Sea Level Rise Projections and Maps

[JimD]

Thanks to retiredBill I found the link to a global map that shows the effects of different amounts of sea level rise.

There is a global map on which you can set the sea level rise and zoom down to look at specific locations as well as individual maps of prominent cities and locations around the world.  Works just like Google maps.

Specific maps for Florida, New York, Venice, New Orleans, Washington, San Francisco, Nile Delta, Netherlands (it's sad Neven) as well as the global map.

http://geology.com/sea-level-rise/

[Anne]

It is worth reading Alex Tingle's caveats about his maps here. For example he says the source info isn't very accurate, and they don't take account of access to the sea, or of sea defences and erosion.

Bearing all that in mind, it's a thought-provoking resource.

[ccgwebmaster]

Bearing all that in mind, it's a thought-provoking resource.

One caveat I couldn't see at a glance - the effects of sea level rise from melting land ice vary widely depending on location due to the shifting mass on the planet. Sea level will actually fall near to the big ice sheets as mass is moving away from them - and rise proportionately more further away from them, if memory serves (and this can be a large effect).

In some locations the process is essentially potentially neutral so in those "sweet spots" you can add 10m on to global sea level and not see any significant change. Except in reality the different timings of contributions from different poles is likely to mean nowhere is ultimately unchanged in one direction or another at some point in time.

The specific details with respect to effects at a given location are rather important for planning purposes - if you expect X m of sea level rise (as a global average) by year Y - the implications for what would be needed to defend infrastructure or identify at risk areas are significant.

[Ned W]

Those maps have been around for a while.  They're not particularly reliable, but do convey the general idea.

They're based on elevation data from the Feb. 2000 Shuttle Radar Topography Mission, which used single-pass radar interferometry to map topography from 56S to 60N.  The resulting product is pretty coarse (spatial resolution 30m within the US, 90m elsewhere) and its vertical accuracy is not great.  In particular, the short wavelength used will tend to result in elevation measurements that are too high (biased upwards) in forested areas. 

Currently, Astrium is working on a much better global elevation data set (World DEM) derived from interferometry using the TerraSAR-X and TanDEM-X satellites.  When it's finished it will be a much better source for this kind of thing, at least in terms of spatial resolution.  I don't know how they're dealing with the problem of biases in forested areas, because TSX and TDX operate at an even shorter wavelength than SRTM did. 

If you really want to assess flood risk at a specific point, you need to look at a much higher resolution and higher accuracy source for topographic data, like airborne lidar.

[Ned W]

The blog post that Anne links to happens to include what surely must be a candidate for the all-time stupidest comment anywhere:

Hallo, this is a nice theorie, but the most ice is on the south pole. Greenland was in earlier time ice free! without any change on the sea level. you see, your theorie is bullshit.

That's right.  It turns out that conservation of mass is a CAGW alarmist lie.  You probably believed that if you took all the ice in Greenland and redistributed it across the world's ocean, sea level would have to rise.  But this anonymous blog scientist assures us that once before Greenland's ice just vanished. 

[Anne]

You'll find idiot comments all over the place, such as "no accident it's called Greenland", "natural cycles", "you don't need to be a climate scientist to see..." and "who was driving SUVs back in the Eemian?" I'm thinking of starting a collection of these idiocies.  Ned W, that one is a particular gem!

[ChrisReynolds]

It's not a map but people might want to read the latest RC post:
http://www.realclimate.org/index.php/archives/2013/08/the-inevitability-of-sea-level-rise/

Bottom line - about 2.3m SLR per degree of warming, long term - i.e. it takes time for ice sheets to respond, so don't get greedy and demand it all immediately.

[JimD]

Global Flood Damage Could Exceed $1 Trillion Annually by 2050

Interesting reading.  The report (authored by an economist at the World Bank) advocates building seawalls and such.  Note that they get their numbers assuming that sea level has only gone up .2-.4 meters by 2050. 

Just saw Chris's RC post.  Seems like our authors above ought to be advocating for moving those cities instead of trying to build defenses.

Flood damage in 136 of the world's largest coastal cities could soar to $1tn (£640bn) a year by 2050, because of climate change combined with rapid population increases, economic growth, and subsiding land, according to a study.

The report by Nature Climate Change says the cities at greatest risk, as measured by annual average flood losses, are Guangzhou (China), Miami (US), New York (US), New Orleans (US), Mumbai (India), Nagoya (Japan), Tampa-St Petersburg (US), Boston (US), Shenzen (China) and Osaka-Kobe (Japan).

Owing to their high wealth and low flood protection, Miami, New York and New Orleans comprise 31% of total losses. Adding Guangzhou, the four top cities account for 43% of global losses as of 2005, when the cost of worldwide flood damage was an estimated $6bn a year.

After all, Hallegatte says, even the cost of massive sea walls, natural barriers, and other coastal protection will seem like chump change compared to a scenario where "we have cities destroyed and we have to rebuild them again and again."

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1979.html (paywall)

http://www.theguardian.com/global-development/2013/aug/20/coastal-flood-damage-2050

http://www.motherjones.com/environment/2013/08/map-top-cities-billion-dollar-floods

[ritter]

Seems like our authors above ought to be advocating for moving those cities instead of trying to build defenses.

Where adaptation fails, migration will have to do. We've never been very good at out engineering nature. 

[Tor Bejnar]

Investtigation of Arctic Sea Level Rise
http://www.whoi.edu/science/PO/arcticsealevel/index.html
funded by National Science Foundation and NOAA

An included 2010 presentation is titled
"Arctic Ocean storm surges: origin, climatology, impacts, simulations and predictions".
The summary screen ^{_[reformated]}:

* Critical environmental, socioeconomic, and defense issues have focused the people’s attention on the coastal zone.

* This zone is particularly vulnerable in the Arctic, where unprecedented climate changes have already been observed in the context of high natural variability on a range of time scales.

* Key environmental issues affecting human activities on the Alaskan North Slope and Siberian coastal regions include:
     •   coastal erosion,
     •   recent decline in ice extent and thickness,
     •   less stable and predictable shore--‐fast ice, gouging of shelves and coast by sea ice, pile--‐up of ice on shore,
     •   rise in sea level, and storm hazards.

* One element of the observed climate change is the increased frequency and intensity of extreme events.

