Critique of Most Common SLR Guidance Criteria w.r.t Abrupt SLR

[AbruptSLR]

Given the possibility of global warming beyond a certain threshold no reasonable researcher or authority has questioned the possible loss of much or all of the AIS or GIS ice sheets; but what is debatable is the rate and timing of any such SLR contribution for ice sheets (IS).  The first pdf has a combined graph from: (a) the UN's WCRP task group comparing the AR3/AR4 SLR  GCM projection limits (without dynamic ice mass loss) and a red bar showing possible additional dynamic ice mass loss SLR contribution from the IS and a red arrow showing the possible SLR contribution from abrupt ice mass loss from the IS; and (b) the AR3/AR4 SLR projection limits with the observed SLR data provided by both V&R 2007 and extended by Steven Chu the former US Secretary of Energy.  The next figure from information provided by Pfeffer 2011 showing the potential SLR if the IS were to melt completely and information as to why AR4 did not include any significant dynamic ice melting (abrupt or otherwise).  The next figure/table showes Pfeffer et al. 2008 analysis of SLR contributions from the indicated sources for low1, low 2 and high scenarios; which have been widely quotes and cited as providing reasonable limits for SLR contributions from these sources in this century.  The next figure is from the NRC 2012 SLR analysis performed for the US West Coast States; which accepts/identifies some contributions this century to SLR from the IS, which is a signifigant departure from the AR4 SLR limits.

[AbruptSLR]

The next three figures all from the prematurely released IPCC SOD Chapter 13 on SLR show: (a) the projected SLR limits this century following the IPCC AR5 process; (b) the projected SLR limits this century according to the indicated semi-empirical models; and (c) the projected SLR limits through 2500 following the IPCC AR5 process.  Note that while all of these SLR projections now include some SLR contributions from the ISs, none of them recognize abrupt SLR contributions from the SLR within the time frames indicated.  Thus all of these widely accepted SLR limit guidance assume that the tail of the probability distribution for SLR is to thin to recognize the risk of abrupt SLR within the timeframes indicated.  The purpose of this thread is to critique the analyses behind these documents in order to highlight reasons omitted within these documents that would fatten the tail of the probability distribution sufficiently to justify the recognition of the risk of abrupt SLR this century within future version of such guidance documents at least in order to identify a suitable resiliency check case for future abrupt SLR.  Future as T. Pfeffer is an author common to all of these documents the critique of his SLR analysis begun in the "collapse" thread will be continued in this thread.

[AbruptSLR]

In Pfeffer et al 2008 the authors cite a maximum upper limit on SLR by 2100 that they could envision (at the time of writing) was 2.008m which included 0.394m of SLR due to dynamic ice mass loss from the PIG/Thwaites drainage basins by 2100 assuming a 120 sq km gateway and ice velocity accelerated from the 2 to 2.5 km/yr range in 2008 to 14.6 km/yr by 2100 which they justy as the upper limit because it was the highest ice velocity of any glacier on earth at the time of their writing.  It is noted that none of the guidance documents cited in the first two posts have projections of global SLR exceeding the 2.008m limit anytime before 2200.

With regard to specfic current common SLR guidance: NRC 2012 (for which Pfeffer is a co-author) refers to potential abrupt SLR as "rapid dynamic response" of ice sheets.  NRC 2012 directs almost all of its substantive statements regarding "rapid dynamic response" of ice sheets to land based ice sheet such as GIS and EAIS, and makes only one substantive direct statement regarding the risk of "rapid dynamic response" of WAIS which is: "Studies of such thresholds suggest that widespread denudation of Greenland and West Antarctica is possible in some warming scenarios, such as four times the preindustrial carbon dioxide (Ridley et al., 2010) or 5 C ocean warming (Pollard and DeConto, 2009), but requires thousands of years (e.g., Marshall and Cuffey, 2000; Pollard and DeConto, 2009; Ridley et al., 2010)."  In this statement only Pollard and DeConto, 2009 address the stability of the WAIS, but their simplified computer model was not capable of including the dynamic land-ice-ocean interaction effects (e.g. see Goldberg et al. 2012, or Gladestone et al., 2012 in the "surge" thread) that indicate a risk of the WAIS collapsing on the order of one hundred years.  NRC 2012 also make the following indirect refer to the WAIS, but confuses WAIS's unique status as the worlds only remaining marine based ice sheet by combining its potential response together with the GIS and the EAIS: "Despite rapid changes along the margins of the Greenland and Antarctic ice sheets, it is unlikely that the ice sheets will disappear over the next millennium. The ice sheets are so thick (Figures 3.6 and 3.7) that much of the surface is in higher, relatively cooler parts of the atmosphere, allowing a positive mass balance to be maintained even as the climate warms."  After thus dismissing the potential collapse of the WAIS in less than a millenia, NRC 2012 then states: "The committee projected the cryosphere contribution to global sea-level rise using adaptations of the Meier et al. (2007) extrapolation techniques and the Pfeffer et al. (2008) methods for evaluating uncertainty and establishing projection boundaries. The committee’s extrapolations were based on selected observational data for glaciers, ice caps, and the Greenland and Antarctic ice sheets."  The Meier et al. (2007) extrapolation techniques and the Pfeffer et al. (2008) methods for evaluating uncertainty and establishing projection boundaries, for ice mass loss contributions to SLR, are based largely on expert opinion (a heuristic approach) supplemented by some statistical techniques, and they were largely used by IPCC WG1's 2007 AR4 SLR recommendations (see Pfeffer 2011, and Table 9.2 and Table 5.1 of the NRC 2012 report), which now NRC 2012 and AR5 SOD indicate require major revisions to the AR4 projections. Furthermore, application of Meier et al (2007) and Pfeffer et al. (2008) approaches result in such NRC 2012 statements as the following:
-   "Increased ice discharge beyond presently observed rates was simulated by extrapolating a multiple of present-day observed discharge forward in time to 2100 (see Appendix E). For glaciers and ice caps, an increment of flux equal to 50 percent of the present-day discharge was added, equivalent to 162.4 GT yr-1. For Greenland, the average speed of all outlet glaciers was increased by 2 km yr-1, equivalent to a net discharge of 375.1 GT yr-1. These values are consistent with the observed doubling of Greenland’s mass balance deficit between ca. 1996 and 2000 (Rignot and Kanagaratnam, 2006). For Antarctica, the net outlet flux was doubled from its ca. 2006 value to 264 GT yr-1. All values were increased linearly over 20 years and held constant thereafter. The exact choice of values for the individual components is less important than the net added flux after the 20-year increase, which is approximately 800 GT yr-1 (2.2 mm yr-1 sea-level equivalent)."  It is noted here that per Figure 6.12 of NRC 2012, at the 95% CL level, all of the 2006 ice mass balance value of 264 GT yr-1 that NRC 2012 attributes to the AIS in reality all came from the WAIS, which distorts both NRC 2012's decision to only double this value over 20 years and then to hold it constant thereafter, and also to apply AIS fingerprint scaling factors instead of WAIS fingerprint scaling factors when determining RSLR values for California
-   "Decreased ice discharge was simulated by reducing the projected output of the Greenland Ice Sheet by 25 percent from its projected base value. Currently, about 50 percent of Greenland’s ice loss rate is caused by iceberg calving; a hypothetical 50 percent reduction in calving discharge yields a 25 percent reduction in the total ice loss rate. Other cryosphere terms were left unchanged. For Antarctica, systems likely to experience rapid change are concentrated on the Amundson Coast, and there are no known geographic features in the region that would likely serve as points of stabilization. Moreover, there is no reason to think that the dynamic slowdown seen recently in Greenland is likely to occur soon in Antarctica. Given the larger size of the Amundson Coast outlet glaciers, it is reasonable to hypothesize that any reversals will occur on longer timescales than the committee’s projections. For glaciers and ice caps, future discharge was left unchanged from the base-rate projection in this experiment. The fraction of glacier and ice cap loss from calving discharge is unknown, but is probably less than 50 percent. Thus, the committee assumed that direct climatically-forced surface mass balance is the primary control on future changes in the loss rate of glaciers and ice caps."  It is noted that NRC 2012's focus on the Amundsen Sea Coast outlet glacier inappropriately discounts the potential for abrupt (this century) WAIS ice mass loss from: (a) the Weddell Sea sector (see Hellmer et al. 2012); (b) the Bellingshausen Sea sector (see "surge" thread); (c) the Siple Coast sector (see the discussion in the "collapse" thread); and (d) the facts that snow mass loss from WAIS to the ocean due to increased wind velocity, and potential increased surface mass balance loss due to increased surface melting as WAIS surface temperatures more frequently raise above freezing.
-   "The cryosphere projections presented here have two types of uncertainties: quantified uncertainty and unquantified uncertainty. The quantified uncertainty, which is calculated from the 5–95 percent projection intervals (Appendix E) then converted to 1 σ uncertainties, is a statistical product representing the uncertainty of the curve fitting process. The unquantified uncertainty is associated with the assumption that past system behavior is a good predictor of future system behavior. Rapid dynamic response may play a different role in future sea-level rise than it did during the period of observations, making that period potentially a poor predictor of future system behavior. However, deviations of actual sea-level rise from the simple extrapolation will take time to emerge. Extrapolation of unstable or unpredictable dynamics will thus be reliable initially, but the errors may increase dramatically as the timescale of the extrapolation exceeds the characteristic timescale of the dynamics.  In theory, the uncertainty of the extrapolations could be evaluated by determining the characteristic timescale of rapid dynamic response of vulnerable land-based ice. The timescale for dynamics of individual outlet glacier systems is thought to be decades, whereas the timescale of aggregate outlet glacier systems, such as the marine-ending glaciers draining the Greenland Ice Sheet, may be a century or longer. This timescale has not been established, however, and contributes uncertainties that are both quantifiable and unquantifiable. New work on the time-varying aspects of dynamic response of outlet glaciers, such as the modeling study of Price et al. (2012), may lead to constraints on the timescales of rapid dynamic response."  It is noted that when discussing "unquantified uncertainty" the NRC 2012's focuses on Greenland inappropriately misdirecting attention away from the much large risk of abrupt (this century) SLR contribution from the potential rapid collapse of the WAIS in regard to: (a) warm CDW redirected mid-century beneath the Filchner-Ronne Ice Shelf thus both deteriorating the shelf and causing the grounding line of Weddell Sea sector glaciers to rapidly retreat; (b) continued calving of the RIS (following by mid-century initiation of the "melt pond" mechanism due to increase frequency of surface melting on RIS (c) warm CDW causing a rapid grounding line retreat of key Bel-lingshausen Sea sector glaciers prior to mid-century and (d) the initiation by mid-century of the collapse of key Amundsen Sea Embayment glaciers (including PIG and Thwaites), see related discussion in the "surge" thread (also see Goldberg et al. 2012, Schodlok et al. 2012, and Gladestone et al., 2012).

