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Lennart van der Linde

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1900 on: November 13, 2019, 10:41:35 PM »
Here are the projections for RCP 8.5 from DeConto and Pollard 2016:

https://www.geo.umass.edu/climate/papers2/DeConto2016.pdf

Quote
Antarctica contributes 77 cm of GMSL rise by 2100, and continued loss of the Ross and Weddell Sea ice shelves drives WAIS retreat from three sides simultaneously (the Amundsen, Ross, and Weddell seas), all with reverse-sloping beds into the deep ice-sheet interior. As a result, WAIS collapses within 250 years. At the same time, steady retreat into the Wilkes and Aurora basins... adds substantially to the rate of sea-level rise, exceeding 4 cm yr−1 (Fig. 4c) in the next century, which is comparable to maximum rates of sea-level rise during the last deglaciation.

So in the worst case emissions scenario, which is no longer feasible because we aren't going to burn that much coal, the West Antarctic ice shelves collapse after the Larsen C, which collapses in the 2050s. The Wilkes and Aurora basins would contribute to sea level rise next century, after 2100.

And Rob DeConto has publicly backed off of these projections.

https://www.theatlantic.com/science/archive/2019/01/sea-level-rise-may-not-become-catastrophic-until-after-2100/579478/

Quote
In new work, conducted with three other prominent glaciologists, DeConto and Pollard have lowered some of their worst-case projections for the 21st century. Antarctica may only contribute about a foot of sea-level rise by 2100, they now say. This finding, reached after the team improved their own ice model, is much closer to projections made by other glaciologists... Now their worst-case skyrocketing sea-level scenario seems extremely unlikely, at least within our own lifetimes.

Skeptical Science has a very good overview of MICI.

https://skepticalscience.com/new-light-antarctica-contribution-slr.html

Quote
DeConto says he is not able to comment on it directly as it is undergoing peer review. However, he has presented some preliminary results at the Fall Meeting of the American Geophysical Union (AGU) in December.

So to recap:
- AbruptSLR continues to confuse the timeframes of the original MICI models published in 2016
- The authors of the original MICI models now state that the 2016 projections were too pessimistic
- Other studies have shown that ice flows instead of fails in a brittle manner, which casts doubt on the mechanism needed for MICI to occur.
- Past sea level rise could have occurred without needing the MICI mechanism
- MICI needs hydrofracturing to occur before MICI can occur and yet there are areas in Antarctica where water flows off the ice sheet rather than penetrating through it to create hydrofractures
- Coal is now more expensive than solar and wind power and coal use is expected to peak next decade, so the emission projections of RCP 8.5 from the 2020s through 2100 aren't possible.

Ken,
Wilkes and Aurora reach their maximum rate of ice loss in the next century, but apparently start to contribute significantly already this century, in my understanding of your quotes of DeConto & Pollard.

And while their new results for 2100 seem to be lower than their earlier results, they also warned that after 2100 the rate of ice loss could be even higher than they found earlier, if I remember correctly. Richard Alley also warns for this possibility in this recent news item:
https://insideclimatenews.org/news/12112019/antarctica-ice-shelf-melt-atmospheric-river-thwaites-glacier-ocean-sea-level-rise?utm_source=facebook&utm_medium=social&fbclid=IwAR0gFMMYkF2K6-PP99Dwonon5CJ-E5TsEmSK5oJSuC4B0Bh-0w9HJjC3Nkw

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Alley noted that some research has suggested that, if global warming pushes West Antarctica's towering ice cliffs to collapse, it could raise sea level more than 3 feet by 2100, surging to 50 feet by 2500, from Antarctic ice melt alone.

"That model is sometimes treated as a worst-case scenario, but in fact the model used a maximum calving rate that has briefly been exceeded in Greenland already, and the possibility exists that even faster calving could occur from higher, wider cliffs that could develop in Antarctica," he said.

Even the most recent international assessment of ice loss relies on models that don't account for some of those ice shelf tipping points, he said. "If we're fortunate, and the ice shelves are retained, then these models may be accurate. If we do lose the ice shelves, the models may project less sea level rise than will occur, perhaps by a lot."

Everyone hopes we'll be lucky, but we can't count on that, so the strongest possible mitigation is urgent and preparing for strong adaptation is urgent as well. RCP8.5 may not be likely, but with people like Trump in power we can't be sure either that it will not come to pass. And also with lower RCP's the risks of rapid and large SLR remain substantial, so it seems reasonable to be very aware of those risks and to not underplay them, as has been done for decades now. It seems to me your posts have a tendency to "err on the side of least drama", like many IPCC reports so far, as argued by Brysse et al and others.

gerontocrat

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1901 on: November 14, 2019, 01:13:12 AM »

Second, per the following article, and associated Rignot et al (2019) reference, if DeConto when back and re-calibrated his model values for the EAIS to match Rignot et al. (2019)'s observed values; he would get significantly higher ice mass loss values at much earlier dates.

Title: "Polar Warning: Even Antarctica’s Coldest Region Is Starting to Melt"

https://e360.yale.edu/features/polar-warning-even-antarctica-coldest-region-is-starting-to-melt

Extract: "In January, Rignot and colleagues published a paper that looked back to 1979. Like the IMBIE study, they found an acceleration in ice loss over the continent as a whole: it went up six times over the four decades of their study. But, more strikingly, they could say that East Antarctica was a big player in that loss: from 2009 to 2017, they concluded, West Antarctica accounted for 63 percent of the continent’s ice loss, and East Antarctica accounted for 20 percent — more than the Antarctic Peninsula’s contribution of 17 percent.

In the face of rapid change and limited data, it is extremely challenging to predict what the Antarctic will do in the future. The models, says Rignot, “all have fundamental flaws. None of them are right.” Their resolution is coarse and they don’t include all the physics; plus they are lacking in critical input data. Very little is known, for example, about water temperatures and the seafloor shape off the coast of much of East Antarctica. That affects things like ocean currents and sea ice buildup, both of which affect glacier flow.

For now, DeConto says, his models show that “the East Antarctic is stable for a few decades, but in the high emissions scenarios it starts to become a player in the late 21st century.” But, he adds, “If I went back and put [Rignot’s] numbers in…” He trails off, waving his hands at the potentially large, unknown increase that would cause."

See also:

Eric Rignot, Jérémie Mouginot, Bernd Scheuchl, Michiel van den Broeke, Melchior J. van Wessem, and Mathieu Morlighem (January 22, 2019), "Four decades of Antarctic Ice Sheet mass balance from 1979–2017", PNAS, 116 (4) 1095-1103; https://doi.org/10.1073/pnas.1812883116

https://www.pnas.org/content/116/4/1095
The Rignot et al paper (and its accompanying spreadsheet separated out melt from the annual mass gain from snowfall of about 1,100GT. They found that in many parts of the EAIS things had changed from annual snowfall in excess of melt, i.e. a net mass gain, to annual snowfall less than melt, .e. a net mass loss.

The GRACE + GRACE-FO data  seems to confirm this, especially in the EIS East of the Ross Ice Shelf (data to September 2019 attached).
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1902 on: November 14, 2019, 05:37:17 PM »

The Rignot et al paper (and its accompanying spreadsheet separated out melt from the annual mass gain from snowfall of about 1,100GT. They found that in many parts of the EAIS things had changed from annual snowfall in excess of melt, i.e. a net mass gain, to annual snowfall less than melt, .e. a net mass loss.

The GRACE + GRACE-FO data  seems to confirm this, especially in the EIS East of the Ross Ice Shelf (data to September 2019 attached).

gerontocrat,

Thank you for this helpful analysis, and as many readers can't keep up with the numerous posts in this thread, I re-post Reply #1689 below as it relates to this topic:

Readers who have been following my posts for the past few (six) years know that Eric Rignot has made it clear that:

a) for many decades the SMB for East Antarctic has changed little except for the fact that in the past decade a few extreme precipitation (snowfall) events associated with atmospheric river events have episodically increased the SMB for East Antarctic as illustrated by the Dronning Maud Land events discussed in the two references cited below.

b) While snowfall (and thus SMB) has increased recently in West Antarctica, the added gravitational load from this mass is serving (& will increasing serve to) accelerate glacial ice flow velocities in key marine glaciers in West Antarctica; which in turn is serving to destabilize the WAIS.

The first and second attached images taken from Tsukernik et al:

May 2009 Atmospheric River Event in the Dronning Maud Land
By: Maria Tsukernik, Amanda Lynch, Maya Wei and Irina Gorodetskaya

The first attached image shows the accumulative and per day precipitation in Dronning Maud Land from 1979 to the end of 2011; which indicates exceptional (unusually high) snowfall/accumulation in this area particularly in May of 2009.  The second figure indicates that this (and possibly other subsequent) high precipitation event(s) was/were due to an Atmospheric River event(s) coming from the Indian Ocean tropical region.  While many scientists who have projected low ice mass loss from AIS have grabbed on to this (and possible subsequent) high precipitation event to say that the future accumulation of large amounts of snow in East Antarctica will largely offset the projected future dynamic ice mass loss in West Antarctica, I do not feel good about any such use of this precipitation data as: (a) The atmospheric rivers are not captured in the GCM models used by these reticent researchers; yet they are happy to grab on to field data without a long trend line and which could be a natural fluctuation; and (b) with increasing global warming future atmospheric river events may bring sufficient warm water from the tropics to Antarctica so that the precipitation falls as rain and not snow; which contribute to episodic rapid ice mass loss from any such impacted area.

&

The following reference and abstract provide valuable analysis of weather data from a station in Dronning Maud Land; and provide further insight into the various factors involved in such events. 

Meteorological regimes and accumulation patterns at Utsteinen, Dronning Maud Land, East Antarctica: Analysis of two contrasting years by: I. V. Gorodetskaya, N. P. M. Van Lipzig, M. R. Van den Broeke, A. Mangold,W. Boot, and C. H. Reijmer; JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES, VOL. 118, 1–16, doi:10.1002/jgrd.50177, 2013

Abstract: "Since February 2009, an automatic weather station (AWS) has been operating near Utsteinen Nunatak, north of the Sør Rondane Mountains, in Dronning Maud Land at the ascent to the East Antarctic Plateau. This paper gives an assessment of the meteorological conditions, radiative fluxes, and snow accumulation for the first 2 years of operation, 2009 to 2010, analyzed in terms of meteorological regimes. Three major meteorological regimes— cold katabatic, warm synoptic, and transitional synoptic—are identified using cluster analysis based on five parameters derived from the AWS measurements (wind speed, specific humidity, near-surface temperature inversion, surface pressure, and incoming longwave flux indicative of cloud forcing). For its location, the relatively mild climate at Utsteinen can be explained by the high frequency of synoptic events (observed 41%–48% of the time), and a lack of drainage of cold air from the plateau due to mountain sheltering. During the cold katabatic regime, a strong surface cooling leads to a strong near-surface temperature inversion buildup. A large difference in accumulation is recorded by the AWS for the first 2 years: 235mm water equivalent in 2009 and 27mm water equivalent in 2010. Several large accumulation events during the warm synoptic regime occurring mainly in winter were responsible for the majority of the accumulation in 2009. Mostly, small accumulation events occurred during 2010, frequently followed by snow removal. This interannual variability in snow accumulation at the site is related to the intensity of the local synoptic events as recorded by meteorological regime characteristics."
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Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1903 on: November 14, 2019, 11:10:51 PM »
Let's take a look at RCP 8.5.  Basically, all of the IPCC RCPs look very similar until the 2020s and then diverge rapidly in the rest of the 21st century.



