An icy retreat

Eine deutsche Fassung finden Sie in der KlimaLounge.

175 comments on this post.
  1. Rupert Matthews:

    I wonder if someone can help with a query here. This article and most of the other articles and comments I can find on Arctic sea ice concentrate very much on sea ice extent. But towards the end of the article the author mentions sea ice thickness, but only in passing. Presumably the actual amount of ice up there is measured by multiplying extent by thickness. I would have thought that the amount of ice was more important than either extent or thickness – but maybe I am missing something. So why does nearly everyone talk about extent? Is it easier to measure? Or is there a deeper (forgive the pun) reason?

  2. Paul:

    That ginormous temperature anomaly over Greenland makes me wonder what the melt rates are there this year.

  3. Mike:

    #1 You are missing this (from the text):

    “A much more useful measure for the state of Arctic sea ice is therefore the total sea-ice volume. However, for its estimation one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past. While this will hopefully change in the future because of the successful launch of the Cryosat 2 satellite a couple of weeks ago, at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.”

  4. Lord Soth:

    Thanks for the interesting article Dirk.

    I have really noticed how the day to day weather is having a dramatic impact on sea ice extent. Instead of depending on climate issues, we are looking at the right weather conditions for three to four months of the year, to make the knockout punch on the arctic ice cap.

    2008 has proven to us that we can have significant ice loss in August. 2009 has also proven that unfavorable weather can turn a contender into a dud for sea ice loss, based on extent.

    The important thing to remember is that volume is going down year after year, and 2009 despite its lackluster extent, did beat 2007 and 2008 for lowest volume. And it appears that 2010 will score a knockout punch in regard to minimun volume.

    I would love to get some detailed info on cryosat-2, such as how long would it take to get full coverage of the arctic (even north of 80) for sea ice volume. Are we talking daily, weekly, monthly or seasonal post processing for sea ice volume graphs ?

  5. jyyh:

    No deeper reason needed, as it’s somewhat more difficult to measure anything from orbit than in location. On exchange one gets a large coverage for observations (though not a full one, ask people who know orbitals why is that) Volume is better and harder to measure than extent, that can be measured from orbit quite easily (well people doing that might disagree, the clouds are quite hard to discount sometimes) from refractive properties of ice, but volume isn’t the absolutely optimal parameter either, but for better one one would need also the consistency of the ice (how porous it is) and the core temperature on the onset of melting (which is very hard to measure). F.e. ice that forms when slush ices over is much more porous than the clear ice from the freezer. For volume calculations one needs to know f.e. the underlying ocean temperatures quite well(as ~90% of ice is under water, hence there are buoys sailing in there.

  6. mauri pelto:

    The volume is simply not directly measured. The volume measuring system has been well validated and the results demonstrated as robust, but it has still not been direct. The Polar Science Center at U of Washington provides the daily volume updates, PSC. The extent is visible to all of us in daily imagery and the ability to observe the changes is fascinating take a look at the nearly daily reporting and new imagery provided by Neven

  7. Rosemary:

    Thanks for the clear, accessible and engaging article, Dirk!

  8. John P. Reisman (OSS Foundation):

    #1 Rupert Matthews

    Extent is pretty easy to see and volume or thickness is not as obvious. But simply multiplying the extent by the thickness does not get you where you want to go.

    Reason being, the thickness is different in different areas of the Arctic.

    I have been testing a new page on OSS for Current Climate Conditions for about a month. And though I’m not done making sure everything is working yet, you might as well take a look

    http://www.ossfoundation.us/the-leading-edge/projects/environment/global-warming/current-climate-conditions

    There will be an underlying section in the future to provide more detail and more data products. The Cryo section, at the moment, has the basics, extent, volume, flow and even some forecasting, in case you drive a submarine?


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future – climatelobby.com
    L

  9. Nagraj Adve:

    I believe that Arctic sea ice has thinned by an average of roughly 40 per cent over the last few decades, from an average of ten feet to six feet. What does more current data suggest?
    Nagraj Adve

  10. Eli Rabett:

    The issue with climate studies is not what you got but what you had. Since no one was really doing appropriate measurements 30 or more years ago, you take the records that still exist, dig up and drill new proxys and try and figure what the various things you were interested in were. Same with ice volume and even extent back before the satellite era.

  11. Walt Bennett:

    What catches my eye is the temp anomaly. Plus ten on a sustained basis?

    And surely we admit that we are still in the early stages of the warming.

    Sustained temps above 0*C in total darnkess at the top of the planet?

    With surely much more warming to come?

    Dirk, I’m looking upon the field science and the honest observations of those such as you who spend significant time there, because to be honest the men in computer labs have not succeeded in delivering the message.

    Which is unfortunate because we all agree that “by the time you can see it, it’s just too late.”

    Would you concur with my observation that the arctic is well on its way to becoming substantially warmer for a very long period of time?

    In other words, this trend cannot turn around in time scales meaningful to this discussion due to the inertia of its own accelerating positive feedback loop.

    Would you concur with that?

  12. wilt:

    July is the month when the average temperature in the Arctic is at its maximum. Up till now in July, the daily loss of arctic sea ice has been about 60,000 square kilometers, as compared to about 80,000 in 2008 and more than 100,000 in 2009 or the ‘record year’ 2007. I don’t understand how this would be compatible with the ‘very thin ice’ suggested by Dirk Notz.
    http://wattsupwiththat.com/2010/07/25/sea-ice-news-15/

  13. Lynn Vincentnathan:

    RE

    However, some recent studies indicate that such a distribution of relatively high temperature in parts of the Arctic and relatively low temperature in Northern and Central Europe and parts of the US might become somewhat more wide-spread in the future.

    Drats! I was sort of hoping that the one thin silver thread (no lining, of course) in this AGW debacle/catasstophe would be no more freezes here in the lower Rio Grande Valley, so our tropic plants and garden veggies wouldn’t freeze, as they did this past winter several times in Dec and Jan. Which is unusal, since we only get a killing freeze here maybe once (if twice, then within a few days) about every 5 to 10 years.

    Are there any sources or studies on this, that the strongly negative arctic oscillation (I think that’s what they call it) may become more common in the future?

  14. Thomas:

    We have three easy to understand measures for sea ice. Extent is the most widely used, but a pixel (or grid cell) is counted as ice covered if the estimation of cover is 15% or more. Obviously a system with say 10 cells at 16% coverage has less ice than a system with 5 cells at 100% coverage, so extent can give a misleading indication of ice area. Area would be an estimation of the actual area covered. I think area is probably more relevant for measuring ice/albedo, and ice-atmosheric interactions. I doubt area is that straightforward to estimate, otherwise we would be seeing routine reports of it. Finally you have ice volume.

  15. chris:

    It would be really helpful to have some expert insight into the contribution of the AMO to the very high current Arctic temperature anomalies. There’s no question that the dominant contribution to warming is global warming (!); however to what extent are the extreme effects in the Arctic (which are greater than projected from models) due to a superposition of global warming and enhanced N. Atlantic heat arising from the positive phase of the AMO?

    Earlier studies (e.g. Trenberth and Shea, 2006) suggested that once the global warming effect on SST was removed from the AMO variability, there wasn’t actually very much of a contribution from the AMO (around 0.1 oC to SST in the tropical N. Atlantic in 2005). However more recent analyses support a stronger contribution from the AMO to high sea surface temperatures in the N. Atlantic (e.g. Chylek et al, 2009; Enfield and Cid-Serrano, 2010; Polyakov et al. 2010).

    This seems like an important issue for properly understanding events in the Arctic.

    Trenberth, KE and Shea P (2006) Atlantic hurricanes and natural variability in 2005, Geophys. Res. Lett. 33, L12704
    http://www.agu.org/journals/ABS/2006/2006GL026894.shtml

    Chylek P et al. (2009) Arctic air temperature change amplification and the Atlantic Multidecadal Oscillation, Geophys. Res. Lett. 36, L14801.
    http://www.agu.org/journals/ABS/2009/2009GL038777.shtml

    Enfield DB and Cid-Serrano L (2010) Secular and multidecadal warmings in the North Atlantic and their relationships with major hurricane activity, Int. J. Climatol. 30, 174-184.
    http://www3.interscience.wiley.com/journal/122261152/abstract?CRETRY=1&SRETRY=0

    Polyakov IV et al. (2010) North Atlantic warming: patterns of long-term trend and multidecadal variability, Climate Dyn. 34, 439-457.
    http://www.springerlink.com/content/8415720180780275/

  16. Bob (Sphaerica):

    Question: I recently discovered the North Pole Cam. It’s fascinating beyond belief to me that I can spend a part of my day basically watching the north pole melt in real time using graphs, animated graphics, and even actual north pole time lapse footage. It fascinating and frightening that it’s happening, and it’s fascinating that I can watch. 20 years ago it was amazing to watch the first Gulf war in real time. Now it’s the Arctic.

    The world we are blessed to live in (at least for the moment, if we don’t throw it all away with arrogance and collective stupidity) is truly amazing.

    Looking at previous years of North Pole time lapse footage, it appears that ice begins to refreeze by the end of July or middle of August. Is this true, or just a mistaken impression I have from watching the footage?

    If so, the implication would be that while extent would continue to decrease from the edges, most chances of a very low final minimum would be greatly reduced after July.

    Also, that refers to the surface and presumably surface temperatures. What’s going on underneath? What it the sea water temperature at the actual pole? Is it causing melting from the bottom up at this time of year, or freezing from underneath?

  17. NeilT:

    Over the years I have noticed that Scientists simply don’t want to get into the Extent v Volume v Area debate. Partially because the data for Extent is long term and reliable, partly because it is extremely difficult to calculate volume as the recent IPY webcast showed. When we actually went there and looked at the “old” ice it simply wasn’t there. No matter what the satellites reported.

    Of course there is also the problem that Extent includes areas of sea that are 85% water, which would effectively kill any quality volume assessment using Extent. For that you would have to use Area and the Area figures have been deemed to be less accurate.

    I am much more interested in the first half of the article. At the beginning it talks about the changes in winter. Whilst summer is more “sexy” in terms of reporting the loss of ice, it is the winter (I believe), which is more indicative of the changing climate forced by emissions.

    In the last 2 years much has been said about the “near misses” to the 2007 low. Yet almost nothing (in relative terms), has been said about the fact that winters are growing shorter and warmer. At the same time the ice cycle is growing shorter and the open water cycle is growing longer.

    Whilst it is no surprise, to those who doubt, that we don’t break any records in summer ice melt, in the middle of one of the deepest solar minimums since solar records began; it should be of huge surprise, to those same doubters, that the winters (in the middle of the same solar minimum), are so warm with so little ice.

    If we look at the Sunspots for solar cycles and map it against the , it is no surprise that the breakup is so early in 2002 – 2004. What is a surprise, though, is the W/Msq delivered in 2007 (ok the weather was good but the solar output was low) and the early breakup then.

    However if we look at the ice low in 2005, the winter/spring low in 2006/2007 and the near miss in summer 2006 plus the ever decreasing volume of ice, the lengthening Autumn ice free season and the ever increasing winter temperatures; the 2007 result should not really be a surprise. Either spring, summer, autumn or winter.

    So really something is forcing a change in the arctic which is making it warmer, not just in the summer, not just because of albedo (no sun in the winter although the water is giving back it’s heat), but generally over the whole year. Also not just one year but year after year after year; solar high or solar low.

    Personally that’s my definition of climate change but I do understand we can’t say that until we have tracked it for a few decades. BUT will we even have any summer ice there in a few decades?

  18. Edward Greisch:

    16 Bob (Sphaerica): What is the URL of the North Pole Cam?

    Every decrease in sea ice means we are closer to BP drilling in the Arctic Ocean. An oil well there would be another bad reason to not fight GW.

  19. Greg Robie:

    I’m one of those who watches the extent on a daily basis during the melt season and, more often than not, also do so year around. This year I added http://arctic.atmos.uiuc.edu/cryosphere/ and http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm to my daily ritual of checking the NSIDC graph http://nsidc.org/data/seaice_index/images/daily_images/N_timeseries.png and NOAA’s National Ice Center’s 31 day extent animation http://www.natice.noaa.gov/ims/loop/ak-1mo-loop.html (when the “Near real-time Arctic site was taken down for a while http://quartet.narod.ru/arctic.html ). I find all of these different representations of data on Arctic ice helpful for thinking about the import of the occasional story and blog post about the changes unfolding in the Arctic.

    Latent heat factors strongly into what one needs to watch for/think about, both as the ice reforms in winter, and, as it melts in the summer. This post’s point about the delay in ice formation off Greenland last winter is an example of this. The same will be true for the ice melting this summer: becasue all we can measure on an Arctic-wide basis is the extent, there will be a lag before the extent decline will confirm the loss of volume the Arctic ice cap has experienced due to global warming—particularly in the past decade.

    This year the perimeters of the Arctic ice cap seem to be melting more or less as per the new normal of the last decade. What does appear to be different this year, and is indicative of the lack of volume in the remaining Arctic ice, is the “flows” of 60% – 80% ice extent through the center of the ice cap that the Cryosphere Today site displays. Comparing what is being observed this year with 2007, it almost constitutes a sea change. And this has an impact on the prediction I made here back in May—and posted a graph of on the solstice: http://home.roadrunner.com/~robie/opento/welcome.html .

    I created the curve using Photoshop and the 1979-2000 average. That choice has me as wrong as I currently am because of the role latent heat differently plays in todays ice extent change dynamics depending on whether the melt is occurring at the edges or internally to the ice cap. What happens, on average, at the ice cap’s edges does not apply to how the thermodynamics will play out at the center of the ice cap. In the center of the ice cap latent heat and ice extent decline will interplay over time to yield yet another new normal. Learning from my less-than-completely-thought-through prediction, and as best I can guess now, the new shape of the ice extent decline will be defined by the thermal dynamics created by the eventual impact shortening daylight will have on solar incidence’s contribution the change of phase in an area where ice extent has rarely dropped below 90% in the past.

    The current slope of the ice extent curve is tracking last year’s. This is descriptive of what happens at the ice cap’s perimeter. If the percent of ice extent continues to lower in the ice cap’s center, as it has so far in the melt season, the slope of the curve could steepen significantly in the next 6 weeks. Surface winds will also play a major role in what is observed. Regardless, the amount of open water that is exposed will delay the reformation at the start of the winter freeze. The more diffuse that open water the less its impact (this year); the more concentrated it is, the greater (this and future years). Either way, this year should begin to define a new melt pattern that will be defined the curve of the ice extent loss that leads to late summers with 90% sea ice loss. Such is our near, and maybe very near, future.

    The confusion that is possible when conflating extent and volume as one thinks/feels about future behavior of a substance with the latent heat that water has re its solid/liquid change of phase, can, as it did to me with my choice to use the curve of the 1979-2000 average, lead to too-quick-thinking. Such thinking and its predictions can be more a reflection on ones limited mental capacity and the role motivated reasoning plays in obscuring contradictions; complexity; (and ironically) simple physics and math!

