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Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE

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AbruptSLR:

--- Quote from: GeoffBeacon on November 24, 2017, 05:41:12 PM ---Any comments?

--- End quote ---

Geoff,

I enjoyed watching the short video, as it offers a nice summary in a manner that the general public can digest.  Regarding Tamsin Edwards' criticism, I would say that it is irrelevant whether we know, as a proven fact, that human activity has caused the Amundsen Sea Embayment, ASE, marine glaciers to cross their tipping points, as climate models combined with field observation make an almost certain fact.  For example:

1. Proistosescu & Huybers (2017) demonstrate convincingly that since 1750 anthropogenic activity has slowly been increasing the heat content of both the Tropical Pacific Ocean and the Southern Ocean; which not only increases ocean driving ice mass loss from West Antarctic marine glaciers, but also has activated a slow-response positive feedback mechanism that is currently increasing ECS to at least the upper end of the AR5 range.

Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, Vol. 3, no. 7, e1602821, DOI: 10.1126/sciadv.1602821

http://advances.sciencemag.org/content/3/7/e1602821

Thus, not only are humans responsible for increasing the heat content of the Southern Ocean but the associated increase of the current ECS value means that the hydrofracturing mechanism described by DeConto & Pollard could begin as soon as 2040; which would greatly accelerate ice mass loss from all of the WAIS.

2.  There is no serious doubt that human activity caused the ozone hole over Antarctica, which accelerated the westerly wind velocities into a 'sweet spot' for promoting the increased upwelling of relatively warm circumpolar deepwater, CDW, onto the continental shelves that lead to key marine glaciers in the ASE (and other Antarctic marine glaciers).  Thus not only are we responsible for increasing the heat content of the CDW, but we are responsible for the mechanism that delivers this heat content to the grounding line of key marine glaciers.

3.  It is my opinion that human activity has accelerated surface ice mass loss from Greenland (including due to both decreased albedo from air pollution and from increased surface temperatures), which most likely caused a 'cold spot' in the North Atlantic, which most likely has somewhat slowed the Meridional Overturning Circulation, MOC.  Hansen et al (2016) indicates that this slowing of the MOC has reduced the formation of polynas in the Weddell Sea area, which has promoted an increase in Antarctic sea ice area, which has protected the upwelled CDW from cooling as much as it use to; which promotes grounding line retreat of key Antarctic marine glaciers.  This bipolar seesaw action contributes to Hansen's ice-climate feedback which further increases ECS and which further increases the risk of hydrofracturing of key ASE marine glaciers circa 2040.

I could go on, but my main point is that reticent scientists do not hesitate to dream-up any highly improbably scenario (like SSP1) to indicate that we may never cross the 2C limit; but then they do not hesitate to imply that much more probable scenarios that lead to GMSTAs approaching at least 2.7C (at which point DeConto & Pollard's ice cliff and hydrofracturing mechanisms kick into high gear) are not absolutely proven and thus do not merit serious consideration by busy decision makers who are bedeviled by other fat-tailed risks.  Such a reticent scientific posture is not good science.

Best,
ASLR

Neven:
Tamsin Edwards is an apologist for climate risk denial, like a good Brit phlegmatically adding a couple of big paving stones to the road to hell.

magnamentis:

--- Quote from: AbruptSLR on November 24, 2017, 09:28:44 PM ---
--- Quote from: GeoffBeacon on November 24, 2017, 05:41:12 PM ---Any comments?

--- End quote ---

Geoff,

I enjoyed watching the short video, as it offers a nice summary in a manner that the general public can digest.  Regarding Tamsin Edwards' criticism, I would say that it is irrelevant whether we know, as a proven fact, that human activity has caused the Amundsen Sea Embayment, ASE, marine glaciers to cross their tipping points, as climate models combined with field observation make an almost certain fact.  For example:

1. Proistosescu & Huybers (2017) demonstrate convincingly that since 1750 anthropogenic activity has slowly been increasing the heat content of both the Tropical Pacific Ocean and the Southern Ocean; which not only increases ocean driving ice mass loss from West Antarctic marine glaciers, but also has activated a slow-response positive feedback mechanism that is currently increasing ECS to at least the upper end of the AR5 range.

Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, Vol. 3, no. 7, e1602821, DOI: 10.1126/sciadv.1602821

http://advances.sciencemag.org/content/3/7/e1602821

Thus, not only are humans responsible for increasing the heat content of the Southern Ocean but the associated increase of the current ECS value means that the hydrofracturing mechanism described by DeConto & Pollard could begin as soon as 2040; which would greatly accelerate ice mass loss from all of the WAIS.