So when you read that we are currently closer to RCP 8.5 then we are RCP 4.5 or RCP 2.6, it sounds pretty alarming.  However, we still have 80 years left in this century.



While I imagine that some readers benefit from your posts, it seems to that:

1. Many readers may very well take your posts on anthropogenic radiative forcing scenarios to mean that they have plenty of time left before they need to take effective action; and if this the case then your posts are increasing the likelihood that society will remain on, or close to, a BAU pathway than we would have without your posts, thus moving us away from the left-tail of the first attached image towards the right tail of that conceptual PDF.

2. If some of my observations about ice-climate mechanisms, and MICI-type of failure modes, prove correct then even if society becomes carbon neutral by 2040 a cascade of ice-climate feedback mechanisms could have a major impact on mankind anyway (see the second image)

Edit: The third image from Hansen et al. (2016) shows a representative temporary increase in planetary energy imbalance for a 5-year Doubling time; which is close to my assumed scenario where at least the Byrd Subglacial Basin sustains a MICI-type of collapse circa 2040.  Such a pulse of the planetary energy imbalance could conceptually trigger the ice-climate cascade illustrated by the second image.

AbruptSLR,

1. You misinterpret my posts.  We need to get off of fossil fuels fast. 

What I'm saying is that we're doing that.  My posts are meant to keep hope alive and to correct the misimpressions that many people on this website have that we're too late.  You can see that just upthread of this post someone linked to a very dubious paper (not peer reviewed and not be a climate scientist) saying that we're all doomed and society is going to collapse.

I think that many people read what you post and assume it's true and come away from here thinking that society is doomed.  If we're doomed to collapse, what would be the point of trying to change anything?

Many of your posts take very speculative or extreme projections and imply that they're definitely going to occur.  I think readers of this forum should be told when you point out extreme right tail risks that the conditions for those events occurring haven't yet been met.

Also, you tend to completely ignore facts that make the extreme right tail risks unlikely to occur.  Case in point, renewables have been less expensive than coal for almost two years now.  Investments in new coal plants have plummeted and retirements of coal power plants have accelerated.  Coal use is projected to peak within a few years and then rapidly decrease afterwards.  Even thought that's been pointed out, you seem to think that we'll still be on the RCP 8.5 scenario when there is no other source of greenhouse gas emissions that can make up for the missing coal emissions.

Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1904 on: November 14, 2019, 11:31:51 PM »
On 2, keep in mind that even if MICI is valid the conditions for it according to DeConto and Pollard are:

An increase in ocean temperatures around Antarctica to 2 degrees above current temperatures and extensive hydrofracturing (lots of surface melt that would allow enough melt water to build up that it would penetrate 100 meter plus ice cliffs).  We're nowhere close to seeing those conditions.

In DeConto and Pollard 2016 they instantaneously raised the temperatures (I'm assuming from a 2015 start date) by 2 degrees.  They also used the RCP 8.5 scenario which keeps ramping up the GHG forcings well beyond what is now projected to occur.  The result was that 40 years later the Larsen C ice shelf at the south end of the Antarctic Pennisula collapses.  Thwaites and PIG are closer to the pole than Larsen C so would not collapse until later.  East Antarctica doesn't begin to contribute significantly to sea level rise until the 2100s in their scenario.

So a projection of MICI starting in Antarctica in the 2040s doesn't appear to be supported by science.  In fact, studies indicate that if we can keep the temperature rise to 1.5 C the WAIS won't collapse.

KiwiGriff

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1905 on: November 14, 2019, 11:46:37 PM »
Quote
when there is no other source of greenhouse gas emissions that can make up for the missing coal emissions.
Such certainty gives you away. 30 years of the IPCC and we have not changed the shape of the keeling curve appreciably.
Coal has mostly been swapped for new gas assets with a fifty year life.
I can think of a few potential sources of greenhouse gas emissions including permafrost melt, burning the Amazon and furtive methane from fracking and faulty infrastructure  that could push us over RCP 8.5
RCP 8.5 is very unlikely but not "impossible" at this point.

On the other hand the lower RCP's always have been impossible being based on technology we do not actually have and the application of which we could not achieve in any reasonable expectation of the  economic and political future. 

Quote
In fact, studies indicate that if we can keep the temperature rise to 1.5 C the WAIS won't collapse.
@1.2 C now  and  0.2C  a decade that's less than two decades away without allowing for warming masked by human induced aerosols.
1.5C is already blown 2C is highly unlikely and 3C probable on our present path.
« Last Edit: November 14, 2019, 11:52:52 PM by KiwiGriff »

Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1906 on: November 15, 2019, 12:08:48 AM »
Quote
when there is no other source of greenhouse gas emissions that can make up for the missing coal emissions.
Such certainty gives you away. 30 years of the IPCC and we have not changed the shape of the keeling curve appreciably.
Coal has mostly been swapped for new gas assets with a fifty year life.
I can think of a few potential sources of greenhouse gas emissions including permafrost melt, burning the Amazon and furtive methane from fracking and faulty infrastructure  that could push us over RCP 8.5
RCP 8.5 is very unlikely but not "impossible" at this point.

On the other hand the lower RCP's always have been impossible being based on technology we do not actually have and the application of which we could not achieve in any reasonable expectation of the  economic and political future. 

Quote
In fact, studies indicate that if we can keep the temperature rise to 1.5 C the WAIS won't collapse.
@1.2 C now  and  0.2C  a decade that's less than two decades away without allowing for warming masked by human induced aerosols.
1.5C is already blown 2C is highly unlikely and 3C probable on our present path.

You're entitled to your opinion.

However, the science on temperature increases says:

https://www.ipcc.ch/sr15/

Quote
Pathways consistent with 1.5°C of warming above pre-industrial levels can be identified under a range of assumptions about economic growth, technology developments and lifestyles

Quote
In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050 (2045–2055 interquartile range).1 For limiting global warming to below 2°C with at least 66% probability CO2 emissions are projected to decline by about 25% by 2030 in most pathways (10–30% interquartile range) and reach net zero around 2070 (2065–2080 interquartile range).

As to natural gas infrastructure, I hope you haven't invested in that Ponzi scheme as the wells, pipelines, power plants and associated infrastructure are going to be stranded assets by 2035.

https://solarmagazine.com/natural-gas-power-stranded-asset-risk-reaches-a-tipping-point/

Quote
atural Gas Power Stranded Asset Risk Reaches a Tipping Point
By Andrew Burger - Oct 07, 2019

Investment risk in new and proposed natural gas power plants is on the rise. The risk of them becoming stranded assets has reached a tipping point, according to two companion reports produced by the Rocky Mountain Institute (RMI).

Sharp declines in the costs and improving performance of clean energy portfolios (CEPs) that include solar and wind power generation, battery energy storage, energy efficiency and utility-customer demand-side response (DSR) by and large have driven the cost-competitiveness of CEPs below that for new natural gas power plants and electricity across the U.S. That includes investments in the latest, highest efficiency combined-cycle power plants, especially new “peaker” plants designed just to start up quickly and meet sudden, unexpected shortfalls in grid supply or spikes in demand, RMI highlights in The Growing Market for Clean Energy Portfolios and Economic Opportunities for a Shift from New Gas-Fired Generation to Clean Energy Across the United States Electricity Industry.

Quote
It will be less expensive to operate new solar and clean energy portfolios than 90% of the proposed combined-cycle natural gas power capacity slated to come online by 2035—some 68 gigawatts’ (GW) worth, according to RMI’s analysis.  And that assumes the pace of clean energy cost declines will slow dramatically and doesn’t consider the impact of prospective climate or renewable energy policies.





sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1907 on: November 15, 2019, 12:15:36 AM »
There seems to be some confusion here. DeConto et al. raised the _ocean_temperature in Amundsen region  by 2C. Most of the discussion here seems to be about global mean temperature increase. While the two are coupled, they are very far from the same thing.

sidd

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1908 on: November 15, 2019, 12:36:31 AM »
There seems to be some confusion here. DeConto et al. raised the _ocean_temperature in Amundsen region  by 2C. Most of the discussion here seems to be about global mean temperature increase. While the two are coupled, they are very far from the same thing.

sidd

Bronselaer et al (2018) used an AIS model that does not account for MICI nor hydro-fracturing (which are not likely to be significant before 2040), nor an ECS of about 5C as projected by many CMIP6 projections.  Nevertheless, at a depth of about -500m (near the grounding lines of most ASE marine glaciers) Bronselaer et al. (2018) show a projected increase of local ocean temperature of about 1.2C between about 2015 and 2080 (see the associated first image); so who knows how high this increase in local ocean temperature would go if they modelled MICI and used a ECS of about 5C.

Furthermore, DeConto & Pollard did not model any of the subglacial cavities (see the second image) nor the fragile condition of the base of the Thwaites Ice Tongue shown in the third image.

Bronselaer, B. et al. (2018) Change in future climate due to Antarctic meltwater, Nature, doi:s41586-018-0712-z

https://www.nature.com/articles/s41586-018-0712-z

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KiwiGriff

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1909 on: November 15, 2019, 12:36:49 AM »
Quote
In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050
And ........our present reality.

edmountain

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1910 on: November 15, 2019, 01:52:21 AM »
1. You misinterpret my posts.  We need to get off of fossil fuels fast. 

What I'm saying is that we're doing that.
...
Your optimism is admirable but I have not seen any data to suggest the world is getting off fossil fuels fast. The only data I have seen suggests that fossil fuel consumption is rising year after year. This is borne out by the inexorable and accelerating climb in CO2 levels as shown by KiwiGriff.

https://www.nationalobserver.com/2019/07/31/opinion/fossil-fuel-burning-leaps-new-record-crushing-clean-energy-and-climate-efforts

Also, you tend to completely ignore facts that make the extreme right tail risks unlikely to occur.  Case in point, renewables have been less expensive than coal for almost two years now.  Investments in new coal plants have plummeted and retirements of coal power plants have accelerated.  Coal use is projected to peak within a few years and then rapidly decrease afterwards.  Even thought that's been pointed out, you seem to think that we'll still be on the RCP 8.5 scenario when there is no other source of greenhouse gas emissions that can make up for the missing coal emissions.
Alas, projections are not facts. And there are plenty of other sources of GHG emissions to replace coal.

