Models are improving, but can they catch up?

All models are wrong, but some are useful, as the saying goes. However, when looking at how Arctic sea ice decline is modeled, one might be tempted to say that all sayings are useful, but some are wrong. To be fair, I should be the last person taking a piss at climate models. Hundreds of brilliant scientists, engineers and IT specialists are giving their best every day to make supercomputers come up with scenarios that project future changes. Unfortunately, there is no Planet B to experiment on.

But we have come to a point where fake skeptics show up in television programmes (such as last week's BBC Newsnight) and use modeled predictions for Arctic sea ice in the 2007 IPCC Fourth Assessment Report as an argument not to be worried about the disappearance of Arctic sea ice, because "none of them shows it melting before the year 2070 on a regular basis in the summer" (quote from UK Conservative MP Peter Lilley).

As always, they're not telling the whole story:

This image (taken from the Climate Crocks blog) comes from a GRL research paper by Stroeve et al. that was published in 2007, detailing how models that participated in the World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (CMIP3) were doing compared to observations (red line). The 2011 dot was drawn in, based on NSIDC data on September 7th of last year. Commenter Tim took the liberty of drawing in the new 2012 record. This picture saves us the 1000 words needed to explain how off models are when it comes to matching observations, which essentially makes their projections worthless.

But as the Arctic sea ice cover has changed radically in just 6 years, so have new and improved models started a new round of simulations and projections for the Phase 5 project (CMIP5) for the next IPCC assessment report. And again, Dr. Julienne Stroeve and her colleagues from the NSIDC, NCAR and the Voeikov Main Geophysical Observatory in Russia, have taken a look at how these models are faring in a new GRL paper that was published three weeks ago in Geophysical research Letters: Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations.

From the introduction:

The rapid retreat and thinning of the Arctic sea ice cover over the past several decades is one of the most striking manifestations of global climate change. Previous research revealed that the observed downward trend in September ice extent exceeded simulated trends from most models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (CMIP3). We show here that as a group, simulated trends from the models contributing to CMIP5 are more consistent with observations over the satellite era (1979–2011). Trends from most ensemble members and models nevertheless remain smaller than the observed value. Pointing to strong impacts of internal climate variability, 16% of the ensemble member trends over the satellite era are statistically indistinguishable from zero. Results from the CMIP5 models do not appear to have appreciably reduced uncertainty as to when a seasonally ice-free Arctic Ocean will be realized.

This is a very interesting paper that is easy to follow. Two metrics are used to evaluate the performance of CMIP5 climate models: 1) The distribution of simulated extents over the period of observations (1953-2011) is used to assess how well the models capture the observed state of the ice cover, and then 2) Trends in simulated ice extent are used as a measure of the ability of the models to capture the response of the ice cover to global climate change. Quote:

It is possible that a model can capture the historical state but not the trend. We compare results of these evaluations to those based on the CMIP3 simulations. The CMIP5 models will become the main source of climate projections assessed by the International Panel on Climate Change (IPCC) in its 5th Assessment Report.

Two scenarios are used for the 56 ensemble members from 20 climate models in the CMIP5 archive: The representative concentration pathway (RCP) 4.5 future emission scenario, that stabilizes radiative forcing at 4.5 W m-2 in the year 2100, resulting in approximately 550 ppm of CO2 by 2100. The other scenario is the same CMIP3 20th century and future “business as usual” (SRES A1B emission scenario) model output. A1B attains CO2 levels of 750 ppm by 2100 and is hence a more aggressive scenario than RCP4.5. Models with more than 75% of their distribution falling outside the observed range of 6.13 to 8.43 million km2 were rejected. Of the 20 CMIP5 models, 17 models were retained, resulting in a total of 38 ensemble members.

Here's how things look for modeled, observed and projected September mean sea ice extent in the 1900-2100 period:

Figure 2. Time-series of modeled (colored lines) and observed (solid red line) September sea ice extent from 1900 to 2100. All 56 individual ensemble members from 20 CMIP5 models are included as dotted colored lines, with their individual model ensemble means in solid color lines. The multi-model ensemble mean is based on 38 ensemble members from 17 CMIP5 models (shown in black), with +/- 1 standard deviation shown as dotted black lines. Figure inset is based on the multi-model ensemble mean from CMIP5 and CMIP3, +/- 1 standard deviation.

I haven't drawn in this melting season's result, but it will obviously fall outside the 1 standard deviation of the CMIP5 multi-model ensemble. Some ensemble members are even lower, but that's because they started out much lower than the actual observations.

Results are described as follows in the paper:

Based on multi-model ensemble mean extents at the beginning of the 20th century, there is a 1.1 million km2 difference in the mean September extent between CMIP3 and CMIP5 (Figure inset, N.). During the period of satellite observations, the September CMIP5 multi-model ensemble mean tends to be slightly lower than the observed extent until 2007, after which it is higher. By contrast, the CMIP3 multi-model ensemble has a positive bias throughout the period of observations and especially during the most recent decade. Turning to the end of the 21st century, the CMIP5 multi-model ensemble mean never reaches ice-free conditions (defined here as less than 1.0 million km2), but the minus 1 standard deviation drops below the ice-free threshold around year 2045. Several CMIP5 models (CanESM2, GISS E2-R, GFDL-CM3, NCAR CESM, MIROC-ESM and ESM-CHEM) show essentially ice-free conditions by 2050, with the CanESM2 model having an ensemble member reaching nearly ice-free conditions as early as 2016 (0.54 million km2). By contrast, despite the more aggressive emission scenario (SRESA1B) driving the CMIP3 models, an overall more extensive sea ice cover is retained, with the minus 1 standard deviation reaching nearly ice-free conditions in 2075.

The same thing was done for March mean sea ice extent, with the following result:

The lower CMIP5 March extent compared to CMIP3 results in good overall agreement with the observations, though the observed values fall below the CMIP5 multi-model ensemble means in recent years.

Stroeve et al. also test whether the observed trend falls within the distribution of simulated trends at a specified level of statistical significance:

Turning to the modern satellite era, 1979-2011, more CMIP5 ensembles have a smaller rate of decline than observed, which at -0.84 million km2 per decade is nearly twice as large as the trend for 1953-2011. Forty-six of 56 ensemble members have trends outside of the 2 bound for the observations and 9 ensemble members have trends that are not statistically different from zero at the 90% confidence level. Although most model trends remain slower than observed, six ensemble members have rates of decline larger than observed. Overall, 64% of the ensemble member trends are statistically different from the observed trend at the 90% confidence level. In contrast, 85% of the CMIP3 ensemble members have trends that are statistically different from observed. The multi-model ensemble mean trend over the satellite period is -0.50 million km2 decade, which is 70% larger than the CMIP3 multi-model mean value of -0.35 million km2 decade.

It's clear that the CMIP5 models do a better job than the CMIP3 models used for the 2007 IPCC Fourth Assessment Report. But better is not the same as good. In this case 'less bad' would be a more accurate description. If Arctic sea ice continues melting at this rate, the question arises whether there is any sense in trying to optimize models. By the time they capture all the processes that are involved in melting, transporting and compacting the Arctic sea ice cover, it might already be gone. Maybe some of the money and human intelligence that go into models could be better spent on observational purposes (satellites, buoys, moorings) and the consequences that disappearing Arctic sea ice is already producing: changing weather patterns, methane release, permafrost melt and erosion.

