You are old father William

The concentration maps are more alarming (e.g.), although I suppose we'll have to wait and see if a corresponding loss of extent is seen later in the season.

I happened to spot Maslowski's presentation from the March State of the Arctic conference, and he's sticking with 2016 +/- 3 years notwithstanding having acquired the level-headed Ron Kwok and Jay Zwally as collaborators.

A video of its press conference is available and was very interesting (5 or 6 of the leading scientists summarizing the state of things), but it was covered by exactly one (1) reporter. While I suppose "Arctic still melting, now even more ahead of schedule" has acquired a certain dog bites man quality, sharply contrasting with anything possessing the merest whiff of potential scandal, I still found the lack of press attention a little unbelievable. At the end of the video someone can be heard observing that the reporter just got an exclusive, followed by bitter laughter from all.

BTW, it's when I got the progressive bi-focals that I acquired the habit of peering over my specs, that being more comfy much of the time than tilting my head back.

Sea ice area is also interesting.

http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Area.png

Re:The Euthyphro Dilemma

Does God have free will ?

Re : Spencer's choice of belief. There is a pattern to it. As when temperature rise became obvious some claimed that average temperature doesn't exist, as AGW becomes more obvious some will claim it can never be proven.

Varifocals don't seem to work for me. I'm using my telephone to write this post, as usual, and I find it most comfortable simply to take my glasses off and hold the screen about ten centimetres from my face. When I'm out and about I simply peer over the top.

The varifocals give me the option of holding the telephone at waist level and peering down while holding my head fixed, but I haven't ever got used to it. It's okay for text entry but I find it very hard to read web pages using that method. My unassisted vision at the 10 to 15 cm range is excellent and that means the small high resolution screen of a modern phone is ideal for me.

My only worry is that sometimes people assume that I'm holding the camera phone up to take photographs, which can cause embarrassment. It's a really tiny telephone and really doesn't look like the kind of device a person could use for nearly all of his internet communications.

Does God have free will? Of course she does.

Cryosphere today is looking interesting at the moment too.. A linear extrapolation would have complete melting by mid july. Although I would have to point out that melting is not usually linear.

Arctic ice melt in any one year is affected by external factors (winds, currents, clogging of flow channels, etc) so what you get in September is always heavily influenced by weather conditions during the melt season.

There is strong evidence, though, that the state of the ice has been irreversibly compromised. There's less old ice around and the ice state has been described by field workers in ways that are difficult to reconcile with reports from just a century ago. Ice thickness measurements from laser altimeters suggest a medium term reduction.

[I'm dubious about this. The recovery time for the Arctic pack isn't very long -W]

Albedo and extent of ice in the meantime do matter for global warming, but possibly not that much. By that I mean that it's quite possible, at least in principle, to reach a kind of tipping point where the arctic region became seasonally ice free without causing a global tipping point (irreversible climate change locked in by the arctic changes). But gross arctic climate change would have unignorable regional effects. We live in interesting times.

"possible, at least in principle, to reach a kind of tipping point where the arctic region became seasonally ice free without causing a global tipping point"

Notwithstanding tipping points are as far away from the consensus as 0 degree C sensitivity, studies by NASA and a mostly ignored paper by James Hansen indicate recently identified multi period ocean oscillations and black soot pollution are principle causes of the diminishing ice.

"... tipping points are as far away from the consensus as ..."

Kind of an over-broad generalization, perhaps? I don't think most scientists dispute the concept of a "tipping point" (Younger Dryas would seem to illustrate this nicely).

The Younger Dryas is not an example of a tipping point. A tipping point occurs when a trend becomes unstoppable. The Younger Dryas not only stopped a warming trend, it reversed the trend. This Discovery News article mentions possible causes.

[Tipping point lacks a clear meaning. See, e.g., http://scienceblogs.com/stoat/2008/02/tipping_point_watch.php -W]

Paul, people may use words differently. Most people I work with would understand "tipping point" to be a point at which a system switches from more-or-less stable state "A" to a different more-or-less stable state "B".

The Younger Dryas isn't itself a tipping point, but presumably some tipping point was crossed that set off the relatively rapid transition from the state "warming North Atlantic region" to the state "rapidly cooling North Atlantic region".

There is a good discussion of the concept of tipping points at RealClimate. I think it nicely confirms my comment that there's nothing particularly controversial about the concept of "tipping point" itself.

5 degrees would convince Spencer? Some might be convinced much sooner than that...

http://i48.tinypic.com/2jdgo5x.jpg

Then again, Spencer isn't convinced by primary evidence either (the human fingerprint). Secondary evidence (the rapid rise of modern temperatures) isn't likely to change his mind.

J,

Glad you agree YD wasn't a tipping point. Per RC: Tipping points are fundamentally tied to the existence of positive feedbacks. Even if the Younger Dryas was a feedback, it would have been a negative one.

Nor did it occur because some tipping point was crossed that set off the relatively rapid transition from the state "warming North Atlantic region" to the state "rapidly cooling North Atlantic region". It likely was the result of a cataclysmic event (huge melt lake draining or meteors) according to the Discovery article linked above.

Can you point to anything in the IPCC AR4 or peer reviewed literature that indicates tipping points are part of the consensus?

MarkB's graphic is excellent.

I forgot the captions.

http://i47.tinypic.com/256zcpc.jpg

[The recovery time for the Arctic pack isn't very long -W]

Wm, being superficial again

[I can be less superficial if you like: http://www.agu.org/pubs/crossref/2007.../2007GL030253.shtml -W]

As for Doctor Who, as the little child who sat and watched the first ever episode with my dad in November, 1963, my vote is for Moffat.

When I fell in love with Doctor Who, what I signed up for was the mad wizard who storms into Stone Henge with a red haired girl who waited for her imaginary friend and a ruthless woman he meets backwards. I was seven years old. I've grown up a bit since then but I still remember. Trust me, this is how Doctor Who is supposed to work. It hasn't always been this good but it was worth the wait. For television this good I would have been happy to wait another couple of decades.

William, you're dubious about ice decay, you think recovery cycles are short, and you think "tipping points" are poorly defined.

I can buy all of those but still think something is up in the arctic. I'm watching closely to see what happens.

[Don't misinterpret me (I'm in the process of writing the what-I-think-about-cl-ch-in-easy-words post). For tipping points, you might like http://www.realclimate.org/index.php/archives/2006/07/runaway-tipping-p… . For Arctic sea ice, I really don't know -W]

Paul, I'm not really interested in participating in an argument just for the sake of arguing. If that's what you're looking for, you'd best find someone more like-minded.

There are many references to the existence of tipping points in the literature of various fields, including both ecology and climate science. William links to a previous post of his, which in turn references:

Lenton et al. 2008. Tipping elements in the Earth's climate system. Proceedings of the National Academy of Sciences, 105: 1786-1793.

This was followed, a year later, by a special issue of PNAS [December 8, 2009; 106 (49)] devoted to papers about tipping dynamics in various segments of the earth system, including two "perspective" papers and seven or eight research articles.

You can also find no shortage of papers referring to the existence of tipping points in ecosystems. A few minutes with Google Scholar should make that clear. I think the first paper that came up when I tried that was by Steve Carpenter, former president of the ESA and pretty much a walking embodiment of the scientific "consensus" among ecologists.

Again, I'm not interested in a lengthy "how many angels can dance on the head of a pin" style argument. I'm also not interested in debating whether X, Y, or Z is or is not a tipping point, since as William points out the language gets imprecise here. But you seem to be categorically denying the actual concept of tipping points, to the extent that you analogized it to "climate sensitivity of 0 C". I think that's an unreasonable comparison.

Steve, thanks for the pointer -- only mention I've seen anywhere -- to
> Maslowski's presentation

J,

I don't in any way deny the concept of tipping points in general or their possible existence in climate. I do say that they are as far from the likely and most likely probabilities of the consensus, in other words as likely to happen, as a 0.5 degree C net feedback for doubling CO2. My guess is that both are in the 10% range.

I like to argue for the sake of self education, but I hope this is more in the spirit of a discussion. Even though the Younger Dryas turned out to not be a tipping point, I'm glad you brought it up because I didn't know what it was until today.

Is Lenton et al consensus science? Did you read what William wrote about it?

That's 0.5 degree C negative net feedback

:] I can be less superficial if you like: http://www.agu.org/pubs/crossref/2007.../2007GL030253.shtml -W]

Not much, the all other things changing in the direction Wm chooses ploy is not berry berry convincing. The climate is a heavy ocean liner.

> is Lenton et al consensus science?