[TerryM]

While the costs involved in building a new New York further inland might seem extreme they probably pale when compared to the costs of building ever higher coastal defences. If things progress as rapidly as I fear we would have had to start the project at least a decade ago.
Insurance premiums may rise more rapidly than the sea and corporate head offices may migrate inland faster than the storm surges.
Would Detroit, with it's very low property values, access to plenty of fresh water and possibly an improving climate be seen as viable?
Terry

[JimD]

Terry

Asking New Yorkers to move to Detroit is almost as cruel as asking them to live in Cleveland!!

And here I was thinking Canadians were nice people.

It does make sense. But the HORROR, it might be better to go down with the ship.

[Chuck Yokota]

There are some interesting articles about the geographical variations in sea level rise from September 2012:

http://www.skepticalscience.com/Sea-Level-Isnt-Level-This-Elastic-Earth.html

http://www.skepticalscience.com/Sea-Level-Isnt-Level-Ocean-Siphoning-Levered-Continents-and-the-Holocene-Sea-Level-Highstand.html

[Shared Humanity]

While the costs involved in building a new New York further inland might seem extreme they probably pale when compared to the costs of building ever higher coastal defences. If things progress as rapidly as I fear we would have had to start the project at least a decade ago.
Insurance premiums may rise more rapidly than the sea and corporate head offices may migrate inland faster than the storm surges.
Would Detroit, with it's very low property values, access to plenty of fresh water and possibly an improving climate be seen as viable?
Terry

They won't move Manhattan. Concrete perimeter around the island with fill raising the island by about ten feet. You lay all of the underground mechanicals before the fill is put in and lose a couple of stories on each building.

[johnm33]

Short of a new topic this looks like the best place for this commentary on a soon to be released IPCC report. http://phys.org/news/2013-08-scientists-revive-climate.html#firstCmt

[JimD]

John

Good catch.  If you see the report when it comes out please post it.

[JimD]

I just edited the title of this topic to include "Projections" of sea level rise.  Wili and I had a series of posts on projection issues a few days ago in another topic and I thought we should have clear topics on things like sea level rise and temperature rises due to the interest in them.  So I thought modifying this topic would be appropriate.  I will look for new links on this issue and insert them.

[JimD]

Below is a Jun 2013 paper by Levermann et al (in the Proceedings of the National Academy of Sciences) on the multimillennial sea-level rise due to rising temperatures.

The study gives total projections and projections after 2000 years per degree C rise.  It does not address nearer timeframes, but rather the full rise, and the lower 2000 year rise (in other words it takes more than 2000 years to see the full rise), generated by temperature increases.  It is based on:

Here we combine paleo-evidence with simulations from physical models to estimate the future sea-level commitment on a multi- millennial time scale and compute associated regional sea-level patterns.

http://www.pnas.org/content/110/34/13745.full

See especially table 1 as it lists contributions from Greenland, Antarctica and Thermal Expansion and Glaciers - excerpt follows

Rise in M     after 2000yrs          Total Rise
                 Median  Range        Median Range
1 C            2.3       1.0-4.9        2.5     1.0-10.8
   
2 C            4.8        2.6-7.5       10.9    3.1-13.4

3 C            6.6        3.4-9.8       12.5    9.9-14.9

4 C            9.0        5.7-12.1      13.9   11.8-15.9

[JimD]

Below is a Jan 2007 paper by Rahmstorf in Science that makes projections on sea level rise for 2100.  Its primary finding is that for each 1 C rise in temp there will be a sea level rise of 3.4 mm per year.  It projects a sea level rise of up to 1.4 M by 2100.

I note that the paper also says this:

For this reason, our capability for calculating future sea-level changes in response to a given surface warming scenario with present physics-based models is very limited, and models are not able to fully reproduce the sea-level rise of recent decades.   Rates of sea-level rise calculated with climate and ice sheet models are generally lower than observed rates. Since 1990, observed sea level has followed the uppermost uncertainty limit of the Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (TAR), which was constructed by assuming the highest emission scenario combined with the highest climate sensitivity and adding an ad hoc amount of sea-level rise for “ice sheet uncertainty”

The author builds a semi-empirical model and runs hindcasts to check for model validity and then runs it to project future sea level rise.

We can explore the consequences of this semi-empirical relationship for future sea levels (Fig. 4), using the range of 21st century temperature scenarios of the IPCC (1) as input into Eq. 2. These scenarios, which span a range of temperature increase from 1.4° to 5.8°C between 1990 and 2100, lead to a best estimate of sea-level rise of 55 to 125 cm over this period. By including the statistical error of the fit shown in Fig. 2 (one SD), the range is extended from 50 to 140 cm

Although a full physical understanding of sea-level rise is lacking, the uncertainty in future sea-level rise is probably larger than previously estimated. A rise of over 1 m by 2100 for strong warming scenarios cannot be ruled out, because all that such a rise would require is that the linear relation of the rate of sea-level rise and temperature, which was found to be valid in the 20th century, remains valid in the 21st century. On the other hand, very low sea-level rise values as reported in the IPCC TAR now appear rather implausible in the light of the observational data.

http://www.sciencemag.org/content/315/5810/368.full

[JimD]

Here is a plain language version of the Levermann paper 2 posts up (by Levermann himself).

I note that Levermann says the current scientific literature puts an upper limit on sea level rise of 2m by 2100.

The long-term (2000 years) sea level rise potential is 2.3m per deg C rise.  And it goes up some more from there.

http://theconversation.com/the-inevitability-of-sea-level-rise-16871

[JimD]

Another really cool sea level rise map for the US (sorry I love maps).  The map is interactive and you can select states and cities and get a map for the specific city and change all kinds of settings as well.  Very neat!

http://www.climatecentral.org/news/sea-level-rise-locking-in-quickly-cities-threatened-16296

[Lennart van der Linde]

"Levermann says the current scientific literature puts an upper limit on sea level rise of 2m by 2100."

Yes, but a few scientists, such as Jim Hansen, but also Richard Alley, it seems, do not exclude a possibility of even more than 2m by 2100. Science does not seem to be able to exclude this possibility with high confidence yet, so it seems wise to take such a risk into account in discussions about potential future SLR.

[Lennart van der Linde]

Levermann et al speak about a SLR-committment of 2.3 m/degree C over 2000 years.

However, they explicitly take into account a risk of 3m/degree C over 2000 years, and even 4 m/degree C of total SLR-committment over more than 2000 years.

A global temperature rise of 4 degrees C over 2000 years, or even this century, will be very hard to prevent, since earth system sensitivity may be double the fast-feedback sensitivity, so even a 2 degrees rise this century could mean 4 degrees after 2000 years, according to Jim Hansen and others. And Anderson & Bows argue that in many mitigation scenarios even preventing 4 degrees this century has a less than 50% chance of succeeding, so this means we may be on course for up to 8 degrees of warming over 2000 years.

