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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #100 on: June 01, 2014, 01:15:39 PM »
SH,

Thanks, sometimes it is difficult to know how much background to provide, or not.

For instance, at the following website, Aslak Grinsted, points out that in regards to sea level rise section of  the Summary for Policy Makers, SPM, of Assessment Report 5, AR5:

"The explanation is that the true uncertainty is considered to be greater than the model spread.
The supplementary material to the sea level chapter says that they follow section 12.4.1.2 when they use 5-95% as the likely range.

[EDIT: I just found an explanation in an SPM footnote: "Calculated from projections as 5−95% model ranges. These ranges are then assessed to be likely ranges after accounting for additional uncertainties or different levels of confidence in models. For projections of global mean sea level rise confidence is medium for both time horizons."]"

http://www.glaciology.net/Home/Miscellaneous-Debris/whatdoeslikelymean


Also, at the following link, Aslak Grinsted provides the accompanying figure with the following Legend


http://www.glaciology.net/Home/Miscellaneous-Debris/comparisonofsealevelprojections


Legend:
"•  Extrap: constant rate of sea level rise at present day trend from sealevel.colorado.edu. (An absolute lower limit of plausibility IMO)
• FAR: full range of SLR projections from FAR (taken from SAR table 7.8)
•  SAR: full range of SLR projections from SAR (taken from TAR table 11.14). (SARp369: "Excluding the possibility of collapse of the West Antarctic ice sheet").
•  TAR: full range of SLR projections from TAR table 11.14. (TAR p.642: "The range of projections given above makes no allowance for icedynamic instability of the WAIS".)
•  AR4: SLR projection excluding scaled-up ice sheet discharge. (AR4 WG1 Table 10.7).
•   AR4+: SLR projection including scaled-up ice sheet discharge. (AR4 WG1 Table 10.7). Context for "larger values cannot be excluded" can be found in the AR4 SPM.
•  SEM: full range of semi-empirical projections in AR5 (from AR5 fig.13.12).
•  AR5: "process based" ice sheet projections from AR5 table 13.5. These do not account for a potential collapse of Antarctic marine based sectors which may contribute up to several decimetres (indicated with thin shaded line).
•  Ice sheet experts*. refers to Bamber and Aspinall (2013) table S1 5-95% plus non ice sheet contributions from AR5 table 13.5. Note BA13 does not refer to a specific scenario (hence the asterisk)
•  SLR experts refers to the expert elicitation of Horton et al. 2013 (table 1). They do not provide RCP45 but only RCP85 and RCP3PD. However both SEMs and AR5 agree that the projection for RCP45 lies at about a third of the way between. So I have used this weighing. "



Furthermore, in the link at the end of this post, Aslak Grinsted goes on to say:

"…. To appreciate why 0.98 m is not an upper limit of SLR then you have to read on and understand the caveats stated in the AR5. The SPM also says:

"
The basis for higher projections of global mean sea level rise in the 21st century has been
considered and it has been concluded that there is currently insufficient evidence to evaluate
the probability of specific levels above the assessed likely range.
"

To parse this you need to understand the IPCC jargon. "Likely" means the 66% confidence interval. I.e. slightly less than a one sigma interval. So, the full uncertainties are at least twice as large but they are unwilling to say by how much exactly. They also say that there is an additional uncertainty that is unlikely to be anything but positive:

"Based on current understanding, only the collapse of marine-based sectors of the Antarctic ice sheet, if initiated, could cause global mean sea level to rise substantially above the likely range during the 21st century. However, there is medium confidence that this additional contribution would not exceed several tenths of a meter of sea level rise during the 21st century. {13.4, 13.5}"

It is unclear what they mean by "several tenths of a meter". I find it remarkable that they could not agree on a more quantitative statement considering they are only stating something with "medium confidence". In any case this excluded potential contribution is clearly positive. This uncertainty strongly affects the upper tail of the uncertainty range. It is effectively a bias. Ice sheet experts appear to judge this collapse scenario quite probable, and post-AR5 modelling indicates that Pine Island Glacier in Antarctica is already engaged in an unstable retreat (Favier et al., 2014).

The literal meaning of the AR5 likely range is that there is 17% chance of exceeding 1m SLR assuming that there is no marine instability (under RCP8.5). If there is an instability then the probability is greater."

http://www.glaciology.net/Home/Miscellaneous-Debris/ar5sealevelriseuncertaintycommunicationfailure

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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #101 on: June 01, 2014, 01:47:58 PM »
In February 2002, the then U.S. defense secretary Donald Rumsfeld said: "There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – there are things we do not know we don't know."

While I am on a roll about providing background information, I will make a few more comments about uncertainties with regard to abrupt climate change, ACC.

For example, when generating Recommended Concentration Pathway, RCP, 8.5 (the highest Confidence Level, CL, family of scenarios) the IPCC calibrated this family of scenarios to match the 90th percentile of model projection published by 2007, and thus does not consider any new findings.  In this regard it is important to remember that GCM CL only address the uncertainties within the input variables, and not within such other vital factors as: (1) completeness of input scenarios, (2) model sensitivity/accuracy, and (3) calibration of models to actual climate sensitivities.  To elaborate on these three particular factors:

1.   The recent economic development of alternate fossil fuels such as shale gas and tar sands means that sufficient economically recoverable carbon-based fuels exist to continue following RCP 8.5 - 95% CL scenario to a 6oC global-mean temperature rise, by 2100, unless modern society makes extensive efforts to get off the concentration pathway that it has been following for over 30-years.  Of particular concern is the fact that many countries around the world have made commitments to develop large quantities of shale gas (most notably the EU following the Ukraine Crisis); which unless carefully regulated can make more radiative contributions to AGW than burning coal.
2.   No Global Circulation Model/Earth System Model (GCM/ESM) has sufficient accuracy, or sensitivity to accurately project any aspect of Abrupt Climate Change, ACC.  Therefore, if decision makers are expecting to receive early warning of ACC from the billions of dollars-worth of GCM/ESM projections, then they are likely to be as surprised.  It is noted that assessments of GCM/ESM projection indicate that the chain of positive feedback associated with the change in albedo associated with the loss of summer snow extent and polar sea ice area can temporarily change climate sensitivity from an effective current value of approximately 3oC to over 6 oC (when considering ESS, see the first attached image, from Hansen and Sato).
3.   Independent assessments (Hammitt and Shlyakhter, 1999) of the external uncertainty associated with projection methodologies such as those used by the IPCC indicate that in many applications, 20 % to 45% of actual results fall outside the previously assumed 98% confidence levels.  Thus policy makers should not be surprised if ACC probabilities of occurrence are actually 10 to 22.5 times more likely to occur than as reported by the AR5 (or AR4).