Hefaistos

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1911 on: November 15, 2019, 07:52:51 AM »
There seems to be some confusion here. DeConto et al. raised the _ocean_temperature in Amundsen region  by 2C. Most of the discussion here seems to be about global mean temperature increase. While the two are coupled, they are very far from the same thing.

sidd

Always must remember, that the development of climate is first and foremost related to what's going on in the oceans (and the sun obviously). That's where 93% of GW goes. Oceans store something like 99.9% of the surface thermal energy on the Earth, the dry atmosphere contains 0.07% of the energy.
The atmosphere isn't warming the oceans.
To warm the Southern Ocean 2 C requires a lof of heat energy and a lot of time. Currently, mankind has managed to warm the oceans with a trend of approximately 0.04 °C per decade for the upper 700 meters. Or, less than half a degree per century. The warming is much less than that on deeper levels of the oceans.
The Southern Ocean doesn't even seem to be warming if you look at 2m surface temperatures. You can see the effekt of El nino in attached figure, but apart from that there is no positive trend.
SSTs even have a negative trend.
« Last Edit: November 15, 2019, 08:05:32 AM by Hefaistos »

KiwiGriff

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1912 on: November 15, 2019, 08:53:27 AM »


Quote
The Southern Ocean plays a fundamental role in global climate. With no continental barriers, it distributes climate signals among the Pacific, Atlantic, and Indian Oceans through its fast-flowing, energetic, and deep-reaching dominant current, the Antarctic Circumpolar Current. The unusual dynamics of this current, in conjunction with energetic atmospheric and ice conditions, make the Southern Ocean a key region for connecting the surface ocean with the world ocean’s deep seas. Recent examinations of global ocean temperature show that the Southern Ocean plays a major role in global ocean heat uptake and storage. Since 2006, an estimated 60%–90% of global ocean heat content change associated with global warming is based in the Southern Ocean. But the warming of its water masses is inhomogeneous. While the upper 1,000 m of the Southern Ocean within and north of the Antarctic Circumpolar Current are warming rapidly, at a rate of 0.1°–0.2°C per decade, the surface sub­polar seas south of this region are not warming or are slightly cooling. However, subpolar abyssal waters are warming at a substantial rate of ~0.05°C per decade due to the formation of bottom waters on the Antarctic continental shelves. Although the processes at play in this warming and their regional distribution are beginning to become clear, the specific mechanisms associated with wind change, eddy activity, and ocean-ice interaction remain areas of active research, and substantial challenges persist to representing them accurately in climate models.

https://tos.org/oceanography/article/southern-ocean-warming



DK.....


 

Lennart van der Linde

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1913 on: November 15, 2019, 09:41:18 AM »
Hansen et al 2016:
https://pubs.giss.nasa.gov/abs/ha04710s.html

"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 [...] 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."

Silvano et al 2018:
https://advances.sciencemag.org/content/4/4/eaap9467

"Strong heat loss and brine release during sea ice formation in coastal polynyas act to cool and salinify waters on the Antarctic continental shelf. Polynya activity thus both limits the ocean heat flux to the Antarctic Ice Sheet and promotes formation of Dense Shelf Water (DSW), the precursor to Antarctic Bottom Water. However, despite the presence of strong polynyas, DSW is not formed on the Sabrina Coast in East Antarctica and in the Amundsen Sea in West Antarctica. Using a simple ocean model driven by observed forcing, we show that freshwater input from basal melt of ice shelves partially offsets the salt flux by sea ice formation in polynyas found in both regions, preventing full-depth convection and formation of DSW. In the absence of deep convection, warm water that reaches the continental shelf in the bottom layer does not lose much heat to the atmosphere and is thus available to drive the rapid basal melt observed at the Totten Ice Shelf on the Sabrina Coast and at the Dotson and Getz ice shelves in the Amundsen Sea. Our results suggest that increased glacial meltwater input in a warming climate will both reduce Antarctic Bottom Water formation and trigger increased mass loss from the Antarctic Ice Sheet, with consequences for the global overturning circulation and sea level rise."

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1914 on: November 15, 2019, 10:55:46 AM »

 And there are plenty of other sources of GHG emissions to replace coal.

For example, most of the proven crude oil reserves shown in the first attached image, and/or the proven shale gas reserves shown in the second image, could be developed if the price of crude oil were to return to the over $100/barrel range that it was not too long ago:

Title: "Map: The Countries With the Most Oil Reserves"

https://www.visualcapitalist.com/map-countries-most-oil-reserves/

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1915 on: November 15, 2019, 11:14:57 AM »
The first image shows the locations of the Big & Little Ears relative to a collapse near the Little Ear cavity (see Kim et al. 2018) that lead to a surge of the Thwaites Ice Tongue after January 2012, as described in the linked article & associated YouTube video.

Title: "Thwaites Glacier Tongue Major Calving Event, Antarctica"

https://blogs.agu.org/fromaglaciersperspective/2012/10/08/thwaites-glacier-tongue-major-calving-event-antarctica/

Extract: "During the Austral winter between April and September, 2012 the Thwaites Glacier a large outlet glacier of the West Antarctic ice Sheet experienced a major calving event, as was pointed out by a reader on this blog. This is along with Pine Island Glacier often considered the weak underbelly of the ice sheet. MODIS imagery from February, March, September and October is used here to illustrate the event."

&

Title: "thwaites"



&

Furthermore, the 2012 collapse and subsequent surge of the Thwaites Ice Tongue, caused the drainage of four upstream subglacial lakes that kept the ice tongue growing to its current grounded condition.  The second image shows the location of the four Thwaites subglacial lakes that drain between June 2013 and July 2014, just after the local collapse of the subglacial cavities in the Thwaites gateway.  The third image shows that the ice surface elevation above these four Thwaites subglacial lakes dropped as the lakes drained, & the associated outburst of meltwater contributed to the surge of the Thwaites Ice Tongue during this period.

These subglacial lakes typically take about twenty years to refill, so circa 2032 to 2035 they should be ready to push any icebergs out of the Thwaites gateway (thus exposing any ice cliff there at that time) if another subglacial cavity were to collapse near the base of the Thwaites Ice Tongue (say the Big Ear subglacial cavity), which could lead to a subsequent MICI-type of failure of the BSB.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1916 on: November 15, 2019, 01:00:36 PM »
Hansen et al 2016:
https://pubs.giss.nasa.gov/abs/ha04710s.html

"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."

Thanks, Lennart.
I'm just trying to understand how far the quoted developments from Hansen 2016 have gone, as they seem to be a driving mechanism for Antarctic bottom melt.

Above we have seen that SO surface is indeed cooling.
Are lower latitudes warming? No, see attached, we have a negative SST trend in Antarctic seas.
Are we getting increased precipitation in SO? No, see attached, there is no trend there.

I don't see much evidence in satellite data for their claim.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1917 on: November 15, 2019, 01:14:15 PM »
[Are lower latitudes warming? No, see attached, we have a negative SST trend in Antarctic seas.

Antarctic seas are at higher latitudes, not lower. Lower latitudes are closer to the equator.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1918 on: November 15, 2019, 06:00:17 PM »
Hansen et al 2016:
https://pubs.giss.nasa.gov/abs/ha04710s.html

"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."

Thanks, Lennart.
I'm just trying to understand how far the quoted developments from Hansen 2016 have gone, as they seem to be a driving mechanism for Antarctic bottom melt.

Above we have seen that SO surface is indeed cooling.
Are lower latitudes warming? No, see attached, we have a negative SST trend in Antarctic seas.
Are we getting increased precipitation in SO? No, see attached, there is no trend there.

I don't see much evidence in satellite data for their claim.

If you are truly interested in the influence of ice meltwater (which also cools SST) and precipitation on Southern Ocean SSS (sea surface salinity), then I provided the following reference cited in Reply #1823, and I attach a pdf of that paper for your convenience:


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, doi: 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.
« Last Edit: November 15, 2019, 06:35:52 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1919 on: November 15, 2019, 06:16:47 PM »
The linked reference cites the 'Dominant Role of Extreme Precipitation Events in Antarctic Snowfall Variability', and notes that this dominance is most pronounced in the coastal and ice shelf areas; which by extension means that extreme precipitation events are also dominant over the coastal areas of the Southern Ocean.  So once again it is not wise to be blinded by averages when evaluating the influence of precipitation into the Southern Ocean and the subsequent impact on ice-climate feedback mechanisms (ala Hansen et al. [2016]) unless one evaluates precipitation during strong storms and atmospheric river events:

John Turner et al. (19 February 2019), "The Dominant Role of Extreme Precipitation Events in Antarctic Snowfall Variability", Geophysical Research Letters, https://doi.org/10.1029/2018GL081517

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL081517

Abstract
Antarctic snowfall consists of frequent clear‐sky precipitation and heavier falls from intrusions of maritime airmasses associated with amplified planetary waves. We investigate the importance of different precipitation events using the output of the RACMO2 model. Extreme precipitation events consisting of the largest 10% of daily totals are shown to contribute more than 40% of the total annual precipitation across much of the continent, with some areas receiving in excess of 60% of the total from these events. The greatest contribution of extreme precipitation events to the annual total is in the coastal areas and especially on the ice shelves, with the Amery Ice Shelf receiving 50% of its annual precipitation in less than the 10 days of heaviest precipitation. For the continent as a whole, 70% of the variance of the annual precipitation is explained by variability in precipitation from extreme precipitation events, with this figure rising to over 90% in some areas.

Plain Language Summary
The Antarctic ice sheet is extremely important because of its possible contribution to sea level rise and through the climate records than can be reconstructed using chemical signals locked in the ice. The mass of the ice sheet is constantly changing because of the ice gained by snowfall and the loss of ice at the margins via iceberg calving and melt through contact with relatively warm water masses. The amount of snow falling on the Antarctic is highly variable and dependent on the meteorological conditions over the Southern Ocean and the penetration of marine air into the interior. We show that extreme snowfall events, defined at the heaviest 10% of daily precipitation amounts, contribute a high percentage of the annual snowfall and are the main factor controlling the year‐to‐year variability of snowfall across the continent. This has implications for the reconstruction of past climate records using data from ice cores and the selection of future ice core drilling sites.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1920 on: November 15, 2019, 06:37:23 PM »
...
These subglacial lakes typically take about twenty years to refill, so circa 2032 to 2035 they should be ready to push any icebergs out of the Thwaites gateway (thus exposing any ice cliff there at that time) if another subglacial cavity were to collapse near the base of the Thwaites Ice Tongue (say the Big Ear subglacial cavity), which could lead to a subsequent MICI-type of failure of the BSB.

