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Bruce Worden
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I, too, fall in the exponential rather than Gompertz camp. My reasoning is simple: The ice has been thinning. As the (surface area) / (volume) ratio increases, the ice will melt faster. This is borne out by the acceleration in volume loss over the past couple of decades as seen in your first figure (vis a vis the area/extent losses). I see no reason for the volume loss to decelerate without a significant change in climate/weather. P.S. It would be helpful if you were to make the x-axes of your plots cover the same time period and extend the area and extent projections to cover the time out to 2025. If volume drops to (near) zero while there is still significant area/extent, that will suggest that the projections are not consistent and need some revision.
Mary, You'll probably get a few opinions here, but my take on the data is that 2007 was exceptional because of exceptional weather (superimposed, of course, on a long-term declining trend). The "recovery" that followed in 2008 and 2009 was simply a "dead cat bounce" back toward the trendline, perhaps enhanced by somewhat cooler weather in those years. The arctic really, really wants to freeze and stay frozen, but that tendency is being overwhelmed by the changing climate. This year was not driven by particularly exceptional weather, it was the result of the long term erosion of the ice volume (a steady decrease in the multiyear ice that you mention) brought about by a dramatically warming arctic. So its hard to say what will happen next year. If it's a warm year, the record could be broken. If it's cool, or the wind blows the ice around at the end of the season, we could see a somewhat greater extent. No matter what the extent does, one thing is almost certain: there will be less ice volume next year than there was this year.
Toggle Commented Oct 6, 2012 on More vids at Arctic Sea Ice
Djprice537: The winter maximum is in a declining trend, just not as dramatic (yet) as the summer minimum. See this image from Cryosphere Today: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2010.png That plot goes through 2010. I wish they'd update it. You can also look at the sea ice (area) anomaly to see the long term decline: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/sea.ice.anomaly.timeseries.jpg
Toggle Commented Oct 6, 2012 on More vids at Arctic Sea Ice
So we have microbes turning the ice black, and now mining: http://www.nytimes.com/2012/09/24/science/earth/melting-greenland-weighs-perils-against-potential.html?hp I can't imagine how much soot large-scale mining is going to spew onto the ice. Not to mention the industrial heat and the glee with which the mining companies will shred the ice while chasing new deposits. And farming activity has been increasing for years now, which means more animals, which means more local atmospheric methane. (And any local CO2 reduction from the increased plant life is going to be offset by the CO2 spewed by mining, farm machinery, and increased population.) I'm starting to think that the ice sheet might melt a little faster than we expect.
"We get good coverage of the Arctic ice melt in Australia - here is the latest from ABC News website - a graphic showing loss of ice since 1984." I like the graphic, but I get frustrated with all of this talk of the "average." I know that one needs to establish a baseline, but when that baseline is a declining trend, the average value misrepresents what is happening. And then you compare this year to the average and you leave the impression that "wow, yep, that's different from the average," when the real story is a long-term and increasingly rapid decline.
A4R: "I have posted the CH4 359 hPa imagery for Sept 11-20, 2012 vs 2011." Ouch.
Karl, you post insulting, inflammatory rhetoric and then whine and demand apologies when you get back in kind. Is your "doctorate" perhaps coming from the Anthony Watts School of Pretended Outrage? I doubt anyone here is impressed with your alleged credentials. What is impressive is that despite the massive balance of evidence to the contrary you assert that global warming is the result of "natural cycles." Whether that is actual ignorance or ideological stubbornness the answer is the same (as Chris put it): "shut up, stop whining, go away and learn."
Rob Dekker, Thanks for the heads-up and the link. This is something I've been following for a time now, and I'm glad to see others taking note. If you look at Flanner et al. (2011), they were seeing about 0.45 (up to 1.1) W/m2 forcing from snow and ice albedo change -- as of 2008. That was before the big snow melt records (and recent ice records) were set. I'd estimate that we're now looking at at least 0.6 W/m2, probably more. Pretty terrifying when you consider that ALL of that heat is being dumped into the Arctic over the course of the summer. That's a lot of heat to warm the ocean, permafrost, and air. I'm beginning to think that the methane "alarmists" may have a point. Not to mention how is Greenland going to react when everything around it looks like the Mediterranean? Ugh.
crandles: "One way you can get more ice at maximum in the seasonally ice free version is that it misses out on autumn/fall snow cover which is excellent insulation compared to just ice." Okay, that's one I can accept. It's the kind of thing I was referring to earlier when I said "It would require the initial conditions to set up some persistent air or water circulation pattern that caused less energy inflow or more energy outflow in system A than in system B." Snow cover differences could have a similar effect if they persist and allow for differential energy outflow even when ice cover was equal. As for alternating years, there would be an at-least-partially-offsetting positive feedback when the thinner snow melted sooner, exposing (lower albedo) ice to the sun's input. I have no idea what the relative scale of these factors is, so it's hard to guess how might play out. My guess is that all of this is second-order and we're going to continue to see rapidly decreasing ice until we don't have any. Chris: No argument that the open water dumps more energy to the atmosphere than the ice covered water. Especially since the water is relatively warm from basking in the sun all summer. But that just means you have relatively warm Arctic autumns (and, I suppose, eventually winters too). Aside from wreaking havoc with NH weather, the warm blanket of air would actually tend to retard ice formation. Kevin: Your house of cards analogy is also a good description of the state of our civilization vis a vis the climate. Just make the people adding the cards blind, deaf, and greedy, and it's about perfect.