Furthermore, since the RCP scenarios were developed, subsequent research regarding fast climate response functions (see Rogelj et al. 2012, Henriksson et al. 2010, Annan and Hargreaves 2009, and Baker and Roe 2009) indicate that the expected mean temperature increase for RCP 8.5 now exceeds that projected for SRES A1FI (see the second attached image from Rogelj et al 2012).


"The dogmas of the quiet past are inadequate to the stormy present. The occasion is piled high with difficulty, and we must rise with the occasion. As our case is new, so we must think anew and act anew." President Abraham Lincoln

Selected References:

J.K. Hammitt and A.I. Shlyakhter, “The Expected Value of Information and the Probability of Surprise,” Risk Analysis 19(1): 135-152, 1999.

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.

Rogelj, J., Meinshausen, M. and Knutti, R., (2012), "Global warming under old and new scenarios using IPCC climate sensitivity range estimates", Nature Climate Change - Letters, doi: 10.1038/NCLIMATE1385.
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Shared Humanity

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #102 on: June 01, 2014, 03:34:53 PM »
ASLR.....

I can only speak for myself but I find some background on a post that explores a specific issue is invaluable. It does not need to be extensive (a small part of the post is fine) and including links that explain the background further is fantastic.

I am trying to catch up with people here. Background helps.

Shared Humanity

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #103 on: June 01, 2014, 03:41:06 PM »
With regards to your explanation of sea level rise projections, it would not surprise me if the curve of these projections had a pronounced kurtosis. In fact, I would be shocked if this were not the case. The low end would be defined by the most recent slr contributions. No model would predict any possibility of a decline. Meanwhile, many models would likely have some possibility of substantial increases in the rate of slr.

AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #104 on: June 01, 2014, 06:38:35 PM »
For those not so familiar with probability theory, I offer the following two definitions related to the shape of a Probability Density Function, PDF:

"Skewness is a measure of symmetry, or more precisely, the lack of symmetry. A distribution, or data set, is symmetric if it looks the same to the left and right of the center point.

Kurtosis is a measure of whether the data are peaked or flat relative to a normal distribution. That is, data sets with high kurtosis tend to have a distinct peak near the mean, decline rather rapidly, and have heavy tails. Data sets with low kurtosis tend to have a flat top near the mean rather than a sharp peak. A uniform distribution would be the extreme case."

So if one were to use the Horton expert survey (see Replies #52 and #60) for the 83rd percentile for the RCP 8.5 scenario as an approximation of a SLR PDF, then you have both a relatively high degree of kurtosis and of skewness.  However, as the expert's models improve, and they are willing to acknowledge more future SLR, one can expect the peak of the PDF to shift to the right (see for example the following link that indicates that 97% of climate change researchers believe that the AR5 SLR projections are too low; which implies to me that AR6 will have higher projections than AR5, just a AR5 had about 50% higher SLR projections than AR4; because the IPCC process is slow to acknowledge the most recent research):


http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/feb/18/scientists-worried-ipcc-underestimate-sea-level-rise

« Last Edit: June 01, 2014, 06:50:38 PM by AbruptSLR »
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #105 on: June 01, 2014, 06:57:20 PM »
I would also like to point out that all measurements of Black Carbon, BC, in the environment are currently considerably higher than that assumed in RCP 8.5 (see the "Forcing" thread in the Antarctic folder), and I am concerned that the following reference by Marin-Spiotta et al 2014 indicates that during marked climate change in the early Holocene, wildfires were very widespread (& they are becoming increasingly common now with AGW); which may indicate that more future wildfires will lead to more BC, and more albedo loss (particularly in the Arctic & tundra); which in-turn should drive the ESS value higher:

Marín-Spiotta, E., N.T. Chaopricha, A.F. Plante, A.F. Diefendorf, C.W. Müller, S. Grandy, and J.A. Mason. Long-term stabilization of deep soil carbon by fire and burial during early Holocene climate change. Nature Geoscience

http://www.nature.com/ngeo/journal/vaop/ncurrent/pdf/ngeo2169.pdf
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #106 on: June 01, 2014, 09:35:52 PM »
While I am reviewing factors that could accelerate SLR, I would like to remind readers that no AR5 GCM projection included methane contribution from the expected degradation of the permafrost, see the first attached image of the projected permafrost carbon flux (atmospheric emission in billions of short tons per year) from the permafrost with time [from: NOAA and the National Snow and Ice Data Center (NSIDC), 2011.  This image indicates that there will be strong carbon flux (about 2.5% of which is expected to be methane) from permafrost decomposition before the end of the century. 
The second attached image shows the ratio of GHG equivalent of gas to coal vs methane emissions as a share of gas production and the assumed methane global warming potential, from IEA 2012.  Howarth et. al. 2012 indicates that new sources of shale gas, tight gas, and coal-bed methane normally have emissions of about 6%, with a 100-year GWP of 34 and a 20-year GWP of 105; which indicates that new sources of unconventional gases could induce radiative forcing from as much as that induced by new coal sources to as much as over 1.5 times that induced by new coal sources (see the second attached image), over a 20-year period.

This information indicates that methane's contribution to global warming will be accelerating until the end of the century and that current AR5 projections do not address this contribution.  Furthermore, methane hydrates are extensively discussed in other portions of this Forum (see the "Forcing" thread in the Antarctic folder); which represents a very real risk that increases rapidly after 2100.

