Sea ice animation upthread reminds me of how ice behaves on the Great Lakes, except of course it's the Arctic Ocean. What a remarkable thing to witness.

Anybody here happen to know the aviation maintenance/safety enhancement know as "HUMS?" Among other things HUMS captures recordings of nominal dynamic behavior of aviation machinery so when things begin to go weird they'll be noticed before parts start to fly off. Imagine if the Arctic basin plot Neven posted was a helicopter rotor harmonic plot and the mechanic responsible for the machine was routinely reviewing HUMS data for signs of trouble. Business as usual? Doubtful. Ideally we'd be using our instrumentation systems as an alarm source. Of course, that's axiomatically "alarmist" so no can do.

Further to 2°, truth appears to be breaking out all over: Science adviser warns climate target 'out the window' One of the [UK] government's most senior scientific advisers has said that efforts to stop a sharp rise in global temperatures were now 'unrealistic'. Prof Sir Bob Watson said that any hope of restricting the average temperature rise to 2C was 'out the window'. He said that the rise could be as high as 5C - with dire consequences. Sir Bob added the Chancellor, George Osborne, should back efforts to cut the UK's CO2 emissions. He said: 'I have to look back on [the outcome of successive climate change summits] Copenhagen, Cancun and Durban and say that I can't be overly optimistic.' 'To be quite candid the idea of a 2C target is largely out of the window.' 'I would say to George Osborne: `Work with the public sector. Work with the public on behaviour change. Let's demonstrate to the rest of the world that we can make significant progress here`' Sir Bob is among the most respected scientists in the world on climate change policy. More at BBC: http://www.bbc.co.uk/news/science-environment-19348194 That's the Tory government's adviser speaking. Chancellor Osborne is out-of-phase, as are many politicians; Osborne is not going to look like a hero 20 years from now.

Kevin McKinney: To understate things a bit, it seems pretty likely that this season is going to mark a big milestone on the longer term trajectory of the ice--though I won't be surprised if next year is even worse. It's interesting to look back at the available satellite record and see the gradual unveiling of more perfect hindsight: we've been steadily setting new records for low extent since the beginning of these* observations, while for some reason 2007 was the first to really seize our attention. Indeed, it seems the available satellite record doesn't even include a baseline "normal." "Ice, we never even knew you." A very simple bet would hinge on whether next year will set another record for low extent, or if we'll have to wait a bit longer for what's now clearly inevitable. Monthly records occasionally have back-back "lowest yet" but annual? Are there any, yet? * See http://nsidc.org/data/seaice_index/images/n_plot_hires.png for instance. What's "normal" in that record?

Me: ...much more ice than water to the sky. I intended the opposite.

Werther: ...I’ve included the image of ice as a sort of ‘bank account’ in my thinking. Like any km3 melted releasing the involved forcing energy to ‘do other things’. I think I see what you mean. I can't express my opinion on this in a scientific way either other than the crudest sort of napkin calculations but I'm considering the surface properties of ice as they're capable of influencing the overlying atmosphere (air/ice, radiative, etc.), which would seem to vary in influence as a function of relatively contiguous surface area of ice. An influence that is independent of volume, 2D if you will as the ice "appears" quite normal until the last few centimeters melt away or it has broken up so as to present much more ice than water to the sky. Thinking about the energy budget and particularly the open ended time horizon I suspect as far as weather goes that the effects of enthalpy of the ice itself will be transient, ephemeral. But speaking of thin crusts, I myself am a mile wide and an inch deep. Don't pay much heed... :-)

"Several denialist blogs are now beginning to insist that an ice free Arctic is no problem, as it happened in the past." I don't think those folks are thinking it through quite all the way. As long as there's a fair swathe of ice extent lingering through summer in the Arctic, things down south are going to remain more or less smoothly functioning in the accustomed manner. That is to say, sea ice extent matters to weather more than volume; as long as there's even a crust of ice covering enough of the Arctic ocean the atmosphere's not going to know or care what's happening to volume. As the crust diminishes into insignificance, -then- we'll see what portends for our future. For my part I think we'll see a several-year "step function" in weather behavior farther south that'll be very obvious in retrospect, looking at the years spanning the decline from "functional" to "useless" ice covering the Arctic ocean.

anthropocene: In this scenario how do you plan and build new ports, oil terminals, sea defences etc.? There must be some way to build all these with robustness to SLR change built in - I suspect this makes them much, much more expensive. You need ample foresight and the freedom and resources to use it. See SkS piece on London for an example of what a robust civil service armed with facts is supposed to do and is able to accomplish when the political climate allows this to happen.

Can't help but wonder about destruction under the ice, seeing that river. Excellent imagery of this area on Google map/Earth; search Kangerlussuaq.

Rob Dekker: Either way, these projections make the IPCC look like "deniers", but then again, the IPCC projects a minimum of some 6.5 million km^2 this year...while self-proclaimed 'skeptic' blog WUWT just put in their best estimate of 4.55 million km^2. An excellent point-- "alarmist" shoe on the other foot. If WUWT's prediction is below that of IPCC for year after year, what are we to conclude?

Bernard Vatant asked an intriguing question about turbid runoff perhaps being an indicator of melting intensity. I notice that Jason Box entertains comments at his site; Bernard's question might be right up Box's alley. Albedo appears to be running right off the rails this year; see MeltFactor latest post: Greenland ice sheet albedo continues dropping at highest elevations Box speculates about role of wildfires elsewhere in this year's precipitous plunge.

Further to Al Rodger, Jason Box and MeltFactor have an update on Greenland albedo. The news is darker (sorry!). Greenland ice sheet reflectivity at record low, particularly at high elevations

A lot of work in this article. Thank you, Neven.

Just a quick caution that Apocolypse4Real's "Moscow Times" link above seems to be infected. Opening the article produces: ClamAV: Exploit.JS.CVE-2006-1359 "Exp/TxtRng-A is an exploit for a vulnerability in Microsoft Internet Explorer (CVE-2006-1359)." So if you're running an ancient copy of IE, best avoided.

That death spiral graph by Jim Pettit is a very useful visualization, solves some problems with other perspectives. It's also a nice pun.