Ice Apocalypse - Multiple Meters Sea Level Rise

[AbruptSLR]

How far are we away from proof of concept with MICI? It seems like we are making heaps of progress with measuring the topography beneath the ice and water temperature / salinity / depth.

I'm anticipating the day when scientists can tell us that a specific retrograde grounding line has been breached and warm water is at the base of an 800+ meter deep ice cliff so we can all follow along in real time.

Correct me if I'm wrong, but I think MICI would be a function of the speed at which the warm water lifts the ice off the bedrock. The surface ice instability kicks in when the base begins to float, no?

I realize that these are very remote places which makes observation challenging but there is also huge public interest. Any ice gurus know when we'll hit an important grounding line?

First, you are wrong about: "... warm water lifts the ice off the bedrock.  The surface ice instability kicks in when the base begins to float, no?"  In the attached image, the word 'Heat' represents the 'warm water', which melts the underside (basal ice) of the ice shelf, which both causes the grounding line to retreat (which in a retrograde seabed increases the height of the future ice cliff) and reduces the thickness of the ice shelf itself (which makes it less stable).  The ice-cliff failure mechanism itself is causes by splitting tension in the ice upstream of the cliff (see the notch in the lower panel, as ice has a low tensile strength).  However, it is true for ice cliffs that fail in a 'slump' mode, the spitting tensile in the upper ice, cause it to slump off about the mid-height of the cliff face (to form one iceberg), and then buoyance then does uplift the lower chunk of ice to become another iceberg. I recommend that you read some of the linked papers on MICI in this thread.

Second, regarding when an ice sheet model with MICI subroutines will be accepted by consensus climate scientists, I recommend that you use the links in Reply #824 to track the 'International Thwaites Glacier Collaboration' and the DOMINOS program, & to make this easier for readers, I provide the following extract from that post:

Extract: "Now that the field phase of the International Thwaites Glacier Collaboration is complete, I can recommend periodically monitoring the linked websites in the coming weeks & months for updates as the field data is analyzed from the eight associated projects (see the attached image):

Title: "The International Thwaites Glacier Collaboration"

https://thwaitesglacier.org/
&
https://thwaitesglacier.org/projects

Extract: "UK and US scientists are collaborating to investigate one of the most unstable glaciers in Antarctica, the Thwaites Glacier, roughly the same size as Florida or Britain."

See also:

For the project Twitter site, see:

https://twitter.com/GlacierThwaites?ref_src=twsrc%5Etfw%7Ctwcamp%5Eembeddedtimeline%7Ctwterm%5Eprofile%3AGlacierThwaites&ref_url=https%3A%2F%2Fthwaitesglacier.org%2F

Also, I note that both Jeremy Bassis & Doug Benn are involved in the DOMINOS project & thus this hierarchical approach to computer modeling will certainly include ice-cliff failure mechanisms.

Title: "Disintegration of Marine Ice-sheets Using Novel Optimised Simulations (DOMINOS)"

https://thwaitesglacier.org/projects/dominos
"

Edit, regarding slumping see:

Byron R. Parizek et al. Ice-cliff failure via retrogressive slumping, Geology (2019). DOI: 10.1130/G45880.1

https://pubs.geoscienceworld.org/gsa/geology/article/569567/Icecliff-failure-via-retrogressive-slumping

[AbruptSLR]

…
Any ice gurus know when we'll hit an important grounding line?

I suspect that local ice cliff failures near the base of the Thwaites Ice Tongue (see the first two images) will begin sometime between 2025 and 2033, and will be initiated due to influences from Super El Nino events in that timeframe.  I further suspect that it would then take at least until around 2040 to become more widespread in the Thwaites Glacier gateway (as I do not expect the Eastern Thwaites Ice Shelf to collapse before then):

Yu, H., Rignot, E., Morlighem, M., & Seroussi, H. (2017). Iceberg calving of Thwaites Glacier, West Antarctica: full-Stokes modeling combined with linear elastic fracture mechanics. The Cryosphere, 11(3), 1283, doi:10.5194/tc-11-1283-2017

https://www.the-cryosphere.net/11/1283/2017/tc-11-1283-2017.pdf
https://www.the-cryosphere.net/11/1283/2017/tc-11-1283-2017-assets.html

Edit: As shown in the third attached image, the floating ice at the base of the Thwaites Ice Tongue is already highly fractured; which is why I believe that this area could expose a base ice cliff face (with a freeboard over 100m) due to the local ocean current flushing action associated with Super El Ninos in the 2025 to 2033 timeframe.

[AbruptSLR]

As a reminder (of earlier posts on this topic), the linked reference discusses complexities in Thwaites ice-ocean interaction that are not currently represented in coupled ice sheet/ocean model, and which produced newly enlarged basal ice cavities near the grounding line of the Thwaites Ice Tongue.  Such cavities contribute to a local destabilization of the grounded ice in this area:


P. Milillo et al. (30 Jan 2019), "Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica', Science Advances, Vol. 5, no. 1, eaau3433, DOI: 10.1126/sciadv.aau3433

https://advances.sciencemag.org/content/5/1/eaau3433

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 attached 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."

[Sleepy]

Adding to ASLR's post above, an mp4 I made of the NASA animation attached below.

_{Changes in surface height at Thwaites Glacier's grounding line, 2011 to 2017, with sinking areas in red and rising areas in blue. The growing cavity (red mass, center) caused the greatest sinking. The mottled area (bottom left) is the site of extensive calving. Contours show bedrock topography. Credit: NASA/JPL-Caltech}

Also, AGGI is now updated with 2018 numbers:
https://www.esrl.noaa.gov/gmd/aggi/aggi.html

Edit; mp4 messed up so I had to redo it.

[Rich]

Thank you ASLR. I'll spend some time reading this.

[Sleepy]

Glacial cycles simulation of the Antarctic Ice Sheet with PISM – Part 1: Boundary conditions and climatic forcing.
https://www.the-cryosphere-discuss.net/tc-2019-71/

Glacial cycles simulation of the Antarctic Ice Sheet with PISM – Part 2: Parameter ensemble analysis.
https://www.the-cryosphere-discuss.net/tc-2019-70/

Reference PISM simulation of the Antarctic Ice Sheet over the past 210 kyr, mp4 at this link:
https://av.tib.eu/media/41779

[AbruptSLR]

Some people think that this thread is too doom and gloom; so I provide the following link to an article on potential progress in the EU to implement a 'Carbon Fee and Dividend' program as supported by James Hansen:

Title: "Introducing a new citizens initiative for carbon pricing in Europe"

https://skepticalscience.com/Introducing-citizens-initiative-carbon-pricing-europe.html

Extract: "A new European Citizens’ Initiative (ECI) called “The fast, fair and effective solution to climate change” was launched on May 6. The proposal asks that the European Commission introduce a carbon-pricing policy known as Carbon Fee and Dividend at the European Union level. The European Commission registered the proposal earlier this month.

Organizers behind the initiative now have one year until May 6, 2020 to gather the 1 million signatures needed for the European Commission to consider the proposal.

Scientists and economists agree: Putting an increasing price on pollution and giving the returns to households works. A steadily increasing price on fossil fuels will reduce pollution by leading companies and consumers to choose cleaner, cheaper options. All money collected would be returned fairly and for example every month to citizens as a dividend. Most low- and middle-income families will be better off by this policy"

[Tim]

Except you better watch closely how this tax is actually implemented in its details. In Alberta Canada, we have a carbon tax, but it wasn't implemented in line with Hansen's vision at all, where the taxing of large emitters would create a dividend so large that those households you mention would be able to buy solar panels and electric cars with it. Instead, the largest emitters are exempt from the tax and placed under the easily gamed cap and trade system, which has made the dividend cheque we receive pitifully small because the big money source Hansen was aiming at with his idea is exempt, which effectively negates Hansen's concept.

Then, what's happened on top of all that, is that the energy companies have all still cried wolf politically, about a tax which they are actually exempt from, and raised their prices beyond even what those small dividend cheques provided to families, effectively hoovering up all those cheques from the households and placing them into their own pockets instead.