Selected References:
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
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jai mitchell

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #107 on: June 02, 2014, 01:18:24 AM »
I think that you are touching on some serious deficiencies with the IPCC AR5.  I have pointed out these on several occasions here and elsewhere.

Not only do they use a nominal ECS of 3.0 Their entire basis for the ECS value is that Arctic sea ice will trend its' loss with CO2-equivalent atmospheric abundances.  In other words, a gradual decline in the models until it is gone in late September sometime in the year 2065.  Skeptical science did a good job showing that this was an obscene oversight by the IPCC.

In this simple statement:  The arctic sea ice will be summer ice-free several decades before the current IPCC models. Then we know that the non-linear temperature change in the arctic that will occur after this happens will necessarily push the ECS value above 4.0 and likely to 4.5.

It is this kind of reasoning that shows why Hansen has a curve that projects a 5 meter sea level rise by 2100. 



In this graph he shows that the exponential result of positive feedbacks (both in deep ocean temperature increases and in WAIS melt dynamics, as well as regional Greenland ablation results from summer arctic sea ice being gone by June 21 2035, will create these exponential increases.

The basis for his understanding of these things is the simple fact that the rate of energy deposition into the earth (mostly into the ocean) is increasing at an exponential rate (Top of Atmospheric Energy imbalance) because the earth's temperature is not able to keep up with the increased forcing from greenhouse gasses.

To this end, the Rignot failure to include multiple ocean heat content dynamics (i.e. a doubling of volume and a tripling of injection temperature into the WAIS regression line melt from the Circumpolar Deep Water pool by 2060) necessarily underestimates projected sea level rise by up to one order of magnitude (total WAIS contribution by 2100 of 40 cm vs potential 400 cm.)

Surely we must realize that the current rate of Antarctic melt is responding to emissions levels that were generated two decades ago.  Therefore, in the following scenario, the Hansen & Soto melt rate makes much more sense:



http://oi57.tinypic.com/b4gwn8.jpg
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #108 on: June 02, 2014, 12:25:04 PM »
jai,

As the January 2013 Fairfax SLR projection of over 11m circa 2075 seems to me to be erring on the side of most drama, I provide the attached figure from Hansen & Sato 2012 (see Figure 7 from the linked reference with a free access pdf), indicating 5m by 2100.

http://www.columbia.edu/~jeh1/mailings/2012/20121226_GreenlandIceSheetUpdate.pdf

Obviously, both numbers are relatively high; and the multi-meter difference illustrates how sensitive non-linear functions are, and emphasizes the need to calibrate, and to re-calibrate, them using the best information available.

Best,
ASLR
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #109 on: June 02, 2014, 02:55:17 PM »
Clearly the attached GIS ice mass loss per the GRACE satellite through 2013, indicates that this trend is non-linear; however, once the marine-terminating glacier's ice mass loss slows-down, will the shape of the trend line change to something more dominated by surface ice mass loss?

http://www.arctic.noaa.gov/reportcard/greenland_ice_sheet.html
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #110 on: June 02, 2014, 03:20:30 PM »
Talking about trends in SLR contributions, per AR5 the SLR contribution from glaciers is currently slowing-down (see the first attached image, with the caption for Figure 1 below, from AR5), while the SLR contribution from both the GIS and the AIS is accelerating (see the second attached image, Figure 2, also from AR5), resulting in the linear sea level rise trend line over this period:

Caption for Figure 1: Recent trends in glacier mass loss during (a) 1850-2010 and (b) 1961-2010. Coloured lines indicate different models, shaded areas show uncertainty. Blue bars display number of measured mass balance glaciers (IPCC, 2013).

Caption for Figure 2: Contribution of global glaciers (red), Greendland (green) and Antarctica (blue) to sea level rise between 1992-2012. Positive correlation between cumulative ice mass loss and sea level equivalent, shaded areas indicate uncertainty.

see also:

https://www.ccin.ca/home/ccw/glaciers/current

Also consider that an Atmospheric River event contributed to ice mass gain in the EAIS circa 2011, which temporarily served to mask the rate of acceleration of ice mass loss from the WAIS, as it is generally lumped together with the EAIS and reported as the AIS by the IPCC.
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #111 on: June 02, 2014, 03:27:34 PM »
For those not familiar with the Jakobshavn Effect, you can see it in dramatic action (in near real time) at the following link to the Greenland folder:

http://forum.arctic-sea-ice.net/index.php/topic,154.200.html#lastPost

Note that in a few decades time the Thwaites Glacier is likely to be subject to the same type of behavior as the Jakoshavn Glacier is exhibiting today.
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Re: Sea Level Rise and Social Cost of Carbon
« Reply #112 on: June 02, 2014, 04:50:26 PM »
Aaacckkkkk! Not kurtosis, skewness.  :o

jai mitchell

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #113 on: June 02, 2014, 05:09:29 PM »
ASLR

Thanks for posting the real Hanson Graphic, that is the one I was looking for.  Didn't realize that the one I was posting was an adaption to it, now that you posted it I can see that their curve significantly steeper!
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Re: Sea Level Rise and Social Cost of Carbon
« Reply #114 on: June 08, 2014, 09:37:14 PM »
What a single American city is facing.....a $1 billion price tag to protect themselves from  1 foot sea level rise.

http://www.washingtonpost.com/business/economy/in-norfolk-evidence-of-climate-change-is-in-the-streets-at-high-tide/2014/05/31/fe3ae860-e71f-11e3-8f90-73e071f3d637_story.html

AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #115 on: June 09, 2014, 05:35:57 AM »
Given the very high amount of calving currently going on at Greenland's Jakobshavn glacier (see the following link)

http://forum.arctic-sea-ice.net/index.php/topic,154.200.html

I believe that it appropriate to attached the following figure from Rahmstorf, Perrett and Vermeer (2011), in which the authors indicate with the red wedged lines the portion of ice sheet mass loss contribution to SLR that they feel are addressed by their semi-empirical model (see the following reference).  I note that most of the SLR contribution within the red wedged line area come from Greenland marine glaciers such as Jakobshavn glacier.

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.