[AbruptSLR]

Furthermore with regard to the SLR guidance from the NRC 2012, the following observations are made regarding NRC 2012 use of the Meier et al. (2007) extrapolation techniques and the Pfeffer et al. (2008) methods for evaluating uncertainty and establishing projection boundaries, for ice mass loss contributions to SLR:
-   NRC 2012's SLR projections ignore the risk of portions of collapsing marine ice sheets floating-off the seafloor while remaining largely in place.  Note that the subglacial cavity calculated for, and observed at, the PIG substantiates my hazard scenario for WAIS collapse postulation that subglacial WAIS passageways could become sufficiently extensive by 2100 that SLR contribution from this mechanism could be significant.
-   NRC 2012's SLR projections are not directly correlated with either the SRES, or the RCP, families of radiative forcing scenarios, and thus are independent of radiative forcing func-tions (other than that considered by the initial expert opinion calibration).  Nevertheless, it is suspected that the expert opinion calibration by NRC 2012 assumes the probability distribution of the radiative forcings from the SRES family of scenarios, without recognizing that lower scenarios such as B1 are no longer reasonable to assume and that the cumulative probability distribution should be adjusted accordingly.
-   While NRC 2012 committee members are aware of the scientific community's concern about the potential collapse of the WAIS (see Pfeffer 2011), they choose to focus on the finding of four to five year old research to justify their opinion that the WAIS will not collapse faster than on a millennial scale, and they ignore, or discount, the majority of literature that indicates a significant possibility of at least a partial WAIS collapse this century.
-   Where NRC 2012 does reference radiative forcing for estimating steric SLR contribution they reference the old SRES scenarios instead of the new RCP scenarios and NRC 2012 does not note, or make correction for the fact that between 2000 and 2012 SLR has been following the RCP 8.5 95% CL SLR projections, and thus their lower steric range based on SRES B1 contains twelve years of non-conservative (or incorrect) input, and is not likely to be followed in the future.

Also, NRC 1987 acknowledges the risk of up to 3.5m of eustatic SLR by 2100.  It would be advisable for NRC 2012 to at least acknowledge a risk of multiple meters of SLR by 2100, which has been recognized by the scientific community to be a risk since at least the early 1980's.

[AbruptSLR]

The IPCC AR5 SOD contains many similar statements as the NRC 2012 document (possibly as Pfeffer is a co-author of both documents), and thus will not be reviewed here in such detail, rather the following briefly lists additional abrupt SLR risks specific to the Thwaites/PIG drainage systems (with particular focus on Thwaites as the "soft underbelly of the WAIS), which will be elaborated on in a new thread to soon be posted on projections of abrupt SLR risks to the 2040 - 2050 timeframe for the PIG/Thwaites ice drainage systems:
 - The Thwaites Glacier is unique in the ASE not only because of the ice mass size in its drainage basin but also because: (a) It has a relatively steep ice face slope that indicates this high ice weight driving force is currently being resisted at its gateway/threshold by relatively strong basal resistance, which could readily be neutralized by the postulated formation of an expanding subglacial cavity due to CDW and due to postulated increasing frequency of outbursts of basal melt water from the recently identified subglacial melt water network resulting in periodic surges of ice out from Thwaites; and (b) the thinness of the crust in the BSB resulting in an exceptionally high basal ice melting rate that resulting in the rapid re-supply of pressurized water to the subglacial lakes that are part of the Thwaites subglacial melt water network. It is noted that its is likely that the postulated subglacial cavity at the current threshold of the Thwaites Glacier has already intercepted a subglacial lake previously identified infront of a submerged mound on the east side of the west ice stream (see Tinto & Bell 2011), and it is postulated that such an interception would effectively provide the subglacial cavity with a branch extending many kilometers to the east thus introducing warm CDW to more ice on the east ice stream, while the main subglacial cavity begins to melt its way directly down into the BSB following the west ice stream. 
- If a sufficiently large subglacial cavity systems develops to disrupt the apparently high basal resistance at the current Thwaites threshold then, both the wide of the current threshold should increase and the groundling line could retreat over at least a 50km wide gateway forming an ice shelf over the north edge of the BSB, which would promote more ice mass loss by advective melting on the underside of the ice shelf and an acceleration of the ice stream velocities upward to possibly 4.5 km/yr by 2020; and then it is posulated that thinning of the ice shelf due to the subice shelf melting and the high ice flow velocities would further widen the gateway to approximately 100 km by 2040 and would extend the new Thwaites Ice Shelf all the way to the subglacial lake identified by Schroeder et al 2013 to be behind a damming bedrock ridge in a distributed canal system that is feeding a system of concentrated channels downstream.  It is postulated that once the grounding line retreats to this lake behind the damming bedrock ridge identified by Schroeder et al 2013, then the subglacial cavity would be immediately extended in an east-west direction resulting in the subglacial cavity extending rapidly on these two main branches (see the figures I drew on the Vaughen base figures in the "collapse" thread) by 2050. 
- Also, the ocean water around the ASE is anomolously high now and it is possible that over ten years of La Nina and ENSO neutral conditions have feed more than expected ocean heat content into the ASE CDW which would be promoting more rapid subglacial cavity advective melting than previously expected.
- If all of the rapid dynamic kinematics happens as describe above the associated internal friction within the Thwaites Glacier would cause enhances internal ice melting that would rain down through cracks in the glacial mass to increase the subglacial melt water and decrease basal friction, possibly enough to increase the average ice stream flow rates in the remaining grounded glacier to 6 km/yr.
- By 2050 the ice thinning at the Thwaites Glacier gateway may proceeded to such an extent that the prior buttressing action of the Thwaites Glacier to the ice in the PIG drainage basin may be reduced and some of the ice from the PIG basin may begin to flow into the Thwaites drainage basin.
- It is further noted here that the vertical advective melting action with a subglacial cavity is generally limited by the area of exposure of the CDW to the ice face and not on the heat content of the CDW.  Therefore, simplistic projections such as those discussed in earlier posts for the NRC 2012, of ice mass loss from the ASE glacier by simple multiple of currently observed ice mass loss rates, are almost certainly underestimates if the extensive subiceshelve areas are created as discussed above in this post (not that all of the old Thwaites Iceberg Tongue disintergated rapidly in the presences of the warm CDW within the ASE since the 1990s.
- As previously discussed in the "surge" thread I postulate that their is currently a horizontal advective synergy between the PIG and Thwaites systems that will help to promote the circulation of CDW into the ASE even if subglacial conditions temporarily become less conductive to subglacial cavity extension as Goldberg et al 2012 has projected may occur for the PIG grounding line retreat before 2040.  As Goldberg  et al did not consider this horizontal advection, the groundling retreat of PIG may not stall in 2040 and may continue beyond 2050 when its subglacial cavity is postulate to intercept a similar subglacial cavity coming from the Ferrigno Glacier.  If these two subglacial cavities were to intercept then tidal pumping of CDW through the interconnected cavities than ice mass loss would accelerate significantly.
- If the GIS ice mass loss is further accelerated between now and 2050 by: (a) albedo loss; (b) seasonal loss of the Arctic Sea Ice; and (c) activation of the Northern marine terminating glaciers; then the RSLR around ASE associate with the GIS ice mass loss, would help to destabilize the WAIS glaciers.

More specific information of such mechanisms that could promote abrupt ice mass loss from the PIG & Thwaites system will be elaborated in a new thread (by this weekend).

[AbruptSLR]

Most of the abrupt SLR mechanisms that I made in the immediately preceeding post deal primarily with the PIG/Thwaites rapid dynamic ice mass loss initiation phase behavior up until 2050; which result in SLR values similar to that shown in the accompanying figure by Hansen and Sato 2011 for the non-linear curve by Hansen 2007 until 2050.  The following mechansims are intented to present probable mechansims that could reasonably result in the highly non-linear response indicated by the Hansen 2007 curve for the period from 2050 to 2100 (which would be many times the rate of ice mass loss stated by Pfeffer et al 2008 to be an upper limit based on extremely simplified assumptions that could not possibly model (nor disprove a complex collapse scenario such as briefly discussed below):
- As stated in the prior post, by 2050 the ice in the BSB is assumed to have a significant ice shelf (above most of the BSB) as indicated by the image in the "collapse" thread for the state of the grounding line retreat into the BSB by 2050. In this condition the ice streams feeding into this BSB iceshelf may have average velocities of 4.5 to 6 km/yr plus significant advection of ice melt water from beneath the BSB ice shelf.  Now it is assumed that this BSB would be subject to the same ice melt pond collapse mechanism as proposed for the Ross Ice Shelf, RIS, after 2050; which would promote the entrance of large cyclones into both the Ross Sea Embayment and the ASE/BSB open water area as such storm gain significant energy from the temperature difference from the cold ice front and the relative warm adjoining water.  The low pressure at the center of such cyclones would raise the water elevation at the cyclone eye significantly resulting in significant ice calving of the ice front due to both ice flexure (from the elevated water surface) and due to wave action.
- Ice calving would also be promoted in the BSB area due to the branching of the subglacial cavities  that may likely follow the subglacial melt water flow network paths, which would result in many regions of ice ridges with little lateral support will would likely accelerate ice calving due to buoyant instability forces that have been observed in Greenland marine terminating glaciers.
- Icebergs caused by the accelerated calving (due to storms and buoyant instability of grounded ice ridges with inadequate lateral support) would be free to float out of the BSB area are rates several times higher than assumed by Pfeffer et al 2008 for ice mass loss from PIG/Thwaites.
- For PIG it is assumed that as the grounding line retreats the ice shelf front will also retreat thus activing the numerous side spurs to the main PIG trough thus accelerating ice mass loss from this area, and also that as stated previously significant amount of PIG ice mass will flow into the BSB area once buttressing from Thwaites is relieved.
- As indicated in the "forcings" thread the WAIS surface is warming at a rate of 0.8 C/decade, which from 2013 to 2073 would result in a surface temperature increase of 4.8 C which would be amplified by 2073- 2100 by significant albedo loss due to reductions in both sea ice and due to open water assumed to have occurs in the Ross Sea Embayment, over the BSB and possibly in the Weddell Sea Embayment.  Such high temperatures will support accelerated surface ice mass loss with increasing frequence (note it is also assumed that the Larsen C ice shelf would have collapse by 2050 resulting in more albedo driven warming of the Antarctic Peninsula.
- Again (see the "collapse" thread) by 2070 many of the subglacial cavities in the Ross, Weddell, Bellingshausen and Amundsen Sea area will have interconnected not only introducing tidal flushing into the interconnect system of subglacial cavity and seaways but will also change the current patterns between all four of these seas.
-  It is noted that by the 2060 to 2080 timeframe the group working with from Hellmer et al. 2012
have estimated that the glaciers around the Filchner-Ronne Ice Shelf could be contributing as much as 4mm/yr to sea level rise or as much as 0.160m from 2060 to 2100; but this group did not consider the likely changes in sea passageways and the loss of support from Thwaites, which could easily double this contribution of Weddell Sea ice mass loss to 0.32m by 2100.
- It is noted that the WAIS is already a highly seismically & vocanically active area, and the loss of such large amounts of projected ice mass loss by 2090 could result in significant seismic and vocanic activity as indicated by Behrendt 2011's conclusion that: "The present rapid changes in stability of the WAIS resulting from global warming, could be accelerated by subglacial volcanism."; which is also supported by the following quote from McGuire 2012 regarding the Iceland's response to the loss of a kilometer thick icesheet (as WAIS is considered here by 2090):

