevocably change because something happens either once, or for five consecutive years? Who is empowered to do what, based on this, that bothers you?

    The eight lowest minimum sea ice extents during this period have occurred in the last eight years.
    — The State of the Climate in 2014

  56. #58 Rob Dekker
    United States
    2016/10/08

    Hank, you are missing the point entirely.
    Did you not read the posts from above ?

    The issue is two-fold :
    First, by adding “for at least five consecutive years” to the definition of “(nearly) ice free”, the IPCC postponed when the Arctic can be called “(nearly) ice free” by a whopping 2 decades or more. Even Phil Hays’ analysis confirms that.

    Secondly, this change of adding “for a least five consecutive years” appears in the AR5 IPCC documents without any discussion or explained reason nor any documentation.

    Not to mention that in the context where it is used, it is actually incorrect (as William already explained).

  57. #59 Hank Roberts
    in the cracks
    2016/10/08

    And you’re missing the reply point — asking you why you care and what difference it makes.

    If you’re simply proofreading the Internet for errors and omissions, more power to you.

    If this — you call it a redefinition, I call it making the obvious explicit — has any consequences for anything related to climate change, I’m most curious to know what threshold or trigger or regulation you’re thinking will be an issue for this.

    [I think we’ve now gone round this circle at least once, and possibly twice. You simply don’t agree. Time for someone to not have the last word -W]

  58. #60 Hank Roberts
    2016/10/08

    P.S.
    > postponed when the Arctic can be called “(nearly) ice free”

    No, because it is either (nearly) ice free, or it isn’t, in September.

    You can’t say the Arctic is (nearly) ice free any other month of a year, even if it was (nearly) ice free during the most recent past September.

    Get it? You sail your boat out there, you either hit ice that stops you, or you don’t.

    If it’s November or December and you rely on having read that the Arctic is (nearly) ice free, you’ll be making a titanic error.

    Map.
    Territory.
    Do not conflate.

  59. #61 Vinny Burgoo
    2016/10/08

    Arnell redux?

    No thanks.

  60. #62 crandles
    2016/10/10

    Environmentalist in 2045 or whenever sea ice is first below 1m km^2: Ooooh look, the Arctic Ocean is nearly ice free!

    Denier: Actually no, it will be at least 4 years and probably more like 20 or more years before Arctic Ocean is ice free (per IPCC definition).

    Environmentalist: Oh, err, that is actually correct so I cannot argue with that.

    Doesn’t seem like an ideal way for such conversations to go. But is this important? Almost certainly not, and definitely not if the definition is going to evolve.

    Potentially more important would be if there was some lesson(s) to learn about IPCC processes and how to avoid allowing them being by-passed or whatever. However, not sure what, if anything, went wrong so possibly no lesson(s) to be learnt. So investigating what happened could well be not worth the effort.

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