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Kevin O'Neill
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Rob, when I started posting FDD graphs on the forum last fall I made note that the DMI N80 data is not a perfect proxy, but if anything it is probably conservative.
Toggle Commented Mar 16, 2017 on PIOMAS February 2017 at Arctic Sea Ice
Rob: "Where do I find FDD for (many) Arctic winters past ?" Rob, they can be easily calculated from any temperature dataset. I've used the DMI N80 data to produce the FDD charts that I've posted. Reanalysis can be used to generate temperature data as well and could provide coverage for more than the N80 domain.
Toggle Commented Mar 8, 2017 on PIOMAS February 2017 at Arctic Sea Ice
zebra - I went back and reread this thread just to make sure I wasn't jumping to conclusions based on a couple of ill-written comments. I think you ought to drop the condescension and maybe do some actual work with the physics and daily/monthly/yearly values. Rob Dekker has been one of the few here that has *always* been ready to change his opinion when data warrants it.. Along with Chris Reynolds he is one of the best citizen scientists we have in this community. He has always been forthright in presenting both his data and his formulas. Your self-righteous and condescending attitude stands in stark contrast to what I admire about Rob and Chris. Sorry, but I'm just tired of reading your crap.
Toggle Commented Mar 3, 2017 on PIOMAS February 2017 at Arctic Sea Ice
zebra - I always by habit default to Energy Involved in the Phase Changes of Water to jog my memory for the energy conversions. It doesn't speak of evaporation in this context.
Toggle Commented Feb 7, 2017 on A new Arctic feedback (?) at Arctic Sea Ice
zebra, "You seem to be leaving out evaporation?" I'm leaving out a lot more than that :) These are just back of the envelope numbers. And like albedo there is evaporation taking place now - so the percent it affects the final result is already (partially) included even though not dealt with specifically. We know feedbacks will change and obviously if there is a significant change in the net of all feedbacks, then these results cannot account for them. But to account for every feedback diligently would require a GCM that handles at least handles the arctic very accurately. Perhaps Wieslav Maslowski's regional arctic model could do that, but we know how perilous it has been to trust GCMs on matters related to the arctic.
Toggle Commented Feb 7, 2017 on A new Arctic feedback (?) at Arctic Sea Ice
In the above:"If we diffuse that over the top 200m we quickly drop the actual increase in ocean temperature down to a 0.6 degree. " Should read: If we diffuse that over the top 200m we quickly drop the actual increase in *ARCTIC* ocean temperature down to a 0.6 degree.
Toggle Commented Feb 7, 2017 on A new Arctic feedback (?) at Arctic Sea Ice
I think we're looking at timeframes a bit longer than we might intuitively expect. The long-term trend in volume loss is 0.05 kkm^3/year. As Rob points out in the other thread, this loss incorporates all of the albedo effects to date. It also incorporates any changes in ocean warming, atmospheric warming and all other forcing or feedback changes. Assume that we lose all ice by September 1st, what are the actual consequences? Other than a lot of publicity it really won't change anything. At essentially the very moment the ice disappears it will start refreezing. The year-to-year change won't be much different than we've seen over the past decade. We'll still see thousands of cubic kms of ice formed every winter, but, on average, a little less each year. And again, on average, every year it will disappear a little sooner. If we look at the change mathematically, we are likely to see essentially all the ice melt out when max volume is around 19 kkm^3. Assume the arctic sea area is 12.5 Mkm^2, then an equivalent ocean surface layer would be 1.5 m deep and we would have the potential to raise it's temperature by 80°C if none of it were there at the beginning of the melt season. This is a staggering amount, but it isn't quite as bad as it seems because that's not what would