Thus I expect to see accelerating contributions to SLR from the GIS for at least the next 10 to 25 years; which I believe will serve to help destabilize several WAIS marine glaciers, resulting in the WAIS making the worlds largest SLR contributions after about 2035 to 2040.
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #116 on: June 09, 2014, 11:41:30 AM »
Regarding my last post about ice mass loss from Greenland's Jakobshavn glacier, I provide the following linked reference with a free access pdf (by Hughes et al 2014) comparing the Jakobshavn Effect for both the Jakobshavn (GIS) and Byrd (EAIS) glaciers.  This paper provides the two attached images related to the Jakobshaven glacier; which indicate that if the calving face retreats another 7 to 10km then it will have retreated past a bottom pinning point, and would thereafter be free to retreat many kilometers:

Hughes, T., Sargent, A., Fastook, J., Purdon, K., Li, J., Yan, J.-B., and Gogineni, S.: Quantifying the Jakobshavn Effect: Jakobshavn Isbrae, Greenland, compared to Byrd Glacier, Antarctica, The Cryosphere Discuss., 8, 2043-2118, doi:10.5194/tcd-8-2043-2014, 2014.

http://www.the-cryosphere-discuss.net/8/2043/2014/tcd-8-2043-2014.pdf

"Abstract. The Jakobshavn Effect is a series of positive feedback mechanisms that was first observed on Jakobshavn Isbrae, which drains the west-central part of the Greenland Ice Sheet and enters Jakobshavn Isfjord at 69°10'. These mechanisms fall into two categories, reductions of ice-bed coupling beneath an ice stream due to surface meltwater reaching the bed, and reductions in ice-shelf buttressing beyond an ice stream due to disintegration of a laterally confined and locally pinned ice shelf. These uncoupling and unbuttressing mechanisms have recently taken place for Byrd Glacier in Antarctica and Jakobshavn Isbrae in Greenland, respectively. For Byrd Glacier, no surface meltwater reaches the bed. That water is supplied by drainage of two large subglacial lakes where East Antarctic ice converges strongly on Byrd Glacier. Results from modeling both mechanisms are presented here. We find that the Jakobshavn Effect is not active for Byrd Glacier, but is active for Jakobshavn Isbrae, at least for now. Our treatment is holistic in the sense it provides continuity from sheet flow to stream flow to shelf flow. It relies primarily on a force balance, so our results cannot be used to predict long-term behavior of these ice streams. The treatment uses geometrical representations of gravitational and resisting forces that provide a visual understanding of these forces, without involving partial differential equations and continuum mechanics. The Jakobshavn Effect was proposed to facilitate terminations of glaciation cycles during the Quaternary Ice Age by collapsing marine parts of ice sheets. This is unlikely for the Antarctic and Greenland ice sheets, based on our results for Byrd Glacier and Jakobshavn Isbrae, without drastic climate warming in high polar latitudes. Warming would affect other Antarctic ice streams already weakly buttressed or unbuttressed by an ice shelf. Ross Ice Shelf would still protect Byrd Glacier."
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #117 on: June 09, 2014, 11:54:20 AM »
In regards to my last post about the Jakobshavn glacier possibly retreating past its pinning point (note that some researchers have shown numerically that surface meltwater entering crevasses near the calving face of Jakobshavn would be sufficient to get the calving point to retreat upstream of the pinning point), I provide the following link to a NASA YouTube video focused on Rignot et al's 2014 work on six Amundsen Sea Embayment marine glaciers; which notes that most of the grounding lines for these glaciers have already retreated past their pinning points (see the first attached image).  The second attached image shows how interferometry is used from ESA satellite surface elevation data tidal fluctuations to determine where the grounding line has retreated to for the Pine Island Glacier:

https://www.youtube.com/watch?v=W2pYHMx5bN8
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #118 on: June 16, 2014, 04:56:22 PM »
It should not come as a surprise to regular readers that previous estimates of the social cost/consequences of carbon have been vastly underestimated as indicated by new research cited in the following linked article:

http://www.independent.co.uk/environment/climate-change/climate-change-will-cost-world-far-more-than-estimated-9539147.html

Also see:

http://thinkprogress.org/climate/2014/06/16/3449645/stern-updated-climate-model-economic/
« Last Edit: June 17, 2014, 12:31:07 AM by AbruptSLR »
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jai mitchell

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #119 on: June 16, 2014, 09:29:43 PM »
what we didn't realize is that Ackerman was underestimating. . .

http://www.nytimes.com/cwire/2011/07/14/14climatewire-administration-grossly-underestimated-carbon-69396.html

Administration Grossly Underestimated Carbon Cost, Says Study

By TIFFANY STECKER of ClimateWire
 
Published: July 14, 2011

linked document: 

it turns out we were at $245 per ton of CO2 back in 1995
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Lennart van der Linde

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #120 on: June 17, 2014, 12:11:20 PM »
The abstract of the Dietz & Stern paper says [my emphasis]:
http://www.lse.ac.uk/GranthamInstitute/wp-content/uploads/2014/06/Working-Paper-180-Dietz-and-Stern-2014.pdf

'To slow or not to slow' (Nordhaus, 1991) was the first economic appraisal of greenhouse gas emissions abatement and founded a large literature on a topic of great, worldwide importance. In this paper we offer our assessment of the original article and trace its legacy, in particular Nordhaus' later series of 'DICE' models. From this work many have drawn the conclusion that an efficient global emissions abatement policy comprises modest and modestly increasing controls. On the contrary, we use DICE itself to provide an initial illustration that, if the analysis is extended to take more strongly into account three essential elements of the climate problem - the endogeneity of growth, the convexity of damages, and climate risk - optimal policy comprises strong controls. To focus on these features and facilitate comparison with Nordhaus' work, all of the analysis is conducted with a high pure-time discount rate, notwithstanding its problematic ethical foundations.

On p.6 they say about social discounting:
"the rate of pure-time preference is 1.5% and the elasticity of marginal social utility of consumption is 1.5, so that with growth of consumption per capita of, say, 2%, the social discount rate would be 4.5%. We have written elsewhere about why we think it is inappropriate to posit such a high rate of pure-time preference (e.g. Stern, 2013, forthcominga,f) - and we return to explain why in Section 5 - but for the purpose of clarity of comparison we set aside our misgivings, concerning this and other features, in the modelling that comprises the core of this paper."