  20. John P. Reisman (OSS Foundation):

    Just a quick note on the temp anomaly over Greenland. The image states it is first half of January, so i don’t think it sustained for very long.

    Here’s the NCDC/NOAA chart for the month of January

    http://www.ncdc.noaa.gov/sotc/?report=global&year=2010&month=1&submitted=Get+Report

    Not to belittle the concern however.

    I forgot about the north pole cams, I used to watch those too.

    I just loaded them in the Cryo section with source links

    http://www.ossfoundation.us/projects/environment/global-warming/current-climate-conditions


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future – climatelobby.com
    Learn the Issue & Sign the Petition

  21. Bob (Sphaerica):

    18 (Edward),

    North Pole Cam

    Amazing beyond belief. Truly. I live in a wonderful age. I can’t believe I didn’t become a scientist myself. I need a do over on life (not really, but you know what I mean).

  22. NeilT:

    I knew I shouldn’t have tried to use html….. :-(

    solar cycle sunspots courtesy of solarcycle24 and the hathaway prediction
    http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif

    Barrow sea ice breakup courtesy of the Alaska Uni sea ice group

    http://seaice.alaska.edu/gi/observatories/barrow_breakup/Melt-out-20100709.png

  23. Pete Dunkelberg:

    Wilt # 12

    How can reality not be consistent with itself?

    The arctic ice is not simply uniformly thin. It is broken with lots of gaps. Whether an area becomes clear of ice depends very much on the wind blowing the ice elsewhere. The net effect depends on whether the ice has been blown to a warmer spot. Look at the graphs provided above, or look at Arctic Sea Ice News daily.

    Around the end of June the wind shifted and the daily reduction of ice extent fell way off. Lately though the graph is running about parallel to the 2007 line.

    The daily Arctic Oscillation graph gives you a first approximation to winds in the Arctic. What it indicates just now is quite modest overall wind in the Arctic.

    What will Arctic weather be for the rest of this summer? The answer is blowing in the wind. But no matter which way the wind blows, CO2 is in the air intercepting long wave radiation.

  24. Bob (Sphaerica):

    12 (wilt),

    What I have gleaned from reading, watching, and keeping an open mind is that we do not have any true way of measuring ice in the Arctic (although Cryosat 2 should get us a lot closer). Extent, area, everything is just a proxy for the amount of total ice in the Arctic, and they are all limited proxies… and even then, it’s just a measurement, not an understanding of a complex system. Extent doesn’t tell you how thick the ice is, or how much ice is really there. Area doesn’t tell you how thick it is, either, and is only a gross estimate of actual area. Any single number doesn’t really tell you what is really there, or what is going to happen.

    In each case, you are looking at wide expanses of ocean with varying amounts of floating ice interspersed. Or, you are looking at sheets of seemingly solid ice of unknown depth and consistency (is it solid ice, or packed snow, or ice riddled with fissures and pockets of melted water?).

    In addition, it is constantly moving. Now you see it, now you don’t. Winds and currents move it around, dispersing or compressing it. It melts from above (air temperature and direct sunlight). It melts from below (water temperature). It freezes. It melts here and freezes there. It’s not an easy, simple thing to measure, especially when you consider the massive area involved, the harshness of the conditions, and that there’s no solid land on which to base a permanent station.

    [Along those lines, the fact that some North Pole Cams seem to fall over or potentially start floating if enough ice melts gives you some pause. 2007 includes images from an icebreaker, but it's unclear from the comments if this was done just because one was handy, or if it was necessary because of the degree of melt involved.]

    So any effort to argue that this year is more or less than that year, because this measurement is more or less than that measurement, is fallacious to begin with. That, I think, is a main point of the original post, that it’s an environment and situation which is difficult to observe and then water down into a single, easy to consume and accept number. Predicting what will happen is just not easy and simple.

    It’s a complex system. A single number which represents “how much” by any measure is just an oversimplified model of a complex system. Models exist for specific purposes, and to use them for the wrong purpose is wrong. What we need to do is to better understand the system, and to improve our measurements. These are the two things that I think scientists working in that area are attempting, and I’m grateful to them for the effort.

  25. Bob (Sphaerica):

    12 (wilt),
    18 (Edward),

    Something that I consider immensely useful in understanding better (from a visualization perspective) what is happening in the Arctic are the animations provided here:

    The Cryosphere Today

    Watch thirty days of melt and shuffle in action. It’s informative.

  26. Halldór Björnsson:

    Re #12.
    Wilt, look at the evolution of sea ice extent this year
    (http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png). You will notice that this summer the decline in extent has been fairly steady (since May). In early July there was a period when the rate of decline seemed to be levelling off. This was concurrent with a cold anomaly devloping in the Arctic. Once that was over, the decline continued. Hence, Dirk’s statement on the sensitivity to weather patterns seems to hold.

  27. Mark Zimmerman:

    in 2007 a relatively stable high-pressure system formed above the Beaufort sea, towards the north of North America, leading to rapid melting of sea ice there.

    Have similar conditions occurred in the past 30 years, other than in 2007?

  28. wilt:

    Pete Dunkelberg # 22

    Thanks for the informative links, and especially for the observation that the outcome is litterally blowing in the wind: the minimum value will be determined by the local weather, especially the direction and strength of the wind (as it was in the exceptional year 2007). It seems to me that in this situation things like AMO are more important than CO2.

  29. Hank Roberts:

    Which navies have submarines operating in the Arctic these days?
    Are any of them, when they have a submarine in the Arctic, providing any data for scientific use on a realtime or frequently updated basis?

    I realize they’re called the ‘silent service’ because they don’t want to be noticed, generally.

    Does anyone know if the Navy’s sea ice publications are based on updated data sets that aren’t available to other scientists, or are delayed?

    (I ask because I remember, when I was a marine biology student for a while in the 1960s, how researchers got their sonar gear from their country’s navy — and each sonar rig had cutouts for particular bands so those scientists couldn’t see their own navy’s submarines. Instead the scientists got together at meetings and swapped data sets a few times a year, and the combined data gave good coverage. Nobody cared about that — it was _realtime_ detection of the submarines that worried the navies.)

  30. Bob (Sphaerica):

    28 (wilt),

    It seems to me that in this situation things like AMO are more important than CO2.

    This is a bait-and-switch. What you are saying is that because there’s wind, and it’s an important factor in the final annual degree of the current, unheard of summer Arctic ice melt, nothing else matters.

    Without CO2, temperatures wouldn’t be warm enough to cause the anomaly and for wind to matter all that much. Yes, certain conditions will tip things further one way or the other, but we wouldn’t be on the precipice of watching summer Arctic ice disappear if it weren’t for dramatic and indisputable Arctic warming. Wind wouldn’t be a factor worth measuring if it weren’t for CO2 and the resulting temperature increase.

  31. jyyh:

    “The arctic ice is not simply uniformly thin. It is broken with lots of gaps.” , this is clearly seen in satellite photos where thicker (and usually older) ice floe takes on wind or current and creates an “open sea wake” on its tail.

  32. John:

    This article mentions air temperature anomalies a lot. It does not mention sea temperatures or currents? What about the contribution of AMO and others? Have any of the relevant cycles/currents changed in recent years and if so what effect is this potentially having?

    It sounds really bad, but when we have only got 30 years of (incomplete) data for a region that fluctuates between no ice and ice swallowing a third of the planet, what are we really watching here?

  33. Lou Grinzo:

    If I may, my page with a lot of these graphs plus some others:

    http://www.grinzo.com/energy/graphs.html

    I semi-regularly update this page, reorganize it, etc. as I become aware of new graphics relevant to energy and climate issues.

  34. Hank Roberts:

    “The summers observed by the North Pole Web Cams were very different. (see table …). The onset of melting is typically in early June, but occurred in late July in 2002, and late June in 2003 and 2004. The Web Cam images show very limited melt pond coverage in 2002, but widespread melt pond coverage in 2003 and 2004. In 2003, the melt ponds were widespread by July 4, but diminished in late July, and then reformed in mid-August. ….”

    Much more: http://www.arctic.noaa.gov/detect/ice-npole.shtml

  35. richard pauli:

    Another important distinction between weather and climate:

    Weather forecasting is a vital service, heavily funded, with reports used by all sectors of business, agriculture, military and personal lives.

    Climate forecasting reports are poorly funded, outdated, actively suppressed by political groups and lack much of an institutional structure in the US. Met office in England is the exception. Few business have discovered the value of regional climate forecasting.

  36. DeNihilist:

    Excellent article. Short, precise, and easily accesable. Thanx.

  37. Bob (Sphaerica):

    28 (wilt),
    30 (myself),

    Actually, I’m going to revise what I said a bit. Wind matters, AMO matters, but it’s not nearly as important temperature, period, and the effect of local (Arctic) weather on temperature.

    Wind and currents shuffle the ice around, which affects measurements of extent, but again, extent is merely a proxy for total ice volume. It may make things look better or worse, by making the proxy larger or smaller, but what really matters is the amount of total melt (and winter recovery in ice volume, again not extent).

    Put another way, one can say that things are no better than is represented by the extent… but things can be considerably worse. This position was presented (and scoffed at on WUWT) by one scientist who said that when the final full summer Arctic melt comes it may be sudden and unexpected. The proxy of ice extent is not what it seems. It’s not volume, it’s not “ice quality,” and it may not even be close

    Do not fall in love with simple numbers and graphs that make a complex world into a simple, predictable place.

  38. Walt Meier:

    Thanks to Dirk for a nice discussion of sea ice conditions and for highlighting NSIDC’s news and analysis site.

    In regards to volume, I will point out a couple things:

    1. We have gotten some volume estimates from the NASA ICESat satellite, e.g.:

    Kwok, R., G. F. Cunningham, M. Wensnahan, I. Rigor, H. J. Zwally, and D. Yi, 2009: Thinning and volume loss of the Arctic Ocean sea ice cover: 2003-2008. J. Geophys. Res., 114.

    Unfortunately, ICESat went out of service last October.

    2. In recent post, we mentioned modeled ice volume estimates at the University of Washington:

    http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php

    These assimilate our sea ice concentration data and then use model physics to track thickness and hence total volume. They’ve shown record low volume since spring. I’m a little bit skeptical that the volume anomaly is so low. One has to keep in mind that these are model estimates and may be subject to some biases. However, the model has agreed well with previous observations and it does provide at least some estimate of volume. Also, while there is less first-year ice and more 2nd and 3rd year ice, which is thicker, compared to recent years, the amount of the thickest, oldest ice (>5 years) has continued to decline. So the volume anomaly may be reflecting that loss of the oldest ice.

  39. Didactylos:

    wilt:

    You are comparing four consecutive years. In climate terms, that is meaningless. Yes, some of the 2010 late winter ice was ridiculously thin, and melted as easily as it formed. But the rest of the single year ice is only thin compared to the long term average. You won’t get anywhere comparing it to very recent years, unless you want to join us in speculating about polar weather conditions.

    Was the entire extent of single year ice significantly thinner than the previous year? That’s the part we needed Cryosat-2 for. Instead, we have to make do with scattered observations. We know more southerly ice was very thin. We know that some areas didn’t ice over until the melt season had nearly begun. And those areas have all melted out long ago, confirming that they were, indeed, very thin.

  40. Douglas:

    Echoing #14. I would think a complementary measure would be area of arctic covered with 85% sea ice. Or 100%. Does anyone plot this? I just looked at NSDIC and didn’t see it.

  41. Bob (Sphaerica):

    I finally hunted around enough to try to find out where the North Pole Cams are actually located, and was pleased to find the following image, showing their changing locations with time… I was not entirely surprised to find that the answer is “it depends on what day you ask.”

    Buoy Drift Track Map

    It serves as an important reminder that, even with the support of the illusion of the steady, continuous images from the pole cams, the Arctic is a fluid, dynamic environment, not a pseudo-continent made of solid ice as the Rudolph Christmas specials of our youth lead us to believe.

    Has anyone considered, proposed, or implemented an “ARGO float” type project for the Arctic? I’d think it would be quite informative to have an army of robotic buoys which could report their locations and status — either resting on ice or afloat, along with air temperature and, if afloat, the water temperature — giving a clear image of how the Arctic surface stretches and morphs over the course of a year.

    It would also help to silence the critics who keep complaining that the Arctic is a huge gap in the temperature record.

  42. geo:

    I am not sure if this has been referenced, for an estimate of volume of ice see:
    http://www.agu.org/pubs/crossref/2010/2010GL042652.shtml

    This will be used to calabrate crysostat

  43. dhogaza:

    Wilt:

    It seems to me that in this situation things like AMO are more important than CO2.

    Please re-read Dirk’s article, in which he explains that higher temps have led to thinner ice, which is more easily blown around than the thick sea ice which covered most of the arctic in the past.

    So in a trivial sense, yes, “things like AMO” are more important for the extent figure, because this impacts how the ice is blown around. However, that ice being blown around is still melting.

    Try this thought experiment:

    Dump a few bags of crushed ice into a swimming pool this summer.

    Use some blowers or fans to push that ice towards one side of the pool. Extent will drop.

    Now reposition your blowers or fans to push that ice away from the side of the pool, spreading it across a wider area. The “15% or more” extent will grow.

    Yet … the ice will still be melting. The fact that the water and the air over the water is warm does matter.

    (in actuality, in the arctic, the extent actually didn’t grow earlier this july, but rather the rate of decline in extent slowed dramatically. But hopefully you get the point.)

  44. pete best:

    I have a question. As Arctic summer sea ice decline is a central prediction of AGW theory can it be claimed that the increased summer sea ice melt and possibly overall its thickness (volume) is in line with these predictions taking into account natural variability of course ?

  45. wilt:

    #37, #43
    ‘Do not fall in love with simple numbers and graphs that make a complex world into a simple, predictable place.’

    Bob, I am trying to avoid the trap you refer to, and I understand and respect the arguments that you and Dhogaza have put forward. And it will probably be a lot easier to discuss this topic once the data from Cryosat-2 have been available for some years. But for the moment I remain unconvinced that overall the Arctic ice is much thinner than it used to be. Let me rephrase my position by formulating two (provocative) statements:
    1. The sea ice minimum in 2008 was above the 2007 value, and 2009 was above the 2008 value. If again 2010 yields a minimum value higher than in 2009, this would not support the hypothesis that we are on the way to a summer-ice-free Arctic (and yes, I realize that it’s only a limited number of years)
    2. In view of the decisive effects of wind and ocean currents, would you agree that the minimum value of Arctic sea ice is more related to weather than to climate? In other words, whatever the outcome this year, neither AGW-proponents nor their adversaries should claim it as a ‘victory’ for their point of view.