actually happen. Because of thermal diffusion the energy wouldn't be limited to the top 1.5m and it wouldn't all necessarily stay in the arctic. If we diffuse that over the top 200m we quickly drop the actual increase in ocean temperature down to a 0.6 degree. Unfortunately, that would be an accumulative increase each year. Remember, these numbers were predicated on no ice at the beginning of the melt season just to show what the theoretical *potential* heating equivalent of melting all that ice would be - this is not something that's likely to happen, but it shows how dramatic the changes would be with a year-round ice-free arctic ocean. Given this energy budget, a year round ice-free arctic ocean would seem to be a giant step towards a runaway greenhouse effect. Fortunately there seems little reason to suspect that ice will stop forming in winter :)
Toggle Commented Feb 7, 2017 on A new Arctic feedback (?) at Arctic Sea Ice
Glenn, I assume Rob is just looking at the numbers. The most we've ever lost from Jan 31 to minimum is 14.8 kkm^3 (2012) and in recent years the least is 12.1 kkm^3 (2014). In 2016 we lost 14.1 kkm^3. The long-term trend is increasing, but only by 0.05 Mkm^3 per year. The difference lies not in how much we melt so much as it is where we start from. So the fact we're as low as we are pretty much dictates we'll be low in September, but how low depends on the next few months of weather. If we lose the max we've seen in the last decade we'll drop to 1.4 kkm^3. OTOH, if we lose the minimum we've seen over that same period we'll still be at 4.1 kkm^3 and not pass 2012's low record. If we lose the average we've seen over the past decade we'll finish at 2.6 kkm*2.
Toggle Commented Feb 6, 2017 on PIOMAS February 2017 at Arctic Sea Ice
Bill, I've always considered it rude- akin to saying someone is making sh*t up - when one asks for a citation that can be found with a simple Google search. NeilT apparently had no trouble locating NASA's article. I think you also need to bear in mind bifurcation and the *net* effects of solar forcing, Milankovich cycles, and GHG forcing. There can be more than one point of stable equilibrium. Also, the difference between a glacial and interglacial is really rather small. Or, more pertinent, what small percent change caused this?
Toggle Commented Dec 12, 2016 on PIOMAS December 2016 at Arctic Sea Ice
Bill F writes: The planet has spent longer with ice free conditions at the poles than it has with polar glaciation. I think you forget the oft used disclaimer, 'past performance is not an indicator of future results.' Scientists believe Venus was life supporting for 2 Billion years. The main reason is the sun was 30% dimmer. I believe Venus and Earth share the same sun. I.e., conditions in the past are NOT the same as conditions today. Nor are conditions today reliable indicators for tomorrow. In the future we expect the sun's output to increase even more - making a runaway greenhouse effect not only possible - but likely. But that's on a timescale few of use need worry about (a billion years from now). In the past, periods of rapid climate change have wiped out most species on Earth. Humans have not been around long enough to undergo one of these periods. It's easy to imagine humans surviving in some post-apocalypse sci-fi scenario. It's more difficult to imagine us surviving while maintaining the technological, cultural, and societal norms we have developed over the past 10,000 years.
Toggle Commented Dec 11, 2016 on PIOMAS December 2016 at Arctic Sea Ice
Neven, your work keeping this site going is commendable. You might consider using this community's knowledge by accepting guest posts on a regular basis to keep the site active. And I'm sure there's someone you trust here that might even take over moderation duties. Thanks, regardless :)
Toggle Commented Nov 20, 2016 on Sabbatical (I hope) at Arctic Sea Ice
Wayne's website is listed in the side blogroll: Wayne Davidson's EH2R. The first post I remember him writing on this year's Tanspolar Stream 'liquefaction' was Transpolar Stream Current is now a free flowing sea river with broken sea ice all the way to the North Atlantic back on Sept 4th.