In Section 5 they give their conclusions and say about discounting (p.23):
"This has not been a paper about the sensitivity of results to pure-time discounting, or other parameters and structures relevant to discounting. As we found in the technical annex to Stern (2007) and in Dietz et al. (2007c; 2007a), lower pure-time discounting does indeed favour stronger and earlier action to curb emissions. Those results were from the 'PAGE' IAM (Hope, 2006), but we know from other work that this is also true of DICE (Nordhaus, 2007). We have argued elsewhere that careful scrutiny of the ethical issues around pure-time discounting points to lower values than are commonly assumed (usually with little serious discussion). Pure-time discounting is essentially discrimination by date of birth in the sense that a life, which is identical in all respects (including time patterns of consumption) but happens to start later, has a lower value. If, for example, the pure-time discount rate were 2%, a life starting 35 years later, but otherwise the same, would have half the value of a life starting now. The time horizon essential to a discussion of climate change makes careful examination of these ethical issues unavoidable. Preliminary calculations indicate that low pure-time discounting will significantly increase the optimal controls in this paper as well."

So it seems Dietz & Stern still estimate the social cost of carbon conservatively.

jai mitchell

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #121 on: June 18, 2014, 06:11:01 PM »
Climate Policies Deserve a Negative Discount Rate

http://www.law.uchicago.edu/files/files/Fleurbaey%20paper_0.pdf

Marc Fleurbaey & Stéphane Zuber

Therefore, if climate policies such as mitigation efforts are paid by the affluent populations of the present generations and greatly benefit the worst off of the distant future generations in the most catastrophic scenarios, it is very likely that the correct discount rates for the evaluation of such policies should be negative, which means that a dollar of benefit in the distant future is worth more than a dollar of effort today.


Cass Sunstein remarked that the fundamental premise of intergenerational discounting (positive) assumes that future generations will be better off than those of today.  It is clear that the current crisis in Syria is directly attributed to a crushing 3 year drought in early 2010 which has now spilled over to Iraq.  The climate-induced heatwaves of India have already led to riots and the El Nino induced late monsoons have exacerbated economic loss and social unrest in the region.  Couple this with the recent increases in oil costs due to the political unrest in Iraq and the "threat multiplier" of climate change on a geopolitical realm is clear.

the potential for widescale economic disruption in India due to climate-induced stresses is multiplied by the political unrest generated in the middle east that was largely attributed to climate-induced stresses several years ago.  This is producing a compounding effect.

we have currently locked in 0.8C of additional globally averaged warming at our current GHG abundances. (that is Hansens' estimate - I believe that even his estimate is conservative).

It is clear that without some kind of mitigation/adaption strategy on a global scale, we will lose our modernity.  In this scenario then, a negative discount rate is more than appropriate (dismal).
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Laurent

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #122 on: June 26, 2014, 05:38:00 PM »
Bangladesh's sea walls may make floods worse
http://www.newscientist.com/article/mg22229752.700-bangladeshs-sea-walls-may-make-floods-worse.html?cmpid=RSS|NSNS|2012-GLOBAL|environment#.U6w8-lFJzlc

sidd

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #123 on: June 26, 2014, 10:27:24 PM »
Half of Bangladesh is history, and the residents know it. One of my nightmares is that the next Osama is a child in Dacca today.

sidd

AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #124 on: July 04, 2014, 12:24:13 AM »
The following link and the associated attached image indicates the projected increase in extreme weather events (the attached figure shows the increase in crop loss) in the USA for the different RCP scenarios; which illustrates the high social cost of carbon, particularly for RCP 8.5 (however the attached image neglects SLR):

http://riskybusiness.org/report/overview/executive-summary
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Bruce Steele

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #125 on: August 23, 2014, 02:17:13 AM »
http://sealevelrise.assembly.ca.gov/reports

Here is a link to a California Assembly report on sea level rise. Ninety pages. I testified on the industry panel and so some of my testimony is included. Although sea level rise and thermal expansion of sea water are intimately linked I make the point that water temperature increases will negatively impact certain fisheries. It should be noted that the infrastructure impacts that get the largest attention in this report are also major contributors to the problem( global warming ). I won't be holding my breath until a report on the biological consequences is convened. Gretchen Hoffman did address  ocean acidification so the committee was somewhat inclusive of biological impacts but I would hope people can increase their focus on habitat loss and shoreline losses as estuary and shorelines move inland and meet highways, railways, and seawalls. Planning on leaving some room for natural shorelines to expand inland will help mitigate some losses but triage for what wildlife remains isn't at this point in planning stages. Many more downsides for wildlife I am undoubtably missing.
     

Laurent

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #126 on: September 02, 2014, 12:11:59 AM »

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #128 on: September 06, 2014, 12:35:29 AM »
The crisis of rising sea level.
http://www.reuters.com/investigates/special-report/waters-edge-the-crisis-of-rising-sea-levels/

The Reuters special investigation focuses on coastal damage already occurring in the United States because of rising sea levels. Slightly higher sea levels means there are roughly twice as many coastal flood events:
The analysis was then narrowed to include only the 25 gauges with data spanning at least five decades. It showed that during that period, the average number of days a year that tidal waters reached or exceeded flood thresholds increased at all but two sites and tripled at more than half of the locations.

The combined costs of flood damage and flood control initiatives are huge.

Laurent

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #129 on: September 06, 2014, 01:38:25 PM »
The increase with SLR should follow the increase in melt in Greenland and Antartica, a doubling every 5 year...

Clare

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #130 on: September 07, 2014, 08:40:50 AM »
This article includes photos of the potential impacts of sea level of 1-2m including storm surges, rise in Auckland, I'm sure some of you will be familiar with this city.

""This new research shows sea level rises could be much higher than a metre by the end of this century," Antarctic Research Centre director and New Zealand's IPCC author Tim Naish said.