The devil is in the details. In Alberta, the tax has left households net poorer, and in even less of a position to buy alternatives.

Hansen envisioned a culture that actually wanted to solve climate change. He forgot to account for the psychopaths that run and game the system, who are finally only now going to implement the tax because all the Davos people got together and figured out how to game it. Just because they're calling it a carbon tax and dividend program, doesn't mean it's Hansen's vision. All they've done is figured out how to game it is all. Nobody in Alberta's contracting economy is able to buy a solar panel or an electric car with the $120 dollars every three months that we get, especially when our energy costs, overt and hidden, just went up by four times that amount by the companies who don't even pay the tax. It's a total fail here because it was gamed to change Hansen's vision into something he wasn't envisioning at all, which is what corporations and their governments do with ideas.

The devil is in the details.

[AbruptSLR]

...
The devil is in the details.

Tim,

Thank you for your observations of how adult bullshit has been leading us all on a path to climate breakdown for decades.  As James Hansen have communicated for decades the solutions to climate change are well known, it is clearly adult dishonesty that has prevented the implementation of even building a firm foundation for effective climate action (such as Hansen's Carbon Fee and Dividend program).

While not to highjack this thread I have observed that unless adult climate change bullshitters are shown a plan to effectively deal with climate change, they will continue to obstruct climate action.  Therefore, I link to an article on the youth movement and climate action, as it is harder to pervert someone like Greta Thunberg, and at least EU leaders are seeing the reality of this current situation:

Title: "The Kids Are Taking Charge of Climate Change"

https://foreignpolicy.com/2019/04/10/the-kids-are-taking-charge-of-climate-change/

Extract: "“We’ve been telling the politicians exactly this for years, and they brushed us off. But the young people, they’re honest, innocent in a way, and speak straight to the problems, which they didn’t create but will have to pay for.” There’s more action on the political level in the last month than he has seen in a decade, he said, even if there has been no overhaul of policy yet. “If the politicians don’t act,” Quaschning said, “they’ll lose this younger generation. They’re worried.”
…
The shift in discourse may not have changed policy yet, but it is obviously wind in the sails of the pro-climate voices in Merkel’s cabinet, the EU, and elsewhere. Germany’s environment minister, Svenja Schulze, will be heading up a new climate cabinet that will coordinate emissions reduction efforts across various ministries to reach the country’s 2030 climate targets, namely 55 percent reduction of emissions by 2030, compared with 1990 levels. The government will develop a climate law to chart the way, which Spiegel magazine reported this week may include a serious tax on carbon, which hadn’t originally been in the plans."

Best,
ASLR

[Rich]

Some people think that this thread is too doom and gloom;"

.
The truth of climate change is mostly gloomy. Someone has to tell the truth.

I value what I'm finding here.

BTW - the equations in that SLR paper on crevasses at Thwaites are way above my pay grade. I'll just infer that Thwaites is one of the prime spots where we'll see MICI proved or disproved in the intermediate future.

For what it's worth, I've watched a bunch of YouTube videos with Eric Rignot. He comes across as pretty credible and a good example of a scientist who is doing his best to wake people up.

[Tim]

@AbruptSLR

Just watch for those two gaming strategies I outlined. To summarize, price controls are absolutely required or corporations will just gobble up those dividend cheques for themselves. And the large emitters must not be exempted from the tax, because that's the actual source of the money Hansen was eyeballing. Without them contributing to the tax, the dividend is a ridiculous pittance and not what Hansen envisioned at all.

You need price controls to protect the dividend cheque from being stolen, and large emitters participating in the tax in order to make the dividends large enough to matter.

Watch for it, because with those tiny changes, they've totally gamed it. Coming soon to an area near you!

[RoxTheGeologist]

It's my experience so far in California that a 'carbon' tax isn't doing what it's supposed to do, and that is because the oil companies wont sell the farm. I am SERIOUSLY worried that the carbon tax will fail to cut emissions, here is NO guarantee it will work. We don't need some wishy-washy idea of tax and dividend that makes everyone seem like we are saving the planet but it turns out to be greenwashing.

My experience is that the LCFS carbon credits are trading at $183 a ton, and there is the ability to blend biodiesel to B20. If the oil companies wanted to be blending they would be. It's worth around $500m in tax credits. The problem is that all the WILLING participants in the market have already put in blending (6-7% of the market share). The oil companies want to keep selling their assets, the oil in the ground. They will NOT give up the share unless the marketing infrastructure changes. And they own it. If they aren't going to blend at $183 a ton, what chance is there of blending at $20 or $50. None. You have to compensate them for their lost assets, the billions of barrels in the ground, or they wont economically do it. They are businesses and beholden to their share holders.

What we need is a carbon market, and anybody adding GHG to the atmosphere through LUC, Burning Carbon, throwing nitrates on the soil, they have to match the emissions by buying carbon credits that are sequestered. lets start at 2% GHG sequestration, and devise a plan to get to %100 by 2050 using life cycle analysis and strong verification. It's the only way to be sure.

Also note, that means that everyone eating food or using power or gas is going to be responsible for paying to put the GHG back in the ground. We are all going to have to pay to do this. Thinking it can be revenue neutral and we wont have to pay for the environmental damage we are causing seems to be too good to be true. Rant Over

[AbruptSLR]

Some people think that this thread is too doom and gloom;"

.
The truth of climate change is mostly gloomy. Someone has to tell the truth.

I value what I'm finding here.

BTW - the equations in that SLR paper on crevasses at Thwaites are way above my pay grade. I'll just infer that Thwaites is one of the prime spots where we'll see MICI proved or disproved in the intermediate future.

For what it's worth, I've watched a bunch of YouTube videos with Eric Rignot. He comes across as pretty credible and a good example of a scientist who is doing his best to wake people up.

Rich,

I concur that Eric Rignot is a straight shooter, as are all of his co-authors in the linked reference (with Hansen as a lead author); which, does not consider the details of how abrupt ice sheet mass loss might occur, but rather on the consequences:

James Hansen, Makiko Sato, Paul Hearty, Reto Ruedy, Maxwell Kelley, Valerie Masson-Delmotte, Gary Russell, George Tselioudis, Junji Cao, Eric Rignot, Isabella Velicogna, Blair Tormey, Bailey Donovan, Evgeniya Kandiano, Karina von Schuckmann, Pushker Kharecha, Allegra N. Legrande, Michael Bauer, and Kwok-Wai Lo (2016), "Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous", Atmos. Chem. Phys., 16, 3761-3812, doi:10.5194/acp-16-3761-2016

http://www.atmos-chem-phys.net/16/3761/2016/acp-16-3761-2016.html

Abstract: "We use numerical climate simulations, paleoclimate data, and modern observations to study the effect of growing ice melt from Antarctica and Greenland. Meltwater tends to stabilize the ocean column, inducing amplifying feedbacks that increase subsurface ocean warming and ice shelf melting. Cold meltwater and induced dynamical effects cause ocean surface cooling in the Southern Ocean and North Atlantic, thus increasing Earth's energy imbalance and heat flux into most of the global ocean's surface. Southern Ocean surface cooling, while lower latitudes are warming, increases precipitation on the Southern Ocean, increasing ocean stratification, slowing deepwater formation, and increasing ice sheet mass loss. These feedbacks make ice sheets in contact with the ocean vulnerable to accelerating disintegration. We hypothesize that ice mass loss from the most vulnerable ice, sufficient to raise sea level several meters, is better approximated as exponential than by a more linear response. Doubling times of 10, 20 or 40 years yield multi-meter sea level rise in about 50, 100 or 200 years. Recent ice melt doubling times are near the lower end of the 10–40-year range, but the record is too short to confirm the nature of the response. The feedbacks, including subsurface ocean warming, help explain paleoclimate data and point to a dominant Southern Ocean role in controlling atmospheric CO2, which in turn exercised tight control on global temperature and sea level. The millennial (500–2000-year) timescale of deep-ocean ventilation affects the timescale for natural CO2 change and thus the timescale for paleo-global climate, ice sheet, and sea level changes, but this paleo-millennial timescale should not be misinterpreted as the timescale for ice sheet response to a rapid, large, human-made climate forcing. These climate feedbacks aid interpretation of events late in the prior interglacial, when sea level rose to +6–9 m with evidence of extreme storms while Earth was less than 1 °C warmer than today. Ice melt cooling of the North Atlantic and Southern oceans increases atmospheric temperature gradients, eddy kinetic energy and baroclinicity, thus driving more powerful storms. The modeling, paleoclimate evidence, and ongoing observations together imply that 2 °C global warming above the preindustrial level could be dangerous. Continued high fossil fuel emissions this century are predicted to yield (1) cooling of the Southern Ocean, especially in the Western Hemisphere; (2) slowing of the Southern Ocean overturning circulation, warming of the ice shelves, and growing ice sheet mass loss; (3) slowdown and eventual shutdown of the Atlantic overturning circulation with cooling of the North Atlantic region; (4) increasingly powerful storms; and (5) nonlinearly growing sea level rise, reaching several meters over a timescale of 50–150 years. These predictions, especially the cooling in the Southern Ocean and North Atlantic with markedly reduced warming or even cooling in Europe, differ fundamentally from existing climate change assessments. We discuss observations and modeling studies needed to refute or clarify these assertions."