  46. Lynn Vincentnathan:

    Another Q sort of related. Someone brought up a terrible cold snap happening right now in Peru (see: http://www.bbc.co.uk/news/world-latin-america-10749124 ), as proof against AGW, of course. I spoke about the difference between weather and climate — to deaf ears, I’m sure.

    But I also went on to tell about our cold spell here in the lower Rio Grande Valley (and elsewhere) this past winter, and how I asked the scientists, and they told me we were in a strongly negative arctic oscillation — with wind bringing cold north to south, instead of the usual west-east pattern. And that the global average temps for those winter months were actually above average a bit.

    I suggested maybe Peru is also experiencing the same type of thing, but what did I know, since I’m not a scientist.

    Does anyone know whether this might also be the cause of Peru’s astral winter’s cold snap this year, and ?? is any part of the antarctic or its nearby oceans well above average ??

    I did find this article on Google Scholar (which I suggested my denialist friend make use of), which seems to indicate against this, but have there been any developments on this since 2004? — http://www.nature.com/nature/journal/v432/n7015/abs/432290b.html :

    Atmospheric science: Early peak in Antarctic oscillation index
    Julie M. Jones & Martin Widmann
    Nature 432, 290-291 (18 November 2004)

    The principal extratropical atmospheric circulation mode in the Southern Hemisphere, the Antarctic oscillation (or Southern Hemisphere annular mode), represents fluctuations in the strength of the circumpolar vortex and has shown a trend towards a positive index in austral summer in recent decades, which has been linked to stratospheric ozone depletion, and to increased atmospheric greenhouse-gas concentrations. Here we reconstruct the austral summer (December–January) Antarctic oscillation index from sea-level pressure measurements over the twentieth century and find that large positive values, and positive trends of a similar magnitude to those of past decades, also occurred around 1960, and that strong negative trends occurred afterwards. This positive Antarctic oscillation index and large positive trend during a period before ozone-depleting chemicals were released into the atmosphere and before marked anthropogenic warming, together with the later negative trend, indicate that natural forcing factors or internal mechanisms in the climate system must also strongly influence the state of the Antarctic oscillation.

  47. Doug Bostrom:

    I remain unconvinced that overall the Arctic ice is much thinner than it used to be.

    Leaving us with the observation and possible problem that ice that is not visible is either nonexistent or is physically arranged in such a fashion that the total amount has not changed yet is no longer directly visible.

    Presumably if Wilt’s implication that no ice has in fact vanished is correct, this means that -effective- sum thickness of the ice is the same, it’s just stacked into extremely tall, vertically oriented slabs projecting far below the surface of the Arctic Ocean. In other words, volume is equal to the past, areal distribution has radically changed. Has anybody observed these features?

  48. Didactylos:

    wilt said: “But for the moment I remain unconvinced that overall the Arctic ice is much thinner than it used to be.”

    Why is this? We lack data, yes – but we’re not as ignorant as all that. Icesat and submarine data show beyond doubt that the ice is a lot thinner now than previously.

    “In view of the decisive effects of wind and ocean currents, would you agree that the minimum value of Arctic sea ice is more related to weather than to climate? In other words, whatever the outcome this year, neither AGW-proponents nor their adversaries should claim it as a ‘victory’ for their point of view.”

    This is missing the point in spectacular style. We can easily discount the year-to-year variation and look at the longer trends. And those are indisputable: ice extent has plummeted dramatically, particularly during the summer (hence having the greatest effect on the minimum extent). So, the real answer to your question is: no matter what happens this year, we are in big trouble. If you call that a ‘win’ for the warmists, then I think perhaps that’s not the most productive way of looking at it.

  49. wilt:

    #47 “Wilt’s implication that no ice has in fact vanished…”

    I don’t know why you are twisting my words, but I do know that it’s making the discussion needlessly complicated. Let us focus on the facts and their interpretation. Facts are that the minimum was higher in 2008 than in 2007, and higher in 2009 than in 2008. We will have to wait and see whether the outcome for 2010 is higher than in 2009 (in my view this is more likely than not). If it is, then those results are not easily compatible with an ice layer that is supposed to get thinner year after year.
    Whatever your point of view, I suppose that any reasonable discussion starts with respect for the facts, and for arguments.

  50. John P. Reisman (OSS Foundation):

    Something to consider, and I had thought about it earlier but did not write what I was thinking.

    One of the current issues is that the multi-year ice was able to build more second year I think that was last year due to natural variability factors. The trend is clear and down but there’s lots of stuff gong on up there.

    I think that the dispersion and changing action of the ice also can trick us. The models are still models and measurements are developing. I’ll be interested to see how things work out with the new satellite.

    With all the complexities, the ice is trending down and doing things that it was not able to do when the pack was thicker and more stable.

    I think it could take at least one more year if weather patterns are nominal to see a more dramatic spike down.

    One of the conflicting bits of data is in between the Navy models and PIOMAS, which shows a dramatic spike down. I wonder if there is an input issue, or resolution issue there?

    The truth may lie somewhere in between. If I were to guess, their might be an ice action issue that is confounding the data collection too. I don’t know, and I’m very interested what the science comes up with this year, that should help refine the understanding of these issues.

    But as has been said before, we are losing the ice. It’s just a matter of time. The changes in the weather patterns if they become more normal especially with the AO, then that and other factors could speed things up, while other factors could slow it down.

    Lot’s to learn and it’s fun to try to figure it out. But the end result is we are dong some rather amazing damage to our planet in relation to our ability to safely interact with those things that have kept us alive so far.


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future – climatelobby.com
    Learn the Issue & Sign the Petition

  51. Didactylos:

    pete best asked: “As Arctic summer sea ice decline is a central prediction of AGW theory can it be claimed that the increased summer sea ice melt and possibly overall its thickness (volume) is in line with these predictions taking into account natural variability of course ?”

    Good question! And the answer is (surprisingly) no. Arctic ice is doing much worse than predicted in the last IPCC report. This is one of those errors that you don’t get to hear about so much.

    In fact, current Arctic sea ice extent is completely outside the range projected by the IPCC models. They didn’t forecast it being this low until 2050.

    Reference figure 13 in the Copenhagen Diagnosis.

  52. Chris Dudley:

    Mauri (#6),

    The updates are not always daily for the Arctic Ice Volume calculated by the Polar Science Center. In fact it was about a month between the last update and the most current one with data through 7/17/2010.

    One should also be careful reading the graph. It is given as an anomaly relative to a 1979-2009 average and the average plot here: http://psc.apl.washington.edu/ArcticSeaiceVolume/images/PIOMAS_daily_mean.png which marks months at their midpoints rather than their beginnings. This may be what caused Joe Romm to incorrectly claim that the ice volume was below 10,000 km^3 on 6/27/2010 http://climateprogress.org/2010/06/27/arctic-sea-ice-extent-volume-record-nsidc-volume/ It does appear to be around 8,000 km^3 now though.

    Basically, the resolution of the graphs is daily but the updates may not be.

  53. Peter:

    Just a question to all- what is, if there is one the lag time in CO2?

    Arctic ice is melting- we know this- but is this in result to the current 392ppm CO2 level- or from C02 levels of 20, 30 years ago.

    Dr. Hansen has said the ice at the poles will begin to melt when CO2 passes 350ppm.

  54. wilt:

    #48 Didactylos said: We can easily discount the year-to-year variation

    If so, why then was the outcome in 2007 not ignored by the warmists? Instead, it was presented as a kind of final proof that Armageddon was about to start. In my view, your desire to ignore all data that do not fit with your theory, resembles the attitude that many warmists had with respect to the global temperatures of the last 15 years (you have probably noticed that by now even respected AGW proponents like S. Solomon use the term ‘flattening’ for the temperatures in recent years).

    [Response: Stop fighting against strawmen. 'Proof of armageddon'? Really? Please stick to substantive points that relate to things that scientists have actually said about this - for instance here, rather than someone's fevered imaginings. - gavin]

  55. Bob (Sphaerica):

    45 (wilt),

    In view of the decisive effects of wind and ocean currents, would you agree that the minimum value of Arctic sea ice is more related to weather than to climate?

    No, I wouldn’t, because of the point I keep making, which I believe is a re-iteration of Dr. Notz position. A quote from the original post above:

    Therefore, only considering a possible “recovery” of just the extent of Arctic sea ice always remains somewhat superficial, since sea-ice extent contains no information on the thickness of the ice.

    Ice extent, as I’ve said, is a mere proxy for actual amount of ice. Changes in extent from one year to the next border on irrelevant, just as changes in global mean temperature from one year to the next tell you nothing of the long term trend.

    I would agree that with the current, grossly abnormal degree of Arctic summer ice melt, which is a clear result of AGW, because it has “loosened” the ice and so seemingly allows it to “move” more than in the past, then the measure of ice extent as a proxy for actual ice volume is very subject to weather patterns. The fact that currents and local weather have such a strong effect on overall extent is meaningless in the context of the true issue, which is whether or not increased temperatures are melting more Arctic ice year to year, and even that will be subject to some degree to variations in local Arctic temperature which are in turn a result of local Arctic weather.

    This is not equivalent to saying “that the minimum value of Arctic sea ice is more related to weather than to climate,” and that statement is patently false.

    In other words, whatever the outcome this year, neither AGW-proponents nor their adversaries should claim it as a ‘victory’ for their point of view.

    First, I get so tired of positioning the AGW debate as a game, with points scored, and to be won or lost. This is particularly true because a denier will always choose to score points with short term events (such as this year’s summer ice minimum with respect to last, or 2008′s global mean temperature as compared with 1998) when these are not valid observations.

    Second, no one with any sense is going to claim “victory” based on such annual outcomes. Even a completely ice free Arctic is not a victory, but merely another piece of mounting evidence supporting the theory which is already pretty much proven beyond doubt.

    Third, it’s not a victory, it’s the most debilitating defeat the human race may suffer in its short history. Being proven right will not be a victory (or rather, it will be Pyrrhic).

    You cannot watch the globe on a day to day, month to month or year to year basis and use that as a measuring stick for whether or not the theory of GHG and climate change is correct, or proven.

    Fact: Global temperatures continue, as a long term trend, to rise.
    Fact: Arctic ice continues, as a long term trend, to retreat.
    Fact: Glaciers, Greenland and Antarctic ice masses, as a long term trend, continue to shrink.

    Playing a game of watching for which particular indicator supports your position this year or next is silly. This is sadly very true when I know that (a) all of the physics behind AGW is correct and (b) the evidence is most pronounced at the poles and so (c) sometime within the coming decades, during my own lifetime, I expect to see a summer completely devoid of Arctic ice.

    Only an unexpected and at this point increasingly unlikely negative feedback in the climate system will save us from (c), and I’m not very hopeful that one will arise.

    It doesn’t have to happen this year, or with a linear downward trend. That’s not the point. It is going to happen. Period.

    P.S. I don’t believe, from all you’ve said, that you’ve either completely read or understood Dr. Notz’s post. Please go back and read it, several times, from start to finish.

  56. Ray:

    Good article. I was surprised at the skepticism about our current ice volume measurements since Polar Science Center modeling estimates seemed to verify well. It’s hard to imagine a heavy winter rain in Western Greenland.

  57. Ron R.:

    In the context of retreating sea ice, I wonder if the term should be devolution rather than evolution.

  58. pete best:

    Re #51, I thought as much myself.

  59. Kevin Stanley:

    RE: wilt’s “If so, why then was the outcome in 2007 not ignored by the warmists?”

    Well, in addition to Gavin’s point about sticking with what has actually been said by serious people, and Bob’s (and others’) point about extent being an imperfect (potentially quite poor) proxy for the amount of ice present, there’s also this: No one had ever seen ice extent that low before. Remember that since extent is measured by looking at area with 15% or greater ice coverage, then while it is possible to have high extent with fairly little ice, it is impossible to have low extent with a large amount of ice (unless, as another poster suggested, it’s suddenly become incredibly thick where it does exist, and projects only down into the sea and not up where we might notice).

    So while summer 2007, in retrospect, probably wasn’t a huge departure from the ongoing trend in ice amount…it was the moment when rate of the ongoing ice loss became *glaringly obvious*.

    In other words the year-to-year variation in amount of ice between 2006-2007 really wasn’t all that important in the big picture. It’s just that weather conditions conspired to make it obvious from orbit, through the low extent.

    Make sense?

  60. Edward Greisch:

    41 Bob (Sphaerica): The buoys move around so much it is hard to see how anybody can make anything consistent out of it.

  61. Septic Matthew:

    It is an interesting intellectual/emotional experience to watch these processes evolve in real time while reflecting that the judgment as to overall warming and cooling depends on decades of measurements. I check “Cryosphere” and other similarly themed sites with reliable data at least a few times per week.

    Today, global ice extent is nearly average (across the past 3 decades) for this time of year:

    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg

    That’s only a single time series, but it certainly is not evidence for global “warming”. With hundreds dead from cold in the Andes this month, what we have now is one of the oscillations in which the NH is above average in temp, and the NH is below average in temp (I make no claim as to “exact balance”.)

    According to another site, the Arctic (above 80 degrees N) has below average temperatures for this time of year, and has had for a few weeks now, co-incident with a dramatic reduction in the rate of Arctic ice melt (Danish Meteorological Institute: http://ocean.dmi.dk/arctic/meant80n.uk.php) since the rapid melt of the previous 3 months.

    Inferences about long-term climate change based on events of the last 7 months are imaginary, though undoubtedly fun.

  62. Septic Matthew:

    oops, I meant that the Sh is now below average in temp. I hope that’s obvious in “context”.

  63. Hank Roberts:

    ‘wilt’ above starts from this mistaken idea:

    > an ice layer that is supposed to get thinner year after year.

    Where did you get that one, wilt? Why do you believe it?

  64. wilt:

    #55 Bob Spaerica wrote about “the current, grossly abnormal degree of Arctic summer ice melt”, and apperently he was referring to the rapid rate of melt in June.
    However, in my first contribution (#12) I discussed the July 2010 data. I wrote that in my view there is a discrepancy between the suggested sensitivity of this ‘very thin’ ice and the observation that in this July month the daily loss of sea ice is not higher but much lower than in the previous years.

    I agree with you that it would be silly to call an ice-free Arctic a victory for anyone.
    Furthermore, I have read and understood what Dirk Notz has written in his post. Basically, he argues that the sea ice in the Arctic has become very thin, and hence, in contrast to the much thicker ice of past decades, the ice now reacts very quickly and very sensitively to the weather patterns that are predominant during a certain summer.

    In view of those data, and also since the conditions at the Arctic this summer do not seem to be not completely different from those in 2008 or 2009, I remain sceptical about the concept that a large part of the remaining ice will melt soon. But we will see, by the end of summer.