[JimD]

Lennart

Levermann et al speak about a SLR-committment of 2.3 m/degree C over 2000 years.

However, they explicitly take into account a risk of 3m/degree C over 2000 years, and even 4 m/degree C of total SLR-committment over more than 2000 years.

Yes,  from Fig 1 in the paper or my excerpt above:

For 2000 years and a 4C rise in temperature the range is 5.7-12.1m and total rise of 11.8-15.9m.  The range covers the typical uncertainty of the calculations.  Equal chance of the bottom number as the high number. 

Note that the paper DOES NOT indicate that the temperature rise from AGW will be limited to 4C.  The paper was just using the numbers 1-4 for running their model and validating it against past paleo data.  This I believe was just for convenience sake in order to limit the complexity of the work to be done.  If other researchers work comes to the conclusion that temperatures will rise 6 C, for example, one could extrapolate from this papers work or, better yet, rerun their model using 6C and recalculate new numbers.

I'm sure that if other researchers find this paper sound there will be other work leveraged from it and we will get new calculations in the next few years.

As not to many people are really focused on what happens in 2000 years but want to know what is going to happen soon (by 2100) we will need to find some other papers to insert as well.

Feel free to insert academic papers on this topic as you find them.  A lot of commentators and bloggers have come up with number via their own interpretations of what they read and hear, and those are interesting as well because it is instructive to follow their logic and also to see what concerns them the most.  But I always want to see the original work myself (I am not very trusting) as people have a tendency to exaggerate or change the intent of the original work.

[JimD]

Thanks to AbruptSLR and Lennart I found over in the Antarctic Folder another link to a paper on SLR by Goelzer et al Jul 2012

Millennial total sea-level commitments projected with the Earth system model of intermediate complexity LOVECLI

http://iopscience.iop.org/1748-9326/7/4/045401/article

The following is the projection from the abstract:

... In experiments with greenhouse gas concentration stabilization at 2100 AD, the total sea-level rise ranges between 2.1 m (B1), 4.1 m (A1B) and 6.8 m (A2). In all scenarios, more than half of this amount arises from the Greenland ice sheet, thermal expansion is the second largest contributor, and the contribution of glaciers and ice caps is small as it is limited by the available ice volume of maximally 25 cm of sea-level equivalent....

BIG NOTE:  This paper is projecting for the date year 3000 vice 4000 (or more) as in the Levermann paper.  It could be that the numbers from the 2 papers are in very close agreement.

They are using the IPCC scenarios and assuming greenhouse gas concentrations stabilize.  The approximate (I am eyeballing a chart) CO2 concentrations year 2100 for the scenarios are (B1) 530ppm, (A1B) 700ppm, (A2) 830ppm. 

Any more educated readers want to inform us on this a bit on these papers?  I note that the climate sensitivity used in the LOVECLIM is much lower than what seems to be the consensus sensitivity numbers used elsewhere (but maybe this makes sense in what they are doing for some reason).  The paper also states (I think) that for the 1000 year timeframe of this study that Greenland dominates in terms of ice sheet melting over Antarctica and that a little more than 50% of  Greenland will be melted by then (this is the A2 scenario and +6C temperature rise).

[Lennart van der Linde]

Jim,

You're right that for every worst-case scenario there's also a best-case scenario. From a precautionary perspective I think scientifically based worst-case scenarios should be leading in deciding about policies, so that's why I think we should stress those worst-case scenarios, while hoping the best-case scenarios, or even the most likely scenarios, will turn out to be more/most accurate.

Goelzer et al 2012 I find interesting because it seems they find a worst-case scenario of about 25 meters of SLR by the year 3000, if I interpret their figure 7 correctly.

I will soon post some other SLR-articles I find interesting.

[JimD]

Here is a Vermeer and Ramstorf paper (published in PNAS) from 2009 that projects sea level for a number of IPCC scenarios.  It is interesting to compare this with the other Ramstorf paper above from 2007.  Using different methodology slightly higher numbers are projected in this paper (approx. 0.5m higher) 75 to 190 cm.

Global sea level linked to global temperature
Martin Vermeera,1 and Stefan Rahmstorfb
aDepartment of Surveying, Helsinki University of Technology, P.O. Box 1200, FI-02150, Espoo, Finland; and bPotsdam Institute for Climate Impact Research, Telegrafenberg A62, 14473 Potsdam, Germany
Edited by William C. Clark, Harvard University, Cambridge, MA, and approved October 26, 2009 (received for review July 15, 2009 

http://www.pnas.org/content/106/51/21527.full

Abstract

We propose a simple relationship linking global sea-level variations on time scales of decades to centuries to global mean temperature. This relationship is tested on synthetic data from a global climate model for the past millennium and the next century. When applied to observed data of sea level and temperature for 1880–2000, and taking into account known anthropogenic hydrologic contributions to sea level, the correlation is >0.99, explaining 98% of the variance. For future global temperature scenarios of the Intergovernmental Panel on Climate Change's Fourth Assessment Report, the relationship projects a sea-level rise ranging from 75 to 190 cm for the period 1990–2100.

[JimD]

Here is a very interesting paper that was referenced in the 2009 Ramstorf paper.

Pheffer et al Sep 2008 Science
Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise

http://www.sciencemag.org/content/321/5894/1340.full?sid=4f90482f-93da-43bf-b786-7200292dc236

This paper is a very interesting read (and a relatively easy one as there is basically no math in it).  The basic conclusion of the paper is that sea level rises above 2 M by 2100 are not physically tenable.  Greenland due to its geology is amenable to calculating with some certainty its possible slr contributions but Antarctica is not for the same reason.  The paper assumes East Antarctica just will not have significant changes by 2100 so it will not contribute much to slr while in the west the authors make their calculation (if I understand it correctly) assuming high end observed processes (glacier speeds and such).  For Antarctica to change the 2 M number (it is impossible for Greenland to do this) there would have to be a significant and large change in the dynamics of the melt down there.  Maybe AbruptSLR could jump in and respond to this paper as I am sure he has read it and he is very technically astute.

Abstract

On the basis of climate modeling and analogies with past conditions, the potential for multimeter increases in sea level by the end of the 21st century has been proposed. We consider glaciological conditions required for large sea-level rise to occur by 2100 and conclude that increases in excess of 2 meters are physically untenable. We find that a total sea-level rise of about 2 meters by 2100 could occur under physically possible glaciological conditions but only if all variables are quickly accelerated to extremely high limits. More plausible but still accelerated conditions lead to total sea-level rise by 2100 of about 0.8 meter. These roughly constrained scenarios provide a “most likely” starting point for refinements in sea-level forecasts that include ice flow dynamics.