Toggle Commented Oct 10, 2016 on The 2016 melting season in images at Arctic Sea Ice
Witold writes: "Unfortunately with single cutoff used to define the state of ice it is difficult to derive good measure. We would have to take strong assumptions on the density distribution of the ice, that would be wrong most of the time due to the high variance due to weather conditions, day of the year etc." I understood this as Wayne's point all along. In fact, I've used the same argument at Tamino's. At Tamino's I added in the fact that the 'pole hole' is assumed to be 100% ice covered. This may have been true in 1979; it's not true today. The distributions may bias measurements high today vs yesteryear, the 'pole hole' assumption obviously biases measurements high. Tamino - much as I usually respect him - assumed I was a denier and basically called me an idiot. Of course he did not rebut either argument -- because you can't :) The most one can say is that the area of the pole hole is relatively small - but it *still* biases measurements high today vs yesteryear. I do not blame scientists - I blame people who fixate on extent. A holistic view of the ice - e.g., taking into account area, extent, volume, and compaction - is going to lead to a better perspective. The main purpose behind still using extent is to provide an historical context, but if that context is misleading, then of what use is it? Well, it gives us something to talk/argue about.
Toggle Commented Sep 18, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
Rob Dekker writes: "Maybe sea ice "area" is a better metric than "extent" for the sort of analysis that you and wayne are suggesting." I think you're missing the point. If we want to compare two periods we want an appropriate comparison; i.e, apples-to-apples. If we know there are discrepancies that the comparison does not take into account we should either attempt to correct them or heavily caveat the comparisons. Blithely assuming that the measurement process has not changed therefor the comparison is apt is wrong. It's the assumption that the comparison is apt that is the problem - not whether another metric is more or less apt. We *want* useful comparisons for historical reasons, but at some point we have to assess whether systemic changes invalidate or significantly affect the comparison; i.e., does it become misleading. It is unclear to me that area actually offers a more valid comparison. If it did, I think scientists would use it instead of extent. Extent may be the best metric we have - that doesn't imply that the process results are immune from a growing systemic bias.
Toggle Commented Sep 10, 2016 on PIOMAS September 2016 at Arctic Sea Ice
wayne writes: "I believe the old 15% rule was designed greatly for a periphery analysis at the edge of an existing huge pack ice area largely surviving the summer. Now the Pack is collapsing within." Yes, this is exactly the same thing I wrote (not having read wayne's comment yet) about the marginal ice zones. The marginal ice zones used to be on the periphery of the pack. Now they're just about everywhere.
Toggle Commented Sep 9, 2016 on PIOMAS September 2016 at Arctic Sea Ice
Rob Dekker writes: "Also, regardless of the level (15% or 20% or 30%), if the same threshold is used for all historic data, you can make a fair comparison between years. And that is exactly what NSIDC data provides." This is the standard response, and for some metrics it is a valid response, but for some measurements it is totally inaccurate. Essentially it is only valid when *all other variables are equal.* Now, would anyone like to make *that* particular claim? The two most important factors that I can see off the top of my head are the distribution of ice by concentration and the variance of same. In high concentration regimes an error of 15% is not going to change anything. In low concentration regimes it can change alot. One need only consider how the 'pole hole' is treated. I believe it is assumed to be 100% -- because that made sense 40 years ago. Does it make any sense *this* year? We are suddenly no longer comparing like-to-like, but actually introducing error by using an unchanging metric. When marginal ice zones make up a small percentage of the overall extent, then the arbitrary threshold is of little importance, but in years where the marginal ice zones are widespread, then the arbitrary threshold becomes misleading. It is mistaken to believe that any arbitrary threshold allows one to compare the past and present given the other changes that have taken place.
Toggle Commented Sep 9, 2016 on PIOMAS September 2016 at Arctic Sea Ice
Wayne, a full description of the model can be found here (free access): Modeling Global Sea Ice with a Thickness and Enthalpy Distribution Model in Generalized Curvilinear Coordinates, Jinlun Zhang and D. A. Rothrock "The model biases are within 8% in Arctic ice motion, within 9% in Arctic ice thickness, and within 14% in ice extent in both hemispheres. The model captures 56% of the variance of ice thickness along the 1993 submarine track in the Arctic. The simulated ridged ice has various thicknesses, up to 20 m in the Arctic and 16 m in the Southern Ocean.
