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Comments 48601 to 48650:

48601. Kevin8233 at 03:12 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Dikran:

       I would however point out that to get back to five million km^2 would require around the largest annual increase in sea ice seen in the satelite record, which seems rather unlikely as the trend in winter sea ice extent/volume are still downwards.

       I believe we just had exactly that.  And no, I don't believe that a record freeze means the downward trend is over.  Is was a record freeze becauseit followed a record melt.

        

48602. Kevin8233 at 03:07 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       John Hartz:

       Re your forecast that 2013 will be a recovery year for arctic sea ice and for future reference, do you like your crow baked or broiled?

       I don't seem to be able to find your prediction.  Is it here?

        

       Phillippe:

       It was clear before the storm that the minimum was going to be extremely low, the storm simply made it impossible to not beat the 2007 record

       Agreed, that was "one" of the other reasons.

        

48603. stonepig at 03:06 AM on 22 February 2013
       In Wall Street Journal op-ed, Bjorn Lomborg urges delay with misleading stats
       

       Somewhere I read reports written by insurance companies regarding the future of global climate changes and that industry. It's about the cost of replacement, not what it is pitted against.

48604. TerryM at 02:35 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Last year the Caa opened up and swallowed the MYI that previously had found a safe haven north of there. This year we could have a repeat of this new avenue for advection and melt or this winter's MYI having slid down from above Ellesmere Island may plug the labrinth of channels.

       My WAG is that the Caa opens again & that SIA, SIE & volume will all fall below this years minimum. If the Caa opens, Arctic ice will find that the only place of refuge is above Northern Greenland, ballancing between advection through Nares Strait or advection through Fram Strait. 

       While it's possible that the remaining ice can evade both traps in any one year, at some point an unfavorable wind or current will ship the bulk of it south.  I 'd consider lingering year round ice in 2033 much less likely than an ice free period in 2013.

       Considering the probability that we'll go into the coming melt season with less volume than last, and that we'll probably have an open Caa like last year, I'd be surprised if any of the metrics were as high as 2012.

       Terry

48605. John Hartz at 02:29 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       @Kevin #26

       Re your forecast that 2013 will be a recovery year for arctic sea ice and for future reference, do you like your crow baked or broiled?

48606. Philippe Chantreau at 02:22 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Kevin, would you care to list the "number of factors" involved in last year's record?

       You mentioned only that one storm. It was clear before the storm that the minimum was going to be extremely low, the storm simply made it impossible to not beat the 2007 record. Considering that this record was not beaten but shattered, I doubt that the storm was that much of a factor. That was also the opinion expressed by Zhang and colleagues from UW.

       Overall the conditions over much of the season were "a mixed bag" (NSIDC's words). In contrast, 2007 had a perfect combination of melting conditions.

       http://nsidc.org/arcticseaicenews/2012/08/a-summer-storm-in-the-arctic/

48607. cRR Kampen at 02:07 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       #27 - "The reason why there are "recoveries" in the observations is essentially "regression to the mean", after an extreme year, you will generally get a less extreme one."

       What physics is behind this?

       There is a severe circularity in this reasoning involving the definition of 'extreme year'. Apart, of course, from the meaning of 'mean' in cases of accelerating trends on dynamical systems.

48608. Dikran Marsupial at 02:01 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Kevin making testable predictions is what science is all about.  However, your two arguments both seem to me to be saying more or less the same thing twice.  The reason why there are "recoveries" in the observations is essentially "regression to the mean", after an extreme year, you will generally get a less extreme one.

       I would however point out that to get back to five million km^2 would require around the largest annual increase in sea ice seen in the satelite record, which seems rather unlikely as the trend in winter sea ice extent/volume are still downwards.

48609. Kevin8233 at 01:43 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       yes, I did mean in millions.  As to why, which is important.

       2012 was very low for a number of reasons, one of which was the storm which dispersed ice.  Doubt that will happen again like that this year.  As I indicated, I believe it will be a recovery year, which happens with some regularity.  Couple the two tegether and there is some pressure to be dramatically higher than last year.

48610. Tristan at 01:42 AM on 22 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       The thing I find difficult to match up in my head is the idea that (judging by the likely ranges) the TCR can be as much as 2/3rds of the ECS.

       A TCR of 2 and an ECS of 3 implies that 66% of the total warming associated with doubling GHG concentrations would have been already realised by the time the GHG concentrations had doubled.

       It doesn't seem plausible.

48611. meher engineer at 01:40 AM on 22 February 2013
       In Wall Street Journal op-ed, Bjorn Lomborg urges delay with misleading stats
       

       what is Accumulated Cyclone Energy?