[Laurent]

Watching Antartic melting last winter (Northen), I can tell you, it started to melt, not a lot but yes it did. I am not speaking of Ronne ice shelve and Filchner Ice shelve wich did melt a lot but of amery ice shelve. Abruptslr  will tell us more... !

[Lennart van der Linde]

Hansen & Sato 2011 (draft version that was published unchanged in 2012) on pp.22-23 give the following comment on Pfeffer et al 2008:
http://arxiv.org/ftp/arxiv/papers/1105/1105.0968.pdf

“The kinematic constraint may have relevance to the Greenland ice sheet, although the assumptions of Pfeffer at al. (2008) are questionable even for Greenland. They assume that ice streams this century will disgorge ice no faster than the fastest rate observed in recent decades. That assumption is dubious, given the huge climate change that will occur under BAU scenarios, which have a positive (warming) climate forcing that is increasing at a rate dwarfing any known natural forcing. BAU scenarios lead to CO2 levels higher than any since 32 My ago, when Antarctica glaciated. By mid-century most of Greenland would be experiencing summer melting in a longer melt season. Also some Greenland ice stream outlets are in valleys with bedrock below sea level. As the terminus of an ice stream retreats inland, glacier sidewalls can collapse, creating a wider pathway for disgorging ice.

The main flaw with the kinematic constraint concept is the geology of Antarctica, where large portions of the ice sheet are buttressed by ice shelves that are unlikely to survive BAU climate scenarios. West Antarctica's Pine Island Glacier (PIG) illustrates nonlinear processes already coming into play. The floating ice shelf at PIG's terminus has been thinning in the past two decades as the ocean around Antarctica warms (Shepherd et al., 2004; Jenkins et al., 2010). Thus the grounding line of the glacier has moved inland by 30 km into deeper water, allowing potentially unstable ice sheet retreat. PIG's rate of mass loss has accelerated almost continuously for the past decade (Wingham et al., 2009) and may account for about half of the mass loss of the West Antarctic ice sheet, which is of the order of 100 km3 per year (Sasgen et al., 2010).

PIG and neighboring glaciers in the Amundsen Sea sector of West Antarctica, which are also accelerating, contain enough ice to contribute 1-2 m to sea level. Most of the West Antarctic ice sheet, with at least 5 m of sea level, and about a third of the East Antarctic ice sheet, with another 15-20 m of sea level, are grounded below sea level. This more vulnerable ice may have been the source of the 25 ± 10 m sea level rise of the Pliocene (Dowsett et al., 1990, 1994). If human-made global warming reaches Pliocene levels this century, as expected under BAU scenarios, these greater volumes of ice will surely begin to contribute to sea level change. Indeed, satellite gravity and radar interferometry data reveal that the Totten Glacier of East Antarctica, which fronts a large ice mass grounded below sea level, is already beginning to lose mass (Rignot et al., 2008).”

My conclusion from Hansen and Sato is that it may be too early to say with high confidence that more than 2m of SLR by 2100 is not possible.

[Lennart van der Linde]

Another interesting paper is Foster & Rohling 2013 in PNAS:
http://www.pnas.org/content/early/2013/01/03/1216073110.full.pdf+html

They conclude:
"Given the present-day (AD 2011) atmospheric CO2 concentration of 392 ppm, we estimate that the long-term sea level will reach +24 +7/−15 m (at 68% confidence) relative to the present. This estimate is an order of magnitude larger than current projections for the end of this century [up to 2 m; best estimate, 0.8 m (Pfeffer et al. 2008)] and seems closer to the worst-case long-term sea level projection portrayed by Meehl et al. (2012). Using terminology of the Intergovernmental Panel on Climate Change Fourth Assessment Report IPCC AR4, we find it very likely (i.e., at 90% confidence) that long-term sea-level rise for sustained present-day CO2 forcing will be >6 m, and likely (68% confidence) that it will be >9 m. Through analogy with the geological record, this rise likely will be achieved through melting of the GrIS and WAIS and possibly some portion of the EAIS (if sea level were to rise >14 m). However, it will take many centuries to get to these high levels. Given the typical mean rates of natural sea-level rises on multicentury timescales [1.0–1.5 cm·yr−1, with extremes during deglaciation of 5 cm·yr−1], our projection suggests an expected equilibration time of the Earth system to modern CO2 forcing of 5–25 centuries."

So they think the current CO2-concentration of almost 400 ppm will eventually, in about 5-25 centuries, lead with 68% likelihood to a SLR of 9-31m, with a best estimate of about 24m, and with 84% likelihood of at least 9m of eventual SLR (their 68% in this case is not 'carefully worded', as Rohling has confirmed by email).

Even for 350 ppm they find a 84% chance of at least 7m of SLR in the longer term, with a best estimate of about 16m, and 16% chance of more than 21m (according to supporting information file Dataset S2, linked at the end of the supplementary information).

[Lennart van der Linde]

Meehl et al 2012 (Nature Climate Change), to which Foster & Rohling 2013 refer, contains this interesting figure:
http://www.nature.com/nclimate/journal/v2/n8/fig_tab/nclimate1529_F3.html

This seems to imply a worst-case scenario of almost 6m of SLR by 2200 and about 10-12m by 2300.

[JimD]

My conclusion from Hansen and Sato is that it may be too early to say with high confidence that more than 2m of SLR by 2100 is not possible.

I don't think anyone is saying that other than that is the conclusion of the Pheffer paper.  While Hansen does not seem to like the paper, Ramstorf seems to have the opposite opinion.  But a good find and interesting comments.

One thing I find disappointing about the Hansen paper is that, in some ways, it seems to misrepresent the Pheffer paper or ignore the contents of the paper.  Pheffer went to some trouble to show why the topography of Greenland significantly restricts the flow of ice into the sea and calculates how much higher the rate of ice movement and melt would have to be to result in large contributions to sea level rise and concludes that it is not possible.  This seems to take into account Hansen's argument.  I would have preferred him to state why Pheffers calculations and conclusions are wrong rather than just to say the melt is going to rapidly accelerate and this  will overcome the geology.