Also, you might want to scroll through the following linked thread:

Title: "Hansen et al paper: 3+ meters SLR by 2100"
https://forum.arctic-sea-ice.net/index.php/topic,1327.0.html

Finally, I provide the attached image, which illustrates the concept of an 'ice plug' temporarily preventing MICI events in key Antarctic marine glaciers & you are correct that the Thwaites Glacier is most at risk of losing its 'ice plug' first in Antarctica.

Best,
ASLR

[wdmn]

Just a quick note on James Hansen and the carbon fee and dividend.

I spoke to James Hansen a few months ago by email, and he reiterated his belief that if countries began implementing a carbon fee and dividend, that the market would make the required adjustments.

I also note that Hansen talks quite a bit about "bullshit" (or greenwashing) in his book "Storms of My Grandchildren."

Please also note that when a carbon fee and dividend is brought in, it tends to come in at a price that is much lower than has been recommended, and is only slowly increased.

Finally, I note that Hansen wrote in 2008:

"If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm, but likely less than that. The largest uncertainty in the target arises from possible changes of non-CO2 forcings."

The paper also warned that continued growth of greenhouse gas emissions for another decade would make it practically impossible to avoid catastrophic effects on the climate system.

Here we are in 2019, having seen another decade of growing emissions, with Mauna Loa CO2 readings recently cracking 415ppm.

Given all of this, while I have tremendous respect for Dr. Hansen, and continue to look to him as one of the most capable and astute climatologists, I can no longer agree with him that a carbon fee and dividend will be sufficient for us to avoid catastrophic warming.

Perhaps if the fee and dividend had been implemented across most of the world 20, or even 10 years ago. But how can we continue to advocate for a solution that, even if implemented tomorrow in most countries, would take 5 or so years -- assuming it was not full of loopholes -- to start working at all?

I believe, along with a growing number of people, that the only reasonable position to advocate for now is for a command economy, such as has occurred during the world wars. If climate change is an emergency, treat it like one. Don't tinker with the markets.

[AbruptSLR]

It's my experience so far in California that a 'carbon' tax isn't doing what it's supposed to do, and that is because the oil companies wont sell the farm. I am SERIOUSLY worried that the carbon tax will fail to cut emissions, here is NO guarantee it will work. We don't need some wishy-washy idea of tax and dividend that makes everyone seem like we are saving the planet but it turns out to be greenwashing.
…

Not all Carbon Fee and Dividend plans are the same (& it is definitely not a cap & trade plan; which Hansen does not support), but the linked plan by 'Citizens' Climate Lobby' is supported by James Hansen and many others:

Title: "The Basics of Carbon Fee and Dividend"

https://citizensclimatelobby.org/basics-carbon-fee-dividend/

[AbruptSLR]

…
I'll just infer that Thwaites is one of the prime spots where we'll see MICI proved or disproved in the intermediate future.
…

While Thwaites is the most important marine glacier to watch, it is physically connected to the Pine Island Glacier; therefore, in the attached image I have sketched a blue line where I speculate that a calving fault will form in the Southwest corner of the Pine Island Ice Shelf. PIIS, sometime in the second half of July 2019.  While I may be wrong, it is at least worth watching, and I note that no consensus climate ice sheet model that I have seen projects such a rapid retreat of the PIIS.

Edit: This image was taken on May 22, 2019

[RoxTheGeologist]

It's my experience so far in California that a 'carbon' tax isn't doing what it's supposed to do, and that is because the oil companies wont sell the farm. I am SERIOUSLY worried that the carbon tax will fail to cut emissions, here is NO guarantee it will work. We don't need some wishy-washy idea of tax and dividend that makes everyone seem like we are saving the planet but it turns out to be greenwashing.
…

Not all Carbon Fee and Dividend plans are the same (& it is definitely not a cap & trade plan; which Hansen does not support), but the linked plan by 'Citizens' Climate Lobby' is supported by James Hansen and many others:

Title: "The Basics of Carbon Fee and Dividend"

https://citizensclimatelobby.org/basics-carbon-fee-dividend/

I left the CCL because I no longer think carbon pricing will work. A command economy is not going to happen.

A system like the LCFS for carbon trading might, where the obligated parties (emitters) have to buy credits from the sequesterers (capture etc) would. It's not a policy I have seen published, please correct me if I am wrong. If there isn't enough sequestration, then it gets expensive to pollute. The argument might be that there will never be enough sequestration (just like the oil companies in California do with the LCFS) but it there isn't then DONT USE THE CARBON becasue that incremental price on the sequestration will be too high. It doesn't mean the end of carbon being taken out of the ground, but we will have to pay to put it back.

[wdmn]

I left the CCL because I no longer think carbon pricing will work. A command economy is not going to happen.

A system like the LCFS for carbon trading might, where the obligated parties (emitters) have to buy credits from the sequesterers (capture etc) would. It's not a policy I have seen published, please correct me if I am wrong. If there isn't enough sequestration, then it gets expensive to pollute. The argument might be that there will never be enough sequestration (just like the oil companies in California do with the LCFS) but it there isn't then DONT USE THE CARBON becasue that incremental price on the sequestration will be too high. It doesn't mean the end of carbon being taken out of the ground, but we will have to pay to put it back.

I know we're drifting back off topic, but to me your logic is a bit strange. The idea that companies will not use the carbon is completely dependent on whether governments are willing to put in place a system that will have high enough costs to cause that (i.e. that governments are strong enough to see their way out of the prisoners dilemma and stop caving to pressure). If the government is strong enough to do that, I don't see why a temporary command (war) economy is an impossibility. Both require the same commitment to actually treating the situation as an emergency that does not allow remaining reserves to be used. So either both are possible, or both are impossible. If both are impossible, we're all screwed. If both are possible, the question is what would work better? To me the obvious answer is the one that doesn't have any delay in response, or room for scamming or finding loopholes, etc.

[Sleepy]

Slideshare by Glen Peters.
https://www.slideshare.net/GlenPeters_CICERO/were-so-fucking-late
Adding four selected images below.

[Lennart van der Linde]

Levermann et al 2019 draft open for discussion, on Antarctic contribution to SLR:
https://www.earth-syst-dynam-discuss.net/esd-2019-23/

"For the so-called business-as-usual warming path, RCP-8.5, we obtain a median contribution of the Antarctic ice sheet to global mean sea-level rise within the 21st century of 17 cm with a likely range (66-percentile around the mean) between 9 cm and 36 cm and a very likely range (90-percentile around the mean) between 6 cm and 59 cm. For the RCP-2.6 warming path which will keep the global mean temperature below two degrees of global warming and is thus consistent with the Paris Climate Agreement yields a median of 13 cm of global mean sea-level contribution. The likely range for the RCP-2.6 scenario is between 7 cm and 25 cm and the very likely range is between 5 cm and 39 cm. The structural uncertainties in the method do not allow an interpretation of any higher uncertainty percentiles. We provide projections for the five Antarctic regions and for each model and each scenario, separately. The rate of sea level contribution is highest under the RCP-8.5 scenario. The maximum within the 21st century of the median value is 4 cm per decade with a likely range between 2 cm/dec and 8 cm/dec and a very likely range between 1 cm/dec and 13 cm/dec."

[AbruptSLR]

At the risk of being imprecise, I present four images in this post and four images in the next post, in an attempt to get readers oriented in the area where I first expect ice cliff failures for Thwaites Glacier between to bed areas that I have labelled Big Ear and Little Ear in this series of images.

The first image comes from Kim et al. (2018).
https://www.mdpi.com/2072-4292/10/8/1236

The second image comes from Tinto Bell (2011), that shows the bed trough leading to the BSB

The third and fourth images show the alignment A-B that Rignot believes has low stability

[AbruptSLR]

As a follow on to my last post, I present four images in an attempt to get readers oriented in the area where I first expect ice cliff failures for Thwaites Glacier between to bed areas that I have labelled Big Ear and Little Ear in this series of images.

With a hat tip to Sleepy, the first image shows the ear relative to the growth of the subglacial cavity at the base of the Thwaites Ice Tongue (near the Big Ear)

The second image shows the locations of the Big & Little Ears relative to a collapse of the cavity that lead to a surge of the Thwaites Ice Tongue after January 2012.

The third image shows the location of Big & Little Ears on a Sentinel 1 image from May 23, 2019.  This image shows ice bergs floating near the Little Ear location.

The fourth image shows the bathymetry of the Thwaites Gateway prior to 2013, where the location of the Big & Little Ears is self-evident, so I have not labelled them.

[Sleepy]

Nice, thanks.
Posting this here as well, about DAC but it also outlines the risks and challenges for the US.
https://rhg.com/research/capturing-leadership-policies-for-the-us-to-advance-direct-air-capture-technology/

Last year, global CO2 emissions reached an all-time high. Recent scientific research indicates that global emissions need to reach net-zero between 2045 and 2055 to limit global temperature rise to 1.5 degrees Celsius. DAC technology does not make it possible to bypass the difficult work of reducing emissions. We find that even with break-neck electrification of vehicles, buildings, and industry, unprecedented improvements in energy efficiency, completely decarbonized power generation, and carbon removal from enhanced natural sequestration, DAC technology will be essential for the US to decarbonize by midcentury. Our analysis indicates that for the US to reach net-zero emissions by 2045 (our “100by45” scenarios) between 560 and 1,850 million metric tons of CO2 will need to be removed by DAC technology and then permanently stored underground annually, depending on the availability of other carbon removal options, such as bioenergy with carbon capture and storage (BECCS) and natural sequestration, and the pace of electrification in the transportation, buildings, and industrial sectors.

[Adam Ash]

I wonder if Levermann et al

Levermann et al 2019 draft open for discussion, on Antarctic contribution to SLR:
https://www.earth-syst-dynam-discuss.net/esd-2019-23/
...

have factored in recent titbits like:

A new study of warm seawater seeping into a cavity below the Ross Ice Shelf shows that a key section of the France-size hunk of ice is melting much faster than the rest.

“We’ve identified an especially vulnerable section where the melt rate is 10 times higher than the rest of the ice shelf,” said study co-author Poul Christoffersen, a glaciologist at the University of Cambridge’s Scott Polar Research Institute. The Ross Ice Shelf is considered relatively stable, but Christoffersen said the location of the rapid melting coincided with a “pinning point” — essentially a buttress that holds back flowing ice and lends stability to the entire shelf…

https://www.nbcnews.com/mach/science/new-look-antarctica-s-biggest-ice-shelf-shows-melting-occurring-ncna1001866

[AbruptSLR]

As a follow-on to my posts in Replies #1170 and #1171, on how I expect ice cliff failure mechanism to first initial in the Thwaites Gateway, between what I label in those posts, the Big and Little Ear bed locations.  Furthermore, I believe that within this limited area of the trough that leads directly into the Byrd Subglacial Basin, that ice cliff failure mechanism could be formed sometime between 2028 and 2035, without the need for hydrofracturing, once the ice mélange has been cleared-out from in front of this area.

The first image (of a Landsat-7 photograph from January 2013) shows how many crevasses there were (& are) in the ice between the grounding line (in green & showing the Big Ear) and the caving front (orange line).  This is the ice mélange region at the base of the Thwaites Ice Tongue that I mentioned must be cleared away by warm modified CDW water associated with Super El Nino events that may occur circa 208 & 2035.

The second image shows a computer analysis of projected basal crevasse development in the bottom of the ice shelf in this Big Ear area at the base of the residual Thwaites Ice Tongue.

The third image (from Bassis & Ma 2015) shows how warm modified CDW water can entering into such basal ice shelf crevasse, and then burns through the basal crevasse up to the top surface of the ice shelf.  Furthermore, the second image shows that these basal crevasses for the Thwaites ice shelf near the Big Ear are concentrated at the base of the ice shelf, so that if/when the warm modified CDW burns through the crevasse, this would leave a bear ice cliff that could initial an ice-cliff failure just upstream of the Big Ear.

The fourth image shows that the subglacial ice cavity is growing at the Big Ear (shown in the bottom panel of this image).  The growth of this cavity decreases the stability of the ice shelf in this area.

[AbruptSLR]

As a follow-on to my last post:

The first image reminds readers that there are troughs in the seafloor of the Amundsen Sea Embayment, ASE, that direct the warm modified CDW water from offshore of the local continental shelf to the Thwaites ice shelves (where the CDW both accelerates basal ice melting and when appropriate to burn through basal crevasses in the ice shelves).

The second image reminds readers that the basal melt water from the entire Thwaites Glacier catchment basin is channeled through the bed trough between the Little and Big Ear area, which is dynamically working to grow the subglacial cavity in this area (particularly where the light freshwater meltwater mixes with the relatively dense warm modified CDW).

The third and fourth images reminds readers that the basal meltwater drainage system from beneath the Thwaites Glacier contains subglacial lakes that periodically drain (say every 20 to 25 years).  Furthermore, the last such drainage event (from June 2013 to January 2014) may have been triggered by the partial collapse of the subglacial cavity between the Big & Little Ears sometime in 2012.  Also, I note that the next Thwaites subglacial lake drainage event may happen as early as 2033 to 2038.

[AbruptSLR]

The linked reference adds information to the relationship between two types of ENSOs and Arctic surface temperatures in the boreal winter.  The associated improved understanding of the relationship between ENSO events and Arctic sea ice melting could provide more accurate projections for the risk of an Arctic albedo flip in the coming decades:

Zhiyu Li et al. (2019), "Different effects of two ENSO types on Arctic surface temperature in boreal winter", Journal of Climate, https://doi.org/10.1175/JCLI-D-18-0761.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0761.1

Abstract
The present work investigates different responses of Arctic surface air temperature (SAT) to two ENSO types based on reanalysis datasets and model experiments. We find that eastern Pacific (EP) ENSO events are accompanied by statistically significant SAT responses over the Barents-Kara Seas in February, while central Pacific (CP) events coincide with statistically significant SAT responses over northeastern Canada and Greenland. These impacts are largely of opposite sign for ENSO warm and cold phases. During EP El Niño February, the enhanced tropospheric polar vortex over Eurasia and associated local low-level northeasterly anomalies over the Barents-Kara Seas lead to anomalously cold SAT in this region. Simultaneously, the enhanced tropospheric polar vortex leads to enhanced sinking air motion and consequently reduced cloud cover. This in turn reduces downward infrared radiation (IR), which further reduces SAT in the Barents-Kara Seas region. Such a robust response cannot be detected during other winter months for EP ENSO events. During CP El Niño, the February SAT over northeastern Canada and Greenland are anomalously warm and coincide with a weakened tropospheric polar vortex and related local low-level southwesterly anomalies originating from the Atlantic Ocean. The anomalous warmth can be enhanced by the local positive feedback. Similar SAT signals as in February during CP ENSO events can also be seen in January but they are less statistically robust. We demonstrate that these contrasting Arctic February SAT responses are consistent with responses to the two ENSO types with a series of atmospheric general circulation model experiments. These results have implications for the seasonal predictability of regional Arctic SAT anomalies

[AbruptSLR]

I provide the linked article to remind readers that eight of the most sophisticated ESMs for CMIP6, are projecting ECS values will increase to over 5C in the coming decades, and that
increasing ECS values means increasing climate variability, which means increased risk of a coming abrupt change in climate state (such as occurred in the Mid-Pliocene period due to an Arctic albedo flip, e.g. see my last post).