As for the new IPCC report coming out next year: This time, a crazy melting season that shatters all previous records occurs just before the deadline and not after it. Will the seriousness and potential danger of an ice-free Arctic be reflected in the relevant chapters? Or will the IPCC again be too conservative (see this piece by Bryan Walker on the Hot Topic blog), hiding behind models that still haven't caught up with reality? The (lead) authors have their work cut out for them, but I'm sure they'll do a good job. We'll see what happens then.

Thanks goes out to Julienne Stroeve for allowing me to cover her important paper. Dr. Stroeve is currently in the middle of the ice pack to survey ice conditions and collect validation data (more on that later). To share her experiences she has started a blog: Ice Edge 2012

Comments

[Werther]

Welcome back, Neven,

As I was digesting some info, I saw your new thread article and thought 'why not be the first?'
This is on SST's, I'll read your models-article ASAP.

www.ssmi.com/sst/sst_data_daily.html?sat=tmi_amsre

Thanks to Keeper of the Gate / Wunderground I found these wonderful pics on SST.
I think I’ve seen some links on ho to get this as a layer over Google Earth, so it probably isn’t new to some of you.

The North Pole pic doesn’t show anomaly. But you bet; Hudson Bay, especially James Bay are warm. Same goes for the Kara Sea (going Atlantic) and the shallow part of Laptev Sea. Baffin Bay also quite light blue. And look at the coastal Beaufort Sea! As a side note, Lake Superior makes a good swim.
Only the ESAS up to the Pevek Bay Siberian coast is cool.

This matches the general warmth distribution this summer.

For a take away; there is some snow on Brooks Range, on Wrangell Island, on mountains around Pevek Bay and high in the Verchoyansky Chrebet (the mountain range ending near Tiksi). But it is much, much less than last year. And no snow at all in the Gory Byrranga, Taymir, 74 dG N, that is tale-telling.

[Neven]

Hi, Werther. I'm still not back, but will be the day after tomorrow. I'm grateful for the minimum to not have occurred, because doing an ASI update with this 56K modem would get me killed by my wife ("we're supposed to be on a holiday, you know?").

[Misfratz.wordpress.com]

If Arctic sea ice continues melting at this rate, the question arises whether there is any sense in trying to optimize models.

It does currently look very likely that the September sea ice will all be gone before the models are reasonably competent at predicting its disappearance. However, it is still worth improving the models because:

(a) It will become increasingly important to forecast the timing of the seasonal Arctic sea-ice melt, as more trade uses the North-West passage and Northern sea route. Being able to do this a couple of weeks in advance could be very valuable.

(b) Related to this, the big ice-albedo feedback kicks in with sea-ice declines in the months of May, June and July, and not September. These months give the models longer to catch-up.

(c) Knowledge gained by modelling the Arctic sea-ice will be useful when modelling the Antarctic sea-ice, and possibly also the Greenland and Antarctic ice sheets, as well as other myriad smaller ice shelves.

All that said, it is much easier to improve a model when you have detailed and accurate observational data to compare it against, otherwise you are flying blind when trying to work out why the model is failing to produce the right answers.

[FrankD]

I agree Misfratz, but ...

"It does currently look very likely that the September sea ice will all be gone before the models are reasonably competent at predicting its disappearance."

...made me think of the famous Niels Bohr quote: "Predition is difficult, especially about the future..."

;-)

[Seke Rob]

Which reminded me of "The road to Perdition"

('twas of course "Prediction is very difficult, especially about the future" :)

[crandles]

It is also worth improving the models because it is very useful to have the CMIP5 models in order to know an expected shape in order to extrapolate sensibly. So far the models are suggesting a sigmoid shape (like gompertz). It is useful to know this else you are just left with a large range like https://sites.google.com/site/arctischepinguin/_/rsrc/1345012383469/home/piomas/piomas-trnd1.png

Further improved models may give us better idea of where things begin to level out.

Just because the models seem biased, does not mean they are not useful.

[crandles]

I thought it was Yogi Berra, but apparently

"It's tough to make predictions, especially about the future.
A variant of this has also been attributed to physicist Niels Bohr, but the Danish version has been tracked back to Markus M. Ronner in 1918 by lundskovdk-citater."

[Arcticio]

I don't even understand the efforts invested in this paper. Extent is just the wrong metric to compare. Ice thickness will be zero long before extent. And the models have thickness data, or how do you calculate the energy needed to melt 5 million km² of ice?

[Billy JM]

Arcticio, you read my mind. What point is there to all this focus on extent? The modelling that needs to be perfected is Sea Ice Volume. If PIOMAS is correct, minimum volume is 80% less than 1979, and nearly half what it was in 2007. A paper-thin 'extent' of ice will be irrelevant if there's no volume to back it up. These genii need to focus on where the real issue lies - not area, not extent, but volume.

[Neven]

Arcticio, Billy JM, at the end of the paper it is stated:

As a next step, we will compare early 21st century modeled ice thickness distributions with thickness distributions based on NASA ICESat and Operation IceBridge missions.

[Jim Williams]

It's nice to see the Scientists apply some Science to the Alchemy of Predictive Climate Modelling.

(What's going on north of 85 between about 60E and 165E anyway?)

[Wipneus]

So far the models are suggesting a sigmoid shape (like gompertz).

Not all models. For instance the MIROC* models (Watanabe JAMTEC) seem to hit zero and stay there.

You must look at the individual realizations and *not* the ensemble means. Those means will have a sigmoid-like shape even if the individual runs have not.

[Al Rodger]

This Stroeve & Barrett pdf presentation compares PIOMAS with the CMIP5 models on pages 18 & 19.
http://www.cesm.ucar.edu/working_groups/Polar/presentations/2012/stroeve.pdf

[David Chase]

Getting the models right is important. Whatever melted that ice ahead of "schedule" might do the same for permafrost, hydrates on the ocean floor, and Greenland (or it might not -- wouldn't you like to know?)

[Jim Williams]

Getting models like PIOMAS right is important, but I'm inclined to see predictive modelling as a misleading distraction at this point. Until we can accurately predict what the world looks like today there's no meaning to predictions about tomorrow.

We can predict that things are going to get worse faster than we can figure out how they are going to get worse. That's all we need to know about the predictive models.

The unknown unknowns have won.

[Devi869]

The models should have been totally redisigned when we found out that during the holocene thermal maximum there was little if any ice in the summer in the arctic. HTM was as warm as today. Like Hansen, I prefer to trust the paleoclimatic data than models.

[Andre Koelewijn]

This makes me wonder what to expect about the timescale on which the Greenland ice sheet and the Antarctic ice sheet could melt.
Current projections of sea level changes may prove to be (far) too optimistic as well...

Ever thought of how many people now live at a level of no more than 10 metres above current mean sea level? And how 'organised' the required mass relocations can be?