Not only might the upstream subglacial lakes drain circa 2035 (or earlier), but currently extreme El Nino events occur about every 20-years, with the last such occurrence being the 2015-16 event; which on average would put such another extreme event around 2035-36.  However, the linked article (and associated research) indicates that such extreme events will occur about every 10-years when GMSTA reaches about 1.5C, while Gavin Schmidt projects that GMSTA will be about 1.23C in 2019; which raises the probability that we will experience another extreme El Nino event sometime between 2030 and 2035.  Furthermore, the 2015-16 event resulted in significant amounts of surface ice melting on many West Antarctic ice shelves.  Thus, it is possible that hydrofracturing could contribute to a collapse of the Thwaites Glacier residual Ice Tongue and Eastern Ice Shelf between 2031 and 2036 during an extreme El Nino event.

Title: "‘Extreme’ El Niños to double in frequency under 1.5C of warming, study says"

https://www.carbonbrief.org/extreme-el-ninos-double-frequency-under-one-point-five-celsius-warming-study

Extract: "If global warming reaches 1.5C above pre-industrial levels – the aspirational limit of the Paris Agreement – extreme El Niño events could happen twice as often, the researchers find.

That means seeing an extreme El Niño on average every 10 years, rather every 20 years."

Also, I provide a link to Kim et al (2018)] that cites a subglacial cavity collapse near the Little Ear in January 2012 that resulted in the formation of an abrupt drop in the local surface elevation in the trough shown in the first and second images by Kim et al. (2018).  As noted before, the September 2012 event also triggered a surge in the ice flow of the Thwaites Ice Tongue.

Seung Hee Kim, Duk-jin Kim and Hyun-Cheol Kim (2018), "Progressive Degradation of an Ice Rumple in the Thwaites Ice Shelf, Antarctica, as Observed from High-Resolution Digital Elevation Models", Remote Sens, 9, 1236; doi:10.3390/rs1008123

Abstract: "Ice rumples are locally-grounded features of flowing ice shelves, elevated tens of meters above the surrounding surface. These features may significantly impact the dynamics of ice-shelf grounding lines, which are strongly related to shelf stability. In this study, we used TanDEM-X data to construct high-resolution DEMs of the Thwaites ice shelf in West Antarctica from 2011 to 2013. We also generated surface deformation maps which allowed us to detect and monitor the elevation changes of an ice rumple that appeared sometime between the observations of a grounding line of the Thwaites glacier using Double-Differential Interferometric SAR (DDInSAR) in 1996 and 2011. The observed degradation of the ice rumple during 2011–2013 may be related to a loss of contact with the underlying bathymetry caused by the thinning of the ice shelf. We subsequently used a viscoelastic deformation model with a finite spherical pressure source to reproduce the surface expression of the ice rumple. Global optimization allowed us to fit the model to the observed deformation map, producing reasonable estimates of the ice thickness at the center of the pressure source. Our conclusion is that combining the use of multiple high-resolution DEMs and the simple viscoelastic deformation model is feasible for observing and understanding the transient nature of small ice rumples, with implications for monitoring ice shelf stability."

Extract: "…  we monitored the surface features of the ice rumple using Landsat 7 ETM+ images from 2003–2014 (Figure 7). The images in this time series showed a gradual dissipation of the ice rumple, strongly indicating continuous thinning of the Thwaites ice shelf. Furthermore, the disappearance of surface features (e.g., crevasses and surface gradient) from 2013 onwards suggests that the ice shelf has been ungrounded, removing the pressure point that had been maintaining the ice rumple. Nonetheless, the ice shelf might have been in contact with the pinning point even after the disappearance of surface features, as intermittent ice contact to the pinning point could be possible due to ice shelf thickness fluctuations [29].

According to the optimization result, the ice thickness was 711.64 ± 14.25 m and 683.76 ± 12.48 m in 2011 and 2012, respectively. This is quite different from the known ice thickness of the Thwaites ice shelf near the grounding line (~1 km), despite the low vertical resolution of the radar sounder used for such measurements [7]. This indicates a thickness decrease of 36.17 ± 17.27 m during that one-year period. However, as the center of the pressure source in 2012 was located 341.96 m upstream and 210.10 m to the west from that in 2011, it is difficult to substantiate the thickness and thickness change with the obtained datasets. Our results for the surface depression and thinning of the ice rumple in the Thwaites ice shelf were much higher than that previously reported. It is rather surprising to observe such high (>10 m) surface depressions in an ice shelf in such a short time; Rignot et al. [30] and Paolo et al. [14] reported that the thinning rate of the Thwaites ice shelf was 6.13 and 2.80 m/year, respectively. …
From 2011–2013, our deformation maps showed the recent fading of a small ice rumple in the surface of the Thwaites ice shelf, West Antarctica. The pinning point was located nearly 5 km offshore from the previously estimated grounding line in 2011, and appeared sometime between 1996 and 2011 when the grounding line of Thwaites Glacier retreated. The deformation pattern we found, along with a time series of Landsat 7 ETM+ imagery, showed that the ice was still in contact with the basal topography as late as 2013 but is likely to have since been unpinned. We then used the deformation maps with the simple viscoelastic deformation model (widely used in volcanic studies) to interpret the surface changes in terms of pressure changes at the bottom of the ice shelf by applying an idealized spherical pressure source. The estimated numbers were reasonable and the ice shelf thickness at the center of the spherical pressure source was also estimated using the depth and radius. The surface depression and thinning of this ice rumple were found to be much higher than those of previously reported levels for the broader region, …"

Caption for first image: "Figure 1. Grounding lines of Thwaites Glacier in 1996 (green) and 2011 (red) estimated using the DDInSAR method with European remote sensing (ERS) satellites [13,15]. The orange dotted rectangle in the eastern shelf indicates a larger ice rumple previously discussed by Tinto and Bell [7]. A newly generated digital elevation model derived from TanDEM-X data on 10 June 2011 is shown within the yellow rectangle. The small red feature inside the yellow dotted square indicates the smaller ice rumple considered in this study. The background image is the MODIS Mosaic of Antarctica (MOA) image map [16]. The overlaid ice velocity map was extracted from Rignot et al. [17].

Caption for the second image: "Figure 7. Landsat 7 ETM+ images from 2003–2014 showing the gradual disappearance of the studied ice rumple in the Thwaites ice shelf. Crevasses and surface gradients are generally created atop an ice rumple due to surface extension and elevation increase. Such features were visible as late as 2011 but disappeared by 2013, indicating gradual ice thinning. Larger images are magnifications of selected areas indicated by red boxes. The yellow dotted line was extracted from the grounding line of the MEaSUREs dataset [13,15]."

Regarding the possible implications of both event driven events cited previously in this post, this might flush-out any floating icebergs within the trough leading to the BSB; which might well move the location of the local grounding line towards the upstream in of the trough where ice cliff failure mechanisms might possibly occur before 2040.
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Tom_Mazanec

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1921 on: November 15, 2019, 07:30:17 PM »
Quote
Not only might the upstream subglacial lakes drain circa 2035 (or earlier), but currently extreme El Nino events occur about every 20-years, with the last such occurrence being the 2015-16 event; which on average would put such another extreme event around 2035-36.
Even if that remains true, isn't it an average? Like saying the Pacific Northwest has a megaquake every 500 years and the last one was in January 1700, so we are safe for 180 years? Or a city wiping mereor hits twice a millennium and the last was in 1908, so we have nothing to worry about? Couldn't a big El Nino happen almost any year in the Twenties?
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1922 on: November 15, 2019, 08:35:23 PM »
Quote
Not only might the upstream subglacial lakes drain circa 2035 (or earlier), but currently extreme El Nino events occur about every 20-years, with the last such occurrence being the 2015-16 event; which on average would put such another extreme event around 2035-36.
Even if that remains true, isn't it an average? Like saying the Pacific Northwest has a megaquake every 500 years and the last one was in January 1700, so we are safe for 180 years? Or a city wiping mereor hits twice a millennium and the last was in 1908, so we have nothing to worry about? Couldn't a big El Nino happen almost any year in the Twenties?

Tom,

You are asking a fundamentally important question that I only have time to give a partial response to:

Many consensus scientists like to assume that the pool of observed events that they draw their statistics from comes from a system that is in at least pseudo-static equilibrium, as would reasonably be the case for calculating the risk of a meteor strike; however, this is not the case for case for systems that are not in pseudo-static equilibrium, such as for Earth Systems near a tipping point subjected to forcing or for a system that accumulates risk with time such as for earthquakes where tectonic strains/deformations accumulate with time along a fault system.

Thus, as warm water accumulates with time in the Western Pacific Warm Pool, with each passing year an extreme El Nino event becomes more likely, and also as the frequency of extreme El Nino events increases with GMSTA; both of these considerations.

Furthermore, in complex systems subject to cascades of tipping point can be subject to abrupt changes in return periods for any give event in the cascade chain.  For instance, as you note the current 20-year return period is only an average for a system in pseudo-static equilibrium, while a right-tailed extreme El Nino event could occur much earlier (particularly given the current volume of warm water in the Western Pacific Warm Pool, and the current rate of global warming); which might then thin the ice within a subglacial cavity near the base of the Thwaites Ice Tongue; which might then trigger an earlier collapse of that subglacial cavity; which might then accelerate the return period for a surge of glacial ice feeding the Thwaites Ice Tongue; which might then unseal the subglacial drainage system that empties through the Thwaites gateway; that might then accelerate the flushing of any icebergs between the Thwaites gateway and the open sea; which might then trigger an earlier than projected (say by DeConto and Pollard) slumping type of MICI-failure mechanism on the upstream side of the Thwaites gateway; that could then trigger an earlier than projected collapse of the glacial ice in the Byrd Subglacial Basin; that then might trigger an earlier than project collapse of the WAIS and the Totten Glacier.