Title: "New climate models predict a warming surge"

https://www.sciencemag.org/news/2019/04/new-climate-models-predict-warming-surge

Extract: "But a host of global climate models developed for the United Nations' next major assessment of global warming, due in 2021, are now showing a puzzling but undeniable trend. They are running hotter than they have in the past.
…
But in at least eight of the next-generation models, produced by leading centers in the United States, the United Kingdom, Canada, and France, that “equilibrium climate sensitivity” has come in at 5°C or warmer."

[AbruptSLR]

As a follow on to my comments in Reply #1175:

The first image shows the turbulent convective mixing of the warm modified CDW and the fresh basal meltwater in front of an ice cliff in Antarctica.  In my opinion this type of turbulent convection is significantly contribution to the observed expansion of the subglacial cavity in the trough area between the Big and Little Ears of the Thwaites Ice Shelf/Ice Tongue.

The second image shows the conceptual degradation of methane hydrates from the paleo-bed of the retreating paleo-marine ice sheet in the Barents Sea during the last interglacial.  I note that as it is believed that the bed beneath the Thwaites Glacier also contains methane hydrates, and abrupt retreat of the Thwaites grounding line in the relatively shallow Thwaites Gateway, could result in a similar release of methane into the atmosphere from the potential degradation of methane hydrates in the Thwaites Gateway, in the coming decades.

[AbruptSLR]

Climate change is complicated, as is the modeling of its subparts like the Arctic Ocean and the Beaufort Gyre.  In previous posts I have raised the prospect of, in a warming world, the Beaufort Gyre releasing a large volume of relatively freshwater into the North Atlantic Ocean; which would both slow the MOC, and weaken the Arctic's halocline which would cause deeper relatively warm ocean water to rise up in the water column, which would melt more Arctic sea ice.  Clearly, this ice-climate feedback mechanism would serve to increase ECS (by both warming the tropical sea surface temperatures due to the slowing MOC and by the albedo flip associated with the accelerated loss of Arctic sea ice); and thus climate science has begun to focus more on this very real and significant climate risk as illustrated by the numerous related paper collected in the first linked JGR: Oceans Special Issue, and by the associated selected linked references (note the JGR: Oceans Special Issue has too many papers to be summarized in this post):

JGR: Oceans Special Issues (2019), "Forum for Arctic Modeling and Observational Synthesis (FAMOS) 2: Beaufort Gyre phenomenon"

https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)2169-9291.FAMOS2

See also:

Proshutinsky, A., and R. Krishfield (2019), In a spin: New insights into the Beaufort Gyre, Eos, 100,https://doi.org/10.1029/2019EO119765. Published on 08 April 2019.

https://eos.org/editors-vox/in-a-spin-new-insights-into-the-beaufort-gyre

Extract: "Although the Beaufort Gyre is located in the Arctic region, it has impacts on the climate further afield in two ways:
•   First, fresh water accumulates in the Beaufort Gyre which results in a deficit of fresh water flowing into the North Atlantic. This deficit creates the conditions for deep convection of ocean waters and heat release from the ocean to atmosphere in the subpolar regions; it also promotes intensification of the Atlantic Ocean Meridional Circulation (AOMC).
•   Second, when there are prevailing counter-clockwise winds over the Arctic, fresh water released from the Beaufort Gyre region inhibits the processes of deep convection, reduces intensity of the AMOC and results in climate cooling. Such periodical releases of fresh water from the Arctic Ocean, which have occurred in the 1970s, 1980s, and 1990s, are known as ‘Great Salinity Anomalies’ (Dickson et al., 1988; Belkin et al., 1998)."
&

Edward W. Doddridge et al. (01 April 2019), "A Three‐Way Balance in the Beaufort Gyre: The Ice‐Ocean Governor, Wind Stress, and Eddy Diffusivity", JGR Oceans,
https://doi.org/10.1029/2018JC014897

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018JC014897

Abstract: "The Beaufort Gyre (BG) is a large anticyclonic circulation in the Arctic Ocean.  Its strength is directly related to the halocline depth, and therefore also to the storage of freshwater.  It has recently been proposed that the equilibrium state of the BG is set by the Ice-Ocean Governor, a negative feedback between surface currents and ice-ocean stress, rather than a balance between lateral mesoscale eddy fluxes and surface Ekman pumping.  However, mesoscale eddies are present in the Arctic Ocean; it is therefore important to extend the Ice-Ocean Governor theory to include lateral fluxes due to mesoscale eddies.  Here, a non-linear ordinary differential equation is derived that represents the effects of wind stress, the Ice-Ocean Governor, and eddy fluxes.  Equilibrium and time-varying solutions to this three-way balance equation are obtained and shown to closely match the output from a hierarchy of numerical simulations, indicating that the analytical model represents the processes controlling BG equilibration.  The equilibration timescale derived from this three-way balance is faster than the eddy equilibration timescale and slower than the Ice-Ocean Governor equilibration timescales for most values of eddy diffusivity.  The sensitivity of the BG equilibrium depth to changes in eddy diffusivity and the presence of the Ice-Ocean Governor is also explored.  These results show that predicting the response of the BG to changing surface forcing and sea ice conditions requires faithfully capturing the three-way balance between the Ice-Ocean Governor, wind stress and eddy fluxes."

&

Gianluca Meneghello, John Marshall, Jean-Michel Campin, Edward Doddridge, Mary-Louise Timmermans. The Ice-Ocean governor: ice-ocean stress feedback limits Beaufort Gyre spin up. Geophysical Research Letters, 2018; DOI: 10.1029/2018GL080171

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL080171

Abstract
The Beaufort Gyre is a key circulation system of the Arctic Ocean and its main reservoir of freshwater. Freshwater storage and release affects Arctic sea ice cover, as well as North Atlantic and global climate. We describe a mechanism that is fundamental to the dynamics of the gyre, namely, the ice‐ocean stress governor. Wind blows over the ice, and the ice drags the ocean. But as the gyre spins up, currents catch the ice up and turn off the surface stress. This governor sets the basic properties of the gyre, such as its depth, freshwater content, and strength. Analytical and numerical modeling is employed to contrast the equilibration processes in an ice‐covered versus ice‐free gyre. We argue that as the Arctic warms, reduced sea ice extent and more mobile ice will result in a deeper and faster Beaufort Gyre, accumulating more freshwater that will be released by Ekman upwelling or baroclinic instability.

Plain Language Summary
The Beaufort Gyre, located north of Alaska and Canada, is a key circulation system of the Arctic Ocean. Changes in its depth and circulation influence the evolution of the Arctic sea ice cover, the North Atlantic circulation, and the global climate. The gyre is driven by persistent, ice‐mediated winds, accumulating surface freshwater toward the center, deepening the gyre, and spinning up its currents. We describe a mechanism, dubbed here the ice‐ocean governor, in which the interaction of surface currents with the ice regulates the depth of the Beaufort Gyre: The spinning up of the gyre reduces the relative speed between the ocean and the ice, and hence the freshwater accumulation. This competes with, and we argue is more important than, the release of freshwater by flow instability, which moves water from the center toward the periphery. In the current climate the depth and speed of the Beaufort Gyre are mainly set by the governor, but this may change in a warming world where reduced ice cover will render the ice‐ocean governor less effective. The resulting deeper, swifter gyre will likely exhibit more variability in its freshwater storage and flow speeds.