48612. cRR Kampen at 01:08 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       #24, I might acknowledge your reproach of 'evasion' after you have checked my arguments for disposing with the concept of 'mean' in this case, but not before.

       Interestingy 'The Black Swan' is much a report dealing with this kind of 'argument' leveled against Taleb all the time by people who do not seem to understand the concept involved.

       Your (and Tamino's et al's) statistical approaches have fared pretty well, but we are increasingly looking at a Turkey Syndrome here -> http://www.attaincapital.com/img/newsletters/20111121_Fig1.gif

48613. KR at 01:03 AM on 22 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       Tristan - Quite correct on the three sensitivities; clearly I needed more coffee when I wrote that.

       As to the TCS range, the IPCC AR4 discussion on sensitivities states that:

       Equlibrium climate sensitivity is likely to be in the range 2°C to 4.5°C with a most likely value of about 3°C, based upon multiple observational and modelling constraints. It is very unlikely to be less than 1.5°C.

       The transient climate response is better constrained than the equilibrium climate sensitivity. It is very likely larger than 1°C and very unlikely greater than 3°C.

       ESS as Hansen defined includes ice sheet changes, feedbacks including release of GHG's (such as ocean CO2, permafrost methane, etc). I find it (IMO) a bit more clear to group the different sensitivities by what feedbacks occur over that time period, rather than just the timescale itself. 

48614. Dikran Marsupial at 00:47 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       cRR Kampen You made an clear error in asserting that regression to the mean applies only to Gaussian situations, but when I explained why that is incorrect, your response was to argue instead that in some situations the mean is irrelevant.  While this is technically true, it is also evasion, and I have learned over the years there is little to be gained discussing science where such errors cannot simply be acknowledged.

       Perhaps the easiest way to decide would be for you to provide a numerical prediction for NSIDC September extent, with a credible/confidence interval and we can see how our predictions fare.

       My statistical approach has fared pretty well for the last couple of years, I see no reason to expect a spectacular recovery suggested by Kevin's prediction, but at the same time I rather doubt that Arctic sea ice will vanish as quickly as you suggest either.  

48615. cRR Kampen at 00:34 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       [DM] "... new ice forms accross much of the Arctic during winter, and this is steadily pushed throughout the year towards the Canadian archipelago and northern Greenland throughout the year.  Even when the Arctic is substantially ice free during the summer, this "stubborn ice" is likely to continue to be sufficiently replenished in the winter to last all summer, even when there is regular shipping across the Arctic."
       
       This is simply not true: http://i1340.photobucket.com/albums/o728/OlTom67/cryosat_zpsf2aa8e10.gif (borrowed from a comment under http://neven1.typepad.com/blog/2013/02/cryosat-2-reveals-major-arctic-sea-ice-loss.html ).
       Why would this trend reverse - especially as the albedo feedback kicks in ever more?
       
       [DM] ]"This is simply incorrect, regression to the mean ocurrs in non-Gaussian situations as well..."
       What 'mean'?
       There are situations in which 'mean' is meaningless. Cf catastrophe theory, http://en.wikipedia.org/wiki/Catastrophe_theory .
       Many examples are given in 'The Black Swan' by Nassim Taleb, http://en.wikipedia.org/wiki/Black_swan_theory .
       What does 'mean' mean if you take the mean daily financial volume on Wall Street while knowing that over past half century only ten loose days account for half the total volume of the entire half century and realizing these are the days with true meaning?

       What is the mean melting rate of an icicle on the roof - when it includes its sudden moment of dropping off?

       [DM] "Also, just looking at the data suggests regression to the mean is just what we should expect, extremes in the observations are generally followed by less extreme observations the next year.  Every record low in the data set is followed by a higher extent in the following year.  Why should 2012/3 be any different?"

       
       Again, what 'mean'? To answer your question directly, the chance that 2013 will be different is considerable and actually increases every year - momentarily that is - because the drop of the 'mean' which is really a point value accelerates. Guassian reasoning fails here (and actually forces me to write gibberish like 'a mean being a point value').
       Another reason to suspect relatively considerable chance of a new record in 2013 is simply the fact the total volume of ice in March 2013 will be smaller (again) than it was in March 2013. There is simply less ice to melt. And more heat te melt it, too.
       
       [DM ]"Note that the minimum in 2012 came very close to being inconsistent with last years projection, being only just within the 95% credible interval, which suggests that last years minimum was a very extreme event judging by the long term trend."