2.  There is no serious doubt that human activity caused the ozone hole over Antarctica, which accelerated the westerly wind velocities into a 'sweet spot' for promoting the increased upwelling of relatively warm circumpolar deepwater, CDW, onto the continental shelves that lead to key marine glaciers in the ASE (and other Antarctic marine glaciers).  Thus not only are we responsible for increasing the heat content of the CDW, but we are responsible for the mechanism that delivers this heat content to the grounding line of key marine glaciers.

3.  It is my opinion that human activity has accelerated surface ice mass loss from Greenland (including due to both decreased albedo from air pollution and from increased surface temperatures), which most likely caused a 'cold spot' in the North Atlantic, which most likely has somewhat slowed the Meridional Overturning Circulation, MOC.  Hansen et al (2016) indicates that this slowing of the MOC has reduced the formation of polynas in the Weddell Sea area, which has promoted an increase in Antarctic sea ice area, which has protected the upwelled CDW from cooling as much as it use to; which promotes grounding line retreat of key Antarctic marine glaciers.  This bipolar seesaw action contributes to Hansen's ice-climate feedback which further increases ECS and which further increases the risk of hydrofracturing of key ASE marine glaciers circa 2040.

I could go on, but my main point is that reticent scientists do not hesitate to dream-up any highly improbably scenario (like SSP1) to indicate that we may never cross the 2C limit; but then they do not hesitate to imply that much more probable scenarios that lead to GMSTAs approaching at least 2.7C (at which point DeConto & Pollard's ice cliff and hydrofracturing mechanisms kick into high gear) are not absolutely proven and thus do not merit serious consideration by busy decision makers who are bedeviled by other fat-tailed risks.  Such a reticent scientific posture is not good science.

Best,
ASLR

--- End quote ---

another top post as always, must be mentioned from time to time

A-Team:

--- Quote ---Tamsin Edwards is an apologist for climate risk denial.

--- End quote ---
Here is an amusing commentary on their low-ball Antarctic scenario from G Laden and RB Alley.

I did not care for the timing (as it undercut a good public outreach effort from E Holthaus) nor the self-promotional tone of the Guardian piece, nor the barrage of followup tweets, from a minor figure in climate science seemingly assuming a major role as media spokesperson.

I wonder if she will morph into another Dahl-Jensen, Judith Curry, Andrew Rifken, or Bjorn Lomberg, the last thing we need right now in communicating climate risk. Or maybe just naive (as only a scientist can be) to how the Guardian post will be utilized by industry to muddy the risk waters.

I located her researchgate page and the never--published, never-cited 2006 dissertation on Z bosons; this constant recitation of being a particle physicist despite never having worked in that area in a professional capacity. It's not a qualification any more than neurosurgery because the physics of climate change is entirely nineteenth century newtonian (outside a few things like isotopes).

http://gregladen.com/blog/2015/11/22/antarctic-ice-sheet-deterioration-study-left-out-important-factors/
http://www.annualreviews.org/doi/abs/10.1146/annurev-earth-060614-105344?journalCode=earth
http://www.annualreviews.org/doi/abs/10.1146/annurev-earth-060614-105344?journalCode=earth
https://www.researchgate.net/profile/Tamsin_Edwards/contributions
https://www-d0.fnal.gov/results/publications_talks/thesis/edwards/thesis.pdf

"An engineer, a theoretical physicist [ie TE], and a paleoclimatologist are at a wedding. There is a ice large sculpture of a swan on a flat topped table, for decoration. The three start a betting pool on how long it will take for the entire swan, which has already started to melt, to end up on the floor.

The engineer notices some of the meltwater dribbling off the back of the table. She places a set of beer mugs under the streams of water, and records how long it takes for a measured amount of liquid to accumulate. She uses this to generate a graph showing melting over time, estimating the volume of the swan by looking it up in his manual on Ice Sculpture Specifications, and suggests that it will take eleven hours.

The theoretical physicist estimates the volume of ice by assuming a spherical swan, measures the air temperature, and calculates the rate of conversion from ice to water using thermodynamics. He comes up with a different estimate, because the engineer forgot to account for density differences in ice vs water. He estimates that the swan will be entirely the floor in eight and a half hours.

The paleoclimatologist disagrees, and says, “It will take between one and three hours for that swan to be on the floor.”