See also:

Title: "Arctic ice sets speed limit for major ocean current"

https://www.sciencedaily.com/releases/2018/10/181017140925.htm

Extract: "There have been a handful of times in the recorded past when the Beaufort Gyre has spilled over, beginning with the Great Salinity Anomaly in the late 1960s, when the gyre sent a surge of cold, fresh water southward. Fresh water has the potential to dampen the ocean's overturning circulation, affecting surface temperatures and perhaps storminess and climate.

Similar events could transpire if the Arctic ice controlling the Beaufort Gyre's spin continues to recede each year.

"If this ice-ocean governor goes away, then we will end up with basically a new Arctic ocean," Marshall says.
…
In this new paper, the researchers studied the interplay of ice, wind, and ocean currents in more depth, using a high-resolution, idealized representation of ocean circulation based on the MIT General Circulation Model, built by Marshall's group. They used this model to simulate the seasonal activity of the Beaufort Gyre as the Arctic ice expands and recedes each year.
They found that in the spring, as the Arctic ice melts away, the gyre is exposed to the wind, which acts to whip up the ocean current, causing it to spin faster and draw down more fresh water from the Arctic's river runoff and melting ice. In the winter, as the Arctic ice sheet expands, the ice acts as a lid, shielding the gyre from the fast-moving winds. As a result, the gyre spins against the underside of the ice and eventually slows down.
…
Marshall and Meneghello note that, as Arctic temperatures have risen in the last two decades, and summertime ice has shrunk with each year, the speed of the Beaufort Gyre has increased. Its currents have become more variable and unpredictable, and are only slightly slowed by the return of ice in the winter.

"At some point, if this trend continues, the gyre can't swallow all this fresh water that it's drawing down," Marshall says. Eventually, the levee will likely break and the gyre will burst, releasing hundreds of billions of gallons of cold, fresh water into the North Atlantic.
…
An increasingly unstable Beaufort Gyre could also disrupt the Arctic's halocline -- the layer of ocean water underlying the gyre's cold freshwater, that insulates it from much deeper, warmer, and saltier water. If the halocline is somehow weakened by a more instable gyre, this could encourage warmer waters to rise up, further melting the Arctic ice."

Edit: It goes without saying that a pulse of cold, relatively fresh, water from the Beaufort Gyre into the North Atlantic, would trigger a bipolar seesaw mechanism that would contribute to the destabilization of key Antarctic marine glaciers.

[Rich]

I'm looking for an educated guess here.

The field of study related to understanding sea level rise has certainly expanded tremendously over the past decade. That trend certainly looks set to continue in the forseeable.

In my imagination, the ability to predict SLR will improve considerably over time as we deploy more and more instruments to gather data and observe the results.

Is there any reason that by 2030 we shouldn't be able to predict SLR 20 years into the future within -/+ 20% with high confidence?

I guess this is a way of getting a sense of what we don't know and our path to filling in the holes that will yield better predictive capability. I know there is no exact answer to my question ..just trying to get a feel when people think the predictive ability will emerge.

[Sleepy]

We are in general, including the experts, notoriously overconfident and optimistic when it comes to predictions.

This article is from 1976, by E.C. Capen and the Society of Petroleum Engineers.
https://doi.org/10.2118/5579-PA

Handling Uncertainty

Our schooling trained us well to handle the certainties of the world. The principles of mathematics and physics work. In Newton's day, force equaled mass times acceleration, and it still does. The physicists, when they found somewhat erratic behavior on the atomic and molecular level, were able to solve many problems using statistical mechanics. The extremely large number of items they dealt with allowed these probabilistic methods to predict behavior accurately.

So we have a dilemma. Our training teaches us to handle situations in which we can accurately predict the variables. If we cannot, then we know methods that will save us in the presence of large numbers. Many of our problems, however, have a one-time-only characteristic, and the variables almost defy prediction.

You may embark on a new project whose technology differs from that used on other projects. Or perhaps your task is to perform a familiar project in a harsh environment. Try to estimate the total cost and completion time. Hard! You cannot foresee everything. And, for some reason, that which you cannot foretell seems to bring forth more ill than good. Hence, the predictions we make are often very optimistic. Even though we see the whole process unfolding and see estimate after estimate turn out optimistic, our next estimate more than likely will be optimistic also.

Also:
https://metasd.com/2012/07/capen-quiz/

Ventana colleague Bill Arthur has been giving the quiz to clients for years. In fact, it turns out that the vast majority of takers are overconfident in their knowledge – they choose ranges that are too narrow, and get only a three or four questions right. CEOs are the worst – if you score zero out of 10, you’re c-suite material.

 

[Rich]

If someone would have told you 50 years ago how good we would become at predicting the path of a hurricane, you probably wouldn't have believed them.

We're going to get there with SLR.

[Sleepy]

50 years ago I watched Neil Armstrong land on the moon (or rather, next month...). It still feels wierd that so many years have passed and even weirder when I see americans today, cheering for the 'unprecedented' accomplishments of SpaceX.

SLR will get there, whether we like it or not.

[Shared Humanity]

If someone would have told you 50 years ago how good we would become at predicting the path of a hurricane, you probably wouldn't have believed them.

We're going to get there with SLR.

Predicting the real time path of a hurricane involves understanding a number of small processes (wind sheer, water temperatures, location of lows, highs and fronts) in a very specific time frame. Predicting SLR involves understanding processes that are linked across the planet and occur over decades, an entire systems analysis. One is far more difficult than the other IMHO.

AbruptSLR's research rich posts here certainly demonstrate this complexity.

I visit this thread daily and always struggle to understand the research that AbruptSLR posts. If it were not for the abstracts and plain language summaries, it would be hopeless.

[Shared Humanity]

One thing I do like to track is the actual measures of SLR. While this is looking back instead of forward the measures clearly show an acceleration of SLR increases. This should not be surprising as all of the processes that contribute to SLR are accelerating as well (global temps, ice sheet melt, glacier speeds etc.)

[Rich]

If someone would have told you 50 years ago how good we would become at predicting the path of a hurricane, you probably wouldn't have believed them.

We're going to get there with SLR.

Predicting the real time path of a hurricane involves understanding a number of small processes (wind sheer, water temperatures, location of lows, highs and fronts) in a very specific time frame. Predicting SLR involves understanding processes that are linked across the planet and occur over decades, an entire systems analysis. One is far more difficult than the other IMHO.

AbruptSLR's research rich posts here certainly demonstrate this complexity.

I visit this thread daily and always struggle to understand the research that AbruptSLR posts. If it were not for the abstracts and plain language summaries, it would be hopeless.

This is a thread about sea level rise. I'm raising an important question about the science of predicting SLR.

I too value ASLR's contributions here and it is only because there is at least one such insightful and connected person on the topic that I ventured out to ask the question. It was a question which was hoping that there would be some expert insight in response.

Nothing personal, but you're not representing yourself as someone who has expertise to shed light on my question yet you are putting yourself in the position of being the arbiter of whether the question is a good one or not.

Let me take a step back and explain why I'm asking the question. Humanity obviously needs this information to plan and to provide motivation to take action. It is only relatively recently (the past decade or so) that we really began to get understand the situation threat more clearly as being related warm ocean circulation reaching the ice sheets at depth.

Regardless of opinion degree of difficulty, the reason we can track hurricanes more accurately is because we recognized it as a priority and applied ourselves to solving it.

Predicting SLR will not be easy, but it is not an insurmountable task. As you indicate, the time dimension of prediction is completely different.

But other aspects of the prediction will not be so much complex as they will be data for you intensive. We know where all the ice is located. We have satellites and radar which can see through the ice and reveal the topography of the earth beneath it. We have equipment that tells us the temperature and salinity of the ocean at depth. We have a pretty damn good idea of how CO2 forcing is increasing ocean temperature in aggregate and (to your point), we need to hone our models to be understand how the ocean circulation is going to deliver that warm water to a targeted set of locations.

My intuition is that we are going to have the will and resources to thoroughly model the 3D space where the majority of the ice is located and interfaces with the ocean. With another decade or so, we'll probably be able to assemble enough observations about things like MICI to reasonably predict ice dynamics. Lots of super smart people are dedicating their lives to answering the question I'm asking.