       
       No it was not, it was spot on considering the long term trend, which exhibits accelerating ice loss.
       
       [DM] "Note "regression to the mean" doesn't mean that the minimum extent this year can't be lower than in 2012, just that "all things being equal" we would expect it not to be lower."

       
       But not all things are being equal. This year the ocean-atmosphere system contains more heat than it did last year. This given, plus the fact total ice is less now than it was a year ago can only lead to the expectation next minimum will be lower. Only thing to save this is sheer luck e.g. a cool summer with benevolent stratus and winds.
       
       Kind regards/cRR

48616. Dikran Marsupial at 00:25 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Kevin, fair point, everybody should give a credible/confidence interval on predictions, rather than a point estimate.  Note I actually did give a credible interval, so it isn't absolutely correct to say "nobody else has".
       

       5 km^2 +/- .1 is a very brave prediction indeed (I presume you meant millions of km^2, I don't think anyone is quite that pessimistic! ;o), given the inter-annual variability is about ten times larger than this.
       

48617. Kevin8233 at 00:08 AM on 22 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Kevin would you like to add error bars to your prediction, so that it can be unequivocally falsifiable?

       No one else has, but sure, +/- .1

48618. Dikran Marsupial at 23:56 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Kevin would you like to add error bars to your prediction, so that it can be unequivocally falsifiable?

48619. Dikran Marsupial at 23:55 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       cRR Kampen writes From what is that ice being replenished? There is nothing to replenish it!".

       I am not an expert in the physics of Arctic ice, but my understanding is that new ice forms accross much of the Arctic during winter, and this is steadily pushed throughout the year towards the Canadian archipelago and northern Greenland throughout the year.  Even when the Arctic is substantially ice free during the summer, this "stubborn ice" is likely to continue to be sufficiently replenished in the winter to last all summer, even when there is regular shipping across the Arctic.

       "This is no principle in statistics, this is only a principle belonging to gaussian distribution statistics and these are NOT applicable here."

       This is simply incorrect, regression to the mean ocurrs in non-Gaussian situations as well, although the motivation for regression to the mean is most easily justified by considering what causes a random variable to exhibit a Gaussian distribution (summation of a number of component random variables).  If you have a small number of random variables, the sum may not be sufficently Gaussian, but it will still mean that extreme values will be the result of extreme values of the components, and hence you will get regression to the mean.
       

       However, that is a moot point, as Gaussian statistics are appropriate.  Both the model that I use, and I strongly suspect that used by Tamino, assumes the errors of the model are normally distributed, and indeed that looks reasonable from analysis of the residuals.
       

       Also, just looking at the data suggests regression to the mean is just what we should expect, extremes in the observations are generally followed by less extreme observations the next year.  Every record low in the data set is followed by a higher extent in the following year.  Why should 2012/3 be any different?
       

       Note that the minimum in 2012 came very close to being inconsistent with last years projection, being only just within the 95% credible interval, which suggests that last years minimum was a very extreme event judging by the long term trend.
       

       Note "regression to the mean" doesn't mean that the minimum extent this year can't be lower than in 2012, just that "all things being equal" we would expect it not to be lower.
       

       I agree with Walt Meier on this one, the definition of an ice free Arctic is a bit tricky.  It will be functionally ice free (i.e. ships can go more or less where they like, significant decrease in summer albedo) in a matter of decades, but it won't be completely ice free for quite a long time afterwards.  I am sure skeptics will be claiming that the IPCCs predictions were wrong on these grounds long after shipping regularly passes over the north pole!
       

48620. Kevin8233 at 23:46 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       5.0 km^2

       Recovery year.

48621. CBDunkerson at 23:21 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       The arguments for a 'slow down' in ice loss which I have most frequently seen are;

       1. Once all of the thin ice melts there will be a core of thicker multi-year ice which just hangs on year after year.
       2. Most of the volume loss is due to export of thick ice. Once all of that thick ice is gone the volume loss will slow down.

       The fact that these arguments contradict each other indicates that at least one of them must fail. Indeed, it seems clear that both are incorrect. The past few years we have seen huge expanses of thick ice just wither away in days once the thin ice barrier between them and open water is gone... that demonstrates both that this thick ice will not hold out for years on end AND that much of the loss has nothing to do with export.

       That said, land ice which extends out over the ocean or breaks off into it can be MUCH thicker than ice formed from frozen sea water. That kind of 'former land ice' will remain around for decades after all of the 'sea water ice' is gone. So there WILL be a 'leveling off' at above zero arctic sea ice... it will just be a very small amount above zero.

