Ice Apocalypse - Multiple Meters Sea Level Rise

[Sciguy]

Rob DeConto was a contributing author on the IPCC's 2019 Special Report on the Oceans and the Cryosphere (SROCC)  Chapter 4 is dedicated to analyzing the recent studies on sea level rise.  It includes a good overview of MICI, MISI, the role of subsurface water in contact with the floating ice shelves and the importance of grounding line retreat.  They have paragraphs dedicated to analyzing recent observations for Thwaites and Pine Island Glaciers as well as overall assessments of both the Greenland and Antarctic ice sheets.  Here's a link to chapter 4 of the SROCC:

Atmospheric forcing is also become increasingly recognized to be an important factor for the future of the AIS. A sustained (15 days) melt event over the Ross Sea sector of the WAIS in 2016 illustrated both the connectivity of Antarctica to the tropics and El Niño, and the possibility that future meltwater production on ice-shelf surfaces could change in the near future (Nicolas et al., 2017). This was highlighted by Trusel et al. (2015), who evaluated the future expansion of surface meltwater using the snow component in the RACMO2 regional atmospheric model (Kuipers Munneke et al., 2012) and output from CMIP5 GCMs. Under RCP8.5, they find a substantial expansion of surface meltwater production on ice shelves late in the 21st century that exceed melt rates observed before the 2002 collapse of the Larsen B Ice Shelf. Surface meltwater is important for both ice dynamics and SMB due to its potential to reduce albedo, saturate the firn layer, deepen surface crevasses, and to cause flexural stresses that can contribute to ice-shelf break-up (hydrofracturing) (Banwell et al., 2013; Kuipers Munneke et al., 2014). The presence of surface meltwater does not necessarily lead to immediate ice shelf collapse (Bell et al., 2017b; Kingslake et al., 2017), although surface meltwater was a precursor on ice shelves which have collapsed (Scambos et al., 2004; Banwell et al., 2013). This dichotomy illustrates the uncertain role of meltwater and the need for additional study. When and if melt rates will be sufficiently high in future warming scenarios to trigger widespread hydrofracturing is a key question, because the loss of ice shelves is associated with the onset of marine ice sheet instabilities (Crosschapter Box 8 in Chapter 3). Based on the single modelling study by Trusel et al. (2015), we do not expect that widespread ice shelf loss will occur before the end of the 21st century, but due to limited observations and modelling to date, we have low confidence in this assessment.
 

DeConto and Pollard (2016) used an ice sheet model with a formulation similar to that used by Golledge et al. (2015) and Bulthuis et al. (2019) but they include glaciological processes not accounted for in other continental-scale models: 1) surface melt and rain water influence on hydrofracturing of ice shelves; and 2) brittle failure of thick, marine-terminating ice fronts that have lost their buttressing ice shelves. Where the ice fronts are thick enough to form tall ice cliffs above the waterline, they can produce stresses exceeding the strength of the ice, causing calving (Bassis and Walker, 2012). Once initiated, ice-cliff calving has been hypothesized to produce a self-sustaining Marine Ice Cliff Instability (MICI; Cross-chapter Box 8, Chapter 3). The validity of MICI remains unproven (Edwards et al., 2019) and is considered to be characterized by deep uncertainty, but it has the potential to raise GMSL faster than MISI. DeConto and Pollard (2016) represent hydrofracturing and ice-cliff calving with simple parameterizations, but the glaciological processes themselves are supported by more detailed modelling and observations (Scambos et al., 2009; Banwell et al., 2013; Ma et al., 2017; Wise et al., 2017; Parizek et al., 2019). DeConto and Pollard (2016) provide four ensembles for RCP2.6, RCP4.5, and RCP8.5 scenarios, representing two alternative ocean model treatments and two alternative paleo sea-level targets used to tune their model physical parameters. However, their ensembles do not explore the full range of model parameter space or provide a probabilistic assessment (Kopp et al., 2017; Edwards et al., 2018). Under RCP2.6, DeConto and Pollard (2016) find very little GMSL rise from Antarctica by 2100 (0.02–0.16 m), consistent with the findings of Golledge et al. (2015) and Bulthuis et al. (2019). In contrast, their four ensemble means range between 0.26–0.58 m for RCP4.5, and 0.64–1.14 m for RCP8.5.

Note that these are the estimates from their 2016 study. They've since indicated that they are considerable over estimates.

There are summaries of many other studies in the chapter, including ones that address the recently discovered cavity under Thwaites Glacier.  They also address the feedbacks from huge increases in meltwater on ocean stratification.

None of the scenarios lead to the catastrophic consequences implied by AbruptSLR's musings.  All of them agree that if we can keep emissions in-line with the RCP 2.6 scenario, the future sea level rise is greatly reduced from the RCP 8.5 emissions scenarios.  Many agree (including DeConto and Pollard) that the WAIS will not collapse under the RCP 2.6 scenario.

[Lennart van der Linde]

Note that these are the estimates from their 2016 study. They've since indicated that they are considerable over estimates.

There are summaries of many other studies in the chapter, including ones that address the recently discovered cavity under Thwaites Glacier.  They also address the feedbacks from huge increases in meltwater on ocean stratification.

None of the scenarios lead to the catastrophic consequences implied by AbruptSLR's musings.  All of them agree that if we can keep emissions in-line with the RCP 2.6 scenario, the future sea level rise is greatly reduced from the RCP 8.5 emissions scenarios.  Many agree (including DeConto and Pollard) that the WAIS will not collapse under the RCP 2.6 scenario.

As you cite, IPCC SROCC also refers to Kopp et al 2017 (including DeConto & Pollard) which shows a non-negligible risk of pretty fast SLR between 2100-2300 even at RCP2.6 (3m SLR in 2 centuries). See table 1 in Kopp et al attached below. When DeConto & Pollard will have published their lowered estimates for 2100, we may also learn their new estimates for 2200 and 2300, which may be even higher than before, if I've understood their earlier indications of those results correctly. None of these estimates will be as definitive as you seem to present them, which means they still imply risks that should not be ignored, as indicated by the quotes from IPCC SROCC attached below, and as ASLR fortunately does not tire of reminding us, as do experts as for example Dewi Le Bars, when he reflected last February on the implications of two recent papers for the projections by DeConto & Pollard and for ice-climate feedback modelling (as proposed by Hansen et al, amongst others):
https://sites.google.com/site/dewilebars/sea-level-monthly-review/february-2019

On Edwards et al 2019:
'The claim that MICI is "not necessary" to reproduce past sea level high stands is both not really true and not really useful. The uncertainty range about what could have been the contribution of Antarctica to sea level during the Pliocene is 5-20 m and during the Last Interglacial it is 3.6-7.4 m. DeConto and Pollard’s model without MICI can reproduce up to 6 m and 5.5 m respectively for these two period (see Edwards et al. E.D. Fig. 4). So yes it can reproduce the lower part of the ranges. But most of the Pliocene range cannot be reproduced with the no-MICI assumption. What the figure shows is that the model with MICI covers a much bigger par of the possible Antarctic contribution for these periods. And still, even including MICI, the model can only explain a maximum of 12 m contribution for the Pliocene. Which means additional mechanisms would be necessary to cover the whole range of possible Antarctic contribution for that period. The claim that MICI is “not necessary” is also not very useful practically because projections with MICI are used to make high-end sea level scenarios. The important information is then is it possible or not? If it was not possible then it would be good news and decision makers wouldn't need to take it into account. "Not necessary" only has an impact on low-end scenarios, for which MICI would already not be used anyways.'

On Golledge et al 2019:
'Current state of the art (CMIP5 type) climate models do not include ice sheet models so the coupled effects between ice sheets and climate are a blind spot. In these climate models the ice sheets are just white mountains that do not change over time. They might have a snow layer on top of them but no ice. So snow falls on them accumulate a little bit and when it melts it is put in the nearest ocean grid box. If too much accumulates then it is put directly in the ocean to avoid infinite accumulation. What is missing is a model to transform the snow to ice and then transport it back to the sides of the ice sheet or to the ocean under the force of gravity. This is what ice sheet models do. Golledge et al. use the PISM ice sheet model for Greenland and Antarctica and couple them offline to LOVECLIM, an intermediate complexity climate model. Intermediate complexity means lower resolution and simpler physics compared to CMIP5 type climate models. It is the type of models generally used for long paleoclimate simulations.

What they find is that allowing feedbacks between the ice sheets and the climate model leads to strengthen both Antarctic and Greenland mass loss, by 100% and 30% respectively. For Antarctica this is not a surprise, although the magnitude is much bigger than I expected. Freshwater from the melting of ice leads to increase the ocean stratification, because it is is very light. This reduces vertical ocean mixing and as a result the surface of the ocean cools down while the subsurface warms up. Antarctica mostly looses mass from ice shelves basal melt and calving which is strengthened by warmer subsurface ocean temperature. For Greenland, it comes as a surprise to me that the feedback would increase the mass loss, because Greenland mostly looses mass from surface melt and a cooler atmosphere temperature would tend to reduce surface melt. Unfortunately the paper does not explain the mechanisms at play there (or did I miss it?).

There are a few issues with the ice sheet models that reduce my confidence in the projections. For Greenland the model is not able to reproduce the recent fast mass loss acceleration. Therefore the authors artificially impose the mass loss on the model in two ways: (1) decrease the friction between the ice and the bed (basal traction) to have a faster flow between 2000 and 2015 and (2) reduce the snowpack refreezing between 2000 and 2025. Refreezing is important for the mass balance because on ice sheets more than half of the snow that melts in the summer refreezes locally. It never reaches the ocean. Michiel van den Broeke had a similar comments in Trouw (in Dutch). You can force the model to agree with observations but if the model does not have the proper dynamics to explain observations there is no reason it is doing a good job for the future. For Antarctica, the model starts with enormous mass accumulation (1000 Gt/year in 1900) and accumulates mass until the 1980th. This is clearly not possible, such an accumulation would have been seen by tide gauge measurements. In fact as I said in the last review it is expected that Antarctica was slowly loosing mass in the 20th century. Also, the internal variability of grounded ice is so large in the model (Fig. 1a-d) that I do not understand what is going on physically (please let me know if you do).

In conclusion, the paper’s goal is important and it is the first time that two high resolution ice sheet models are coupled to a climate model. This is a big step in the right direction. However, I am not convinced by the results because of the issues mentioned above concerning the ice sheet models. Nevertheless, it is very instructive as it shows the long way that is left for ice sheet models to reach the level at which we can trust their future projections.'

[AbruptSLR]

…
None of the scenarios lead to the catastrophic consequences implied by AbruptSLR's musings.
…

First, I note that the SROCC has 'low confidence' in their collective assessment that key ice shelves will maintain their integrity/buttressing action until the end of the 21st century.  However, when one looks a Sentinel-1 images of the ice shelves in the ASE one wonders how many years (not decades) that they will provide effective buttressing action particularly in the Thwaites Glacier gateway.

Second, while the SROCC is a useful piece of work, any such consensus climate science document cannot be 'cutting-edge' science by definition; thus I believe that it is helpful to consider the opinions of key climate scientists that they express outside of peer reviewed documents.  In this regard, I provide the following two liked videos of Alley and DeConto, respectively, where they indicate that hydrofracturing and cliff failures are a real risk this century:

At around minute 42 of the first linked video entitled: ""Sea-Level Rise: Inconvenient, or Unmanageable?" Richard B. Alley", Alley notes that the ASE marine glaciers could begin to hydrofacture with subsequent cliff failures in about 50-years +/- 50 years:



&

At an EGU press conference DeConto said (see the second linked video) his work implied tipping points for major sea level rise occur between 2 and 2.7C above pre-industrial (which if ECS is ~5C and we continue following RCP 8.5, may occur before 2050):.

http://client.cntv.at/egu2016/press-conference-8 (DeConto starts about 22:10)

Lastly, I provide four related images, in case readers haven't scrolled back to find them.  The first two from DeConto & Pollard (2016 extended data) show their rough projection of the impact of some ice-climate feedbacks.  The third image is a screenshot from DeConto's 2016 EGU press conference (i.e. from the second linked video), and the fourth image illustrates how energy is advected from the tropical ocean sea surface via atmospheric Rossby waves to just south of the Arctic Circle (whereinafter this energy is typically blown into the Arctic Circle by local surface winds).

[Lennart van der Linde]

Two more quotes from IPCC SROCC attached:

[AbruptSLR]

This is just a quick post to note that as the CMIP6 models made numerous changes from the CMIP5 models including both changes to their cloud feedback mechanism and incorporation of several (but not all) ice-climate feedback mechanisms (for the first time); it will take some years of post-processing of the various projections in order to get a better attribution handle as to roughly how much each different feedback mechanism contributed to the increase in the most likely ECS from around 3C to around 5C (which is a major change).  I this regard, I note that initial assessment assign the lion's share of this increase in projected ECS to cloud feedback mechanisms; but I note that several ice-climate feedbacks trigger net positive cloud feedback mechanisms.  Thus right now it is hard to say how much of the nominally 2C increase in ECS is due to refinements of pre-existing mechanisms (including cloud feedback mechanisms) updated from the CMIP5 models and how much is associated with brand new ice-climate feedbacks that only consider MISI-type ice sheet forcing and not MICI-type ice sheet forcing.

Hopefully, for CMIP7 MICI mechanisms will be sufficiently calibrated to be incorporated within the CMIP7 models themselves, so that the new and improved MICI mechanisms/models are driven by the full cascade of forcings/feedbacks calculated by the CMIP7 models.  In this regard, I remind readers that the DeConto & Pollard (2016) sea-level contribution projections were omitted from SROCC because their surface meltwater (for hydrofracturing of ice shelves) projections were higher than those projected by CMIP5 models (with ECS nominally 3C); while surface meltwater projections from the final CMIP6 models (with nominal ECS on the order of 5C) are likely to be higher than the CMIP5 projection; but which may be lower than the future CMIP7 ice shelf surface meltwater projections.

[AbruptSLR]

The linked reference only considers the uncertainty in sea-level rise projections associated with MISI mechanisms (and ignores both MICI mechanisms and ice-climate feedback mechanisms).  Nevertheless, as the first attached image from this reference has no time units; it presents a useful concept that with time (whether for MISI mechanisms over centuries or MICI mechanisms over decades) the shape of pdf controlling the ice volume remaining in the AIS ice sheet becomes negatively skewed; which means that large (& rapid) contributions from the AIS to SLR become much more likely.

Alexander A. Robel, Hélène Seroussi, and Gerard H. Roe (July 23, 2019), "Marine ice sheet instability amplifies and skews uncertainty in projections of future sea-level rise", PNAS, 116 (30) 14887-14892, https://doi.org/10.1073/pnas.1904822116

https://www.pnas.org/content/116/30/14887

Significance
The potential for collapse of the Antarctic ice sheet remains the largest single source of uncertainty in projections of future sea-level rise. This uncertainty comes from an imperfect understanding of ice sheet processes and the internal variability of climate forcing of ice sheets. Using a mathematical technique from statistical physics and large ensembles of state-of-the-art ice sheet simulations, we show that collapse of ice sheets widens the range of possible scenarios for future sea-level rise. We also find that the collapse of marine ice sheets makes worst-case scenarios of rapid sea-level rise more likely in future projections.

Abstract
Sea-level rise may accelerate significantly if marine ice sheets become unstable. If such instability occurs, there would be considerable uncertainty in future sea-level rise projections due to imperfectly modeled ice sheet processes and unpredictable climate variability. In this study, we use mathematical and computational approaches to identify the ice sheet processes that drive uncertainty in sea-level projections. Using stochastic perturbation theory from statistical physics as a tool, we show mathematically that the marine ice sheet instability greatly amplifies and skews uncertainty in sea-level projections with worst-case scenarios of rapid sea-level rise being more likely than best-case scenarios of slower sea-level rise. We also perform large ensemble simulations with a state-of-the-art ice sheet model of Thwaites Glacier, a marine-terminating glacier in West Antarctica that is thought to be unstable. These ensemble simulations indicate that the uncertainty solely related to internal climate variability can be a large fraction of the total ice loss expected from Thwaites Glacier. We conclude that internal climate variability alone can be responsible for significant uncertainty in projections of sea-level rise and that large ensembles are a necessary tool for quantifying the upper bounds of this uncertainty.

Furthermore, in my last post I noted that DeConto & Pollard (2016)'s SLR contributions from the AIS were not included in SROCC's consensus SLR projections because the surface ice meltwater that they assumed would collapse the ASE ice shelves/tongue via hydrofracturing occurred earlier than projected by CMIP5.  However, the second image shows the Thwaites Ice Tongue and Eastern Ice Shelf in October 2012; while the third image shows the same ice features seven years later on October 29, 2019; and comparing these images shows that not only is the Ice Tongue shorter, narrower and has reduced structural integrity but also that both the eastern and western sides of the Eastern Ice Shelf have both sustained significant amounts of calving (leaving the TEIS narrower).  Thus, it is entirely plausible that the Thwaites Ice Tongue and the western side of the TEIS may collapse sufficiently within the next decade to allow a hypothetical ice mélange from hypothetical ice cliff failures near the subglacial cavity at the upstream base of the Thwaites Ice Tongue (what I call the 'Big Ear') to float away and not to provide buttressing action against the hypothetical ice cliffs; even without any hydrofracturing at all.

[Sciguy]

There is also a lot of confusion on this whole website about the RCP scenarios used to make future projections.  The most alarming studies use RCP 8.5 to get their alarming results and they tend to downplay the benefits of limiting emissions to the RCP 2.6 scenario.

People look at emissions today and think they will continue on at the same rate into the future without taking into account recent advancements in renewable energy and battery technology.  (Keep in mind that the bulk of emissions projected for the 21st century occur after 2030.)  Here is a study that explains the assumptions in the RCP 8.5 scenario:

https://link.springer.com/article/10.1007/s10584-011-0149-y

A growing population and economy combined with assumptions about slow improvements of energy efficiency lead in RCP8.5 to a large scale increase of primary energy demand by almost a factor of three over the course of the century (Fig. 5). This demand is primarily met by fossil fuels in RCP 8.5. There are two main reasons for this trend. First, the scenario assumes consistent with its storyline a relatively slow pace for innovation in advanced non-fossil technology, leading for these technologies to modest cost and performance improvements (e.g., learning rates for renewables are below 10% per doubling of capacity; see also Riahi et al. 2007 for further detail). Fossil fuel technologies remain thus economically more attractive in RCP8.5. Secondly, availability of large amounts of unconventional fossil resources extends the use of fossil fuels beyond presently extractable reserves (BP 2010). The cumulative extraction of unconventional fossil resources lies, however, within the upper bounds of theoretically extractable occurrences from the literature (Rogner 1997; BGR 2009; WEC 2007).9

Notice that coal makes up most of the projected energy use in RCP8.5.  In RCP 8.5, coal use is projected to increase significantly in 2030 and continue strong growth until 2100.

In reality, wind and solar power have already become cheaper than coal and coal use is expected to peak by 2030 (and possibly even earlier) as the following article, published in August 2019 explains:

https://www.reuters.com/article/us-china-coal-climate/chinas-coal-demand-to-peak-around-2025-global-usage-to-follow-report-idUSKCN1VD0BD

China's coal demand to peak around 2025, global usage to follow: report

BEIJING (Reuters) - China’s coal demand will start to fall in 2025 once consumption at utilities and other industrial sectors reaches its peak, a state-owned think tank said in a new report, easing pressure on Beijing to impose tougher curbs on fossil fuels.

The world’s biggest coal consumer is expected to see total consumption fall 18% from 2018 to 2035, and by 39% from 2018 to 2050, the CNPC Economics and Technology Research Institute, run by the state-owned China National Petroleum Corp (CNPC), forecast in a report on Thursday.

However, the CNPC researchers said they expected the total share of coal to drop to 40.5% by 2035 as renewable, nuclear and natural gas capacity continues to increase rapidly.
“With coal demand in China falling gradually, world coal consumption is forecast to reach a peak within 10 years. Meanwhile, China’s coal demand, currently accounting for half of the world’s total, will decline to around 35% by 2050,” the report said.

Wind and solar continue to fall in cost and are now approaching parity with natural gas.

https://www.fastcompany.com/90402331/its-now-cheaper-to-build-new-renewables-than-it-is-to-build-natural-gas-plants

09.11.19 world changing ideas

It’s now cheaper to build new renewables than it is to build natural gas plants
People could save $29 billion on their electric bills if utilities built new clean energy instead of new natural gas plants.

By Adele Peters  2 minute Read
Clean energy has reached a tipping point: It’s now cheaper to build and use a combination of wind, solar, batteries, and other clean tech in the U.S. than to build most proposed natural gas plants. Utilities want to spend $90 billion to build new gas plants and $30 billion to build new gas pipelines—but if they used renewables instead, consumers could save $29 billion in electricity bills, according to a new report from the nonprofit Rocky Mountain Institute.

The researchers looked at how natural gas plants are used on power grids today and then calculated what would be necessary for clean energy to replace those plants, including batteries to store power when wind and solar aren’t available. It’s already cheaper, in almost all cases, to build and run new clean energy projects than natural gas projects. By the middle of the 2030s, clean energy could drop in cost so much that it will be cheaper to build and run new renewables than to keep existing gas plants running, and gas plants could quickly become stranded assets (the same thing is currently happening with coal plants around the country). More than 90% of recently built plants could be forced into early retirement.

[AbruptSLR]

Milillo et al. (2019) highlighted the importance of ocean tides on the retreat of the Thwaites Glacier grounding line, and particularly on the formation/expansion of subglacial cavities in the 50-km wide Thwaites Glacier gateway (which are of critical importance).  Therefore, I provide a link to the Padman et al. (2018) reference entitled: "Ocean Tide Influences on the Antarctic and Greenland Ice Sheets".  This reference discusses may of the key influences of ocean tides on ice shelves (/tongues) and on grounding line retreat for marine and marine-terminating glaciers.  While such tidal influences are too numerous to conveniently discuss in this post; the attached associated image illustrates that not only do tidally included ocean current melt glacial ice near the grounding line, but they also cause the glacial ice to repeatedly lift off the glacial bed upstream of the grounding line (see location F in the image); which can induce fracturing (forming crevasses) of the glacial ice upstream of the grounding line (location G in the image).  Here I note that such crevasses location just upstream of the grounding line, produces ice bergs that can float away from the Thwaites 50-km wide gateway; which could abruptly expose unstable ice cliffs in the gateway when the 'Big Ear' cavity collapses in the future:

Laurie Padman et al. (8 January 2018), "Ocean Tide Influences on the Antarctic and Greenland Ice Sheets", Reviews of Geophysics, https://doi.org/10.1002/2016RG000546

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016RG000546

Abstract
Ocean tides are the main source of high‐frequency variability in the vertical and horizontal motion of ice sheets near their marine margins. Floating ice shelves, which occupy about three quarters of the perimeter of Antarctica and the termini of four outlet glaciers in northern Greenland, rise and fall in synchrony with the ocean tide. Lateral motion of floating and grounded portions of ice sheets near their marine margins can also include a tidal component. These tide‐induced signals provide insight into the processes by which the oceans can affect ice sheet mass balance and dynamics. In this review, we summarize in situ and satellite‐based measurements of the tidal response of ice shelves and grounded ice, and spatial variability of ocean tide heights and currents around the ice sheets. We review sensitivity of tide heights and currents as ocean geometry responds to variations in sea level, ice shelf thickness, and ice sheet mass and extent. We then describe coupled ice‐ocean models and analytical glacier models that quantify the effect of ocean tides on lower‐frequency ice sheet mass loss and motion. We suggest new observations and model developments to improve the representation of tides in coupled models that are used to predict future ice sheet mass loss and the associated contribution to sea level change. The most critical need is for new data to improve maps of bathymetry, ice shelf draft, spatial variability of the drag coefficient at the ice‐ocean interface, and higher‐resolution models with improved representation of tidal energy sinks.

Caption: "(a) Schematic showing a cross‐section through an ice sheet grounding zone, after Fricker et al. (2009). Vertical scale is greatly exaggerated. From landward to seaward: F is the landward limit of tidal flexure; G is the limit of ice flotation, that is, the grounding line; Ib is the break‐in slope; Im is the local elevation minimum; and H is the landward limit of the hydrostatic zone of free‐floating ice shelf, or the seaward limit of ice flexure. We define the region between F and H as the grounding zone, which is typically 5–10 km wide. (b) ICESat elevation profile (with respect to the WGS‐84 ellipsoid) for a segment of track 0218 crossing the grounding line of Institute Ice Stream, southern Ronne Ice Shelf, following Fricker and Padman (2006). The limits of flexure, points F and H, determined from ICESat repeat track analysis shown in Figure 4c are indicated. (c) ICESat‐derived height anomalies (difference of each repeat track profile relative to mean of all profiles). Equivalent anomalies at the same epochs based on tide predictions from CATS2008 are indicated by the horizontal lines between 40 and 50 km. Epochs for repeat track anomalies and tide prediction anomalies are coded by color."

Edit: If it is confusion to some readers how an iceberg upstream of the grounding line could float away, I provide the second attached image from Rignot et al (2017) shown a elevation section cut near the Thwaites gateway just to the west of the 'Big Ear' subglacial cavity; which shows that hydrostatic forces exceed gravitational forces upstream of the local grounding line.  Thus if/when the Thwaite Ice Tongue collapses next; such icebergs currently grounded upstream of the grounding line could pop-up and float away.

[AbruptSLR]

There is also a lot of confusion on this whole website about the RCP scenarios used to make future projections.  The most alarming studies use RCP 8.5 to get their alarming results and they tend to downplay the benefits of limiting emissions to the RCP 2.6 scenario.
…

There is quite a bit of confusion on the part of left-tail-thinking advocates on the role of the different RCP scenarios on ice-climate associated risks.  Indeed, there are too many points of confusion to address in this post besides the following:

1. The current 'ice plug' in the 50-km wide Thwaites Glacier gateway many collapse circa 2030 without any more anthropogenic radiative forcing (say to induce meltwater on top of the Thwaites Ice Shelf/Tongue) if the current tidal pumping of warm CDW into the subglacial cavity in the gateway bed trough continues to expand this subglacial cavity; which might then be followed by collapse of this subglacial cavity which might then trigger a MICI-type of collapse of the glacial ice in the Byrd Subglacial Basin.  If so then we should have stayed below an atmospheric carbon dioxide concentration of 350ppm as advocated by James Hansen.

2. Without a socio-economic collapse, it could take decades to transition from a primarily fossil fuel driven global economy to a more sustainable global economy; assuming that global decision makers were determined to support such a rapid transition.  However, given the current lobbying efforts to promote non-conventional fossil fuels like fracked shale oil/gas and tar sand oil; decision makers may well be slow (as they have been in recent decades) to support such a transition; by which time a cascade of climate change tipping points may (or may not) have been triggered.

3. The first attached scripps plot shows that we are indeed currently following a RCP 8.5 pathway; while the second attached plot shows that we are currently not following the RCP6 pathway, let alone the RCP 2.6 pathway (which like almost certainly would require the widespread use of negative emissions technology to achieve, but it is questionable whether any agency will be willing to pay for the widespread application of such negative emissions technology).

[Sciguy]

As more research is done into the MICI failure mechanism, it seems less plausible.  The following two papers, published in the past 10 days, would seem to doom the MICI hypothesis.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL084397?af=R

A Speed Limit on Ice Shelf Collapse through Hydrofracture
Alexander A. Robel  Alison F. Banwell
First published: 24 October 2019

Abstract
Increasing surface melt has been implicated in the collapse of several Antarctic ice shelves over the last few decades, including the collapse of Larsen B Ice Shelf over a period of just a few weeks in 2002. The speed at which an ice shelf disintegrates strongly determines the subsequent loss of grounded ice and sea level rise, but the controls on collapse speed are not well understood. Here we show, using a novel cellular automaton model, that there is an intrinsic speed limit on ice shelf collapse through cascades of interacting melt pond hydrofracture events. Though collapse speed increases with the area of hydrofracture influence, the typical flexural length scales of Antarctic ice shelves ensure that hydrofracture interactions remain localized. We argue that the speed at which Larsen B Ice Shelf collapsed was caused by a season of anomalously high surface meltwater production.

It's important to note that the collapse of an ice shelf takes weeks, not hours, as that allows time for the resultant ice cliff to flow viscously to height below which brittle failure would occur.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL084183?af=R

Marine Ice Cliff Instability Mitigated by Slow Removal of Ice Shelves
Fiona Clerc  Brent M. Minchew  Mark D. Behn
First published: 21 October 2019

Abstract
The accelerated calving of ice shelves buttressing the Antarctic Ice Sheet may form unstable ice cliffs. The marine ice‐cliff instability (MICI) hypothesis posits that cliffs taller than a critical height (~90‐m) will undergo structural collapse, initiating runaway retreat in ice‐sheet models. This critical height is based on inferences from pre‐existing, static ice cliffs. Here we show how critical height increases with the timescale of ice‐shelf collapse. We model failure mechanisms within an ice cliff deforming after removal of ice‐shelf buttressing stresses. If removal occurs rapidly, the cliff deforms primarily elastically and fails through tensile‐brittle fracture, even at relatively small cliff heights. As the ice‐shelf removal timescale increases, viscous relaxation dominates, and the critical height increases to ~540 m for timescales > days. A 90‐m critical height implies ice‐shelf removal in under an hour. Incorporation of ice‐shelf collapse timescales in prognostic ice‐sheet models will mitigate MICI, implying less ice‐mass loss.

[AbruptSLR]

As more research is done into the MICI failure mechanism, it seems less plausible.  The following two papers, published in the past 10 days, would seem to doom the MICI hypothesis.

…

First, the two references that you cite were already discussed in this thread and were found not to represent the doom of the MICI hypothesis, but rather calibration considerations.

Second, neither of the references that you cite consider the current situation in front of the Thwaites Glacier 50-km wide gateway; which as noted by Milillo et al. (2019): "Such complexities in ice-ocean interaction are not currently represented in coupled ice sheet/ocean models."

P. Milillo, E. Rignot, P. Rizzoli, B. Scheuchl, J. Mouginot, J. Bueso-Bello, and P. Prats-Iraola (2019), "Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica", Sci Adv. 5(1): eaau3433, doi: 10.1126/sciadv.aau3433
PMCID: PMC6353628
PMID: 30729155

https://advances.sciencemag.org/content/5/1/eaau3433
&
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353628/

Abstract: "The glaciers flowing into the Amundsen Sea Embayment, West Antarctica, have undergone acceleration and grounding line retreat over the past few decades that may yield an irreversible mass loss. Using a constellation of satellites, we detect the evolution of ice velocity, ice thinning, and grounding line retreat of Thwaites Glacier from 1992 to 2017. The results reveal a complex pattern of retreat and ice melt, with sectors retreating at 0.8 km/year and floating ice melting at 200 m/year, while others retreat at 0.3 km/year with ice melting 10 times slower. We interpret the results in terms of buoyancy/slope-driven seawater intrusion along preferential channels at tidal frequencies leading to more efficient melt in newly formed cavities. Such complexities in ice-ocean interaction are not currently represented in coupled ice sheet/ocean models."

Caption for the first image (Fig 1): "Thwaites Glacier, West Antarctica.
(A) Map of Antarctica with Thwaites Glacier (red box). (B) Shaded-relief bed topography (blue) with 50-m contour levels (white) (16), grounding lines color-coded from 1992 to 2017, and retreat rates for 1992–2011 (green circle) versus 2011–2017 (red circle) in kilometer per year. Thick yellow arrows indicate CDW pathways (32). White boxes indicate outline of figs. S1 and S2 (C) DInSAR data for 11 to 12 and 27 to 28 April 2016, with grounding lines in 2011, 2016, and 2017 showing vertical displacement, dz, in 17-mm increments color-coded from purple to green, yellow, red, and purple again. Points A to F are used in Fig. 2. (D) Height of the ice surface above flotation, hf, in meters. (E) Change in ice surface elevation, dh, between decimal years 2013.5 and 2016.66 color-coded from red (lowering) to blue (rising). (F) Ice surface speed in 2016–2017 color-coded from brown (low) to green, purple, and red (greater than 2.5 km/year), with contour levels of 200 m/year in dotted black."

Caption for the second image (Fig 3): "Ice thickness change of Thwaites Glacier.
(A) Ice surface elevation from Airborne Topographic Mapper and ice bottom from MCoRDS radar depth sounder in 2011, 2014, and 2016, color-coded green, blue, and brown, respectively, along profiles T1-T2 and (B) T3-T4 with bed elevation (brown) from (16). Grounding line positions deduced from the MCoRDS data are marked with arrows, with the same color coding. (C) Change in TDX ice surface elevation, h, from June 2011 to 2017, with 50-m contour line in bed elevation and tick marks every 1 km."

Furthermore, the third attached image shows how the largest subglacial cavity identified by Milillo et al. (2019) is located, with regard to the 50-km wide Thwaites Glacier gateway.

Finally, the fourth attached image (from 2013) shows how if/when the Thwaites Ice Tongue collapses the icebergs from the base of the Thwaites Ice Tongue to the upstream end of the subglacial cavity could quickly float away thus abruptly exposing unstable ice cliffs on the retrograde bed slope of the Thwaites Glacier gateway that leads directly into the Byrd Subglacial Basin.

[AbruptSLR]

The linked article focuses on just two issues that left-tail thinking advocates generally ignore; e.g.:
1) the use of air conditioners and refrigeration will increase rapidly with climate change; and
2) increasing wildfires can make the electrical power grid unreliable thus decreasing the viability large-scale application of many 'sustainable' power sources

Title: "How climate change makes fighting it harder"

https://www.axios.com/climate-change-air-conditioning-california-wildfires-b9874883-e380-4cdd-a61a-e48fa1a69b2f.html

[AbruptSLR]

For those who may think that the Thwaites Glacier represents a special case that may have limited/local susceptibility of ice cliff failure mechanisms, and that there would be no future cascade of tipping point mechanisms associated with an abrupt collapse of the Thwaites Glacier (say in coming decades; I provide the linked reference that discusses just one tipping point mechanism (of many) associated with the response of the Southern Ocean/MOC that would almost certainly be triggered by an abrupt release of icebergs from the potential rapid collapse of the Thwaites Glacier.

The linked (open access) Fogwill et. al. (2015) reference first notes that in order to achieve the observed sea levels during recent past interglacial periods (particularly the Eemian) as yet unidentified mechanisms must have contributed to the accelerated collapse of major portions of the WAIS.  The reference then assumes various collapse scenarios for the WAIS and uses a regional climate model to study the sensitivity of the Southern Ocean to the assumed scenarios in order to study one of several likely feedback mechanisms that could contribute to accelerated WAIS collapse.  The attached image shows the projected decrease in AABW formation (which would slow the MOC) and the increase in CDW (400 to 700m deep) temperature (which would accelerate ice mass loss from Antarctic marine glaciers) associated with these scenarios.  Of particular, concern is that the projections indicate that the scenarios result in the advection of the warmer CDW to key marine glaciers (in this scenario including PIG & other ASE marine glaciers), which results in a positive feedback for sustained WAIS collapse.  The authors acknowledge that their findings are likely conservative (ESLD) as they do not consider continued GHG emissions nor possible high values for ECS/ESS, nor the positive feedbacks cited by Hansen et. al. (2016).  The reference concludes by calling for the development of more advanced climate models (such as E3SM) to further investigate the many and complex issues associated with this matter:

C. J. Fogwill, S. J. Phipps, C. S. M. Turney & N. R. Golledge (2015), "Sensitivity of the Southern Ocean to enhanced regional Antarctic ice sheet meltwater input", Earth's Future, Volume 3, Issue 10, Pages 317–329, DOI: 10.1002/2015EF000306

http://onlinelibrary.wiley.com/doi/10.1002/2015EF000306/full

Abstract: "Despite advances in our understanding of the processes driving contemporary sea level rise, the stability of the Antarctic ice sheets and their contribution to sea level under projected future warming remains uncertain due to the influence of strong ice-climate feedbacks. Disentangling these feedbacks is key to reducing uncertainty. Here we present a series of climate system model simulations that explore the potential effects of increased West Antarctic Ice Sheet (WAIS) meltwater flux on Southern Ocean dynamics. We project future changes driven by sectors of the WAIS, delivering spatially and temporally variable meltwater flux into the Amundsen, Ross, and Weddell embayments over future centuries. Focusing on the Amundsen Sea sector of the WAIS over the next 200 years, we demonstrate that the enhanced meltwater flux rapidly stratifies surface waters, resulting in a significant decrease in the rate of Antarctic Bottom Water (AABW) formation. This triggers rapid pervasive ocean warming (>1°C) at depth due to advection from the original site(s) of meltwater input. The greatest warming is predicted along sectors of the ice sheet that are highly sensitized to ocean forcing, creating a feedback loop that could enhance basal ice shelf melting and grounding line retreat. Given that we do not include the effects of rising CO2—predicted to further reduce AABW formation—our experiments highlight the urgent need to develop a new generation of fully coupled ice sheet climate models, which include feedback mechanisms such as this, to reduce uncertainty in climate and sea level projections."

Extract: "One major uncertainty, however, is how the marine-based West Antarctic Ice Sheet (WAIS) will respond to future climate change, and particularly how it may contribute to future global mean sea level (GMSL) [Lenton et al., 2008; Pritchard et al., 2012; Vaughan et al., 2013; Golledge et al., 2015]. In part, this question arises from analogy with past interglacial periods when, despite only small apparent increases in mean atmospheric and ocean temperatures, GMSL is predicted to have been far higher than present [Dutton et al., 2015; Dutton and Lambeck, 2012; Kopp et al., 2009]. To achieve these levels, undefined mechanisms must have been at work that substantially increased the net contribution of the Earth's ice sheets to global sea level [Fogwill et al., 2014].

One such mechanism could have been through ice-ocean feedbacks that arose as a consequence of enhanced meltwater discharge to the Southern Ocean. This has been highlighted in recent studies investigating the apparent coupling between Antarctic ice sheet change and atmospheric temperatures during past interglacials [Holden et al., 2010]. In conclusion, this detailed study of the Last Interglacial demonstrated that feedbacks from WAIS retreat were required to simulate the magnitude of the observed warming within Antarctic ice core records.
…
To summarize, the changes in the properties of AABW triggered by increasing freshwater input in the Southern Ocean surrounding Antarctica have critical implications for the dynamics of the Antarctic ice sheet. Intriguingly, several recent studies provide growing evidence of rapid contemporary changes in the properties of AABW [Jacobs et al., 2002; Rhein et al., 2013; van Wijk and Rintoul, 2014]. Observations suggest that the AABW layer is warming, freshening, and contracting in volume [Jacobs et al., 2002], although the drivers of these changes are not yet clear. Our simulations and the mechanism described above suggests that contemporary Southern Ocean freshening may already be occurring as a result of increasing delivery of meltwater from Antarctic ice, with the possibility that a marked reduction in the rate of AABW production may be imminent [Purkey and Johnson, 2013; Rhein et al., 2013], triggering further warming at depth in the Southern Ocean. When combined with uncertainties regarding potential increases in ocean temperatures due to shifting winds and/or changing ocean circulation patterns, the potential for marked changes in ocean ice sheet dynamics over the next century is high [Fogwill et al., 2014; Hellmer et al., 2012; Miles et al., 2013; Spence et al., 2014]. Our experiments provide a unique insight into potential future changes in the Southern Ocean that have important implications for the stability of the Antarctic ice sheets. This study examines just one of a number of strong feedback mechanisms operating at the ocean ice sheet interface that question current sea level rise projections; clearly, modeling studies will need to integrate these feedbacks to gain a more realistic picture of future change."

[longwalks1]

In regard to the Guardian article of the Amazon tipping point.  I have gotten behind  in this thread, busy and one needs to delve and think deeply on this thread. 

From the author cited for her report on papers.  Oct 31 
https://www.piie.com/blogs/realtime-economic-issues-watch/lets-look-evidence-tipping-points-amazon-rainforest

She cites the two primary papers she utilized and critiques the Bolsanaro government regime. 

Her "PIEE" chart is here (bad pun)
https://www.piie.com/research/piie-charts/amazon-deforestation-fast-nearing-tipping-point-when-rainforest-cannot-sustain

Her 7 page review that the Guardian cited is here
https://www.piie.com/sites/default/files/documents/pb19-15.pdf

As always, with admiration to the posts here. 

[AbruptSLR]

Most people are not prepared to deal with deep uncertainty risks related to sustainability (whether: ecological stress/degradation; pollution or climate change); and consequently, prefer thinking about the left-tail of any associate PDF.  Unfortunately, we are currently forcing Earth Systems at rates not observed in the paleo-record; which increases the probability for the occurrence of cascades of tipping points required to realize some of the risks associate with deep uncertainty.

For instance, in 2008 Pfeffer et al. developed the first attached PDF for possible eustatic SLR by 2100 (with units of mm); which did not consider ocean-marine glacier interactions and thus this PDF by Pfeffer et al only roughly corresponds to the SLR indicated by the combined yellow & pink curves in the second image; which is less than half of the possible SLR by 2100 when considering deep uncertainty.

[AbruptSLR]

More bad news about likely abrupt increases in GHG emissions due to permafrost degradation this century:

B. Teufel  & L. Sushama (2019),"Abrupt changes across the Arctic permafrost region endanger northern development", Nature Climate Change, volume 9, pages858–862, DOI: https://doi.org/10.1038/s41558-019-0614-6

https://www.nature.com/articles/s41558-019-0614-6

Abstract: "Extensive degradation of near-surface permafrost is projected during the twenty-first century, which will have detrimental effects on northern communities, ecosystems and engineering systems. This degradation is predicted to have consequences for many processes, which previous modelling studies have suggested would occur gradually. Here we project that soil moisture will decrease abruptly (within a few months) in response to permafrost degradation over large areas of the present-day permafrost region, based on analysis of transient climate change simulations performed using a state-of-the-art regional climate model. This regime shift is reflected in abrupt increases in summer near-surface temperature and convective precipitation, and decreases in relative humidity and surface runoff. Of particular relevance to northern systems are changes to the bearing capacity of the soil due to increased drainage, increases in the potential for intense rainfall events and increases in lightning frequency. Combined with increases in forest fuel combustibility, these are projected to abruptly and substantially increase the severity of wildfires, which constitute one of the greatest risks to northern ecosystems, communities and infrastructures. The fact that these changes are projected to occur abruptly further increases the challenges associated with climate change adaptation and potential retrofitting measures."

[AbruptSLR]

Every now and then I feel philosophical, so here goes:

1. Can someone be called alarmist if there really is something to be alarmed about?  Alternately, just because someone is paranoid doesn't mean that they are wrong.

2. As neither the AR5 nor the 2015 Paris Climate Agreement calculated how much negative emissions would be required to compensate for crossing an Earth System tipping point (let alone a cascade of tipping points); how can the IPCC claim to have provided decision makers with adequate climate change guidance?

See also:
Shinichiro Fujimori et al, A new generation of emissions scenarios should cover blind spots in the carbon budget space, Nature Climate Change (2019). DOI: 10.1038/s41558-019-0611-9

https://www.nature.com/articles/s41558-019-0611-9

3. When calculating potential impacts, Integrated Assessment Models (IAMs) seldomly evaluate combinations of climate considerations (such as SLR combined with increased tidal variations); how can decision makers adequately assess right-tail risks?

4. When we are currently imposing radiative forcing at a rate approximately one hundred times faster than occurred during the PETM; how can the IPCC use values of ECS determined from the paleo-record to access future climate change without evaluating the impacts for factors such as cascading tipping points and/or ice-climate (ice sheet forcing) feedbacks?

5. If the acceptable operation of our modern global socio-economic system is dependent on engineering systems with factors of safety adequate to address uncertainties without system shutdown; why do IPCC assessments focus on likely ranges without consideration of factors of safety?

6. As most of our current global socio-economic decision-making processes were developed in a world not threatened by numerous potential Earth Systems tipping points; why do we continue to use such decision-making processes as GMSTA rapidly approaches tipping points that could be triggered by passing the 1.5C threshold?

7. If key Antarctic marine glaciers can pass the point of no return (with regard to stability) when the increase in the Southern Ocean's average CDW temperature and upwelling conditions are effectively irreversible; why do we collectively insist on waiting to actually witness MICI-types of failures before giving decision makers the information that they need to take effective action?

That is enough philosophizing for now.

[AbruptSLR]

I have previously noted that a potential collapse of the Thwaites Glacier (in coming decades) would trigger a rapid warming & upwelling of CDW over the continental shelves of West Antarctica (see Reply #1812).  However, I did not mention then that the marine glaciers in the Bellingshausen Sea, & particularly the Ferrigno Glacier) rest in deep bed rifts that represent potential seaways from the Bellingshausen Sea to both the Amundsen Sea Embayment and the Weddell Sea.  In this regard, while first following reference, abstract and first attached image are generic in nature; the boundary conditions (which are comparable to that for the Ferrigno Glacier) assumed in this work indicate that "subglacial cavities" (or "ice cavities" as noted on the figure) are likely to grow in the Bellingshausen coastal sector, in a comparable fashion to the advective driven "subglacial cavity" that is extending beneath PIG from the PIIS:

On the Role of Coastal Troughs in the Circulation of Warm Circumpolar Deep Water on Antarctic Shelves

by: Pierre St-Laurent, John M. Klinck and Michael S. Dinniman; 2012, JPO.

Abstract:
"Oceanic exchanges across the continental shelves of Antarctica play an important role in biological systems and the mass balance of ice sheets. The focus of this study is on the mechanisms responsible for the circulation of warm Circumpolar Deep Water (CDW) within troughs running perpendicular to the continental shelf. This is examined using process oriented numerical experiments with an eddy-resolving (1 km) 3–D ocean model that includes a static and thermodynamically active ice shelf. Three mechanisms that create a significant onshore flow within the trough are identified: (1) a deep onshore flow driven by the melt of the ice shelf, (2) interaction between the longshore mean flow and the trough, and (3) interaction between a Rossby wave along the shelf break and the trough. In each case the onshore flow is sufficient to maintain the warm temperatures underneath the ice shelf and basal melt rates of O(1myr−1). The third mechanism in particular reproduces several features revealed by moorings from Marguerite Trough (Bellingshausen Sea): the temperature maximum at mid-depth, a stronger intrusion on the downstream edge of the trough, and the appearance of warm anticyclonic anomalies every week. Sensitivity experiments highlight the need to properly resolve the small baroclinic radii of these regions (5 km on the shelf): simulations at 3 km resolution cannot reproduce mechanism 3 and the associated heat transport."

&
The following linked reference and the second and third attached associated images provide more details of the Ferrigno Rift that leads to the upstream end of the PIG, and thus represents part of a potential future seaway from the Bellingshausen Sea to the Amundsen Sea Embayment.

Robert G. Bingham, Fausto Ferraccioli, Edward C. King, Robert D. Larter, Hamish D. Pritchard, Andrew M. Smith, David G. Vaughan (2012), "Inland thinning of West Antarctic Ice Sheet steered along subglacial rifts", Nature, 487, pages 468–471, DOI: https://doi.org/10.1038/nature11292

https://www.nature.com/articles/nature11292?draft=journal

Abstract: "Current ice loss from the West Antarctic Ice Sheet (WAIS) accounts for about ten per cent of observed global sea-level rise. Losses are dominated by dynamic thinning, in which forcings by oceanic or atmospheric perturbations to the ice margin lead to an accelerated thinning of ice along the coastline. Although central to improving projections of future ice-sheet contributions to global sea-level rise, the incorporation of dynamic thinning into models has been restricted by lack of knowledge of basal topography and subglacial geology so that the rate and ultimate extent of potential WAIS retreat remains difficult to quantify. Here we report the discovery of a subglacial basin under Ferrigno Ice Stream up to 1.5 kilometres deep that connects the ice-sheet interior to the Bellingshausen Sea margin, and whose existence profoundly affects ice loss. We use a suite of ice-penetrating radar, magnetic and gravity measurements to propose a rift origin for the basin in association with the wider development of the West Antarctic rift system. The Ferrigno rift, overdeepened by glacial erosion, is a conduit which fed a major palaeo-ice stream on the adjacent continental shelf during glacial maxima. The palaeo-ice stream, in turn, eroded the ‘Belgica’ trough, which today routes warm open-ocean water back to the ice front to reinforce dynamic thinning. We show that dynamic thinning from both the Bellingshausen and Amundsen Sea region is being steered back to the ice-sheet interior along rift basins. We conclude that rift basins that cut across the WAIS margin can rapidly transmit coastally perturbed change inland, thereby promoting ice-sheet instability."

&

The following linked (open access) reference cites research on four decades of marine glacier grounding line retreat in the Bellingshausen margin (see fourth attached image).  This region contributes significantly to the instability of the WAIS:

Frazer D.W. Christie, Robert G. Bingham, Noel Gourmelen, Simon F.B. Tett & Atsuhiro Muto (22 May 2016), "Four-decade record of pervasive grounding line retreat along the Bellingshausen margin of West Antarctica", Geophysical Research Letters, DOI: 10.1002/2016GL068972


http://onlinelibrary.wiley.com/doi/10.1002/2016GL068972/abstract

Abstract: "Changes to the grounding line, where grounded ice starts to float, can be used as a remotely-sensed measure of ice-sheet susceptibility to ocean-forced dynamic thinning. Constraining this susceptibility is vital for predicting Antarctica's contribution to rising sea levels. We use Landsat imagery to monitor grounding line movement over four decades along the Bellingshausen margin of West Antarctica, an area little monitored despite potential for future ice losses. We show that ~65% of the grounding line retreated from 1990-2015, with pervasive and accelerating retreat in regions of fast ice flow and/or thinning ice shelves. Venable Ice Shelf confounds expectations in that despite extensive thinning, its grounding line has undergone negligible retreat. We present evidence that the ice shelf is currently pinned to a sub-ice topographic high which, if breached, could facilitate ice retreat into a significant inland basin, analogous to nearby Pine Island Glacier."

[AbruptSLR]

While thick portions of large ice shelves like the Ross Ice Shelf, are resistant to hydrofracturing failure, their structural integrity can be abruptly compromised by both tsunamis and infragravity waves, as discussed in the linked reference (& as can be seen from the attached images):

P. D. Bromirski et al. (16 June 2017), "Tsunami and infragravity waves impacting Antarctic ice shelves", JGR Oceans, https://doi.org/10.1002/2017JC012913

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017JC012913

Abstract
The responses of the Ross Ice Shelf (RIS) to the 16 September 2015 8.3 (Mw) Chilean earthquake tsunami (>75 s period) and to oceanic infragravity (IG) waves (50–300 s period) were recorded by a broadband seismic array deployed on the RIS from November 2014 to November 2016. Here we show that tsunami and IG‐generated signals within the RIS propagate at gravity wave speeds (∼70 m/s) as water‐ice coupled flexural‐gravity waves. IG band signals show measureable attenuation away from the shelf front. The response of the RIS to Chilean tsunami arrivals is compared with modeled tsunami forcing to assess ice shelf flexural‐gravity wave excitation by very long period (VLP; >300 s) gravity waves. Displacements across the RIS are affected by gravity wave incident direction, bathymetry under and north of the shelf, and water layer and ice shelf thicknesses. Horizontal displacements are typically about 10 times larger than vertical displacements, producing dynamical extensional motions that may facilitate expansion of existing fractures. VLP excitation is continuously observed throughout the year, with horizontal displacements highest during the austral winter with amplitudes exceeding 20 cm. Because VLP flexural‐gravity waves exhibit no discernable attenuation, this energy must propagate to the grounding zone. Both IG and VLP band flexural‐gravity waves excite mechanical perturbations of the RIS that likely promote tabular iceberg calving, consequently affecting ice shelf evolution. Understanding these ocean‐excited mechanical interactions is important to determine their effect on ice shelf stability to reduce uncertainty in the magnitude and rate of global sea level rise.

Plain Language Summary
A major source of the uncertainty in the magnitude and rate of global sea level rise is the contribution from Antarctica. Ice shelves buttress land ice, restraining land ice from reaching the sea. We present the analysis of seismic data collected with a broadband seismic array deployed on the Ross Ice Shelf, Antarctica. The characteristics of ocean gravity‐wave‐induced vibrations, that may expand existing fractures in the ice shelf and/or trigger iceberg calving or ice shelf collapse events, are described. The mechanical dynamic strains induced can potentially affect ice shelf integrity, and ultimately reduce or remove buttressing restraints, accelerating sea level rise.

[AbruptSLR]

I provide the attached image of the surface ice elevation for the Thwaites Glacier; which show that there would be a lot of gravitational driving force if an MICI-type of failure mechanism were to be initiated in the Thwaites gateway in the coming decades.

[AbruptSLR]

More bad news regarding anthropogenic GHG emissions in the coming decades:

Title: "Fossil Fuel Use in Southeast Asia Is Projected to Increase 60% By 2040"

https://www.motherjones.com/kevin-drum/2019/11/fossil-fuel-use-in-southeast-asia-is-projected-to-increase-60-by-2040/

Extract: "Energy use is projected to increase by half and fossil fuel use is projected to rise by 60 percent. If nothing happens to change this, it will dwarf any reduction in carbon emissions from the developed countries of the West."

[AbruptSLR]

For those whom may have forgotten, the West Antarctic ice shelves lose more ice mass during El Nino events, and as large El Nino events are projected to become more frequent with continued global warming, this is bad for WAIS stability:

F. S. Paolo, L. Padman, H. A. Fricker, S. Adusumilli, S. Howard, M. R. Siegfried. Response of Pacific-sector Antarctic ice shelves to the El Niño/Southern Oscillation. Nature Geoscience, 2018; DOI: 10.1038/s41561-017-0033-0

https://www.nature.com/articles/s41561-017-0033-0

Abstract
Satellite observations over the past two decades have revealed increasing loss of grounded ice in West Antarctica, associated with floating ice shelves that have been thinning. Thinning reduces an ice shelf’s ability to restrain grounded-ice discharge, yet our understanding of the climate processes that drive mass changes is limited. Here, we use ice-shelf height data from four satellite altimeter missions (1994–2017) to show a direct link between ice-shelf height variability in the Antarctic Pacific sector and changes in regional atmospheric circulation driven by the El Niño/Southern Oscillation. This link is strongest from the Dotson to Ross ice shelves and weaker elsewhere. During intense El Niño years, height increase by accumulation exceeds the height decrease by basal melting, but net ice-shelf mass declines as basal ice loss exceeds ice gain by lower-density snow. Our results demonstrate a substantial response of Amundsen Sea ice shelves to global and regional climate variability, with rates of change in height and mass on interannual timescales that can be comparable to the longer-term trend, and with mass changes from surface accumulation offsetting a significant fraction of the changes in basal melting. This implies that ice-shelf height and mass variability will increase as interannual atmospheric variability increases in a warming climate.

[Sciguy]

More bad news regarding anthropogenic GHG emissions in the coming decades:

Title: "Fossil Fuel Use in Southeast Asia Is Projected to Increase 60% By 2040"

https://www.motherjones.com/kevin-drum/2019/11/fossil-fuel-use-in-southeast-asia-is-projected-to-increase-60-by-2040/

Extract: "Energy use is projected to increase by half and fossil fuel use is projected to rise by 60 percent. If nothing happens to change this, it will dwarf any reduction in carbon emissions from the developed countries of the West."

Fortunately solar power is now cheaper than coal and natural gas in southeast Asia. Any forecast where you see coal continuing growth past 2025 should be doubt, and now natural gas is in the same situation as coal.

https://www.reuters.com/article/singapore-energy-solar/rpt-cheaper-solar-power-gains-ground-in-southeast-asia-idUSL3N27H09O

SINGAPORE, Oct 31 (Reuters) - Southeast Asia is accelerating plans to harness energy from the sun in coming years as the cost of generating electricity from some solar power projects has become more affordable than gas-fired plants, officials and analysts said.

The region, where power demand is expected to double by 2040, is striving to expand the share of renewable sources as developing nations seek affordable electricity while battling climate change.

Southeast Asia’s cumulative solar photovoltaic (PV) capacity could nearly triple to 35.8 gigawatt (GW) in 2024 from an estimated 12.6 GW this year, consultancy Wood Mackenzie says.

Among the encouraging signs for the solar industry was a recent auction for a 500 megawatt (MW) solar project in Malaysia of which 365 MW were bid at a price lower than the country’s average gas-powered electricity, said Yeo Bee Yin, minister of energy, science, technology, environment and climate change.

[AbruptSLR]

We should all remember that the sea surface salinity of the Southern Ocean is currently decreasing (due to ice meltwater); which indicates that the associated ice-climate feedback mechanism is already engaged and should increase in the future:

Garcia‐Eidell, C., Comiso, J.C., Dinnat, E., Brucker, L. 2019. Sea Surface Salinity Distribution in the Southern Ocean as Observed from Space Journal of Geophysical Research: Oceans: 2018JC014510 [10.1029/2018jc014510

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JC014510

Abstract
Large‐scale spatial and temporal variabilities of sea surface salinity (SSS) in the Southern Ocean from 2011 to 2017 were studied using products derived from microwave sensors on board Aquarius, Soil Moisture and Ocean Salinity (SMOS), and Soil Moisture Active and Passive (SMAP) satellites. Four products, three from Aquarius and one from SMOS, were evaluated and shown to be generally consistent within 0.3 to 0.6 psu and agree favorably with in situ measurements. However, although the Aquarius products show consistent seasonality of SSS with high values of 34.45 psu in October and low values of 33.40 psu in May, the SMOS and SMAP products lack such seasonal variations. This may be caused by larger uncertainties in the SMOS and SMAP data due in part to the lack of concurrent scatterometer measurements that is used to correct for roughness effects. The four products provide similar spatial distributions of SSS with root‐mean‐square difference from 0.25 to 0.58 psu. Differences among Aquarius products are mainly due to varying salinity retrieval algorithms, smoothing, and masking of sea ice, while the SMOS product showed the highest SSS deviation that is likely due to the bias‐adjustment done on the data set. Our analyses show that SSS in the Southern Ocean region has significant meridional variations with the lowest SSS near the ice edge and highest at lower latitudes. The SSS is also lowest in summer indicating the predominant influence of sea ice and glacial melt, but it stays low near ice edges even during the growth season.

Plain Language Summary
Salinity together with temperature is the key parameters that control the state and circulation of the World's oceans. The large‐scale distribution of the sea surface salinity of the Southern Ocean is quantified for the first time using Aquarius, Soil Moisture and Ocean Salinity, and Soil Moisture Active and Passive satellite microwave data. Seasonal and interannual changes in the distribution as affected by the sea ice cover, surface temperature, and precipitation are evaluated. Comparative studies were done, using four different products that are publicly available, in conjunction with in situ observations to gain insights into the true nature of the distribution and how consistently the sea surface salinity is depicted by the different products. There are general consistencies in the products, and discrepancies are attributed to different algorithms, smoothing techniques, and sea ice masking. Aquarius data are shown to have higher accuracy than Soil Moisture and Ocean Salinity and Soil Moisture Active and Passive products in part because of having concurrent scatterometer that provides accurate correction to roughness effects.

[Sciguy]

I provide the attached image of the surface ice elevation for the Thwaites Glacier; which show that there would be a lot of gravitational driving force if an MICI-type of failure mechanism were to be initiated in the Thwaites gateway in the coming decades.

According to DeConto and Pollard (2016), initiation of MICI requires ocean temperatures around Antarctica to be 2 degrees C higher than today and extensive hydrofracturing (caused by surface melt forming melt ponds that drain through the glacier).

As shown upthread, the oceans around Antarctica are warming very slowly (around 0.05 degrees per decade), so it will be centuries before they hit that 2C threashold.

And it appears that surface melt near the Amundsen Sea (where the Thwaites and Pine Island Glaciers terminate) has been low for the past four decades.  The State of the Climate 2018 report, published September 2019, has a chapter on Antarctica covering the most recent full year of observations (2017/2018) and updates trends from previous reports.

https://www.ametsoc.net/sotc2018/Chapter_06.pdf

Summer sea ice extent in the western Bellingshausen Sea and Amundsen Sea sectors was higher than typical, and was associated with low SSTs and low coastal precipitation. Cool conditions in this sector also contributed to a low ice sheet melt season overall for 2017/18. This low-melt year continues a trend, now spanning from the 1978/79 to 2017/18 seasons, of reduced summer melting that is statistically significant (p < 0.05).

The low melt year of 2017/18 continues a downward trend observed in both melt extent and melt intensity since 1978, trends that are now statistically significant (p < 0.05; Fig. 6.7). Since 1978 melt extent has decreased on average 11 400 km2 per year and the melt index by 294 600 day·km2 per year. Year 2017/18 had the third smallest melt extent and fourth lowest melt intensity in the satellite record (1978–present). These observed negative trends are consistent with previous reports (Liu et al. 2006; Tedesco 2009; Tedesco et al. 2009).

[sidd]

The decrease in melt is for all of antarctica, not the Amundsen/Bellinghausen sea alone. If anyone has a citation  on Amundsen/Bellinghausen melt, that would be useful. I have not the time and energy at the moment to derive those from microwave observation from SSIMS .

sidd

[Rodius]

More bad news regarding anthropogenic GHG emissions in the coming decades:

Title: "Fossil Fuel Use in Southeast Asia Is Projected to Increase 60% By 2040"

https://www.motherjones.com/kevin-drum/2019/11/fossil-fuel-use-in-southeast-asia-is-projected-to-increase-60-by-2040/

Extract: "Energy use is projected to increase by half and fossil fuel use is projected to rise by 60 percent. If nothing happens to change this, it will dwarf any reduction in carbon emissions from the developed countries of the West."

I find comparisons between the Rich countries and Poor countries in total values misleading.
The more accurate method to determine who needs to the most or less is considering the per capita emissions.

It would even be fairer to say we should set the target to get below the global average per capita and adjust the total every year that way.
In 2017 it was 4.91 tonnes per person.
https://edgar.jrc.ec.europa.eu/overview.php?v=booklet2018&dst=CO2pc

This means every country that sits above the per capita target needs to do what is required to get there.

Using this as a benchmark, we can clearly see who needs to do the work.
USA - 15.74
Australia - 16.45
Iceland - 12.23
and so on.

Countries that can increase co2 emissions
India - 1.83
Indonesia - 1.94
Vietnam - 2.29

China was at 7.72.... but they make a lot of stuff for the rich countries, I wonder if we removed the CO2 emissions for manufacturing our stuff whether it would be even half that value left over.

Rich countries are looking for ways to do as little as possible at the expense of those who
have not caused the problem and are doing their fair share while growing.

[nanning]

Thanks for that Rodius .

[AbruptSLR]

The decrease in melt is for all of antarctica, not the Amundsen/Bellinghausen sea alone. If anyone has a citation  on Amundsen/Bellinghausen melt, that would be useful. I have not the time and energy at the moment to derive those from microwave observation from SSIMS .

sidd

As it only takes one sufficiently intensive surface ice melt event to hydrofracture an ice shelf, looking at averages (even for just the ASE) is not good science, as intense surface ice melt events happen more frequently during intense El Nino events as occurred in January 2016.  In this regard, the first attached image comes from the first linked source:

"Scientists stunned by Antarctic rainfall and a melt area bigger than Texas"

https://www.washingtonpost.com/news/energy-environment/wp/2017/06/15/scientists-just-documented-a-massive-melt-event-on-the-surface-of-antarctica/?utm_term=.526054dc4fdf

Extract: "Scientists have documented a recent, massive melt event on the surface of highly vulnerable West Antarctica that, they fear, could be a harbinger of future events as the planet continues to warm.

In the Antarctic summer of 2016, the surface of the Ross Ice Shelf, the largest floating ice platform on Earth, developed a sheet of meltwater that lasted for as long as 15 days in some places. The total area affected by melt was 300,000 square miles, or larger than the state of Texas, the scientists report."
&
The second linked reference finds that: "The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major surface melt events.":

Julien P. Nicolas et. al. (2017), "January 2016 extensive summer melt in West Antarctica favoured by strong El Niño", Nature Communications 8, Article number: 15799, doi:10.1038/ncomms15799

http://www.nature.com/articles/ncomms15799

Abstract: "Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Niño event. The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major melt events."

Furthermore, I repost the second attached image to remind readers that the recent past observed rate of warming of the Southern Ocean is not relevant to a possible MICI-type of event in the WAIS in coming decades, because what matters is the increase in temperature of the warm CDW that is advected over the various continental shelves to the grounding lines of the key West Antarctic marine glaciers (which the second image show will increase by about 1.5C by 2050 as compared to 1960).

[AbruptSLR]

...

According to DeConto and Pollard (2016), initiation of MICI requires ocean temperatures around Antarctica to be 2 degrees C higher than today and extensive hydrofracturing (caused by surface melt forming melt ponds that drain through the glacier).

As shown upthread, the oceans around Antarctica are warming very slowly (around 0.05 degrees per decade), so it will be centuries before they hit that 2C threashold.

...

I addition to the surface meltwater and CDW upwelling information that I provided to sidd in Reply #1828; here I note that:

DeConto & Pollard (2016) only presents the results of early MICI model that makes approximations and assumptions and is currently being updated; and given that the findings indicate at an increase of 2C in the ocean temperatures adjoining the Antarctic marine glaciers/ice shelves, is sufficient to initiate some local MICI mechanisms; but these findings are contingent upon:

1. Their model adequately matching the actual relevant Earth Systems;
2. That ECS is roughly 3C instead of roughly 5C as indicated by preliminary CMIP6 projections;
3. The Thwaites Ice Tongue does not collapse due to its fragility in the next roughly ten years without either hydrofracturing or a 2C increase in the temperature of the adjoining ocean waters.

[AbruptSLR]

….

DeConto & Pollard (2016) only presents the results of early MICI model that makes approximations and assumptions and is currently being updated; and given that the findings indicate at an increase of 2C in the ocean temperatures adjoining the Antarctic marine glaciers/ice shelves, is sufficient to initiate some local MICI mechanisms; but these findings are contingent upon:

1. Their model adequately matching the actual relevant Earth Systems;
...

Selected reasons to believe that the DeConto & Pollard (2016) model may not adequately match the Earth Systems associated with the potential to form a MICI mechanism in the 50-km wide Thwaites gateway include:

1. Their base model of the Antarctic was developed prior to 1998 and thus their representation of the TEIS and the Thwaites Ice Tongue may well match the geometry associated with the first image of these features from 1998; rather than that shown in the second image from 2019 where I have superimposed likely load paths leading into these feature; and I note that the load path with heavy arrows leading from the upstream side of the 'Big Ear' subglacial cavity to the TEIS causes a compressive stress field in the glacial ice upstream of the 'Big Ear' which serves to stabilize the abrupt 145m increase in the ice surface elevation going from the 'Big Ear' upstream to the compressive stress field.

2. The resolution of their continent-scale model is likely not sufficiently refined to include the 'Big Ear' subglacial cavity located directly in the Thwaites gateway leading to the BSB.

3. Their model does not include the tidal amplification of the advection of warm CDW to the grounding line in the Thwaites gateway; which is currently causing the 'Big Ear' subglacial cavity to continue to grow.

4. Their model likely does not include the recent basal ice melting beneath either the TEIS or the Ice Tongue; nor the depressed ice surface elevation over the 'Big Ear'; which subjects the thin ice downstream of the 'Big Ear' to uplift/floatation from hydrostatic water pressure that could cause the currently confined icebergs at the base of the Thwaites Ice Tongue to float away in the coming decades.

[AbruptSLR]

The linked reference indicates that the RIS will slowly continue to thin with or without ocean warming:

Adam J. Campbell, Christina L. Hulbe & Choon-Ki Lee (11 January 2018), "Ice Stream Slowdown Will Drive Long-Term Thinning of the Ross Ice Shelf, With or Without Ocean Warming", Geophysical Research Letters, DOI: 10.1002/2017GL075794

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075794/full

Abstract: "As time series observations of Antarctic change proliferate, it is imperative that mathematical frameworks through which they are understood keep pace. Here we present a new method of interpreting remotely sensed change using spatial statistics and apply it to the specific case of thickness change on the Ross Ice Shelf. First, a numerical model of ice shelf flow is used together with empirical orthogonal function analysis to generate characteristic patterns of response to specific forcings. Because they are continuous and scalable in space and time, the patterns allow short duration observations to be placed in a longer time series context. Second, focusing only on changes that are statistically significant, the synthetic response surfaces are used to extract magnitude and timing of past events from the observational data. Slowdown of Kamb and Whillans Ice Streams is clearly detectable in remotely sensed thickness change. Moreover, those past events will continue to drive thinning into the future."

[AbruptSLR]

Russia will also certainly be exporting Arctic coal to India within a few years:

Title: "India Wants More Russian Coal"

https://www.maritime-executive.com/article/india-wants-more-russian-coal

Extract: "Plans are underway to ship Russian coking coal to India via the Northern Sea Route after a series of meetings in Vladivostok last month.
…
Exporting coal from the Taymyr Peninsula along the Northern Sea Route is a key part of Russian President Vladimir Putin’s plan to develop the Arctic shipping route. His goal for shipping 80 million tons along the Route each year is not expected to be possible without Taymyr coal."

[AbruptSLR]

…
Countries that can increase co2 emissions
India - 1.83
Indonesia - 1.94
Vietnam - 2.29

China was at 7.72.... but they make a lot of stuff for the rich countries, I wonder if we removed the CO2 emissions for manufacturing our stuff whether it would be even half that value left over.

Rich countries are looking for ways to do as little as possible at the expense of those who
have not caused the problem and are doing their fair share while growing.

I am not certain that human nature (whether in the first, or third worlds) will allow modern global society to make the adjustments required to avoid a climate catastrophe in the coming decades:

Title: "Delhi air quality: Judges accuse authorities of 'passing the buck'"

https://www.bbc.com/news/world-asia-india-50285343

Extract: "India's top court has accused state governments of "passing the buck" on air pollution and failing to take action to tackle Delhi's toxic smog.

The Supreme Court said authorities were only interested in "gimmicks", rather than concrete measures to combat pollution levels.

Levels of dangerous particles in the air - known as PM2.5 - are at well over 10 times safe limits in the capital."

[AbruptSLR]

This increases the chances that the world will stay on a BAU pathway for longer than it would have otherwise:

Trump to begin formal withdrawal from Paris climate agreement

https://www.axios.com/trump-paris-climate-agreement-formal-withdrawal-6e3140dd-5b96-474b-a0e8-9c8f8a5b4800.html

Extract: "President Trump got a step closer Wednesday to pulling America out of the Paris climate agreement by sending a withdrawal letter to the United Nations, Secretary of State Mike Pompeo announced in a statement Monday.

Driving the news: While Trump indicated this intention in June 2017, today marks the first day his administration could begin the formal process, which will be completed on Nov. 4, 2020 — a day after the 2020 presidential election.

Why it matters: While today is more procedural than symbolic in nature, the U.S. beginning the exit process is likely to further dampen the 2015 climate deal's aspirations and remove any slim chance that Trump would ever re-engage on the matter, like he suggested in 2017 he would be willing to.
…
If a Democrat wins the White House in 2020, he or she would have to submit a letter to rejoin the accord, at which point there is a 30-day delay. The U.S. could then be back into the agreement as soon as Feb. 21, 2021."

[AbruptSLR]

Per the linked article, the International Thwaites Glacier Collaboration, ITGC, will be sending several teams to McMurdo next week and that the teams will deploy to field between later November 2019 and January 2020.  I will be interesting to learn what they find-out (particularly about the subglacial cavities) this season:

Title: "Land Ice Field Season 2019-2020, Antarctica"

https://thwaitesglacier.org/events/land-ice-field-season-2019-2020-antarctica

Extract: "MELT, TARSAN, GHC, THOR, and TIME teams will depart for McMurdo in early November 2019, and will deploy to the field between late November 2019 and January 2020.

ITGC teams plan to drill through the floating ice at the edge of the ice sheet, install instrumentation to measure the ocean, and use seismic and radar systems to map the ice thickness and the cavity beneath the ice. Teams will also collect sample sediment cores from the sub-ice seabed. A geoscience team will collect rock samples from nearby mountains to examine the past history of the ice sheet. Farther upstream, another field team will investigate the boundary between the fast-flowing ice of Thwaites Glacier and the near-stationary ice next to it."

[Rodius]

…
Countries that can increase co2 emissions
India - 1.83
Indonesia - 1.94
Vietnam - 2.29

China was at 7.72.... but they make a lot of stuff for the rich countries, I wonder if we removed the CO2 emissions for manufacturing our stuff whether it would be even half that value left over.

Rich countries are looking for ways to do as little as possible at the expense of those who
have not caused the problem and are doing their fair share while growing.

I am not certain the human nature (whether in the first, or third worlds) will allow modern global society to make the adjustments required to avoid a climate catastrophe in the coming decades:

Title: "Delhi air quality: Judges accuse authorities of 'passing the buck'"

https://www.bbc.com/news/world-asia-india-50285343

Extract: "India's top court has accused state governments of "passing the buck" on air pollution and failing to take action to tackle Delhi's toxic smog.

The Supreme Court said authorities were only interested in "gimmicks", rather than concrete measures to combat pollution levels.

Levels of dangerous particles in the air - known as PM2.5 - are at well over 10 times safe limits in the capital."

I agree with you about our inability to react in a way that will reduce the catastrophe that is coming our way.

I also agree that India is basically being stupid in regards to using coal for power. The pollution there is shocking.

My point was more about who needs to do the most work in regards to the actions that need to be taken.
In theory, it is not India or SE Asia.

Oddly, India in particular, need to stop using coal and fossil fuels not to reduce their CO2 emissions, they need to do it to vastly reduce their levels of air pollution.
This means they need to do it for local reasons that are unrelated to global CO2 levels, but rather pollution levels.
To me, this benefit is just one more reason to get rid of fossil fuels. Maybe there is motivation for change in this approach.

As an aside..... India looking to Russia is an indication that the Adani mine in Australia is entering the too hard basket. The Govt is getting rather extreme in their efforts to force the Adani mine to start. For example, making it illegal to protest environmental concerns when it affects mining, imprisoning protest organizers (I am aware or 3 protesters serving 2 years each) and looking to create laws that makes insurance companies and banks unable to refuse their business to fossil fuel companies.
Australia is as corrupt as hell.
It also is why I doubt we fail to do enough to avoid global civilizational collapse within the coming decades.

(I will hunt down the links for the above mentioned statements, I thought I had them saved but didnt do it)

Imprisonments for protesting
This is what they want to do - https://www.theguardian.com/australia-news/2019/oct/03/peter-dutton-accused-dictator-urging-welfare-cuts-protesters
This is what they have done so far -
https://www.theguardian.com/australia-news/2019/oct/24/queensland-parliament-passes-laws-to-crack-down-on-climate-protesters
https://www.abc.net.au/news/2019-10-11/extinction-rebellion-protester-eric-herbert-sentenced-probation/11595318

https://www.canberratimes.com.au/story/6470618/morrison-doesnt-like-it-when-the-quiet-australians-start-to-speak-up/

[AbruptSLR]

The linked articles contain some useful color commentary from last years International Thwaites Glacier Collaboration's field trips to the world's 'Most Terrifying Glacier':

Title: "These scientists used small explosions to 'see' under Antarctica and measure how fast a key glacier will melt"

https://www.pri.org/stories/2019-06-11/these-scientists-used-small-explosions-see-under-antarctica-and-measure-how-fast

Extract: "Anandakrishnan called that ridge “Thwaites Glacier’s last defense against warming.” 

“The glacier is stable as long as the grounding line stays on that ridge,” he said. “If it were to step back from that ridge, then it would contribute enormously to sea level.”

Thwaites Glacier itself contains enough ice to raise sea levels by roughly two feet if it melts. But if it collapses, it would destabilize nearby glaciers and could trigger some 11 feet of global sea level rise.

The seafloor inland from the grounding zone ridge slopes downward again in what scientists call a retrograde slope. It’s as if Thwaites were sitting in a giant bowl. If the floating ice shelf where Anandakrishnan and his team camped were to disappear completely and the glacier retreated inland from that ridge, scientists fear there would be little to stop its complete collapse. "

Caption for image: "Crevasses at the grounding zone of Thwaites, where a ridge on the seafloor beneath the ice acts like a brake on the seaward flow of the glacier."

See also:

Title: "The Race to Understand Antarctica’s Most Terrifying Glacier"

https://www.wired.com/story/antarctica-thwaites-glacier-breaking-point/

[AbruptSLR]

...
I agree with you about our inability to react in a way that will reduce the catastrophe that is coming our way.

I also agree that India is basically being stupid in regards to using coal for power. The pollution there is shocking.

My point was more about who needs to do the most work in regards to the actions that need to be taken.
In theory, it is not India or SE Asia.

Oddly, India in particular, need to stop using coal and fossil fuels not to reduce their CO2 emissions, they need to do it to vastly reduce their levels of air pollution.
This means they need to do it for local reasons that are unrelated to global CO2 levels, but rather pollution levels.
To me, this benefit is just one more reason to get rid of fossil fuels. Maybe there is motivation for change in this approach.

As an aside..... India looking to Russia is an indication that the Adani mine in Australia is entering the too hard basket. The Govt is getting rather extreme in their efforts to force the Adani mine to start. For example, making it illegal to protest environmental concerns when it affects mining, imprisoning protest organizers (I am aware or 3 protesters serving 2 years each) and looking to create laws that makes insurance companies and banks unable to refuse their business to fossil fuel companies.
Australia is as corrupt as hell.
It also is why I doubt we fail to do enough to avoid global civilizational collapse within the coming decades.

…

All very valid points.  Thank you for the information & local insights.

[AbruptSLR]

...
All very valid points.  Thank you for the information & local insights.

We should all remember that not only are first and third world government official using 'gimmicks' to appear to be taking action against pollution (including the pollution of GHG emissions) and environmental degradation, when they really are not; but many (most) large companies around the world are using 'greenwashing' to appear to be providing sustainable goods and service; while actually they are spending many times more on greenwashing advertising than what they are spending on research to make our global socio-economic system more sustainable.  Similarly, I believe that both governments and private entities in the first world should be actively providing grants/loans and training/support to allow third world countries to transition to more sustainable economies (including energy conservation, etc.) than they would do without such support:

Title: "Greenwashing"

https://en.wikipedia.org/wiki/Greenwashing

Extract: "The first Earth Day was held on April 22, 1970. This encouraged many industries to advertise themselves as being friendly to the environment. Public utilities spent 300 million dollars advertising themselves as clean green companies. This was eight times more than the money they spent on pollution reduction research."

[AbruptSLR]

…
Similarly, I believe that both governments and private entities in the first world should be actively providing grants/loans and training/support to allow third world countries to transition to more sustainable economies (including energy conservation, etc.) than they would do without such support:

...

While the International Energy Agency (IEA) may be somewhat biased; they do have access to large amounts of data, and per the linked article the IEA's latest data shows that 'global energy efficiency gains are slowing'.  This is important because while producing sustainable energy is valuable, it is even more valuable to use the energy that we produce more efficiently.  In this regard, I believe that one of the best things that the first world could do to fight climate change would be to facilitate the transfer of existing efficient energy systems (including insulation) to third world economies; unfortunately, this concept has been floated for decades but has only been implemented on a limited scale:

Title: "Global energy efficiency gains are slowing"

https://www.axios.com/global-energy-efficiency-homes-cars-size-5ecadac2-b2cb-4df5-95d4-b69531ffb8f9.html

Extract: "Primary energy intensity — that is, amount of energy needed per unit of GDP — improved by just 1.2% in 2018. That's the third consecutive year of declining gains and the slowest improvement since 2010, the agency said.
…
“We can improve energy efficiency by 3% per year simply through the use of existing technologies and cost-effective investments," IEA executive director Fatih Birol said in a statement.

•   "Ambitious policies need to be put in place to spur investment and put the necessary technologies to work on a global scale," he adds."

[blumenkraft]

Crosspost!

Changes in high-altitude winds over the South Pacific produce long-term effects on the Antarctic

“The study provides the first evidence of long-term changes in the high-altitude winds of the southern westerly wind belt over the South Pacific,” explains Dr Frank Lamy. “Our findings indicate closer atmospheric ties between the tropics and mid to high latitudes than in other sectors of the Southern Hemisphere, with consequences for global overturning circulation and the storage of atmospheric CO2 in the ocean.”

The team’s findings are also important with regard to understanding current and especially future large-scale climate mechanisms in the comparatively under-researched Southern Hemisphere. One crucial aspect is the coupling of the tropical Pacific with the source of the global climate phenomenon El Niño Southern Oscillation (ENSO) and the West Antarctic. The data shows that the West Antarctic Ice Sheet’s high sensitivity to ENSO in the Pacific sector, which can be seen in satellite observations made over the past few decades, is most likely also significant over much longer time scales. “A change in the high-altitude winds over the South Pacific in response to the increased frequency and intensity of El Niño events that many climate models predict would reduce the stability of the West Antarctic Ice Sheet, while also negatively impacting CO2 storage in the South Pacific,” says Lamy, putting the findings in perspective.

Link >> https://www.awi.de/en/about-us/service/press/press-release/changes-in-high-altitude-winds-over-the-south-pacific-produce-long-term-effects-on-the-antarctic.html

(The study will be published on November 5, 2019 as an open access article in the online portal PNAS

The original title is: Frank Lamy, John C.H. Chiang, Gema Martínez-Méndez, Mieke Thierens, Helge W. Arz, Joyce Bosmans, Dierk  Hebbeln, Fabrice Lambert, Lester Lembke-Jene, Jan-Berend Stuut: Precession modulation of the South Pacific westerly wind belt over the past million years, Proceedings of the National Academy of Sciences of the United States of America (PNAS)  /doi.org/10.1073/pnas.1905847116)

[AbruptSLR]

Every now and then I feel philosophical, so here goes:

…

I note that if the worlds human population were to be considered to be divided into two groups called 'workers/hosts' and 'exploiters/parasites' then the Red Queen hypothesis would provide many insights as to why our global societies have had such a difficult time making much measurable progress in getting off a Business-as-Usual (BAU) pathway; even when climate change models from the 1960's (including Exxon's) foresaw the path that we have subsequently taken w.r.t. climate change/sustainability.  If one considers GHG emissions as a pollution that the consumer/developer has not paid for then they can be considered as exploiters/parasites on workers/hosts even if they are unborn future generations entitled to a sustainable world such as the exploiters/parasites received from prior generations.  As noted in the linked Wikipedia article this situation (our current situation) is similar to the prisoners dilemma (i.e. we are trapped on a BAU pathway, as the effort for the works/hosts to get off this rat-race/arms-race would give the exploiters/parasites an upper hand long enough to put the works/hosts into bondage):

Title: "Red Queen hypothesis"

https://en.wikipedia.org/wiki/Red_Queen_hypothesis

Extract: "The Red Queen hypothesis (also referred to as Red Queen's, the Red Queen effect, Red Queen's race, Red Queen dynamics) is an evolutionary hypothesis which proposes that organisms must constantly adapt, evolve, and proliferate in order to survive while pitted against ever-evolving opposing organisms in a constantly changing environment, as well as to gain reproductive advantage.

The hypothesis intends to explain two different phenomena: the constant extinction rates as observed in the paleontological record caused by co-evolution between competing species, and the advantage of sexual reproduction (as opposed to asexual reproduction) at the level of individuals.
…
Indeed, an adaptation in a population of one species (e.g. predators, parasites) may change the natural selection pressure on a population of another species (e.g. prey, hosts), giving rise to common antagonistic coevolutions. If this positive feedback occurs reciprocally, a potential dynamic coevolution may result.

The phenomenon's name is derived from a statement that the Red Queen made to Alice in Lewis Carroll's Through the Looking-Glass in her explanation of the nature of Looking-Glass Land:
Now, here, you see, it takes all the running you can do, to keep in the same place.
…
One can apply such arms races to human conflict and interpret them as a prominent cause of conflict. According to Azar Gat, the Red Queen effect arises when two competing groups find themselves in a security dilemma. The security dilemma results when a group takes defensive measures (which possess inherent offensive capabilities) to improve their security, triggering a military arms race. This arms race, much like the example previously referenced, causes each side to consume ever increasing amounts of resources in order to outpace the other and to gain an advantage. If an advantage is gained, the arms race is over and the group with more resources has won. However, typically both sides continue to match each other stride for stride, thus triggering the Red Queen effect, as no matter how many resources each side invests, neither is able to gain an advantage. The situation somewhat resembles the prisoner's dilemma. Neither side can stop the arms race, due to mutual suspicion and fears that the other group will gain a significant tactical advantage. Because of this, the Red Queen effect is a common outcome of inter-human competition and conflict."

Edit: Note that I use the term 'workers' herein because it that more effort to produce a sustainable global socio-economic system than it does to maintain our current largely exploitive global socio-economic system underpinned by the use of fossil fuels.

[AbruptSLR]

Crosspost!

Changes in high-altitude winds over the South Pacific produce long-term effects on the Antarctic

“The study provides the first evidence of long-term changes in the high-altitude winds of the southern westerly wind belt over the South Pacific,” explains Dr Frank Lamy. “Our findings indicate closer atmospheric ties between the tropics and mid to high latitudes than in other sectors of the Southern Hemisphere, with consequences for global overturning circulation and the storage of atmospheric CO2 in the ocean.”

The team’s findings are also important with regard to understanding current and especially future large-scale climate mechanisms in the comparatively under-researched Southern Hemisphere. One crucial aspect is the coupling of the tropical Pacific with the source of the global climate phenomenon El Niño Southern Oscillation (ENSO) and the West Antarctic. The data shows that the West Antarctic Ice Sheet’s high sensitivity to ENSO in the Pacific sector, which can be seen in satellite observations made over the past few decades, is most likely also significant over much longer time scales. “A change in the high-altitude winds over the South Pacific in response to the increased frequency and intensity of El Niño events that many climate models predict would reduce the stability of the West Antarctic Ice Sheet, while also negatively impacting CO2 storage in the South Pacific,” says Lamy, putting the findings in perspective.

Link >> https://www.awi.de/en/about-us/service/press/press-release/changes-in-high-altitude-winds-over-the-south-pacific-produce-long-term-effects-on-the-antarctic.html

(The study will be published on November 5, 2019 as an open access article in the online portal PNAS

The original title is: Frank Lamy, John C.H. Chiang, Gema Martínez-Méndez, Mieke Thierens, Helge W. Arz, Joyce Bosmans, Dierk  Hebbeln, Fabrice Lambert, Lester Lembke-Jene, Jan-Berend Stuut: Precession modulation of the South Pacific westerly wind belt over the past million years, Proceedings of the National Academy of Sciences of the United States of America (PNAS)  /doi.org/10.1073/pnas.1905847116)

For convenience, below you can find a link to a pdf of this cited reference:

https://www.pnas.org/content/pnas/early/2019/10/29/1905847116.full.pdf

[AbruptSLR]

The linked article confirms that October was the warmest such month on record, and that 2019 is now certain to be one of the warmest years on record:

Title: "Earth sizzles through October as another month ranks as the warmest on record"

https://www.washingtonpost.com/weather/2019/11/05/earth-sizzles-through-october-another-month-ranks-warmest-record/

Extract: "October was the warmest such month on record globally, narrowly edging out October 2015 for the top spot, according to a new analysis from the European Union’s Copernicus Climate Change Service. The finding, released Tuesday, is significant because it shows that 2019 is certain to be one of the warmest years on record, continuing a trend scientists attribute to increasing amounts of greenhouse gases in the atmosphere due to human activities."

[AbruptSLR]

The linked article confirms that October was the warmest such month on record, and that 2019 is now certain to be one of the warmest years on record:

…

The last strong El Nino was during the 2015-16 season; and in the past such strong El Nino events have been followed by a strong La Nina event within a few years.  However, there have been no strong La Nina event in the 2016-17, 2017-18 and 2018-2019 seasons and now it is clear that there will be no strong La Nina event in the 2019-20 season.  Furthermore, as 2019 could be one of the two warmest years on record, this matches the trend identified in the attached plot by James Hansen that shows that recent increases in the rate of global warming is closely related to a decrease in the frequency of strong La Nina events.

[Hefaistos]

Oddly, India in particular, need to stop using coal and fossil fuels not to reduce their CO2 emissions, they need to do it to vastly reduce their levels of air pollution.
This means they need to do it for local reasons that are unrelated to global CO2 levels, but rather pollution levels.
To me, this benefit is just one more reason to get rid of fossil fuels. Maybe there is motivation for change in this approach.

However, the main culprit for the extreme seasonal Indian air pollution has less to do with fossil fuel: according to government sources about half of pollution is because of subsistence farmers burning their fields.

It has been legally forbidden to burn the grass and crop leftovers, but substistence farming means that you cannot afford to pay for mechanical soil processing. So they will continue to burn their fields.

[Tor Bejnar]

Past Antarctic ice melt reveals potential for 'extreme sea-level rise'

Sea levels rose as much as three metres per century during the last interglacial period as Antarctic ice sheets melted, a pace that could be exceeded in the future, given the turbo-charged potential of human-led climate change.

A study led by Australian National University researchers, published in Nature Communications, found sea-level increases during the last major melt of about 130,000 years ago were faster than models have factored in, even though the "climate forcing" from greenhouse gases is much stronger today.
...

I'm not certain I've found the actual paper, but maybe (see next post).

[Tor Bejnar]

Asynchronous Antarctic and Greenland ice-volume contributions to the last interglacial sea-level highstand

    Eelco J. Rohling, Fiona D. Hibbert, Katharine M. Grant, Eirik V. Galaasen, Nil Irvalı, Helga F. Kleiven, Gianluca Marino, Ulysses Ninnemann, Andrew P. Roberts, Yair Rosenthal, Hartmut Schulz, Felicity H. Williams & Jimin Yu

Nature Communications volume 10, Article number: 5040 (2019)

...
Finally, we infer intra-LIG sea-level rises with event-mean rates of rise of 2.8, 2.3, and 0.6 m c−1. Such high pre-anthropogenic values lend credibility to similar rates inferred from some ice-modelling approaches51. The apparent reality of such extreme pre-anthropogenic rates increases the likelihood of extreme sea-level rise in future centuries.

This research reveals up to 2.8 meters/century sea level rise (without people mucking things up).

Edit:  LIG = The last interglacial

[AbruptSLR]

Given the importance of Milillo et al. (2019), I have decided to repost the reference and abstract and portions of Fig 1 A/B, C, partial D & partial E and Fig 3 A, B & C.  Also, I noted that:

1. Fig 1 panel D shows that the upstream side of the Big Ear subglacial cavity has a negative ice surface height above floatation (meaning that it is experiencing positive buoyance).

2. Fig 3 panel C shows that between 2011 and 2017 the upstream side of the Big Ear subglacial cavity has uplifted about 20m possibly associated with the positive buoyancy that it is experiencing.

P. Milillo, E. Rignot, P. Rizzoli, B. Scheuchl, J. Mouginot, J. Bueso-Bello, and P. Prats-Iraola (2019), "Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica", Sci Adv. 5(1): eaau3433, doi: 10.1126/sciadv.aau3433
PMCID: PMC6353628
PMID: 30729155

https://advances.sciencemag.org/content/5/1/eaau3433
&
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353628/

Abstract: "The glaciers flowing into the Amundsen Sea Embayment, West Antarctica, have undergone acceleration and grounding line retreat over the past few decades that may yield an irreversible mass loss. Using a constellation of satellites, we detect the evolution of ice velocity, ice thinning, and grounding line retreat of Thwaites Glacier from 1992 to 2017. The results reveal a complex pattern of retreat and ice melt, with sectors retreating at 0.8 km/year and floating ice melting at 200 m/year, while others retreat at 0.3 km/year with ice melting 10 times slower. We interpret the results in terms of buoyancy/slope-driven seawater intrusion along preferential channels at tidal frequencies leading to more efficient melt in newly formed cavities. Such complexities in ice-ocean interaction are not currently represented in coupled ice sheet/ocean models."

Caption for the first image (Fig 1): "Thwaites Glacier, West Antarctica.
(A) Map of Antarctica with Thwaites Glacier (red box). (B) Shaded-relief bed topography (blue) with 50-m contour levels (white) (16), grounding lines color-coded from 1992 to 2017, and retreat rates for 1992–2011 (green circle) versus 2011–2017 (red circle) in kilometer per year. Thick yellow arrows indicate CDW pathways (32). White boxes indicate outline of figs. S1 and S2 (C) DInSAR data for 11 to 12 and 27 to 28 April 2016, with grounding lines in 2011, 2016, and 2017 showing vertical displacement, dz, in 17-mm increments color-coded from purple to green, yellow, red, and purple again. Points A to F are used in Fig. 2. (D) Height of the ice surface above flotation, hf, in meters. (E) Change in ice surface elevation, dh, between decimal years 2013.5 and 2016.66 color-coded from red (lowering) to blue (rising). (F) Ice surface speed in 2016–2017 color-coded from brown (low) to green, purple, and red (greater than 2.5 km/year), with contour levels of 200 m/year in dotted black."

Caption for the second image (Fig 3): "Ice thickness change of Thwaites Glacier.
(A) Ice surface elevation from Airborne Topographic Mapper and ice bottom from MCoRDS radar depth sounder in 2011, 2014, and 2016, color-coded green, blue, and brown, respectively, along profiles T1-T2 and (B) T3-T4 with bed elevation (brown) from (16). Grounding line positions deduced from the MCoRDS data are marked with arrows, with the same color coding. (C) Change in TDX ice surface elevation, h, from June 2011 to 2017, with 50-m contour line in bed elevation and tick marks every 1 km."