...The present-day average velocity of all Greenland outlet glaciers is 0.56 km/year when weighted by drainage basin area or 1.23 km/year when weighted by gate cross-sectional area. The two weighted averages are different because gate cross-sectional area does not scale with drainage basin area. Average (present day to 2100) outlet glacier speeds required to meet 2- and 5-m SLR targets range from 26.8 km/year to 125 km/year, depending on the scenario considered [table 2 and supporting online material (SOM)]. These velocities must be achieved immediately on all outlets considered and held at that level until 2100. Delays in the onset of rapid motion increase the required velocity further (fig. S1)...
....A comparison of calculated (Table 2) and observed (1.23 km/year) average velocities shows that calculated values for a 2-m SLR exceed observations by a factor of 22 when considering all gates and inflated SMB and by a factor of 40 for the marine gates without inflated SMB, which we consider to be the more likely scenario. With the exception of discharge through all gates at inflated SMB (26.8 km/year), none of the velocity magnitudes shown in Table 2 has ever been observed anywhere, even over short time periods....

The Pheffer paper seems to assume (or maybe it said it) that the Eastern Antarctic will not make any significant contributions to sea level rise this century (which I seem to have read in other places as well).  The Paper indicates that over 90% of the Antarctic contribution to slr will come from PIGS/Thwaites and Lambert/Amery.  Once again the Pheffer paper seems to anticipate the Hansen papers arguments for Antarctic melt and after reading the Hansen comments several times Hansen does not exactly refute the Pheffer papers timeline.  He just seems to state that there will eventually be a very large melt from the West side.  The Pheffer paper says this about this area:
 

Most of the marine-based ice in West Antarctica is held behind the Ross and Filchner-Ronne ice shelves, which we consider unlikely to be removed by climate or oceanographic processes within the next century [e.g., (19)]. The Amundson Coast basin [including Pine Island Glacier (PIG) and Thwaites Glacier], however, is not confined by large ice shelves and contains about 1.5 m sea level equivalent (5.43 × 105 Gt) (20). The aggregate cross-sectional gate area of PIG and Thwaites Glacier is ca. 120 km2 (20). The average velocity in this region is 2 km/year (table S2), higher than the average velocity of all Antarctic ice streams [0.65 km/year (19)]. An average (present day to 2100) velocity of 53.6 km/year is required to discharge 1.5 m sea-level equivalent through the PIG and Thwaites glacier gates by 2100, again far greater than any observed glacier velocity. ...

Anyway, this is interesting and I am learning a lot.

[Lennart van der Linde]

What I forgot to note in my last post: even the strongest mitigation scenario of Meehl et al 2012 seems to contain a risk of more than 1m of SLR by 2100 and more than 3m by 2300.

[JimD]

Meehl et al 2012 (Nature Climate Change), to which Foster & Rohling 2013 refer, contains this interesting figure:
http://www.nature.com/nclimate/journal/v2/n8/fig_tab/nclimate1529_F3.html

This seems to imply a worst-case scenario of almost 6m of SLR by 2200 and about 10-12m by 2300.

I tried to find a non-paywalled copy of this paper and could not unfortunately.  If anyone finds one please post it. 

I notice on the graphs from the paper you linked to that it is in pretty close agreement with the Pheffer paper.  It seems that Ramsdorf, Pheffer, Levermann and Meehl and their co-authors are in, at least, broad agreement given their different approaches.

[Lennart van der Linde]

Jim, good points about Pfeffer et al and Hansen & Sato. I've looked at those before, but am not yet entirely convinced. I have to run now, but will come back and see if I can explain why Hansen & Sato may still have a point about Pfeffer et al, although I agree it needs more careful and elaborate work to be able to be really convincing.

[Lennart van der Linde]

Jim,

You can find a lot of relevant discussion and papers on the risks of SLR in this thread (and also others) in the Antarctic folder, where AbruptSLR has done, and still is doing, a great job in pointing out reasons why Pfeffer et al 2008 may still be underestimating those risks:
http://forum.arctic-sea-ice.net/index.php?topic=31.0

See for example this comment I made there:

"Pfeffer et al (2008) estimate a max possible rise of about 2 meters by 2100:
http://www.sciencemag.org/content/321/5894/1340.full.pdf

That would imply a rate of SLR by about 2100 of probably circa 4 cm/yr, so if sustained about 4 m/century. The question is if this would be their estimated max potential rate of SLR, or if it could go even faster later in the next century.

Hansen and Sato (2012) seem to expect an 'iceberg cooling' negative feedback which would keep the max rate of SLR under about 5-6 meters/century (under BAU emissions). They criticize Pfeffer et al for (mainly) not sufficiently taking the instablity of WAIS into account.

Pfeffer et al assume an average outlet glacier velocity for PIG/Thwaites of about 14-15 km/yr from 2020-2100. How fast could we reach that speed and how much faster could those glaciers go?

And how about the assumption of Pfeffer et al for Greenland of an average outlet glacier velocity of about 27 km/yr from 2020-2100? How likely is that and how much faster could it go, if at all?"

Also Pfeffer et al did not consider a possible contribution from Totten Glacier in the EAIS, if I'm not mistaken.

And they assume a sudden speed-up of all outlet glaciers until 2020 with constant speed from then on. But could this acceleration not continue for several more decades?

About the possible 'iceberg cooling effect' that Hansen & Sato point out: they speak of a model run of 60 cm of SLR by 2065 and 1.4m by 2080, so assuming constant speed from then on this would imply almost 2.5m by 2100, about 8m by 2200 and about 13.5m by 2300 as a worst-case scenario.

This would be only a little more extreme than Pfeffer et al and Meehl et al. whose worst-case scenarios would reach these same levels only a few decades later. This would seem to make little difference for potential mitigation and adaptation policy implications in the current decade and the rest of this century.

[JimD]

I found an interesting letter in PNAS by Strauss Jul  2013 that comments on the Levermann paper.

One item especially caught my attention.  Great numbers for use in promoting awareness of our problems.  The total melting potential of burning a ton of coal or a liter of petroleum.

One more set of implications from Levermann et al. is worth visiting here. Simple calculations integrating TCRE indicate that emitting 1 metric ton of carbon may increase ocean volume by 1,092 m3 (588– 1680 m3) in the long run. Similarly, combusting 1 ton of coal ultimately adds 621 m3 (334–955 m3) to the ocean, and a single liter of petroleum adds 647 times its volume (348– 996 L), assuming mean fuel carbon densities from current US consumption (16).

http://www.climatecentral.org/wgts/filetracker.php?file2dl=Strauss-PNAS-2013.pdf

[JimD]

Lennart

BTW I am just having fun here looking through the papers and trying to figure out what they say.  I have no position on what the right answer is.  I am playing devil's advocate is all and not picking any fights.