48622. cRR Kampen at 23:11 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       “The predominant ice circulation pushes ice toward those coasts resulting in thick ice that tends to get replenished.” (Walt Meier)

       From what is that ice being replenished? There is nothing to replenish it!

       Reality is the ice on those coasts is also getting thinner, while the last shreds of multiyear ice might – just might – survive for another half year.

       “There is a principle in statistics known as "regression toward the mean," which is the phenomenon that if an extreme value of a variable is observed, the next measurement will generally be less extreme, i.e. we should not expect to observe record lows in consecutive years.” 

       This is no principle in statistics, this is only a principle belonging to gaussian distribution statistics and these are NOT applicable here.

       “ This is because when extremes are reached and records are broken, a number of different variables generally have to align in the same direction to make this happen. ”

       This is not true. Sometimes extremes are reached and records are broken because one single strengthening driver pushes the system that way.

       That is the case here (the driver is known as ‘global warming’ and never forget this pertains primarily to the oceans!).

       Last year’s extreme Arctic ice low was realized during a summer that was in no way remarkable. There was no ‘alignment of different variables’ as was the case in 2007. Moreover, the year of greatest volume loss, 2010, was no remarkable summer either. Those of us focusing on the Arctic Summer Storm of 2012 should realize first that the ice was already far below record levels before that storm moved in, and secondly that 2010 featured no such storm.

       We can realistically start betting on this or one of the coming couple of years for the first ice free Arctic summer. Forget 2034. Really.

        /cRR

48623. curiousd at 20:43 PM on 21 February 2013
       Introducing the History of Climate Change Science
       

       I purchased the text by Farmer and Cook from Amazon. It will be a great "sit down and read" for me. I gather from the threads by rockytom that there are a wide variety of types of courses by which  colleges teach climate science in some form. In the "101" level course we teach in one semester for non science majors, Farmer and Cook is too dense to be the main student text book, but it would be  ideal as a reference for the professor or as an assigned reference for student in - depth study. I am holding a workshop for outstanding  high school physics teachers in March, a workshop that will introduce climate science as enrichment. As part of the workshop I  will recommend Farmer and Cook as an outstanding reference text.

48624. Daniel Bailey at 15:27 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Remember that the bottom-melt contribution to Arctic sea ice mass losses has been increasing over the past several decades as the heat sequestered in the oceans continue to manifest itself in the Arctic.  At 50%+ now, the melt contribution from the oceans has become the full equal of the sun itself.  And all the cloudy days in the world cannot stop that.

48625. Bob Lacatena at 15:23 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       13, Bob W.,

       One possible slowdown -- if the ice were to stay centered at the North Pole, which I don't believe will happen -- is the fact that the closer you get to the pole, the earlier the arrival of winter night. Closer and closer to the pole means less and less time to actually do the melting.  That could result in the leveling you think won't happen.

       But, as I said, I don't think that will be the case.  The ocean currents and other factors clearly tend to migrate and pile the ice along the northern coast of Greenland and the nearby islands.  There is no reason to believe that not only will that trend continue, but even accelerate (as it has this winter), due to the thinner, fractured ice being more mobile.  That scenario would suggest that "the end" will come even sooner and more quickly.

48626. Tristan at 14:49 PM on 21 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       Yes, and if you read my post you'll note that I mentioned all three :)

       Isn't it Transient Climate Response? Maybe both terms are used. I haven't seen estimates quite as high as 3C for TCR.

       Charney/ECS is not 50-100 years though, it's longer than that. It includes the ocean mostly/wholly responding to the forcing.

       I believe Hansen's term for the milennial sensitivity was Earth System Sensitivity

48627. Bob Wallace at 14:46 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Statistics are wonderful tools, but they have to be used correctly.

       Let's ask oursleves why the rate of melt might not flatten out as we approach zero.

       1) Most likely the atmosphere and oceans will be warmer each year.  And that heat will have less ice to melt, less work to do. 

       2) Most likely there will be less albedo with each passing year.  Shriking extent exposes more water and water soaks up heat rather than reflecting it back out.  And with more first year ice there will be a double whammy.  First year ice will likely form more melt ponds (heat absorbers).  And thinner first year ice lets more sunlight through to the water below.

       3) More open water, with shrinking extent, will mean more fetch and increased wave action which will fracture the ice, making it easier to transport into melting temperature water.

       4) More open water is likely to lead to more frequent/stronger summer storms which will both damage and transport ice.

       All of those things are melt accelerating events.  

       Then let's ask ourselves why melt rates might slow as we approach the first melt-out.