  65. Doug Bostrom:

    Septic Matthew says: 26 July 2010 at 3:29 PM

    Nice misunderstanding, SM. The graph you show of course includes -all- sea ice, both that in precipitous decline in the Artic as well as that surrounding the Antarctic. The seemingly counterintuitive increase of Antarctic sea ice of course helps to lessen (hide?) the decline visible in the graph. See this post at Skeptical Science for some background information on why Antarctic sea ice is behaving as it does. Others I’m sure will volunteer more corrections.

  66. dhogaza:

    Septic Matthew:

    That’s only a single time series, but it certainly is not evidence for global “warming”.

    Ahem, it’s not evidence for uniform warming across the globe.

    However, it is evidence that science is on the right track. Scientists have, after all, been predicting that sea ice in the southern hemisphere would behave differently than sea ice in the arctic for many years. You’ve correctly pointed out that this is exactly what’s happening.

    What’s odd is that you think that when scientific predictions are supported by observations that somehow this undermines science.

    Why is that, SM?

  67. Bob (Sphaerica):

    64 (wilt),

    …and apperently he [Bob] was referring to the rapid rate of melt in June…

    No, I was referring to the long term trend, in which the summer ice retreat for all recent years is between two and four standard deviations below the long term average. As I’ve said, month watching and year watching is pointless. Trends are what matter.

    Extent Measure 1 with standard deviation
    Extent Measure 2 with standard deviation

    and this:

    Northern Hemisphere Extent Anomalies 1980-2010

    Basically, he [Dr. Notz] argues that the sea ice in the Arctic has become very thin, and hence, in contrast to the much thicker ice of past decades, the ice now reacts very quickly and very sensitively to the weather patterns that are predominant during a certain summer.

    Yes. So weather very much affects extent from month to month and year to year, but the underlying problem is the temperature change and ongoing, increased melt due to abnormally high temperatures year round, including earlier and later melt seasons, not the wind and weather.

  68. Bob (Sphaerica):

    61 (Septic Matthew),

    Today, global ice extent is nearly average (across the past 3 decades) for this time of year

    Except that this is always going to be the case, because while a nightless summer is happening on one pole, a sunless winter happens on the other. While ice cover shrinks here, it grows there, so the sum will always be about the same, even when ice completely vanishes from the Arctic in the summer.

    It’s like looking at a flat tire and pointing out that it’s only ever flat on the bottom, the other sides are always round, so it’s really not that big of a problem.

    And I rather doubt that global temperatures will ever reach the point where they are above freezing at the poles even in winter, so that the numbers you present would ever drop. It’s a frightening thought, though.

    So….

    Very nicely distracting misrepresentation of data and facts, though. You do the denial crowd proud. You should do guest posts over at WUWT.

  69. Didactylos:

    wilt said “I remain sceptical about the concept that a large part of the remaining ice will melt soon.”

    You really aren’t paying enough attention, are you? Only a small part of the remaining ice has to melt to equal recent years, and what happens is entirely dependent on weather conditions over the next couple of months.

    I just can’t work out what you are trying to prove. Do you fondly imagine that Arctic ice has begun to turn around? There is no evidence for such an idea, and overwhelming evidence to the contrary. If you want to live in a pretend world where what you believe is always true, then fine. Just don’t come here seeking justification.

    Arctic sea ice area is today missing 1.3 million square kilometres, compared to the baseline average. That is slightly worse than both preceding years, and comparable with 2007, 2008 and 2009. No doubt last year and the year before you were sceptical that so much ice could melt by the end of the season, but despite varied weather, we set the 2nd and 3rd record lows.

    In just a couple of days, the ice area will drop below the baseline minimum, with weeks to go in the melt season. So, it’s game over. There is simply no way a miracle can occur and the minimum area be above average. All that remains to be seen is exactly how much below average it is.

    (Note: this post mostly discusses area, not extent. It applies to both, but numbers and dates may differ.)

    Why does 2007 get so much attention? Blame the media for the hype. For the scientific attention: why not? It was an unusual year, some claim unprecedented. If you go back and look, you will find much speculation about “tipping points”. But from the point of view of communicating climate change, record years provide volume, but not insight. As soon as the record isn’t immediately broken, the boring old “it’s stopped” arguments come crawling out. And I really wish they wouldn’t.

  70. Rattus Norvegicus:

    John @50:

    Walt Meier has a couple of posts up about PIOMAS vs. the Navy models (he had a bit to do with developing the Navy model (PIO?). BTW, he is legit and works at NSIDC now. The posts are worth reading even if the comments aren’t :).

  71. Brian Dodge:

    wilt — 26 July 2010 @ 8:38 AM “I don’t understand how this would be compatible with the ‘very thin ice’ suggested by Dirk Notz.”
    Bob (Sphaerica) — 26 July 2010 @ 11:08 AM “Wind matters, AMO matters, but it’s not nearly as important temperature, period, and the effect of local (Arctic) weather on temperature.”
    Greg Robie — 26 July 2010 @ 9:33 AM “Comparing what is being observed this year with 2007, it almost constitutes a sea change.”
    Walt Meier — 26 July 2010 @ 11:18 AM “I’m a little bit skeptical that the volume anomaly is so low.”

    “Now consider Fig. 2 B, which shows the impact of a much thinner ice-thickness distribution: Because here most of the ice has a thickness of around 1 m, the area that becomes ice-free during summer crucially depends on the amount of total melting: In the example shown here, 90% of the area remains ice covered for a total melt of 0.5 m during a relatively cool summer, whereas only 50% of the area remains ice covered for 1 m of total thinning during a warmer summer.”
    “Because of the nonlinear ice-thickness distribution, a gradual thinning of the ice cover can initially lead to an acceleration, and, at some point, a very rapid loss of ice-covered area during summer.”[1]

    “In the simulations, ice retreat accelerates as thinning increases the open water formation efficiency for a given melt rate…” [2]

    I downloaded data from IJIS, Normalized each years data to the maximum extent for that year, and plotted them aligned to start at the day of maximum extent [3]. Note the relatively low spread in extent of previous years near the midpoint of the melt. The divergent trajectories due to weather affect the final minimum, but even years with higher final extent (e.g. 2009) are integrating the effect of higher temperatures in loss of thickness and volume distribution.

    Its pretty clear to me that this year exhibited a “sea change” in the dynamics of ice melt at the start of the year. Wind, AMO, Temperature all matter, and affect the start, rate, and end point of the melt(extent), but the thickness of the ice(volume) has a strong effect too. The decreasing minimum extents of the last few years have been accompanied by decreasing thickness and volume, and the persistent ice has integrated that change. The graphs and pictures available to us lay people have obscured the change in volume until recently[4]; Ice that was 3 meters thick may now only be 2m, and 2m may now be only 1 m, but extent doesn’t show those changes. I would argue that the dramatic rate of early melt this year is indicative of a low volume anomaly; that the “very rapid loss of ice-covered area” at the beginning of the year is a seasonal analogue of changes modelled by Holland et. al. in 2006 and expanded on by Notz in 2009.

    [1] http://www.pnas.org/content/106/49/20590.full?sid=e07507fe-9f98-41fb-9054-eafdd9d49f2b The future of ice sheets and sea ice: Between reversible retreat and unstoppable loss Dirk Notz, PNAS November 2, 2009, doi: 10.1073/pnas.0902356106
    [2] http://www.agu.org/pubs/crossref/2006/2006GL028024.shtml Holland, M. M., C. M. Bitz, and B. Tremblay (2006), Future abrupt reductions in the summer Arctic sea ice, Geophys. Res. Lett., 33, L23503, doi:10.1029/2006GL028024.
    [3] http://www.imagenerd.com/uploads/2010icemelt-cM9fB.jpg
    [4] http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php

  72. belazeebub:

    I would suggest that people (re-)read:

    ‘Perennial pack ice in the southern Beaufort Sea was not as it appeared in the summer of 2009′
    David G. Barber et al
    http://www.agu.org/pubs/crossref/2009/2009GL041434.shtml

  73. noiv:

    The usually high correlation between area and extent is going to vanish this year.

    http://arctic-roos.org/observations/satellite-data/sea-ice/observation_images/ssmi_ice.png

    In the real world the difference is open water between the floes. MODIS took a nice photo yesterday:

    http://ice-map.appspot.com/?map=Arc&sat=ter&lvl=7&lat=77&lon=180&yir=2010&day=207

    The NSIDC named it ‘diffuse ice’, isn’t ‘crushed ice’ more depicting? Also, it is strange that in September an extent of 6 million square kilometers with 50% ice concentration will not be called a record minimum.

    The Arctic is not only changing faster than the IPCC can model it, but also faster than we can adjust our ontology. Since 30 years the extent describes the arctic ice as a two dimensional object. Hopefully Cryosat will spend another dimension soon.

  74. Louis Derry:

    re #61 – This post is “imaginative”. First, actually *look* at the data. You can download the data and do some simple stats on it (or something more sophisticated f you like times series analysis), but you really don’t have to. The trend is clear to the naked eye. In both curves (ice area, ice area anomaly) there is a clear decline since, oh, the beginning of the last decade. And this doesn’t even include the thinning effect on regrown sea ice that Dirk discusses (see many other publications). The most pronounced negative area anomalies are *all* in the last few years. The deviation between the 1979-2008 mean becomes obvious in about 2002 – just look at the plot. The 3 or 5 year running means all deviate from the 30 year average in the last 7-10 years. Whaddya mean “nearly average”? There’s this thing about data – if you actually look at it, it will often tell you a lot. That’s what we scientists do for a living. The data you cite quite clearly tell the story. You must have not really looked at it. Go ahead and do some stats – same result. You get about a -1.3 million km2 average anomaly over the last few years, almost all of it due to changes in the Arctic. This is a no brainer. Go back to the uiuc site and look carefully at the other images *and* at the data used to create them. The only years on record with < 4 million km2 of Arctic ice are since 2002 (or 2006, depending on how you count uncertainties). There is an old trick – when you want to hide something, plot it on the scale you can find, and it will make the change seem trivial. The folks at uiuc weren't trying to hide anything, they just must think this is so clear they didn't need to worry about plotting with a large y-axis range. The global plot they give inadvertently makes the trend *appear* a bit less striking than their plot of the Arctic anomaly http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.arctic.png, but it actually doesn't change the numbers at all. I could go on and on – but if it's not obvious in both the global and Arctic data sets I can't help you. Cliff Notes version: the numbers on global ice area *clearly* indicate large declines in the last decade. One can argue about "why?" but there is simply no question about "what?"

  75. Jeff L.:

    I guess I shouldn’t read RealClimate comments late at night. I thought that Bob (Sphaerica) said “Question: I recently discovered the North Pole Clam.” That really piqued my curiosity! It was only a few sentences later that I discovered my error . . .

  76. Leif:

    With the Arctic showing more exposed sea and lower ice volume, it is not surprising to me to see a warmer Arctic but that would imply to me that the future coldest winter air masses will subsequently have to occur over the land masses with regularity. The average temperature of the earth must remain about average. With a large segment, Arctic, significantly warmer the cold has to go someplace. Land cools faster then water, So land it is. Recall the record cold in Mongolia this winter with ~4 million livestock frozen to death. With lots of ice the Arctic could retain the cold. Now the “Arctic” and “coldest” will not be synonymous.

  77. James McDonald:

    Granted this is an article about the Arctic, but sea ice in the Antarctic seems to have been unusually large this year. Was this expected? Is there a simple explanation?

    A back-of-the-envelope calculation of 1 million km^2 excess at 1 meter thick (?) would give an excess of about 1000 km^3 of sea ice. Meanwhile, GRACE indicates perhaps 100 km^2 of ice sheet melting. Could these be connected?

    In particular, melting ice would create an area of lower salinity around Antarctica, but how big, how deep, and how quickly would it diffuse?

    And lower salinity would lead to faster ice formation, but to what extent, and would it matter if the initial ice was formed near shore, where it would be likely to form anyway?

    These are just random musings, but it would be nice if someone with expertise could shed some light.

    Thanks…

    [Response: The difference between Arctic and Antarctic sea ice response is explained on page 30/31 of the Copenhagen Diagnosis. It makes no sense to look at the sum of both, since they are affected by very different processes and their seasons are out of sync - when you look in northern summer, the Arctic is near its minimum and the Antarctic near its maximum, so the sum is simply dominated by the latter. -stefan]

  78. James McDonald:

    P.S. Part of the reason I ask is that some denialist is sure to notice this at some point and argue that the missing Arctic ice is countered by excess Antarctic ice, so what is the problem?

    It would be nice to have a cogent answer.

  79. Rod B:

    Didactylos (48), in reply to wilt, you say, “…Icesat and submarine data show beyond doubt that the ice is a lot thinner now than previously.” Dirk Notz says in this article, “…one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past.” And goes on to hope that the launch of the Cryosat 2 satellite a couple of weeks ago will improve things. Which is it??

    How exactly do you prove that “ice extent has plummeted dramatically” by some (magical?) discounting of the gradual increase of the extent the past few most recent years?

  80. Rod B:

    Gavin (54), In his reply to wilt regarding the loss of ice extent Didactylos’ words were, “… we are in big trouble.” Because that might not quite be armageddon is being pretty nit-picky in your criticism, me thinks.

  81. James McDonald:

    For a rather simply computed measure of the state of the Arctic, has anyone compiled totals for the km’s of coastline with significant ice? This is not a measure likely to have any profound meaning, but it is easy to compute and somewhere along the way from historic ice conditions to an ice-free arctic, this number will go from a large value to zero, so it would convey some sense of where we are in that process. And there is also the possibility that unexpected patterns would jump out if it were computed…

  82. Edward Greisch:

    John P. Reisman (OSS Foundation): I used your web site to advocate fee & dividend on
    http://dotearth.blogs.nytimes.com/2010/07/26/next-steps-on-climate-and-energy-2/
    today. You should make comments on
    http://dotearth.blogs.nytimes.com
    often as well because the NYT has a large circulation. Dotearth is a good place to direct people to RealClimate.

  83. Edward Greisch:

    “The winter 2009/2010 will be remembered by many people in Europe (and not only there) as particularly cold”
    Not if they are my age [64] and have lived in the same place most of that time. Last winter was very short and rather almost hot regardless of what the short-timers thought.
    “Even in January, there were days on end with above 0°C temperature” In Greenland? Unimaginable. Over 42 adult years, the warming is very noticeable to a person in a snowy place.

  84. villabolo:

    26 July 2010 at 11:05 PM
    James McDonald says:

    “. . . missing Arctic ice is countered by excess Antarctic ice, so what is the problem?”

    James, tell them the problem is that, such Ying/Yang metaphysics will not ‘equalize’ the altered and detrimental weather conditions that an open Arctic Ocean would cause.

  85. Ray Ladbury:

    Rod B. says, “How exactly do you prove that “ice extent has plummeted dramatically” by some (magical?) discounting of the gradual increase of the extent the past few most recent years?”