And how about the assumption of Pfeffer et al for Greenland of an average outlet glacier velocity of about 27 km/yr from 2020-2100? How likely is that and how much faster could it go, if at all?"

I think you misunderstood this paragraph from the paper.

The present-day average velocity of all Greenland outlet glaciers is 0.56 km/year when weighted by drainage basin area or 1.23 km/year when weighted by gate cross-sectional area. The two weighted averages are different because gate cross-sectional area does not scale with drainage basin area. Average (present day to 2100) outlet glacier speeds required to meet 2- and 5-m SLR targets range from 26.8 km/year to 125 km/year, depending on the scenario considered [table 2 and supporting online material (SOM)]. These velocities must be achieved immediately on all outlets considered and held at that level until 2100. Delays in the onset of rapid motion increase the required velocity further (fig. S1).

Current weighted speed is only 1.23 km/yr and the speed needed to hit a 2m slr is 26.8 km/yr.  And that 26.8 km/yr would have to be achieved immediately and held at that speed until 2100.  Any delays in getting to this speed immediately require even higher velocities.  I surely do not know how likely it is that we will hit the 26.8 nor if higher speeds are possible (we would have to find it in some other paper), but I absolutely know that we will not be hitting the 26.8 km/yr speed for many years yet.  The melt just does not have enough heat driving it yet and will not for some time.  So, if we accept their numbers it means that the velocity needed will be well in excess of the 26.8 km/yr.  Greenland seems to be constrained.

Also Pfeffer et al did not consider a possible contribution from Totten Glacier in the EAIS, if I'm not mistaken.

I think this is correct as Totten is not specifically mentioned.  In the chart on Antarctic contributions to slr it does not look like the East Antarctic is listed, but I may just be misinterpreting it also.

Pfeffer et al assume an average outlet glacier velocity for PIG/Thwaites of about 14-15 km/yr from 2020-2100. How fast could we reach that speed and how much faster could those glaciers go?

Well that is the question all right and the answer seems to hang on it.  The paper says this

The average velocity in this region is 2 km/year (table S2), higher than the average velocity of all Antarctic ice streams [0.65 km/year (19)]. An average (present day to 2100) velocity of 53.6 km/year is required to discharge 1.5 m sea-level equivalent through the PIG and Thwaites glacier gates by 2100, again far greater than any observed glacier velocity

which indicates that the current PIGS/Thwaites velocity is 2 km/yr and then the paper calculates its 2m by 2100 limit based upon an increase in PIGS/Thwaites velocity of 7 times.  A big increase so they are assuming it speeds up a lot.  And it has to hit that velocity within 10 years and then hold.  Is this assumption still too conservative?  I have no idea but they do seem to be fully accepting that all melt rates are going to increase significantly.  To fully dump PIGS/Thwaite would require an immediate speed up of 26 times the current velocity that held till 2100.  Close to a collapse?  One of our Black Swans perhaps?

And they assume a sudden speed-up of all outlet glaciers until 2020 with constant speed from then on. But could this acceleration not continue for several more decades?

I may be exceeding my pay grade here, but I think the answer to that question is no for Greenland and for the Antarctic maybe.  The outlet glaciers do not have an unlimited amount of ice to dump into the ocean.  As time goes on they will have dumped a large percentage of the total volume of ice available to them and the rate of new ice creation will eventually come to a halt due to the warming.  Greenland is constrained due to it being shaped like a bowl.  As the depth of the ice cap shrinks it has less force to exert, less volume to dump and, importantly, less height advantage.  Antarctica obviously is shaped more traditionally and also has a lot more volume to dump.  How fast it could go, how soon it could get up to speed and how long it could last?  Good question.  I expect that if there are any significant flaws in the paper or omissions it will be in relation to Antarctica.  But, excepting the unexpected collapse (to everyone but AbruptSLR) it would seem unlikely that we will get an acceleration there for many years yet, so this paper might be pretty on the mark?  Maybe??
   
There is a supplemental table to the paper (separate pdf download) which details all the main discharging glaciers in Greenland that might help understand how detailed this paper was in those calculations.

[Lennart van der Linde]

I'm still wondering how Levermann et al compares to Foster & Rohling. F&R think that 400 ppm is enough to raise sea level by about 10-30m in the long run. Let's assume 400 ppm implies about 2-4 degrees C of warming in the long run. So F&R's estimate then suggests about 2.5-15m of SLR per degree of warming in the long run, a much wider range than the circa 3-4m per degree of Levermann et al (for 4 degrees of warming).

So do Levermann et al under-estimate potential SLR for the long run? Or do Foster & Rohling over-estimate this potential long-run SLR?

[TerryM]

Probably a very stupid question but is it possible that the ice/ocean interface will move sufficiently far inland that the only thing passing through the narrow cracks in the bowl's edge will be meltwater?
If glacial retreat exceeds glacial advance this would at some point seem an inevitability but I don't know if there are examples of this kind of activity re. ice sheets. Mountain glaciers are in retreat everywhere you look & if the same process took place with ice sheets in Greenland wouldn't this throw out all the papers that are based on glaciers entanglements in the narrow fjords that snake their way through coastal mountains?
Terry

[Lennart van der Linde]

Jim,

I greatly appreciate your detailed comments on Pfeffer et al. Here's another link to their paper, since the other links may not work:
http://www3.geosc.psu.edu/~jfk4/Geosci_500/Discussion%20papers/Last%20week%202/Science%202008%20Pfeffer.pdf

They may very well be right, but I'm also playing a kind of devil's advocate, since we want to have very high confidence in their conclusions in order to not be (even more) unpleasantly surprised later on.

So let's consider these quotes from their paper:

"[T]he near-doubling of ice discharge from Jakobshavn Glacier in 2004–2005 was associated with an acceleration to 12.6 km/year (7). Similarly, a temporary 80% increase in the speed near the terminus of Kangerdlugssuaq produced a velocity of 14.6 km/year (6). A comparison of calculated (Table 2) and observed (1.23 km/year) average velocities shows that calculated values for a 2-m SLR exceed observations by a factor of 22 when considering all gates and inflated SMB and by a factor of 40 for the marine gates without inflated SMB, which we consider to be the more likely scenario. With the exception of discharge through all gates at inflated SMB (26.8 km/year), none of the velocity magnitudes shown in Table 2 has ever been observed anywhere, even over short time periods.
The highest observed velocities have occurred at surging glaciers, including circa (ca.) 70 m/day (25.5 km/year) at Variegated Glacier (17) and 105 m/day (38.3 km/year) at Medvezhiy Glacier (18), but were held only for brief periods (hours to days). Although no physical proof is offered that the velocities given in Table 2 cannot be reached or maintained over century time scales, such behavior lies far beyond the range of observations and at the least should not be adopted as a central working hypothesis."