"Twenty thousand years ago, Iceland was entirely covered by a layer of ice that averaged close to a kilometer in thickness.  Around 15-16,000 year ago, planetary warming triggered rapid melting of the glaciers, reducing the load acting on the volcanoes beneath and on the underlying asthenosphere.  By 12,000 years ago unloading was sufficiently advanced to trigger a spectacular response.  Over a period of 1500 years or so, the volcanic eruption rate jumped by between 30 and 50 times, before falling back to today's level.  This volcanic rejuvenation was in part a reflection of the release of magma held ready and waiting, within and beneath the volcanoes themselves, but mainly testament to a huge increase in the supply of fresh magma from deeper within the Earth.  Such was the load reduction due to the rapid loss of ice mass, that the depressed lithosphere quickly bounced back by as much as half a kilometer, dramatically reducing the pressures in the asthenosphere and triggering a 30-fold jump in magma production."
- It is noted further that GIA in the Northern Hemisphere typically reduces actual sea level by moving magna from under to ocean to under places like Greenland (thus dropping the seafloor) but in the case of WAIS the GIA would raise the seafloor by multiple meters and the magna would likely come from beneath the EAIS thus lowering the elevation of the EAIS and promoting future (after 2100) ice mass loss from glaciers in the EAIS.
-Further the collapse of the WAIS would active numerous adjoining EAIS ice streams (such as the Byrd Glacier) that were previously buttressed by the WAIS.
- It is also noted that the loss of the abrupt ice mass loss from WAIS would help to destabilize some of the large marine terminating glaciers in GIS by the end of the century thus accelerating their contribution to SLR
-It is important to note that for the collapse of the WAIS to contribute to SLR this century, that as Hansen points out, it is not necessary for the ice to melt, only for the grounded ice to float, so there may likely be many icebergs floating all around the Southern Ocean by 2100.

[AbruptSLR]

On the off chance that some of the authors of the IPCC AR5 WG1 on SLR (and/or other Forum readers) might have missed (or missed the significance of) some of the following references published before the AR5 cut-off date I thought that I would provide (on this & the next post) the following list of references that thought contributed value to the potential of abrupt SLR:
[1]   Bamber, J. L., Riva, R. E. M., Vermeersen, B. L. A. & LeBrocq, A. M., (2009),  "Reassessment of the potential sea-level rise from a collapse of the West Antarctic Ice Sheet", Science, 324, pp. 901–903.
[2]   Barnes, D. K. A., and Hillenbrand, C. D., (2010), "Faunal evidence for a late quaternary trans-Antarctic seaway", Glob. Change Biol., 16, pp. 3297–3303.
[3]   Boon, X.Y.R., (2011), Basal Roughness of Upper Thwaites Glacier, A Master of Science Thesis in Geosciences from the Pennsylvania State University - Department of Geosciences, August 2011.
[4]   Bradley, S.L., Siddall, M., Milne, G.A., Masson-Delmotte, V., and Wolff, E., (2012), "Where might we find evidence of a Last Interglacial West Antarctic Ice Sheet collapse in Antarctic ice core records?", Global and Planetary Change 88-89 (2012) 64–75.
[5]   Branecky, C., Kirshner, A.E, Anderson, J.B., and Nitsche, F.O., (2011), "Organized Subglacial Meltwater Flow in Inner Pine Island Bay, West Antarctica" AGU conference presentation.
[6]   Bromirski, P. D., O. V. Sergienko, and D. R. MacAyeal (2010), Transoceanic infragravity waves impacting Antarctic ice shelves, Geophys. Res. Lett., 37, L02502, doi:10.1029/2009GL041488.
[7]   Colville, E.; A.E. Carlson, B.L. Beard, R.G. Hatfield, J.S. Stoner, A.V. Reyes, and D.J. Ullman; "Sr-Nd-Pb Isotope Evidence for Ice-Sheet Presence on Southern Greenland During the Last Interglacial"; Science, Vol. 333 No. 6042, 29 July 2011, pp 620-623, doi: 10.1126/science.1204673.
[8]   Conway, H., Hall, B.L., Denton, G.H., Gades, A.M., and Waddington, E.D., "Past and Future Grounding-line Retreat of the West Antarctic Ice Sheet", Science 8 October 1999, Vol. 286 no. 5438 pp. 280-283 DOI: 10.1126/science.286.5438.280.
[9]   Corr, H.F., and Vaughan, D.G., (2008), "I recent volcanic eruption beneath the West Antarctic ice sheet", Nature Geoscience Letters, Vol. 1, February 2008, doi: 10.1038/ngeo106.
[10]   Deschamps, P., Durand, N., Bard, E., Hamelin, B., Camoin, G., Thomas, A.L., Henderson, G.M., Okuno, J., and Yokoyama, Y., (2012), " Ice-sheet collapse and sea-level rise at the Bølling warming 14,600 years ago", Nature, Vol. 483, 559, doi:10.1038/nature10902
[11]   Elliott, S., Maltrud, M., Reagan, M., Moridis, G., and Cameron-Smith, P., "Marine methane cycle simulations for the period of early global warming", Journal of Geophysical Research, Vol. 116, G01010, doi: 10.1029/2010JG00 1300, 2011.
[12]   Fyke, J.G., Weaver, A.J., Pollard, D., Eby, M., Carter, L., and Mackintosh, A.; "A new coupled ice sheet/climate model: description and sensitivity to model physics under Eemain, Last Glacial Maximum, late Holocene and modern climate conditions", Geosci. Model Dev., 4, 117-136, 2011, doi: 10.5194/gmd-4-117-2011.
[13]   Fox. D., (2012), "Witness to an Antarctic Meltdown", Scientific American, July 2012, pp. 54-61.
[14]   Gladstone, R., Cornford, S., Edwards, T., Lee, V., Payne, A., and Shannon, S., (2011), "Calibrated prediction of future Pine Island Glacier behavior", Geophysical Research Abstracts, Vol. 13, EGU2011-12800, EGU General Assembly 2011.
[15]   Gladstone, R.M., Lee, V., Rougier, J., Payne, A.J., Hellmer, H., LeBrocq, A., Shepherd, A., Edwards, T.L., Gregory, J., and Cornford, S.L., (2012), "Calibrated predictionof Pine Island Glacier retreat during the 21st and 22nd centuries with a couple flowline model", Earth and Planetary Science Letters, 333–334 (2012) 191–199.
[16]   Goldberg, D. N., Little, C. M., Sergienko, O. V., Gnanadesikan, A., Hallberg, R. and Oppenheimer, M.  (2012), "Investigation of land ice-ocean interaction with a fully coupled ice-ocean model: 1. Model description and behavior", J. Geophys. Res., 117, F02037, doi:10.1029/2011JF002246.
[17]   Goldberg, D. N., Little, C. M., Sergienko, O. V., Gnanadesikan, A., Hallberg, R. and Oppenheimer, M.  (2012a), "Investigation of land ice-ocean interaction with a fully coupled ice-ocean model: 2. Sensitivity to external forcings", J. Geophys. Res., 117, F02038, doi:10.1029/2011JF002247.
[18]   Gomez, N., Mitrovica, J. X., Huybers, P., and Clark, P. U., (2010), "Sea level as a stabilizing factor for marine-ice-sheet grounding lines", Nature Geosci., 3, pp. 850–853.
[19]   Graham, A.G.C., Nitsche, F.O. and Larter, R.D., (2011), "An improved bathymetry compilation for the Bellingshausen Sea, Antarctica, to inform ice-sheet and ocean models", The Cryosphere, 5, 95–106, 2011, doi: 10.5194/tc-5-95-2011.
[20]   Hansen, J.E., and Sato, M. (2011a), "Paleoclimate Implications for Human-Made Climate Change", NASA Goddard Institute for Space Studies and Columbia University Earth Institute, New York.
[21]   Hansen, J.E., and Sato, M., 2012, "Climate Sensitivity Estimated From Earth's Climate History", NASA Goddard Institute for Space Studies and Columbia University Earth Institute, New York.
[22]   Hansen, J., Sato, M. and Kharecha, P. (2011b), "Earth's Energy Imbalance and Implications", NASA Goddard Institute for Space Studies, New York City, New York and von Schuckmann, K., Centre National de la Recherche Scientifique Laboratoire de Physique des Oceans France.2011.
[23]   Hansen, J., Sato, M. and Ruedy, R. (2012), "Perceptions of Climate Change: The New Climate Dice".
[24]   Heimbach, P., and Losch, M., (2012), "Adjoint sensitivities of sub-ice-shelf melt rates to ocean circulation under the Pine Island Ice Shelf, West Antarctica", Annals of Glaciology 53(60), doi: 10.3189/2012/AoG60A25.
[25]   Hellmer, H.H., Kauker, F., Timmermann, R., Determann, J., and Rae, J. (2012) "Twenty-first-century warming of a large Antarctic ice-shelf cavity by a redirected coastal current" Nature, Vol. 485, May 10, 2012, p. 225. doi: 10.1038/nature11064.
[26]   Howarth, R.W., Santoro, R. and Ingraffea, A., (2011), "Methane and the greenhouse-gas footprint of natural gas from shale formations", Climate Change, doi:10.1007/s10584-011-0061-5, 2011.
[27]   Howarth, R., Shindell, D., Santoro, R., Ingraffea, A., Phillips, N., and Townsend-Small, A., (2012a), "Methane Emissions from Natural Gas Systems", Background Paper Prepared for the National Climate Assessment Reference number 2011-0003, February 25, 2012.
[28]   Howarth RW, Santoro R, and Ingraffea A (2012b). "Venting and leakage of methane from shale gas development: Reply to Cathles et al. Climatic Change", doi:10.1007/s10584-012-0401-0.
[29]   Jakobsson, M., Anderson, J.B., Nitsche, F.O., Gyllencreutz, R., Kirshner, A.E., Nirchner, N., O'Regan, M., Mohammad, R., and Eriksson, B. (2012), "Ice sheet retreat dynamics inferred from glacial morphology of the central Pine Island Bay Trough, West Antarctica", Quaternary Science Reviews, 1-10.
[30]   Joughlin, I., and Alley, R.B., (2011), "Stability of the West Antarctic Ice Sheet in a Warming World", Review Article, Nature Geoscience, 24 July 2011/ doi: 10.1038/NGE1194
[31]   Joughlin, I., B.E. Smith and D.M. Holland, (2010),"Sensitivity of 21st century sea level to ocean-induced thinning of Pine Island Glacier, Antarctica", Geophysical Research Letters, Vol. 37, 2010, doi: 10.1029/2010GL044819.
[32]   Katz, R.E, and Worster, M.G. (2010), "Stability of ice-sheet grounding lines", Philos. Trans. R. Soc. A, 466 (2118), 1597-1620, doi:10.1098/rspa.2009.0434.
[33]   Khazendar, A., Rignot, E. and Larour, E. (2011), Acceleration and spatial rheology of Larsen C Ice Shelf, Antarctic Peninsula, Geophys. Res. Lett., 38, L09502, doi:10.1029/2011GL046775.
[34]   Kopp, R. E., Simons, F. J., Mitrovica, J. X., Maloof, A. C., and Oppenheimer, M., (2009), "Probabilistic assessment of sea level during the last interglacial stage", Nature, 462, pp. 863-867.
[35]   Lamarque, J.F. (2008), "Estimating the potential for methane clathrate instability in the 1% CO2 IPCC AR-4 simulations", Geophys. Res. Lett., 35, L19806, doi: 10.1029/2008GL035291.
[36]   Larour, E., Schiermeier, J., Rignot, E., Seroussi, H., Morlighem, M. and Pade, J.; (2012), "Sensitivity Analysis of Pine Island Glacier ice flow using ISSM and DAKOTA", J. Geophys. Res., 117, F02009, doi:10.1029/2011JF002146.
[37]   Lempert, R., Sriver, R.L. and Keller, K., (2012); "Characterizing Uncertain Sea Level Rise Projections to Support Investment Decisions" Report to POLA.
[38]   Levermann, A., T. Albrecht, R. Winkelmann, M.A. Martin, M. Haseloff, and I. Joughin, (2011), "Kinematic first-order calving law implies potential abrupt ice-shelf retreat", The Cryosphere Discussion, 5, 2699-2722, 2011 doi: 10.5194/tcd-5-2699-2011.
[39]   Luckman, A., Jansen, D., Kulessa, B., King, E.C., Sammonds, P., and Benn, D.I., (2012), "Basal Crevasses in Larsen C Ice Shelf and implications for their global abundance", The Cryosphere, 6, 113-123, doi:10.5194/tc-6-113-2012.
[40]   MacGregor, J.A., Catania, G.A, Markowski, M.S., Andrews, A.G. (2012); "Widespread rifting and retreat of ice-shelf margins in the eastern Amundsen Sea Embayment between 1972 and 2011"; Journal of Glaciology; 58 (209): 458 DOI: 10.3189/2012JoG11J262