[wayne]

Very good expose Neven. Except I like to see what the models show in an animation series. First off the mark do they replicate the certain pattern of ice extent melts , especially "the look" which keeps some sea ice towards NE Siberia until mid august? Secondly
do they have cyclones crossing the North Pole more often as times goes on? Third do they have open water halocline thickness right?
And so on..... Many of us here can help by finding quickly if "the look" of animated melts is totally wrong. I suspect the big surprise here is not from the sea but from the atmosphere where as Arctic Ocean winters are obliterated by Cyclones crossing its "air space" as if the North Pole was like in the hurricane lanes in August. Many thanks nevertheless. Perhaps the latest animation is out there, lets take a look.....

[Jim Williams]

Andre, are you talking about the projections based upon the now discredited "slow change" hypothesis? All the projections I ever see for Greenland are the same 'millennial' guesstimates I saw as a child.

[Yazzur]

Andre:

The number of humans living within 10 meters of sea level seems to be in the range of 600+ million.

http://sedac.ciesin.columbia.edu/gpw/docs/McGranahan2007.pdf

[Espen]

Maybe we should start a relocation service?

[Misfratz.wordpress.com]

What's going on north of 85 between about 60E and 165E anyway?

It's melt Jim, but not as we know it.

The point about extent is that it is the best observed measure of sea-ice. If there were thirty years of satellite ice thickness observations then I'm sure it would be used more often.

[Bosbas]

Neven, thank you for maintaining this wonderful site. It really inspires. As for the dot you added for 2012; it seems it points at 2015; shouldn't it be moved further to the left?

[anthropocene]

imho, when the history of AGW comes to be written one of the major mistakes noted will be the over reliance and too much emphasis being put on computer models. Too inaccurate and too easy to attack by skeptics. Hansen and Alley seem to have realised this and now only focus on the paleoclimate record - after all the earth is the best model for the earth. IIRC antarctic ice sheet started to appear when C02 dropped below 450ppm. From current observations, summer arctic ice disappears at approx. 390-400ppm. GIS presumably disappears somewhere between these two: 400 and 450ppm. Do we need to know anymore than these three numbers?

[Bernard J.]

Espen at September 17, 2012 at 15:15.

Sadly, I think that there's insufficient time and resourcing for an orderly relocation effort, when those days in the near future soon enough arrive.

However... I do volunteer Watts, Lindzen, Spencer, Bastardi, Morano, Plimer, Carter, Monckton and a host of other Denialati to go to the affected regions and assist in any way that they are able, as a very partial penance for consciously and actively participating in the unnecessary destruction of the planet's climate.

They will of course be required to wear names badges.

[Seke Rob]

hmmmm, not in favor of *badges* for historical reasons. Special pointy hats though, that will stand them out so all from afar can see where they are would suite me fine.

[Lennartvdl]

"From current observations, summer arctic ice disappears at approx. 390-400ppm. GIS presumably disappears somewhere between these two: 400 and 450ppm."

Those paleo-data seem to indicate that 400 ppm (Pagani et al) was not crossed the past few million years, or even the past 15 million yrs (Tripati et al), with sea level 15-25 meters higher and no GIS and WAIS, or at least much smaller.

Hansen himself thinks 350 ppm (crossed in about 1988) was the point when Arctic sea ice started its self-reinforcing decline, or maybe even earlier. Because of the inertia in the system we're seeing the effects of that today, with much more in the pipeline. To have prevented the Arctic decline, and the polar amplification as a result of that, we should have probably kept the concentration at least below 350 ppm.

[Paddy]

I was thinking that next year might be even more important than this year to the debate. Right now, the anti-anthropogenic argument seems to have crystalised around the claim that "it's just fluke weather this year", since this is the first individual year that's gone below the 2007 extent. If next year bounces back a little bit, like 2008 did, they may just get away with that argument for a while. If, on the other hand, the 2013 extent is even lower than this year, they'll probably have to abandon that line and move back to the tried and tested "Things are getting warmer, but it couldn't possibly be anything to do with emissions, and we reject any suggestion that this ice melt could be a bad thing anyway".

The question is: what extent is likely in 2013? With no model having accurately predicted the current fall that I'm aware of, I've really no idea. But which side of the 2012 extent it ends up, and how far to either side, would seem to be pretty key to both how fast the future ice collapse is likely to go, and how the debate is likely to go this time in 2013.

[Aaron Lewis]

There are models, and there are models. In 2002 when I pointed out that the very well tested Deming control models suggested that there would be major Arctic sea ice melt within a decade, I was called an "Alarmist" and told to go read the climate change literature.

I had read the literature. I first worked on atmospheric circulation models at NCAR in 1964, I worked for Jay Forrester on the Club of Rome Report (as a Dynamo programer), had been Senior Scientist at Bechtel; retired, and in 2002 was consulting at Bechtel on environmental issues. However, in 2002, the big names in climate science, were not interested in somebody that went back to the basic science. They had their peer reviewed models, and they believed them. They still believe them.

At this point, all of the simulation models fail because they underestimate the amount of water vapor in the Arctic. As the NH cools this fall; it will precipitate out as snow. That snow will keep extant ice warm and weak; snow will keep the ocean warm, snow will keep perafrost from refreezing, and will limit sea ice formation. (Limited sea ice formation means less rejected brine to cool the clathrates on the sea floor.) however, the mass of water in the snow is small, and thus the snow will melt rapidly next spring. Thus, there will be open water next spring and an Arctic Low will form again next summer. The feedbacks from water vapor / snow will be more intense in following years. Within a very few years there will be very limited sea ice during periods of high insolution (June 21).

Moreover, in the past, water vapor was condensed out before it got to the Arctic proper. In the Arctic, latent heat was not not a factor. In the old days, heat in the Arctic was from insolution. Now, heat from the south is imported across the Arctic as water vapor. Now, we have to think of the entire NH as collecting heat for the Arctic.

The difference in required forcing between a seasonally ice free Arctic Ocean and a year round ice free Arctic Ocean is less than the feedbacks from a seasonally ice free Arctic Ocean. That is: when we get to seasonally ice free Arctic Ocean, we are committed to year round ice free Arctic Ocean as the system comes to equlibrium over a period of 50 or 100 years.

People that say it will take much longer than a century, are not thinking about the North Pacific and North Atlantic as sources of latent heat that can move freely into the Arctic. The changes in atmospheric circulation that such heat flows will drive are not going to be good for industrial agriculture.

And, if you think like a mine engineer, and do a structural analysis of the GIS with moulins, and account for the structural strength of ice at various temperatures, then the GIS does not melt in place, but undergoes a progressive structural collapse resulting in a ice/water slurry with large horizontal velocities.

[Yazzur]

The relocation of 10% of the worlds population is an unimaginable task, and I don't know how it would be possible to allocate the resources to accomplish that task.

What we see in the Arctic indicates to me that it is possible, though it still seems unlikely, for Greenland and WAIS to contribute sufficient melt to see a 5-10 meter sea level increase within the century. I think the modeling is of critical importance to see if climate change can (will?) impact Greenland and WAIS that amount. If the models start to provide evidence of a chance of a 10 meter increase in sea level, then the Herculean task of planning for the relocating 5-10% of the worlds population and the infrastructure to service them would need to be done. Not to mention the changes to the water and food supply chain that would have to occur concurrently. It makes a real difference relocating, say, 2% of the worlds people verses 10%.

