We covered this extensively at WUWT last summer, including the “unprecedented claim” where a researcher said it was a recurring 150 year event that was ‘right on time‘. It turns out jet stream changes and thin cloud cover was the driver. Also “the analysis shows that ocean temperatures and Arctic sea-ice cover were relatively unimportant factors in causing the extra Greenland melt.”.
From the University of Sheffield
Jet stream changes cause climatically exceptional Greenland Ice Sheet melt
Research from the University of Sheffield has shown that unusual changes in atmospheric jet stream circulation caused the exceptional surface melt of the Greenland Ice Sheet (GrIS) in summer 2012.
An international team led by Professor Edward Hanna from the University of Sheffield’s Department of Geography used a computer model simulation (called SnowModel) and satellite data to confirm a record surface melting of the GrIS for at least the last 50 years – when on 11 July 2012, more than 90 percent of the ice-sheet surface melted. This far exceeded the previous surface melt extent record of 52 percent in 2010.
The team also analysed weather station data from on top of and around the GrIS, largely collected by the Danish Meteorological Institute but also by US programmes, which showed that several new high Greenland temperature records were set in summer 2012.
The research, published today in the International Journal of Climatology, clearly demonstrates that the record surface melting of the GrIS was mainly caused by highly unusual atmospheric circulation and jet stream changes, which were also responsible for last summer’s unusually wet weather in England.
The analysis shows that ocean temperatures and Arctic sea-ice cover were relatively unimportant factors in causing the extra Greenland melt.
Professor Hanna said: “The GrIS is a highly sensitive indicator of regional and global climate change, and has been undergoing rapid warming and mass loss during the last 5-20 years. Much attention has been given to the NASA announcement of record surface melting of the GrIS in mid-July 2012. This event was unprecedented in the satellite record of observations dating back to the 1970s and probably unlikely to have occurred previously for well over a century.
“Our research found that a ‘heat dome’ of warm southerly winds over the ice sheet led to widespread surface melting. These jet stream changes over Greenland do not seem to be well captured in the latest Intergovernmental Panel on Climate Change (IPCC) computer model predictions of climate change, and this may indicate a deficiency in these models. According to our current understanding, the unusual atmospheric circulation and consequent warm conditions of summer 2012 do not appear to be climatically representative of future ‘average’ summers predicted later this century.
“Taken together, our present results strongly suggest that the main forcing of the extreme GrIS surface melt in July 2012 was atmospheric, linked with changes in the summer North Atlantic Oscillation (NAO), Greenland Blocking Index (GBI, a high pressure system centred over Greenland) and polar jet stream which favoured southerly warm air advection along the western coast.
“The next five-10 years will reveal whether or not 2012 was a rare event resulting from the natural variability of the NAO or part of an emerging pattern of new extreme high melt years. Because such atmospheric, and resulting GrIS surface climate, changes are not well projected by the current generation of global climate models, it is currently very hard to predict future changes in Greenland climate. Yet it is crucial to understand such changes much better if we are to have any hope of reliably predicting future changes in GrIS mass balance, which is likely to be a dominant contributor to global sea-level change over the next 100-1000 years.”
###
In a story at RedOrbit the scientists report:
Scientists have been trying to determine what led to the 50-year-record ice melt in Greenland. In April a team of scientists wrote in the journal Nature that they determined that the ice melt could be due to thin cloud cover.
h/t to junkscience.com
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In the meantime the temperature in the Arctic is the coldest it has been for today in 21 years.
http://ocean.dmi.dk/arctic/meant80n.uk.php . . the last time was in 1992 . .
http://ocean.dmi.dk/arctic/meant80n.uk.php
Very little of that meltwater made it to the sea as the episode was very short lived and not penetrating in a meaningful manner. Most of the melt quite likely re-froze within seconds to minutes from the cold of the underlying ice mass.
izen says:
June 18, 2013 at 7:32 am
“And yet several posters have expressed dismay that we do not know what the cause of the Greenland melt or the varience of the jet stream might be. Are people projecting their own ignorance?!”
My post might have been a bit brief. But rgbatduke set forth the problem of attribution in great detail. I await your response to him.
izen says:
June 18, 2013 at 1:39 am
“Ascribing something to a unusual, but ‘natural’ variation is NOT an explanation, just a description. It begs the question; Why does this unusual natural variation happen, what are its causes.”
You commit what all oxford graduates know as a “Category Mistake.” Natural Variation is not a cause or a set of causes but an entirely different sort of thing. It is the range of our data from lowest to highest. For example, Mann’s attempt to “eliminate” the Medieval Warm Period was an attempt to erase an important high point in our temperature data. Mann’s attempt did not address putative causes of MWP.
Forgive me. Oxford.