"My personal view is that the IPCC has always underestimated sea level rise. When we go back and measure what actually happened with time images and satellites, we find the observations are always above the upper bounds of their predictions," he said.

Naish's views are backed by others including US Antarctic ice sheet modelling expert Professor Rob DeConto. He said warming water around the ice shelves has the potential to destabilise land based ice sheets and contribute to rises of about 4m by 2100."

http://www.stuff.co.nz/environment/10459124/Climate-worries-focus-on-melting-ice

ritter

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #131 on: September 12, 2014, 10:17:58 PM »
It's happening....

Celebrities and billionaires powerless as their multimillion-dollar Malibu homes are mercilessly battered by huge waves

http://www.dailymail.co.uk/news/article-2753877/Celebrities-billionaires-powerless-multimillion-dollar-Malibu-homes-mercilessly-battered-huge-waves-dragging-fences-glass-panels-furniture-sea.html

(granted, not the best source.)

AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #132 on: September 13, 2014, 06:09:27 PM »
The linked reference reminds us that in addition to anthropogenic SLR projections, we need to add both: (a) local/regional SLR variability; and (b) long-term natural regional SLR contributions:

Dangendorf, S., D. Rybski, C. Mudersbach, A. Müller, E. Kaufmann, E. Zorita, and J. Jensen, (2014), "Evidence for long-term memory in sea level", Geophys. Res. Lett., 41, 5564–5571, doi:10.1002/2014GL060538.

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060538/abstract

Abstract: "Detection and attribution of anthropogenic climate change signals in sea level rise (SLR) has experienced considerable attention during the last decades. Here we provide evidence that superimposed on any possible anthropogenic trend there is a significant amount of natural decadal and multidecadal variability. Using a set of 60 centennial tide gauge records and an ocean reanalysis, we find that sea levels exhibit long-term correlations on time scales up to several decades that are independent of any systematic rise. A large fraction of this long-term variability is related to the steric component of sea level, but we also find long-term correlations in current estimates of mass loss from glaciers and ice caps. These findings suggest that (i) recent attempts to detect a significant acceleration in regional SLR might underestimate the impact of natural variability and (ii) any future regional SLR threshold might be exceeded earlier/later than from anthropogenic change alone."
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jai mitchell

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #133 on: September 13, 2014, 08:51:45 PM »
The Yale Climate Forum came out with a new video on Greenland

https://www.youtube.com/watch?v=_PEi0Retg8A

Quote from Prof. Jason Box
Geological Survey of Denmark and Greenland

Greenland's sea level contribution 10 years ago was 1/2 a millimeter per year.  Ten years later it is 1 mm per year.  It is expected that this loss rate will continue to double with a period of somewhere between 5-12 years.  So, the next decade Greenland is losing 2mm/year, the next decade it is 4 mm/year and the next is 8 mm/year.  You take that to the end of the century and the Greenland ice sheet has yielded about 1 meter of sea level rise.

The previous meltwater pulse 2B video, also from the Yale Climate Forum
upthread but repost here:  https://www.youtube.com/watch?v=71l9lzLsBRc

indicates that the Contribution to Sea Level from WAIS is already grossly underestimated in the IPCC AR5

Combine these factors with the thermal expansion potential of 20cm to 50cm by 2100 and the gravitational effects of mid-latitude rise caused by the melt of Antarctica and we are

Easily looking at 1.8 to 3.4 Meters of sea level rise (or more) by 2100.  The More being a worst case scenario RPC 8.5 with multiple natural feedback mechanisms leading to 7C warming by 2100 and 21C warming in the arctic by then.
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #134 on: September 15, 2014, 04:11:28 AM »
Easily looking at 1.8 to 3.4 Meters of sea level rise (or more) by 2100.  The More being a worst case scenario RPC 8.5 with multiple natural feedback mechanisms leading to 7C warming by 2100 and 21C warming in the arctic by then.

jai,

Are you saying that for a RCP 8.5 anthropogenic GHG scenario with multiple positive feedback mechanisms, that SLR could be more than 3.4 m by 2100?  If so, how high do you think that it could go?

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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jai mitchell

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #135 on: September 15, 2014, 08:26:47 AM »
You know SLR.  If the Fat Tail is correct and our ECS is closer to 6C for 2X CO2 and we produce a massive permafrost destabilization and the overturning circulation halts causing a step-change decrease in natural CO2 sequestration and the peat burns in the arctic and the tropical forests burn in the amazon and Indonesia.  Well, we will be looking at even more than the potential 7.5C high range estimate of globally averaged temperatures by 2100.  In this case, one where the scientists expect things are going, but rely on "magical thinking" to give them a reasonable argument to leave out the estimations from their current models (atmospheric fraction is not modeled to increase, but it will.  methane and co2 contributions from permafrost are not modeled in the RCP 8.5 analysis but we know that about 55% of the CO2 will be releases into the atmosphere.  The carbon and methane emission of burning peat and forests around the world is not included in the analysis. . .)

In this scenario then, with massive potential positive feedbacks, the arctic temperatures could see a 17C-22C average warming by 2100. (estimate global average warming to be 10C on its way to +24C by 2300)

This rapid warming would lead to a total collapse of the Greenland ice sheet in the course of a few decades due to hydro fracture,  The WAIS is completely gone and a significant portion of the east shelf is also gone.

so,

Are you saying that for a RCP 8.5 anthropogenic GHG scenario with multiple positive feedback mechanisms, that SLR could be more than 3.4 m by 2100?  If so, how high do you think that it could go?

you tell me.

Note: I updated the potential warming from 7C globally averaged to 10C due to the ECS adjustment from 4.5C to 6C per 2X CO2.  The previous 7C was only considering 4.5C with feedbacks.
« Last Edit: September 15, 2014, 09:07:19 AM by jai mitchell »
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crandles

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #136 on: September 15, 2014, 04:49:23 PM »
http://julesandjames.blogspot.co.uk/search/label/climate%20sensitivity

the additional decade of temperature data from 2000 onwards (even the AR4 estimates typically ignored the post-2000 years) can only work to reduce estimates of sensitivity, and that's before we even consider the reduction in estimates of negative aerosol forcing, and additional forcing from black carbon (the latter being very new, is not included in any calculations AIUI). It's increasingly difficult to reconcile a high climate sensitivity (say over 4C)


I think the data is doing quite well at thinning that fat tail which can arise if you only look at limited data in certain ways.