Toggle Commented Sep 3, 2016 on 2016 Mega-Dipole at Arctic Sea Ice
Over on the Forum Gray-Wolf writes: "This year we may be watching this slow evolution at play and some folk might find they need 'update' their current understandings of the working of the basin ( I know none of us know it all but some long held beliefs might be falling by the way side?)." This is in keeping with wayne's latest comment. It's wise to remember that this is not your grandfather's arctic. It's not your father's arctic. And, if you're old enough, it's not even the arctic of your youth. We are primates that excel at pattern-matching. While this is generally a very good trait, it can also mislead us. This is especially true if we're unable to understand that -- as the financial disclaimer goes -- "Past Performance is Not Necessarily Indicative of Future Results..." When you're in unknown territory extrapolating from past performance becomes especially problematic. Given enough time and/or imagination we can always find an analog somewhere in the past or a reanalysis dataset or a GCM ensemble. The question is how appropriate is the analog for prediction? As regards 2016 specifically the main questions that I see are: Was the June stall in SIE a physical reaction to the early losses (negative feedback)? Was the stall unrelated physically to the early season losses, but just the result of random weather? Or was the June stall simply non-existent; i.e., the manifestation of early season losses do not show up in SIE in June, but will be seen later in the season? The answer as to what to expect going forward in the melting season depends largely on the correct answers to the questions above.
Toggle Commented Jun 19, 2016 on 2016 melting momentum, part 1 at Arctic Sea Ice
Chris, I agree that there were some rather cavalier attitudes expressed. You and I discussed last year (or perhaps 2014) on your blog the possibility that we've reached a 'floor' in PIOMAS volume. That since the the negative feedbacks increase as Sept. minimum SIE decreases, we may reach (may have reached?) a point where the negative feedbacks equal the positive feedbacks and the result slows and even the linear trend is no longer appropriate -- much less non-linear trends that accelerate the volume loss. Of course the difference between yours, mine, and Rob's positions can probably be encapsulated on a chart with a total difference of a decade or so as far as the end result. I'm rooting for the quick result, but cognizant it's just as likely the longer one. No bets here :)
Toggle Commented Jun 12, 2016 on Crisis in the Cryosphere at Arctic Sea Ice
In the preceding comment the sentence "Global warming introduces a trend of less and less snow." doesn't really convey what was intended. It should read something more akin to: Global warming introduces a trend in maximum snow cover and a trend in it's disappearance. I can even argue with that characterization, but at least it's closer.
Toggle Commented Jun 12, 2016 on Crisis in the Cryosphere at Arctic Sea Ice
Chris and Rob, you seem to be arguing past each other. Just break it down to basics: NH snow cover typically melts from south to north. This indicates it's a result of the annual seasonal cycle; warming temperatures synchronous with growing insolation as winter transitions to summer. Global warming introduces a trend of less and less snow. This is the same phenomena we see with NH hemisphere lakes. Later onset of ice and earlier disappearance of ice. This has been changing for decades. That last statement is important. Lake ice data shows this effect has been occurring since long before the relatively recent declines in SIA or SIE. Thus, the premise that declines in sea ice cover are the primary driver for reductions in NH snowcover is unconvincing. Approaching the problem from the other direction, we know that temperatures over ice and snow are going to be colder than those over land or water free of ice or snow. While this is the basis of the albedo feedback, it typically has little effect on snowcover near the newly opened seas. The two primary reasons are the temperature of the newly opened seas (near or below the melting point of snow initially) and the minimal heat capacity of air. There is a tertiary reason: even when ice cover is removed we'd still need consistent or persistent offshore winds for any effect to materialize. Having said this, reductions in sea ice cover could change synoptic weather patterns. This is the basis for 'Warm Arctic Cold Continents' which relies on a rapid advance of snow cover in the fall/winter. Unfortunately (for this discussion and for knowledge in general) the recent decline in sea ice cover has occurred in too short a time period for us to make many statistically significant evaluations. We *know* that reduced sea ice cover has to affect the weather -- at least locally, if not regionally and globally. What we don't know is exactly how this will manifest itself and what the range of variation is or can be. My own surmise is that by the time we do have statistical significance it will be a post-mortem discussion.