       Class?  Anyone?  I just don't know any thing that might work to slow melting.  It might be that we'll see increased cloud cover which would serve to block incoming sunshine, but I'm not aware that there has been a significant increase to date.  

       If there is a physical force which will slow the melt it better make its presence known soon.

       I'm going with an exponential curve.  Actually an exponential curve until right before the end when the line may go verticle.  A melt-cliff.

       The volume of transport out the Fram Straight is staying about constant even though the ice is thinning.  More "extent" is moving through.  And it looks like ice is starting to get shoved into the Canadian Archepeligo channels and into melting water as well.

       I can see a big wind event during the last ice year which over a short, few day period simply shoves the last ice out.  Not saying that will happen.  But I find it more likely than the ice mounting a last attempt to hang on to the bitter end.

48628. KR at 14:06 PM on 21 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       Tristan - Actually, there are three sensitivities that can be considered:

       • Transient climate sensitivity (TCS) over the short term, the first response to a forcing change. Estimated at 1.5-3C/doubling of CO2.
       • Charney sensitivity (50-100 years) that includes 'fast' feedbacks such as water vapor, sea ice, clouds (~50% larger than TCS) - this is what is usually referred to as 'equilibrium sensitivity', the estimate of 2-4.5C/doubling of CO2 discussed in the IPCC reports.
       • What Hansen has termed long-term or equilibrium sensitivity that includes ice sheet changes, ocean absorption/release of CO2, and other feedbacks on the several thousand year time-frame. The equilibrium sensitivity has been estimated at ~6C/doubling of CO2, based upon ice age temperature changes. 

       There are even longer feedbacks, such as CO2 drawdown through weathering of rocks, but those are on the 10's of thousands of year scale. 

48629. villabolo at 12:26 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Amateur's question, will the forthcoming El Nino have any effect on this summer's ice?

48630. Lou Grinzo at 12:11 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Given the forces we've set in motion -- past and current emissions, long atmpspheric lifetime of CO2 (the ultimate "inconvenient truth", IMO), unleashing even some of the 1.7 trillion tons of permafrost carbon (not to mention the methane hydrates), etc. -- it's clear that once we start seeing a Blue Arctic every summer, it will be a "permanent" fixture, with the onset and re-freeze dates being theonly thing worth tracking.  (Plus CO2 and CH4 emissions from the permafrost, Arctic ocean temps, Greenland melt, ...)

       
       As for what constitutes a Blue Arctic, we could argue endlessly about that, with people preferring any one of numerous plausible, defensible alternatives; I prefer to go with the famous US Supreme Court Justice comment about obsenity: I'll know it when I see it.

48631. mandas at 12:11 PM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       To make a proper prediction, you would have to take into account the environmental conditions, which would be virtually impossible to predict.

       But I would like to suggest that, statistically speaking, the curve is more likely to be asymptotic, and would 'level out' as it approaches zero, rather than declining to zero in 2034 as suggested in Cawley's graph.

48632. Tristan at 11:51 AM on 21 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       Charney and Equilibrium Climate Sensitivity (ECS) are the same thing, and it requires many centuries to fully realise.

       Earth System Sensitivity is the whole hog, including such long term feedbacks as albedo change from ice sheet loss. That requires milennia.

       TCR should be the focus, the effects are more immediate (~70 year forecast) and the estimates more precise (you don't have to deal with certain complex dynamics).

48633. Adam H at 11:18 AM on 21 February 2013
       Geologic Time and Climate Change Science
       

       Re 12

       In NH, Holocene interglacial maximum received LESS summer insolation than Eemian interglacial maximum. New paper in Nature (NEEM (Dahl-Jensen et a) 2013) shows Greenland survived this, allbeit shedding half its mass. This means that because the Eemian sea level data are hard to ignore, the WAIS likely disintegrated (at least partially).

       Not sure what the future has in store for WAIS, mainly because no one can know, but the science is progressing as we speak (and it is very interesting...)

48634. Cara Hernandez at 10:56 AM on 21 February 2013
       There is no such thing as climate change denial
       

       James Taylor has followed up on his dishonest editorial of last week with a second editorial based on misrepresenting the very same study. The latest editorial is entitled "As The Consensus Among Scientists Crumbles, Global Warming Alarmists Attack Their Integrity" and can be found here.

48635. KR at 10:54 AM on 21 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       adrian smits - The 2-4.5 C Charney climate sensitivity (mid-term; 50-100 years) includes feedbacks such as water vapor, clouds, climate driven aerosols, sea ice, and snow cover. See Hansen et al 2007 for a reasonable discussion of climate sensitivity and various feedbacks. 