[AbruptSLR]

Here is the rest of my list of selected references on this topic:
[41]   Martin, M.A., R. Winkelmann, M. Haseloff, T. Albrecht, E. Bueler, C. Khroulev, and A. Levermann, "The Potsdam Parallel Ice Sheet Model (PISM-PIK) - Part 2: Dynamic equilibrium simulation of the Antarctic ice sheet", The Cryosphere, 5, 727-740, 2011, doi: 10.5194/tc-5-727-o2011.
[42]   MacGregor, J.A., Catania, G.A., Markowski, M.S., Andrews, A., (2012), "Widespread rifting and retreat of ice-shelf margins in the eastern Amundsen Sea Embayment between 1972 and 2011", Journal of Glaciology, Vol. 58, No. 209, doi: 10.3189/2012JoG11J262.
[43]   McGuire, B, (2012), Waking The Giant: How a Changing Climate Triggers Earthquakes, Tsunamis and Volcanoes, Oxford University Press, 320p.
[44]   Muhs, D.R., Simmons, K.R, Schumman, R.R., Groves, L.T., Mitrovica, J.X., and Laurel, D., (2012), "Sea-level history during the last interglacial complex on San Nicolas Island, California: Implications for glacial isostatic adjustment processes, paleozoogeography, and tectonics", NSF Workshop on: Sea-level changes into the MIS 5: from observations to prediction, Palma de Mallorca, April 10-14, 2012, and Quaternary Science Reviews, doi: 10.1016/j.quascirev.2012.01.010.
[45]   Muhs, D.R., Simmons, K.R., Schumann, R.R., Halley, R.B. (2011). Sea-level history of the past two interglacial periods: new evidence from U-series dating of reef corals from south Florida. Quaternary Science Reviews, 30: 570-590.
[46]   NRC, (2012), Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future, Committee on Sea Level Rise in California, Oregon, and Washington; Board on Earth Sciences and Resources and Ocean Studies Board; Division on Earth and Life Studies; The National Academies Press, Washington, D.C.
[47]   Orsi, A.J., Cornuelle, B.D., and Severinghaus, J.P., (2012), "Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide", Geophysical Research Letters, vol. 39.
[48]   Pfeffer, W.T., Harper, J.T., and O'Neel, S., (2008), "Kinematic constraints on glacier contribution to 21st-century sea-level rise", Science 321, 1340-1343, 2008.
[49]   Pfeffer, W.T., (2011), "Land Ice and Sea Level Rise A Thirty-Year Perspective", Oceanography, Vol. 24, No. 2, pp. 95 - 111.
[50]   Plate, C., Muller, R., Humbert, A., and Gross, D. (2012), "Evaluation of the criticality of cracks in ice shelves using finite element simulations", The Cryosphere Discussion, 6, 469-503, doi: 10.5194/tcd-6-469-2012.
[51]   Pollard, D., and DeConto, R.M., (2009), "Modeling West Antarctic ice sheet growth and collapse through the past five million years", Nature, 458, 329-332.
[52]   Previdi, M., Leipert, B.G., Peteet, D.T., Hansen, J.E., Beerling, D.J., Broccoli, A.J., Frolking, S., Galloway, J.N., Heimann, M., Le Quere, C., Levitus, S., and Rarnaswamy, V., (2011), "Climate sensitivity in the Antropocene" Earth Syst. Dynam. Discuss., 2, 531-550, doi: 10.5194/esdd-2-531-2011.
[53]   Rahmstorf, S., Perrett, M., and Vermeer, M. (2011), "Testing the robustness of semi-empirical sea level projections", Clim Dyn, Springer-Verlag, doi: 10.1007/s00382-011- 1226-7.
[54]   Rahmstorf, S., and Vermeer, M., (2011), "Discussion of: Houston, J.R. and Dean, R.G., 2011.  Sea-Level Acceleration Based on U.S. Tide Gauges and Extensions of Previous Global Gauge Analyses", Journal of Coastal Research, 27(3), 409-417.  Journal of Coastal Research, 27(4), 784-787.  West Palm Beach (Florida), ISSN 0749-0208.
[55]   Reagan, M.T. (PI), (2011), Interrelation of Global Climate and the Response of Oceanic Hydrate Accumulations, Lawrence Berkeley Laboratory: Task Report 10-1, January 31, 2011.
[56]   Reagan, M.T., and Moridis, G.J. (2008), "Dynamic response of oceanic hydrate deposits to ocean temperature change", J. Geophys. Res., 113, 107, 486-513, doi: 10.1029/2008JC004938.
[57]   Rigot, E., Bamber, J.L., Van Den Broeke, M.R., Davis, C., Li, Y., Van De Berg, W.J., and Van Meijgaard, E., (2008), "Recent Antarctic ice mass loss from radar interferometry and regional climate modeling", Nature Geoscience
[58]   Rignot, E., Mouginot, J., and Scheuchl, B., (2011), "Ice Flow of the Antarctic Ice Sheet" Science, Vol 333, 9 Sept. 2011, pp 1427-1430.
[59]   Rignot, E., I. Velicogna, M. R. van den Broeke, A. Monaghan, and J. Lenaerts (2011), “Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise.” Geophysical Research Letters 38 (5) (March). doi:10.1029/2011GL046583.
[60]   Romig, A.D., Backus, G.A., and Baker, A.B. (2010); A Deeper Look at Climate Change and National Security; Sandia National Laboratories Report: SAND2011-0039; March 2010
[61]   Ross, N., Bingham, R.G., Corr, H.F.J., Farraccioli, F., Jordan, T.A., Brocq, A.L., Rippin, D.M., Young, D, Blankenship, D.D., Siegert, M.J., (2012), "Steep reverse bed slope at the grounding line of the Weddell Sea sector in West Antarctica", Nature Geoscience, doi:10.1038/ngeo1468, 09 May 2012
[62]   Salo, K., Hallquist, M., Jonsson, A.M., Saathoff, H., Naumann, K.-H., Spindler, C., Tillmann, R., Bohn, B., Rubach, R., Mentel, Th.F., Muller, L., Hoffmann, T., and Donahue, N.M. (2011); "Volatility of secondary organic aerosol during OH radical induced ageing"; Atmos. Chem. Phys., 11, 11055-11067, 2011; doi: 10.5194/acp-11-11055-2011.
[63]   Sanderson, B.M., O'Neill, B.C., Kiehl, J.T., Meehl, G.A., Knutti, R., and Washington, W.M., (2011), "The Response of the Climate System to Very High Greenhouse Gas Emission Scenarios" Environmental Research Letters July 2011, 11p / doi: 10.1088/1748-9326/6/3/0334005.
[64]   Sasgen, I., Konrad, H., Ivins, E.R., van den Broeke, M.R., Bamber, J.L., Martinec, Z. and Klemann, V. (2012), "Antarctic ice-mass balance 2002 to 2011: regional re-analysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment", The Cryosphere Discuss., 6, 3703-3732, doi: 10.5194/tcd-6-3703-2012.
[65]   Scherer, R. P. et al. (1998), "Pleistocene collapse of the West Antarctic Ice Sheet", Science, 281, pp. 82–85.
[66]   Scheuchl, B., Mouginot, J., and Rignot, E., (2012) "Twelve years of ice velocity change in Antarctica observed by RADARSAT-1 and -2 satellite radar interferometry"; The Cryosphere Discuss., 6, 1715–1738, 2012 doi:10.5194/tcd-6-1715-2012.
[67]   Schodlok, M.P., Menemenlis, D., Rignot, E., and Studinger, M., (2012) "Sensitivity of the ice-shelf/ocean system to the sub-ice-shelf cavity shape measured by NASA IceBridge in Pine Island Glacier, West Antarctica", Annals of Glaciology 53(60) 2012 doi: 10.3189/2012AoG60A073.
[68]   Schuur, E.A.G. and Abbott, B., (2011), "High risk of permafrost thaw", Nature, 480, 32-33, Dec. 2011.
[69]   Shakun, J.D., et al. (2012), "Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation", Nature, 484, 49-U1506.
[70]   Shindell, D.T., Faluvegi, G., Koch, D.M., Schmidt, G.A., Unger, N., and Bauer S.E. (2009), "Improved Attribution of Climate Forcing to Emissions" Science, Vol. 326 no. 5953 pp. 716-718, DOI: 10.1126/science.1174760
[71]   Siddall, M., Milne, G.A., (2011), "Understanding sea-level change is impossible without both insights from paleo studies and working across disciplines", Earth Planet. Sci. Lett. (2011), doi:10.1016/j.epsl.2011.10.023
[72]   Schneider, D.P, Deser, C., and Okumura, Y., (2011), "An assessment and interpretation of the observed warming of West Antarctica in the austral spring" Clim Dyn (2012) 38:323–347, DOI 10.1007/s00382-010-0985-x.
[73]   Steig, E., Schneider, D., Rutherford, S., Mann, M., Comiso, J., and Shindell, D. (2009). Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year. Nature, 457, 459-463. doi:10.1038/nature07669.
[74]   Steig E.J., Ding Q., Battisti D.S. and Jenkins A. (2012) "Tropical Forcing of Circumpolar Deep Water inflow and outlet glacier thinning in the Amundsen Sea Embayment", West Antarctica. Ann. Glaciol., 53(60), 19–28 doi: 10.3189/2012AoG60A110.
[75]   Strugnell, J.M., Watts, P.C., Smith, P.J. and Allcock, A.L. (2012), "Persistent genetic signatures of historic climatic events in an Antarctic octopus". Molecular Ecology. DOI: 10.1111/j.1365-294X.2012.05572.x.
[76]   Tinto, K. J. and R. E. Bell (2011), "Progressive unpinning of Thwaites Glacier from newly identified offshore ridge - constraints from aerogravity", Geophys. Res. Lett., doi:10.1029/2011GL049026.
[77]   Vaughan, D.G., Barnes, D.K.A., Fretwell, P.T., and Bingham, R.G., (2011), "Potential seaways across West Antarctica", Geochemistry Geophysics Geosystems, Vol. 12, No. 10, 7 October 2011, doi: 10.1029/2011GC003688.
[78]   Vaughan, D. G., and Spouge, J. R., (2002), "Risk estimation of collapse of the West Antarctic Ice Sheet", Climatic Change 52, pp. 65–91.
[79]   Willis, J.K. and Church, J.A., (2012), "Regional Sea-Level Projection", Science, Vol. 336, pp 550-551.
[80]   Winkelmann, R., Levermann, A., Krieler, K., and Martin, M.A., (2012), "Uncertainty in future solid ice discharge from Antarctica", The Cryosphere Discuss., 6, 673-714, doi:10.5194/tcd-6-673-2012.