    OK, Rod, you win the pony award (after the kid who is presented with a dungpile and gets excited because it means there’s a pony somewhere). How you can look at these trends
    http://tamino.wordpress.com/2010/07/26/summer-ice/

    and conclude the trend is pisitive defies explanation–unless you’ve forgotten the defiinition of climate. Of course there has been an increase since 2007–that was a very deep anomaly in the trend. Good lord! Get serious.

  86. John P. Reisman (OSS Foundation):

    This post and comments have inspired me to update my ‘Models can be Wrong’ page

    http://www.ossfoundation.us/projects/environment/global-warming/myths/models-can-be-wrong

    I added the Arctic Ice and Sea Level Rise graphs


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future – climatelobby.com
    Learn the Issue & Sign the Petition

  87. John P. Reisman (OSS Foundation):

    Rod B

    I had posted this in the Information Levels post

    http://www.realclimate.org/index.php/archives/2010/07/information-levels/comment-page-4/#comment-181881

    Figure you missed it though.

    Rod, while I was planning, and still hope to do a more critical analysis of the confidence levels in ice data, I was talking to an ice modeler just yesterday, and since I did not ask if I could quote him, I won’t, though I’m ‘confident’ he would not mind.

    I asked, let’s forget about the data for a minute and let me ask you a general lay question. How confident are you that we are losing the Arctic ice?

    His answer was simple:

    “I would say it’s a certainty that we are losing the ice.”

    I don’t know if that is the particular answer you were looking for but, from all the analysis, within the error bars, we are losing the Arctic. Even without the errors, we are losing the ice. It’s as simple as that.

    Maybe consider signing the petition now? Or is it still too soon for you.


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future – climatelobby.com
    Learn the Issue & Sign the Petition

  88. Kevin McKinney:

    “The average temperature of the earth must remain about average.”

    No, it must remain exactly average.

    At whatever numerical value.

  89. Dappled Water:

    James MacDonald (77) – yup, as shown in some model simulations as far back as the 1980′s & 90′s.

    http://www.sciencemag.org/cgi/content/abstract/278/5340/1104

    Complicated by the ozone hole, however some discussion on a proposed mechanism here:

    http://psc.apl.washington.edu/zhang/Pubs/Zhang_Antarctic_20-11-2515.pdf

  90. Chris Dudley:

    Interestingly, a lack of sea ice in the West of Greenland is being blamed for the large recent retreat of the Jakonbshavn Glacier: http://www.msnbc.msn.com/id/38233438/ns/us_news-environment/

  91. Kevin Stanley:

    @RodB
    read Walt Meier’s post at 38 and look at PIOMAS to help answer your question:

    “Didactylos (48), in reply to wilt, you say, “…Icesat and submarine data show beyond doubt that the ice is a lot thinner now than previously.” Dirk Notz says in this article, “…one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past.” And goes on to hope that the launch of the Cryosat 2 satellite a couple of weeks ago will improve things. Which is it??”

    You imply that the two views are inconsistent, but they are not. They just approach the same facts from different vantage points. There does indeed seem to be enough data to conclude with confidence that arctic ice has been thinning, AND there have not been observations as regularly as Dr. Notz (and most everyone else, I imagine) would like in order to make a precise estimate in which we may have confidence.

    And as for your next post…first, if you think it’s be “nit-picky” to consider “we’re in big trouble” as substantially different than “final proof of Armageddon,” then you and I live in different semantic universes. But presumably you would agree that nit-picking distracts from substantive conversation? So let’s stop talking about Gavin’s reaction to the word “Armageddon” and just compare the points didactylos was making in 48 with the points wilt was making in 54. I’m pretty sure one of them was right and one of them was bloviating. In case it’s not obvious, I’ll give you a hint: I think the one who was making the argument that taking all the relevant data into account, it’s clear the ice is declining rapidly (no matter what the year-to-year extent numbers) was right, and the one who responded to that very comment by accusing the first of harboring a “desire to ignore all data that do not fit with your theory” was bloviating. What do you think?

  92. Didactylos:

    Rod B asks “which is it?”

    Well, both. My statement is completely compatible with the article. Submarine data and data from Icesat put the matter beyond controversy. However, they do not provide a complete, continuous picture. Cryosat-2 will continue the Icesat record with only a small gap, but before we had satellite thickness data, we were limited to when and where a submarine happened to be.

    That’s enough to say that ice is a lot thinner now than it used to be, but with such poor coverage, it is hard to estimate exactly how much thickness has been lost, and from where.

    As for your waffle about “discounting of the gradual increase of the extent the past few most recent years” – you know you are talking nonsense. You are by no means stupid, so please don’t insult us.

  93. NeilT:

    I see the constant wuwt assertion that it doesn’t matter where the ice is so long as the global measurement is the same as ever.

    Obviously it’s garbage but people who don’t have a clue just look at the headline numbers bend a braincell or two (not consumed by the TV shows), to the problem and then consign climate science to the junk pile.

    However, if this document
    http://www.arcus.org/files/search/sea-ice-outlook/2010/06/pdf/pan-arctic/wilsonjuneoutlook.pdf
    is correct in it’s claims (and I’d guess it would not have made it into the search outlook if it was wildly inaccurate); then in the next 2-20 years (according to DR Barber in his IPY webcast), when we are ice free during the summer in the Arctic, we run a 12.5% chance of a shutdown in the North Atlantic Drift.

    The document then states that a consequence of this shutdown would be 300mph winds and deaths in the northern hemisphere (including the US).

    Now what I’d like to know of the denialists is whether they would take an 8 cylinder pistol, put a round in it and take the 12.5% chance that it won’t blow their heads off when they play Russian Roluette (deliberate misspelling to avoid being identified as spam) with it.

    Because, to me, the game being played by those who deny all the scientific evidence is Russian Roluette, not with their lives but with millions of others who have no choice whatsoever . However, the refreshing thing (OK I’m weird), about this document is that it won’t be anonymous 3rd world folk (and many western people have 3rd world disaster fatigue), who die but Americans, Canadians, Russians and Scandinavians.

    Personally, I would have thought that any Sensible, Reasoning, person; would want to avoid this scenario like the plague. Even if it had a 1 in 100 chance of coming to pass!

  94. tamino:

    For those who don’t seem to get it: global warming is about climate (the long-term trend), not weather (the short-term variations).

    Likewise, the decline of arctic sea ice extent is about the long-term trend, not the short-term variations.

    Anyone who suggest “the gradual increase of the extent the past few most recent years” as evidence against a significant long-term declining trend, just can’t be taken seriously.

  95. Didactylos:

    NeilT:

    I do not believe any filtering was done on the SEARCH estimates. Charles Wilson’s submission is just a wild guess from an interested amateur. It does not inspire me with confidence, and I have to wonder whether it was planted by the deniers solely for the purpose of being wrong. Either way, I think SEARCH made a gross error in including it without any caveats.

  96. Hunter Cutting:

    The legend below Fig. 4 reads “Arctic sea-ice extent on June 28, 2010.”

    But the legend on the top of the image says “20 July 2010.”

    Does the July 20 date refer to when the image was generated (based on data from June 28), or is something else going on?

    Hunter

    [Response: Well spotted, thanks. We updated the figure from the original KlimaLounge article, but forgot to update the caption. -stefan]

  97. Hank Roberts:

    Good catch by Hunter Cutting above re Fig. 4
    Look at the original German version–the picture is different:
    http://www.wissenslogs.de/wblogs/gallery/16/Fig4.png

  98. wayne Davidson:

    Tank sie Dirk!

    Ok there are a couple of misconceptions with respect to this years melt especially with contrarian sites.
    First off, now there is has been dominating low pressure over the Arctic Ocean, which has stopped compressing the ice over the Beaufort sea, and also decreased surface temperatures by more clouds. But this has not stopped a massive melt from going on, since its largely melting from under water, and near the pole water as shown itself
    above and cracking through, meaning the remaining ice is not thick. On satellite pictures we can literally see
    extremely broken and wet conditions, everywhere I look its weak emaciated icescape. Weather wise, what I have seen is quite extraordinary, there was/is a bunch of circumpolar Arctic High pressures surrounding and forcing a low pressure at the pole:

    http://www.esrl.noaa.gov/psd/map/images/rnl/slp_30b.rnl.html

    In Each of these high’s have likely given all time high temperature records or persistent hot and dry weather making the news.
    So I read again with amazement the quick draw mc-Graw contrarian press shooting blanks and people are buying the end of global warming for the nth time fooled by masters of drama certainly not climate or weather.

  99. Doug Bostrom:

    Didactylos says: 27 July 2010 at 10:26 AM

    Might help to note, SEARCH extended an entirely open invitation for predictions to all comers, regardless of affiliation or qualifications. A bold policy, perhaps inspired by recent demands for inclusion by “citizen auditors” and their allies. Personally I was surprised that only one conspicuous “outlier” (to put it kindly) attached itself to the collection. Possibly SEARCH expected the supporting methods documentation to speak for itself? Reasonable people would look at that and form a charitable conclusion, those with agendas would of course jump on it with both feet.

  100. crandles:

    Peter #53

    It would seem likely that there is relatively little lag.

    Ref: Impact of instantaneous sea ice removal in a coupled general circulation model (GRL, VOL. 34, L14502, 5 PP., 2007 doi:10.1029/2007GL030253

    “Sensitivity experiments show an almost complete recovery from total removal or strong increase of sea ice after four years.”

  101. Rod B:

    Ray Ladbury (85), I never asserted a positive trend. I was simply questioning the hyperbole of the statements and the cavalier back-of-the-hand throwing into the trash of the recent up ticks.

  102. Ian George:

    Are there any records of sea ice extent/volume in the early 1900s when Amundsen sailed through the NW passage?

  103. Rod B:

    John P. Reisman (87), I was merely pointing out that Dirk Notz says (and Tamino mostly agrees) that are ability to measure ice thickness is very poor — near nonexistent with any credibility, and that there is a bit of a cognitive disconnect with your-all’s “solid confidence” that ‘we know anyway that it is getting very much less.’ Like lets not let little nuisances like measuring things hinder our positions.

    I’m not quite ready to sign your petition.

  104. Philip Machanick:

    Didactylos #51: good one. I am going to start making a point of blogging IPCC errors on the side of too little warming, starting with this one.

  105. Rod B:

    Kevin Stanley (91), the statements 1) …the overall distribution of ice thickness, which we have not been able to measure routinely in the past…, and 2)…data show beyond doubt that the ice is a lot thinner now than previously… are consistent with each other??? Could’ve fooled me! I wonder how much “a lot” is, especially “beyond doubt.”

    I think it is perfectly and scientifically reasonable to assume that as sea-ice extent diminishes, thickness probably does to — to some extent. That is not what I was fussing about.

  106. Greg Robie:

    Since this comment will be at the start of a new page, and the comment starting the last page—#51—noted that current sea ice loss is consistent with IPCC modeling for 2050, I’d like to hear thoughts about the “why” of this that methane defines.

    As I have commented before at RealClimate, it appears that methane concentration tends to be peaking in the high northern latitudes in conjunction with late December and early January—the onset of the hard freeze. If the amount of insulation in the atmosphere is increasing (in the last decade it would appear that the Arctic has seen a 50 ppb increase of its average, and the seasonal variation seems to also be about 50 ppb), and countering what Gavin has asserted about the importance of methane relative to carbon dioxide, it seems to me that in the high northern latitudes, and at a time when early ice extent recovery is critical to facilitating lower temperatures as winter progresses (and retaining sea ice), this added insulation could be a key part of what the models have missed when missing when the kind of summer sea ice loss we are experiencing should have been expected to occur as the planet warms.

    I have been trying to see the signature of the increased methane in the ice data. I am now wondering if it is the rapidly growing area of ~60-80% ice ‘flowing’ through the center of the ice cap observable in this season’s melt that is the summer’s aspect of it, while the balance of the signature is visible in Figure 2 in the difference in the shape and height of the winter curves.

    Temperature increase is a root cause of the change in both extent and volume. As a former insulation contractor I know that increasing insulation—due to the logarithmic nature of U values—has exponential impacts relative to heat loss. More insulation of a type as potent as CH4 occurring in the atmosphere during the onset of ice formation is a significant variable that I am not reading discussion about in either this post or its comments. Have I missed anything?

    Part of why I Photoshopped the 1979-2000 curve as I did in my prediction this year—see #19—is that I was factoring in an educated guess re what methane is causing. As I noted before, that curve of the average is defined, primarily, by extent decline at the edges of the Arctic ice. If methane’s added insulation effects the winter dymics more than the summer ones, and the center of the ice cap more then its edges, such is a dynamic that I am betting is poorly modeled. Is this possible? It also seems to me that with the increasing loss of ice volume, the extent becomes an ever poorer stand-in for volume.

    Such would certainly would seem to be the case in what has constituted this discourse in the bulk of these comments.

    When the confusion resulting from conflating extent and volume is combined with the role motivated reasoning plays in public discourse, it seems to me that what is critical is to begin to include methane in what gets reported about the ice extent changes in the Arctic. Relative to comments about the southern hemisphere’s ice extent, there is a 100-150 ppb difference in atmospheric concentration of methane between the poles p://www.esrl.noaa.gov/gmd/ccgg/globalview/ch4/ch4_intro.html . And while Dlugokencky et al unhelpfully noted this winter that they could not see the signature of the methane time bomb’s detonation in the surface air sample analyses reported on for 2007 & 8, the metric was noted to not be a good one to see such. Concurrently, Bloom et al have used satellite data to extrapolate an increase in methane coming from the high northern latitudes. Heat loss and gain dynamics concerning the delay that the latent heat of water effects in what is observed in sea ice is key to understanding risks for which the Arctic is a metaphorical canary-in-the-coal-mine. Due to the heat involved in the change of phase of water, methane, as insulation, plays a much different role at the poles than it does elsewhere on the planet. In the Arctic, now, it is “all about (me)thane.”

    The sooner the relative importance of is methane in the Arctic is commonly understood, the less unintelligent our society might act. Science-focused blogs, like RealClimate, seem like a good place to be doing this.

  107. Didactylos:

    RodB said: “I think it is perfectly and scientifically reasonable to assume that as sea-ice extent diminishes, thickness probably does too”

    And all the data we have supports this. What we lack is a continuous dataset, in both time and space. So, we know that ice is thinning. What we don’t know is if it was unusually thick or thin in specific years, or if it was unusually thick or thin in specific areas.

    However, we can even estimate that information. We can track ice age and location, and that helps confirm estimates of thickness.

    I know deniers always think we shouldn’t act until we have all the data, and everything nailed down “to ten points of decimals”, as Lord Flibbertigibbet would say. But in this one case, can’t we just agree that the boat has sailed? We can’t go back in time and fill in the gaps in our observations of thickness. We will have to make do with the historical records we have.