Edit: The linked reference and associated images provides an example of how to calculate reliability, return period and risk for systems subjected to nonstationarity:

Laura K. Read and Richard M. Vogel (21 July 2015), "Reliability, return periods, and risk under nonstationarity", Water Resources Research, https://doi.org/10.1002/2015WR017089

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2015WR017089
&
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015WR017089

Abstract
Water resources design has widely used the average return period as a concept to inform management and communication of the risk of experiencing an exceedance event within a planning horizon. Even though nonstationarity is often apparent, in practice hydrologic design often mistakenly assumes that the probability of exceedance, p, is constant from year to year which leads to an average return period To equal to 1/p; this expression is far more complex under nonstationarity. Even for stationary processes, the common application of an average return period is problematic: it does not account for planning horizon, is an average value that may not be representative of the time to the next flood, and is generally not applied in other areas of water planning. We combine existing theoretical and empirical results from the literature to provide the first general, comprehensive description of the probabilistic behavior of the return period and reliability under nonstationarity. We show that under nonstationarity, the underlying distribution of the return period exhibits a more complex shape than the exponential distribution under stationary conditions. Using a nonstationary lognormal model, we document the increased complexity and challenges associated with planning for future flood events over a planning horizon. We compare application of the average return period with the more common concept of reliability and recommend replacing the average return period with reliability as a more practical way to communicate event likelihood in both stationary and nonstationary contexts.
« Last Edit: November 15, 2019, 08:57:12 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1923 on: November 15, 2019, 09:41:42 PM »
One would expect that NOAA knows something about ocean-atmosphere interactions, thus I single-out their GFDL CM4.0's projection of a most likely current value of ECS of about 5.0C (see the first attached image & linked references).  NOAA's most significant changes for GFDL CM4.0 as compared to earlier model projections (with lower values of ECS) was improvements to the ocean, ice and aerosol modules; that lead to increasingly net positive cloud feedbacks (and much higher model skill levels as indicated by the second attached image).  This result is what only would expect from MISI-types of ice-climate feedback contributions to ECS; which leaves one to speculate what effective values of climate sensitivity would be projected if/when CMIP7/CMIP8 projections evaluate the impacts of MICI-types of ice-climate feedback mechanisms:

I.M. Held, H. Guo, A. Adcroft, J. P. Dunne, L.W. Horowitz, J. Krasting, E. Shevliakova, M. Winton, M. Shao, M. Bushuk, A.T. Wittenberg, B. Wyman, B. Xiang, R. Zhang, W. Anderson, V. Balaji, L. Donner, K. Dunne, J. Durachta, P. Gauthier, P. Ginoux, J-C. Golaz, S.M. Griffies, R. Hallberg, L. Harris, M. Harrison, W. Hurlin, J. John, P. Lin, S.J. Lin, S. Malyshev, R. Menzel, P.C.D. Milly, Y. Ming, V. Naik, D. Paynter, F. Paulot, V. Ramaswamy, B. Reichl, T. Robinson, A. Rosati, C. Seman, L. Silvers, S. Underwood, N. Zadeh (2019), "Structure and Performance of GFDL's CM4.0 Climate Model", Journal of Advances in Modeling Earth Systems (JAMES). DOI: 10.1029/2019MS001829

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019MS001829

Abstract
We describe GFDL's CM4.0 physical climate model, with emphasis on those aspects that may be of particular importance to users of this model and its simulations. The model is built with the AM4.0/LM4.0 atmosphere/land model and OM4.0 ocean model. Topics include the rationale for key choices made in the model formulation, the stability as well as drift of the pre‐industrial control simulation, and comparison of key aspects of the historical simulations with observations from recent decades. Notable achievements include the relatively small biases in seasonal spatial patterns of top‐of‐atmosphere fluxes, surface temperature, and precipitation; reduced double Intertropical Convergence Zone bias; dramatically improved representation of ocean boundary currents; a high quality simulation of climatological Arctic sea ice extent and its recent decline; and excellent simulation of the El Niño‐Southern Oscillation spectrum and structure. Areas of concern include inadequate deep convection in the Nordic Seas; an inaccurate Antarctic sea ice simulation; precipitation and wind composites still affected by the equatorial cold tongue bias; muted variability in the Atlantic Meridional Overturning Circulation; strong 100 year quasi‐periodicity in Southern Ocean ventilation; and a lack of historical warming before 1990 and too rapid warming thereafter due to high climate sensitivity and strong aerosol forcing, in contrast to the observational record. Overall, CM4.0 scores very well in its fidelity against observations compared to the Coupled Model Intercomparison Project Phase 5 generation in terms of both mean state and modes of variability and should prove a valuable new addition for analysis across a broad array of applications.

Plain Language Summary
The Geophysical Fluid Dynamics Laboratory (GFDL) of the National Oceanic and Atmospheric Administration (NOAA) participates along with a number of model centers around the world in constructing state‐of‐the‐art climate models for use in studies for climate change and prediction. GFDL's latest multi‐purpose atmosphere‐ocean coupled climate model, CM4.0, is described here. It consists of GFDL's latest atmosphere and land models at about 100 km horizontal resolution, and ocean and sea ice models at roughly 25 km horizontal resolution. A handful of standard experiments have been conducted with CM4.0 for participation in the Coupled Model Intercomparison Project Phase 6, an archive of climate model results utilized by the Intergovernmental Panel on Climate Change and the climate research community more generally. The model results have been extensively evaluated against observations. This paper makes the case that CM4.0 ranks high among state‐of‐the‐art coupled climate models by many measures of bias in the simulated climatology and in its ability to capture modes of climate variability such as the El Niño‐Southern Oscillation and Madden‐Julian Oscillation. The paper also discusses some potential weaknesses, including unrealistically large internal variability in the Southern Ocean and insufficient warming before 1990 in the simulation of the 20th century.

See also:

Title: "Structure and Performance of GFDL’s CM4.0 Climate Model"

https://www.gfdl.noaa.gov/research_highlight/structure-and-performance-of-gfdls-cm4-0-climate-model/

Extract: "This paper describes the GFDL’s latest multi-purpose atmosphere-ocean coupled climate model, CM4.0. It consists of GFDL’s newest atmosphere and land models at about 100 km horizontal resolution, and ocean and sea ice models at roughly 25 km horizontal resolution. A handful of standard experiments have been conducted with CM4.0 for participation in the Coupled Model Inter-comparison Project Phase 6 (CMIP6), an archive of climate model results utilized by the Intergovernmental Panel on Climate Change (IPCC) and the climate research community more generally.

The model results have been extensively evaluated against observations. This paper makes the case that CM4.0 ranks high among state-of-the-art coupled climate models by many measures of bias in the simulated climatology and in its ability to capture modes of climate variability, such as the El Niño-Southern Oscillation and Madden-Julian Oscillation. The paper also discusses some potential weaknesses, including unrealistically large internal variability in the Southern Ocean and insufficient warming before 1990 in the simulation of the 20th century.

The two figures below illustrate the quality of CM4.0’s simulation of the current climate. The first figure compares the spatial pattern of the top-of-atmosphere (TOA) radiative fluxes with that of the CMIP5 coupled climate models used in the last IPCC assessment. CM4.0 has lower root-mean-square errors in (red dots) than nearly all CMIP5 models (box and whiskers). The second figure shows the realism of the pattern of sea surface temperature anomalies in a typical ENSO event in CM4.0, a marked improvement over other GFDL models used in IPCC assessments (not shown)."

&

JAMES' reference series on: "Geophysical Fluid Dynamics Laboratory CMIP6 Models"

https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)1942-2466.CMIPMOD1


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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1924 on: November 15, 2019, 10:08:40 PM »
I have previously noted that one ice-climate feedback associated with ice mass loss from the WAIS is that it pushes relatively warm North Pacific Ocean water thru the Bering Strait into the Chukchi Sea (see the first attached image) where it would suppress (is suppressing) local ice formation as indicated by the second attached image showing the regional sea ice extents on November 15, 2019 for the Bering and Chukchi Seas (and the Sea of Okhotsk); which suggests that the sea ice in these areas does not appear to understand that it is nearly winter.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1925 on: November 15, 2019, 10:59:11 PM »
For this post I decided to combine several different positive feedback mechanisms associated with both the ocean and ice systems:

1. The first image confirms that the AMOC has been slowing for decades due to some unknown combination of decadal cyclic oscillations, climate change and ice-climate feedback.  So, whether this is a coincidence or not it will accelerate the warming of the SST of the tropical oceans in the coming decades.

2. The second image shows that for whatever reason (the Antarctic ozone hole, climate change or ice-climate feedback) Agulhas leakage from the Indian Ocean into the Atlantic Ocean, which will eventually reach the Gulf Stream where it will likely penetrate more warm water into the Arctic Ocean in the coming decades.

3. The third image shows how warm surface water leaks out of the Western Pacific Warm Pool into the Southern Ocean, where it eventually contributes to Antarctic ice melting; while the fourth image shows how the ocean's surface currents span the world and interacts with the MOC; which indicates that as the MOC slows more leakage will occur from the Western Pacific Warm Pool into the Southern Ocean; which constitutes yet another positive feedback factor for more climate change.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1926 on: November 15, 2019, 11:27:10 PM »
[Are lower latitudes warming? No, see attached, we have a negative SST trend in Antarctic seas.

Antarctic seas are at higher latitudes, not lower. Lower latitudes are closer to the equator.

Yes, my bad... when down under, up is down :)

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1927 on: November 16, 2019, 04:33:04 PM »
The National Academies of Sciences, Engineering and Medicine represents the gold standard in the USA for evaluating climate change risks, thus I do not believe that it would be wise for the IPCC bodies working to develop new forcing scenarios to replace the SSP scenarios [see the first attached image from Riahi et al. (2017)] to ignore Steffen et al (2018)'s warnings of the risks of following trajectories leading to a 'hot house' Earth, nor to ignore Scambos et al. (2017); which indicates that: 'Constraining how much and how fast the West Antarctic Ice Sheet (WAIS) will change in the coming decades has recently been identified as the highest priority in Antarctic research (National Academies, 2015)'.

Therefore, in addition to the traditional five families of anthropogenic radiative forcing scenarios that the IPCC normally sponsors for each new Assessment Report; I recommend that for AR7 the IPCC creates a sixth family of forcing scenarios that considers the non-radiative forcing from MICI-type collapses of key marine (and marine terminating) glaciers in both Antarctica and Greenland combined with a postulated major global socio-economic contraction beginning circa 2050, where it would be assumed that the world would abruptly transition from its current BAU (or SSP 5) pathway to an essentially carbon neutral pathway due to the postulated contraction circa 2050.  Fundamentally, I am recommending that the IPCC follow the approach used by Hansen et al. (2016), but to develop a family of more rigorous scenarios based on ice sheet forcing risks starting with the CMIP6 projections that consider MISI-type ice-climate feedbacks (which likely contributed to many of these models projection values of ECS equal to, or greater than, 5C).

Due to the complexities of MICI-type of mechanism, I would further recommend that the IPCC use the output from the eight different projects of the 5-year (starting in 2018) International Thwaites Glacier Collaboration (see the second image) in 2023-2024 to create regional models of both Antarctica and Greenland in order to develop values for the non-radiative forcing from MICI-types of collapses from key marine (& marine terminating) glaciers; to create this sixth IPCC sponsored family of non-radiative forcing scenarios (starting circa 2040 to 2050) that would be input into CMIP7 models to provide input into AR7.