[AbruptSLR]

OldLeatherneck requested that I provide a glossary and the following incomplete list of key terms and acronyms (more definitions can be found in the papers in the list of references previously posted in this thread):


AIS: Antarctic Ice Sheets
 
Albedo Flip: Albedo is a measure of the reflectivity of Earth’s surface.  "Albedo flip" is a term that  describes the process by which a  former heat-reflecting ice surface will become a heat-absorbing body of water.

AR3, AR4: IPCC Assessment Reports 3, and 4, respectively.

BAU: "Business as Usual"; as it relates to SLR, in a BAU scenario, no measures are taken to mitigate or arrest the conditions that cause global climate changes.

CL: Confidence Level

ENSO: El Nino Southern Oscillation

GCM: General Circulation or Global Coupled Model

GHG: Green House Gas

GIC: Glaciers and Icecaps

GIS: Greenland Ice Sheet

LIG: Last Interglacial

MIS: Marine Isotope Stage

NAS: National Academy of Sciences

NRC: National Research Council

PDF: Probability Distribution Function

RCP:  Representative Concentration Pathways

RSLR: Relative Sea Level Rise

SRES: Special Report on Emission Scenarios

SST: Sea Surface Temperature

WAIS: West Antarctic Ice Sheet (the last marine ice sheet in the world)

WCRP: UN, WCRP Task Group on Sea Level Variability and Change

[AbruptSLR]

The first image is from the USACE's EC 1165-2-212 (2011) based largely on data processed by NOAA, indicates the USACE's recommended guidance for addressing the uncertainties and standard error of linear trend of SLR vs the period of record in the US.  Based on such information the USACE requires a minimum threshold of a 40-year observation period before they recognize that a SLR trend has an acceptable uncertainty (standard error) to be used in design.  As the standard error data presented in the first image was gathered during an era with little ice mass loss contribution, such guidance is of little value in estimating the future contributions to SLR of such sources.  In an attempt to address the risk of ice mass loss the USACE's EC 1165-2-212's (2011) provides the graph shown in the second attached image, which provides guidance for the civil engineer to design civil works to the lower Modified NRC-I curve (which as indicated falls within the IPCC AR4 95% Confidence Levels projections that only consider thermal expansion of the oceans), and only to plan for (but not to design for) the Modified NRC-II and -III curves, which include SLR contributions from land-based ice mass loss.  However, even the Modified NRC-III curve does not include the risk of abrupt SLR from a potential collapse of the WAIS this century.

[AbruptSLR]

I thought that I would post this image of Eustatic Sea Level Rise Projects after NRC, 1987.  As the indicated "High" sea level by 2100 per Hoffman 1983 was 3.5m; this figure indicates how intimidation of climate science after 1983 has induced researchers to adopt "least drama" SLR projections with lower "High" projections.  The risks of high SLR were evident to researchers before 1983; but what has changed in the meantime is researchers' increased reticence to express their true opinion on this matter.

[prokaryotes]

Why least drama in messaging the science? Apparently "least drama" wasn't very successful so far...

[Anne]

Yes, please tell us more about "intimidation of climate science after 1983". That was when the NAS report was published... Who was intimidating the scientists, and how? And what is the evidence? I know nothing about this.

[FredFriendly]

I would agree that noone was intimidated, but incentives for funding change and you're alot better off if your hypothesis fits the current norm and supports the status quo.  A good read: http://www.bmartin.cc/pubs/92prom.html

[AbruptSLR]

I have no interest in providing details of the various kinds of intimidation that researchers have been subjected to as these have been discussed elsewhere in this blog, and one can easily Google this subject to find more information; however, I provide two very quick examples of such an easy to perform Google search on the intimidations that Michael Mann has been subjected to (he lost his job, his has been subjected to congressional subpoenas that were parts of witch hunts; and has had death threats made on himself and his family):

In the first linked video made just over one year ago Mann says that the world will not reach 400 ppm of carbon dioxide until 2014; but the world reached this level in 2013; indicating even Michael Mann is showing scientific reticince:


http://abcnews.go.com/US/video/mann-michael-blakemore-bill-global-warming-science-climate-earth-interview-16732895


The second link leads to another video from July 2013 which privide more details (and shows that Mann is starting to get his feet under himself from earlier intimidation):

http://thinkprogress.org/climate/2013/07/09/2272181/mann-of-steel-new-film-starring-author-of-the-hockey-stick-and-the-climate-wars/

Mann is only one easy example to reference (even James Hansen has lost his job due to his administration getting tired of his efforts to bring the hazards of climate change before the public) of intimidation.  But as focusing on this topic of intimidation is a distraction from the real topic of how to change public policy to better deal with the risks of abrupt sea level rise; my future posts will focus developing a path forward towards actually protecting public safety rather than participating in a delaying campaign of fiddling while Rome burns.

[Anne]

I see what you mean. I didn't realise there'd been anything more alarming than scientific disagreement, and the suggestion of intimidation startled me.

However, as you say, let's get back to business. I have no wish to derail the thread.

[AbruptSLR]

Ann,

As you say lets get back to business, and while I am not interested in discussing the details of why over thirty years ago scientists were more open about making policy recommendations (which is what NRC 1987 was) about the true risks of SLR; than they were in NRC 2012 (which is a policy guidance document on SLR, see: NRC, (2012), Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future, Committee on Sea Level Rise in California, Oregon, and Washington; Board on Earth Sciences and Resources and Ocean Studies Board; Division on Earth and Life Studies; The National Academies Press, Washington, D.C.); and also than they are likely to make in September 2013 in AR5 (based on the leaked draft cited earlier in this thread); I am willing to clarify to readers some of the reasons why they should not be surprised when it the future: (a) when their flood insurance premiums escalate rapidly when no flood defense systems have been built; and (b) when policy makers tell them that they are responsible for carrying the burden of their own flood losses because the number of flood cases has exceeded the limit of the public purse to help them after a flood event.

First, I would like to note that decision makers (policy makers) are responsible for public safety, not scientists (who only provide recommendations).  Therefore, it is fine with me that scientists exhibit natural reticence (even without intimidation) as they may likely be trying to ensure the integrity of the scientific process (which may be slow); while it is the decision makers' responsibility to conduct additional hazard assessments of the risks to public safety for factors beyond those that traditional engineering design practice consider for public works subjected to flooding related to SLR.

Now I would like to present the attached image that illustrates the relationship of inherent systemic uncertainty and climate system response (upper panel), and inherent systemic uncertainty in modeling and forcing parameters (lower panel), from Keller (2011).
(See: Keller, K., (2011), "Bayesian Decision Theory and Climate Change", Encyclopedia of Energy, Natural Resource and Environmental Economics, Elsevier Academic Press, ed. Shogren, J., 2011)

In both panels of this figure, the conceptual model for Expert A (the reticent expert) are shown in blue lines; while the conceptual model for Expert B (the precautionary expert) are shown in red lines.  Now in the upper panel the "climate state in question" (here SLR) is either subject to a potential threshold (a tipping point) as indicated by the red curve, or it is not as indicated by the blue curve.  Now the lower panel shows the consequences of assuming one of these two different situations on the shapes of probability density function (PDF) used by engineers to safe guard public safety.  I note here that the blue PDF (of Expert A) matches closely to the Ice2sea PDF that I have discussed elsewhere (and these Ice2sea findings will likely be cited in justifying the SLR positions presented in AR5); while the red PDF (of Expert B) closely match the shapes of the PDFs that I have posted in many threads (first in the "Philosophical" thread).