“””””…..izen says:
June 18, 2013 at 4:31 am
@- Billy Liar
“When sufficient firn cores have been taken over the rest of the area of Greenland we’ll have some data.”
We already have a LOT of data on when these melt events occurred, here is a graph of them over the last 6000~ years. Note how rare they are in the last few centuries, certainly none in the 1930s or 40s.
http://www.gisp2.sr.unh.edu/DATA/alley1.html
Note how they have been related to the increased summer sun in the past with a summer perihelion, but the rising CO2 is causing a similar rise in down welling energy which, by the indirect means of altering the jet streams, has caused more surface melting……”””””
As far as I know, the melting of ice, has been directly linked to one physical phenomenon. That is the raising of the Temperature of that ice to around 273.15 Kelvins, give or take some small adjustments due to the ambient pressure, which for the ice surface, would be the atmospheric pressure, no doubt reduced from standard by the typical altitude of Greenland ice surfaces; accompanied by the input to that ice surface of a supply of energy, perhaps as “heat energy” which must (second law) come from some HOTTER material source above (or below) the ice surface. Well in the case of ice, the below surface must necessarily be COLDER, so nyet on that supplying latent heat of melting (80 calories per gram of ice). So that leaves a warmer atmosphere above for that source of “heat energy”; or that energy required for the phase change, could be supplied by EM radiation from some overhead atmospheric source.
Since photons know nothing of Temperature, then the source of that downward radiation from the atmosphere, could be either hotter or colder than the ice surface.
Now the ice surface itself is a source of thermal (black body like) EM radiation, and since we are postulating that the surface is melting, then we can presume that the effective BB Temperature of that radiation, is about 273 Kelvins, about 15 deg. C lower than the global mean Temperature of about 288 Kelvins, so the thermal emission must be less than about 315 W/m^2, appropriate for a 273 K BB radiator, and the spectral peak would be about 10.65 microns wavelength, from Wien’s law.
Now if the overlying atmosphere is HOTTER than the ice surface near 273K which it must be to supply “heat energy”, then it would be emitting a thermal radiation spectrum, but it would be far less intense than the 10.65 micron peak spectrum from the ice surface, since the atmosphere molecular density, is a tiny fraction of that of ice. So very little melting could be due to LWIR thermal radiation from the atmosphere. Then there is the re-emitted greenhouse effect radiation from the CO2, and also from atmospheric water vapor, which is likely to still be more abundant, than the CO2. But that re-emitted greenhouse radiation, originally came from the thermal emissions from the ice itself, and it would be only of the order of half of the surface emission, that is in the CO2 band (or water), since the GHG emission, is necessarily isotropic, so only half can be coming back down to the ice.
So that leaves the ice as necessarily, a net EMITTER of LWIR EM radiation, only a fraction of which is CO2 active, and only half of that can come back down.
Hence, there simply is no way that the atmosphere, and GHG effects can be supplying “latent heat energy” to the ice, to melt it; in excess of the thermal emission of LWIR EM radiation by the ice.
Now Greenland ice is quite thick and at some altitude, but I don’t see how it could possibly be in contact with jet stream air flows.
The only other possible source to provide “latent heat energy” to the ice, in order to melt it at about 273 Kelvins, is the sun itself, in the form of shorter wave solar spectrum radiation, which contains near IR wavelengths that are absorbed in H2O. H2O is most strongly absorbing at 3.0 microns, and only 1% of solar spectrum radiant energy remains at longer than 4.0 microns.
I’m left with an inescapable conclusion that only the sun can melt the Greenland ice surface, and I don’t see where jet streams come into play, unless to move cloud into or out of the picture.
Well maybe I’m missing something; my computer is far too slow to do terra-flop modeling.
Ian W
Thanks for the link. Superb stuff!
I can roll it out whenever some rabid warmist tries to tell me today’s melt is “unprecedented!” (wail, gnash teeth)
BTW I think you may be in danger of making izen rather hot-tempered 😉
Izen,
When I was scuba-diving off the coast of Western Scotland this Easter, I went looking for your ‘hidden ocean heat’ as I could have done with a bit of it. Couldn’t seem to find it though. Brrr!
(yes, I know my comment is rather fatuous, but I can’t help but laugh at rabid warmists like ol’ izen)
{ izen says:
“Americans are continuing to connect the dots between climate change and extreme weather in the United States,” said Anthony Leiserowitz, director of the Yale Project on Climate Change Communication. “They’re associating climate change with some of the major events that we experienced last year, like the ongoing drought.”
And of course they are right. }
Yeah, those Obama supporters are one intelligent bunch.
“CO2 is causing… ” [Izen at 4:31AM today]
Prove it.