"Greenland SMB was accelerated at present-day rates of change, but dynamic discharge was calculated by accelerating outlet glacier velocities by an order of magnitude in the first decade. In Antarctica, PIG/Thwaites was accelerated from present-day net discharge (19) in the first decade and held thereafter to the highest outlet glacier velocity observed anywhere [14.6 km/year (6)], and Lambert/Amery was accelerated from present-day net discharge (19) in the first decade by an order of magnitude and held thereafter."

"Most of the marine-based ice in West Antarctica is held behind the Ross and Filchner-Ronne ice shelves, which we consider unlikely to be removed by climate or oceanographic processes within the next century [e.g., (19)]."

Fair enough, that it seems I confused their 27 km/yr average speed from 2008-2100 for 2m SLR by GIS alone with their circa 12 km/yr average speed over 2020-2100 for the GIS-contribution to a total 2m SLR by 2100. So the first seems indeed very unlikely, but the second maybe not completely, since such velocities have already been observed in a few locations/short periods and it seems the melting has just begun and has speeded up quite a bit over the past decade?

Moreover, GIS may be more vulnerable than thought at Jakobshavn and Petermann Glaciers, since at these glaciers the glacier beds extend inland hundreds of kilometers below sea level into the interior, as Hansen & Sato also seem to indicate?

Pfeffer et al do consider a contribution from Amery/Lambert in the EAIS, but a much larger part of EAIS may be vulnerable to relatively mild warming, according to recent research on the Pliocene (I don't have the reference at hand now, but it will be in the Antarctic thread for sure).

The great ice shelves RIS and FRIS may also be more vulnerable than thought, but I will have to check what papers AbruptSLR has found on those.

To what extent negative and positive melting feedbacks will balance each other out or not seems to still be an open question as well.

Pfeffer himself has given a nice overview in 2011 of the state of the science on land ice and sea level rise:
http://www.tos.org/oceanography/archive/24-2_pfeffer.pdf

He says:

'[M]uch of the focus of the glaciological research community has been on the dynamics of marine-based ice—that is, on the possibility of “rapid dynamic changes” that would transfer ice quickly from land to ocean and raise sea level far faster than by melt alone. Such events appear in the PDF as a “Fat Tail”: events of high consequence, and low but not a vanishing probability, hence, the “fat” tail of the distribution. Such events are both spectacular and important, but they are not the entire story, nor are
they the entire PDF.'

So my conclusion so far is: 2m of SLR by 2100 seems quite unlikely, but we cannot at this moment exclude such a risk, and there might even be a reasonable argument in the making for a risk of still faster SLR.

[Lennart van der Linde]

Terry,

I've been wondering the same, but have found no answer yet. I suspect/fear however that Arctic amplification will have some big unpleasant suprises in store for us when GIS, WAIS and EAIS start to melt/disintegrate seriously later this century.

[Lennart van der Linde]

Expert elicitation seems to be an important way of getting more insight into the potential risk of WAIS-collapse. Bamber & Aspinall (2013) gave some useful data from their survey amongst 13 experts (out of 26 invited) in 2010 and 2012:
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1778.html

In their supplementary Table S1 (p.8 last column) they apparently show that the rate of SLR in 2100 from the ice sheets is estimated on average to be 5-7 mm/yr, with a 5% risk of more than circa 17 mm/yr, and a very small chance of almost 4 cm/yr in the most extreme scenario. That last scenario would seem to be about the same as the most extreme scenario by Pfeffer et al. On p.10 (bottom) of the supplementary info they also seem to give an even more extreme estimate for the max rate of (total) SLR in 2100 of almost 5 cm/yr, but I don't understand the technical details of these different estimates.

The 13 experts surveyed were (p.11 supplementary info):
Richard Alley, Richard Hindmarsh, Philippe Huybrechts, Ian Joughin, Shawn Marshall, Frank Pattyn, Jeff Ridley, Eric Rignot, Catherine Ritz, Robert Thomas, Michiel van den Broeke, Roderik van de Wal, David Vaughan.

[JimD]

Lennart

In an attempt to shed some light on this question.

So do Levermann et al under-estimate potential SLR for the long run? Or do Foster & Rohling over-estimate this potential long-run SLR?

I found two articles on RealClimate on this very question of process based, empirical based and paleo based sea level projections by Ramsdorf.  Pretty convenient.  I am still trying to process the articles and all the comments.  Let me know what you think.

Part 1
http://www.realclimate.org/index.php/archives/2013/01/sea-level-rise-where-we-stand-at-the-start-of-2013/

Part 2
http://www.realclimate.org/index.php/archives/2013/01/sea-level-rise-where-we-stand-at-the-start-of-2013-part-2/

[AbruptSLR]

All,

I have found the discussion in this thread enjoyable.  Unfortunately, I do not have time now to properly entering into the discussion about Pfeffer et al 2008/2011; so I will provide the following link to so of my prior comments on this topic (of Pfeffer et al), and I would like to draw particular attention to my reply #19 in that thread that indicates that all of the researchers cited after the link will be holding a seminar (September 9-12, 2013) to consider whether there is justification to increase SLR projections beyond that considered essentially by Pfeffer et al (ie over 7-ft or 2.1 m by 2100).  Thus I am not the only person concerned with this possibility:

http://forum.arctic-sea-ice.net/index.php/topic,70.0.html


Louise C. Biddle - University of East Anglia; Carmen Boening – JPL; Knut Christianson - New York University; Ian Fenty – JPL; Ichiro Fukumori – JPL; Karen J. Heywood - University of East Anglia; David M. Holland - New York University; Chia-Wei Hsu - University of California, Irvine; Erik R. Ivins – JPL; Ian R. Joughin - University of Washington; Ala Khazendar – JPL; Ron Kwok – JPL; Felix W. Landerer – JPL; Eric Yves Larour – JPL; Brent M. Minchew – Caltech; Sophie MJ Nowicki - NASA GSFC; Antony J. Payne - University of Bristol; Eric Rignot - University of California, Irvine; Mirko Scheinert - Dresden University of Technology; Michael Schodlok – UCLA; Mark Simons – Caltech; Andrew L. Stewart – Caltech; Andrew F. Thompson – Caltech; Isabella Velicogna - University of California Irvine; Anna K. Wahlin - University of Gothenburg; Michael M. Watkins – JPL; Benjamin G. Webber - University of East Anglia; Josh Willis - JPL