    And, for the Nth time: the data we have supports the conclusion that ice has thinned significantly.

  108. tamino:

    Rod B (in #101) talks about “cavalier back-of-the-hand throwing into the trash of the recent up ticks” in summer minimum sea ice extent. Everybody should look at the graph. The “recent up ticks” are utterly meaningless in regard to the declining trend.

    I base that statement on examining and anlyzing the data. The last three years (which includes those two “up ticks”) are the three lowest on record, and are all well within the error range defined by the long-term trend. There is no evidence at all — zero, zip, nada, squat — of any “recovery” or “reversal” or doubt.

    This is not a “cavalier back-of-the-hand throwing into the trash.” It’s statistics. Rod B is the one who is being cavalier. He’s throwing into the trash the long-term trend for no other reason than he doesn’t want to believe the obvious result. He has no evidence or analysis to back up his claim — zero, zip, nada, squat.

    Rod B (in #103) also says “Dirk Notz says (and Tamino mostly agrees) that are [sic] ability to measure ice thickness is very poor — near nonexistent with any credibility.” What Notz actually says about sea ice thickness is that “we have not been able to measure routinely in the past” and in consequence “at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.” He also says “sea ice in the Arctic has become very thin,” which certainly implies that he has great confidence in the overall conclusion of an overall thinning trend. I agree with all his statements, and I’ve also posted about some of the evidence of thinning ice overall. This evidence consists of actual measurements, with credibility far exceeding Rod B’s estimation (or of Rod B himeself), and is only one piece in what’s emerging as an ever-clearer picture.

    It’s clear that we don’t have anywhere near the consistent, complete coverage of sea ice thickness (either spatially or temporally) required to reconstruct either thickness or volume with the same precision we can gauge extent or area. But the claim that our ability to measure ice thickness is “nonexistent with any credibility” is utterly false, nothing more than wishful thinking on the part of Rod B because he doesn’t want to face the truth.

    Until Rod B admits that he’s just plain mistaken on both these points, it’s time to recognize that his credibility is nonexistent.

  109. Rod B:

    Didactylos, most of what you say in #107 I don’t have a problem with. My point was that your precise words in 207 are not the same as “data show beyond doubt that the ice is a lot thinner now.” This might sound nit-picky but in scientific analyses nitpicks are important: do you fire the retro rockets for 11.5 sec or 12.5 sec? or more striking, do we fire them at X kilometers or X miles?

    The idea that “deniers always think” we shouldn’t act until we have all the data (I’ll let this hyperbole pigeon-holing pass for the sake of discussion) doesn’t give you license to blow things way out of rationality — at least in scientific discussions… in political discussions maybe a little is O.K.

    Tamino, except I read your post and noticed that you did NOT throw the recent up ticks into the trash in your analysis.

    “…nonexistent with any credibility” might be an exaggeration (“nonexistent” is a bit too pure), but ‘very little with good credibility’ is pretty much the same thing you say about the data in #108: “…don’t have anywhere near the consistent, complete coverage of sea ice thickness (either spatially or temporally) required to reconstruct either thickness or volume…”

    I have no basis or cause for disagreeing with your overall analysis; I actually thought it quite good.

  110. Didactylos:

    Okay, Rod B. I should have said “beyond a reasonable doubt”. As for “a lot” thinner – Kwok, R., and D. A. Rothrock (2009) find “an astonishing decrease of 1.75 m in thickness”. I stand by what I said. A lot thinner.

  111. Kevin Stanley:

    RodB:

    In case you’re being honest with this:

    “Kevin Stanley (91), the statements 1) …the overall distribution of ice thickness, which we have not been able to measure routinely in the past…, and 2)…data show beyond doubt that the ice is a lot thinner now than previously… are consistent with each other??? Could’ve fooled me! I wonder how much “a lot” is, especially “beyond doubt.””

    ‘Routine measurements of the overall distribution’ is simply a much higher standard than ‘enough data to confidently say there has been a large change.’

    Even if you haven’t been able to measure something routinely and comprehensively, you may still have been able to get enough measurements of enough of the area of interest to confidently judge a big change.

    And of course, this is in fact the case. For instance there’s the submarine data from the US Navy that Hank has mentioned. Is it enough to characterize as “routine” measurements of “the overall distribution of ice thickness” across the entire arctic? Nope. Is it enough to confidently conclude that arctic ice has been getting thinner? Absolutely.

    Can you see it now? The statements do not conflict with each other at all.

  112. R. Gates:

    Very nicely done summary of Arctic ice conditions over this past year. Thanks for taking the time to post it. I would like to hear a bit more about the frquency of the Arctic Dipole Anomaly, espcially as it affects the formation of sea ice, and the possible positive feedback loop that may be established where open water creates the conditions for high pressure, leading to more open water etc. I also know a great many of us are looking forward to the CryoSat 2 data with keen interest, as it will provide a valuable tool to really looking at the status of sea ice volume and mass.

  113. Septic Matthew:

    68 Bob (Sphaerica)

    These are anomalies with respect to the seasonal averages. According to some predictions, AGW is supposed to reduce total sea ice at each pole, so the seasonal total should decline.

    66, dhogaza: That’s only a single time series, but it certainly is not evidence for global “warming”.

    Ahem, it’s not evidence for uniform warming across the globe.

    I prefer my locution: a constant time series is not evidence for any change. Of course, it may also not be evidence against some particular change, but the AGW predicts reduced ice at each pole, and disappearance of ice from some parts of Antarctica has been cited as evidence of AGW even as ice accumulated in other parts.

    77, Stefan: [Response: The difference between Arctic and Antarctic sea ice response is explained on page 30/31 of the Copenhagen Diagnosis. It makes no sense to look at the sum of both, since they are affected by very different processes and their seasons are out of sync - when you look in northern summer, the Arctic is near its minimum and the Antarctic near its maximum, so the sum is simply dominated by the latter. -stefan]

    A few years ago, global sea ice total was below average, and that was cited as evidence for AGW.

    94, tamino: Anyone who suggest “the gradual increase of the extent the past few most recent years” as evidence against a significant long-term declining trend, just can’t be taken seriously.

    I agree, but your message is a few years late. A rather prominent trend that ended in 2007 was widely cited as evidence for global warming, despite the fact that it was a short-term trend. It has been followed, apparently, by a regression toward the mean.

    From April through June of 2010 Arctic ice melted at a higher rate than previously measured for that season, and got a lot of press. Since then, the Arctic ice has melted at a slower rate than previously measured for the month, and the message is it’s a short-term trend of no consequence.

    But all of the short-term trends are of little evidentiary value, including the warm summer of 2010 on the American East Coast, and the cool summer of 2010 on the American West Coast. The long-term “trends” of temperature and precipitation on both coasts are nearly flat.

  114. Didactylos:

    “A few years ago, global sea ice total was below average, and that was cited as evidence for AGW.”

    By whom? Antarctic sea ice has been increasing very slightly for a very long time. There’s nothing new, here.

    New records always do get more press than mere boring decade on decade ice loss. We will all just have to live with it – scientists need all the positive press coverage they can get.

  115. tamino:

    There is perhaps no single topic on which we hear more blathering idiocy than the subject of ice in general, and sea ice specifically — as this thread has already demonstrated.

    I believe that the reason is this: the cryosphere is so obviously screaming “global warming” so loud, that denialists feel they have to say something, anything, no matter how false or how stupid, in a vain attempt to silence it.

  116. Brian Dodge:

    “….some denialist is sure to notice this at some point and argue that the missing Arctic ice is countered by excess Antarctic ice…”

    The first thing to point out is that less Arctic ice will mean more evaporation from open water and higher humidity in the North polar cell circulation, regardless of how much ice is in the Antarctic. The southerly surface flow of the polar cell will carry more moisture into the Polar/Ferrel cell uplift region, increasing precipitation. This may be observed in increased rainfall(or snowfall when the temperatures are low enough); it will be predominately in fall when decreasing temperatures are squeezing out the excess moisture built up by the larger summer ice extent decline. [2][3][4]

    The second thing to point out is that any yahoo like me with internet access and a rudimentary spreadsheet can show that NH declines aren’t balanced by SH increases. [5] Note that yearly averaging hides the decline of the much larger summer versus winter season; a larger effect on the weather won’t be hidden.

    [1] http://en.wikipedia.org/wiki/Atmospheric_circulation
    [2] http://www.google.com/#hl=en&q=wales+nov+2009+fall+floods (Great Britain is in the zone where the polar & Ferrel cells converge)
    [3] http://www.dasmirnov.net/blog/a-snow-covered-britain
    [4] http://www.imagenerd.com/uploads/sno_cover_anomaly-gZZqa.jpg data from Rutgers Snow Lab http://climate.rutgers.edu/snowcover/ – I shoulda put credit on the image)
    [5] http://www.imagenerd.com/uploads/seaiceanomaly-g7Hw4.jpg Monthly data downloaded from http://www.woodfortrees.org/data/nsidc-seaice-n/plot/nsidc-seaice-s , with a 12 month running average and a 1979-1989 base period average subtracted

  117. Hank Roberts:

    And the third thing to point out:

    Friday, March 12, 2010
    WUWT trumpets result supporting climate modelling

    NSIDC Reports That Antarctica is Cooling and Sea Ice is Increasing trumpets the observation that Antarctic sea ice is increasing. This is expected from climate modeling. Nice to see someone else is picking up on this interesting confirmation of our scientific expectation….

    http://moregrumbinescience.blogspot.com/2010/03/wuwt-trumpets-result-supporting-climate.html

  118. RichardC:

    28 Wilt said, ” It seems to me that in this situation things like AMO are more important than CO2.”

    In essentially all situations things like the AMO matter more than CO2, but CO2 changes the universe of potential situations. In other words, short-term weather stuff masks long term climate stuff over the short term.

  119. Bob (Sphaerica):

    113 (Septic Matthew),

    These are anomalies with respect to the seasonal averages. According to some predictions, AGW is supposed to reduce total sea ice at each pole, so the seasonal total should decline.

    Excuse me if I don’t fall into this typical denier trap.

    “According to some predictions, AGW is supposed to…”

    So you make a vague claim that a claim is sort of made, etc. etc.

    Please cite a specific prediction, attributable to some work of science (not a blog or some vociferous denier’s recollection), with the source.

    At the same time, please read the second paragraph from Hank’s link (#117):

    The prediction is old. In 1992 Manabe and coworkers, in running a changing CO2 experiment, noticed that the Antarctic sea ice cover increased with increasing CO2. They traced this to increased fresh water on the Antarctic ocean, which derived from increased precipitation — snow. They also observed in their model that the Arctic ocean sea ice experienced a marked decline in thickness, and major loss of extent in the summer, but not so large a decrease in the winter.

  120. Rod B:

    Didactylos (110, how about, “we strongly suspect?” ‘Beyond a reasonable doubt’ is the highest level of proof in legal circles and not met here.

    Quite a feat: with very few measuring capabilities your references none-the-less have measured the decreasing thickness within one centimeter — presumably as an average over the entire Arctic? Impressive! You’re still confusing extensive scientific measurements with strong personal beliefs based on a few observations.

    Kevin Stanley (111), ‘enough data to confidently say there has been a large change’ is getting more like it, though I could still quibble a little bit with the elusive “large.” However, the initial phrases are still inconsistent: their words are not the same as these words. A scientist who says, “I’ve been looking at it a long time and from many perspectives, and, though I have little direct tangible evidence, I am confident from the evidence I do have that the ice is thinning to the extent that a major global problem is ensuing” is speaking like a scientist. I might disagree with his/her conclusions but I can’t refute his analysis. On the other hand one who espouses hyperbolic rabid rhetoric and claims evidence that clearly does not exist is not acting scientifically and I can state with confidence ‘beyond a reasonable doubt’ that he’s just blowing smoke up my butt.

  121. Didactylos:

    Rod B: Enough already. You have provided zero evidence that Arctic ice has not thinned. The Scottish legal system has an appropriate term: no contest.

  122. tamino:

    Comments from Rod B and Septic Matthew are what I was talking about in #115.

    It’s a real pity so to pollute such an informative post from Dirk Notz. I only hope such displays don’t discourage him from further contributions to RC.

  123. Doug Bostrom:

    tamino says: 28 July 2010 at 9:03 PM

    Comments from Rod B and Septic Matthew are what I was talking about in #115.

    If hairs are all they’ve got, hairs are what they’ll split. Failing having anything useful to say, semantic quibbling can fill any empty volume, even that which used to be properly filled with an icecap.

  124. John P. Reisman (OSS Foundation):

    #49 Edward Greisch

    That is a truly great link! Thanks for that.

    Chris, I may be mixing up things I heard about Callendar and Arrhenius? Some of what is in my head came form talking to different scientists and I don’t recall (oops, an Alberto Gonzales moment ;).

    Here are a some of gems from Svantes paper in 1896:

    “Certain American geologists hold the opinion that since the close of the ice age only some 7000 to 10,000 years have elapsed, but this most probably is greatly underestimated.”

    “A simple calculation shows that the temperature in the Arctic regions would rise about 8º to 9º C., if the carbonic acid increased to 2.5 or 3 times its present value. In order to get the temperature of the ice age between the 40th and 50th parallels, the carbonic acid in the air should sink to 0.62–0.55 of its present value (lowering of temperature 4)–5) C.)”

    “On the supposition that the mean quantity of carbonic acid in the air reaches 0.03 vol. per cent,”

    “The following calculation is also very instructive for the appreciation of the relation between the quantity of carbonic acid in the air and the quantities that are transformed. The world’s present production of coal reaches in round numbers 500 millions of tons per annum, or 1 ton per km.squared on the earths surface. Transformed into carbonic acid, this quantity would correspond to about a thousandth part of the carbonic acid in the atmosphere”

    I’m still browsing, but really interesting to see these papers.


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance:Learn the IssueSign the Petition

  125. Dhananjay Jog:

    Environmental degradation is happening faster than previous anticipations- Considering the rate of disappearing of Arctic-ice,it is obvious that within a decade we will have ice-free Arctic.

  126. Kevin Stanley:

    RodB:perhaps it’s true that “one who espouses hyperbolic rabid rhetoric and claims evidence that clearly does not exist is not acting scientifically and I can state with confidence ‘beyond a reasonable doubt’ that he’s just blowing smoke up my butt.”

    Please have a look if you haven’t already at Kwok and Rothrock 2009, consider PIOMAS, read some of the IPY reports on arctic sea ice, and then tell us to whom you are referring when you say “one who…claims evidence that clearly does not exist.”

    You have been directed to evidence, yet you seem to be claiming it “clearly does not exist.” Think about that for a second.

    When you’re done with that, maybe consider the irony of accusing someone else of being hyperbolic and calling them rabid in the same sentence.

  127. John P. Reisman (OSS Foundation):

    Okay, I found the ref for Arrhenius by digging through my notes

    ‘Svante Arrhenius suggested human emissions would warm the planet.’