       Of these feedbacks, the largest is water vapor increases driven by temperature, roughy doubling the temperature change from long lived GHGs alone. Aerosols (based on ice core evidence) decrease with warming, as (obviously) do sea ice and snow cover. Cloud feedback represents a fairly uncertain, but small, contribution to feedbacks, based on the evidence so far. 

       And, perhaps more importantly, we have far more evidence (and lines of evidence) supporting total climate sensitivity than we do for some of the components of feedback. If clouds turn out to supply less positive feedback, then perhaps aerosols provide more? Whatever the uncertainties about the ratios of the components, the strongest evidence is for the sum of feedbacks and total climate sensitivity - transient, Charney, and equilibrium. 

48636. L. Hamilton at 10:38 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Back in October, I posted at Neven's a set of predictions for extent, area and volume based simply on Gompertz curve extrapolation. The same method worked reasonably well over the previous 2 years, and expecially so for volume. I view this as a rough null hypothesis for comparison with more elaborate physical models.

       PIOMAS mean Sep 2013 volume: 3,100 km^3

       NSIDC mean Sep 2013 extent:  3.8 million km^2

       CT 1-day 2013 minimum area: 2.3 million km^2

       Naive Predictions of 2013 Sea Ice

48637. adrian smits at 10:16 AM on 21 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       If the actual increase in temperature from a doubling of c02 is one degree celcious without feedbacks and one of the major contributers to additional warming was supposed to be a large positive feedback from clouds. Should not that mean that if clouds only represent a small positive feedback the estimate of additional warming should be adjusted downwards?

48638. Citizen 7 at 08:27 AM on 21 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       I've spent quite a bit of time today studying the two papers in Nature Climate Change on contrail cirrus that Sphaerica so kindly provided as references, and I want to say I really appreciate the insight into how this phenomenon is being discussed by atmospheric scientists. I am also rather intrigued by the way people who inquire about the phenomenon are sometimes treated, even on this list--like they have become misled by an idea that has cooties on it and needs to be batted away, "debunked," in the same way the very notion of global warming is "debunked" by the climate change denialists. No, DSL, books like Merchants of Doubt are not being ignored; various kinds of academics are starting to analyze the process. Denial is a very real psychological/social phenomenon that results when important strands in one's--and one's social group's--belief bubble are being challenged. And of course the "belief bubble" that we all inhabit, which takes for granted assumptions like the notion that our human enterprise must continue to "grow" ad infinitum, is challenged by the discovery that if we keep doing what we're doing, only more and more of it, we're going to shove the planetary system into a new and inhospitable state--so of course there's a lot of implicit climate change denial in the fact that we all keep marching in lock step, even if only certain well-funded think tanks are generating the explicit kind of denial that you're trying to challenge on this website.

       But there are multiple other layers of denial as well, "new rules" and new realities that we don't want to face--climate change almost seems to be one of the easier ones, especially since it's getting to be more and more "in our faces" all the time, but we're going to have to penetrate all of them eventually.

       I gather from the papers in Nature Climate Change several things about what is being called "aviation-induced cloudiness," which apparently can result from two different mechanisms, the fanning out of ice crystals from aircraft contrails into high, cirrus-like clouds, and also aerosols of soot and other particulates emitted by aircraft that could serve as nuclei for ice crystals. Modeling the effects of contrail formation and spread demonstrated that spreading "contrail cirrus" clouds increase radiative forcing by a considerable amount--a net globally of 37.5 mW per square meter, and up to 300 mW per sq m over the eastern U.S. and central Europe. Boucher goes on to say that "overall, and despite their short lifetime, contrails may have more radiative impact at any one time than all of the aviation-emitted carbon dioxide that has accumulated in the atmosphere since the beginning of commercial aviation." That sounds to me like a pretty significant statement, even if aviation is only responsible for "an estimated 2-14% of anthropogenic climate forcing." It sounds, in fact, like an important item to throw in the mix if you come across people concerned about what they're seeing in the sky, to get them concerned about climate change, instead of making fun of them.

       Boucher notes that "both ground- and satellite-based cloud observations have suggested a small but noticeable increase in regions of high air-traffic density." And Burkhardt and Karcher specifically identify the southeastern U.S. is as having "coverage" by the young, linear contrails of up to 1%, the highest figure given for that kind of cloud. I happen to live in the southeastern portion of the U.S., and I know what I see in the sky now is qualitatively and quantitatively different from what I saw only a few years ago, when contrails might be seen sometimes but never 10, 12, 15 of them lining up from horizon ro horizon, or fanning out into herringbone patterns of cirrus to cover half the sky and more.