No, Izen, I didn’t ask you to jump up, grab three tennis balls, and start juggling and telling jokes. Waving your hands wildly while you flounce from one side of the stage to the other won’t work, either. What do you think this place is, A CIRCUS?
Now, if you choose to throw one of your famous fits — THAT would be entertaining.
Can’t seem to work one up? Okay. I’ll help you. What is the matter with you, Izen? Are you crazy? You must be. No sane person would tell lies that made her or him look as RIDICULOUS as you are making yourself appear. Oh, I beg your pardon, you aren’t lying or insane, you’re just stupid and prideful? Well, in that case, I’m sorry — NOT! If you know that you are stupid, then you know enough to NOT POST AS IF YOU KNOW SOMETHING WORTH SAYING.
Bwah, ha, ha, ha, ha, ha, ha, haaaaaaaaaaa!
[Okay, okay, qualification — IF Izen is insane, then his or her spending his or her psychotic breaks posting on WUWT is not a laughing matter. Get help, Izen. You don’t need to do this to yourself.]
**********************************
Izen [1:46AM today]: “increasing energy which is mainly going into the oceans. The evidence for that is unequivocal and robust”
Bruce Cobb [4:23AM today]: Show your work.
Izen [4:47AM today – Izen’s “proof” for Cobb]:
1) “observation-based reanalysis of the ocean” [i.e., recycled model output “data,” a.k.a. “JUNK”];
2) “Americans are continuing to connect the dots” [whoo, hoo, that’s “robust” proof]
3) “two dozen leading scientists convened to evaluate the abundance and quality of available records of heat waves, cold waves, floods and droughts in the United States.” [no CAUSATION mechanism mentioned at all]
JM: So, Izen, you just ran really fast in the hamster wheel for — NOTHING.
Okay, okay, O Wonderful WUWT Scientists, I realize this is a science forum. LOL, you probably wonder if I am sane! Hmm. Not sure. #[%)] I’ll try to stop harassing the Izen…………. for now (heh, heh, heh).
…… but, provoking the Izens of the world is SO MUCH FUN!!!
Love this site.
Izen says:
“Its very odd… Less than twenty posts in is a video in which the leading scientists researching this subject gives a detailed description of what the jet stream is, how it works and why it is now meandering about and causing extreme weather.”
No, it’s not odd, and we know what the jet stream is. I’m not sure you do though, because if you did you would never say: “why it is now meandering about…” – it has always meandered izen, this isn’t a new phenomenon. The jet stream is a product of atmospheric turbulent dynamics. Turbulent dynamics, as described by Andrey Kolmogorov some seventy years ago, exhibits behaviour that results in low frequency variations dominating the behaviour of the process at all scales. This low frequency characteristic is often misinterpreted as some kind of causal behaviour, but such analysis amounts to the same kind of post hoc ergo propter hoc error that water diviners use to explain their “successes”.
The video showing an individual playing “pin the extreme weather tail on the climate change donkey” is amusing, but that “causal relationship” will break down in years to come, by which time the climate alarmists will have some other hand-waving explanation for why their previous prediction failed.
“And yet several posters have expressed dismay that we do not know what the cause of the Greenland melt or the varience of the jet stream might be.”
I know exactly what the *variance* is caused by, and have explained it simply and clearly. And given the importance of *variance* (as the square of the standard deviation) I don’t think I’ve ever come across a scientist who didn’t know how to spell it. But for now, I will give you the benefit of the doubt – English may not be your first language – but I suggest you read up a little on Kolmogorov’s work, you cannot understand the nature of the jet stream without it.
jai mitchell says:
June 17, 2013 at 4:09 pm
Myron Mesecke
Yes, that is basically what they are saying. A blocking pattern left a dome of high pressure over Greenland causing unprecedented melt. In the summary of the article it says, ”
————————
It was not unprecedented. It happens with regular frequency.
beng says:
June 18, 2013 at 7:44 am
Where did all that surface “melt” go last summer? Snow isn’t like rock, so it prb’ly soaked into the snow and — refroze. Ooowww, so scary…..
Yes it soaked into the snow but didn’t completely refreeze.
http://nsidc.org/greenland-today/2013/03/an-early-spring-calibration-for-melt-detection/
@- Janice Moore
“Now, if you choose to throw one of your famous fits — THAT would be entertaining.
Can’t seem to work one up? Okay. I’ll help you. What is the matter with you, Izen? Are you crazy? You must be. No sane person would tell lies that made her or him look as RIDICULOUS as you are making yourself appear. Oh, I beg your pardon, you aren’t lying or insane, you’re just stupid and prideful? Well, in that case, I’m sorry — NOT! If you know that you are stupid, then you know enough to NOT POST AS IF YOU KNOW SOMETHING WORTH SAYING.”