Examples of variables that scientists (possibly advised by such experts as: Rignot, Hansen, Alley, Pollard and DeConto) could use to develop different individual scenarios for such a sixth family of both radiative and non-radiative forcing scenarios could/might include:

1. Key governments (such as the USA) implementing aerosol-based geoengineering between 2040 and 2050; that cannot be sustained after 2050 due to the postulated global socio-economic contraction.

2. Key marine terminating glaciers (such as Jakobshavn) providing a multi-year armada of icebergs into the North Atlantic (say between 2030 & 2035) that might trigger a collapse of key Antarctic Peninsula ice shelves (say Larsen C) due to the bipolar seesaw mechanism; that might trigger an increase in upwelling of warm CDW across key Antarctic continental shelves that might increase the risks of local MICI-type failures of local marine glaciers (like Thwaites).

3. An extreme El Nino event circa 2030 could drive a seasons worth of warm CDW into the ASE in 2031 that could hollow-out the Big Ear subglacial cavity in the Thwaites gateway by 2033 that could lead to a collapse of that subglacial cavity leading to a surge of the glacial ice feeding the Thwaites Ice Tongue causing it to collapse and to an outburst of the subglacial meltwater from the Thwaites subglacial drainage system (including the previously mentioned four subglacial lakes) that could push out to sea any mélange of icebergs seaward of the ice cliff in the Thwaites gateway.

I could cite other variables cited in this thread but hopefully if the IPCC were wise enough to appoint scientists like Rignot, Hansen, Alley, Pollard and/or DeConto to the team developing such non-radiative forcing contributions to the sixth suite of forcing scenarios, they would have no trouble developing appropriate combinations of variables for different scenarios (hopefully with input from the researchers from at least the International Thwaites Glacier Collaboration):

Will Steffen, Johan Rockström, Katherine Richardson, Timothy M. Lenton, Carl Folke, Diana Liverman, Colin P. Summerhayes, Anthony D. Barnosky, Sarah E. Cornell, Michel Crucifix, Jonathan F. Donges, Ingo Fetzer, Steven J. Lade, Marten Scheffer, Ricarda Winkelmann, and Hans Joachim Schellnhuber (August 14, 2018),"Trajectories of the Earth System in the Anthropocene", PNAS, 115 (33), 8252-8259, https://doi.org/10.1073/pnas.1810141115

https://www.pnas.org/content/115/33/8252

Abstract: "We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be. If the threshold is crossed, the resulting trajectory would likely cause serious disruptions to ecosystems, society, and economies. Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System—biosphere, climate, and societies—and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values."

&

T.A. Scambos et al. (2017), "How much, how fast?: A science review and outlook for research on the instability of Antarctica's Thwaites Glacier in the 21st century", Global and Planetary Change, Volume 153, June 2017, Pages 16-34

https://www.sciencedirect.com/science/article/pii/S092181811630491X

Abstract: "Constraining how much and how fast the West Antarctic Ice Sheet (WAIS) will change in the coming decades has recently been identified as the highest priority in Antarctic research (National Academies, 2015). Here we review recent research on WAIS and outline further scientific objectives for the area now identified as the most likely to undergo near-term significant change: Thwaites Glacier and the adjacent Amundsen Sea. Multiple lines of evidence point to an ongoing rapid loss of ice in this region in response to changing atmospheric and oceanic conditions. Models of the ice sheet's dynamic behavior indicate a potential for greatly accelerated ice loss as ocean-driven melting at the Thwaites Glacier grounding zone and nearby areas leads to thinning, faster flow, and retreat. A complete retreat of the Thwaites Glacier basin would raise global sea level by more than three meters by entraining ice from adjacent catchments. This scenario could occur over the next few centuries, and faster ice loss could occur through processes omitted from most ice flow models such as hydrofracture and ice cliff failure, which have been observed in recent rapid ice retreats elsewhere. Increased basal melt at the grounding zone and increased potential for hydrofracture due to enhanced surface melt could initiate a more rapid collapse of Thwaites Glacier within the next few decades."

&

Keywan Riahi et al. (January 2017), "The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview", Global Environmental Change, Volume 42, Pages 153-168, https://doi.org/10.1016/j.gloenvcha.2016.05.009

https://www.sciencedirect.com/science/article/pii/S0959378016300681

Extract: "While the SSPs were designed to represent different mitigation and adaptation challenges, the resulting narratives and quantifications span a wide range of different futures broadly representative of the current literature. This allows their subsequent use and development in new assessments and research projects. Critical next steps for the community scenario process will, among others, involve regional and sectoral extensions, further elaboration of the adaptation and impacts dimension, as well as employing the SSP scenarios with the new generation of earth system models as part of the 6th climate model intercomparison project (CMIP6)."

&

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."


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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1928 on: November 16, 2019, 05:25:05 PM »
Here I post a few more positive feedback mechanisms that interact with ice-climate feedback mechanisms:

1. The first two images show that the surface of the ocean is warming much more rapidly than the deeper zones of the ocean; which leads to an increasingly stratified ocean; which would promote the relatively rapid warming of future tropical ocean SSTs if MICI-types of mechanism were to occur in the coming decades.

2. The third image shows how as the deeper zones of the Southern Ocean warm with continued global warming, these zones are projected to release more CO2 into the atmosphere; and I have previously noted that possible MICI-type mechanism that could develop in coming decades my slow the MOC sufficiently to leak more warm water (that would otherwise be the case) into the Southern Ocean (particularly from the Pacific Ocean).

3. The fourth image shows how warming ocean bottom waters particularly in shallow portions of the Pacific Ocean (such as the warm water periodically killing coral reefs), can induce/accelerate the venting of hydrothermal CO2 from the seafloor into the atmosphere.  Presumably a major MICI-type of freshwater hosing events considered by Hansen et al. (2016) would increase the planetary energy imbalance sufficiently to accelerate such hydrothermal venting for at least multiple decades.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1929 on: November 16, 2019, 05:27:22 PM »
Quote
I could cite other variables cited in this thread but hopefully if the IPCC were wise enough to appoint scientists like Rignot, Hansen, Alley, Pollard and/or DeConto to the team developing such non-radiative forcing contributions to the sixth suite of forcing scenarios, they would have no trouble developing appropriate combinations of variables for different scenarios (hopefully with input from the researchers from at least the International Thwaites Glacier Collaboration):
The triumph of hope over experience.
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1930 on: November 16, 2019, 05:43:36 PM »
Quote
I could cite other variables cited in this thread but hopefully if the IPCC were wise enough to appoint scientists like Rignot, Hansen, Alley, Pollard and/or DeConto to the team developing such non-radiative forcing contributions to the sixth suite of forcing scenarios, they would have no trouble developing appropriate combinations of variables for different scenarios (hopefully with input from the researchers from at least the International Thwaites Glacier Collaboration):
The triumph of hope over experience.

If hoping that the IPCC would behave rationally is too much of a stretch, then if the GOP gets hit by a blue-wave in the 2020 election, then it would be imaginable that with the International Thwaites Glacier Collaboration, ending in 2023, that by 2024 the end of campaign 2 & Version 4 of the start-of-the-art E3SM program together with an Exascale computer (see the two attached images) might include MICI-mechanisms (validated by the International Thwaites Glacier Collaboration findings) which could then provide more realistic projections for CMIP7 and AR7 using the next suite of conventional IPCC anthropogenic radiative forcing scenarios.

Edit: If believing that E3SM might incorporate re-calibrated MICI-mechanisms after major simulation campaign 2 is too much of a stretch for some to believe then the last chance for society to get a heads-up in time to try to safeguard some vestige of mankind from the worst impacts of the likely major global socio-economic contract that I have postulated circa 2050, might be after 2028 when the results of major simulation campaign 4 are released.
« Last Edit: November 16, 2019, 09:38:47 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1931 on: November 16, 2019, 09:45:34 PM »
While many/most people in the world are not likely to become vegetarian/vegan anytime soon; that is no reason for more reasonable people not to, as doing so offers both health and environmental benefits as cited by the linked reference:

Michael A Clark, Marco Springmann, Jason Hill, and David Tilman (November 12, 2019), "Multiple health and environmental impacts of foods", PNAS, 116 (46) 23357-23362,  https://doi.org/10.1073/pnas.1906908116

https://www.pnas.org/content/116/46/23357

Significance
Dietary choices are a leading global cause of mortality and environmental degradation and threaten the attainability of the UN’s Sustainable Development Goals and the Paris Climate Agreement. To inform decision making and to better identify the multifaceted health and environmental impacts of dietary choices, we describe how consuming 15 different food groups is associated with 5 health outcomes and 5 aspects of environmental degradation. We find that foods associated with improved adult health also often have low environmental impacts, indicating that the same dietary transitions that would lower incidences of noncommunicable diseases would also help meet environmental sustainability targets.

Abstract
Food choices are shifting globally in ways that are negatively affecting both human health and the environment. Here we consider how consuming an additional serving per day of each of 15 foods is associated with 5 health outcomes in adults and 5 aspects of agriculturally driven environmental degradation. We find that while there is substantial variation in the health outcomes of different foods, foods associated with a larger reduction in disease risk for one health outcome are often associated with larger reductions in disease risk for other health outcomes. Likewise, foods with lower impacts on one metric of environmental harm tend to have lower impacts on others. Additionally, of the foods associated with improved health (whole grain cereals, fruits, vegetables, legumes, nuts, olive oil, and fish), all except fish have among the lowest environmental impacts, and fish has markedly lower impacts than red meats and processed meats. Foods associated with the largest negative environmental impacts—unprocessed and processed red meat—are consistently associated with the largest increases in disease risk. Thus, dietary transitions toward greater consumption of healthier foods would generally improve environmental sustainability, although processed foods high in sugars harm health but can have relatively low environmental impacts. These findings could help consumers, policy makers, and food companies to better understand the multiple health and environmental implications of food choices.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1932 on: November 17, 2019, 01:32:11 AM »
The linked open access reference indicates that the unusual amount of wildfires in the Amazon this year is strongly correlated to prior deforestation:

Jos Barlow  Erika Berenguer  Rachel Carmenta  Filipe França (15 November 2019),  "Clarifying Amazonia's burning crisis", Global Change Biology, https://doi.org/10.1111/gcb.14872

https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14872

Abstract
This article clarifies the different types of fire in the Amazon, their different drivers and the positive feedbacks that can lead to more fires in the region. It then explores evidence regarding the peak in active fire detections in August 2019, showing that these were linked to the highest levels of deforestation since 2008. Finally, we examine the solutions needed to reduce the prevalence of uncontrolled or illegal fire in the Brazilian Amazon.