You are looking at the high end so no real complaint with 4.5C for doubled CO2 ignoring long term feedbacks. Earth system sensitivity of 6C seems quite possible but to assume that kicks in by 2100 seems remarkably rapid even if you think it reasonable to start invoking things like " massive permafrost destabilization and the overturning circulation halts".

Seems like quite a few big 'ifs'.

"total collapse of the Greenland ice sheet in the course of a few decades"
Hmm. If 5 year doublings continue through 2100 then the rate of SLR from ice sheet outflow rates would be pretty substantial. I struggle to comprehend how you could get that many doublings or where adequate heat to allow that would come from. But if you are invoking several low probability events each causing positive feedbacks .....

Maybe somebody should consider this, but I think it would be appropriate if it had clear warnings that it assumes several events considered unlikely.

AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #137 on: September 15, 2014, 06:20:26 PM »
so,

Are you saying that for a RCP 8.5 anthropogenic GHG scenario with multiple positive feedback mechanisms, that SLR could be more than 3.4 m by 2100?  If so, how high do you think that it could go?

you tell me.

Note: I updated the potential warming from 7C globally averaged to 10C due to the ECS adjustment from 4.5C to 6C per 2X CO2.  The previous 7C was only considering 4.5C with feedbacks.

jai,

Since you ask my opinion on a likely RCP 8.5 SLR scenario, I provide the attached image of a probability density function, PDF, of for RSLR of the coast of California by 2070 and 2100.

Best,
ASLR
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Bruce Steele

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #138 on: September 15, 2014, 06:51:53 PM »
 Poll
What is the maximum sea level rise you would expect by 2100?
< 1 meter
2 (4%)1.0 meters
2 (4%)1.5 meters
12 (24%)2.0 meters
9 (18%)2.5 meters
6 (12%)3.0 meters
2 (4%)> 3 meters
17 (34%)
Total Members Voted: 50
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Author Topic: Sea Level Rise by 2100 (POLL)  (Read 5918 times)
OldLeatherneck
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Sea Level Rise by 2100 (POLL)
« on: April 28, 2013, 08:01:13 PM »
Quote
There are various estimates and models of how much sea levels will rise during the 21st century.  If and when policy makers and planners begin to take AGW/CC seriously they need to have some basis for determining what to be prepared for in terms of sea level rise.  If you were to advise them of what they need to be prepared for in terms of anticipated sea levels, how would you advise them, and why?
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No need to start a new poll but for those who missed this I wanted to point it out. About a year and a half ago.

AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #139 on: September 16, 2014, 12:24:57 AM »
The linked Aviso data indicates that in June 2014 mean sea level was at its highest level on record:

ftp://ftp.aviso.oceanobs.com/pub/oceano/AVISO/indicators/msl/MSL_Serie_MERGED_Global_IB_RWT_GIA_Adjust.txt

Date               Mean Sea level (cm)
2014.350338    6.645029e-02
2014.377486    6.631584e-02
2014.404633   6.686508e-02
2014.431781   6.806793e-02
2014.458928    6.941100e-02
2014.486076    7.049582e-02
2014.513223    7.123972e-02
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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jai mitchell

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #140 on: September 16, 2014, 02:03:59 AM »
Re: several low probability feedbacks.

We already are seeing the slowdown of the Meridional Overturning Circulation.  The positive feedback of a snow-free/Ice free northern hemisphere by may 30th, 2099 would produce enough regional warming in the northern hemisphere over the following 3 months to produce an albedo feedback event (not currently modeled) with equivalent forcing of an ADDITIONAL doubling of CO2.

The forests of the Amazon and the peat/forests of Indonesia are already burning, This will continue, There is more carbon ready to release in northern hemisphere permafrost than is in our current atmosphere abundance.  This release on its own, without additional anthropogenic emissions would effectively raise global CO2 to 800ppmv.   

I project that, if RCP 8.5 is continued that the decline of natural sinks and the arctic becoming a net source (future) vs. net sink (now) will produce an additional 20% persistence of annual anthropogenic emissions in the next 40 years and an additional 10% persistence in the next 60 years.  (in this scenario I do not see human civilization lasting beyond 60 years from today).

These feedbacks are already being observed.  You cannot pretend that the permafrost melt and the albedo feedback mechanisms are not happening already.  We cannot afford to pretend that the boreal forests are not already being lost to wildfire each summer and that massive peat fires are not already burning in Siberia and in the Yukon.   Indonesia started to burn in the summer of 1999. 

There has been no analogous period in the geologic record.  In every single one of those previous warming events there was a slower (by several orders of magnitude) event causing the warming within a primordial world with an ancient abundance of  terrestrial and oceanic carbon-based organisms, in the forms of northern hemispheric primordial forests stretching well into the arctic circle and all the bony fish that the ocean could hold; a combined total body mass of several hundred billions of tons of carbon sequestration capacity working constantly to mitigate the climate transition.  ALL LOST NOW. 

Human activity has already worked to destroy those mitigating factors throughout the worlds oceans and the northern hemisphere, produced a pulse forcing more rapid and intense than any time in the world's history.
« Last Edit: September 16, 2014, 07:07:27 AM by jai mitchell »
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AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #141 on: September 16, 2014, 05:11:25 AM »
Anyone interested in adding to the list of positive feedback mechanisms that jai just cited, then take a look at the numerous factors documented in the following thread (but be sure to look at all seven pages of posts):

http://forum.arctic-sea-ice.net/index.php/topic,41.300.html
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nowayout

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #142 on: September 16, 2014, 12:15:59 PM »
Me thinks one honorable mention is missing, even if included in the Selected Forcing Factors thread: methane from the Arctic sea shelf. The warm currents both from the Atlantic and the Pacific side won't do any good, and even without a Big Burrp it will increasingly contribute to the methane levels.
The melting permafrost on land can refreeze in winter. The inundated permafrost is probably more vulnerable.