Furthermore, I would like to make a very few quick comments about Pfeffer et al's case:
(1) Their values for current ice mass loss from the WAIS need to be increased by about 25% due to Glacial Isostatic Adjustment, GIA, corrections to match recent GPS field measurement (and if one were to follow their logic this would increase the 2100 SLR contribution from the WAIS also by 25%).
(2) They do not realize that substantial amount of ice mass loss from the AIS currently occurs due to the outflow of basal melt water, see the attached table from:

Citation: Death, R., Wadham, J. L., Monteiro, F., Le Brocq, A. M., Tranter, M., Ridgwell, A., Dutkiewicz, S., and Raiswell, R.: Antarctic Ice Sheet fertilises the Southern Ocean, Biogeosciences Discuss., 10, 12551-12570, doi:10.5194/bgd-10-12551-2013, 2013.

http://www.biogeosciences-discuss.net/10/12551/2013/bgd-10-12551-2013.pdf

http://www.biogeosciences-discuss.net/10/12551/2013/bgd-10-12551-2013-supplement.pdf

(3) They seem to ignore the fact that as the WAIS is the last remaining marine ice sheet, most of the ice mass loss after 2040 will likely occur by the float-out of icebergs and bergy bits that have calved-off of the unstable faces of several ice streams that have retreated behind the gateways cited by Pfeffer et al.

When, I have more time I will post more arguments for why Pfeffer et al 2008/2011 may be non-conservative, from a public safety point of view (or if you have the energy you could look though the many threads in the Antarctic folder).

Best,
ASLR

[AbruptSLR]

I only have time to make short replies for a while about why an upper SLR limit by 2100 beyond Pfeffer et al's 2m value should be considered:

Regarding my prior comment that possibly after 2040 bergy bits (particularly from Thwaites, Smith and Pine Island, Glaciers) may calve-off and float away faster than Pfeffer et al considered, see particularly my replies #13 and 46 at the following thread link:

http://forum.arctic-sea-ice.net/index.php/topic,72.0.html

Also from the following reference, I present the following quote citing the "ephemeral" nature of the stability of the Thwaites Glacier if circulating waters substantially reduce the basal resistance in the gateway area:

Dynamic (in)stability of Thwaites Glacier, West Antarctica,
by B. R. Parizek, K. Christianson, S. Anandakrishnan, R. B. Alley, R. T. Walker, R. A. Edwards, D. S. Wolfe, G. T. Bertini, S. K. Rinehart, R. A. Bindschadler, S. M. J. Nowicki, Article first published online: 16 MAY 2013, DOI: 10.1002/jgrf.20044;  Journal of Geophysical Research

"In addition to the SeaRISE data sets, we use detailed aerogeophysical and satellite data from Thwaites Glacier as input to a coupled ice stream/ice-shelf/ocean-plume model that includes oceanic influences across a several kilometers wide grounding zone suggested by new, high-resolution data. Our results indicate that the ice tongue provides limited stability, and that while future atmospheric warming will likely add mass to the surface of the glacier, strong ice stream stabilization on bedrock highs narrower than the length of the grounding zone may be ephemeral if circulating waters substantially reduce basal resistance and enhance melting beneath grounded ice within this zone."

[Lennart van der Linde]

Jim and ASLR,

Thanks for the great contributions. I think the overview on RealClimate by Rahmstorf is very useful and to the point. In the comments there someone posted this video of a lecture by Richard Alley:


The last four minutes of this lecture I find particulary interesting, where Alley says we can't rule out an abrupt SLR by a collapse of the WAIS of maybe up to 3m in about a century. This may not happen at all, or not for centuries, but we unfortunately cannot be sure that such a collapse will not start within this century.

Also Rahmstorf adds in the comment section (inline response to comment #19):
"Semi-empirical models have been criticised for potentially underestimating non-linear ice-sheet responses, like what Richard Alley talks about in his lecture. I think there are some arguments why these models might underestimate and some why they might overestimate future sea-level rise, but ultimately we do not know."

So, in addition to earlier comments here and to ASLR's pointer to the very interesting workshop next week, I think Alley and Rahmstorf give reasonable arguments for taking Pfeffer's risk of about 2m of SLR by 2100, or maybe even some more, seriously into account at this point in the scientific discussion.

[Lennart van der Linde]

This paper by Rahmstorf and colleagues, Schaeffer et al (2012), I find also very interesting:
http://www.climateanalytics.org/sites/default/files/attachments/publications/Schaeffer%20et%20al%20%282012%29%20Long-term%20SLR.pdf

From their table 1 it seems possible to conclude that even in their CPH reference scenario, which is not a worst-case yet, a risk of about 1.4m of SLR in 2100 and about 4m by 2200 seems possible. So it seems likely that their worst-case scenario will look about the same as that of Meehl et al, mentioned above. And just as in Meehl et al, Schaeffer et al show a risk of about 1m of SLR even in scenarios that have a more than 50% chance of staying below 2 degrees C of warming.

[AbruptSLR]

Lempert et al. 2012 provide the Beta PDF for Pfeffer et al 2008's SLR projections, shown in the attached image; which also provides a rough comparison with both the low and high SLR ranges for Pfefer et al 2008 and for Rohling et al 2007 and also the average low (0.6m) and the average high (1.25m) SLR for projections selected by NOAA for SLR by 2100.  Examining this figure one sees that not only is the Rohling et al high range higher than that for Pfeffer et al; but the Beta PDF from Pfeffer et al's work shows a good probability of exceeding Pfeffer et al's "limit" of 2m SLR by 2100.

Furthermore since 2008, SLR has only followed the high range and radiative forcing has exceeded the RCP 8.5 98%CL scenario; thus if one were to redraw today a PDF from Pfeffer et al 2008's work one would need to trim off some of the lower (left-hand) tail area associated with the low SLR range projections, and add to the upper (right-hand) trail area associated with the upper SLR range projections.  Indeed, the longer society follows the BAU path the more the SLR PDF for 2100 will shift to high values.

Also, in this post, I would like to note that since before 2000 the Earth has been in an El Nino hiatus period; and when this oscillation (the PDO) swings out of this hiatus period, SLR can be expected to accelerate beyond the values that we (and Pfeffer) have been observing recently.