Now I would like to note that in this Antarctic folder I have provided well over 700 posts citing specific well-documented physical mechanisms that indicate that the Expert B model of the world (w.r.t. ASLR) has a high likelihood of being correct and I believe that with each passing year more evidence will be published reducing the uncertainties regarding the Expert B model (the precautionary model).  For example, it appears that AR5 (Expert A) will maintain the position that the Arctic Sea Ice, ASI, will not disappear seasonally (in September) until about 2050 (according to published statements made by Peter Wadham who is reviewing AR5); while many other experts (Expert B, see the ASIB) believe that the ASI will be seasonally ice "free" (less than 1million sq km of ice in September) by about 2017; which would represent one "potential threshold" being over-tipped that could contribute to numerous subsequent positive feedback mechanisms leading to ASLR by 2100.

I will provide more comments on this topic when I have more time.

[AbruptSLR]

I would like to note that offshore oil/gas drilling companies have been well aware of climate changes related to sea state conditions since at least the early 1980's; and they have developed rational design procedures to deal with the risks of extreme weather on their offshore equipment/vessels/platforms; however, flood protection authorities have not yet adopted these more advanced risk-based design procedures; largely because the public through their civil servant have not yet demanded the adoption of more advanced risk based (including hazard analyses) design procedures.

Data collected in the 1980's indicated that sea states of unexpected severity occur more often than previously assumed by offshore/marine rules with the projected climate change and increasing extreme weather still more severe sea state conditions can be expected.  As a historical example, the process to change the Norwegian offshore standards to address these bifurcated changes in sea states has already been implemented focusing on the risk based approaches based on modern reliability methods.  NORSOK Standard for offshore platforms requires consideration of a one in a 10,000-year event as a check for structural integrity (Accidental Limit State, ALS), including consideration of cases with a "fat-tailed" annual load distribution ("bad-behaving problem" in the attached figure).  If an annual load distribution has a "smooth-tailed" ("well behaving problems" in the attached figure), i.e. there is no sudden change of the tail for annual exceedance-probabilities in the range of 10^-2 to 10^-4, then the design is governed by the traditional Ultimate Limit State, ULS, limit case.  For the ULS case, the traditional design load and resistance partial safety factors will ensure a sufficient margin against structural failure.  However, if the wave loading mechanism is such that a "fat-tailed" annual load distribution occurs in the range of an annual exceedance-probability between 10^-2 and 10^-4 ("bad-behaving problem" in the attached figure) then the ULS design margins may not lead to a sufficiently low failure probability; and the new offshore design criteria requires that additional safety measures be taken before the equipment/vessel/structure can be insured.

It would be relatively easy for flood protection authorities to adopt similar risk-based design criteria in order to enhance public security from future SLR (note future SLR design cases always include weather related [storm related] load combinations); however, the public is reticent to demand that public officials take the appropriate measures.

[AbruptSLR]

For those who are interested in learning more about one of the risk-based design procedures that I referred to in my immediately preceeding post can learn about "Probabilistic Safety Assmessments" (PSA's) at the following weblinks:

http://psa2013.org/

http://www.psam2013.org/

[AbruptSLR]

The linked announced Sept 2013 workshop focused on ice-ocean interactions for Antarctica; indicates that the researchers sponsoring this workshop believe that the 1-ft to 7-ft currently projected range of SLR by 2100 (see NOAA December 2012) may be too low, and they are working on new and improved SLR projections:


http://kiss.caltech.edu/workshops/ocean-ice2013/index.html


"The Sleeping Giant: Measuring Ocean Ice Interactions in Antarctica; September 9 - 12, 2013
California Institute of Technology; Pasadena, CA 91125

Sea level rise remains one of the most poorly predicted and potentially costly impacts of human caused climate change. Projections for sea level rise between now and 2100 range from 1 to 7 feet, which could affect hundreds of millions of people worldwide. This dramatic range of uncertainty frustrates decision making at all levels, from government to industry to individuals. Global sea level depends on a complex, inter-connected system with many components. But the ice sheets of Greenland and Antarctica, which contain ice equivalent to 80 meters of sea level, are the most critical and most uncertain components of this system.
Recent work has suggested that interactions between the ocean and marine terminating glaciers may control the fate of some ice sheets. For example, in West Antarctica much of the ice rests below current sea level and is connected to the oceans through ice streams and outlet glaciers like Pine Island and Thwaites. It has been postulated that these two glaciers—both of which are thinning rapidly—are reacting to warm Circumpolar Deep Water that is intruding from the north, a process that could ultimately cause the collapse of the West Antarctic Ice Sheet and potentially result in 10 feet of global sea level rise.
We propose to study this potential “tipping point” of global sea level rise. In particular, we will develop scientific requirements for an observing system to monitor the ocean conditions near key outlet glaciers such as Pine Island and Thwaites, test hypotheses for relating ocean conditions to ice loss, and cultivate a new generation of sea level rise projections. Although many observational assets are already devoted to the Antarctic cryosphere, the ocean near Antarctica remains poorly sampled and long-term campaigns will be required in order to answer the fundamental questions that stymie present-day sea level projections. Given harsh conditions and remote locations, remote sensing techniques will likely play an important role along with more traditional in situ observing systems. Lessons learned from observational and numerical studies of particular outlet glaciers would be used to identify and better understand other regions of key ocean-ice interactions."

[AbruptSLR]

It appears to me that the movement to overhaul the IPCC climate change reporting process to make more frequent reports (compared to the current six to seven-year cycle); indicates that scientists understand that the climate is changing so quickly (including projections of higher SLR) that the IPCC needs to provide more updated policy recommendations before decision makers plan measures that will be overwhelmed when the actual change occurs (such as SLR exceeding 2m by 2100):


http://www.theguardian.com/environment/2013/sep/04/scientists-overhaul-un-climate-report-ipcc

[AbruptSLR]

The information at the following link about leaked IPCC AR5 WG1 SLR information closely matches the previously linked information cited earlier in this thread; and it is interesting to think that if the WG1 researchers can so casually changes their SLR projections from AR4 to AR5, then how much will they change their SLR projections from AR5 to their next official projection is released (hopefully more frequently than every 6 to 7 years, as discussed in the immediately preceeding post).  People using any such official WG1 SLR projections need to understand that all the GCM/RCM/LCM SLR projections were calibrated to paleo-climates that were all in equilibrium, while the conditions today are far from equilibrium, and thus there is no way that policy makers should take the AR5 SLR projections as authoritative scientific forecasts for planning purposes without reading all of the disclaimers in the AR5 report which essentially say: "All models are wrong, but some models are useful…" provided user understands the limits of the model:

http://www.bloomberg.com/news/2013-09-05/ice-melting-faster-in-greenland-and-antarctica-in-un-leak.html

[AbruptSLR]

The following two abstracts are taken from the proceedings of the following IGSOC sponsored symposia, and they are relevant to the need to communicate better guidance information related to SLR associated with ice mass loss including that from the AIS:

International Symposium on Changes in Glaciers and Ice Sheets: observations, modelling and environmental interactions; 28 July–2 August; Beijing, China; Contact: Secretary General, International Glaciological Society


http://www.igsoc.org/symposia/2013/beijing/proceedings/procsfiles/procabstracts_62.htm


Climate change: the physical science basis – some progresses of WG1 AR5 IPCC
Qin DAHE
Corresponding author: Qin Dahe
Corresponding author e-mail: qdh@cma.gov.cn
"The Intergovernmental Panel on Climate Change (IPCC) has been established by WMO and UNEP to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation. It is open to all members of the UN and of WMO. The IPCC Working Group I (WGI) assesses the physical scientific aspects of the climate system and climate change. At present, the IPCC has begun the government and expert review of the Working Group contributions, and preparations for the Fifth Assessment Report (AR5) are entering the final stage. Compared with previous reports, the AR5 will put greater emphasis on assessing the socio-economic aspects of climate change and the implications for sustainable development, risk management and the framing of a response through both adaptation and mitigation. Since the release of IPCC AR4, a number of questions on climate change sciences were left unresolved. For example, has climate change accelerated, is the Greenland ice sheet stable, will the Himalayan glacier have disappeared in 2035, what is the role of clouds and aerosols, is the carbon cycle feedback positive, will there be more disasters such as droughts, etc? AR5 will provide an update of knowledge on them. Ice sheets and sea-level rise is one of the key cross-cutting themes in AR5. In the WGI report, there are two chapters stating the progress in cryosphere and sea-level studies, i.e. the fourth chapter (Observations: Cryosphere) and the thirteenth chapter (Sea Level Change). Both the extensive thinning of margins and mass loss of ice sheets in Greenland and Antarctica are remarkable. Details will be introduced in the presentation."

Travelling the last mile: communicating cryospheric knowledge
Robert BINDSCHADLER
Corresponding author: Robert Bindschadler
Corresponding author e-mail: robert.a.bindschadler@nasa.gov
"There is no doubt within the cryospheric community that ‘our’ world, dominated by ice and low temperatures, is reacting strongly to increased warming of our planet. I address the challenges these physical changes pose for our scientific community. In a sense, we were caught with our pants down, equally astonished, as was the global audience, by the surprises of disintegrating ice shelves, accelerating outlet glaciers and shrinking land ice. We have responded by focusing on new areas of research and have been treated to impressively precise datasets that inform us about ongoing change. The excitement and, I’d like to think, the importance of what is happening to land ice across the globe has attracted new colleagues to share in our investigations, forming new collaborations and interdisciplinary teams. But are these changes enough? Are we simply recasting the science we do rather than transforming the landscape of what it means to be a ‘cryosopher’? Being thrust to the front and center of the climate change stage not only provides new attention and frequent headlines, but new responsibilities as well. What are these new responsibilities and how do we meet them?"

[sidd]

Calafat and Chambers. GRL, July 2013, doi:10.1002/grl.50731

Not only is sea level rise accelerating, the acceleration is increasing, i.e. the rate of increase of sea level is at least quadratic.

” … since 1973, SL accelerations have been increasing at a significant rate of 0.002 mm/yr^3 until reaching its present value of 0.022 ± 0.015 mm/yr^2 for the 60 year record centered around 1982.”

sidd

[AbruptSLR]

Sidd,

Thanks for the great reference.  I hope that the decision makers get the authors' concluding message that:

"Furthermore, we have found that the acceleration is increasing over time. This acceleration appears to be the result of increasing greenhouse gas concentrations, along with changes in volcanic forcing and tropospheric aerosol loading."