       On the "chem trail debunking" website, old photos are being presented purporting to show that "it's always been like this"--that's crap, and I greatly resent this Orwellian attempt to rewrite history. There may be a few photos of such things appearing now and then, going way back--I did see short, transient contrails from time to time as far back as I can remember--but the kind of huge, dominating formations that I see now, no--that would have been a very occasional thing, if it ever occurred. I grew up in and around the "picture postcard" St. Pete beaches before there were condos lining every shoreline, and if there had been lots of contrails crisscrossing the skies they would have stood out like a sore thumb. In contrast, there are some mornings these days when I feel like I'm living in some kind of Stephen King novel--"under the dome" of "aviation-induced cloudiness," of whatever cause.

       So to me, someone who with great emotion flat-out denies that there's anything different going on in the skies today, at least where I live, is engaging in something very like climate change denial. There's a certain belief bubble that will apparently be threatened if some new information is admitted. And that doesn't seem very scientific to me at all--rather, it's a clinging to the "old paradigm," as Thomas Kuhn describes, and reinforced by a kind of groupthink--you don't want to believe something, and the people you talk to don't want to believe it either, so you all reinforce each other's erroneous but deeply held beliefs--it works to keep thoughts of climate change tidily at bay, why not other discomfiting thoughts? The same kind of denial seems to mark the reluctance of the scientific community to weigh in on the physical events of 9/11--instead of "debunking" the truly incredible standard explanation and asking what happened to all that mass, there are gatekeepers like Michael Shermer working hard to "debunk" the questions that are raised. When we start finding the courage to deal with that whole ball of wax, maybe moving on to tackling climate change won't seem so hard to do.

48639. CBDunkerson at 07:52 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Note that the 2012 maximum volume is barely higher than the 1979 minimum volume. Also that the August and October volume figures are just a hair higher than the September minimums... suggesting that if we hit 'zero' volume at some point in September it will likely only be a few years after that before we start seeing 'zero' volume for three months straight.

       Note: I put scare quotes around 'zero' because there will always be some small amount of Arctic sea ice which is still attached to land or only recently broken off from land until Greenland completely melts out.

48640. Paul W at 07:35 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Since we are most likely seeing the developement of increasing positive feedbacks, I expect that the deteriation in ice volume and extent will exceed the statistical estimates. My guess is 3M km2.

       The other prediction is more weather extremes for the NH than last year.

       I wish I could predict a colapse in public gulibility for contrarian double think but that does seem to be going strong with the majority being only "luke warmers".

48641. DSL at 07:32 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       As for regression to the mean, keep in mind that ASV minimum has exceeded the previous year exactly once in the last decade.  I'm going with 2600 km3 in ASV, 3.9m km2 in extent, and 2.2m km2 in area.  Thickness will spend at least 45 days under 1m average (26 days in 2012).

48642. ubrew12 at 06:43 AM on 21 February 2013
       In Wall Street Journal op-ed, Bjorn Lomborg urges delay with misleading stats
       

       Lomborg says: "Consider hurricanes [or droughts, fires, etc] ... If the aim is to reduce storm damage, then first focus on resilience... better building codes and better enforcement [and, presumeably, SECOND, or last, focus on prevention]".  It sounds reasonable but prevention is needed TODAY to prevent DROWNING tomorrow, not just 'storm damage'.  I think Lomborg's 'dirty little secret' is that prevention measures take 30-40 years to have any effect, thanks to the heat capacitance of the oceans.  You can harden Miami all you want, but without prevention it's still going to float away.  And the WINDOW whereby you prevent that fate is closing NOW.

       Lomborg: "Instead of pouring money into subsidies and direct production... focus on ... research..."  And how much CO2 does research prevent from entering the atmosphere again?  Lomborg here seems not to understand how capitalism works.  First you build the market and THEN the investors come (and hire the researchers, etc).  For example, much of the cost innovation in Germany's solar program is in the supply chain.  How does a researcher simulate THAT development in the lab?  This call to put our faith in the 'X factor' of pure research is just a delay tactic, but in any case works against Lomborg as easily as for him.  Why don't we stop burning fossil fuels until the 'X factor' invents ways to easily sequester CO2?  Lets have our cake and eat it too!  Of course, cap n trade or a carbon tax would be more consistent with capitalism, but Obama's direct support for solar and wind is just an end run around a Congress that will never support those reasonable measures (despite the fact that Republicans invented them).  What Lomborg is really saying is to put alternative energy behind closed gov't research doors, where it'll be 'out-of-sight/ out-of-mind'.  He's saying this despite the fact that that is exactly where they've been for the last 40 years.