“Why do you think that, you are clearly an idiot, and I am clearly a physicist, so I must be right!” says the theoretical physicist.

Just as the paleoclimatologist is about to answer, the already melting neck of the swan breaks, and the upper part of the neck and head fall backwards, knocking off one of the large wings. All of those pieces slide off the table and crash on the floor. The stress of the impact causes the second wing to break off, but it stays on the table, but it begins to slowly slide toward the edge, clearly about to fall off as well.

“Because,” the paleoclimatologist says. “Last wedding I went to, that happened.”

AbruptSLR:
I concur that paleo researchers can share a lot of insights with ESM modelers (see the linked open access reference), and one insight that CMIP6 modelers could learn would be to make some of their runs including subroutines of DeConto and Pollard's ice cliff failure and hydrofracturing mechanism, because without the introduction of such freshwater hosing into their models, they will never be able to match the climate responses indicated in the paleo record for Super Interglacials:

Anna S. von der Heydt, Peter Ashwin (Submitted on 12 Apr 2016), "State-dependence of climate sensitivity: attractor constraints and palaeoclimate regimes",    arXiv:1604.03311


http://arxiv.org/abs/1604.03311
&
http://arxiv.org/pdf/1604.03311v1.pdf

Abstract: "Equilibrium climate sensitivity is a frequently used measure to predict long-term climate change. However, both climate models and observational data suggest a rather large uncertainty on climate sensitivity (CS). The reasons for this include: the climate has a strong internal variability on many time scales, it is subject to a non-stationary forcing and it is, on many timescales, out of equilibrium with the changes in the radiative forcing. Palaeo records of past climate variations give insight into how the climate system responds to various forcings although care must be taken of the slow feedback processes before comparing palaeo CS estimates with model estimates. In addition, the fast feedback processes can change their relative strength and time scales over time. Consequently, another reason for the large uncertainty on palaeo climate sensitivity may be the fact that it is strongly state-dependent. Using a conceptual climate model, we explore how CS can be estimated from unperturbed and perturbed model time series. Even in this rather simple model we find a wide range of estimates of the distribution of CS, depending on climate state and variability within the unperturbed attractor. For climate states perturbed by instantaneous doubling of CO2, the sensitivity estimates agree with those for the unperturbed model after transient decay back the attractor. In this sense, climate sensitivity can be seen as a distribution that is a local property of the climate attractor. We also follow the classical climate model approach to sensitivity, where CO2 is prescribed and non-dynamic, leading to CS values consistently smaller than those derived from the experiments with dynamic CO2. This suggests that climate sensitivity estimates from climate models may depend significantly on future dynamics, and not just the level of CO2."

Extract: “... the presence of variability on the attractor on a number of timescales means there are clear and non-trivial distributions of sensitivities, even for unperturbed climates. The distribution of sensitivities depends strongly on the background state as well as on the timescale considered. This suggests that it could be useful to think of the unperturbed climate sensitivity as a local property of the “climate attractor”. For a perturbed system (we have considered instantaneously doubled CO2) this is still useful once an initial transient has decayed. This transient will depend in particular on ocean heat uptake, though also on carbon cycle and biosphere processes that act on time scales roughly equivalent with the forcing time scale. If the climate system has more than one attractor, the perturbed system may clearly evolve to a completely different set of states than the original attractor – a situation that did not occur in the climate model used here. In less extreme cases, there may still be very long transients for some perturbations associated parts of the climate system that are associated with slow feedbacks.

Such perturbations (illustrated in Fig. 1b,d) are not normally applied in climate models used for climate predictions [IPCC, 2013], where climate sensitivity is derived from model simulations considering prescribed, non-dynamic atmospheric CO2. In our conceptual model, we have derived climate sensitivities from both types of perturbations and find that the classical climate model approach (section 2.2, Fig. 4f) leads to significantly lower values of the climate sensitivity than the perturbations away from the attractor with dynamic CO2 (section 2.3, Fig. 11a). This emphasises the importance of including dynamic carbon cycle processes into climate prediction models. Moreover, it supports the idea that the real observed climate response may indeed be larger than the model predicted."

Edit, see also:

https://link.springer.com/article/10.1007/s40641-016-0049-3
&
https://pubs.geoscienceworld.org/gsa/geology/article-abstract/45/7/643/207872/el-nino-southern-oscillation-like-variability-in-a?redirectedFrom=fulltext

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