Indicating that not only is the rate of SLR accelerating, but also that the rate of acceleration is accelerating.

Best,
ASLR

[AbruptSLR]

The linked reference provides data from the GRACE satellite, that decision makers could to understand the current "fingerprint" effect on regional SLR from land-based water contributions to SLR, including those from the AIS:

http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20058/abstract

Land water contribution to sea level from GRACE and Jason-1 measurements
By: Jensen, L., Rietbroek, R., and Kusche, J., 2013. Land water contribution to sea level from GRACE and Jason-1 measurements. Journal of Geophysical Research (Oceans), 118:212–226, doi:10.1002/jgrc.20058

Abstract
"We investigate the effect of water storage changes in the world's major hydrological catchment basins on global and regional sea level change at seasonal and long-term time scales. In a joint inversion using GRACE and Jason-1 data, we estimate the time-dependent sea level contributions of 124 spatial patterns ("fingerprints") including glacier and ice sheet melting, thermal expansion, changes in the terrestrial hydrological cycle, and glacial isostatic adjustment. Particularly, for hydrological storage changes, we derive fingerprints of the 33 world's largest catchment basins, assuming mass distributions derived from the leading EOFs of total water storage in the WaterGap Global Hydrological Model (WGHM). From our inversion, we estimate a contribution of terrestrial hydrological cycle changes to global mean sea level of - 0.20 ± 0.04 mm/yr with an annual amplitude of 6.6 ± 0.5 mm for August 2002 to July 2009. Using only GRACE data in the inversion and comparing to hydrological changes derived from GRACE data directly using a basin averaging method shows a good agreement on a global scale, but considerable differences are found for individual catchment basins (up to 180%). Hydrological storage change estimates in 33 basins from the GRACE/Jason fingerprint inversion indicate a trend 46% smaller and an annual amplitude 43% bigger compared to WGHM-derived storage changes. Mapping the hydrological trends to regional sea level reveals the strongest sea level rise along the coastlines of South America (max 0.9 mm/yr) and West Africa (max 0.4 mm/yr), whereas around Alaska and Australia, we find the hydrological component of sea level falling (min -2.0 mm/yr and -0.9 mm/yr)."

[AbruptSLR]

The following linked reference provides data demonstrating the value of GRACE satellite data not only water mass loss from land (into the sea); but also the pattern of water mass accumulation on land (taking water from the sea):


http://link.springer.com/article/10.1007%2Fs00190-012-0583-2


Continental mass change from GRACE over 2002–2011 and its impact on sea level;
By: O. Baur, M. Kuhn,  & W. E. Featherstone; Journal of Geodesy; February 2013, Volume 87, Issue 2, pp 117-125



"Abstract
Present-day continental mass variation as observed by space gravimetry reveals secular mass decline and accumulation. Whereas the former contributes to sea-level rise, the latter results in sea-level fall. As such, consideration of mass accumulation (rather than focussing solely on mass loss) is important for reliable overall estimates of sea-level change. Using data from the Gravity Recovery And Climate Experiment satellite mission, we quantify mass-change trends in 19 continental areas that exhibit a dominant signal. The integrated mass change within these regions is representative of the variation over the whole land areas. During the integer 9-year period of May 2002 to April 2011, GIA-adjusted mass gain and mass loss in these areas contributed, on average, to −(0.7 ± 0.4) mm/year of sea-level fall and + (1.8 ± 0.2) mm/year of sea-level rise; the net effect was + (1.1 ± 0.6) mm/year. Ice melting over Greenland, Iceland, Svalbard, the Canadian Arctic archipelago, Antarctica, Alaska and Patagonia was responsible for + (1.4±0.2) mm/year of the total balance. Hence, land-water mass accumulation compensated about 20 % of the impact of ice-melt water influx to the oceans. In order to assess the impact of geocentre motion, we converted geocentre coordinates derived from satellite laser ranging (SLR) to degree-one geopotential coefficients. We found geocentre motion to introduce small biases to mass-change and sea-level change estimates; its overall effect is + (0.1 ± 0.1) mm/year. This value, however, should be taken with care owing to questionable reliability of secular trends in SLR-derived geocentre coordinates."

[AbruptSLR]

The following abstracts come from the linked sources and are relevant to Sea Level Rise Policy:

www.igsoc.org/symposia/2013/kansas/proceedings/procsfiles/procabstracts_63.htm
Contact: Secretary General, International Glaciological Society

67A028
Ice sheets and sea level – data, models and ways forward
Richard B. ALLEY, Sridhar ANANDAKRISHNAN, Byron R. PARIZEK, David POLLARD, Kiya L. RIVERMAN, Nicholas D. HOLSCHUH, Atsu MUTO, John M. FEGYVERESI, Nathan T. STEVENS, T. LUTHRA, D.E. VOIGT, P.G. BURKETT, K. CHRISTIANSON, J.P. WINBERRY
Corresponding author: Richard B. Alley
Corresponding author e-mail: rba6@psu.edu
The ‘unknown unknowns’ of ice-sheet behavior have been shrinking rapidly under the coordinated efforts of surface observations, airborne and satellite remote sensing, and modeling, together with atmospheric, oceanic and geologic investigations around the ice sheets, including paleoclimatic studies. For most ice-sheet regions, it is now possible to place useful limits on likely rates of change, quantify uncertainties and define research plans for reducing those uncertainties. Unfortunately, this optimistic outlook does not apply universally. Sufficient retreat of the Thwaites Glacier grounding zone, for example, could shift a calving front into a region of combined width and water depth larger than any outlet on Earth today, raising physical questions that are not as yet close to being answered and that may prove very difficult to constrain tightly. The community faces the challenge of continuing the highly successful work of reducing uncertainties in well-characterized flow regimes, while identifying and characterizing those physical processes that are not yet well represented in key places. Furthermore, policy-makers would like guidance from plausible scenarios until those physical processes are better represented. The need for coordinated observations and modeling is thus growing, not shrinking.

[AbruptSLR]

Regarding my immediately preceeding post about Alley et al 2013 (IGSOC 67A028); I agree with those authors that the rate of learning about ice sheets and sea level has accelerated sharply in the past few years; and I strongly agree that our learning about the risks posed by the Thwaites Glacier has a long ways to go before policy makers can rely on model projections in this area (see my posts today in both the "PIG/Thwaites 2012 -2060" and the "Glaciology" threads).  However, I disagree that policy makers should feel so secure in the current generation of ice mass loss/balance model projections that they should not be concerned about potentially abrupt ice mass loss from all areas of the WAIS and from the coastal areas of the EAIS. 

I believe that we should expect SLR guidance to continue to rachet upwards every few years, until at least 2050 (and possibly 2100) as researchers learns more and more about the "unknown unknowns" that society faces with regard to: radiative forcing, climate sensitivity, and dynamic ice mass loss.

Hopefully, the hard work, and intermediate results, of sound researchers such as Alley et al 2013 will encourage policy makers to provide sufficient funding to allow researchers to converge on more sustainable projections before we cross an Earth System tipping point.

[AbruptSLR]

Attached I have provided a copy of the enabling legislation for the Biggert-Waters Flood Insurance Act of 2012; which allows the US Federal government to transfer the costs and much of the risks of future SLR to the individual flood insurance policy holders in the USA.  It should be noted that the new FEMA (Federal Emergency Management Agency) Flood Insurance Rate Maps (FIRMs) do not include the influence of future SLR, but they are free to revise their FIRMs whenever they like, and according to the Biggert-Waters Act the insurance companies can start to advance charge in their flood insurance premiums for whatever amount of consequences that they can convince the federal government is reasonable.

Also, note that in the following definitions from the Biggert-Waters Act of of the categories of floodplain risks uses both a 1% and an 0.2% annual exceedance probability in any give year; which is the criteria the FEMA uses for creating their FIRMS:

"(1) 100-YEAR FLOODPLAIN.—The term ‘‘100-year floodplain’’  means that area which is subject to inundation from a flood having a 1-percent chance of being equaled or exceeded in any given year.
(2) 500-YEAR FLOODPLAIN.—The term ‘‘500-year floodplain’’ means that area which is subject to inundation from a flood having a 0.2-percent chance of being equaled or exceeded in any given year."

Now what I want to emphasize for these "floodplain" definitions is that they are for "... any given year."  Which means that in the future when SLR occurs all of the FIRMS will change, all of the insurance premiums will be increased (for all policy holders, but with a sliding scale increase for those in the high risk floodplains).  Therefore, in the USA (and similarly elsewhere in the world) it is the individual asset holders who will need to bear the costs and risks associated with future SLR (note that the Biggert-Waters Act allows for a reduction in flood insurance premiums is the asset holders have improved flood defense systems).

[AbruptSLR]

Further to my immediately preceeding post, I would like to make the following points:

- The insurance companies typically only increase their flood insurance premiums on a given policy every roughly five years, therefore, within reason they do not care what long-term SLR guidance that FEMA recognizes, provided they can cover up to five years of possible losses not already covered by premiums.
- All SLR guidance authorities are free to increase their SLR projections anytime that they feel appropriate (as NOAA did in December of 2012 and the IPCC will do in September 2013); thus any possible increases in risk for SLR not covered by current guidance will need to be covered by the asset holders (with a minor five year window of exposure to insurance companies).
- Civil works flood protection measures can that 20 to 50-years to plan, permit and construct; thus asset holders will need to start taking active flood defense measures well before 2050 when the risk of increase in SLR from the WAIS become significant.

In future posts I plan to address how a SLR hazard assessment can be used to develop a Maximum Credible SLR Scenario, MCSS, that can be used in combination with the 0.2% annual exceedance probability storm surge event, in order to help make decisions about what are appropriate measures to take for low probability flood inundation defense measures.

[AbruptSLR]

The authors of the following reference take the large uncertainties in WAIS ice-mass change over the past six years as reason to be scientifically conservative w.r.t. SLR projections; while I believe that these large uncertainties is a reason to be conservative with public safety w.r.t. to the risk of inundation:

Ice-sheet mass balance and climate change. by: Hanna E, Navarro FJ, Pattyn F, Domingues CM, Fettweis X, Ivins ER, Nicholls RJ, Ritz C, Smith B, Tulaczyk S, Whitehouse PL, Zwally HJ. Nature. 2013 Jun 6;498(7452):51-9. doi: 10.1038/nature12238.