    This came form a conversation with Spencer Weart. it was in my notes and it is also in the script for the Climate Science History video, which is why I was talking to Spencer.

    http://www.youtube.com/watch?v=czRDS3jTM4o

    I noticed it was also in our emails. So I’m not going crazy, maybe?

    #70 Rattus Norvegicus

    Thanks, I talked to Walt just a few days ago.

    #103 Rod B

    The confidence issues are between the error bars. i.e. the uncertainties are in between the error bars. but the error bars both top and bottom are heading down.

    I’m unsure as to why you don’t see there is at least some confidence in this? But I will try to find the contexts re confidence that may help.


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance:Learn the IssueSign the Petition

  128. Kevin McKinney:

    #127–John, as you can now see from Edward’s link, you were quite correct that Arrhenius considered the human contribution. At the time, though, the effective timescale appeared to be centuries, and Arrhenius didn’t anticipate what we now call the “downside.” He had a tendency to use the adjective “genial” to describe warmer climates.

    Even Callendar, I think, uses the phrase “deadly ice” in connection with global cooling.

    The realization that warming, too, could be “deadly” probably didn’t begin to dawn until Plass, who I think says that warming could become a “problem” in the future. (Though I don’t think he knew yet at that point–’56?–how soon that future could arrive! He was alive–though experiencing declining health, I think–when Kyoto was signed, and lived till March 1, 2004.)

  129. Rod B:

    Didactylos (121), so if I can not prove it is not thinning, it must be thinning??!! If I can’t prove that a horse can not climb the oak tree, it is proven therefore that it can? This has gone from silly to ridiculous.

    tamino (122), I think Notz’ post was very well done. My comments supporting some of the things he said is hardly “polluting” his post. The other posters who I’m arguing with and who discount what Notz said have to be the polluters. Go fuss at them.

    Doug Bostrom (123), if pointing out exaggerated statements is hair splitting, that means science does not need to be precise and bloviating hyperbole is perfectly acceptable so long as, presumably, the scientist’s heart is in the right place. Nice!

  130. Didactylos:

    Rod B: I didn’t ask for proof. I merely asked for any evidence at all. Evidence that it is getting thicker, evidence that there is no trend in thickness, evidence that the thinning is very slight – you have offered none of these.

    If you provide some evidence, then we can weigh it against the strong evidence of severe long-term thinning, and make our own judgements.

    Otherwise: no contest.

  131. Rod B:

    Kevin Stanley (126), you are correct that I am not aware of all even many of the ice thickness studies. I am relying on just one source, Notz, in this thread when he says, “However, for [total sea-ice volume] estimation one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past. While this will hopefully change in the future because of the successful launch of the Cryosat 2 satellite a couple of weeks ago, at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.” So if you have sources that say Notz is flat-ass wrong and some have long been able to measure thickness over the whole Arctic to within one centimeter, it sounds not credible, but I certainty can’t refute it.

    Please don’t raise the strawman that I’m saying Notz therefore does not believe diminishing sea ice volume is a problem. He doesn’t, and I have not said so.

  132. Rod B:

    John P. Reisman (127), good point. I am not disagreeing that many are confident that sea-ice volume in the Arctic is significantly shrinking, and, more to the point, some of those are studied scientists who are drawing a not unreasonable conclusion — maybe an irrefutable conclusion — with high confidence. I’m merely taking to task those that spout our super capability to make very accurate measurements of the sea-ice volume when that capability doesn’t exist.

    BTW, in the battle for hearts and minds, those ballyhooed exaggerations just serve up fat slow pitches for skeptics and (gulp) deniers to blast out of here — DOES NOT help your cause.

  133. Doug Bostrom:

    Remote sensing of my cranium via mirror reveals a trend to more skin. In-situ digital inspection reveals that the volume of my hair is not increasing farther toward my personal upper pole. Invisible hair indeed appears to be a hint that loss is taking place. I conclude that my hair is “thinning,” a more comforting term than “I’m going bald.”

  134. Bob (Sphaerica):

    127 (John P. Reismann),

    Okay, I found the ref for Arrhenius by digging through my notes

    ‘Svante Arrhenius suggested human emissions would warm the planet.’

    This came form [sic] a conversation with Spencer Weart.

    So are you saying that Spencer Weart lies about his age, and is in fact at least 91 years old, having had that conversation with Arrhenius in 1929 at the prodigal age of 10? Or are you implying that Weart (or maybe Arrhenius, or both) has a time machine?

    [Sorry... the deniers get to quote mine all the time. I just wanted to try my hand at it.]

  135. Didactylos:

    Rod B: How do you hope to have a sensible conversation about anything when you only look at one statement? You can examine it and tear it apart all day long – but until you look at the studies that Notz and I base our conclusions on, you will never understand why our claims are consistent.

    It disturbs me greatly that you haven’t bothered to find out about the data our claims are based on. Notz, of course, references his own work. I have already pointed you to Kwok, R., and D. A. Rothrock (2009), and they in turn reference Rothrock’s earlier work, Rothrock et al. (1999, 2008).

    Now, go and read at least the conclusions of these papers, and think for a moment about the difference in data quality between submarine cruises and satellite data. Next consider for a moment that currently we have neither real-time satellite data, nor real-time submarine data. Now do you understand what Notz meant when he said “at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.”?

    It will take you a while to read and digest all this, so I will ignore you for at least 24 hours. Maybe tomorrow will lead to a more productive conversation.

  136. Ray Ladbury:

    Rod B says, ” I’m merely taking to task those that spout our super capability to make very accurate measurements of the sea-ice volume when that capability doesn’t exist.”

    There is, of course, always the question of how accurate measurements must be to draw a conclusion about a general trend. If we see ice thinning everywhere we look, it begs credulity to think that it must be thickening everywhere else–particularly when we KNOW temperatures are rising. Sometimes, logic works, Rod.

  137. Septic Matthew:

    119, and tamino before that:

    Comment by Bob (Sphaerica) — 28 July 2010 @ 5:56 PM

    OK, I’ll accept that AGW makes no claim that Antarctic ice will decline. I didn’t bookmark what I read (or else it was a few years ago), and it may have been an unreliable source. If I come across something good (i.e. peer-reviewed) in the future, I’ll post a reference. Until I read something different, I’ll accept what you wrote.

    Slightly off topic, but does AGW predict increase tropical cyclone activity? NOAA predicted an increase in activity for this year, but so far that has not happened.

  138. Septic Matthew:

    There’s this, but it might not be directly relevant:

    http://earthobservatory.nasa.gov/Newsroom/view.php?id=42399

    Unless the ice flowing off from Antarctica (without melting) is what is causing the apparent increase in SH ice extent.

  139. Bob (Sphaerica):

    137 (Septic Matthew),

    All from the IPCC:

    11.2.4.5. Tropical Cyclone and Storm Surges
    9.5.3.6 Tropical Cyclones
    10.3.6.3 Tropical Cyclones (Hurricanes)
    10.4.1.2 Climate variability and extreme events
    1.3.8.2 North-east Atlantic extra-tropical cyclones

    Extract from the third, based purely on simulations (and note that it is for a 3x CO2 increase, or somewhere around 855ppm, while we’re now only at 390ppm):

    For 3 × atmospheric CO2 in that model configuration, the simulated tropical cyclones experienced a 56% increase in the number of storms with maximum wind speed greater than 30 m s–1 and a 26% increase in the number of storms with central pressures less than 970 hPa, with no large changes in frequency and movement of tropical cyclones for that southwest Pacific region.

    There are many, many others. Use this link to search for “cyclones” in the IPCC report:

    IPCC Google Search

    I’m pretty sure that a prediction by the NOAA on an individual year would have to do with specific conditions this year, however, without any vague climate change factor, and like all weather predictions…

    I would expect, however, that any such increase related to climate change would have to go with a correspondingly strong increase in temperatures, and while it’s getting warmer (0.8C since 1979, give or take), I’d be surprised myself (again, not being a scientist, not looking at actual numbers, just eyeballing things) if the warmth we’ve seen so far could also be matched to any statistically measurable increase in either storm strength or quantity.

    There’s just too much variability in the system, I think, to get anything useful out of that until (a) temperatures rise a lot more and (b) one has a much longer time frame in which to gather data.

    But since the warming we’re committed to now (how ever long it takes to get there) is probably about 1.4C, and we’re unlikely to take reasonable action as a civilization until we’re committed to at least that magical 2C mark, then I expect we will know at least part of the answer to that question in time (whether we like it or not).

  140. Nigel Williams:

    So is there something intrinsically wrong with the estimates of Arctic sea ice volume done every few weeks by the Polar Science Centre?

    http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php

    Right now that shows ice volume is somewhere below FOUR standard deviations below the ‘historic’ mean trend for this time of year. This is further from the trend than ever observed, and does not bode well for ice survival should wind and weather even briefly conspire towards minimising ice extent in October.

    And Cryosphere’s present image shows more fragmented and lower ice concentrations for this time of year that I can recall from many years of watching.

    http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png

    Its not hard, is it? The evidence of the crime is there, and we know who did it!

    N

  141. Joel Shore:

    Re #137: Just to amplify what Bob said, tropical cyclone forecasts for individual years have much to do with the detailed conditions for that year, not primarily AGW, since there is a lot of year-to-year variability. In particular, note that Bill Gray has also predicted a very active Atlantic hurricane season ( http://hurricane.atmos.colostate.edu/forecasts/ ) and he is an AGW “skeptic”.

  142. Titus:

    The article states: ” Arctic ice…again and again in early summer the question arises whether the most recent trend in sea-ice extent might lead to a new record minimum”.

    I imagine that other folks (myself included) are also looking at Antarctic ice reaching maximum’s, as it appears to have done recently. Do you think that this is worthy of a similar note? I’d be interested for one.

    [Response: We ought to do that. I'll look into it. A couple notes for starters though: First, Antarctic sea ice isn't as predictable, because it is thinner, and more subject to winds. Second, huge areas of Antarctica have actually seen persistent declines in sea ice. The average trend has been positive, but barely so. In West Antarctica (where it is warming) the trend has been strongly negative.--eric]

  143. Karsten V. Johansen:

    To Rupert Matthews concerning ice thickness. Please listen to:

    http://video.hint.no/mmt201v10/osc/?vid=55

  144. John McCone:

    Pertaining to the quote:

    \A much more useful measure for the state of Arctic sea ice is therefore the total sea-ice volume. However, for its estimation one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past. While this will hopefully change in the future because of the successful launch of the Cryosat 2 satellite a couple of weeks ago, at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.\

    This website make exactly the opposite statement saying that the navy does measure ice thickness and that the total ice thickness has increased over the past 2 years:

    http://wattsupwiththat.com/2010/05/29/arctic-ice-volume-has-increased-25-since-may-2008/

    How can these two statements be reconciled with each other?

    [Response: Because 2 years is not the long term trend? - gavin]

  145. Didactylos:

    Those crazy deniers! Models are wrong, they say. But when observations look inconvenient, suddenly the model is right and the observations wrong?

    I’m sure PIPS2 is a useful product, but I give it as much credence as any weather forecast.

    John McCone: Watts and friends have misled you to believe the navy measures ice thickness. They don’t. They put the concentration data into a computer model and try to forecast thickness. This is very, very similar to what PIOMAS does.

    It took me a moment to work out exactly how Watts produced this rabbit out of a hat (never mind the meaninglessness of comparing two single days). But I got there after a pause for thought: firstly, he is looking at winter/spring ice, so we don’t see the unambiguous signal seen in late summer. Then, in early 2008 the ice was in poor shape having undergone extreme basal melting in 2007, due to the ocean heating caused by the open water associated with the dipole anomaly. 2007 also saw a huge loss of multi-year ice. In 2010, the proportions of first and second year ice were more normal – but that did nothing to stop it melting.

    Watts should start a cherry farm with all those cherries he picks.

  146. M:

    “This website make exactly the opposite statement saying that the navy does measure ice thickness and that the total ice thickness has increased over the past 2 years:”

    1) As Gavin noted, short term trend
    2) The PIPS method that Goddard uses is a combination of Navy data and Goddard’s own home-cooked system: the volume dataset used by most Arctic scientists seems to be the PIOMAS dataset, though even that system uses a number of extrapolations and therefore (as far as I can tell) is not as sound a dataset as sea ice extent.

    -M

  147. Alan Millar:

    We are told that the increased Antarctic sea ice extent we have seen was forecast and is entirely in line wth the Models and predictions. When exactly did this become the truth? It wouldn’t be another example of past posting would it?

    I tend to find my predictions are pretty accurate when made after the event!

    This is what the IPCC said about Antarctic sea ice in 2001.

    “16.2.4.2. Sea Ice in the Southern Ocean
    Antarctic sea ice is not confined by land margins but is open to the Southern Ocean. Sea-ice extent contracts and expands on an annual cycle in a roughly concentric zone around Antarctica. The ultimate extent is controlled by a balance of air temperature, leads, wind direction, upper ocean structure, and pycnocline depth. Some of these parameters are controlled in the atmosphere by the relative position of the subpolar trough with respect to the sea ice. In the ocean, variations in the Antarctic Circumpolar Current are important. The extent and thickness of Antarctic sea ice are sensitive to the depth and thermal properties of overlying snow, about which relatively little is known.

    A reduction in Antarctic sea ice volume of about 25-45% is predicted for a doubling of CO2, with sea ice retreating fairly evenly around the continent (Gordon and O’Farrell, 1997). This CSIRO model assumes a 1% yr-1 compounding increase of CO2, corresponding to global warming of 2.1°C. Using a similar but modified model that has a higher albedo feedback and predicted global warming of 2.8°C, Wu et al. (1999) calculate a reduction in mean sea-ice extent of nearly two degrees of latitude, corresponding to 45% of sea-ice volume. These estimates do not represent the equilibrium state, and sea ice can be expected to shrink further, even if GHGs are stabilized.”

    Here is what was said by the IPCC in 2007…………

    ” Highlights from the IPCC Working Group I Summary for Policymakers of “Climate Change 2007: The Physical Science Basis”

    “What can we expect to happen?”…………..“Sea ice is projected to shrink in both the Arctic and Antarctic.”

    So what is the correct story?

    Alan

  148. dhogaza:

    So what is the correct story?

    It starts with noting that CO2 hasn’t doubled yet … “A reduction in Antarctic sea ice volume of about 25-45% is predicted for a doubling of CO2″.

  149. Patrick 027:

    Two different things about the Southern hemisphere -

    Wind driven upwelling of water in a ring around Antarctica (in the midlatitudes or subpolar – I forget offhand which best characterizes it) can be enhanced by atmospheric responses to keeping the upwelling region SSTs similar while warming SSTs at lower latitudes; thus the upwelling can sustain itself and keep a latitude band in the Southern hemisphere from warming as much as other places. (Predicted)

    The Southern hemisphere has less land area and thus the heat capacity of the ocean may slow hemispheric warming even more than in the Northern Hemisphere.