       On Lomborg's website, a review of his book, 'Cool-It' says that he "argues that we should first focus our resources on more immediate concerns, such as fighting malaria and HIV/AIDS and... a safe, fresh water supply".  This is astonishing: the reason we haven't solved AIDS is because of those global warming nutcases.  Now I understand those Chevron commercials: "We Agree!  AIDS is going to lose!"  Despite an overwhelming desire to launch into multiple lines of sarcasm, I'm going to treat this astonishing claim as serious.  Seriously, then: Lomborg doesn't want his audience to know that the WINDOW for preventing the worst effects of global warming in the next half-century is closing NOW.  THAT IS WHY there's such a rush on the subject of PREVENTION, among people who take it seriously.  You snooze... and your grandchildren lose.  

48643. michael sweet at 06:22 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       The weather last summer was not especially favorable for melt but a record was still set.  What if the weather is more favorable for melt this year?  I guess 3million km² for sea ice extent.  Hopefully Dr. Meier is right and the melt slows.

48644. Esop at 06:17 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Funny how the deniers are now celebrating "recovery". Does that mean they feel that 2012 was as low as it would go, and 2013 and so on will have more extent , area and volume. Would be great to know. Also, if they could point out why they think that will be the case.

       I feel pretty confident that when the 2012 record is broken (likely before 2015), the deniers will claim that they expected that, and it was due to so and so natural cause.

       Thus, I would really like the deniers to make a prediction. Will 2013/14/15 see recovery or a new record and why/why not.

48645. Daniel Bailey at 06:01 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       Going with Maslowski (I've ridden that horse for 5 years now, why stop?), I'll go with 2750 km³ for 2013 expected September volume.

       My only worry is that I'm being too conservative.

48646. dwr at 05:34 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       4.25m km2, i.e. above last year's minimum, but below the 2007 minimum.

48647. william5331 at 04:39 AM on 21 February 2013
       Reconciling Two New Cloud Feedback Papers
       

       This article is a clear demonstration of the difference between the arguments of climate scientists and climate deniers.  Here all the available evidence is presented before a conclusion is reached and the reader can go back to source and make his own evaluation.  Climate deniers sound like preachers.  Everything is clear and worked out and the conclusions are in no doubt.  In itself, it doesn't proove that the climate scientists are correct but it sure gives one more confidence that they are on the right track (and that they will change their conclusions if contrary evidence is found).  Some of us need certainty in our lives so much that we become religious and become climate change deniers.  It is so much more comfortable than wrestling with the evidence but so much less satisfying.  I wonder if the insane level of PC and lack of "hard" subjects in our schools is partially to blame.  We no longer study euclidian geometry starting with SAS and ASA and building the whole structure from scratch.  There are no longer any winners and loosers and competition is to the bottom instead of to the top.  It's not cool to be the top student any more.

48648. dana1981 at 04:01 AM on 21 February 2013
       In Wall Street Journal op-ed, Bjorn Lomborg urges delay with misleading stats
       

       bjchip @7 - the original article is linked in the greenbox at the top of the post.

48649. Philippe Chantreau at 03:20 AM on 21 February 2013
       2013 Arctic Sea Ice Extent Prediction
       

       FYI Dikran, Tamino also just took a look at the Cyosat/Piomas comparison and has plotted the differences. Interestingly, contrarian delirium set aside, this winter shows a pretty low volume; last year, a similar low volume led to the staggering record we remember, so the likelihood of being closer to last year's value than to the mean may be significant.

       Robinson's imagery is of superb quality but scary by the astounding loss it shows. We are now so close to zero in summer minimum that is hard to imagine we won't hit a September ice free Arctic before 2030.

       Imagine the first team working on these data when satellite were launched in 1979. Now, some dude comes around and tells them: "From these data and others', you're going to see an 80% loss of ice volume over the next 30 years." No doubt they would have laughed. Indeed what phenomenon could possibly be powerful enough to cause what is best described as a geological scale event?

48650. Chris G at 03:01 AM on 21 February 2013
       In Wall Street Journal op-ed, Bjorn Lomborg urges delay with misleading stats
       

       Here is an analogy: 

       What would it have cost to, say, discourage increasing wheat production in west-central America in the years leading up to 1933? 

       What did the dust bowl cost America?

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