Toggle Commented Jun 12, 2016 on Crisis in the Cryosphere at Arctic Sea Ice
Regarding a runaway greenhouse vis a vis Venus: As Wayne said, Hawking was likely talking of geological timescales - and even at those timescales we're not talking 10s or 100s of thousands of years - but hundreds of millions. As Hansen has explained: "Earth can "achieve" Venus-like conditions, in the sense of ~90 bar surface pressure, only after first getting rid of its ocean via escape of hydrogen to space. This is conceivable if the atmosphere warms enough that the troposphere expands into the present stratosphere, thus eliminating the tropopause (see Fig. 7 in our paper [Climate sensitivity, sea level, and atmospheric CO2], causing water vapor to be transported more rapidly to the upper atmosphere, where it can be dissociated and the hydrogen can then escape to space. Thus extreme warming of the lower atmosphere with elimination of the cold-trap tropopause seems to be the essential physical process required for transition from Earth-like to Venus-like conditions. If Earth's lower atmosphere did warm enough to accelerate escape of hydrogen it would still take at least hundreds of millions of years for the ocean to be lost to space. Additional time would be needed for massive amounts of CO2 to accumulate in the atmosphere from volcanoes associated with plate tectonics and convection in Earth's mantle. So Venus-like conditions in the sense of 90 bar surface pressure and surface temperature of several hundred degrees are only plausible on billion-year time scales." The earth would be uninhabitable for humans long before then, but these are strictly hypothetical worst-case scenarios and it's really unknown if there's even enough fuel to 'achieve' it.
Toggle Commented Jun 2, 2016 on ASI 2016 update 1: both sides at Arctic Sea Ice
Rob Dekker: "...it seems that 2012 (at 3,600 km^3) already crossed Maslowski's boundary." Chris R and I both did the math a few years back and we had 2012 coming up just a few percent shy of an 80% loss. Chris' numbers are here: Go on, say something outrageous
John Christensen: You have made the same mistake that many others have made. Neither Maslowski's original AGU presentation nor the radio interview you pointed to support your claim that he originally said 2013 and then modified it. His AGU presentation (given in 2006) said, “If this trend persists for another 10 years-and it has through 2005-we could be ice free in the summer.” In the radio interview he says, [starting at 16:15] "...if we already have lost probably about 40% volume in the arctic so far if we project this trend ongoing for the last 10, 15 years we probably will hit zero sometime mid next century -- mid next decade, I'm sorry." [ending at 16:33] The NY Times does not give a quote. So it's impossible to know exactly what Maslowski said. But elsewhere I've seen him say as early as 2013, which matches the 2016 +/- 3 years. It also makes no sense that he updated his prediction to 2016 +/- 3 years in 2011; you can find the same prediction at least as early as 2010. Arctic death spiral: Naval Postgrad School’s Maslowski “projects ice-free* fall by 2016 (+/- 3 yrs) which Joe Romm wrote in response to a WUWT article. Here you will also find,"By “ice-free,” Maslowski tells me he means more than an 80% drop from the 1979-2000 summer volume baseline of ~200,00 km^3." Again, this was in 2010.
bobcobbwrites: "The current standard definition for ice-free is extent below 1000 km2...." Sorry, wrong answer. There is no 'standard definition' of 'ice-free.' Maslowski's is the most publicized and prominent scientific prediction of an 'ice-free' arctic. Many people have written about it over the past decade. That others choose to mean something different by 'ice-free' does not impact Maslowski's prediction. And that others ignore his definition speaks to their ignorance, not his prediction. As I said, perhaps you should be more reticent in attacking others unless you already know the context and definitions which they are using. So, a scientist made a prediction ten years ago that the arctic would be ice-free in 2016 +/- 3 years. Are you still completely confident that it won't be? Apparently not as you refused to take the bet.