    Antarctica’s ice sheet will tend to have a slower response time than sea ice and thus can prevent or delay polar amplification of the sort seen in the Arctic.

    Salinity plays a role in sea ice formation. See http://www.skepticalscience.com/antarctica-gaining-ice.htm

  150. Didactylos:

    Alan Millar: I’m not aware of any specific prediction that Antarctic sea ice would continue its gradual increase in the short term.

    As dhogaza says, in the long term, we do expect a significant decline.

    So, what actually was expected?

    We definitely expected to see the Arctic warm much faster than the Antarctic. Eventually, both poles will even out again, but that won’t be for a long time. Have a look at the climate model anomaly maps – they show this very clearly, and have done so from the beginning.

    We are also unsurprised that increased precipitation should cause ice build-up in inland areas of Antarctica. This doesn’t compensate for the mass lost by melting, but in the recent past it has certainly caused regional mass gain. Many people confuse land and sea ice. Maybe that’s how the confusion started?

    As far as I am aware, the dynamics of Antarctic sea ice are still an open question. There are some strong theories, but it’s not yet certain which mechanisms play how much of a role in the current increase. However, none of these theories will prevent the inevitable long term decline.

  151. jyyh:

    (theorized of). #147, one explanation I remember for the increase of Antarctic sea ice is as follows: The global warming increases the moisture in air. This moisture will fall down anywhere it’s cold enough. The coldest place on earth is Antarctica interior. The snow from added moisture will turn into ice over time in Antarctica. This slightly increases the gravitational gradient of ice streams around the Antarctic coasts. This will speed them up. The added ice to ocean from the ice streams is unsalted. As the ice from ice streams of Antarctica melts, this heightens the freezing point of salty ocean water. Thus, GW increases the amount of sea ice on places and at times where there is an increase in the glacial calving and subsequent melting.

    Can’t remember where I 1st saw this explanation, possibly it was on early 1990s, when this issue wasn’t so topical yet for me.

  152. jyyh:

    Could have been this one I read in 1995 or 1996: http://journals.ametsoc.org/doi/abs/10.1175/1520-0442(1992)0052.0.CO;2
    and remembered wrong… Doesn’t change the logicx in the prev answer though :-/.
    Then there’s Cavalieri’s
    http://www.sciencemag.org/cgi/content/abstract/278/5340/1104
    but should register to read it (again). Maybe I will.

    This was a surprise find on this article chase.
    http://tintin.colorado.edu/CVEN5718/Readings/Mercer_Nature_1978.pdf
    previously I thought the potential collapse of WAIS was a matter considered first in late 1980s.

  153. Brian Dodge:

    “(CNN) — An 11-year-old girl was killed and her mother injured when a chunk of ice struck them near a cave attraction in Washington state.

    The two were on a family outing Saturday near the Big Four ice caves in Mount Baker-Snoqualmie National Forest, authorities said.

    The pair was not in or on the caves, said Lt. Jeff Brand of the Snohomish County Sheriff’s Office.

    The 11-year-old girl died after an ice patch fell on her head, he said. Her mother was injured in the leg, but she was not hospitalized.

    Brand said ice at the popular attraction is melting so much this year that it is not stable, and warned visitors to stay away from the ice caves.”

    I know that a singular event can’t be attributed to global warming, but we will eventually get enough small statistics like this to add another confirmation of adverse effects of AGW. Phrases such as “Climate change”, “recent trend in sea-ice extent”,or “trends in extreme weather events” are safely abstract and faceless.
    [edit]

  154. jyyh:

    More likely it was this one:
    http://www.nature.com/nature/journal/v352/n6330/pdf/352019a0.pdf
    should go to the university library for this one. (captcha: flying vexation) Note to beginning scientists, always keep a notebook handy to write the proper references down.

  155. Timothy Chase:

    Didactylos wrote in 150:

    We are also unsurprised that increased precipitation should cause ice build-up in inland areas of Antarctica. This doesn’t compensate for the mass lost by melting, but in the recent past it has certainly caused regional mass gain. Many people confuse land and sea ice. Maybe that’s how the confusion started?

    As far as I am aware, the dynamics of Antarctic sea ice are still an open question. There are some strong theories, but it’s not yet certain which mechanisms play how much of a role in the current increase. However, none of these theories will prevent the inevitable long term decline.

    Back on 8 April 2009 I included links to a few resources that might on where the increase in sea ice is occuring, the warm outer West Wind Drift, the cold inner East Wind Drift, etc. here: Comment 267 of Wilkins Ice Shelf Collapse. But briefly, my thoughts, for what they are worth is that increased melt in Antarctica, particularly along the West Antarctic Penninsula during the Antarctic summer is resulting in more fresh water, stratification, similar to what we are seeing in the Arctic with lighter fresh water on top. As fresh water freezes more easily, this leads to more ice, particularly as it hits the cold inner East Wind Drift.

    Big thing to remember, though, is that we aren’t particularly worried about sea ice melting per se. This isn’t what is going to raise sea levels. We are worried about the reduction in Arctic Sea Ice because of what changes this may imply for ocean circulation in the Atlantic, for example, a collapse of the Atlantic Conveyor Belt could cause temperatures in North America and Europe and oxygen levels in the Atlantic to drop rather severely. But at this point we aren’t seeing anything like this. More importantly, the loss of Arctic Sea Ice makes the loss of much of the ice in Greenland a virtual certainty, at least in the long run.

    Antarctica? What worries us the loss of glaciers along the West Antarctic Penninsula and ultimately the (inland) ice sheet that is anchored below sea level. And sea ice around the West Antarctic Penninsula — being outside the Antarctic Circumpolar Current — is on a downward trend.

    The whole Southern Hemisphere? Sea ice is showing a positive trend of +1.2%. The Bellingshuasen Sea to the west of the West Antarctic Penninsula? -5.3%. The Ross Sea, essentially a bay of water that is closest to the South Pole and well within the Antarctic Circumpolar Current? +4.8%.
    *
    I see that Patrick 027 has put his finger on the fact that ocean has greater thermal inertia than land as the reason why the Southern Hemisphere is currently lagging behind the Northern Hemisphere in terms of global warming.

    Please see comment 149:

    The Southern hemisphere has less land area and thus the heat capacity of the ocean may slow hemispheric warming even more than in the Northern Hemisphere.

    Ocean water mixes. In fact you will find that you can detect 20th Century warming as far down as a mile. Land? Does mix much. So basically all you have to do is warm the surface and heat will only gradually flow to the lower layers. So where you have more land things can warm at the surface more rapidly.

    Anyway, the Article that he points you to suggests that a number of mechanisms are in play, including ozone depletion chilling Central Antarctica and resulting in stronger winds resulting in more polynyas formation and thus sea ice formation — as well as the presence of more fresh water.

    Please see comment 149

    Salinity plays a role in sea ice formation. See http://www.skepticalscience.com/antarctica-gaining-ice.htm

  156. Timothy Chase:

    PS to my above comment

    I had pointed to an earlier comment of mine from 2008, and while I think that post has value, particularly in terms of what it links to, at one point I speak of the storm track continuing to move poleward. This may however be slowed or even reversed for a time if the ozone hole heals significantly. If it heals this should weaken the Antarctic Polar Vortex and the storm track will shift towards the equator or at least move poleward more slowly. (In a warming world storm tracks are expected to move poleward.)

    If the storm track shift towards the equator then the moist warmer maritime air will shift towards the equator as well. This will slow the strong warming trend that we have seen along the West Antarctic Peninsula. So far, both as a consequence of global warming and ozone depletion, the warming of the West Antarctic Peninsula has resulted in glacier loss moving at a more or less steady pace inland over the years towards the West Antarctic Ice Sheet.

    The ozone hole has been both the cause and to some extent the effect of a stronger polar vortex. Moisture carried aloft into the stratosphere by a stronger polar vortex results in further ozone destruction. This increases the temperature differential between the upper troposphere and lower stratosphere and thus strengthens the polar vortex.

  157. Timothy Chase:

    Found the following that may be of interest… The strengthening of the Antarctic Polar Vortex by global warming and ozone depletion has served to move the storm tracks southward and contributed to drought in Australia:

    … The vortex delivers the winter rain-bearing westerly winds called the ‘Roaring Forties,’ which southern Australia relies on for its water supplies.

    However, Jones and team have found that global warming and ozone depletion are interacting to shrink and accelerate the vortex, dragging crucial rainfall towards the South Pole, away from Australia’s landmass.

    The ‘reliable’ rainfall regions most affected by the loss of winter rains are coloured dark blue and purple (Bureau of Meteorology)
    The researchers relied on three decades of data from Antarctica, U.S. and Australian research to show the operation of a vicious cycle. On the one hand, ozone depletion leads to cooler temperatures and lower pressures above Antarctica. On the other, greenhouse warming leads to higher temperatures and pressures over other parts of the globe. This steepens the temperature-pressure gradient between Antarctica and the rest of the Southern Hemisphere, resulting in the stronger and faster-spinning polar vortex which ‘pulls’ the rain-bearing westerlies southwards.

    Antarctic polar vortex sends Australian drought spiralling
    16 Feb 2009
    http://www.abc.net.au/science/news/enviro/EnviroRepublish_946924.htm
    http://climatechangepsychology.blogspot.com/2009/02/antarctic-polar-vortex-sends-australian.html

    Would be interested in the study itself, but haven’t been able to find the title as of yet.

  158. Hank Roberts:

    jyyh, on Antarctic sea ice:

    http://www.realclimate.org/?comments_popup=4469#comment-182806
    pointing to this:

    http://moregrumbinescience.blogspot.com/2010/03/wuwt-trumpets-result-supporting-climate.html

    Much more info in the comments and links there

  159. michael sweet:

    Re Gavins response to 144:
    Dr Meier (from NSIDC) was quoted in a blog post last month on WUWT saying that PIPS is not a suitable source for data to compare thickness of ice from year to year. The quote did not say why. Presumably they are interested in other things (speculation: they plot maximum thickness of an area not average thickness because that is what ships care about). The PIPS data is not intended to be integrated for volume and is not suitable for that use. The PIPS concentration data is also substantially different from AMSR-e.

  160. jyyh:

    Thank you Hank Roberts, might have been the Manabe & al (1992) paper, I read about 15 years ago as well. As Grumbine says, this prediction is old.

  161. dominik lenné:

    To do another back-of-envelope-calculation, based on http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php:

    mean volume loss per decade: 3400 km3
    mean minimum volume for considered period: 14000 km3
    volume anomaly against mean volume 2010: -10000 km3
    remaining volume 2010: 4000 km3
    expected time to zero volume in summer: 1,2 decades, that is 2022.

    Any mistakes made (except assuming linearity)?

  162. D. Price:

    I see Bremen has gone off line again. This is the only same that gives same day ice extent. Time the got it sorted out. does anybody know why they have these problems?

  163. Ian K:

    How come I can only read this article in german? I have only the title in English and clicking on it only takes me to the comments? I have raised this issue twice before with no effect

  164. flxible:

    hey Ian K!! watch what you wish for, now there’s 2 articles with the German version the front page!
    But you can read the English version by clicking the Brit flag beside it.

    reCartcha: outsold nearby

  165. jyyh:

    Just a note, due solar storms that occurred on 1-2 Aug there may be some delay on the updates on several sites covering the satellite measurements.

  166. Ian K:

    thanks flxible. it was a dumb mistake!

  167. adrian smits:

    I still don’t understand why there is such a large divergence between giss and dmi

  168. Ralph:

    “”Walt:
    What catches my eye is the temp anomaly. Plus ten on a sustained basis?”"

    Plus ten temperature anomaly? I cannot see any ‘plus ten’ here.
    http://ocean.dmi.dk/arctic/meant80n.uk.php

    How secure is your data?

    .

  169. dominik lenné:

    I made a plot of the http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php data with the intent to put it into wikipedia. (I “reverse engineered” the values of ice volume.) Can anybody please give me a hint how “hard” these data are. As I understand, they stem from a complex numerical model stiffened by real weather, temperature, current and sparse ice thickness data and crosschecked against ICESat measurements. Do they have kind of 15% precision, what do you think?

  170. wili:

    Picking up on greg robies’ discussion in 106–one of the reasons Arctic melt is of concern to me is that it would seem to greatly increase the likelihood that seabed methane, especially in the shallow continental shelf north of Siberia, would dissociate at increasing rates, perhaps freeing up what I understand are very large quantities of free methane below. Do we have any latest data on methane release in areas like ESAS this summer?

    Also, has there been further important research on what an ice-free Arctic Ocean will mean for North Hemisphere weather patterns and for ocean currents…

    As to the condition of Arctic ice, the term I have seen from people actually interacting with it is “rotten ice,” for example here environmentalresearchweb.org/cws/article/yournews/41112 and google the phrase to find many more such examples.

  171. Sigurdur:

    I notice in the comments section that there is a lot of misconception as to the current Arctic temperature trend.
    It has been quit cold in the Arctic for 3 months. Where do people get the information that it has been warmer?
    Thank you.

  172. Sekerob:

    Sigurdur, quite cold is still less cold than it used to be. Above minus 11 C sea ice melts from below… the very melt holding the summer rise in check… until it’s all gone. There are many charts around to show the anomaly… here’s one: http://polar.ncep.noaa.gov/sst/ophi/color_anomaly_NPS_ophi0.png

  173. David Sims:

    Post #19

    “I feel I can make this educated guess at what the thermal dynamics of our changing climate
    will do to the ice extent this year.”

    take a look at the current graph – slightly different to your prediction!!

  174. Kevin McKinney:

    #171–

    “The Arctic” covers a lot of ground (and ice.) If you are talking about DMI data by some chance, it’s valid for 80 degrees to the Pole, and yes, it’s shown a colder than average summer.

    On the other hand, if you are talking about the Canadian Archipelago, it has been quite a bit warmer than usual for most (though not all) of the summer. Northern Russia–well, that’s been in the news, hasn’t it?

    NCDC July blended land/sea data:

    http://www.ncdc.noaa.gov/sotc/get-file.php?report=global&file=map-blended-mntp&year=2010&month=7&ext=gif

    NCDC June blended land/sea data:

    http://www.ncdc.noaa.gov/sotc/get-file.php?report=global&file=map-blended-mntp&year=2010&month=6&ext=gif

  175. JimCA:

    There doesn’t seem to be an open thread, but this is sort of on-topic:

    Looking at the arctic map at cryospheretoday.com, it seems that the arctic ice cap no longer connects to either North America or Eurasia.
    As far as I can tell, this has never happened before. Am I wrong?

    If this week is the first time that has happened in recorded history, shouldn’t that be noteworthy?

    Thanks for any clarification…