It's an immeasurably important question and that's why we're going to figure it out. The only question is when?

IMO, this is a perfectly healthy and rational topic to inquire about and discuss, yet somehow I feel like I've triggered the ASIF culture police. If you don't like my question, why not just ignore it?

As a new

[Shared Humanity]

If someone would have told you 50 years ago how good we would become at predicting the path of a hurricane, you probably wouldn't have believed them.

We're going to get there with SLR.

Predicting the real time path of a hurricane involves understanding a number of small processes (wind sheer, water temperatures, location of lows, highs and fronts) in a very specific time frame. Predicting SLR involves understanding processes that are linked across the planet and occur over decades, an entire systems analysis. One is far more difficult than the other IMHO.

AbruptSLR's research rich posts here certainly demonstrate this complexity.

I visit this thread daily and always struggle to understand the research that AbruptSLR posts. If it were not for the abstracts and plain language summaries, it would be hopeless.

Did you even read my response?

This is a thread about sea level rise. I'm raising an important question about the science of predicting SLR.

Yes you are which is why I actually tried to draw a distinction between the degree of difficulty of understanding these two predictions.

I too value ASLR's contributions here and it is only because there is at least one such insightful and connected person on the topic that I ventured out to ask the question. It was a question which was hoping that there would be some expert insight in response.

We are certainly in agreement here as this is what I said about my reasons for visiting this thread daily.

Nothing personal, but you're not representing yourself as someone who has expertise to shed light on my question yet you are putting yourself in the position of being the arbiter of whether the question is a good one or not.

I am certainly not suggesting the question is not a good one and would not have tried to answer it if I thought this was the case.

Let me take a step back and explain why I'm asking the question. Humanity obviously needs this information to plan and to provide motivation to take action. It is only relatively recently (the past decade or so) that we really began to get understand the situation threat more clearly as being related warm ocean circulation reaching the ice sheets at depth.
 

Certainly understanding the impacts of oceans warming at depth is crucial but I am of the opinion there are also other crucial things we need to understand (in situ melt of the Greenland and Antarctic ice sheets, etc.) Many of these processes are also not clearly understood.

Regardless of opinion degree of difficulty, the reason we can track hurricanes more accurately is because we recognized it as a priority and applied ourselves to solving it.
 

Yes.

Predicting SLR will not be easy, but it is not an insurmountable task. As you indicate, the time dimension of prediction is completely different.
 

I did not say it was insurmountable. I, in fact, used the term "far more difficult" and, because of this, I do not think we are close to being able to accurately predict SLR. In fact, well informed scientists have very different estimates of SLR by the end of the century for this very reason.

IMO, this is a perfectly healthy and rational topic to inquire about and discuss, yet somehow I feel like I've triggered the ASIF culture police. If you don't like my question, why not just ignore it?

I actually liked your question which is why I responded. And my attempt to do so is certainly not "triggering the ASIF culture police". In the future, I will be more cautious and careful in responding to your posts. It was not my intent to offend.

[AbruptSLR]

We are in general, including the experts, notoriously overconfident and optimistic when it comes to predictions.

…

The linked scientific reference finds that AR5 (as a reflection of consensus climate science) does not adequately communicate the trur level of climate change risks:

Salvador Herrando-Pérez, Corey J A Bradshaw, Stephan Lewandowsky, David R Vieites. Statistical Language Backs Conservatism in Climate-Change Assessments. BioScience, 2019; 69 (3): 209 DOI: 10.1093/biosci/biz004

https://academic.oup.com/bioscience/article/69/3/209/5382637

Abstract: "The scientific evidence for anthropogenic climate change is empirically settled, but communicating it to nonscientific audiences remains challenging. To be explicit about the state of knowledge on climate science, the Intergovernmental Panel on Climate Change (IPCC) has adopted a vocabulary that ranks climate findings through certainty-calibrated qualifiers of confidence and likelihood. In this article, we quantified the occurrence of knowns and unknowns about “The Physical Science Basis” of the IPCC's Fifth Assessment Report by counting the frequency of calibrated qualifiers. We found that the tone of the IPCC's probabilistic language is remarkably conservative (mean confidence is medium, and mean likelihood is 66%–100% or 0–33%), and emanates from the IPCC recommendations themselves, complexity of climate research, and exposure to politically motivated debates. Leveraging communication of uncertainty with overwhelming scientific consensus about anthropogenic climate change should be one element of a wider reform, whereby the creation of an IPCC outreach working group could enhance the transmission of climate science to the panel's audiences."

[Rich]

It was not my intent to offend.

I'm certainly not suggesting that I know what anyone else's intentions are. I'm not a mind reader and I'm not offended

The question as originally posed was WHEN so be people think the predictibility will emerge?

If I offer up the analogy of hurricane forecasting as a difficult process we've come a long way in all Iong way in solving, it's not necessarily helpful to be told that a 20 year SLR prediction is longer than a 5 day hurricane forecast. Of course, I understand that. Of course, I understand it will be difficult. Of course it's important to look at historical data and I do. I see the same acceleration.

I'm distressed by the problems that young people and future generations are being handed by the willful ignorance of the ruling political class. I'm eager for people to understand that we are headed in the direction of refining this predictive ability.

Even though we see GHG related events affecting people every day, if a million people get nailed at once, that's a small percentage of 7.8B people. We are still living in the era climate abstraction.

The recent SR 1.5 was a jolt which triggered a step up in activism with Greta, XR and the GND but it's not enough yet.

We need to embrace all of the science that exists AND the science that will be forthcoming in the near future to help the world transition from climate abstraction to sober reality.

I know we're going to figure this SLR shit out. I don't what the range is going to be, but when we do, it's probably going to impact financial markets that will impact billions of people. The era of abstraction isn't going to survive that.

The thing that people in a community like ASIF can help with is to reinforce the point that we're heading in the direction of better SLR prediction and the day of reckoning with that isn't in the year 2100. It's going to be coming during baby boomer retirement years

You made a point about "in situ" losses from Greenland and Antarctica. I'm assuming you meant losses from atmospheric heating, but I'm not sure so I was hoping you could clarify.
.
Peace.

[Tor Bejnar]

Re scientists doing better SLR forecasting in the future.  Some things that would affect future SLR (if they happened shortly after the prediction) are things we cannot know today.

• Major volcanic eruptions (or war or meteor strikes)
• major relevant inventions (cheap fission made commercial, cheep and fast-working CO2 sequestration machine, etc.)
• major governments (i.e., USA and China) going all in against AGW

Outside of these types of changes-from-the-status-quo, some models will narrow the window of possibilities for future (30 years from prediction) SL forecasts.

[Tom_Mazanec]

TB: Yeah, war is a new one. A war between India and Pakistan could set AGW back decades at a cost of many millions of lives. Of course, maybe the mass fires would be conflagrations instead of firestorms and the pollution would be an accelerant on AGW, leaving us talking about nuclear summer.

[Rich]

Re scientists doing better SLR forecasting in the future.  Some things that would affect future SLR (if they happened shortly after the prediction) are things we cannot know today.

• Major volcanic eruptions (or war or meteor strikes)
• major relevant inventions (cheap fission made commercial, cheep and fast-working CO2 sequestration machine, etc.)
• major governments (i.e., USA and China) going all in against AGW

Outside of these types of changes-from-the-status-quo, some models will narrow the window of possibilities for future (30 years from prediction) SL forecasts.

This is an off thread post.

No one thinks we should stop planning for the future because of the possibility of a volcano or meteor.

Discovery of cheap fusion or all-in int'l effort isn't going to impact a 20 year SLR forecast. Those things are going to take time to implement.

The warming already baked in for 20 years into the future even assuming a good reduction and in a emissions will give scientists a good idea of how warm the ocean will be. There isn't much we can do today to impact the SLR results of the next 20 years.

We need to make changes today to stop worse things from happening further down the road and committing the system to Eemian era sea levels.

Please don't turn this into a joke.

[Tom_Mazanec]

We need to make changes today to stop worse things from happening further down the road and committing the system to Eemian era sea levels.

Rich, I suspect stopping Eemian sea levels is a train that has already left the station.

[AbruptSLR]

We need to make changes today to stop worse things from happening further down the road and committing the system to Eemian era sea levels.

Rich, I suspect stopping Eemian sea levels is a train that has already left the station.

Paleoclimate scientists seem to recognize great SLR risk than does consensus climate science, as indicated by the linked reference and the accompanying image.  The image shows a comparison of an unreasonable linear (by Alley 2010, in a consensus science effort to discount the risk of abrupt SLR) projected rate of SLR to achieve a eustatic sea level change of five meter by 2100, vs a more feasible 10-year doubling time (by Hansen & Sato 2011) projected rate of SLR to achieve the same change by 2100, Hansen.

Title: "Paleoclimate Implications for Human-Made Climate Change"

http://www.columbia.edu/~jeh1/mailings/2011/20110118_MilankovicPaper.pdf

[Sleepy]

Rich, the real joke here is that there's little we can do to stop further melting glaciers even 200 years ahead. We can improve scientific projections of SLR but that's merely about when and how much.

We could step on the FF-brakes but few are interested. RCP2.6 is dead and this planet will go past two degrees like nothing since almost everything we build today are built using fossil fuels. Even if we succeed with a 100% PV/Wind/EV World, attitudes must change because we still can't create energy or the resources we need for maintaining our present lifestyles in the west (including current infinite growth mentality).

The only option left would be to cut back consumption and use renewables and the electric transports we can afford, as wisely as possible. And that's exactly what westerners don't want. That's also why we have a multitude of different failed incremental solutions and a new 2018 emissions record.

Adding an older comment of mine because I like this graph by Levermann.

It has no timescale, just temperature correlated to SLR.
http://www.pnas.org/content/110/34/13745.full.pdf
Fig 1E attached.

Paleo-Evidence
To compare the model results with past sea-level anomalies for
the temperature range up to 4 °C, we focus on three previous periods for which the geological record provides reasonable constraints on warmer climates and higher sea levels than preindustrial: the middle Pliocene, marine isotope stage 11, and the LIG (Fig. 1E).

[sidd]

Blanchon (2009) which i shall not repost again, shows exactly what episodic sea level rise means. Even Hansen's graf is not as educational. We are in a situation like MWP1A, sea level could quite conceivably rise by a meter every twenty years and that rate could continue for five hundred. Then you could have static sea level for a few hundred and then another pulse.

The only question is how far away are we from MWP1A kinda destabilization ? We don't know, and i am not sure we will find out before it begins. We already see troubling signs in SLR acceleration and WAIS retreat.

I think the drama will come from WAIS. GIS will melt in place, although surfae melt will skyrocket, I do no think Greenland is quite as frightful as marine ice sheets in antarctica

sidd

[Rich]

I have empathy for the fatalist outlook. There is a lot of inertia pulling us toward adverse outcomes. I've certainly dwelled in the space.

Morally speaking, I can't go there. There are children who deserve our solidarity in the fight, even if it's futile. In the absence of certainty, we should fight the best future possible.

If we truly doomed, I still think we have a choice about whether we go out struggling or whether we accept it and give in. Then there's the issue of whether we encourage others to give in as well. Lots of people are doing that but I can't bring myself to endorse that.

I'd encourage others to check out XR or Sunrise Movement and build some community there.

I realize that this is off topic, but every once in a while it's useful to try and connect with our mission. Why are we consumers of climate breakdown information?

[Sleepy]

This thread is about science, risks and reality Rich, then opinions.

<snip>
The recent SR 1.5 was a jolt which triggered a step up in activism with Greta, XR and the GND but it's not enough yet.
<snip>
I know we're going to figure this SLR shit out. I don't what the range is going to be, but when we do, it's probably going to impact financial markets that will impact billions of people.
<snip>

It's pretty much figured out already, apart from the replies posted above, you can also read what Rignot has published back towards 2013 regarding Antarctica, there's plenty of posts on that in here as well.
And Greta was talking before SR15 and XR, check the date here:

Another from the "We Don't Have Time" series (posted earlier in this thread).

A message to all adults out there who are busy defending an obsolete lifestyle.

Edit; added the quotes for clarity.

[AbruptSLR]

One should remember that the Ross Ice Shelf, RIS, not only buttresses key WAIS marine glaciers but also key EASI marine glaciers.  Thus, its potential abrupt loss this century could potentially trigger up to 11.6 m of ice contribution to SLR.  In this regards, the linked reference indicates that the RIS stability is currently in something of a 'Goldie Locks' condition, and that relatively small changes in local conditions might trigger a rapidly rapid reduction in RIS stability:

K. J. Tinto, L. Padman, C. S. Siddoway, S. R. Springer, H. A. Fricker, I. Das, F. Caratori Tontini, D. F. Porter, N. P. Frearson, S. L. Howard, M. R. Siegfried, C. Mosbeux, M. K. Becker, C. Bertinato, A. Boghosian, N. Brady, B. L. Burton, W. Chu, S. I. Cordero, T. Dhakal, L. Dong, C. D. Gustafson, S. Keeshin, C. Locke, A. Lockett, G. O’Brien, J. J. Spergel, S. E. Starke, M. Tankersley, M. G. Wearing, R. E. Bell. Ross Ice Shelf response to climate driven by the tectonic imprint on seafloor bathymetry. Nature Geoscience, 2019; DOI: 10.1038/s41561-019-0370-2

https://www.nature.com/articles/s41561-019-0370-2

Abstract: "Ocean melting has thinned Antarctica’s ice shelves at an increasing rate over the past two decades, leading to loss of grounded ice. The Ross Ice Shelf is currently close to steady state but geological records indicate that it can disintegrate rapidly, which would accelerate grounded ice loss from catchments equivalent to 11.6 m of global sea level rise. Here, we use data from the ROSETTA-Ice airborne survey and ocean simulations to identify the principal threats to Ross Ice Shelf stability. We locate the tectonic boundary between East and West Antarctica from magnetic anomalies and use gravity data to generate a new high-resolution map of sub-ice-shelf bathymetry. The tectonic imprint on the bathymetry constrains sub-ice-shelf ocean circulation, protecting the ice shelf grounding line from moderate changes in global ocean heat content. In contrast, local, seasonal production of warm upper-ocean water near the ice front drives rapid ice shelf melting east of Ross Island, where thinning would lead to faster grounded ice loss from both the East and West Antarctic ice sheets. We confirm high modelled melt rates in this region using ROSETTA-Ice radar data. Our findings highlight the significance of both the tectonic framework and local ocean–atmosphere exchange processes near the ice front in determining the future of the Antarctic Ice Sheet."

See also:
Title: "Study uncovers surprising melting patterns beneath Antarctica's Ross Ice Shelf"

https://www.sciencedaily.com/releases/2019/05/190527111724.htm

Extract: "Using the new map of the seabed under the ice shelf, the team ran a model of ocean circulation and its effect on ice shelf melting. Compared with the Amundsen Sea to the east, where warm water crosses the continental shelf to cause rapid melting of the ice shelves, little warm water reaches the Ross Ice Shelf. In the Ross Sea heat from the deep ocean is removed by the cold winter atmosphere in a region of open water, called the Ross Shelf Polynya, before flowing under the ice shelf. The model showed that this cold water melts deeper portions of east Antarctic glaciers, but it is steered away from the west Antarctic side by the depth change at the ancient tectonic boundary.

In a surprise twist, however, the team found that the polynya also contributes to a region of intense summertime melting along the ice shelf's leading edge. This melting was confirmed in the radar images of the ice shelf's internal structure. "We found that the ice loss from the Ross Ice Shelf and flow of the adjoining grounded ice are sensitive to changes in processes along the ice front, such as increased summer warming if sea ice or clouds decrease," said Laurie Padman, a co-author and senior scientist at Earth and Space Research.

Overall, the results indicate that models used to predict Antarctic ice loss in future climates must consider changing local conditions near the ice front, not just the large-scale changes in the circulation of warm deep water. "We found out that it's these local processes we need to understand to make sound predictions," said Tinto."