Laurent

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #143 on: September 18, 2014, 11:18:05 AM »

Sigmetnow

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #144 on: September 18, 2014, 05:45:59 PM »
City of Miami Beach, Florida:  New water pumps are being installed as part of a new storm water infrastructure.
"City officials say the annual king tides are expected to be almost three inches higher than last year. Extreme high tides in the fall and spring push seawater up through aging infrastructure, flooding some Miami Beach streets with more than a foot of water even on sunny days, snarling vehicle and pedestrian traffic."

Cost: $400 million to help protect the city for the next "25 to 30 years."

http://www.washingtonpost.com/national/energy-environment/miami-beach-prepares-for-extreme-high-tides/2014/09/17/5926dc16-3e96-11e4-a430-b82a3e67b762_story.html
People who say it cannot be done should not interrupt those who are doing it.

ritter

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #145 on: September 18, 2014, 08:16:04 PM »
Cost: $400 million to help protect the city for the next "25 to 30 years."
This isn't climate adaptation. This is panic, knee-jerk, band-aidism. Just what do they expect will be necessary in 25 years?!  :o

We, as a species, desperately need to lengthen our planning horizon.

AbruptSLR

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #146 on: September 20, 2014, 01:38:50 AM »
In Post #139 I provided GMSL data from Aviso indicating that in June 2014 global mean sea level was the highest in the satellite era.  The attached plot issued by NASA for August 27 2014, confirms the Aviso data for June, but indicates that by August 27 2014 sea level had dropped back to the mean of the trend line:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Lennart van der Linde

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #147 on: September 24, 2014, 01:58:42 PM »
New paper by Kopp et al. 2014 with some interesting SLR-projections for 2100-2200:
http://onlinelibrary.wiley.com/doi/10.1002/2014EF000239/abstract

Probabilistic 21st and 22nd century sea-level projections at a global network of tide-gauge sites
Robert E. Kopp, Radley M. Horton, Christopher M. Little, Jerry X. Mitrovica, Michael Oppenheimer, D. J. Rasmussen, Benjamin H. Strauss and Claudia Tebaldi

Abstract
Sea-level rise due to both climate change and non-climatic factors threatens coastal settlements, infrastructure, and ecosystems. Projections of mean global sea-level (GSL) rise provide insufficient information to plan adaptive responses; local decisions require local projections that accommodate different risk tolerances and time frames and that can be linked to storm surge projections. Here we present a global set of local sea-level (LSL) projections to inform decisions on timescales ranging from the coming decades through the 22nd century. We provide complete probability distributions, informed by a combination of expert community assessment, expert elicitation, and process modeling. Between the years 2000 and 2100, we project a very likely (90% probability) GSL rise of 0.5–1.2 m under representative concentration pathway (RCP) 8.5, 0.4–0.9 m under RCP 4.5, and 0.3–0.8 m under RCP 2.6. Site-to-site differences in LSL projections are due to varying non-climatic background uplift or subsidence, oceanographic effects, and spatially variable responses of the geoid and the lithosphere to shrinking land ice. The Antarctic ice sheet (AIS) constitutes a growing share of variance in GSL and LSL projections. In the global average and at many locations, it is the dominant source of variance in late 21st century projections, though at some sites oceanographic processes contribute the largest share throughout the century. LSL rise dramatically reshapes flood risk, greatly increasing the expected number of “1-in-10” and “1-in-100” year events.

*************
See particularly their table 1 (attached):
It shows a 5% chance of more than 1.2m of SLR by 2100 and more than 3.7m by 2200 in RCP8.5 and a 0.5% chance of more than 1.8m by 2100 and more than 6.3m by 2200 in that scenario.

Lennart van der Linde

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #148 on: September 26, 2014, 02:38:11 PM »
New paper by Grant, Rohling et al 2014 on rates of SLR over the past five glacial cycles, which shows that rates of at least 1-2 meters/century seem very plausible over the coming centuries:
http://www.nature.com/ncomms/2014/140925/ncomms6076/abs/ncomms6076.html

Sea-level variability over five glacial cycles
K. M. Grant, E. J. Rohling, C. Bronk Ramsey, H. Cheng,   R. L. Edwards, F. Florindo, D. Heslop, F. Marra, A. P. Roberts, M. E. Tamisiea & F. Williams, 2014, Nature Communications

Abstract
Research on global ice-volume changes during Pleistocene glacial cycles is hindered by a lack of detailed sea-level records for time intervals older than the last interglacial. Here we present the first robustly dated, continuous and highly resolved records of Red Sea sea level and rates of sea-level change over the last 500,000 years, based on tight synchronization to an Asian monsoon record. We observe maximum ‘natural’ (pre-anthropogenic forcing) sea-level rise rates below 2 m per century following periods with up to twice present-day ice volumes, and substantially higher rise rates for greater ice volumes. We also find that maximum sea-level rise rates were attained within 2 kyr of the onset of deglaciations, for 85% of such events. Finally, multivariate regressions of orbital parameters, sea-level and monsoon records suggest that major meltwater pulses account for millennial-scale variability and insolation-lagged responses in Asian monsoon records.

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Rohling also gave this presentation yesterday at a big conference in Rotterdam, Delta's in Time of Climate Change, based in part on this new paper:
http://edepot.wur.nl/314954

What seems to be missing from this presentation is the (explicit) observation that the current and future global climate forcing is probably many times stronger than forcings during past deglaciations and interglacials. Therefore SLR of 1-2 meters/century over the coming centuries seems to be a best-case scenario. A substantial risk of higher rates seems very plausible, based on this line of research.

Lennart van der Linde

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Re: Sea Level Rise and Social Cost of Carbon
« Reply #149 on: September 26, 2014, 08:05:36 PM »
Rohling explains for a lay audience:
http://theconversation.com/why-ice-sheets-will-keep-melting-for-centuries-to-come-32171

But again he doesn't point out that the current/future forcing is much bigger than those in the past.