One of the interesting things about being a scientist is seeing how unexpected observations can galvanize the community into looking at a problem in a different way than before. A good example of this is the unexpectedly low Arctic sea ice minimum in 2007 and the near-repeat in 2008. What was unexpected was not the long term decline of summer ice (this has long been a robust prediction), but the size of 2007 and 2008 decreases which were much larger than any model had hinted at. This model-data mismatch raises a number of obvious questions – were the data reliable? are the models missing some key physics? is the comparison being done appropriately? – and some less obvious ones – to what extent is the summer sea ice minimum even predictable? what is the role of pre-conditioning from the previous year vs. the stochastic nature of the weather patterns in any particular summer?
The concentration of polar expertise on the last couple of questions has increased enormously in the last couple of years, and the summer minimum of 2009 will be a good test of some of the ideas that are being discussed. The point is that whether 2009 is or is not a record-setting or near-record setting minimum, the science behind what happens is going to be a lot more interesting than the September headline.
In the wake of the 2007 minimum, a lot of energy went in to discussing what this meant for 2008. Had the Arctic moved into a different regime where such minima would become normal or was this an outlier caused by exceptional weather patterns? Actually this is a bit of false dichotomy since they aren’t exclusive. Exceptional patterns of winds are always going to be the proximate cause of any extreme ice extent, but the regime provides a background upon which those patterns act. For instance, in the paper by Nghiem et al, they showed the influence of wind patterns in moving a lot of thick ice out of the Arctic in early 2007, but also showed that similar patterns had not had the same impact in other years with higher background amounts of ice.
This ‘background’ influence implies that there might indeed be the possibility of forecasting the sea ice minimum a few months ahead of time. And anytime there is the potential to make and test predictions in seasonal forecasting, scientists usually jump at the chance. So it proved for 2008.
Some forecasting efforts were organised through the SEARCH group of polar researchers, and I am aware of at least two informal betting pools that were set up. Another group of forecasts can be found from the Arctic ice forecasting center at the University of Colorado. I personally don’t think that the intrinsic worth of a successful prediction of overall sea ice extent or area is that societally relevant – interest in open shipping lanes that might be commercially important need much more fine-grained information for instance – but I think the predictions are interesting for improving understanding of Arctic processes themselves (and hopefully that improved understanding will eventually feed into the models and provide better tests and targets for their simulations).
What was particularly interesting about last years forecasts was the vast range of forecasting strategies. Some were just expert guestimates, some people used linear regression on past data, some were simply based on persistence, or persistence of the trend. In more mature forecasting endeavours, the methods tend to be more clustered around one or two proven strategies, but in this case the background work is still underway.
Estimates made in June 2008 for the September minimum extent showed a wide range – from around 2.9 to 5.6 M km2. One of the lowest estimates assumed that the key criteria was the survivability of first year ice. If one took that to be a fixed percentage based on past behaviour, then because there was so much first year ice around in early 2008, the minimum would be very low (see also Drobot et al, 2008). This turned out not to be a great approach – much more first year ice survived than was predicted by this method. The key difference was the much greater amount of first year ice there was near the pole. Some of the higher values assumed a simple reversion to trend (i.e. extrapolation forward from the long-term trend to 2008).
Only a couple of the forecasts used physics-based models to make the prediction (for instance, Zhang et al, 2008). This is somewhat surprising until one realises how much work is needed to do this properly. You need real time data to initialise the models, you need to do multiple realisations to average over any sensitivity to the weather, and even then you might not get a range of values that was tight enough to provide useful information.
So how did people do? The actual 2008 September minimum was 4.7 M km2, which was close to the median of the June forecasts (4.4 M km2) – and remember that the 2007 minimum was 4.3 M km2. However, the spread was quite wide. The best estimates used both numerical models and statistical predictors (for instance the amount of ice thicker than 1m). But have these approaches matured this time around?
In this year’s June outlook, there is significantly more clustering around the median, and a smaller spread (3.2 to 5.0 M km2) than last year. As with last year, the lowest forecast is based on a low survivability criteria for first year ice and I expect that this (as with last year) will not pan out – things have changed too much for previous decades’ statistical fits on this metric to be applicable. However, the group with the low forecast have put in a ‘less aggressive’ forecast (4.7 M km2) which is right at the median. That would be equal to last year’s minimum, but not a new record. It would still be well below the sea ice trend expected by the IPCC AR4 models (Stroeve et al, 2008).
There is an obvious excitement related to how this will pan out, but it’s important that the thrill of getting a prediction right doesn’t translate into actually wanting the situation to get worse. Arctic ice cover is not just a number, but rather a metric of a profound and disruptive change in an important ecosystem and element of the climate. While it doesn’t look at all likely, the best outcome would be for all the estimates to be too low.
“I doubt it is significant, but to me it was interesting.”
But in a scientific sense, “interesting” means “significant”.
The effects of general relativity on gravity is not interesting AT ALL to someone throwing a cricket ball.
The rotation of the earth and the coriolis force are not interesting to the ball-thrower either.
> I doubt it is significant
Look at the error bars (gray band) around the average line, that will help assess the wiggles. Remember you’re seeing daily changes posted because people want to see them, but they go up with the caveat that these results are affected by clouds, etc. and get cleaned up after a while
It might just be ice being blown around, but not reducing in density below the 15% threshold used to calculate extent. I’ve been watching Hudson’s Bay for a couple of weeks because in most years the ice would be long gone by now, yet this year it’s not. Much of what’s left is moving around a lot and the extent map at NSIDC shows this, and also the extent shrinking, growing, shrinking as it moves around and changes shape. The density maps from cryosphere today show the ice there to be mostly in the 40% or less range.
Maybe that’s happening elsewhere, too.
Barton P. Levenson
Sorry Paul but you are wrong, and here is what I wrote in full, with bold emphasis added:
Thanks for that Rod; you are correct in recognising that EMR is a different form of energy than HEAT. HEAT is transported by EMR only when there is a potential difference between two opposing sources.
Confirming that, here are some less confusing depictions than K & T 1998:
http://education.gsfc.nasa.gov/ess/Units/Unit2/u2L5aimage.jpg
http://en.wikipedia.org/wiki/Earth’s_energy_budget (containing two graphics)
BTW, there is an update of K & T 1998 here: [sorry, that should say 1997, twice]
http://chriscolose.wordpress.com/2008/12/10/an-update-to-kiehl-and-trenberth-1997/#comment-981
If you look at the NOAA and the other two examples of typical Earth’s Energy Budget diagrams, including a very widely disseminated one from NASA, these demonstrate adequately that you are indeed wrong.
The K & T version includes a confusing depiction of the greenhouse effect that should be treated just as Rod described for HEAT transfer, not as you think.
To help you understand:
Note also that if EMR going up is arrow-labelled positive, then that coming down is negative, and that there is a net result. To demonstrate; consider also that EMR travels in all directions, and typically any layer of air, is being bombarded by EMR laterally in all directions. Typically the emission power from all these lateral directions is uniform, but because they are typically equally opposing each other, they cancel each other out. (no heating takes place)
John P. Reisman, Reur 524
Concerning the erratic nature of retreat of the Jakobshavn glacier over the last ~150 years, according to NSIDC, you wrote in part:
Well, putting aside your semantics, I agree that thermal inertia may be part of the story, but it is probably trivial as elaborated later.
I’m surprised that you assert that thermal inertia IS the answer, because the NSIDC and MODIS data (although they contradict each other somewhat) do NOT support that assertion. There are many other factors in the advance and retreat of glaciers, and perhaps the most basic is the terrain in terms of gradient, channelling profile, and roughness. You do understand that glaciers can only flow if there is a net downhill gradient? According to NSIDC, this glacier has retreated some 50 km since emerging from the Little Ice Age, but in erratic fashion, and there is no correlation with HADCRUT NH temperatures. Over the length of this ~50 km retreat it is hard to imagine that the ground gradients etc were constant and that there was no variation in potential difference between the creep-gravitational driving forces from the ice sheet above and the reactive drag from below.
According to NSIDC, between 1964 and 2001 the retreat was at a comparative standstill. (for 37 years…. The greatest period of warming.)
According to MODIS, 2002 was close to 2001, (slow), but 2003 alone was a massive one-year melt before a following big slow-down. (See 541/p11 )
I’m sorry, but your emphatic; The answer is thermal inertia is wrong. (if the NSIDC data are correct). There is no way that a glacier can virtually sit there for 37 years, and then respond after sudden thermal inertia wakeup with a violent burp for just one year before then immediately going relatively quiescent again. (something else happened!)
BTW glaciers flow (creep) downhill and form large ice shelves in Antarctica, where it is very much colder.
Oh, and BTW, how does your delayed melting response in thermal inertia work in Greenland after the melt season decays; usually in September?
See also my 541 to Nick Barnes and its references.
I also agree that Jakobshavn is only a small player in the total cryosphere, however it is often held as an icon of disaster, particularly WRT the reported rising sea level concerns.
Thus it is appropriate to not cherry-pick a year of rapid retreat in 2003 according to MODIS as being significant in the longer term trend, say from 1964.
Wayne Davidson (409)
Thanks for your compliment:
“Manacker, Mark and others here understand Climate better than Lindzen.”
It’s nice of you to write this, but Richard Lindzen, Professor of Meteorology, Department of Earth, Atmospheric and Planetary Sciences at MIT, certainly knows a whole lot more about climate than either Mark or myself.
According to this site, Lindzen “is often described as the most respectable of the climate ‘sceptics’ and is frequently cited in discussions here and elsewhere. Lindzen clearly has many fundamentally important papers under his belt (work on the QBO and basic atmospheric dynamics), and a number of papers that have been much less well received by the community (the ‘Iris’ effect etc.).”
But thanks for the compliment, anyway.
Max
Rod B, Reur 542, you wrote:
[edit. too tedious – please move on to something more interesting]
Further my recent posts on that iconic Greenland glacier, you might be interested in this Encyclopaedia Britannica on-line entry that puts it into proper perspective:
http://www.britannica.com/EBchecked/topic/234619/glacier/65682/Greenland-Ice-Sheet
EXTRACT, my bold emphasis added:
“The bedrock surface is near sea level over most of the interior of Greenland, but mountains occur around the periphery. Thus, this ice sheet, in contrast to the Antarctic Ice Sheet, is confined along most of its margin… …The unconfined ice sheet does not reach the sea along a broad front anywhere in Greenland, and no large ice shelves occur. The ice margin just reaches the sea, however, in a region of irregular topography in the area of Melville Bay southeast of Thule. Large outlet glaciers which are restricted tongues of the ice sheet, move through bordering valleys around the periphery of Greenland to calve off into the ocean, producing the numerous icebergs that sometimes penetrate North Atlantic shipping lanes. The best known of these is the Jakobshavn Glacier, which, at its terminus, flows at speeds of 20 to 22 metres per day
Thus, the iconic alarming Jakobshavn glacier might be compared with a dripping tap, (faucet), versus the scale of that huge island of ice.
Here ‘tis; the relative scale of Jakobshavn to that massive ice sheet:
http://bprc.osu.edu/blogfiles/MODIS/jk/jakob_00-08_front_change_small.png
Compare with the map of Greenland in the lower RH corner!
Re BobFJ @ 555 (and others), on Jakobshaven.
Trying to correlate Jakobshaven retreat with global temperature averages is an approach which wouldn’t have occurred to me. Do you know what the temperatures at Jakobshaven have been like over the last 100 years? Why don’t you look it up (temperature anomalies for Illulisat)?
However, supposing for the moment that the Jakobshaven temperature anomaly has behaved similarly to the global one, I still don’t find the retreat pattern particularly mysterious.
Suppose the climate (in the broadest sense: temperature, precipitation, seasons, ocean currents, etc) was not changing, and there was a steady state. Then the glacier would presumably neither advance nor retreat. If the climate was static but at some warmer level, the glacier would also be static, at a different location. So there’s some function from static climate to static glacier location. Simplifying “climate” to temperature T, the glacier front position is pos(T). This function is likely to be monotonic, more or less – warmer temperatures have less ice, approximately – but I don’t expect that it is at all linear: it will depend on all sorts of things such as the bedrock topography. It’s easy to imagine a glacier front position which is pretty stable over a wide range of temperatures but then unstable outside that range: a flattish area in the graph of pos(T).
As the climate changes, the glacier will also be inclined to change, but there’s going to be some lag, which will also not be fixed. So if at time t the temperature suddenly changed to T’, then the glacier will start to change and will stabilise – probably at pos(T’) although this is another simplifying assumption – at some later time t’. The lag t’-t will depend on T, T’, and everything else (e.g. bedrock topography).
Now in the real world, the climate is never fixed. Among other changes, we’ve seen considerable warming over the last hundred years. We expect glaciers to retreat accordingly, but at any given time the position of a glacier front is not going to be a good measure of temperature. It’s going to be non-linear, and it’s going to lag. In the case of Jakobshaven, it looks as if there was a stable position for several decades, but once the temperatures reached a certain level, and stayed there for a while, the retreat continued (and will continue – as temperatures continue to rise – until it reaches a new stable position).
In short, although glacier position over long periods should be correlated (although certainly not linearly) with temperatures at the glacier, I don’t think *rate of change* in glacier position is going to be so strongly correlated with *rate of change in temperature*, firstly because of the lag and secondly because of the non-linearities.
This is all amateur guesswork on my part. I hope it’s clear.
Also on Jakobshaven, the significance of this glacier to sea level rise is the speed of the glacier. Not its retreat rate (which is much slower).
A little further reading on Google Scholar tells me that the change in 2001(ish) was the disintegration of the floating ice tongue, caused by increased basal melting from warmer waters in Baffin Bay. Before the disintegration the front wasn’t moving much but the tongue was thinning.
The remaining glacier now is grounded, not floating (although the bedrock, at least in the centre of the ice stream, is far below sea-level), so the continued retreat cannot be attributed to warmer sea water. I suppose that as the glacier continues to retreat this will expose increasing side-fronts of the ice sheet to the sea water of the fjord.
Catching up on back threads a bit, I realize that I found–but, IIRC, never cited on RC–this 2001 paper on Arctic albedo in optical and near IR wavelengths:
http://www.umanitoba.ca/ceos/files/publications_pdf/042.pdf
Hanesiak et al. seems to have some legs, scientifically speaking, as it’s been cited 20 times, according to Google Scholar.
Relevant to past discussions here is the statement that “. . . the most responsive region within this spectrum to changes in the sea ice surface is the visible (VIS) and part of the near-infrared (NIR) region (300-1100 nm).” So, yes, IR albedo–NIR, at least–is important.
The biggest takeaway point generally is probably the fact that this is a very serious observational study measuring actual albedos in situ, and that a major part of its purpose is to improve parameterization of albedo in models. (Ie., make sure that the models are as realistic in this regard as they can possibly be.)
Secondarily, one might note the widely varying albedos measured for different terrain types. IIRC, the original context of this whole discussion thread was an argument from first (or at least, basic) principles that the albedo changes resulting from sea ice melting don’t really matter–or not much. This argument was, I think, answered in considerable part by the point that solar zenith, even at the pole, exceeds angles for which the reflectivity coefficient approaches .5. (See: http://en.wikipedia.org/wiki/File:Water_reflectivity.jpg–although this graphic assumes temps of 20 C. At the pole, solar zenith is around 23 degrees.)
But the study I’m pointing to here also seems to provide empirical support for “my” idea that NIR radiation–which presumably wouldn’t be affected by the angle of incidence issue at all, since it’s emitted uniformly in the lower atmosphere–might be a significant in the melting process. (BTW, I’m quite sure the idea is “mine” only in the context of this particular discussion. Unlike some, I don’t assume that because I never thought of it before, no researcher has either!)
For purposes of this idea, it would be nice to know what the spectrum of the downwelling IR characteristically looks like, WRT to how well it matches up with the spectrum Hanesiak et al are talking about. I searched, but so far did not find. Can anyone point to that data? (Wayne, how about you, since you were just referencing the lack of IR monitoring this year?)
Finally, this interesting paper from 2007 is among those citing Hanesiak et al: http://www.ub.uit.no/munin/bitstream/10037/1909/4/paper_2.pdf
It notes that some (few) GCMs do incorporate “spectral and solar angle dependencies.” But it presents a parameterization for ECHAM5 which, the authors state, will be “the first time the albedo of melt ponds are treated explicit[ly] in any GCM.” It should also be mentioned that the intent is to reduce the under-prediction of Arctic melt trends by GCMs, which we have discussed here on RC in the past. The authors believe that the discrepancy between observed and predicted melt trends may be due to inadequate treatment of albedo within GCMs, resulting in GCM albedo values that are biased high.
Nick Barnes (560) and Bob_FJ
Just calculated the average Illulisaat winter (Jan-Feb-Mar) and summer (Jul-Aug-Sep) temperatures for the 20-year periods 1928-1947 and 1986-2005 (last year listed).
http://www.cru.uea.ac.uk/cru/data/greenland/illulissat.dat
Both summer and winter temperatures were significantly warmer in the earlier period than in the most recent period.
1928-1947
-11.8 winter
+6.6 summer
1986-2005
-15.5 winter
+5.7 summer
Ouch!
So much for a “temperature response” in the most recent glacial retreat. Back to the drawing board.
Max
#556 Manacker, However impressive Lindzen’s credentials are, he has failed predicting anything about present warming conditions. Although he confirms lately that the climate is warmer, nice of him to do so… He steadfast refuses guarantee his predictions, or if he did faintly tries, he fails…….. I read him a few years back that the climate will cool as it inevitably will do so. Assured by ignoring climate science, The man has a lot of nerve to criticize successful predictions, based on models which have done so, And therefore is a classic example that stature is meaningless unless its reinforced by credible accomplishments as achieved elsewhere.
The topography of Greenland has been discussed quite extensively here in the past. The Brittanica entry isn’t news in this forum, nor is the relative scale of Jakobshavn (spellings seem to vary) to the island. I seriously doubt that anyone’s point about Jakobshavn is that it’s going to “drain” Greenland all by itself.
BTW, it’s great to have the recent posts & inline responses back. Thanks to the contributors/IT team! Is the preview function going to come back as well? I like to check with it, especially when, as above, I try to use HTML–I have a pretty high error rate in HTML usage!
“…high error rate in HTML…”
I guess so–my link to the Wiki reflectivity graph should have been:
http://en.wikipedia.org/wiki/File:Water_reflectivity.jpg
“#409 Wayne Davidson says:
29 July 2009 at 14:05
#400. Manacker , Mark and others here understand Climate better than Lindzen… Because they understand AGW while Lindzen pretends he doesn’t….”
…
#556 manacker says:… “Thanks for your compliment”
Spin? Punctuation problem?
Max, if you want more back-handed compliments, you’re also smarter than BobFJ ;-)
Sorry Bob…
Nick Barnes (560)
You wrote:
“Now in the real world, the climate is never fixed. Among other changes, we’ve seen considerable warming over the last hundred years. We expect glaciers to retreat accordingly, but at any given time the position of a glacier front is not going to be a good measure of temperature.”
The average annual temperature at Illulisaat over three 20-year periods was:
1900-1919: -4.8C
1928-1947: -2.7C
1986-2005: -4.4C (2005 is last year of record)
It is certainly true that glacial retreat is not tied to temperature, but we have not really seen considerable warming over the past 100 years (if we exclude the early 20th century warm period of the 30s and 40s).
Max
#566 The topography of Greenland – there isn’t but few glaciers to drain the ice, and the most important of those are up north… so it (the massive melt down) isn’t going to happen so long as the arctic sea ice is holding it (GIS) back… partial ice sheet calving events during summers are likely when the arctic sea ice diminishes enough, but it is not going to be very rapid – in the scale of tens of years (unlike WAIS), or so I see it. But I’m not studying GIS nor WAIS, so this is just another (somewhat, I’d like to think) uninformed opinion on the subject…
Actually the 1930s-40s warm spell over Greenland is well known from the record…
So no, it’s not local air temperature.
#555 BobFJ
I think I see where the confusion is here? In your post #509 I saw the gist of the item as:
Thus you were presenting Jakobshavn in the sense of the paradox between the “greatest prolonged period of warming” and slower glacial retreat, and the current “more rapid melt in recent years” having “occurred during the current warming pause”.
My ‘answer’ was a reply to the paradox. That generally speaking the best or most reasonable answer is likely ‘thermal inertia’.
In your post #555, you are looking at the behavior of Jakobshavn more specifically. My earlier reply, ‘thermal inertia’ was the answer in consideration of the lag time between forcing and oceanic absorption of the forcing energy in the ocean system, which slows down the rate of warming in relation to total forcing capacity.
My answers tend to be general in nature in order to address global warming response mechanisms, or considerations. One glacier does not tell the whole story.
BTW, I agree that the possibility of ‘something else happened’ is interesting, but I do tend to focuc on the big picture not the personality of a single glacier.
As to
I am referring to the long term signals, not inter-annual melt and refreeze.
As to Jakobshavn’s role as an icon of disaster? Humans have long sought the means to protect themselves from danger, thus the industrial iconic phrase canary in a coal mine, though I’m sure there are many similar phrases in the history.
I tend not to cherry pick, but look at the pieces in context of the bigger picture
https://www.realclimate.org/index.php/archives/2005/03/worldwide-glacier-retreat/
It may very well be, or even most likely is that Jakobshavn is the canary in the cryosphere. When fitted in the big picture it it may be more than iconic, but rather, or most likely is, prescient of our future.
Wayne,
To Lindzen’s having “a lot of nerve to criticize successful predictions, based on models which have done so.”
Which predictions and models in particular are you referring to? (And, please, it’s only a question, not some implication that there are none.)
Walter
BobFJ, after a long discourse on why I’m wrong that losing electromagnetic energy cools an object [!], adds:
K&T used what’s called a radiative-convective model (RCM) of the atmosphere, Bob. That reduces the energy-transfer problem to one dimension, accounting for ignoring solid angle by multiplying the optical thicknesses of each layer by a “diffusion factor” usually equal to 1.66. This is adequate to represent the real situation to within a few percent. K&T and me and the climatology community are right about this and you are wrong. Evapotranspiration does not dominate the cooling of Earth’s surface. Period.
P.S. I’ve been writing RCMs since about 1998.
#574, Walter, any one, and I mean any one, a kid, a teenager, a plumber, who understands the basics of GHG’s, will predict more or less an impossible to stop warming to come unless there are volcanic event or some world wide changing phenomenon. Even Lindzen if he bothered to debate here , would be forced to admit, that this graph:
https://www.realclimate.org/images/Hansen06_fig2.jpg
is mighty impressive. So if he cares to impress, start predicting… Correctly…. At least once….. Even at the pub! No bets necessary…. (that should help a reputation in the normal academic world not hindered by stupid money)…
576, Wayne, thanks, though not really an answer to my question (not that one is required!) and I had thought the Hansen A,B scenarios vs. observations to be a fairly contentious subject these days (it certainly was last year at the 20th anniversary). – Walter
More ice (ok, less, apparently):
http://www.guardian.co.uk/environment/2009/aug/06/america-glacier-melt
On a semi-related note (regional ice behavior) Bob_FJ pointed out the excellent Environment Canada ice site and by extension its Ice Graph interactive data extraction program.
The Canadian site is oriented mostly around navigational and other human interaction impacts of ice. Because of that, Ice Graph allows the selection of regions of coverage extending from rather small to nearly the entire purview of Canada’s ice-impacted navigation scene. Super-coverage including individually extractable areas of sub-coverage can be selected, allowing the source of apparent trends to be followed more closely. I’ve been noodling around with Ice Graph and am impressed with how the decline of ice in confined areas isolated from open water is noticeably less dramatic than areas with larger “fetch”. For instance, the Northwest Passage is not showing a great deal of loss, whereas Lake Michigan appears to be undergoing a more obvious decline in recent years.
Another nice feature of Ice Graph is the ability to define what period of record keeping establishes “normal” ice coverage.
Something here for everybody interested in sea (or Great Lakes) ice, regardless of prejudice.
http://ice-glaces.ec.gc.ca/IceGraph/IceGraph-GraphdesGlaces.jsf?id=11874&lang=eng
You are welcome Walter , is it contentious because it is right? Placing myself in the eyes of a novice at this subject, its pretty convincing that this science is at a high degree of precision. I put it to all again, in the past (19th century) , it was fair to say no one knew for sure GT temperature leanings, now this cant be said. Whether scenario A or B or C is a bit off is irrelevant with my main point, this current warming was foreseen in 1988, all while fuddle dudle contrarians gesticulated climate obscenities, not heresies, heritics offer substance. No contrarian can predict anything because they were/are oblivious to this success, they preclude what was learned on purpose, and they offer nothing good.
Barton Paul Levenson, Reur 575, you wrote in part:
Sorry Paul, not what I said. There IS indeed a net HEAT loss from the surface resulting from the difference between up-welling and down-welling EMR (infrared). EMR is a different form of energy to HEAT, but can transfer HEAT to a lower potential between two opposing sources.
Here is an extract from the link below, defining this, using Stefen Boltzmann‘s law:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
http://www.nzifst.org.nz/unitoperations/httrtheory5.htm
Radiation between Two Bodies
The radiant energy transferred between two surfaces depends upon their temperatures, the geometric arrangement, and their emissivities. For two parallel surfaces, facing each other and neglecting edge effects, each must intercept the total energy emitted by the other, either absorbing or reflecting it. In this case, the net heat transferred from the hotter to the cooler surface is given by:
q = ACs (T14- T24 )
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If the symbols are not reproduced OK, the part of the equation fundamental to the discussion is:
(T1^4 – T2^4) which is that classic potential difference found in all energy transfer equations , for instance (T1 – T2) in conductive heat transfer, or (H1 – H2) in hydraulics, where H2 is the lower height.
The following impeccable sources are in agreement with the above. If you are convinced that they are wrong, why don’t you launch a campaign to have corrections made. (and to the accepted physics out there)
http://education.gsfc.nasa.gov/ess/Units/Unit2/u2L5aimage.jpg
http://en.wikipedia.org/wiki/Earth’s_energy_budget (containing two graphics)
Martin Vermeer Reur 572:
Good point, but others here have tried to deny that record when it was raised earlier.
Nick Barnes, Reur 560, 561, 562.
Thanks for the very interesting observations, and you confirm that it is a very complex dynamic in such a long ~50km retreat over some 150 years. (per NSIDC)
My main point remains that the very rapid retreat in 2004, (per MODIS), should not be taken as alarming evidence for disastrous climate change, either regionally or globally.
Furthermore, Jakobshavn is atypical of all other glaciers as far as I’m aware.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Max, Reur 564;
Great stuff…… as you say Ouch!
579 Wayne, thanks again, and to: “This science is at a high degree of precision.” If by precision you refer to the accuracy of projections, that may prove to be the case as the models keep improving. To point out that Scenarios A or B (C is moot) are a bit off, though, hardly illustrates that high precision. Today’s models, it would stand to reason, are better than 1988’s, but if 30 years is the climate standard of choice, as is often stated, then the best we can point to in observation are the hindcasts. Was warming accurately foreseen in 1988? To the extent that observed slopes were more often positive thereafter than not, rather than flat or negative, then yes, but a cynic could argue: “33% odds”. It strikes me that the observed data are less compelling than the ongoing accumulation of puzzle pieces supporting AGW theory. But that’s only a lay opinion, clearly at odds with the more informed mainstream, and we are far afield from my original question about Lindzen’s climate expertise or lack thereof. Walter
> http://education.gsfc.nasa.gov/ess/Units/Unit2/u2L5aimage.jpg
That’s a picture of an equilibrium condition.
We aren’t in one.
jyyh Reur 571, you wrote in part:
May I suggest that floating sea ice is easily pushed around, even by wind, and offers trivial resistance to glacial discharge. The dynamics of glaciers depend largely on gravitational gradients, and, the complexities of topography and a few other complications have been discussed above. (See for example Nick’s 560, 561, & 562). Something I forgot to mention before in the gravitational aspect was that the ice domes are around 3000 metres (3km) above sea level. Although they are a long way from the coast, the fact is that ice creeps slowly and inexorably under the effect of gravitation, (regardless of air temperature), and the forces exerted must be enormous. (for instance they carve huge glacial valleys in the rock)
Nick Barnes (560) and Bob_FJ
The apparent disconnect between local temperature and glacial retreat at Illulisaat (Greenland) intrigued me, since it went against everything one reads in the general media.
So I took the basic monthly temperature record and converted this to annual average temperature, to see if there is a connection. (I did 5 samples correcting each month for the number of days, but this showed less than 0.05°C difference from just taking the arithmetic monthly average, so I stayed with the arithmetic average).
http://farm3.static.flickr.com/2620/3797223161_16c1ac5e39_b.jpg
Over the entire period (1900-2005) there was actually a very slight cooling. The linear cooling over this entire period was 0.1°C. So one can say that thee was no warming at Illulisaat over the 20th century.
What surprised me even more is that the first half of this period (1900-1950) showed a fairly strong linear warming of 2.3°C, while the second half (1951-2005), when most of the CO2 greenhouse warming effect should have taken place, showed a linear cooling of 0.4°C.
Is the glacial retreat we are now observing the delayed result of early 20th century local warming?
(At any rate it is certainly not the result of late 20th century local warming, because there was none.)
A dilemma.
Max
Wayne Davidson
In your 565 you wrote:
“However impressive Lindzen’s credentials are, he has failed predicting anything about present warming conditions.”
Further to Walter Manny’s basic question on Lindzen’s criticism of successful model predictions, which you failed to answer in your 576, here are my comments.
“Present warming conditions”? It has not been warming since 1998 and has been cooling since 2001.
IPCC (and Hadley) have “failed predicting anything about present cooling conditions” (or “interrupted warming conditions”, as some prefer to call it).
Now let’s look at Lindzen’s “failed predictions”.
Lindzen has estimated that a doubling of atmospheric CO2 should lead to a theoretical greenhouse warming of from 0.5 to 1.2 degrees centigrade (all other things being equal).
Let’s take the arithmetic average of 0.85°C.
Atmospheric CO2 level was around 290 ppmv in 1900 and in 2000 it was 369 ppmv. Using the logarithmic relation to adjust Lindzen’s estimate for the CO2 increase over the 20th century, we arrive at 0.3°C.
20th century warming was 0.65°C. Solar studies put around half of this attributable to the unusually high level of solar activity. If the rest is due to CO2 alone (forgetting ENSO, other GHGs, aerosols, etc.), we have 0.3°C left for CO2.
Forgetting “heat hidden in the pipeline”, etc. we have a pretty close “prediction” from Lindzen.
Max
PS If you’d like links to the solar studies, I’ll be glad to provide them.
[Response: This is just rubbish – you know that it’s rubbish, I know that it’s rubbish and Lindzen knows that it’s rubbish. It’s just the kind of superficially plausible rubbish that you can use on people that don’t know any better. For the sake of people reading, the missing elements are the changes in other factors such as aerosols and the difference between transient and equilibriurm sensitivity. Lindzen is well aware of the uncertainty in aerosol forcing – he mentions it all the time – so assuming that it is exactly zero as in the above calculation without mentioning the uncertainty is dishonest. He is also aware of the thermal inertia of the oceans – he has even written a paper about it – so again giving the impression as in the above calculation that it is zero is dishonest. If you are going to go back to playing games, go elsewhere. – gavin]
Excuse me for mentioning this, but won’t the rates of outflow of Greenland’s glaciers matter less in the near future as more and more of the ice sheet itself turns into water?
[Response: Actually no, the vast majority of mass loss from greenland is from the outlet glacier ice rather than surface melting and this will be the case for a very long time. – gavin]
583 Walter, He has lots of expertise, I never argued that. But applies himself very little in climate science. On purpose, making wild allegations, hinting about Arctic alligators during the holocene.
I unquestionably praise the temperature model predictions done in the 80’s. You are grasping at straws when you argue against it.
Before we are stunned by Manackers prowess with physics, lets read Lindzen:
“Lindzen also stated that the global mean temperature has not increased since 1995”
“to cool in the next 30 years”
“Richard Lindzen says he’s willing to take bets that global average temperatures in 20 years will in fact be lower than they are now”
to cool… “probably within the next few decades.”
“Professor Lindzen had been willing to bet that global temperatures would drop over the next 20 years”
“global average temperatures would cool back down in 20 years.”
All this said for several years going back a while… He did state in a news article a few years back, that it will be cooling in 4 to 5 years
Coming FRom Lindzen I am truly not confused…. Is it warmer? Or is warming? Or is it going to be cooler… He is right climate is unpredictable, perhaps in some rooms at MIT.
As Max wrote:
“Present warming conditions”? It has not been warming since 1998 and has been cooling since 2001.”
Well, June 2009 2nd warmest in history? Rings a bell? Is this cooling since 2001? As I recall June 2001:
Temperature anomaly +0.55 C June 2009 +0.77 C….. I digress, since I require clarity.
Sorry, Gavin, what I wrote in 587 to Wayne Davidson is not “rubbish”, just because you may not personally agree with it.
Lindzen has predicted 0.85±0.35°C equilibrium greenhouse effect from doubling CO2 (from 280 ppmv to 560 ppmv, for example). Would you agree that this is what he has predicted or would you prefer that I cite the reference?
Adjusting this for the 20th century increase in CO2 we arrive at a theoretical equilibrium GH warming from CO2 of 0.3°C. Would you agree with this?
IPCC has told us that the climate forcing (1750 to 2005) from other anthropogenic factors (other GHs, aerosols, land use changes, etc.) essentially cancel one another out so that we can ignore them for now. This is spelled out in SPM 2007, p.4. Total net anthropogenic forcing is stated to be 1.6 and forcing for CO2 is stated to be 1.66 W/m^2. This is roughly equal. Would you agree with this?
The solar studies conclude that around 0.3°C of the total 20th century warming can be attributed to the unusually high level of solar activity. I will give you the references, if you wish. Most of the studies attributed a higher level of solar warming during the early 20th century warming than during the last 30 years, but the average over the entire 20th century was a bit over 0.3°C
The Hadley record shows that there was 0.65°C linear warming over the entire 20th century, i.e. from 1901 through 2000. (IPCC TAR and SPM 2007 called this 0.6°C, but the actual Hadley record shows 0.65°C). Would you agree with this?
I believe the only open question is whether or not there is still some warming from the 20th century increase in atmospheric CO2 still “in the pipeline”. I do not have an answer on that, but the point was made by Wayne Davidson that Lindzen was a poor predicter of 20th century GH warming from CO2, and I believe the figures show that he did not do too badly.
If you have better figures, please bring them so I can get educated.
Max
#590… Max, I would, sincerely, absolutely review your reasoning, if I were you… I would look at :
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/ARCHIVE/20010806.png
2001 when your claim it has been cooling ever since; Really?? Sea ice utterly denies your reasoning….
http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png
Need it melt more?
Wayne: “I unquestionably praise the temperature model predictions done in the 80’s. You are grasping at straws when you argue against it.”
I’ll stop. Thanks. — Walter
manacker August 2009 at 11:26 AM
“IPCC has told us that the climate forcing (1750 to 2005) from other anthropogenic factors (other GHs, aerosols, land use changes, etc.) essentially cancel one another out so that we can ignore them for now. This is spelled out in SPM 2007, p.4. Total net anthropogenic forcing is stated to be 1.6 and forcing for CO2 is stated to be 1.66 W/m^2. This is roughly equal. Would you agree with this?”
Sorry, I can’t help but ask: Can we take from your reliance on IPCC data that you are in substantial agreement with the IPCC report for policymakers?
Or is it just this part you agree with:
“The understanding of anthropogenic warming and cooling influences on climate has improved since the Third Assessment Report (TAR), leading to very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming, with a radiative forcing of +1.6 [+0.6to +2.4] W m-2.”
Walter….. how reasonable! Thanks…. When success is denied, some must defend it fiercely!
Congratulations to all.
You have all been very successfully played.
We are nearly at 600 posts on this topic, and almost all of them are postings or responses to Bob_JF with a few more to Max, posters that could easily be identified as trolls after one or two posts, and yet you all took hours of valuable time to respond to them, to let them take over the whole thread.
The world is dissolving before us and you, the intellectual elite that society has privileged with access to special knowledge and leisure, have chosen to squander these gifts on obviously insincere distracters.
Meanwhile the rest of the world is left scratching our heads. Is the Arctic about to be ice free? What will be the consequences for human and non-human life?
I guess these questions are totally stupid and totally irrelevant to your superior intellects, and you far prefer to banter about minutia with posters that are probably paid to do exactly this–derail really crucially important discussions about crucial topics with people who have the intellectual ability to shed some light on them.
I used to think this was a valuable site. Maybe I misjudged. I don’t plan to return any time soon. Thanks for knowingly wasting my and doubtless thousands of others time in trying to follow your hapless and naive sparing with shadows.
manacker (sigh) typically makes a claim about what’s said — claimed to be found on p4 of the SPM
Let’s have a look at p.4.
Where are you seeing what you claim to quote?
Give us a link, please, to whatever you’re relying on for what you claim to see.
Or see if you can find it — are you looking at this?
Climate Change 2007: Synthesis Report
Summary for Policymakers
http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf
Nope.
Page 4 is a global map and a figure caption for it.
How about page 5? Well, there’s footnote 6:
6 … Increases in GHGs tend to warm the surface while the net effect of increases in aerosols tends to cool it. The net effect due to human activities since the pre-industrial era is one of warming (+1.6 [+0.6 to +2.4] W/m2) ….
So that doesn’t match what Max / manacker is claiming is said.
Source, please, for what you claim and why you’re relying on your source.
So far, Max, every time I check what you claim is a fact, it’s not there.
it seems the melting has stalled. The graph is moving away from the 2007 line towards the 1979-2000 line. It looks like falling short of 2008.
Re 590: “If you have better figures, please bring them so I can get educated.”
Max, it has been pointed out to you many times that it is wrong to say “It has not been warming since 1998 and has been cooling since 2001.”
And yet strangely, you have not managed to educate yourself about this.
So you don’t need to pretend that you are here to learn. We know you are not.
596
Hank, it took me seconds to locate the iconic radiative forcing chart on page 4 of the SFP, with which the most cursory reader of the AR4 is familiar. That you ended up elsewhere is understandable, but will you withdraw the triumphant “sigh”.
http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf
Walter
> stalled
riiiiight
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.365.jpg