I am quite used to being told what I think about a subject by people convinced I ‘believe’ in Cagw and am anti nuclear power, which is always gratifying as it enables me to avoid all that hard work and deciding what I think myself.
However it is a new experience to be told how I should behave, based apparently on past actions which I must admit I cannot remember ever having done.
I did not realise that I am ‘famous’ for my ‘fits’, I thought the most egregious thing I have done at WUWT was being impolite to Richard Courtney by suggesting I would always think of him by his diminutive after he ridiculed my name.
However your accusation that I lack the knowledge to contribute meaningfully to this debate and I am merely exhibiting an example of the Dunning-Kruger effect may be better founded. Very few posters here are published Earth system scientists and the tendency to opine about matter far above our pay grade seems to be the sine qua non of WUWT.
Obviously I accept the science that is also endorsed by 97% of the literature, many here do not. May I ask what evidence would convince you to at least consider that the mainstream human understanding of the climate is largely accurate?
I am happy to explain what data or findings would cause be to have serious doubts about the current explanations of the observed warming, melting ice and ocean heat content rise.
Izen, I take it you have not yet read Kolmogorov’s work? Your words are scientifically meaningless. Take this for instance:
“Obviously I accept the science that is also endorsed by 97% of the literature”
What does this even mean? What is “the science”? Kolmogorov’s work is clearly part of “the science” yet you seem unwilling to accept that. And what is “the literature”? You mean the scientific literature? Which covers a massive range of subjects – I can assure you 99.9999% of the totality of scientific literature makes no reference whatsoever to what you are talking about, so clearly 97% cannot endorse it.
Furthermore consensus has never been a cornerstone of science – Lysenko managed to get far better than 97% of the Russian scientific literature supporting his view and rejecting the entire field of genetics. So what?
Your commentary here is vague, incoherent, flawed and, most importantly, unscientific. Was that your goal?
@- .Spence_UK
Izen, I take it you have not yet read Kolmogorov’s work?
No. Do you have a link? The only reference I can find is to a couple of books by a A N Kolmogorov on minimum energy solutions in computer vision systems.
@- “What does this even mean? What is “the science”? Kolmogorov’s work is clearly part of “the science” yet you seem unwilling to accept that. And what is “the literature”? You mean the scientific literature? ”
I think it is obvious from the context, I mention Earth systems science, that the scientific literature I am referencing is that on the physics of the surface conditions of planetary bodies. So the science of how we understand the various conditions on Venus, Mars, the moon and of course the Earth. The fact that no published paper on this subject appears on a search for Kolmogorov makes me doubt he is exactly mainstream….
@-“Your commentary here is vague, incoherent, flawed and, most importantly, unscientific. Was that your goal?”
Perhaps I was shaping my posts to be consistent with the common form here…{grin}
But I am happy to be more precise and give links to the published research if you ask.
By the way can you answer the question I put previously, can you detail what evidence would cause you to doubt your present POV and consider the mainstream scientific explanation of the present observed climate changes as correct?
I agree that the consensus does not validate the science, but the consensus is a measure of the strength and consilience of the present science.
“No. Do you have a link? The only reference I can find is to a couple of books by a A N Kolmogorov on minimum energy solutions in computer vision systems.”
Well, it’s the same guy, but he is a little better known for his earlier work, such as defining the axioms upon which the modern formalisation of probability theory is based, and developed theories of turbulent flow which still underpin analysis of turbulence in fluids today. He is perhaps one of the top 20 most influential scientists of the 20th century… and you’ve never heard of him. Wow.
“I think it is obvious from the context, I mention Earth systems science”
Firstly, if you mean Earth systems science, say so, do not refer to it as “the science”, it is vague and inaccurate. Secondly, even within earth systems science, the vast majority of the literature takes no position on this topic.
“The fact that no published paper on this subject appears on a search for Kolmogorov makes me doubt he is exactly mainstream….”
You want to study a system involving turbulent dynamic fluids and you don’t think Kolmogorov is “mainstream” enough. Ummm… okay.
“By the way can you answer the question I put previously, can you detail what evidence would cause you to doubt your present POV and consider the mainstream scientific explanation of the present observed climate changes as correct?”
I can’t answer this question scientifically because it is not posed as a scientific question. Which points of view? Which bits of mainstream climate science? Some published literature in climate science is very good. Some of it is terrible.
We can talk about specifics, and we have already done so. The jet stream is a great example. The analysis above fails to account for the stochastics in the jet stream that arise from the turbulent dynamics of the atmosphere. These define the bounds of natural variability of the jet stream. It is immediately obvious that they have not been accounted for correctly in the analysis, for example, in the video above.
This is really basic stuff. In science, your measurements and analysis are always limited by something. If you have not understood and accounted for these limits, then your analysis is scientifically worthless.