There's no consensus list defining what is and isn't consensus science, but Scholar lists these citing Lenton et al.; weighing them may help:

Cited by 264

[I'm not sure that Lenton et al. is really science -W]

> Lenton et al.

Did their promised followup article appear somewhere?
I didn't go past glancing through their supplemental text, which at least defines 'tipping point' for their purposes. It's here
http://www.pnas.org/content/suppl/2008/02/07/0705414105.DC1/05414Append…

which says in part:
"... Six events are related to the tipping elements discussed in the present paper, and we focus the discussion on these. An overview of the elicitation and the results from the other parts of the questionnaire will be presented in a separate article (Kriegler E, Hall JW, Held H, Dawson R, Schellnhuber HJ, unpublished work)."

With the recent kerfuffle over a survey of climate scientists, this older survey of scientists might be interesting if it's been published.

Hank: More here: http://hot-topic.co.nz/tipping-and-other-points/

[Thanks for that. But notice how slippery these things are: you say:

Tipping elements (or points, as Malcolm Gladwell would have them) are changes that once started take on a life of their own, and canât easily be returned to their original state. In the climate system that might be the rapid loss of an ice sheet in a few decades or hundreds of years, while regrowing it might take many thousands.

But you've subtley confused things there. For one thing, the Grrenland ice sheet (say) will not melt in decades or centuries: it will take thousands of years. For another, what you're describing with the ice sheet is just hysteresis, not a tipping point -W]

Sheets, safe; shelves, maybe not?

"Some say that we wonât see these ice shelves disappear in our lifetime â Iâm not so sure. I think we might well.

e360: Are you kidding?

Bindschadler: No, no at all."

No, he's not talking about Greenland there. Reassuring.
http://hot-topic.co.nz/five-feet-high-and-rising/

the Grrenland ice sheet (say) will not melt in decades or centuries: it will take thousands of years. For another, what you're describing with the ice sheet is just hysteresis, not a tipping point

I won't pretend to be able to bring great clarity to this issue (only to point to the recent work of others), but I understand that the Greenland ice sheet is thought to have a "tipping point" where it becomes committed to substantial (but not necessarily complete) loss. Where that point is, is a good question. In any event, it's likely to be more stable than the WAIS, as Hank has spotted.

[First of all, I'm not at all convinced that your use of "tipping point" here has any more substance thatn saying "hysteresis".

Let me see if I can write this down in a comprehensible form. The idea of the "tipping point", as I understand it, is something like a pencil balanced on its point on a blob of blu-tack: it is stable, if you push it a bit nothing happens, but if you push it a bit more it catasrtophically cjhanges (and you won't get it back without a great deal of effort). This very simple idea never applies to things in the real world. In the real world, the ice sheets are subject to daily, yearly and decadal fluctuations. If there were sensitive to small perturbations they would have fallen over already. So effectively all sharp edges (in phase space, not the real world) get smeared out.

So yes: if you melt enough of Greenland to lower the ice sheet sufficiently that it is no longer cold on the top, it can't be recovered without a major cooling of the whole earth. But this isn't a very exciting observation: to have melted that much would take ~500+ years (I don't know; more than a century).

The other "threshold passing" thing about Greenland that people speak about is pushing CO2 levels up high enough top melt it all eventually. We're probably at or near that now. But that isn't a tipping point at all -W]

The paper's supplementary info page gives their definition of tipping point, "... formalised as follows (neglecting stochasticity in the control Ï, in which case all equations would have to be rewritten in terms of probability statements)."

Have any of the citing papers rejected the very idea that tipping points can exist? If not, opportunity awaits.

Happy New Year all - this being my first comment of 2011.

Harry Potter is actually up to 63, should be a new one any day now.

My Mother used to read us that poem when I was very young, early 1950's.

I tried varifocals. My Alexander Method training makes it most un-natural to have to move my head so my eyes look through the right part of the lens. But I also cannot remove my glasses because of both eyeball geometry differences and astigmatism. My solution (only relatively recently discovered) has been tri-focals.

Climate: 60+ years of weather experience tells me the extremes are getting more extreme. Anecdotal I know but I do understand the idea that pumping more energy into a chaotic system increases the amplitude of its excursions both ways. Beyond that I rely on info from those who have spent their lives studying the climate in detail and I can not claim an original thought there for this discussion.