"Abstract
Since the 2007 Intergovernmental Panel on Climate Change Fourth Assessment Report, new observations of ice-sheet mass balance and improved computer simulations of ice-sheet response to continuing climate change have been published. Whereas Greenland is losing ice mass at an increasing pace, current Antarctic ice loss is likely to be less than some recently published estimates. It remains unclear whether East Antarctica has been gaining or losing ice mass over the past 20 years, and uncertainties in ice-mass change for West Antarctica and the Antarctic Peninsula remain large. We discuss the past six years of progress and examine the key problems that remain."

[AbruptSLR]

The following link leads to an article discussing the type of politicing (cherry picking) that SLR guidance is subjected to in the IPCC process.  We will not know whether cherrry-picked SLR guidance values come-out of the IPCC until towards the end of September 2013; but either way the question of ASLR will likely not be covered by SLR guidance values until after 2050:


http://www.nytimes.com/2013/09/10/science/a-climate-alarm-too-muted-for-some.html?ref=science&_r=3&

[sidd]

 quote from the IGSOC abstract from Alley et al.

"Sufficient retreat of the Thwaites Glacier grounding zone, for example, could shift a calving front into a region of combined width and water depth larger than any outlet on Earth today, raising physical questions that are not as yet close to being answered and that may prove very difficult to constrain tightly."

He's scared. Pollard is on that author list also.

I'm scared, too.

[AbruptSLR]

Sidd,

It does seem that for may years most researchers assumed that WAIS (and some EAIS) ice streams/glaciers were as stable as those in Greenland; and now the more we learn (as the Antarctic is a tough place to obtain data), the clearer it is that this is not the case.  While the leading edge researchers (possibly now including Pollard) are increasingly understanding the true risks (consequence times probability); most SLR guidance bodies (particularly including the IPCC) are as much policitical bodies as they are scientific bodies; which makes it easy for the majority to treat the findings of the scientists on the leading edge of research as "outiers" that should be ignored when formulating policy.

Therefore, while I am obviously quite concerned about the ASLR risk that we are facing; I have my doubts that policy makers will be prepared to deal constructively with this risk until after the grounding zone for at least the Thwaites/PIG basin has retreated into an unstable configuration; as I believe that this could happen in the next few decades rather than in the next few centuries as the policy makers appear to believe.

Best,
ASLR

[AbruptSLR]

The following article presents some of the types of topics being discussed in the IPCC SLR sessions:


Climate science: Rising tide - Researchers struggle to project how fast, how high and how far the oceans will rise; Nicola Jones; Nature; 501, 301–302 (19 September 2013) doi:10.1038/501300a

http://www.nature.com/news/climate-science-rising-tide-1.13749

[AbruptSLR]

Getting back to Sidd's point that Alley seems very concerned about the short-term stability of the Thwaites Glacier, toward the end of this YouTube video (from the June 2013 Chapman Conference) explicitly says that his co-researchers have input the range of uncertain values for parameters controlling the stability of the Thwaites Glacier into their model; and that they found that at the low end of these values Thwaites was stable for several thousand years; while of the high end of these values Thwaites is very unstable:

[AbruptSLR]

Least readers think that there is only a very small chance that Alley, et al's finding that at the upper end of the uncertainty values for the input parameters for their model of the Thwaites Glacier, means that the glacier maybe very unstable, please consider the following:

- In the view Alley laments that there is currently a very poor understanding of the human input into radiative forcing.  Thus if RCP 2 thru 6 turn-out to be nothing more than wishful thinking on the part of both the alarmists and the denalists; then the probability that the upper values will occur increase by multiple times.

- All glacier models today (including Alley et al's) are incomplete and also are blind to abrupt changes; which means that anyone relying on Alley et al's findings must also accept responsibility for the risk that this model does not adequately account for possibly greater instability mechanisms from: (a) increasing surface crevasses as the glacier thins (as happened locally in 2012 when the Thwaites Ice Tongue surged and thinned the input ice); (b) synergy between the PIG and Thwaites with regard to: (i) horizontal advection of warm CDW from PIIS to the Thwaites Ice Tongue trough; and (ii) as the PIG SW tributary glacier activates the eastern shear margin of Thwaites and also relieves ice flow into the Thwaites Gateway, thus allowing the ice flow velocities in the gateway to accelerate (due to lack of congestion); (c) basal melting may increase faster than the model assumes due to increased geothermal heat as glacial thinning induces magma to flow-in beneath the BSB (as supported by the physical iGPS measurements in this area) and the risk that higher than modeled ice velocities will increase friction induced basal melting; (d) that surface melting and possible surface rainfall after 2050 may markedly accelerate ice mass loss; (e) the subglacial hydrological system beneath Thwaites may contribute to more ice flow than currently expected; and (f) external factors such as tides, storm surge, waves, finger print slr locally as the GIS melts; local increase in onshore winds as the ABSL increasingly positive trend continues and is periodically jump-started when the El Nino hiatus ends.

- The risks that: (a) the fast climate sensitivity is greater than assumed by GCMs due to the faster accumulation of atmospheric humidity than previously projected; (b) the slow climate sensitivity feedback factors (such as Arctic albedo, etc) will occur faster than previously projected; and (c) the risk that a flip to an equable climate (before 2100) may occur more easily (say due to increasing El Nino's and tropical cyclone migration into the Arctic) than previously expected.

- The probability that the forcing models used by Alley et al, do not account fully for the persistence of the Antarctic ozone hole, nor the rapid accumulation of methane over Antarctica; which should accelerate circumpolar winds and thus should drive the ACC further south than expected, resulting in more contact between the warm CDW and ice shelves (including those for both PIG and Thwaites).

- The fact that the AABW is not draining out of the Southern Ocean as fast nor as cold as previously projected, implies both that the warm CDW will warm faster than expected and that the cross-shelf currently will occur with more velocities and volume than previously expected.

[AbruptSLR]

Rahmstorf provides a very nice discussion of the AR5 SLR projections at the following website

http://www.realclimate.org/index.php/archives/2013/09/the-new-ipcc-climate-report/

Which contains the attached image of those AR5 SLR projections

I also note that on page 18 of the IPCC AR5 Summary statement is a significant prognosis:

"It is virtually certain that near-surface permafrost extent at high northern latitudes will be reduced as global mean surface temperature increases. By the end of the 21st century, the area of permafrost near the surface (upper 3.5 m) is projected to decrease by between 37% (RCP2.6) to 81% (RCP8.5) for the model average (medium confidence)."

This should remind all readers that all of the RCP scenarios significantly under estimate GHG contribution from the permafrost over the coming century.

[Lennart van der Linde]

As mentioned by Rahmstorf in the comments, IPCC estimates a 17% chance of more than 98 cm of SLR by 2100 (relative to 1986-2005) for RCP 8.5; their worst-case then seems to be about 1.5-1.7m, although they also mention the almost 2m of the semi-empirical models (but they have no consensus on the usefulness of those models). Hansen still thinks multi-meter SLR is likely at 2100 with BAU.

[AbruptSLR]

Lennart,

Thanks for the details on different opinions on possible ranges of SLR by 2100.

Given that the numerous positive feedback factors to global warming, result in non-linear responses in SLR; it seems to me that the SLR issue is like a diagnosis of cancer, where earlier intervention can result in a good prognosis, but where delayed intervention can result very adverse results, and that relying on uncertainty as a defensive posture is a very poor idea.  I completely side with Hansen on this matter.

Best,
ASLR

[sidd]

i watch for portents
1)saddle collapse a la Gregoire on GIS at 67N
2)NEGIS acceleration over some of the deepest icebeds on earth
3)PIG-Thwaites acceleration
4))EAIS, which has too many oulets bedded too deep

Do not see how we avoid 1m from GIS+AIS by 2100. I fear I am optimistic. I fear Eemian style collapse, an i fear that I am seeing the beginning already.

sidd

[Lennart van der Linde]

ASLR,
I also think we should take Hansen seriously. I'm trying to find out why the Dutch Environmental Assessment Agency thinks 1.5m by 2100 is the worst-case scenario. And why they apparently think that 1.5 meter/century is the worst-case even for the centuries after 2100.

I'm also trying to find out what they think of a plan by two retired engineers to protect our country from many meters of SLR by building a large dyke in front of our coast:
http://haaksezeedijk.1holland.eu/index.php/presentaties.html

If you have any comments at first sight, without knowing the details of their plan, I'm very interested in hearing them.

[AbruptSLR]

Sidd,

I agree that there are multiple trigger points that will make varying degrees of contributions to SLR at different rates; and that there can be feedback mechanisms that can accelerate these rates.  Hopefully, we will be able to make more accurate models before it is to late to react.

Lennart,

As I do not speak/read Dutch I cannot make specific comments about the proposal that you linked to; however, I can say that in New Orleans the storm surge barrier system has been designed to resist over 7 m of storm surge.  Thus, I would say that The Netherlands can design/construct a comparable system on a somewhat larger scale, given sufficient determination.

Best,
ASLR

[Lennart van der Linde]

ASLR,
I'm glad the pictures were clear enough to make this statement at first sight. That's all I needed to hear for now

Thanks and best.

[AbruptSLR]

For those who want to read AR5 Chapter 4 on the Cryosphere (including Antarctica), you can find a pdf at the following link:

http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_Chapter04.pdf

[AbruptSLR]

I realize that some readers would like links to other key AR5 chapters, so here they are:

http://www.climatechange2013.org/report/review-drafts/

and to the SLR Chapter 13 (and related Appendix):

http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_Chapter13.pdf

http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_AnnexII.pdf

[AbruptSLR]

According to the article in the following link, the current US Federal Government shut-down could close the US Antarctic research facilities; which would limit our ability for develop more accurate future SLR guidelines:

http://thinkprogress.org/climate/2013/10/07/2745681/antarctic-research-threatened-by-shutdown/

[werther]

I'm also trying to find out what they think of a plan by two retired engineers to protect our country from many meters of SLR by building a large dyke in front of our coast:
http://haaksezeedijk.1holland.eu/index.php/presentaties.html

Lennart, hi,
I remember the presentation by KNMI of four local climate scenarios back in '06. An engineer from Rijkswaterstaat (the State Engineering Bureau) suggested the coastline could be kept safe for centuries by adding sand (a much related project). I asked him, rather cryptic, with what energy he supposed we could do that?
I had the impression he never even considered that.
It is a BAU scenario, Lennart. It is unsustainable. Eventually, people will have to move.

[AbruptSLR]

All,

First, I agree that dykes are only a temporary safeguard against SLR, but even if they only save 50-years of relative safety they may be a worthwhile investment, as they might buy some time for mankind to over-come its fossil fuel addiction.

Second, I will be on vacation until Oct 21st.

Best,
ASLR