[dorlomin]

The problem with using paleo is that the holocene thermal optimum was caused by the orientation of the axis changing so that it was Northern Hemisphere summer when the earths orbit was closest to the sun.

This would have changed the thermal equator and had a very large impact on high latitude northern hemisphere summers and also winters, as the winters would have notably weaker insolation than today. Paleo can give an indication but the forcings are likely to play out very differently as winter will warm faster than summer and all kinds of other effects that have not been thought off may yet come into play.

Expect the unexpected, this includes counter intuitive things like perhaps places getting colder or snowier, more precipitation may thicken in the NH winter snow packs and perhaps slow the warming rate in spring, perhaps not.

Well anyway, models will have advantages over paleo because we are in rather different situation (warmer winters and colder summers as the background and CO2 acting different to insolation changes)

[Neven]

As for the dot you added for 2012; it seems it points at 2015; shouldn't it be moved further to the left?

Yes, it should, but the big arrow is in the way.

Don't take that graph too literally, I just try to convey the general trend. Else I would've made more of an effort. It's ugly as hell now. :-)

[Arcticio]

Above is from the presentation Al Rodger linked to. It shows PIOMAS volume versus CMIP5 Models. And even if you compare to CryoSat and IceSat instead - the picture is not getting better. I wonder, whether there are other consequences the models are 50 years too late.

[Lanevn]

Are there somewhere free icevolume data (numerical)?

[Bruce Worden]

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.

[OldLeatherneck]

Quoting Arcticio: I wonder, whether there are other consequences the models are 50 years too late?

Most current models for global sea-level rise call for annual increases of about 3.5mm. Considering that Greenland alone has probably lost that much mass in 2012. Coupled with extensive mountain glacier retreat, Antarctic mass loss and thermal expansion I'd say that we need a new baseline for every predictive model for sea-level rise.

[islandraider]

Aaron Lewis, thank you for the detailed post concerning water vapor. Question (tried to answer online): what is insolution?

[Fairfax Climate Watch]

Aaron Lewis, your statement is very convincing! I agree.

[Seke Rob]

Probably a typo, islandraider. In context of the line it would be "insolation", which would be maximum around June 21.

[Al Rodger]

Lanevn,
If the PIOMAS data page doesn't show a way to what you want, try this link below. The data is daily from 1979.

http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ice_volume/PIOMAS.vol.daily.1979.2012.Current.v2.dat.gz

[Al Rodger]

Yazzur,
The maximum Sea Level Rise this century is something I have had a few dust-ups over in the past.

The literature is quite definite in putting a maximum increase below 2 metres by 2100. There are a few dessenters to this view, which include none other than Jim Hansen.
An SLR of 2+ metres is pretty much impossible today by melting alone. The limiting factor is energy. So much energy would be required to be channelled to Greenland or Antarctica to melt that amount of ice - it simply isn't possible.
To achieve such a level of melt, you would actually require either a massive amount of extra climate forcing with no warming or some global cooling to increase the TOA energy imbalance. It sounds bizarre, but that is how it is.
It should be said 2+ metre/century SLR is not impossible. SLRs above 2 metre have been shown since the last glacial maximum. One mechanism that still could achieve such a high rate today is the collapse of an ice sheet causing a massive calving of icebergs. And this would not require melting to create the SLR (although voyaging off in search of the sun, the icebergs would cool the planet, increasing the global energy imbalance and thus assist in their quicker melting).

Where Jim Hansen is correct is that we will continue to have large SLR century-on-century unless human emissions are reduced. The end-game would be an eventual 70 metres of SLR inundating 90% of present human endeaveour although that would require millennia to happen.
(I can reference this screed if anyone's interested.)

[Jim Williams]

I'll add my agreement on Aaron's post to that of others. Question: what is "Deming control models"?

[Richaburton]

Great post as usual Neven. Can't believe these guys aren't trying harder to keep up and be more realistic. Three things I've been giving thought to recently:

1.
There was a post about a week ago regarding the DMI Daily Mean Temperatures North of 80 degrees. I have been eagerly watching this graph since and it still shows no sign of the temperature dropping significantly north of 80 degrees. In fact DMI can be thanked for having such a public archive of their graphs going back to 1958. I think I am correct in saying, after having looked through the historic data and compared it to all previous years, that no other year has held temperatures as high this late in the year North of 80 degrees.

Following the last post on this topic a number of comments were given regarding why 2012 has such anomalously high temperatures in the 'high arctic'. There were suggestions regarding the open water, which I believe is the most likely cause. These were then related to the fact that the remaining pack ice is now small enough to act more like an island than a continent. This means 'on shore' breezes i.e. blowing from the sea into the ice pack are holding up temperatures over the entire pack as it is now so small.

2.
Bruce Worden has already mentioned the insolation changes will have a massive and largely unknown impact on future shrinkage of the pack. The increased absorbtion of solar energy due to the lack of the albedo effect over the open water (used to be sea ice) is now causing the temperatures to remain higher later in the year. It's interesting that the temperature is now holding at about -2 deg C (roughly the freezing temperature of ice). This could mean the latent heat of freezing is being given off holding up temperatures, so a drop is imminent. In the past this hasn't been an observable plateau and the temperature has just plummeted, probably due to the ice pack acting in a more 'continental' fashion in previous years due to the larger area covered by ice. This means it could just be coincidence especially as the graph covers such a large area encompassing open water (relatively warm) and ice (below freezing). Food for thought though.

3. Neven, I looked at the Ice edge 2012 Blog by Julienne Stroeve. It's interesting to note the post from the field on September 11th. I quote, "According to the satellite data, we should have already reached nearly 100 percent ice concentration, yet at 83N, the ice concentration remains less than 40 percent."

Could the ice area/extent actually be being underestimated by the satellites? Gotta love this season due to the interesting changes from the norm, but I have to keep reminding myself that everything I'm witness to is actually a sad side effect of our pollution and the pig ignorance of our governments. They are the only ones who can get together and make an appreciable difference!

[Yazzur]

Thanks Al,

With Hansen predicting up to 5m, and recognizing the arctic ice melt models appear overly conservative, it's a subject I'll need to look at closer.

Adaption to 2m will be expensive, but nothing like 5m.

[Arcticio]

Richaburton: They are the only ones who can get together and make an appreciable difference!

Not exactly, most polluting countries are democracies. You get the government you vote for.

[Seke Rob]

"You get the government you vote for"... and thus fully deserved to sit in your own mess.

[Tim]

Neven,
I took the liberty of updating the Climate Crocks figure, putting 2012 in its proper position:

http://i713.photobucket.com/albums/ww133/Sane_Person/Arctic%20Meltdown/Sea_Ice_models_v_reality-2012.jpg

You're welcome to it. (I'm assuming Peter Sinclair approves.)