Kevin, I understand that the ice provides insulation that slows the loss of heat. What I can't see is a mechanism for ending the season with more ice in the open-water case than in the ice-covered case. Even if they start at the same temperature, the open-water system has substantially more heat in it (because ice at a given temperature has less heat than water at the same temperature). As the open water loses heat, ice forms, creating a layer of insulation, and the rate of heat loss decreases. The rate of heat loss, and total heat, asymptotically approaches that of the ice-covered system. So I don't see how in a finite period of time you ever end up with as much ice as the ice covered system, let alone more.
"Conrad, yes. There is a negative feedback by way of less insulation allows more rapid ice formation." I keep hearing people talking about this negative feedback, but it doesn't make sense to me. Yes, at some point you'll likely get a very rapid freeze up of the open water, but I can't see how you get more total ice at the end of the cold season. Consider: System A is warmish open water, system B is ice-covered coolish water. System A has substantially more total energy than system B. So if you remove the same amount of energy from both through the winter, there is no way that system A ends up with more ice than system B. System A may initially release more energy, but if system A overtakes system B in total ice, then at some point they would be equal, so how is it that system A then releases more energy than system B to end up with more total ice? It would require the initial conditions to set up some persistent air or water circulation pattern that caused less energy inflow or more energy outflow in system A than in system B.* But we're not seeing that. We've had large areas of open ocean at the end of the melt season for the past few years and we continue to see lower and lower ice volume, and a continuation of the long-term trend toward lower maximum ice area. *Looked at another way, you would expect the two systems to approach one another asymptotically -- i.e., they would reach the zero energy state at the same time. But how does the system that starts with more energy (A) cross under the one that starts with less (B) and then the second system (B) begins to shed more energy in order to "catch up" with the first (A) again? I can imagine a weird crisscrossing asymptote like this might be possible to construct in a dynamic system (orbiting bodies w/ momentum transfer; non-Newtonian viscosity; something), but thermodynamics is pretty unidirectional and temperature-proportional in its energy transfer.
Thanks, Seke -- again, those are great plots.
Seke Rob, Those are great plots. They really make the point, and they make the deniers look stupid. I'd like to see those graphs up on all the science sites. The presentation is good, too. What software do you use to make them?
"Denialistas happily argue that it's because the CO2 gas is cold, but is it enough to fully remove the flame's IR radiation?" Isn't the air between the flame and the detector cold (relative to the flame), too? Isn't the upper troposphere cold relative to the planet's surface? The temperature of the intervening gas shouldn't matter if the gas is transparent to IR -- the IR should pass right through to the detector. Use Helium instead of C02 and see what happens. Denialists are morons.
I'm gonna guess that the green is some kind of refractive temperature/salinity contrast effect. Or aliens. Never rule out aliens.
For people who find such things fascinating, yesterday's LANCE image is spectacular: http://rapidfire.sci.gsfc.nasa.gov/imagery/subsets/?mosaic=Arctic.2012262.terra.4km You can really see the state of the ice (or what's left of it), and Greenland is nearly cloud-free.
Dominik, Have a look at the Oct, Nov, Dec, Jan, Feb, snow anomalies at: http://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=1&ui_region=nhland&ui_month=10 The trend is definitely toward more winter snow in recent years. And then it all very quickly melts...
Neven: I may be wrong, but I believe the plots you are using show the average sea ice for September, not the minimum. If so, it would be more consistent to perhaps show a likely range for the current year, rather than the minimum. Aaron: I think you are correct about so many things in your comment that I wouldn't even know where to start. The insolation changes are particularly worrisome. This talk: http://www.wcrp-climate.org/conference2011/orals/B11/Flanner_B11.pdf based on this paper: http://www.nature.com/ngeo/journal/v4/n3/full/ngeo1062.html is quite informative. Particularly devastating is slide #30 ("1979-2008 evolution of cryosphere forcing"). Ending as it does in 2008, it doesn't include the record low late-spring/summer NH snow cover, or the renewed ice retreat of the past few years. I suspect we are looking at at least 0.6 W/m^2 now. And, as insolation, it's *all* concentrated in the north, warming the permafrost and the arctic ocean. Worrisome, to say the least, in terms of potential CO2 and methane release.
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Sep 17, 2012