Recent fires in the Amazon have attracted much political and media attention, but it still remains unclear what has been burning. This is crucial to understanding impacts and identifying solutions. There are three broad types of fire in the Amazon (Figure 1a). First, there are deforestation fires—the process of clearing primary forest which starts with the vegetation being felled and left to dry. Fire is then used to prepare the area for agriculture. Second, there are fires in areas that have been previously cleared. For example, cattle ranchers use fire to rid pastures of weeds, and smallholders, indigenous and traditional peoples use fire in farm‐fallow systems. Not all fires in previously cleared lands are intentional—some escape beyond intended limits. Third, fires can invade standing forests, either for the first time when flames are mostly restricted to the understorey, or as repeated events, resulting in more intense fires.

Figure 1
Open in figure viewerPowerPoint
(a) An overview of fire types, drivers and their positive feedbacks on fire prevalence. Fire types are shaded by the three broad classes of fire in the Amazon: Deforestation (dark grey), fires on previously cleared lands (grey), and forest fires (light grey). Deforestation and agricultural fires are intentional, while uncontrolled fires are either started accidentally or through malevolent intent. (b) Annual deforestation (August–July, following PRODES from TerraBrasilis & INPE 2019; yellow) and active fire counts (January–August, matching the pre‐Moratoria period in 2019; grey bars, stacked to separate January‐July and August). Deforestation in 2019 (orange) was estimated based on DETER‐b (TerraBrasilis & INPE 2019). Active fire counts are from BDQueimadas. Years with extreme droughts are shown with an asterisk. (c) Monthly deforestation detected by DETER‐b for the period April–September, comparing 2019 (red) with the mean ± SD from 2016–2018 (blue). The vertical dashed line represents the onset of the fire moratoria
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1933 on: November 17, 2019, 03:33:16 AM »
As I have previously discussed, the increasing frequency of atmospheric river events poses a threat to WAIS stability with continued global warming (see the linked reference):

Jonathan D. Wille et al. (2019), "West Antarctic surface melt triggered by atmospheric rivers", Nature Geoscience,  12, 911–916, doi:10.1038/s41561-019-0460-1

https://www.nature.com/articles/s41561-019-0460-1

Abstract: "Recent major melting events in West Antarctica have raised concerns about a potential hydrofracturing and ice shelf instability. These events often share common forcings of surface melt-like anomalous radiative fluxes, turbulent heat fluxes and föhn winds. Using an atmospheric river detection algorithm developed for Antarctica together with surface melt datasets, we produced a climatology of atmospheric river-related surface melting around Antarctica and show that atmospheric rivers are associated with a large percentage of these surface melt events. Despite their rarity (around 12 events per year in West Antarctica), atmospheric rivers are associated with around 40% of the total summer meltwater generated across the Ross Ice Shelf to nearly 100% in the higher elevation Marie Byrd Land and 40–80% of the total winter meltwater generated on the Wilkins, Bach, George IV and Larsen B and C ice shelves. These events were all related to high-pressure blocking ridges that directed anomalous poleward moisture transport towards the continent. Major melt events in the West Antarctic Ice Sheet only occur about a couple times per decade, but a 1–2 °C warming and continued increase in atmospheric river activity could increase the melt frequency with consequences for ice shelf stability."
« Last Edit: November 17, 2019, 03:38:21 AM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1934 on: November 17, 2019, 04:15:55 AM »

...I recommend that for AR7 the IPCC creates a sixth family of forcing scenarios that considers the non-radiative forcing from MICI-type collapses of key marine (and marine terminating) glaciers in both Antarctica and Greenland combined with a postulated major global socio-economic contraction beginning circa 2050, where it would be assumed that the world would abruptly transition from its current BAU (or SSP 5) pathway to an essentially carbon neutral pathway due to the postulated contraction circa 2050. ...


What about capitalist market forces that in the coming decades will totally change the energy markets in favour of renewables? That e.g. solar energy is already beating coal to the dust?
That no new ICE cars will be produced in 20 years?
Because old technologies can't compete price-wise, they will soon be extinct.

Shouldn't we ask the IPCC to include also those very dynamic forcing factors of capitalism as we know it, in your proposed sixth family of forcing scenarios? The so called BAU is already greening all by itself. We will soon not be following RCP 8.5.

I do find your scenarios too rigid and too speculative. If you reject the fundamental influence of market forces you always risk repeating the mistake of the Club of Rome report "Limits to growth".

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1935 on: November 17, 2019, 07:49:44 AM »
... Version 4 of the start-of-the-art E3SM program together with an Exascale computer (see the two attached images) might include MICI-mechanisms (validated by the International Thwaites Glacier Collaboration findings) which could then provide more realistic projections for CMIP7 and AR7 using the next suite of conventional IPCC anthropogenic radiative forcing scenarios.

Edit: If believing that E3SM might incorporate re-calibrated MICI-mechanisms after major simulation campaign 2 is too much of a stretch for some to believe then the last chance for society to get a heads-up in time to try to safeguard some vestige of mankind from the worst impacts of the likely major global socio-economic contract that I have postulated circa 2050, might be after 2028 when the results of major simulation campaign 4 are released.


It's not astonishing that this particular GCM displays a high ECS, over 5.
"E3SMv1's high climate sensitivity is solely due to its large positive cloud feedback, which causes its net feedback parameter (which quantifies how strongly the 4xCO2 forcing is radiatively damped) to be less negative than all but two CMIP5 models"

My impression is that the model makers delibaretely set this model on a trajectory that is sure to yield a high ECS, starting in around 1990, but that is rather inconsistent with GSTs from around 1960, see the attached figure.

Maybe E3SM developers should start addressing their troubling fundamental issues with correctly modelling hydrological cycle/convection first, before adding highly speculative MICI mechanisms.

Like many GCMs, these models are running hot when compared to the actual climate. The CMIP6 generation seem to be running even hotter than previous generations.

Another CMIP6 model displaying similar characteristics is UKESM1, see attached figure.
They are both tuned to run cool for 30 years (E3SM) and for 40 years (UKESM) up until approximately 1990, respectively. After 1990 they are both set off on a very steep trajectory.

Maybe these models are tweaked and tuned in order to get a suitably alarmist construct?
ECS is calculated from a short period of only 150 years, and the ECS value will be heavily influenced by model behaviour during that period, although actual equilibrium would take 1000s of simulated years to achieve.

As described in the papers documenting the E3SM model that I discussed up thread, the forecasts made with the current model generations is some variant of "magician's (pseudo-)science".

And NO, it certainly won't help with your proposed "Exascale computer" until you got your basic physical processes right. As I said before, these models lack theory on the hydrological cycle, esp. deep convection. They also lack data, as the satellite grid size is too big to capture the hydrological cycle, esp. in the tropics.

It would be more appropriate to refrain from believing in forecasts from these two GCM models.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018MS001603

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019MS001739
« Last Edit: November 17, 2019, 12:43:46 PM by Hefaistos »

Lennart van der Linde

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1936 on: November 17, 2019, 09:52:25 AM »
If you reject the fundamental influence of market forces you always risk repeating the mistake of the Club of Rome report "Limits to growth".

Have you actually read "Limits to Growth"? If so, where exactly did you find the mistake?
As far as I know they didn't reject the fundamental influence of market forces at all, but maybe I missed it.
Even market forces cannot provide unlimited material growth on a finite planet.
Current market forces are already exceeding several planetary ecological boundaries.
The longer this overshoot lasts, the higher the risk of eventual collapse.
Only by governing market forces can we hope to still avoid this collapse, or at least make its impact less destructive.
This is how I understand the Club of Rome's warning of 1972 (updated several times since), which still seems very accurate to me.

Hefaistos

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1937 on: November 17, 2019, 12:34:46 PM »
If you reject the fundamental influence of market forces you always risk repeating the mistake of the Club of Rome report "Limits to growth".

Have you actually read "Limits to Growth"? If so, where exactly did you find the mistake?
As far as I know they didn't reject the fundamental influence of market forces at all, but maybe I missed it.
Even market forces cannot provide unlimited material growth on a finite planet.
Current market forces are already exceeding several planetary ecological boundaries.
The longer this overshoot lasts, the higher the risk of eventual collapse.
Only by governing market forces can we hope to still avoid this collapse, or at least make its impact less destructive.
This is how I understand the Club of Rome's warning of 1972 (updated several times since), which still seems very accurate to me.

Yes Lennart, I was kind of mezmerised by the Limits to Growth (LTG) book, and actually worked with their programming language to develop some partial models for market processes. Even met briefly with Dennis and Donella and Jay Forrester at MIT in Boston in 1983.
The basic concept of LTG is that there are limited resources, and that mankind is depleting those resources in such a way that it triggers more or less uncontrollable dynamic developments regarding environment etc.
This concept is faulty. Resources will get higher relative prices the scarcer they become. But they won't be physically depleted. That was the first big modelling mistake they made.
The second big mistake was to disregard all technical development. This is also connected with the changing relative prices: when an essential resource gets a higher price due to scarcity, it will trigger developments to either replace that resource with substitutes or find ways to improve the extraction or production of the resource. If we take the oil industry as an example, OPEC tried to impose scarcity several times, oil prices went through the roof, but eventually oil was substituted for other sources of energy, and oil extraction saw new technologies being developed, such as fracking.
The third modelling mistake was to not include counteractions by TPTB.
That said, I agree with what you say about ecological boundaries. Capitalism needs regulation.

Tom_Mazanec

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1938 on: November 17, 2019, 01:57:33 PM »
IIRC, the LTG report showed resources asymptotically tending toward zero, but not reaching it.
Also, there were "switches", you could set to a date simulated as a policy or technology change.
I played around with the model on my old Apple ][+ back in the day and got some interesting results.
The most memorable was when I put the resources at the highest value the machine took, so the depletion was lost in roundoff...essentially making it infinite. The model went into a cycle of ~100-120 years of rise and fall as other constraints like pollution rose and fell.
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Lennart van der Linde

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1939 on: November 17, 2019, 02:38:41 PM »
The basic concept of LTG is that there are limited resources, and that mankind is depleting those resources in such a way that it triggers more or less uncontrollable dynamic developments regarding environment etc.
This concept is faulty. Resources will get higher relative prices the scarcer they become. But they won't be physically depleted. That was the first big modelling mistake they made.
The second big mistake was to disregard all technical development. This is also connected with the changing relative prices: when an essential resource gets a higher price due to scarcity, it will trigger developments to either replace that resource with substitutes or find ways to improve the extraction or production of the resource [...]
The third modelling mistake was to not include counteractions by TPTB.
That said, I agree with what you say about ecological boundaries. Capitalism needs regulation.