[Enno Zinngrebe]

Hi .. i also want to give thanks to Neven for this fine post. I tend to think if a model isnt good enough the appropriate thing to do is to make a better model. No science bashing from me :)

But I want to add a rather humorous paper that is very fitting to this thread.

http://www.the-cryosphere-discuss.net/6/2653/2012/tcd-6-2653-2012.pdf

"The fully-coupled climate model HadGEM1 produces one of the most accurate simulations of the historical record of Arctic sea ice seen in the IPCC AR4 multi-model ensemble. In this study, we examine projections of sea ice decline out to 2030, produced by two ensembles of HadGEM1 with natural and anthropogenic forcings included. These ensembles project a significant slowing of the rate of ice loss to occur after 2010, with some integrations even simulating a small increase in ice area."

This is just published in the journal for summer 2012. I tip my hat to these folks for having the guts to unabashedly publish their model´s call for an ice increase in the face of the biggest ice collapse we have seen yet. This paper is really quickly superseded by nature. But there, but for the Grace of God, ...

in fact it is an interesting little read - mentioning a rare negative feedback:

"A negative feedback effect by which rapid reductions in ice thickness north of Greenland reduce ice export is found to play a major role."

Maybe this is a hint to where the odel goes wrong.

[Jim Williams]

Al Rodger, the problem with your argument is that there is quite a bit of evidence that it has happened in the past.

Other than my preference for evidence over theory, I strongly suspect that there are large stores of energy in the oceans which the people making these claims have ignored. I see no reason to pay any attention to their claims that "it cannot" given their obvious predictive skill so far.

[Chris Reynolds]

Thanks Neven.

[Protege Cuajimalpa]

A problem with the Arctic Sea Ice models is that they try to predict what is going to happen, from a conservative point of view.
There is a saying (in Spanish but I translated to English) that says: “Think badly and it will go well”. It’s a saying that is important at Engineering. You don’t design a ship or an airplane to resist the “average” storm. You have to think in the worst scenario that your ship or airplane is going to face, and then, you design them to resist it. But in Global Warming, we have IPCCC, UN and several scientists, thinking what forecast will better describe the “average” behavior of the Arctic Sea Ice. And then we have all those deniers, that they have good money in their wallets because there are strong interests behind, trying to make the forecasts as “no problem” as possible. So at the end, we just have political speeches, talking about the danger and doing nothing about it.

[Kevin McKinney]

The point of the models is really not prediction, but understanding. If the goal of understanding is reached, it will be worth it... but evidently there is a good bit more to understand yet.

Will the models catch up? Sure, if our civilization is granted enough time. Though it will probably be at <1m km2 sea ice extent.

[Richaburton]

Arctico and Seke Rob.

"You get the government you vote for"

May I point out that even in a democracy the government I vote for may not get into absolute power and thus I don't necessarily get the government I vote for. Besides, living in the UK I'll comment on the Green Party as an example of a party that might make a difference. Even if the Greens did get in then I doubt it would make a significant difference to the UK let alone the world.

The point I was making is that for there to be a significant change the governments of the world need to unite, accept we're going down the wrong route and all agree to make drastic changes to their countries. If it is a united front the people will see the enormity of the challenge we face, and thus be more likely to accept those changes.

[Richaburton]

Ice Edge 2012 blog had an interesting post today from Julienne Stroeve:

"I have been surprised by the vast expanses of open water that we came upon after entering the ice. The average ice concentration of the last five days has been about 65 percent, with about 36 percent of that ice being first-year ice, 14 percent being multiyear ice and 10 percent being brash ice (small broken ice floes). Air temperatures have been above freezing, even at 82.82N, 15.16E, so that there have been no new ice formation observed the last five days."

Remarkable that the weather is still so warm near the pole.

[Karl]

It would be global apart from the matter of that 'extra' million square kilometres of ice down in the Antarctic right now, where's the model for that? Of course next year will be a challenge, especially if another Arctic storm doesn't appear. Can't wait!

[Paddy]

Karl,

1m sq km more winter Antarctic sea ice is less important than 4m sq km less Arctic summer sea ice, for the following reasons:

1) 4m vs 1m
2) Winter sea ice doesn't affect the Earth's albedo the way Summer sea ice does
3) The rising Antarctic sea ice trend is taking place along a declining Antarctic land ice trend, producing a rather confused total effect in the Antarctic, whereas the declining Arctic sea ice trend is taking place alongside a declining Arctic land ice trend, showing a clear total decline in the Arctic.

As for next year: it will indeed be interesting, as I said earlier. We've several reasons to think it'll be another low sea ice extent in the Arctic, however:
1) Warming trend
2) Positive feedback loops (lower albedo; increased methane and CO2 release; perhaps also increased shipping and drilling)
3) Little ice left, and what there is is thin, so not much to build from over this winter

Set against that, there isn't much except the possibility of interannual stochastic variation. Which can be fairly considerable - I wouldn't be at all surprised if 2013 proves to have a higher sea ice extent than 2012's new record (the same happened the year after the last big drop - see 2007-2008 data here http://nsidc.org/images/arcticseaicenews/20111004_Figure3.png). I would, however, be pretty surprised if it proves to have a higher sea ice extent than 2011, and very surpised indeed if it's higher than 2009.

[www.google.com/accounts/o8/id?id=AItOawn4S99JJRLrNfgA838BLqx0pzoN7lqRBgI]

Karl: Antarctic sea ice is seasonal, it melts back every year. Until now Arctic ice hasn't been.

[Arcticio]

RichBurton: If it is a united front the people will see the enormity of the challenge we face, and thus be more likely to accept those changes.

It is just the other way round: Democracy requires participation. You can't expect your government doing the right thing while you stay quite and others demand loudly. This is accepting dictatorship of the rabble.

[Lanevn]

Al Rodger

Ty, that's what i need.

[Arcticio]

Karl: If you point to Antarctica I'll point to Venus, there is zero ice due to CO2 plus no life at all.

So, let's focus at the place where changes are actually happening and will have severe consequences very soon. And be assured you don't want to see Antarctica melting at the same rate as the Arctic.

[Dominik Lenné]

about Aarons post: The humidity - snow cover - mechanism is compelling. Now arises the question: are there observations of increasing snow cover thickness in winter?

[Richaburton]

Arcticio,

That's why I tell everybody I can about this blog and all the data you can find on the Arctic ice melting. Spreading the word and opening everyone's eyes' is the most important thing. I even teach youngsters about it and how they need to think about how they are going to modify their lifestyles.

Quiet is the last thing 'I' am, but you have actually hit the nail on the head with your comment "..... and others demand loudly." The problem is that the 'old guard' are too numerous. More people like myself and others on this Blog need to speak out and keep trying to make a difference.

Despite all this though it is the governments who need to wake up and until we 'the general public' make them we're screwed. So take your negativity, put downs and dictatorship rubbish and channel it elsewhere. Start putting your efforts into doing something positive about AGW instead of having a go at people who are trying to do the right thing.

If you plan on responding to this post with more provocative rubbish you'll be waiting a long time for the reply.

[Sch1st]

@Enno,

Thanks for the interesting paper. It should be noted, however, that the authors conclude the slowdown indicated by their models is unlikely. The authors are simply trying to understand the processes that explain the slowdown indicated by the models. This is necessary to improve models or to understand potential surprises in the future.

[Twemoran]

Richaburton

Take a look at the arctic.io web site before you criticize.

His Satellite and Split Zoom features are the best resource on the internet for ease of comparative viewing, his editorials spot on and his Daily Graphs are a must read.

The only one I know of that may do more to educate the public is Neven, and between them they've done more than you or I could dream of.

I can't imagine staying current without both resources.

Terry

[Conrad Schmidt]

Why don't these models use 1979 reality as a starting point?

[Arcticio]

Richaburton,

I'm sorry, if that figure of speech did offend you. However, assuming any government will listen to the people not speaking to them and has 'to wake up', is simply denial of your responsibility as a citizen. And if that offends you too, I can live with.

[Account Deleted]

why people keep on bringing up Antarctic sea ice baffles me.
I am no expert but surely it is simple as this.
ordinary water ice melts at 0 degrees C.
the Antarctic ice sheet is made up exclusively of ordinary water ice. warming climate is melting this ice depositing large amounts of fresh water into the Antarctic seas. Fresh water melts more easily than salt water and also freezes more easily. so if the sea is less saline it will freeze quicker and more than seas at "normal" salinity.
So to my mind it is inevitable that the more warming takes place the more sea ice there will be until such time as air temperatures remain above 0 degrees C year round.

[Account Deleted]

the same logic does not however apply to the Greenland ice sheet as that ice predominantly gets dumped at lower latitudes into the Atlantic and Baffin bay where it does not have the potential to significantly affect the North pole and Arctic sea.
Snow run off from Siberia is not relevant either is that is a stable annual factor not a new influence.

[Mdoliner43]

Is anyone else having nightmares of kilometer thick chunks of Greenland ice sheet breaking off under torrents of melt-water that washes them into the ocean where they make a whole series of tsunamis. No? Good.

[LRC]

Models are very important to the understanding of any field of knowledge. Even if they are wrong, dissecting where they go wrong can still help understand what is actually happening. So the next part of the question is can they catch up? There are 2 parts to that 1)how much in love is the modeler with his original model. The 2nd one is the big one. Costs. It takes money and time to develop any model and unfortunately because in the immediate future there are very few lives at stake (unlike severe storms), very few dollars to lose due to damage and too far away all this amounts to very little pressure on the public or private groups to send much on learning more about the Arctic.
Of course this will all change when the sea levels do start rising and the weather because too costly to insure against and people start demanding answers (much too late of course).
If other fields of research are any indication, no one model will be the definitive model. It usually takes a variety of models and approaches to help give a more complete picture as to whats the real story is and on top of that there is no chance of ever getting an accurate model or group of models because there is always something more to learn. Does that mean I think we should just stop trying for the perfect model? No! Because without modeling we will learn nothing and that will lead us to a situation like the Dark Ages which I do not think anyone wants to return to.

[Mdoliner43]

Is anyone else having nightmares about kilometer thick chunks of Greenland Ice sheet calving off under the pressure of torrential melt water and crashing into the ocean to produce multiple tsunamis. No? Good

[Janne Tuukkanen]

Philip, that's the theory. But has there been any empirical evidence of surface water salinity decrease around Antarctica? One day I looked for the stuff, but didn't find anything. SSS maps didn't show any trend at first glance neither.

[Bruce Worden]

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...

[LRC]

@ Janne Tuukkanen: This probably belongs somewhere else but this could be part of the answer of why you see salinity uniformity.
http://www.thelivingocean.net/2012/08/ocean-study-reveals-carbon-not-sinking.html

[George Phillies]

Antarctic melting, absolute worst case analysis: Suppose the entirety of our solar power input became available for melting the Antarctic, in the sense that the temperature over the globe dropped to 0.1 C and all excess solar energy were magically transported to Antarctica to melt ice; what is the upper limit on how fast the ice melts?

You have to supply the heat of fusion, and Sol only supplies so much a year, of which a certain part in the end does not melt ice and re-radiates into space.

Times much shorter than this are wrong via energy conservation.

I infer that this time is not the time mentioned above, which was the time given that the energy has to reach Antarctica to make it melt.

Comments?

[Bfraser]

@George Phillies

I think the answer is "instantly" (given your rather magical assumptions).

The volume of the Antarctic Ice Cap is ~25M km2 and the volume of the ocean is @1.3B km2. That's a ratio of over 40:1. Since the heat of fusion of ice is roughly 80cal/g, the average temperature of the ocean would need to be about 2C. Looking at this graph and noting that the average depth of the ocean is only 4000m, I'd say there's probably enough heat right there.

http://www.windows2universe.org/earth/Water/temp.html

[Dan P.]

George -

Sadly there's a major loophole to that kind of calculatation, which others have discussed here. Ice shelves can destabilize by sliding off Greenland or Antarctica. The result in an extreme case could be a sea filled with icebergs, which is the way you get around the actual physical melt rate. Sadly seas rise just as readily in that scenario.

It is my understanding that paleoclimatology supports these very high destabilization rates, although the most detailed scenario I saw described a saddle collapse that was specific to the much bigger ice-age continental sheets. We can certainly hope that there's no easy mechanism for such a collapse in today's ice sheets but we're obviously due for all sorts of accelerated melting even if we luck out on the ultimate timescale.

It turns out that the dominant source of Antarctic melting already is the quickening of glacial flow, apparently due to warm seawater melting the underwater portion of the ice sheet and reducing its ability to buttress the glacial flow behind it. Here's a nice recent paper I found that I don't remember being discussed here:
http://www.nature.com/nature/journal/v484/n7395/full/nature10968.html

The faster-moving glaciers are of course still melting out in the sea. In the extreme iceberg-filled world you could also plausibly melt ice much faster than AGW solar gains by cooling the world's oceans (as icebergs floated further and further towards the equator). Honestly though once the sea level damage is done the melting itself seems secondary.

[Hydrohopster]

"Is anyone else having nightmares of kilometer thick chunks of Greenland ice sheet breaking off under torrents of melt-water that washes them into the ocean where they make a whole series of tsunamis. No? Good."

This seems a distant yet real concern to me, a casual observer.

[Neven]

I took the liberty of updating the Climate Crocks figure, putting 2012 in its proper position:

Thanks a lot, Tim! I'll update the post with it.

[GeoffBeacon]

Last year I wrote to the Connie Hedegaard, the European Commissioner for Climate Action to say that “the science used in formulating climate policy is out of date and seriously underestimating the scale and pace of climate change.” Reply from on of the officals said

When making judgements about individual pieces of research we defer to the considered opinion of the IPCC (Intergovernmental Panel on Climate Change), which brings together thousands of experts globally to review all the relevant scientific literature. For any comprehensive re-evaluation of climate change research, we will rely on IPCC review processes and in particular the upcoming Fifth Assessment Report. We are actively engaged with these processes which will produce new comprehensive climate assessments in the coming years.

Surely this means that that EU climate policy is badly out of date ?

Can I urge European readers of this excellent blog to contact their Members of the European Parliament to ask Connie Hedegaard for further explanation?

[Account Deleted]

Janne Tuukkanen

KISS principle!

I have no sources for data on this. to me it is simple logic not needing validation beyond the reality that the sea is freezing more in a warming world. It is those who wish to challenge this logic that need to get their data out and prove it is not a real mechanism.

[Protege Cuajimalpa]

Have you seen the latest images of Bremen? It is my imagination or there is a continuous melting at the Arctic basin, in front of the East Siberian, Laptev and Kara Seas? When would this melting stop? In a couple of days we will have another Record Dominoes, for the longest time that the melting continues…

[Lewis Cleverdon]

Neven - your question of whether the models can catch up is actually about the mindset of the modellers. A simple extrapolation of observed ASI extent loss by 2000 would have given an incomparably more accurate forecast than the median of the AR4 projections - and that failure was the modellers' choice, not the available maths.

Putting orthodox theory before observation seems to me a pretty poor sort of science, and given the continuing kant about summer ice loss 'perhaps by 2030 to 2050', it would appear that doctrine is pretty impervious to blatant failure.

Yet there is the added difficulty of the number of interactive self-reinforcing variables rising, along with a rise in random contributory events, making the dim prospect of reliable modelling of arctic ice and carbon stocks' destabilization simply vanishingly remote.

Mass-loss from the Greenland Ice Cap has to be a major case in point. Having risen at an average of over 10% per year for the last decade, if that exponent somehow held steady, the cap would be cleared down to a huge land-locked melt-lake by 2080. There are multiple known feedbacks powering that exponent, some of whose internal thresholds are unclear, including:
- rising air temperatures from global warming, from a warming Atlantic, and from a warming Arctic Ocean under increasing ice cover loss;
- rising extreme insolation from the emerging annual phenomenon of the Greenland Summer High;
- rising precipitation from the northward migration of rainfall, of which an increasing fraction is falling as rain, with both a direct heat transport effect, and an increased lubrication effect via moulins, and a destruction of reflective snow cover over the darker ice cap;
- rising fallout of soot and other particulates from shipping causing cryoconite melt holes across the surface;
- rising incidence of very large numbers of minor earth tremors (reflecting just the mass-loss so far) further mobilizing the glaciers.

If we were to fail to apply effective timely Albedo Restoration measures across the Arctic Ocean, most of these factors would be further accelerated by the ongoing acceleration of the mega-feedbacks present in the arctic as sea-ice loss progresses, and as they start to interact with eachother.

While I don't predict a 'sans Geo-E' clearance by 2080 - if only because mass loss would be reduced to melt-water only once the cap declined to a shallow dome over the island's central depression and gradient to passes between encircling mountains was lost - I see no reason to pretend that the mass loss exponent will stay as low as 10% prior to that point. But the chances of anyone usefully modelling those interactions under the prevailing reductionist science seem to me just nebulous.

In short, scientists are either going to face up to adopting the precautionary principle and the need to promote the worst-case scenario (as every military strategist does as standard procedure) or they are liable to be more of a hindrance than a help as the mega-feedbacks take off.

If one starts from the premis that the purpose of science is the service of humanity, it could be argued that the failure to adopt the precautionary princple as the basis of prediction is essentially unscientific.

Regards,

Lewis

[VaughnA]

"And, if you think like a mine engineer, and do a structural analysis of the GIS with moulins, and account for the structural strength of ice at various temperatures, then the GIS does not melt in place, but undergoes a progressive structural collapse resulting in a ice/water slurry with large horizontal
velocities."--Aaron Lewis
Aaron, it sounds like this would cause giant tsunamis.
I live on 100 meters of layered sediments left from the series of Missoula Floods. I live near a road cut that exposes about 10 layers of this sediment about 20 meters high. The thickest layer is about 3 meters with most others being 1 to 2 meters thick. I first recognized these as flood deposits in 1961 when I was still in grade school. I finally put it together about 2 or 3 years later when I saw Dry Falls in eastern Washington. I finally read about the Missoula Floods (www.pbs.org/wgbh/nova/megaflood/) in about 1968 and everything made sense. I recently talked to a farmer from eastern Washington in the Yakima Valley who said he had a canyon which exposed about 100 layers of Missoula Flood Sediment.
Similarly, I suspect that ice dams will build up in numerous valleys in Greenland. I takes very little water to float ice if it rises in cracks and collects at the bottom of the ice sheet. When the water rises high enough the ice will float dammed by the dam in the valley which will catastrophically collapse. i see no reason why this could not happen with minimal or even no water exposed on the surface releasing Possibly 1000 km^3 or more of ice and water causing large tsunamis. There is evidence that these types of floods have occurred in many places at different times over history like the St. Lawrence Seaway http://geology.gsapubs.org/content/38/4/383.full

Oregon State University
http://wave.oregonstate.edu/
has carried out tsunami research that suggests that these types of tsunamis would be indeed very large.
Aaron, your comment about "large horizontal velocities" from an ice collapse in West Antarctica imply an even larger tsunami than from Greenland.
I personally consider these types of events likely if not imminent but not sure how soon.
Hopefully someone with more knowledge of ice sheet disintegration than I can help provide some answers. Also if this does happen how large do you think some of these tsunamis would be? So, Mdoliner43 this is something I have been thinking seriously about since I read about it in Scientific American circa 1993.

[wayne]

Protege, It depends of the cooling rate where the remaining sea ice is, at the moment the greatest cooling is over the Canadian Archipelago, where I am, surface sea water is warmish, above 0. No Grey ice yet. But that can happen when the winds drop. Solid ice happens when sst's are -1.8 C. I suspect it will be a while because of persistent cloudiness almost everywhere in the Arctic.

[Protege Cuajimalpa]

Using the image that Tim actualized, we can see that the shrinking of summertime ice is now about 50 years ahead of the climate model projections:
https://docs.google.com/open?id=0B2LnyvgsEMtOUkNkY21PdXRCVmc
On “Melting snow and ice, A call for action (page 36)” they talk about 30 years:
http://www.regjeringen.no/upload/UD/Vedlegg/klima/melting_ice_report.pdf

[Al Rodger]

"Mass-loss from the Greenland Ice Cap has to be a major case in point. Having risen at an average of over 10% per year for the last decade, if that exponent somehow held steady, the cap would be cleared down to a huge land-locked melt-lake by 2080."

Can we perhaps keep this thread in the real world? There is some 3.6 million cu km of ice on Greenland. It would take 1,200 ZJ to melt it. The current global imbalance is substantially below 10 ZJ pa. So if somehow tomorrow you magically got all that imbalance from around the globe and concentrated it all on Greenland you cound melt it down to the bedrock by 2130. And if you think that is possible, do explain the mechanism. Dropping ice sheet summits, accelerating glaciers: they do not come close for the Greenland Ice Sheet. Neither does more sun, more rain or more soot.

The melt on Greenland is massive. It is significant to future Sea Level Rise (where 510 cu km melt = 1mm SLR). Net ice loss from Greenland in 2011 was 370 cu km. Net ice loss has been increasing at 33 cu km per year according to the GRACE data. The 2012 loss will be spectacularly greater. But whatever it proves to be, to project a multi-metre SLR from it is simple fantasy.

[Karl]

We seem to be under some delusion that the Arctic sea ice is somehow not going to refreeze due to its record melt this year, odd it always seems to! Now, as to why the melt, well we could look at natural cycles powered by solar cycles which cause cycles of ocean heating which would lag some time behind and due to omplex ocean currents and mixing cause other cycles. Or we could, as many do, look at a trace gas that somehow is only causing warming at certain times and in certain places. Sorry, but all in all, AGW driven by CO2 is just not looking logical with the factual information we have, no matter what the models might want to say. Cries of panic and the end of the world might be fashionable in 2012 but it all seems to getting a bit too doomladen around here recently.

[Seke Rob]

How deep frozen is the GIS, or differently, what is the typical temperature profile from top to bottom in the present decade? Can find the historical reconstructions such as this http://courses.washington.edu/proxies/DahlJensenBoreholes.pdf suggesting where a rise is suggested in the range of 3C between 1983 and 1995.

[marktime]

Karl, I suspect you are trolling. If I am wrong, then I suggest you go to a forum such as RealClimate to look at the factual information on AGW which is freely available.

This forum is about Arctic Sea Ice and the thread is about models. Let us not get diverted into defending AGW.

[Lennartvdl]

"Scientists are either going to face up to adopting the precautionary principle and the need to promote the worst-case scenario (as every military strategist does as standard procedure) or they are liable to be more of a hindrance than a help as the mega-feedbacks take off.
If one starts from the premis that the purpose of science is the service of humanity, it could be argued that the failure to adopt the precautionary princple as the basis of prediction is essentially unscientific."

I fully agree. Besides Hansen's warning of the risk of multi-meter SLR even this century, the most extreme worst-case scenario I've seen so far is this recent article by Meehl et al:
http://www.nature.com/nclimate/journal/v2/n8/fig_tab/nclimate1529_F3.html

They show a risk with BAU of up to 12 meters of SLR around the year 2300, with almost 2 meters around 2100 and about 6 meters around 2200.

I've still no idea if Al Rodger's calculations are right. It would be nice to know Hansen's reply to those. I've asked him, but so far Hansen hasn't responded. Maybe if others would do the same we could ask him if we could post his reply here?

[Thereoncewasawindmill.wordpress.com]

Neven - your question of whether the models can catch up is actually about the mindset of the modellers. A simple extrapolation of observed ASI extent loss by 2000 would have given an incomparably more accurate forecast than the median of the AR4 projections - and that failure was the modellers' choice, not the available maths.

Putting orthodox theory before observation seems to me a pretty poor sort of science, and given the continuing kant about summer ice loss 'perhaps by 2030 to 2050', it would appear that doctrine is pretty impervious to blatant failure.

Lewis: I don't think that's fair. Not training the models on 20thC climate is a deliberate choice by the modellers, because if they were to train the models on 20thC climate, then the ability to use 20thC climate as a benchmark of the models would be lost.

To illustrate, a GCM could probably be persuaded to give earlier loss of sea ice by tweaking it to increase the ocean currents. However, if the real reason the model was failing was because of a different unmodelled feedback, by introducing a wrong correction you would have destroyed the ability of the data to detect and correct the error.

The approach of the modellers seems to me to be both rigorous and correct, and thus the data is able to do what it is supposed to - critique the models.

[Chris Biscan]

Everything Ive read says 360km3 = 1MM not 510km3.

At least in the "real world" that's what they say.

[Seke Rob]

My thinking is, that 510 million km^2 is the earths total surface and the oceans are ~360 million km^2. The answer would be Spock logically derived from that.

The simple google answer: http://wiki.answers.com/Q/What_is_the_surface_area_of_the_earth

[Lennartvdl]

360 Gt of ice = 360 km3 of water = 1 mm SLR, according to:
http://climatesanity.wordpress.com/conversion-factors-for-ice-and-water-mass-and-volume/

[wayne]

Sorry, no such thing as a "natural" cycle Karl, before stating such a claim do a preamble, a reference or anything which proves this case. Polar sea ice is a great metric, it has entire ecosystems adjusted to very thick ice spanning thousands and millions of years. All found in the mud at sea bottom, or by the split of bowhead species half Atlantic the other Pacific, to the ruins of paleo Inuit, all not indicating any "natural" cycle but a deep imprint of thick ice so wide and tough it stopped ships from penetrating the Northwest and Northeast passage in one season with any ease modern boats have now, it takes a few days without ice trials, no ice at all even! (documented from the 16th century until about 1998). Further back in time the Norse would have left their ruins all over the Arctic during the medieval warm period, being adventurous tough guys, thousands of years old ruins by the way are found here as if abandoned yesterday, the Romans would have invaded China or vice versa with the ease of wide open sailing. The cold strong multi year ice stopped all that, shaped human history by the climate it gives. So now give some evidence of a "cycle" with polar sea ice in mind. Or accept AGW as a mark seen from space of terra reforming by humans.

[JohnC]

The ice in Greenland doesn't have to melt to raise sea level it just has to get off Greenland.

[Karl]

@ Marktime, i'd suggest you are trying to close down rationale thought.
Models are mere predictions, fiction only until later facts show how well they relate to the real world. The only other place we have on Earth where sea ice melts and refreezes each year is the Antarctic. To ponder why the models are only working, and poorly at that, for the Northern hemisphere and not the Southern is something any rationale person might ponder on. Oh and your suggestion that I need to be 'educated' was insulting, but then you knew that. As for defending a theory, real science doesn't need to be defended, it needs to be proved, you may think AGW has, I do not.
Neven does a great job here, but as I've repeatedly said in the past, it is a great pity he allows the science to be coloured by certain folks politics at times, but then maybe the record melting ice has made these folk more courageous in their viewpoints. I don't post very often as I'm more interested in the data than peoples' views, but feeding frenzies as we've seen over the recent ice melt bother me for their lack of rationality.

[Jim Williams]

Al, he said mass loss, not melting. These are not the same.

I don't know how much ice is going to flow out of Greenland this century myself, but it will probably be more than that which melts in place.

Actually, how much ice leaves Greenland one way or another probably depends upon how much leaves the WAIS -- either through melt or movement. It'd think that a higher sea level would ease the ice transport out of Greenland quite a bit.

[Jim Williams]

Bfraser: "The volume of the Antarctic Ice Cap is ~25M km2 and the volume of the ocean is @1.3B km2. That's a ratio of over 40:1. Since the heat of fusion of ice is roughly 80cal/g, the average temperature of the ocean would need to be about 2C. Looking at this graph and noting that the average depth of the ocean is only 4000m, I'd say there's probably enough heat right there."

Given that your units for both numbers are area, not volume, I can't make sense of them.

However, I'm pretty sure the volume of the oceans is well over 40 times the volume of Antarctic ice (or total ice). If a large fraction of the ice, say a section of the WAIS, breaks up and begins floating it will melt before long. Of course, the damage will have (as others have noted) already been done.

As for how likely it is that a large section of the WAIS will collapse, didn't you hear the stampede of Glaciologists running back to their computers when the Larson B disintegrated?