Below a few quotes from Limits to Growth 1972 and the 30-year update Limits to Growth 2004 that seem to contradict your assertions. Paraphrased Meadows et al say:
- dynamics only become uncontrollable if we wait too long to consciously limit material growth
- even when higher prices for scarcer resources lead to technological innovation and substitution in the short run the total supply of resources remains limited in the longer run
- counteractions by TPTB have been modelled in the several scenario's, including a scenario that avoids collapse by consciously limiting further material growth

Meadows et al argue that the longer we postpone implementing policies to limit material growth, the higher the risk of eventual collapse, without being able to predict exactly when this collapse may occur. In (most of) their scenario's this collapse would occur somewhere during this century, mainly depending on the exact ecological and technological limits.

The current climate crisis seems the ultimate illustration of the general accuracy of their analysis, with climate scientists showing we need extremely rapid emission reductions to avoid passing potentially catastrophic climate tipping points, while energy experts argue that such rapid reductions hardly seem possible without (in the short run) shrinking the global economy, or at least the material consumption in the richer economies.

So the crucial question seems to be: how long do we want to keep gambling with the future of our children? Or alternatively: how certain can we be that we're not risking their future by holding on to business-as-usual policies aimed at continued material growth?

gerontocrat

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1940 on: November 17, 2019, 05:41:15 PM »
I doubt that the LTG model included the use of plentiful resources that were harmful to the extent of being a potential existential threat when society knows it.

- We have vast amounts of coal reserves.
- We have loads of oil & natural gas (even if some places such as the USA may be soon reaching a second physical peak oil/gas limit).
- CO2 emissions are rising - reducing them by 45% by 2030? huh...
-We can and do make ever more increasing quantities of herbicides and pesticides. Many are known to be harmful but are still used in many parts of the world. So many new compounds are produced every year and put into the system after relatively short-term studies that the long-term effects are unknown.
- We knock down forests and and expand the acreage devoted to pasture, to plantations, to arable crops.
- We know we need biodiversity and reduce it at an alarming rate. When its gone its gone. Technology can't fix that - Jurassic Park is an SF flic.

So it's more like a drunk continuing to drink even though it will eventually cause liver failure & death. Many drunks stagger on longer than the Doctors think is possible, but in the end they die.

It is a small planet with limited resources to maintain life. That resource is in decline.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1941 on: November 17, 2019, 08:38:17 PM »

...I recommend that for AR7 the IPCC creates a sixth family of forcing scenarios that considers the non-radiative forcing from MICI-type collapses of key marine (and marine terminating) glaciers in both Antarctica and Greenland combined with a postulated major global socio-economic contraction beginning circa 2050, where it would be assumed that the world would abruptly transition from its current BAU (or SSP 5) pathway to an essentially carbon neutral pathway due to the postulated contraction circa 2050. ...

What about capitalist market forces that in the coming decades will totally change the energy markets in favour of renewables? That e.g. solar energy is already beating coal to the dust?
That no new ICE cars will be produced in 20 years?
Because old technologies can't compete price-wise, they will soon be extinct.

Shouldn't we ask the IPCC to include also those very dynamic forcing factors of capitalism as we know it, in your proposed sixth family of forcing scenarios? The so called BAU is already greening all by itself. We will soon not be following RCP 8.5.

I do find your scenarios too rigid and too speculative. If you reject the fundamental influence of market forces you always risk repeating the mistake of the Club of Rome report "Limits to growth".

1.  In my opinion, SSP1 already accounts for all of the positive dynamic forcing factor of capitalism that you are referring to but ignores vast majority of the negative dynamic forcing factors of capitalism that has allowed the fossil fuel industries to keep our current socioeconomic system on a BAU pathway by such factors as: developing hydrofracturing technology, lobbying for and receiving government subsides to stimulate short-term growth & employment; and replacing a lot of coal consumption with natural gas consumption that has an equal or greater global warming potential.

2. SSP5 (comparable to RCP 8.5) assumes a much lower peak world population (which is currently about 7.75 billion) than does the latest UN projections (see the first two images, respectively).  Furthermore, the 40-year update of Limits to Growth provides projections very much inline with our current BAU situation, and which projects a coming major socioeconomic contraction very much inline with my proposed sixth family of IPCC forcing scenarios (see the last two images, respectively).
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1942 on: November 17, 2019, 08:56:55 PM »
For those who think that my estimate of a global socioeconomic collapse circa 2050 is too aggressive, consider that the first attached image showing the influence of deep uncertainty on global SLR projections (which indicates upper estimates of over 1m by 2050 and almost 5m by 2100); while the second image shows the distribution of world population impacted by a 5m SLR without considering any other climate change impacts.  The third image reminds readers (by replacing the magnitude curve with a consequence curve one gets risk in place of the 'Work' curve shown) that deep uncertainty carries much more risk with it than do left-tail consequences.
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KiwiGriff

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1943 on: November 17, 2019, 10:38:36 PM »
The Seneca effect
Quote
The Seneca effect, or Seneca cliff or Seneca collapse, is a mathematical model proposed by Ugo Bardi that addresses a class of problems in nature in which decline is faster than growth. This model is closely related to the work The Limits to Growth issued by the Club of Rome in the Seventies[1] and its main application is to describe various kind of economics given the condition of a shortage of fossil fuels, e.g. in relation to the Hubbert curve. However, unlike the Hubbert curve, the Seneca cliff shows asymmetry, which can take into account the delay of effects, such as pollution[2].

The term is named after the Roman philosopher and writer Seneca, who wrote Fortune is of sluggish growth, but ruin is rapid (Lucius Anneus Seneca, Letters to Lucilius, 91–63).

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

Ugo Bardi's blog.
https://cassandralegacy.blogspot.com/

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1944 on: November 18, 2019, 10:44:54 AM »
Gavin Schmidt recently posted the first image indicating that 2019 will almost certainly be the second warmest year in the observed record, even though ENSO is currently neutral.

The second image gives an idea how much GMSTA can vary on a monthly basis and shows that for about a month in 2016 we touched the 1.5C target above 'pre-industrial'.

The third image indicates that few people agree on what constitutes the 'pre-industrial' baseline, and that GMSTA may be about 0.1C higher above 'pre-industrial' if an optimal definition of that baseline were to be adopted.

Lastly, the fourth image shows that the West Antarctic is warming much more rapidly than the East Antarctic, indicating that the critical WAIS may be closer to more frequent ice surface melting than people who use optimistic averages for surface temperature anomalies.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1945 on: November 18, 2019, 04:24:00 PM »
This post is just a quick reminder that sea ice in the Arctic is becoming more fragile as during the past decade first year Arctic Sea Ice has come to dominate as indicated by the first image.

Furthermore, the last three images indicate that not only are key Antarctic ice shelves becoming more fragile due to thinning, but as due to warm basal water 'burning' upward through crevasses (see the second image), and due to saturation of the firn with both meltwater and ice (see the last two images, respectively):
« Last Edit: November 18, 2019, 05:50:18 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1946 on: November 18, 2019, 04:45:52 PM »
The linked reference indicates that: "When land adjustment is accounted for, however, the fixed sea surface temperature ERF values are generally 10–30% larger than ERFs derived using linear regression across all forcing agents …"; which, indicates that many atmosphere-ocean general circulation models my be underestimating effective radiative forcing (ERF).  For reference, I provide that attached image from Hansen et al. (2017) showing estimated changes in ERF from 1750 to 2016:

T. Tang et al. (02 April 2019), "Comparison of Effective Radiative Forcing Calculations Using Multiple Methods, Drivers, and Models", JGR Atmospheres", https://doi.org/10.1029/2018JD030188

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JD030188

Abstract
We compare six methods of estimating effective radiative forcing (ERF) using a set of atmosphere‐ocean general circulation models. This is the first multiforcing agent, multimodel evaluation of ERF values calculated using different methods. We demonstrate that previously reported apparent consistency between the ERF values derived from fixed sea surface temperature simulations and linear regression holds for most climate forcings, excluding black carbon (BC). When land adjustment is accounted for, however, the fixed sea surface temperature ERF values are generally 10–30% larger than ERFs derived using linear regression across all forcing agents, with a much larger (~70–100%) discrepancy for BC. Except for BC, this difference can be largely reduced by either using radiative kernel techniques or by exponential regression. Responses of clouds and their effects on shortwave radiation show the strongest variability in all experiments, limiting the application of regression‐based ERF in small forcing simulations.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1947 on: November 18, 2019, 04:55:00 PM »
...
Keywan Riahi et al. (January 2017), "The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview", Global Environmental Change, Volume 42, Pages 153-168, https://doi.org/10.1016/j.gloenvcha.2016.05.009

https://www.sciencedirect.com/science/article/pii/S0959378016300681

Extract: "While the SSPs were designed to represent different mitigation and adaptation challenges, the resulting narratives and quantifications span a wide range of different futures broadly representative of the current literature. This allows their subsequent use and development in new assessments and research projects. Critical next steps for the community scenario process will, among others, involve regional and sectoral extensions, further elaboration of the adaptation and impacts dimension, as well as employing the SSP scenarios with the new generation of earth system models as part of the 6th climate model intercomparison project (CMIP6)."


I thought that I should provide the attached image that compares key aspects (assumed: population growth, GDP growth,  energy demand and food demand) of the SS5-Baseline with the other SSP scenarios:
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1948 on: November 18, 2019, 05:23:55 PM »
While many individuals do not trust the IEA's energy projections, the linked summary of the IEA's 'World Energy Outlook 2019" and first attached image, indicate that there is no single silver bullet (such as EVs) to get to a Sustainable Development Scenario; but rather numerous parties will need to be convinced to cooperate to make climate progress, and that governments (unlike the Trump administration) would need to set standards to limit GHG emissions and to encourage sustainable research.  Unfortunately, per the last two images most governments around the world are falling far short of the actions need to reach a sustainable development scenario:

Title: "World Energy Outlook 2019"

https://www.iea.org/weo2019/

Extract: "Deep disparities define today’s energy world: oil markets and geopolitical tensions, carbon emissions and climate targets, the promise of energy for all and the lack of electricity access for 850 million people around the world.

World Energy Outlook 2019 explores these widening fractures in detail. It explains the impact of today’s decisions on tomorrow’s energy systems, and describes a pathway that enables the world to meet climate, energy access and air quality goals while maintaining a strong focus on the reliability and affordability of energy for a growing global population."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1949 on: November 18, 2019, 05:49:36 PM »

… key Antarctic ice shelves becoming more fragile due to thinning, but as due to warm basal water 'burning' upward through crevasses (see the second image), and due to saturation of the firn with both meltwater and ice (see the last two images, respectively):

Not only are key Antarctic ice shelves becoming more fragile in general, but the attached image shows some specific issues contributing to the fragility of the Thwaites Ice Tongue and the TEIS:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson