Ice Apocalypse - Multiple Meters Sea Level Rise

[AbruptSLR]

The linked article states that direct measurement of the ocean water at the grounding line (measured as part of the ITGC) indicate that the temperature of this water was 2C above freezing; and that the complete findings (from this part of this season's ITGC expedition) will be published in March, 2020:

Title: "Temperatures at a Florida-Size Glacier Alarm Scientists"

https://www.nytimes.com/2020/01/29/climate/thwaites-glacier-melting-antarctica.html

The researchers, working on the Thwaites Glacier, recorded water temperatures at the base of the ice of more than 2 degrees Celsius, or 3.8 degrees Fahrenheit, above the normal freezing point. Critically, the measurements were taken at the glacier’s grounding line, the area where it transitions from resting wholly on bedrock to spreading out on the sea as ice shelves.

It is unclear how fast the glacier is deteriorating: Studies have forecast its total collapse in a century and also in a few decades. The presence of warm water in the grounding line may support estimates at the faster range.

That is significant because the Thwaites, along with the Pine Island Glacier and a number of smaller glaciers, acts as a brake on part of the much larger West Antarctic Ice Sheet. Together, the two bigger glaciers are currently holding back ice that, if melted, would raise the world’s oceans by more than a meter, or about four feet, over centuries, an amount that would put many coastal cities underwater.
…
Drilling the hole — about 30 centimeters wide and 600 meters deep, or roughly one foot by 1,970 feet — and collecting the data took about 96 hours in subzero weather. The results of the study are expected to be published in March. The expedition was part of the International Thwaites Glacier Collaboration, a series of research projects aimed at understanding the glacier."

The linked article also cites the importance of turbulence of the warm water melting the groundling line ice in the subglacial cavities for Thwaites:

Title: "Scientists find record warm water in Antarctica, pointing to cause behind troubling glacier melt"

https://phys.org/news/2020-01-scientists-antarctica-glacier.html

Extract: "Aurora Basinski, an NYU graduate student who made the turbulence measurement, said, "From our observations into the ocean cavity at the grounding zone we observed not only the presence of warm water, but also its turbulence level and thus its efficiency to melt the ice shelf base."

Another researcher, Keith Nicholls, a scientist with the British Antarctic Survey, added, "This is an important result as this is the first time turbulent dissipation measurements have been made in the critical grounding zone of the West Antarctic Ice Sheet.""

[Tom_Mazanec]

Re: Reply #2693 "Atmospheric greenhouse gas concentrations"

Thank you AbruptSLR for that information regarding our calculation of CO_2e. Of course aerosols should be included in that formula as a negative radiative forcing. We now only need the pre-industrial aerosol concentrations to calculate the actual CO₂ equivalent GHG concentrations.

Any prospect of getting those concentrations, nanning?

[AbruptSLR]

Re: Reply #2693 "Atmospheric greenhouse gas concentrations"

Thank you AbruptSLR for that information regarding our calculation of CO_2e. Of course aerosols should be included in that formula as a negative radiative forcing. We now only need the pre-industrial aerosol concentrations to calculate the actual CO₂ equivalent GHG concentrations.

Any prospect of getting those concentrations, nanning?

There are many references like the linked references if you go to Google and search for pre-industrial aerosol radiative forcing:

Carslaw, K.S., Gordon, H., Hamilton, D.S. et al. Aerosols in the Pre-industrial Atmosphere. Curr Clim Change Rep 3, 1–15 (2017). https://doi.org/10.1007/s40641-017-0061-2

https://link.springer.com/article/10.1007/s40641-017-0061-2

Summary: "We review what is known about the microphysical, chemical, and radiative properties of aerosols in the pre-industrial atmosphere and the processes that control them. Aerosol properties were controlled by a combination of natural emissions, modification of the natural emissions by human activities such as land-use change, and anthropogenic emissions from biofuel combustion and early industrial processes. Although aerosol concentrations were lower in the pre-industrial atmosphere than today, model simulations show that relatively high aerosol concentrations could have been maintained over continental regions due to biogenically controlled new particle formation and wildfires. Despite the importance of pre-industrial aerosols for historical climate change, the relevant processes and emissions are given relatively little consideration in climate models, and there have been very few attempts to evaluate them. Consequently, we have very low confidence in the ability of models to simulate the aerosol conditions that form the baseline for historical climate simulations. Nevertheless, it is clear that the 1850s should be regarded as an early industrial reference period, and the aerosol forcing calculated from this period is smaller than the forcing since 1750. Improvements in historical reconstructions of natural and early anthropogenic emissions, exploitation of new Earth system models, and a deeper understanding and evaluation of the controlling processes are key aspects to reducing uncertainties in future."

&

Hamilton, D.S., Hantson, S., Scott, C.E. et al. Reassessment of pre-industrial fire emissions strongly affects anthropogenic aerosol forcing. Nat Commun 9, 3182 (2018). https://doi.org/10.1038/s41467-018-05592-9

https://www.nature.com/articles/s41467-018-05592-9

Abstract: "Uncertainty in pre-industrial natural aerosol emissions is a major component of the overall uncertainty in the radiative forcing of climate. Improved characterisation of natural emissions and their radiative effects can therefore increase the accuracy of global climate model projections. Here we show that revised assumptions about pre-industrial fire activity result in significantly increased aerosol concentrations in the pre-industrial atmosphere. Revised global model simulations predict a 35% reduction in the calculated global mean cloud albedo forcing over the Industrial Era (1750–2000 CE) compared to estimates using emissions data from the Sixth Coupled Model Intercomparison Project. An estimated upper limit to pre-industrial fire emissions results in a much greater (91%) reduction in forcing. When compared to 26 other uncertain parameters or inputs in our model, pre-industrial fire emissions are by far the single largest source of uncertainty in pre-industrial aerosol concentrations, and hence in our understanding of the magnitude of the historical radiative forcing due to anthropogenic aerosol emissions."

[AbruptSLR]

The linked reference indicates that when the AMOC slowed prior to the last interglacial (LIG) this warmed the subsurface ocean temperature adjoining marine, and marine-terminating, glaciers; which resulted in sea levels that were six to nine meters higher than today. 

Clark, P.U., He, F., Golledge, N.R. et al. Oceanic forcing of penultimate deglacial and last interglacial sea-level rise. Nature 577, 660–664 (2020). https://doi.org/10.1038/s41586-020-1931-7

https://www.nature.com/articles/s41586-020-1931-7

Abstract: "Sea-level histories during the two most recent deglacial–interglacial intervals show substantial differences despite both periods undergoing similar changes in global mean temperature and forcing from greenhouse gases. Although the last interglaciation (LIG) experienced stronger boreal summer insolation forcing than the present interglaciation, understanding why LIG global mean sea level may have been six to nine metres higher than today has proven particularly challenging. Extensive areas of polar ice sheets were grounded below sea level during both glacial and interglacial periods, with grounding lines and fringing ice shelves extending onto continental shelves. This suggests that oceanic forcing by subsurface warming may also have contributed to ice-sheet loss analogous to ongoing changes in the Antarctic and Greenland ice sheets. Such forcing would have been especially effective during glacial periods, when the Atlantic Meridional Overturning Circulation (AMOC) experienced large variations on millennial timescales, with a reduction of the AMOC causing subsurface warming throughout much of the Atlantic basin. Here we show that greater subsurface warming induced by the longer period of reduced AMOC during the penultimate deglaciation can explain the more-rapid sea-level rise compared with the last deglaciation. This greater forcing also contributed to excess loss from the Greenland and Antarctic ice sheets during the LIG, causing global mean sea level to rise at least four metres above modern levels. When accounting for the combined influences of penultimate and LIG deglaciation on glacial isostatic adjustment, this excess loss of polar ice during the LIG can explain much of the relative sea level recorded by fossil coral reefs and speleothems at intermediate- and far-field sites."

Edit: Obviously, this study supports the concept that ice-climate feedbacks can contribute to abrupt climate change, for example when the Beaufort Gyre eventually releases a surge of relative warm, relatively fresh, water into the North Atlantic it may likely slow the AMOC; which might lead to abrupt sea level rise.

[AbruptSLR]

Attached is an image that can help people better understand the different families/tiers of the SSP scenarios vs the RCP scenarios:

Some might prefer the first attached image

Edit: For reference, I provide the second attached image from Ed Hawkins showing the historical record thru 2019.

[AbruptSLR]

To me the linked commentary in Nature indicates that some consensus climate scientists are increasingly, and openly, wading into politics   Currently, the IPCC does not assign probabilities to any of their radiative forcing scenarios such as SRES, RCP and SSP, but Hausfather and Peters believe that they are entitled to retroactively assume that such scenarios are comprehensive and accurate and thus can be fitted (by likeminded consensus climate scientists) into a probability density function, PDF, matching the real world; which I do not agree with. 

First, none of the IPCC radiative forcing scenarios (or models) consider ice-climate induced radiative forcing; and they do not adequately characterize such uncertainties as aerosol-cloud feedbacks, and potential future carbon emissions from soils and due to permafrost degradation.

Second, both the first attached image from the article and the second attached image from Scripps (comparing RCP8.5 vs the observed record) indicate that it is not clear what emissions pathway that we are following and that without a big effort our business as usual radiative forcing pathway (including ice-climate, and other underestimated, feedback mechanisms associated) radiative forcing) may follow RCP8.5 for many decades to come.

Title: "Emissions – the ‘business as usual’ story is misleading", January 29, 2020 comment by Zeke Hausfather and Glen Peters, Nature 577, 618-620, doi: 10.1038/d41586-020-00177-3

https://www.nature.com/articles/d41586-020-00177-3

Extract: "Stop using the worst-case scenario for climate warming as the most likely outcome — more-realistic baselines make for better policy.
…
RCP8.5 was intended to explore an unlikely high-risk future.
…
Asking ‘what’s the worst that could happen?’ is a helpful exercise. It flags potential risks that emerge only at the extremes. RCP8.5 was a useful way to benchmark climate models over an extended period of time, by keeping future scenarios consistent. Perhaps it is for these reasons that the climate-modelling community suggested RCP8.5 “should be considered the highest priority”.
…
Those who are tasked with taking climate action on the basis of information from model scenarios are increasingly calling for a more risk-based approach to help with adaptation and mitigation. This approach accounts for the relative likelihood of different outcomes. Controversially, it requires researchers to assign probabilities to scenarios.
…
Therefore, it would be prudent to clearly outline the climate impacts for 3 °C in addition to those for 5 °C."

[AbruptSLR]

The linked news article indicates that at the Thwaites grounding line pronounced ice interactions were observed to be occurring "… driven by sediments at the line and from the rapid melting from warm ocean water.”

Title: "Researchers capture first-ever images of Thwaites Glacier foundations"

https://www.oceanographicmagazine.com/thwaites-glacier-foundations/

Extract: " “Icefin swam over 15 km round trip during five missions. This included two passes up to the grounding zone, including one where we got as close as we physically could to the place where the seafloor meets the ice,” said Schmidt, who is an associate professor in Georgia Tech’s School of Earth and Atmospheric Sciences. “We saw amazing ice interactions driven by sediments at the line and from the rapid melting from warm ocean water.”

Throughout the past 30 years, the amount of ice flowing into the sea from Thwaites and its neighbouring glaciers has almost doubled.
…
“We know that warmer ocean waters are eroding many of West Antarctica’s glaciers, but we’re particularly concerned about Thwaites. This new data will provide a new perspective of the processes taking place, so we can predict future change with more certainty,” said Keith Nicholls, an oceanographer from the British Antarctic Survey (BAS)."

[AbruptSLR]

To me the linked commentary in Nature indicates that some consensus climate scientists are increasingly, and openly, wading into politics   Currently, the IPCC does not assign probabilities to any of their radiative forcing scenarios such as SRES, RCP and SSP, but Hausfather and Peters believe that they are entitled to retroactively assume that such scenarios are comprehensive and accurate and thus can be fitted (by likeminded consensus climate scientists) into a probability density function, PDF, matching the real world; which I do not agree with. 

First, none of the IPCC radiative forcing scenarios (or models) consider ice-climate induced radiative forcing; and they do not adequately characterize such uncertainties as aerosol-cloud feedbacks, and potential future carbon emissions from soils and due to permafrost degradation.

Second, both the first attached image from the article and the second attached image from Scripps (comparing RCP8.5 vs the observed record) indicate that it is not clear what emissions pathway that we are following and that without a big effort our business as usual radiative forcing pathway (including ice-climate, and other underestimated, feedback mechanisms associated) radiative forcing) may follow RCP8.5 for many decades to come.

Title: "Emissions – the ‘business as usual’ story is misleading", January 29, 2020 comment by Zeke Hausfather and Glen Peters, Nature 577, 618-620, doi: 10.1038/d41586-020-00177-3

https://www.nature.com/articles/d41586-020-00177-3

...

In the linked article Michael Mann supports, and elaborates on, my position about the Hausfather and Peters (2020) commentary; however, I note that Mann does mention risks from ice-climate feedback mechanisms:

Title: "The STORY about the ‘business as usual’ story is misleading", by Michael Mann, January 29, 2019

https://michaelmann.net/content/story-about-%E2%80%98business-usual%E2%80%99-story-misleading

Extract: "A new commentary in the journal Nature by Zeke Hausfather and Glen Peters is making the rounds today.

The commentary is similar in content and outlook to a previous piece written by Hausfather on the website of the "Breakthrough Institute" a month ago, arguing that "business as usual" burning of fossil fuels will likely only lead to 3C warming, rather than the considerably higher range of 3-5C warming typically cited based on past IPCC projections. The latter piece was relied upon heavily in a recent Wall Street Journal op-ed by Breakthrough Institute founder Ted Nordhaus that is highly dismissive of the need for rapid reduction in global carbon emissions. The new piece has predictably led to some distorted headlines, for example this one by the BBC: "Climate change: Worst emissions scenario 'misleading' " which, itself, is ironically rather misleading.
…
The most recent peer-reviewed article I’m familiar with that covers this ground is a 2016 article by Rogelj et al in Nature. However, it comes up with higher numbers than Hausfater and Peters for “current policies”, with a central estimate of 3.2C warming, and as much as a 17% chance of warming in excess of 4.1C taking into account both the physical uncertainties and the scenario uncertainties. But that study used a simple climate model (MAGICC) that doesn’t account for non-linearities and, most importantly of all, doesn't include so-called “carbon cycle feedbacks”, that is to say, the feedback mechanism by which global warming can actually release more CO2 (or e.g. methane), adding further to the warming. Indeed, this deficiency applies to all studies that are based on specifying CO2 concentrations rather than emissions, and it applies to the current commentary by Hausfather & Peters.

We have seen a sobering example of the importance of these feedback mechanisms here in Australia where I am currently on sabbatical. In the catastrophic fires that have engulfed the continent (which were exacerbated and amplified by unprecedented heat and drought made possibly by climate change), roughly twice as much carbon escaped into the atmosphere as was produced by all of fossil fuel burning in Australia over the last year.

These sorts of amplifying “carbon cycle” feedback mechanisms (and this is just one example--there are many others including, for example, the potential release of frozen methane in the Arctic with warming) are not accounted for in the simple sorts of projections that Hausfather and others are using here. It is very likely that these feedback mechanisms will add substantially to the warming over the next century.

Combine that with the fact that the most recent (“CMIP6”) IPCC climate models seem to be showing the potential for considerably greater warming than the previous generation ("CMIP5") of IPCC models, and in my view, it is very difficult to rule out warming in excess of 4C under "business-as-usual" climate policies. Only with very strong mitigation efforts and rapid reduction of carbon emissions can we avoid such a scenario with a high degree of confidence."

[wdmn]

ASLR,

Do you think that if Hausfather and Peters has limited their claim to, "we are on the path to emitting xGt of CO2 through industrial activities by 2100" rather than "we are on the path to 3C" it would have been less controversial?

And a less speculative question:

Would you have found their paper less misleading and/or irresponsible?

[AbruptSLR]

ASLR,

Do you think that if Hausfather and Peters has limited their claim to, "we are on the path to emitting xGt of CO2 through industrial activities by 2100" rather than "we are on the path to 3C" it would have been less controversial?

And a less speculative question:

Would you have found their paper less misleading and/or irresponsible?

I think that the reason that RCP 8.5 assumes the use of a lot of coal (and other fossil fuels) is because people like to consider something that is in human control; which is why Hausfather and Peters attack this assumption while ignoring all of the other climate uncertainties including:

- Natural and anthropogenic aerosol radiative forcing and associate feedbacks (including cloud feedbacks);
- Likely carbon emissions from soil and permafrost;
- Likely natural methane emissions , and
- Ice-climate feedback mechanisms.

The IPCC never assigned any probabilities to the occurrence of RCP 8.5, because it is strictly a fabricated scenario merely intended to look at the risk of triggering non-linear feedbacks in the range of 5^oC by 2100.

So in my opinion their paper would have been less misleading/irresponsible if they acknowledged that the long/fat right-tail of the future climate GMSTA pdf is made of many different & interacting factors including the risks of scenarios/pathways with cascading feedback mechanisms and non-fossil fuel radiative forcings.

[wdmn]

Right, so in other words, they've chosen to take RCP 8.5 as a realistic representation of how we would get to a RF of 8.5W/m^2 rather than as a scenario for thinking about what would happen if we were to reach a RF of 8.5W/m^2 through some combination of direct anthro emissions + induced emissions + RF increases from other feedbacks.

So then why do the pathways even bother stating where the emissions come from if they're not supposed to represent realistically our pathway to a certain amount of RF? Why not just create a high end scenario called "if shit really goes wrong, one way or another" (pardon my french)?

EDIT:

To me the linked commentary in Nature indicates that some consensus climate scientists are increasingly, and openly, wading into politics

ASLR it's really interesting that you say this, because Peters and Hausfather (and Roger Pielke Jr. who has been involved in the efforts to bring a "reckoning" to RCP 8.5) have justified their article as being against "bad science," and against the "political rationale" for RCP 8.5:

Glen Peters on Twitter:
"They, as in the EPA? Sure, no doubt.

So, should I modify my science to (try to) meet political ends in the US? Or should I do good science?

SR15 said pledges took us to 3C, & no one seemed to have issue with that. In that sense, we are not being so radical?"

https://twitter.com/Peters_Glen/status/1223718299336310786

Roger Pielke Jr. on Twitter:
"I am hounded on this point daily (you are not being helpful to the cause!)

The demand for "noble cause corruption" in climate science is very real"

https://twitter.com/RogerPielkeJr/status/1223724045675319296

So what happens when scientists begin to split into two camps with both sides denouncing each other as practicing bad science that is politically motivated? How do we read this event, which is exceedingly important?

For a long time we got away with pretending that our scientific practices weren't completely interwoven with the political; both shoring up political power, and being shored up by political power; both revolutionary and conservative. And now there's a return of the suppressed! The scales fall from our eyes: the scientists were political actors all along!

[AbruptSLR]

wdmn,

First, it is useful to realize/remember that effectively everyone lives in a Markov Blanket (bubble) including scientists, yourself and myself, and thus understand/appreciate only part of the big picture.  This is one reason that George W. Bush could get away with stating that: "There is good science and there is bad science" (see the first linked article); because effectively all individuals typically view good science as something that reinforces their Markov Blanket, while they view bad science as something that disrupts their Markov Blanket.  When viewed in this way, only each individual can change their own Markov Blanket; and while others can provide an enriched information environment to facilitate refining ones own Markov Blanket; such others cannot be held responsible for changing your (or the global society's) Markov Blanket.

Title: "Abuses of Science: Case Studies - Examples of political interference with government science documented by the UCS Scientific Integrity Program, 2004-2009"

https://www.ucsusa.org/resources/abuses-science


Second, in my opinion, the scientific method is not a thing but rather it is a continuous/iterative process (see the first image) to search for a better/more-refined understanding of the truth rather than something that reinforces a given Markov Blanket.  However, today the global socio-economic system is dependent upon a Markov Blanket that has been engineered (using the engineering method, see the second image) largely based on the exploitation of the environment; without appropriately addressing the impacts of pollution (including GHG emissions) and other disbenefits.

Third, with this as background one can appreciate that Hausfather & Peters are promoting their Markov Blanket by implying that good science can err on the side of least drama (ESLD) in order to get decision makers to act [thus discounting right-tail risks not only such as RCP 8.5 (Watts/sqm) assumptions about fossil fuel use (especially coal use) but also radiative forcings and feedbacks not included in consensus science models, such as: unexpectedly high negative aerosol forcing, unexpectedly high deforestation, permafrost degradation, ice-climate feedbacks, etc.].

Fourth, greenwashing CMIP6 model projections with high values of ECS under SSP5 8.5 (Watts/sq m) by discounting both RCP 8.5 (Watts/sq m) and SSP5 8.5 (Watts/sq m) so as not to alarm people can be counter productive for many different reasons including:

- It can slow effective action to the point that many non-linear feedbacks and some tipping point cascades are activated.

- It can promote the implementation of adaptive measures that are ineffective and/or counterproductive.

- It can contribute to a backlog of ESLD science findings that future AR versions will blend with new findings; which will effectively slow the rate of refinement of advice given to decision makers.

- It can contribute to the belief that typically slow response feedback mechanisms can be relied upon to give society time to correct its current poor behavior; while in fact typically slow response trigger points such as the Thwaites Ice Tongue (see the third image) and the Beaufort Gyre may have already crossed over into tipping points that cannot be reversed by either cutting emissions and/or implementing solar geoengineering.

ASLR

Edit: I also note that if the WAIS were to collapse abruptly in the coming decades, the impact on the global socio-economic system would likely be sufficient to abruptly reduce anthropogenic aerosol emissions; and if this were to happen the net positive radiative forcing would increase abruptly.

[jai mitchell]

RCP 8.5 total greenhouse gas forcing
RCP 8.5 total anthropogenic forcing
50 years of expected carbon cycle emissions under 2C of warming (crowther et al 2017)

[KiwiGriff]

Roger Pielke Jr. on Twitter:
"I am hounded on this point daily (you are not being helpful to the cause!)

The demand for "noble cause corruption" in climate science is very real"

https://twitter.com/RogerPielkeJr/status/1223724045675319296

So what happens when scientists begin to split into two camps with both sides denouncing each other as practicing bad science that is politically motivated? How do we read this event, which is exceedingly important?

For a long time we got away with pretending that our scientific practices weren't completely interwoven with the political; both shoring up political power, and being shored up by political power; both revolutionary and conservative. And now there's a return of the suppressed! The scales fall from our eyes: the scientists were political actors all along!

Roger A. Pielke Jr.
(born November 2, 1968) is an American political scientist and professor, and was the director of the Sports Governance Center within the Department of Athletics at the Center for Science and Technology Policy Research at the University of Colorado Boulder.[1]

Another who pushes the same shtick .
Bjørn_Lomborg
Lomborg was an undergraduate at the University of Georgia, earned an M.A. degree in political science at the University of Aarhus in 1991, and a Ph.D. degree in political science at the University of Copenhagen in 1994.

When all you have is a hammer every thing is a nail
Those pushing the politicizing of science are in fact the ones qualified for doing it .
Neither of these is a climate scientist as such their opinions on climate science as as good as that of a fuckin plumber.

RCP 8.5 is an extreme case .
RCP 2.5 is also an extreme case .
They bracket the possible  reality's which lies between the two.
When  Pielke jnr starts the same crap over RCP 2.5 he might just have a point  but then he would not be able to spin his political agenda. 

.

[wdmn]

@ASLR
Thank you for introducing me to the concept of a Markov Blanket, and for the rest of your post.

I comprehend that our actions should be informed by the extreme right tail risks. I just wonder how it is best to go about doing that?

What I tried to draw out with my comment about science (as a practice) being interwoven with political networks, is that it doesn't matter what the scientists know if they can't convince enough of the right people within the polis to act in accordance, so they had better recognize how they are meshed with politics and how best to act in light of that.

RCP 8.5 has been a useful tool for scientists, the public and policy makers to think about right tail risks, but the fact that it accounts for its emissions through direct anthro sources only, and that it has probably been misused by the media, expose it to the very type of attack we've just seen. And a public that doesn't understand how science connects with political networks and have been raised with the idea that science is some purely neutral, objective practice are easily swayed by the claims that these scientists have become "politicized" and "corrupted."

@kiwigriff
The actual piece in nature was by Zeke Hausfather who runs carbonbrief and Glen Peters, who was a contributing author to AR5. They have quite a bit of credibility and sway; much more so than Roger or Lomberg.

EDIT: For example, Gregory Flato senior research scientist for Environment and Climate Change Canada and IPCC Bureau member regularly retweets Zeke Hausfather's articles.

You make a good point about 2.5; I almost asked Glen and Zeke about that yesterday; they conveniently did not ascribe probabilities (or likelihood) to the lowest pathways... however, they did pretty much rule out 1.5C or 2C as possible at this point in their comment.

Again, my point is that if we think -- and teach -- that science as a practice is not meshed with the political, we are exposing ourselves to just this kind of outbreak. Using RCP 8.5 to inform or push for policy DOES have political consequences; that's exactly the point of doing it!


EDIT:
I asked Glen Peters a couple of questions based off of things in this thread. Here's how that went

Questions
1) Are you willing to say we should also do away with RCP 2.6 and SSP1-1.9 as it is highly unlikely we will follow either of those pathways?
2) Is it not the case that probabilities were not assigned to RCP 8.5 because its intention is to explore the possibility of triggering non-linear feedbacks in the range of 5C by 2100; i.e. it was never intended to represent a realistic anthro "emissions" pathway?

Responses:
1) I would not do away with 1.9 or 2.6. At the end of the day, modelling groups have to decide where to put their limited computing resources.
2) RCP8.5 as an emission pathway is an outlier. Other RCP emissions may not get to RCP85 forcing. But, I would say the same as 1.

[nanning]

@ASLR
Thank you for introducing me to the concept of a Markov Blanket, and for the rest of your post.

Seconded!
AbruptSLR, your first paragraphs are closely touching on the problems I have in communicating my research. 'bubbles'/bias indeed. Great to read your text. Much appreciated.

[Shared Humanity]

I comprehend that our actions should be informed by the extreme right tail risks. I just wonder how it is best to go about doing that?

I believe the last IPCC report was clear on how to go about doing this.

1. Cut human CO2 emissions 40% by 2030.
2. Eliminate all human CO2 emissions by 2050.

Anything less than this and we are in serious trouble. What we are currently doing (CO2 emissions for 2019 set a new record, beating the previous record set in 2018.) and we are truly fucked.

[Shared Humanity]

My 1st grandchild, Rose, turns 2 in April. Her life is likely going to be a living hell. This saddens me beyond measure.

[AbruptSLR]

I comprehend that our actions should be informed by the extreme right tail risks. I just wonder how it is best to go about doing that?

I believe the last IPCC report was clear on how to go about doing this.

1. Cut human CO2 emissions 40% by 2030.
2. Eliminate all human CO2 emissions by 2050.

Anything less than this and we are in serious trouble. What we are currently doing (CO2 emissions for 2019 set a new record, beating the previous record set in 2018.) and we are truly fucked.

To partially respond to wdmn's point/question:

While the biggest part of my input for this thread will be to continue to clarify the nature of the current right-tail climate risks (which in coming decades may shift to become the most probable case); I appreciate that facing our true situation also entails some characterization of how to address related issues (which typically should be addressed in more detail in the 'Policy and solutions' folder).  In this regard, anthropogenic climate change is caused by human behavior; which evolved in a world where we (collectively) were never up against the limits of Earth Systems to absorb our messes.  Furthermore, human evolution was driven by the tenets of the 'Red Queen hypothesis' essentially where hosts and parasites engaged in an evolutionary 'arms race' to effectively stay in the same relative place as stated by the Red Queen in Lewis Carroll's 'Through the Looking-Glass', where she said: "Now, here, you see, it takes all the running you can do, to keep in the same place."

Title: "Red Queen hypothesis"

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

Now as human culture largely isolated people from being eaten by wild predators since the beginning of the Holocene, the Red Queen hypothesis (w.r.t. human behavior) has been dominated by conflict between different human groups (inter-human competition) to create a 'prisoner's dilemma' which temporarily rewards 'free-riders' (say like the Trump Administration) at the expense of better group cooperation (say like globalism).

Thus, to make better progress in the battle against climate risk, I would recommend that interested parties:

1. Develop strategies for holding free-riders/parasites politically at bay say by emphasizing the reality of the 'mutually assured' destruction nature of right-tailed climate risks in coming decades (such as the interactions of: Beaufort Gyre, MICI, methane emissions from thermokarst lakes, etc. see the attached image; however, I would change the coloring and range of the various Earth Systems tipping mechanisms).

2. Apply Nash Equilibrium (& Abductive Reasoning) logic to develop future radiative forcing cases for CMIP7 that better evaluate pathways/scenarios comparable to SSP3- 7.0, that seek to improve the common good even in the face of international-competition/chaos.  For example, say by NGOs marrying internet-based mass education with microloans to third world populations in order to minimize 'opportunity costs' and instead realizing the potential of third world populations to leapfrog fossil fuel based socio-economic systems.

[AbruptSLR]

The linked reference finds a possible link between Arctic and an increased frequency of El Nino events; which if verified also supports the concept that ECS is higher than CMIP5/AR5 previously recognized:

Charles F. Kennel and Elena Yulaeva (January 27, 2020), "Influence of Arctic sea-ice variability on Pacific trade winds", PNAS, https://doi.org/10.1073/pnas.1717707117

https://www.pnas.org/content/early/2020/01/21/1717707117

Significance
By 20th-century standards, the Central Pacific trade winds that drive the El Nino–Southern Oscillation feedback system to instability have been unusually strong in the 21st century. The annual summer melts of Arctic sea ice are up to twice as large in area as in the 20th century. Arctic sea ice, upper atmospheric circulation, surface wind, and sea-surface temperature data provide evidence that upper troposphere transport processes connect the increased summer losses of Arctic sea ice to the trade-wind and Central Pacific El Nino events characteristic of the present climate state. These results add to the evidence that loss of Arctic sea ice is having a major impact on climatic variability around the world.

Abstract
A conceptual model connecting seasonal loss of Arctic sea ice to midlatitude extreme weather events is applied to the 21st-century intensification of Central Pacific trade winds, emergence of Central Pacific El Nino events, and weakening of the North Pacific Aleutian Low Circulation. According to the model, Arctic Ocean warming following the summer sea-ice melt drives vertical convection that perturbs the upper troposphere. Static stability calculations show that upward convection occurs in annual 40- to 45-d episodes over the seasonally ice-free areas of the Beaufort-to-Kara Sea arc. The episodes generate planetary waves and higher-frequency wave trains that transport momentum and heat southward in the upper troposphere. Regression of upper tropospheric circulation data on September sea-ice area indicates that convection episodes produce wave-mediated teleconnections between the maximum ice-loss region north of the Siberian Arctic coast and the Intertropical Convergence Zone (ITCZ). These teleconnections generate oppositely directed trade-wind anomalies in the Central and Eastern Pacific during boreal winter. The interaction of upper troposphere waves with the ITCZ air–sea column may also trigger Central Pacific El Nino events. Finally, waves reflected northward from the ITCZ air column and/or generated by triggered El Nino events may be responsible for the late winter weakening of the Aleutian Low Circulation in recent years.

[vox_mundi]

https://phys.org/news/2020-02-ocean-gnawing-glaciers.html

Bathymetry Constrains Ocean Heat Supply to Greenland's Largest Glacier Tongue, Nature Geoscience (2020).
https://www.nature.com/articles/s41561-019-0529-x

The Greenland Ice Sheet is melting faster today than it did only a few years ago. The reason: it's not just melting on the surface—but underwater, too.

A team led by oceanographer Dr. Janin Schaffer from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) in Bremerhaven has now identified the source of this intense underwater melting. The conclusions of their study, which the experts have just released in the journal Nature Geoscience, are particularly unsettling because the melting phenomenon they discovered isn't unique to the 79° North Glacier, which means it could produce similar effects elsewhere.

For the purposes of the study, the researchers conducted the first extensive ship-based survey of the ocean floor near the glacier, which revealed the presence of a two-kilometre-wide trough, from the bottom of which comparatively warm water from the Atlantic is channelled directly toward the glacier.

But that's not all: in the course of a detailed analysis of the trough, Janin Schaffer spotted a bathymetric sill, a barrier that the water flowing over the seafloor has to overcome. Once over the hump, the water rushes down the back of the sill—and under the ice tongue. Thanks to this acceleration of the warm water mass, large amounts of heat from the ocean flow past the tongue every second, melting it from beneath.

To make matters worse, the layer of warm water that flows toward the glacier has grown larger: measured from the seafloor, it now extends 15 metres higher than it did just a few years ago. "The reason for the intensified melting is now clear," Schaffer says. "Because the warm water current is larger, substantially more warmth now makes its way under the ice tongue, second for second."

In order to determine whether the phenomenon only manifests at the 79° North Glacier or also at other sites, the team investigated a neighbouring region on Greenland's eastern coast, where another glacier, the Zachariæ Isstrøm, juts out into the sea, and where a large ice tongue had recently broken off from the mainland. Working from the surface of an ice floe, the experts measured water temperatures near the ocean floor. According to Schaffer: "The readings indicate that here, too, a bathymetric sill near the seafloor accelerates warm water toward the glacier. Apparently, the intensive melting on the underside of the ice at several sites throughout Greenland is largely produced by the form of the seafloor."

------------------------------------------

Warming Oceans Could Cause Antarctic Ice Sheet Collapse, Sea Level Rise
https://phys.org/news/2020-02-oceans-antarctic-ice-sheet-collapse.html

A new study suggests the Western Antarctic Ice Sheet is less stable than researchers once thought. As in the past, its collapse in the future is likely.

The finding is based in part on the results of a paper published this week in Nature, co-led by University of Wisconsin–Madison atmospheric scientist Feng He and Oregon State University's Peter Clark, which looks back at the last two time periods in which the planet transitioned from a glacial state, when ice sheets covered large swaths of the globe, into an interglacial state, such as the one we are in now.

Overall, the study found that warming below the surface of the planet's oceans is a significant contributor to ice sheet melt, particularly in the Antarctic, where a large portion of the ice sheet exists under the water.

During the last two transitions from glacial into interglacial periods, that warming was largely driven by the disruption of a process known as the Atlantic Meridional Overturning Circulation (AMOC), akin to an oceanic conveyor belt that carries warm waters northward and cold waters south.

Sub-surface warming, also referred to as oceanic forcing, was likely responsible for the collapse of the Western Antarctic Ice sheet during Earth's last interglacial period going back 125,000 years, which led to three meters of sea level rise. Overall, seas rose by up to nine meters, or nearly 30 feet, during the last interglacial period.

... The study found that AMOC was reduced in a single step at the transition of the last interglacial for roughly 7,000 years. During the transition into the current interglacial period, the Holocene, AMOC reduction lasted only about two-thirds as long and occurred in two steps.

"This is really scary because on paper at least, it shows that six to nine meters of sea level rise can occur with the same amount of global warming happening right now," says He.

Peter U. Clark et al. Oceanic forcing of penultimate deglacial and last interglacial sea-level rise, Nature (2020).

[wdmn]

Thanks again for an informative and well presented reply ASLR.

Just a final point on this, since I was not clear (both you and SharedHUmanity misunderstood me): I didn't mean what policies do you put in place to avoid the risk (implementing policy is the goal, and it's an explicitly political one), my question/point was about HOW do you effectively communicate the risk so that the goal is realized?

Remember that it is not to other scientists that the risk is being communicated; and there will be those amongst whom you must persuade who will have a fundamentally different world view that may include a distrust of scientists and science, etc.

(EDIT: to attempt to put this in another way: how do you persuade the Adults within the markov blankets that are resistant to the information being presented?)

When you think in this way, you realize that RCP 8.5 was always exposed to the critique Hausfather and Peters have recently given. And if the goals for using RCP 8.5 to communicate have always been political, then perhaps we could have done a better job designing RCP 8.5?

It's been known since the 19th century -- when Heinrich Hertz wrote about it -- that scientists rely on not only both empirical evidence and logical consistency, but also the rhetorical efficacy (persuasiveness) of their models/solutions. However, there is less thought about how this applies moving between other networks and collectives (not necessarily educated as scientists). We tend to think we will convince skeptics or deniers through more information (more graphs, etc), when in reality what's not needed is more information, but a different way of presenting that information. I don't blame scientists for this, I only am trying to point out how some of our deep beliefs about science and its relation to politics get in the way of us doing a better job.

[AbruptSLR]

...
When you think in this way, you realize that RCP 8.5 was always exposed to the critique Hausfather and Peters have recently given. And if the goals for using RCP 8.5 to communicate have always been political, then perhaps we could have done a better job designing RCP 8.5?
…

I believe that many of the points made by Hausfather and Peters commentary on RCP 8.5 are disingenuous as I suspect that they are reacting to the recent findings of many of the CMIP6 models that when following SSP5 - 8.5 (baseline) we are headed more towards 6.5 to 7C (see the first image) by 2100; and they decided to dumb down the discussion by focusing discussion on RCP 8.5 in CMIP5 thereby taking as a given that the worst case considered by climate science projects only a 5C increase by 2100 and then to discount the 5C number by pointing out that RCP 8.5 assumes that a lot of coal would be burned, thus side stepping the fact that SSP5 – 8.5 assumes the substitution of a lot of natural gas for coal (see the second image), as methane emissions has about the same impact on GMSTA as does coal. 

Furthermore, the third image shows that SSP5 – 8.5 assumes only a peak global population of about 8.5 billion people circa 2055; which is much less than that projected by the UN in 2019; which hints that SSP5 – 8.5 many not be a worst case.

Finally, the fourth image shows that RCP 8.5 is really about radiative forcing (i.e. the modelers felt that it was important to have at least one scenario with RF greater than, or equal to, 8.5 Watts per sq m. and not on any particular assumption that burning a lot of coal is the way to get there).

See also:

Title: "SSP/RCP-based scenarios: Implementation" by Detlef van Vuuren

https://www.iiasa.ac.at/web/home/about/events/8.detlef.ssps_2.pdf

&

Title: "The SSP (Shared Socioeconomic Pathways) and Scenarios
http://www.globalchange.umd.edu/data/gtsp/workshops/2012/Day1/EdmondsBas_SSPs2012-09-19.pdf

[AbruptSLR]

While I have already linked to previous article about the how the MELT project with the ITGC field survey in the 2019-2020 season found ocean water with temperatures about 2C above freezing at the pressure and salinity found at the grounding line of the Thwaites Glacier, I do so again in this post to emphasis that what it was obvious that such warm water was present in the subglacial cavities at the grounding line of the Thwaites Glacier when it was found that these subglacial cavities have been expanding rapidly in the past several years; nevertheless, consensus climate science discounted this fact until it was actually measured.  Thus, assessment of the risk of a MICI-type of collapse near the base of the Thwaites Ice Tongue (such as that made by Edwards et al 2019 Revisiting Antarctic ice loss due to marine ice-cliff instability, Nature, doi:10.1038/s41586-019-0901-4); should now theoretically be updated to reflect these new findings, but that will not happen for AR6:

Title: "Scientists Find Record Warm Water in Antarctica, Pointing to Cause Behind Troubling Glacier Melt"

https://www.nyu.edu/about/news-publications/news/2020/january/scientists-find-record-warm-water-in-antarctica--pointing-to-cau.html

Extract: "“Warm waters in this part of the world, as remote as they may seem, should serve as a warning to all of us about the potential dire changes to the planet brought about by climate change,” explains David Holland, director of New York University’s Environmental Fluid Dynamics Laboratory and NYU Abu Dhabi’s Center for Global Sea Level Change, which conducted the research. “If these waters are causing glacier melt in Antarctica, resulting changes in sea level would be felt in more inhabited parts of the world.”

The recorded warm waters—more than two degrees above freezing—flow beneath the Thwaites Glacier, which is part of the Western Antarctic Ice Sheet. The discovery was made at the glacier’s grounding zone—the place at which the ice transitions between resting fully on bedrock and floating on the ocean as an ice shelf and which is key to the overall rate of retreat of a glacier."
&

Title: "Scientists alarmed to discover warm water at "vital point" beneath Antarctica's "doomsday glacier""

https://www.cbsnews.com/news/climate-change-thwaites-melting-scientists-warm-water-antarctica-doomsday-glacier/

""From our observations into the ocean cavity at the grounding zone we observed not only the presence of warm water, but also its turbulence level and thus its efficiency to melt the ice shelf base," said Aurora Basinski, an NYU graduate student who made the turbulence measurement."

[AbruptSLR]

Per the attached image Hausfather notes that January 2020 was the second warmest January on record (just below that for 2016 following a Super El Nino event); however, there has been no El Nino behavior during the 2019-2020 ENSO season; which suggests that January 2020 is so warm due to anthropogenic radiative forcing.

[wdmn]

One further note on climate science and politics: our old friend James Hansen came out with a statement recently in which he reiterated his support for a carbon tax and also nuclear power. The statement is available here:

http://www.columbia.edu/~jeh1/mailings/2020/20200124_NoTimeForDespair.pdf

In it, he also had some less than flattering words about the IPCC:

"The ridiculous climate statement – even from politicians – goes something like: “we have 10
years, 7 months, x days until the carbon budget is used up and we are doomed!” IPCC should be
censured for initiating that nonsense, and wrongly frightening young people. We are already in
carbon overshoot, but that does not mean that the problem is unsolvable.
Instead of despair, we should celebrate how far we have come."

He also recently reiterated his belief that ECS is most likely 2.8-3C.


Addendum:
For those wondering, the temperature anomaly given in ASLR's post previous to this one can be converted to a pre-industrial baseline by adding 0.63C -> ~1.24C.

[vox_mundi]

US Sea-Level Report Cards: 2019 Data Adds to Trend in Acceleration
https://phys.org/news/2020-02-sea-level-cards-trend.html

The annual update of their sea level "report cards" by researchers at William & Mary's Virginia Institute of Marine Science adds evidence of an accelerating rate of sea-level rise at nearly all tidal stations along the U.S. coastline. The latest report cards were published on January 30th.



The interactive charts are available online at: http://www.vims.edu/sealevelreportcards

The project's founder, VIMS emeritus professor John Boon, says "the key message from the 2019 report cards is a clear trend toward acceleration in rates of sea-level rise at 25 of our 32 tide-gauge stations. Acceleration can be a game changer in terms of impacts and planning, so we really need to pay heed to these patterns."

VIMS marine scientist Molly Mitchell says "seeing acceleration at so many of our stations suggests that—when we look at the multiple sea-level scenarios that NOAA puts out based on global models—we may be moving towards the higher projections." ... "We have increasing evidence from the tide-gauge records that these higher sea-level curves need to be seriously considered in resilience-planning efforts"

... VIMS' 2019 report cards show that sea level rose at 27 of the 32 monitored stations. Perhaps even more telling is that water levels at 25 of the 32 stations rose at a higher rate in 2019 than in 2018. The five stations where relative sea level fell were all on the U.S. West Coast, four of these in Alaska, where the continued rise of coastal mountains generates sharp decreases in sea level relative to land.

The three highest rates of sea-level rise in 2019 occurred along the Gulf Coast at Grand Isle, Louisiana (7.93 millimeters per year) and at Rockport (6.95 mm/yr) and Galveston (6.41 mm/yr) Texas. Rockport also topped all 32 stations in its rate of acceleration, at 0.26 mm per year per year. If this continues, sea level here will be 0.82 meters (2.69 feet) higher in 2050 compared to 1992. Grand Isle and Galveston showed significant but much more moderate acceleration rates in 2019, at 0.05 mm/yr2 and 0.09 mm/yr2, respectively. The 2050 projections for sea-level rise at these sites is thus appreciably lower: 0.54 m (1.77 ft) at Grand Isle and 0.51 m (1.67 ft) at Galveston.

... Boon and Mitchell note that acceleration at these and other locations sharply increases their quadratic, "best-estimate" sea-level projections for 2050. The difference between the linear rates used in NOAA's sea-level forecasts and the non-linear, accelerating rates used in VIMS' report cards can lead to sharply different forecasts of our sea-level future. ...

[AbruptSLR]

...
He also recently reiterated his belief that ECS is most likely 2.8-3C.


Addendum:
For those wondering, the temperature anomaly given in ASLR's post previous to this one can be converted to a pre-industrial baseline by adding 0.63C -> ~1.24C.

For those who forget, I again provide the attached image from Hansen & Sato 2012; where it is clear that Hansen uses ECS to mean the fast feedback mechanisms only, and that ice-climate feedbacks need to be added on top of that value in order to get the total effective ECS value.

[AbruptSLR]

I thought that I would make a few more comments about Hausfather and Peters' 2020 commentary including:

1. They did not engage in any of the work required to estimate the probabilities for possible future radiative forcing scenarios (instead they indicated that they would just assume probabilities for the RCP scenarios which the IPCC said that it was inappropriate to assign probabilities to).  In this regard, I note that: a) there are many reasons to believe that coal will die a slower death than many seem to assume, including that China is actively marketing their coal burning technology to adjoining countries; and b) fracking is providing increasing amounts of natural gas with a carbon footprint comparable to coal.

2. Even if SSP – 8.5, or RCP 8.5, scenario is roughly followed through about 2040, this amount of radiative forcing many very well be sufficient to trigger radiative forcing mechanisms not adequately evaluated by either CMIP5, or CMIP6, including the activation of such mechanisms by roughly 2040 as: a) the Beaufort Gyre releasing significant quantities of relatively fresh & warm water into the rest of the Arctic Ocean and then into the North Atlantic; b) the Thwaites Glacier may have initiated a MICI-type of collapse; and c) permafrost regions may begin releasing both CO2 and methane in a nonlinear fashion.

3. Many of the CMIP6 with excellent track records have projected ECS values well over 3C and as high as 5.6C.

4. Climate risk is equal to probability time consequences and most consensus climate science projections of consequences seriously under-report both the impacts and the timeframe of the coming climate crisis.

[AbruptSLR]

…
... my question/point was about HOW do you effectively communicate the risk so that the goal is realized?

Remember that it is not to other scientists that the risk is being communicated; and there will be those amongst whom you must persuade who will have a fundamentally different world view that may include a distrust of scientists and science, etc.

(EDIT: to attempt to put this in another way: how do you persuade the Adults within the markov blankets that are resistant to the information being presented?)

When you think in this way, you realize that RCP 8.5 was always exposed to the critique Hausfather and Peters have recently given. And if the goals for using RCP 8.5 to communicate have always been political, then perhaps we could have done a better job designing RCP 8.5?

It's been known since the 19th century -- when Heinrich Hertz wrote about it -- that scientists rely on not only both empirical evidence and logical consistency, but also the rhetorical efficacy (persuasiveness) of their models/solutions. However, there is less thought about how this applies moving between other networks and collectives (not necessarily educated as scientists). We tend to think we will convince skeptics or deniers through more information (more graphs, etc), when in reality what's not needed is more information, but a different way of presenting that information. I don't blame scientists for this, I only am trying to point out how some of our deep beliefs about science and its relation to politics get in the way of us doing a better job.

I will make one brief point about RCP 8.5; which is that its origins had roots in the 'peak oil' belief that both conventional oil and conventional natural gas would run-out soon, and thus it would take massive amounts of coal use to reach this scenario.  Obviously, fracking (& other oil/gas industry technologies) made it clear that 'peak oil' was a lot further off than most consensus climate scientists thought when RCP 8.5 was developed; which is one reason that SSP5 - 8.5 assumes the use of a lot of natural gas in the coming decades to replace coal use; however, many people still assume that they can ignore natural gas use because it currently has a life of about 12.7-years in the atmosphere which is again left over thinking from the RCP scenario days when it was assumed that conventional natural gas would run out soon (while in fact natural gas has about the same carbon foot print as coal, especially when considering fracked natural gas).  Thus Hausfather and Peters were playing games with out-of-date Markov Blankets (of both peak oil and clean gas as an energy bridge); and I point out that these out-of-date myths (Markov Blankets) indicated to policy makers that they did need to take any climate action because: fossil fuels were running out and renewables would soon be so cheap that there was not need for them to stick their collective necks out.  While the truth of the make is that there is currently plenty of cheap fossil fuels available (see the attached image) through at least 2050 to follow SSP5 - 8.5; and after that time ice-climate feedbacks, and other non-linear carbon feedbacks (like thermokarst lake methane emissions), may well be triggered to get to 8.5 Watts per sq m radiative forcing by 2100 even if our global socio-economic system begins to collapse by 2050 (which if it were to collapse would abruptly reduce the negative radiative forcing associated with anthropogenic aerosol emissions).

[AbruptSLR]

Climate change is complex, and while the authors of the linked reference (& associated linked article) focus on the positive aspects of the world's oceans kinetic energy (KE) increasing in the 0 to 2,000 m depth range since the 1990's due to climate change driven winds; such as that climate change induced increases in heat energy will be more effectively distributed around the world and into the deep ocean; however, I note that this research does not focus on the gravitational energy driving the MOC associate with the thermohaline driving energy.  Thus, in a more realistic interpretation of the implications of authors finding would need to include consideration of:

a) The increasing KE of surface ocean currents in the Southern Ocean is accelerating upwelling of warm CDW that is accelerating associated ice mass loss in key marine glaciers like the PIG and the Thwaites Glacier; which increases the likelihood of stronger ice-climate feedback in coming decades which could slow the MOC due to thermohaline effects;
b) Due to the complexities of the ENSO phenomena this higher surface ocean current velocities in the Equatorial Pacific could lead to stronger future El Nino events; and
c) The associated increased upwelling of deep ocean water on the west coasts of continents like South America etc. could lead to more rapid acidification of surface ocean waters in such typically biologically rich areas; which could have serious impacts on these local marine organisms.

Shijian Hu et al. (05 Feb 2020), "Deep-reaching acceleration of global mean ocean circulation over the past two decades", Science Advances, Vol. 6, no. 6, eaax7727, DOI: 10.1126/sciadv.aax7727

https://advances.sciencemag.org/content/6/6/eaax7727

Abstract: "Ocean circulation redistributes Earth’s energy and water masses and influences global climate. Under historical greenhouse warming, regional ocean currents show diverse tendencies, but whether there is an emerging trend of the global mean ocean circulation system is not yet clear. Here, we show a statistically significant increasing trend in the globally integrated oceanic kinetic energy since the early 1990s, indicating a substantial acceleration of global mean ocean circulation. The increasing trend in kinetic energy is particularly prominent in the global tropical oceans, reaching depths of thousands of meters. The deep-reaching acceleration of the ocean circulation is mainly induced by a planetary intensification of surface winds since the early 1990s. Although possibly influenced by wind changes associated with the onset of a negative Pacific decadal oscillation since the late 1990s, the recent acceleration is far larger than that associated with natural variability, suggesting that it is principally part of a long-term trend."

Extract: "We refer to “ocean circulation” as the horizontal movement of seawater in terms of a monthly average. For ocean circulation, the usable energy is mainly in the form of kinetic energy (KE), available gravitational potential energy (APE), available internal energy, and a residual term related to dissipation of KE due to molecular and small-scale diffusion and subgrid processes."

Caption for attached images: "Fig. 2 Horizontal and vertical distribution of long-term KE change. (A) Linear trend of oceanic KE averaged over the upper 2000-m layer (shaded color, unit in 103 J m−2 decade−1) during 1991–2011 from the ensemble mean of the ECMWF ORA-S4, ORA-S3, ECCO2, GODAS, and GFDL ECDA. Area where statistical significance is above the 99% confidence level is highlighted by black dots. (B) Vertical distribution of linear trend (blue line) of ensemble and global mean KE′ and the linear trend in percentage (embedded red line, relative to the climatological KE at each depth). Black dots indicate the 99% confidence level, and shaded area denotes the error in the trend. (C) Time-depth plot of ensemble mean KE′ (color shading and black contour lines) integrated over the global ocean. KE′ is calculated by subtracting the time means over 1991–2011 from the monthly series and low-pass filtering with a cutoff period of 25 months. (D) As in (C), but for the AGVA during 2005–2010."

&

Title: "Ocean currents are getting faster"

https://www.livescience.com/ocean-currents-speeding-up.html

Extract: "New research, published today (Feb. 6) in the journal Science Advances, finds that this acceleration is occurring around the globe, with the most noticeable effects in the tropical latitudes. The enhanced speed isn’t just at the ocean’s surface, but is occurring as deep as 6,560 feet (2,000 meters).
…
Winds over the ocean have been picking up at a rate of 1.9% per decade, the researchers found. This increase in wind speed transfers energy to the ocean’s surface, and subsequently, deeper waters. About 76% of the upper 6,560 feet (2,000 m) of the oceans have seen an increase in kinetic energy since the 1990s. Overall, ocean current speeds have crept up about 5% per decade since the early 1990s, the study found."

[rboyd]

One further note on climate science and politics: our old friend James Hansen came out with a statement recently in which he reiterated his support for a carbon tax and also nuclear power. The statement is available here:

http://www.columbia.edu/~jeh1/mailings/2020/20200124_NoTimeForDespair.pdf

In it, he also had some less than flattering words about the IPCC:

"The ridiculous climate statement – even from politicians – goes something like: “we have 10
years, 7 months, x days until the carbon budget is used up and we are doomed!” IPCC should be
censured for initiating that nonsense, and wrongly frightening young people. We are already in
carbon overshoot, but that does not mean that the problem is unsolvable.
Instead of despair, we should celebrate how far we have come."

He also recently reiterated his belief that ECS is most likely 2.8-3C.


Addendum:
For those wondering, the temperature anomaly given in ASLR's post previous to this one can be converted to a pre-industrial baseline by adding 0.63C -> ~1.24C.

That Hansen note is utterly delusional "Instead of despair, we should celebrate how far we have come." he says! Like we have come to an emissions level over 60% higher than in 1990, and we should be proud of it? He has certainly jumped the eco-modernist and geo-engineering shark, as per his statements below ... then the sell for nuclear. I used to respect him a lot, very sad.

Massive amounts of power will be needed for drawing down atmospheric CO2, for producing
liquid fuels, and for desalinization, as well as for an electricity-dominant energy system. Young
people will get fracked and gassed, if there is no viable alternative for baseload electric power ... Yes, I know, young people are afraid of hurting their Boomer hippie grandparents’ feelings. Of
course, they meant well when they paraded against nuclear power. It was identified as the next
villain, after the Viet Nam war ended. But what is more important: their feelings or your future?

[AbruptSLR]

Esperanza Base is at the Northern tip of the Antarctic Peninsula and it reported a daily high temperature of 18.3 °C (65 °F).

If confirmed,  this will be a new all-time record high temperature ever observed anywhere in the continent of Antarctica.

[AbruptSLR]

Per the attached image the ECMWF ERA5 reanalysis dataset for January 2020 indicates both that January 2020 was the warmest January on record, and that 2020 may become the warmest year on record.

Edit, see also:

https://climate.copernicus.eu/surface-air-temperature-january-2020

[AbruptSLR]

The linked article cites research that not only links the increased accumulation of freshwater in the
Beaufort Gyre (in recent decades) to Arctic Sea Ice loss, but also identifies a positive feedback between associated increased turbulence from the Beaufort Gyre and increasing Arctic Sea Ice loss.  This is not good news.

Title: "Arctic Ice Melt Is Changing Ocean Currents", February 6, 2020 by NASA - JPL

https://www.jpl.nasa.gov/news/news.php?feature=7590

Extract: "A major ocean current in the Arctic is faster and more turbulent as a result of rapid sea ice melt, a new study from NASA shows. The current is part of a delicate Arctic environment that is now flooded with fresh water, an effect of human-caused climate change.

Using 12 years of satellite data, scientists have measured how this circular current, called the Beaufort Gyre, has precariously balanced an influx of unprecedented amounts of cold, fresh water - a change that could alter the currents in the Atlantic Ocean and cool the climate of Western Europe.
…
But the since the 1990s, the gyre has accumulated a large amount of fresh water - 1,920 cubic miles (8,000 cubic kilometers) - or almost twice the volume of Lake Michigan. The new study, published in Nature Communications, found that the cause of this gain in freshwater concentration is the loss of sea ice in summer and autumn. This decades-long decline of the Arctic's summertime sea ice cover has left the Beaufort Gyre more exposed to the wind, which spins the gyre faster and traps the fresh water in its current.
…
Scientists have been keeping an eye on the Beaufort Gyre in case the wind changes direction again. If the direction were to change, the wind would reverse the current, pulling it counterclockwise and releasing the water it has accumulated all at once.

"If the Beaufort Gyre were to release the excess fresh water into the Atlantic Ocean, it could potentially slow down its circulation. And that would have hemisphere-wide implications for the climate, especially in Western Europe," said Tom Armitage, lead author of the study and polar scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
...
"We don't expect a shutting down of the Gulf Stream, but we do expect impacts. That's why we're monitoring the Beaufort Gyre so closely," said Alek Petty, a co-author on the paper and polar scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

The study also found that, although the Beaufort Gyre is out of balance because of the added energy from the wind, the current expels that excess energy by forming small, circular eddies of water. While the increased turbulence has helped keep the system balanced, it has the potential to lead to further ice melt because it mixes layers of cold, fresh water with relatively warm, salt water below. The melting ice could, in turn, lead to changes in how nutrients and organic material in the ocean are mixed, significantly affecting the food chain and wildlife in the Arctic. The results reveal a delicate balance between wind and ocean as the sea ice pack recedes under climate change."

Edit, see also:

Armitage, T.W.K., Manucharyan, G.E., Petty, A.A. et al. Enhanced eddy activity in the Beaufort Gyre in response to sea ice loss. Nat Commun 11, 761 (2020). https://doi.org/10.1038/s41467-020-14449-z

https://www.nature.com/articles/s41467-020-14449-z?utm_medium=affiliate&utm_source=commission_junction&utm_campaign=3_nsn6445_deeplink_PID8099906&utm_content=deeplink

Abstract: "The Beaufort Gyre freshwater content has increased since the 1990s, potentially stabilizing in recent years. The mechanisms proposed to explain the stabilization involve either mesoscale eddy activity that opposes Ekman pumping or the reduction of Ekman pumping due to reduced sea ice–ocean surface stress. However, the relative importance of these mechanisms is unclear. Here, we present observational estimates of the Beaufort Gyre mechanical energy budget and show that energy dissipation and freshwater content stabilization by eddies increased in the late-2000s. The loss of sea ice and acceleration of ocean currents after 2007 resulted in enhanced mechanical energy input but without corresponding increases in potential energy storage. To balance the energy surplus, eddy dissipation and its role in gyre stabilization must have increased after 2007. Our results imply that declining Arctic sea ice will lead to an increasingly energetic Beaufort Gyre with eddies playing a greater role in its stabilization."

Edit 2:
Caption for the attached image: "a Before and b after 2007, including the wind work, W (comprised of atmosphere-ocean, Wao, and ice–ocean, Wio, components), available potential energy (APE), and eddy dissipation, Weddy. The atmosphere and ocean circulations are illustrated by ua and ug, respectively. The size of the arrows/vectors represents their relative strength. The loss of sea ice after 2007 led to increased wind energy input to the BG, increased APE, and increased energy dissipation and freshwater stabilization by eddies."

[AbruptSLR]

The linked reference confirms that polar amplification is enhanced by the upward flux of ocean heat content toward the surface of the Arctic Ocean:

E. Beer et al. (03 February 2020), "Polar amplification due to enhanced heat flux across the halocline", Geophysical Research Letters, https://doi.org/10.1029/2019GL086706

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086706?af=R

Abstract
Polar amplification is a widely discussed phenomenon, and a range of mechanisms have been proposed to contribute to it, many of which involve atmospheric and surface processes. However, substantial questions remain regarding the role of ocean heat transport. Previous studies have found that ocean heat transport into the Arctic increases under global warming, but the reasons behind this remain unresolved. Here, we investigate changes in oceanic heat fluxes and associated impacts on polar amplification using an idealized ocean‐‐sea ice‐‐climate model of the Northern Hemisphere. We show that beneath the sea ice, vertical temperature gradients across the halocline increase as the ocean warms, since the surface mixed layer temperatures in ice‐covered regions are fixed near the freezing point. These enhanced vertical temperature gradients drive enhanced horizontal heat transport into the polar region and can contribute substantially to polar amplification.

Plain Language Summary
The Arctic region is warming at a faster rate than the rest of the globe. A number of mechanisms that may contribute to this have been identified, the most well‐known being the surface albedo feedback which occurs due to the higher reflectivity of ice compared to open water. However, substantial gaps remain in our understanding of what drives the polar amplification of global warming, and projections of how much the polar regions will warm in the future vary widely. Here, we look at the contribution to Arctic warming from the vertical transfer of heat in the upper ocean. In the Arctic Ocean, a large amount of heat is stored in relatively warm waters at depth, with a cold layer of water and sea ice cover above. The results indicate that the amount of heat from this warm water that reaches the sea ice cover will increase under global warming, enhancing the rate of warming in the Arctic region.

[AbruptSLR]

I am reposting Zelinka et al (2020) and am posting O'Connor et al (2020) [which indicates that present day effective radiative forcing, ERF, is greater than the sum of the individual GHG ERFs due to nonlinear interactions] in order to point out that if (with continued anthropogenic forcing) the majority of Earth Systems contributing to climate sensitivity are nonlinear, then consensus climate science will be slower to acknowledge such a situation for reasons including:

1. As models are not equal, one would expect nonlinear Earth Systems to increase the spread of projected ECS values as is the case for the 1.8 – 5.6K range of ECS values from CMIP6 reported by Zelinka et al (2020); which is a higher range than that reported by either CMIP5 or AR5.

2. As AR6 will blend the climate sensitivity values reported by CMIP6 with values of climate sensitivity calculated from both recorded observations and from paleodata; this will have the effect of underreporting nonlinear behavior as recorded observations are limited and paleodata is noisy.

3. Decision makers will defer taking effective action to limit anthropogenic radiative forcing until consensus climate science reduces their uncertainty w.r.t. projected climate sensitivity; which will work to activate more nonlinearity in more Earth Systems (the majority of which have positive feedbacks); which will serve to result in higher realized values of climate sensitivity this century.

Mark D. Zelinka et al. (03 January 2020), "Causes of Higher Climate Sensitivity in CMIP6 Models", Geophysical Research Letters, https://doi.org/10.1029/2019GL085782

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085782

Abstract
Equilibrium climate sensitivity, the global surface temperature response to CO2 doubling, has been persistently uncertain. Recent consensus places it likely within 1.5–4.5 K. Global climate models (GCMs), which attempt to represent all relevant physical processes, provide the most direct means of estimating climate sensitivity via CO2 quadrupling experiments. Here we show that the closely related effective climate sensitivity has increased substantially in Coupled Model Intercomparison Project phase 6 (CMIP6), with values spanning 1.8–5.6 K across 27 GCMs and exceeding 4.5 K in 10 of them. This (statistically insignificant) increase is primarily due to stronger positive cloud feedbacks from decreasing extratropical low cloud coverage and albedo. Both of these are tied to the physical representation of clouds which in CMIP6 models lead to weaker responses of extratropical low cloud cover and water content to unforced variations in surface temperature. Establishing the plausibility of these higher sensitivity models is imperative given their implied societal ramifications.

Plain Language Summary
The severity of climate change is closely related to how much the Earth warms in response to greenhouse gas increases. Here we find that the temperature response to an abrupt quadrupling of atmospheric carbon dioxide has increased substantially in the latest generation of global climate models. This is primarily because low cloud water content and coverage decrease more strongly with global warming, causing enhanced planetary absorption of sunlight—an amplifying feedback that ultimately results in more warming. Differences in the physical representation of clouds in models drive this enhanced sensitivity relative to the previous generation of models. It is crucial to establish whether the latest models, which presumably represent the climate system better than their predecessors, are also providing a more realistic picture of future climate warming.

&

O'Connor, F. M., Abraham, N. L., Dalvi, M., Folberth, G., Griffiths, P., Hardacre, C., Johnson, B. T., Kahana, R., Keeble, J., Kim, B., Morgenstern, O., Mulcahy, J. P., Richardson, M. G., Robertson, E., Seo, J., Shim, S., Teixeira, J. C., Turnock, S., Williams, J., Wiltshire, A., and Zeng, G.: Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2019-1152, in review, 2020.

https://www.atmos-chem-phys-discuss.net/acp-2019-1152/

Abstract. Quantifying forcings from anthropogenic perturbations to the Earth System (ES) is important for understanding changes in climate since the pre-industrial period. In this paper, we quantify and analyse a wide range of present-day (PD) anthropogenic climate forcings with the UK's Earth System Model (ESM), UKESM1, following the protocols defined by the Radiative Forcing Model Intercomparison Project (RFMIP) and the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). In particular, by quantifying effective radiative forcings (ERFs) that include rapid adjustments within a full ESM, it enables the role of various climate-chemistry-aerosol-cloud feedbacks to be quantified.

Global mean ERFs are 1.83, 0.13, −0.33, and 0.93 W m−2 at the PD (Year 2014) relative to the pre-industrial (PI; Year 1850) for carbon dioxide, nitrous oxide, ozone-depleting substances, and methane, respectively. The PD total greenhouse gas ERF is 2.89 W m−2, larger than the sum of the individual GHG ERFs.

UKESM1 has an aerosol forcing of −1.13 W m−2. A relatively strong negative forcing from aerosol-cloud interactions and a small negative instantaneous forcing from aerosol-radiation interactions are partially offset by a substantial forcing from black carbon absorption. Internal mixing and chemical interactions mean that neither the forcing from aerosol-radiation interactions nor aerosol-cloud interactions are linear, making the total aerosol ERF less than the sum of the individual speciated aerosol ERFs.

Tropospheric ozone precursors, in addition to exerting a positive forcing due to ozone, lead to oxidant changes which in turn cause an indirect aerosol ERF, altering the sign of the net ERF from nitrogen oxide emissions. Together, aerosol and tropospheric ozone precursors (near-term climate forcers, NTCFs) exert a global mean ERF of −1.12 W m−2, mainly due to changes in the cloud radiative effect. There is also a negative PD ERF from land use (−0.32 W m−2). It is outside the range of previous estimates, and is most likely due to too strong an albedo response. In combination, the net anthropogenic ERF is potentially biased low (1.61 W m−2) relative to other estimates, due to the inclusion of non-linear feedbacks and ES interactions.

By including feedbacks between greenhouse gases, stratospheric and tropospheric ozone, aerosols, and clouds, some of which act non-linearly, this work demonstrates the importance of ES interactions when quantifying climate forcing. It also suggests that rapid adjustments need to include chemical as well as physical adjustments to fully account for complex ES interactions.

[AbruptSLR]

Consensus climate scientists like Hausfather and Peters (2020) who indicate that model projections using high-end radiative forcing scenarios like RCP 8.5, and/or SSP5 – 8.5 should be discounted because they confuse decision makers whom Hausfather and Peters (2020) indicate should be focusing instead on middle of the road projections such as RCP 4.5, or SSP2 – 4.5; are in my opinion doing a public disservice and are engaging in politics instead of science for reasons including:

1. Calling radiative forcing (RF) scenarios like SSP5 – 8.5 Business as Usual, BAU, scenarios is actually a call for more action to fight climate change, not less.  Furthermore, in my opinion those who say that calling SSP5 – 8.5 a BAU scenario is disheartening, are actually trying to absolve themselves of accountability for facing our true situation.

2. Peters has recently tweeted essentially that reactions against Hausfather and Peters (2020) recommendations is much to do about nothing, because for the next several decades it is difficult to distinguish between model projections using any of the RCP (or SSP) scenarios; however, the attached image illustrates that such a statement is a red herring because each new family of RF scenarios adopt a new (& higher) baseline; while if one goes back to the SRES family of RF scenarios one can see more clearly that we have consistently been following the higher (BAU) scenarios (such as SRES A1F1 or A2), and we are a long ways away from the middle of the road scenario (such as SRES A1).

3. Also, to repeat prior points that I have made on this topic: a) many CMIP6 models are projecting high values of ECS; b) CMIP6 models are discounting the RF input from future ice-climate feedbacks; c) Climate impacts on the global socio-economic system are likely higher than indicated by AR5, thus if our collective socio-economic system were to collapse circa 2050, the associated abrupt drop in negative feedback from anthropogenic aerosol emissions would lead to an abrupt increase in net radiative forcing.

[AbruptSLR]

While this calving event is covered in much more detail in the PIG has Calved thread, I note here that on February 9, 2020 the Pine Island Ice Shelf, PIIS, sustained a major calving event as shown in the attached image; which produced a Malta size loss of ice for the PIIS.  Thus the new calving face is much further upstream than considered by consensus climate science in CMIP6.

[AbruptSLR]

The linked reference indicates that subglacial sediment discharge should increase dramatically this century, with continued global warming.  This will likely result in significant increases in bed erosion beneath glaciers; which is not good news for the stability of key marine glaciers in West Antarctica like PIG and Thwaites Glacier:

Ian Delaney et al. (07 February 2020), "Increased subglacial sediment discharge in a warming climate: consideration of ice dynamics, glacial erosion and fluvial sediment transport", Geophysical Research Letters,
https://doi.org/10.1029/2019GL085672

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL085672

Abstract
We evaluate changes to subglacial sediment discharge during glacier retreat by considering ice dynamics, bedrock erosion and sediment transport processes. Coupling these components together within a single framework, we simulate synthetic alpine glaciers experiencing accelerated glacier melt for 100 years. We find that sediment discharge increases by about 8 times the steady glacier values by the end of the simulation. The enhanced sediment discharge persists through peak water discharge and despite annual bedrock erosion volumes decreasing by approximately 30% from the initial value. The greater sediment discharge results from increased melt at the glaciers’ higher region, where transport was limited prior to glacier retreat. These findings suggest that large increases in sediment discharge may occur as glaciers retreat, and the magnitude of the sediment discharge increase primarily depends on the quantity of sediment stored subglacially.

Plain Language Summary
Changes to sediment discharge from glaciers can dramatically impact downstream communities and ecosystems. We account for two primary processes that largely control to sediment discharge from glaciers: (1) bedrock erosion which creates sediment below the glacier, and (2) the ability of meltwater below the glacier to carry this sediment. To understand the potential changes in sediment discharge as glaciers retreat, we link numerical models of both processes and run them in a scenario that complies with ongoing climate warming. In the scenario, we find that sediment discharge increases dramatically, despite smaller quantities of sediment being produced by bedrock erosion. This is because more meltwater higher on the glaciers increases sediment transport there. Results here suggest that future of subglacial sediment discharge depends on the amount of sediment that already exists below glaciers and large increases in subglacial sediment discharge are possible.

[sidd]

Re: significant increases in bed erosion

?

 the abstract states: " annual bedrock erosion volumes decreasing by approximately 30% from the initial value"

sidd

[Tor Bejnar]

Yes, Sidd, less 'new' cutting of bedrock into sediment, and much more 'old' sediment mobilized because there is much more water flowing.

An analogy:  (what is now) western Arizona was once pretty flat and a river (the antecedent of the Colorado R.) meandered over it, depositing sediment here and picking it up there, as meandering rivers do, with a net increase of sediment being deposited [vaguely what happens under ice fields and advancing glaciers - more sediment is 'created' than gets to the ends of exiting glaciers].  Then there was 'slow' uplift in 'Arizona' and the down-river end started carrying much more sediment than was brought in, and therefore started cutting what is now the Grand Canyon [vaguely what happens under retreating glaciers - more sediment is carried downstream than gets created by the moving ice as there is much more water flowing].  Now, while the Colorado River incised the ancient meanders deep into the pre-existing rock, water flowing under retreating glaciers is mostly just sending downstream (rapidly) what was pulverized by the ice and what was slowly being carried sea-ward by the ice.  Also, the time-scale difference is great (thousands to millions of years vs. decades).

[AbruptSLR]

Yes, Sidd, less 'new' cutting of bedrock into sediment, and much more 'old' sediment mobilized because there is much more water flowing.

An analogy:  (what is now) western Arizona was once pretty flat and a river (the antecedent of the Colorado R.) meandered over it, depositing sediment here and picking it up there, as meandering rivers do, with a net increase of sediment being deposited [vaguely what happens under ice fields and advancing glaciers - more sediment is 'created' than gets to the ends of exiting glaciers].  Then there was 'slow' uplift in 'Arizona' and the down-river end started carrying much more sediment than was brought in, and therefore started cutting what is now the Grand Canyon [vaguely what happens under retreating glaciers - more sediment is carried downstream than gets created by the moving ice as there is much more water flowing].  Now, while the Colorado River incised the ancient meanders deep into the pre-existing rock, water flowing under retreating glaciers is mostly just sending downstream (rapidly) what was pulverized by the ice and what was slowly being carried sea-ward by the ice.  Also, the time-scale difference is great (thousands to millions of years vs. decades).

I concur

[AbruptSLR]

The linked article discusses nine potential climate change 'tipping points'.  While this article provides useful information, I do not necessarily agree with its characterization of the associated climate risks, and I note that it does not discusses risks associated with such key 'tipping point' mechanisms as those associated with the Beaufort Gyre, or the abrupt reduction in negative feedback from low altitude clouds identified in several CMIP6 model projections:

Title: "Explainer: Nine ‘tipping points’ that could be triggered by climate change"

https://www.carbonbrief.org/explainer-nine-tipping-points-that-could-be-triggered-by-climate-change

Extract: "In this article, Carbon Brief explores nine key tipping points across the Earth system, from collapsing ice sheets and thawing permafrost, to shifting monsoons and forest dieback.
And, over the coming week, Carbon Brief will be publishing guest articles from experts in four of the tipping points covered here.

Tipping towers
Irreversible change?
•   1. Shutdown of the Atlantic Meridional Overturning Circulation
•   2. West Antarctic ice sheet disintegration
•   3. Amazon rainforest dieback
•   4. West African monsoon shift
•   5. Permafrost and methane hydrates
•   6. Coral reef die-off
•   7. Indian monsoon shift
•   8. Greenland ice sheet disintegration
•   9. Boreal forest shift
•   Other tipping points"

[AbruptSLR]

While this calving event is covered in much more detail in the PIG has Calved thread, I note here that on February 9, 2020 the Pine Island Ice Shelf, PIIS, sustained a major calving event as shown in the attached image; which produced a Malta size loss of ice for the PIIS.  Thus the new calving face is much further upstream than considered by consensus climate science in CMIP6.

With a hat-tip to blumenkraft for the attached image (taken on Feb. 10, 2020), I make the following observations about the recent calving event:

1. The ice shelf for the SW Tributary Glacier also sustained a calving event.
2. The icebergs in the downstream southern shear margin for the PIIS appear to be free to float into the open ocean; which, would leave adjoining portion of the PIIS susceptible to accelerated future calving events (possibly initiated a MR1 and/or MR2); which are not considered in any of the CMIP6 model projections.

Edit, see also the second image (with a hat-tip to paolo) showing the iceberg mélange on the southwest shear margin for PIIS.

[AbruptSLR]

The linked presentation indicates that advanced CMIP6 model projections (like from HadGEM3), to an excellent job of reproducing the CERES observations including the SST pattern changes.  As these advances CMIP6 models typically project relatively high values of ECS this century, this provides support (based on recorded observations) for the idea that ECS is actively increasing with continued global warming:

Title: "Using CERES Observations to Assess CMIP6 Model Simulations of Changes in Earth's Radiation Budget During and After the Global Warming 'Hiatus'" by Norman Loeb et al (2019)

https://ceres.larc.nasa.gov/documents/STM/2019-10/8-THU_1150am_Loeb_Hiatus_Presentation.pdf

Extract: "Conclusions
•   ERB observations provide key data for testing model representation of both mean climatology and climate system response to SST pattern changes.
•   Model biases in climatology and biases in response to SST pattern changes are not correlated in Sc region over eastern Pacific.
•   GCM-AMIP simulation show decrease in reflected SW TOA flux in marine Sc regions following hiatus, but underestimate eh magnitude compared to observations.
o    Some models do excellent job of reproducing observed patterns in ERB response to SST pattern changes (e.g., HadGEM3).
•   Ts and EIS variations in marine Sc regions explain most of the variability in SW TOA flux, with the Ts contribution dominating."

[wdmn]

2. The icebergs in the downstream southern shear margin for the PIIS appear to be free to float into the open ocean; which, would leave adjoining portion of the PIIS susceptible to accelerated future calving events (possibly initiated a MR1 and/or MR2); which are not considered in any of the CMIP6 model projections.

ASLR,

Your probably already have, but could you post a link to where we might look at the CMIP6 model projections as they relate to the PIIS?

Thank you!

[AbruptSLR]

2. The icebergs in the downstream southern shear margin for the PIIS appear to be free to float into the open ocean; which, would leave adjoining portion of the PIIS susceptible to accelerated future calving events (possibly initiated a MR1 and/or MR2); which are not considered in any of the CMIP6 model projections.

ASLR,

Your probably already have, but could you post a link to where we might look at the CMIP6 model projections as they relate to the PIIS?

Thank you!

wdmn,

Noting that ISMIP6 is associated with CMIP6, see the first linked reference and the second liked website for updates on this matter:

Seroussi et al. (2019), "initMIP-Antarctica: an ice sheet model initialization experiment of ISMIP6", The Cryosphere, 13, 1441-1471; https://doi.org/10.5194/tc-13-1441-2019

https://www.the-cryosphere.net/13/1441/2019/tc-13-1441-2019.pdf
https://www.the-cryosphere.net/13/1441/2019/

Abstract: "Ice sheet numerical modeling is an important tool to estimate the dynamic contribution of the Antarctic ice sheet to sea level rise over the coming centuries. The influence of initial conditions on ice sheet model simulations, however, is still unclear. To better understand this influence, an initial state intercomparison exercise (initMIP) has been developed to compare, evaluate, and improve initialization procedures and estimate their impact on century-scale simulations. initMIP is the first set of experiments of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity focusing on the Greenland and Antarctic ice sheets. Following initMIP-Greenland, initMIP-Antarctica has been designed to explore uncertainties associated with model initialization and spin-up and to evaluate the impact of changes in external forcings. Starting from the state of the Antarctic ice sheet at the end of the initialization procedure, three forward experiments are each run for 100 years: a control run, a run with a surface mass balance anomaly, and a run with a basal melting anomaly beneath floating ice. This study presents the results of initMIP-Antarctica from 25 simulations performed by 16 international modeling groups. The submitted results use different initial conditions and initialization methods, as well as ice flow model parameters and reference external forcings. We find a good agreement among model responses to the surface mass balance anomaly but large variations in responses to the basal melting anomaly. These variations can be attributed to differences in the extent of ice shelves and their upstream tributaries, the numerical treatment of grounding line, and the initial ocean conditions applied, suggesting that ongoing efforts to better represent ice shelves in continental-scale models should continue."

See also, and the attached image:

http://www.climate-cryosphere.org/wiki/index.php?title=ISMIP6-Projections-Antarctica

Extract: "This page describes the experimental protocol for the ISMIP6 projections that target the upcoming IPCC AR6 assessment. Due to the delay in CMIP6 climate simulations, the initial set of ISMIP6 simulations are based on CMIP5 projections. As CMIP6 model outputs become available, ISMIP6 will include simulations based on these new models.
…
Antarctic ice shelf fracture
Surface melting can trigger ice shelf collapse (for example, the Larsen B ice shelf in the Antarctic Peninsula). This mechanism is separate from cliff-collapse, but is a precursor to cliff-collapse. Although the mechanisms for Larsen B-style ice shelf collapse are still poorly understood, ISMIP6 provides dataset for ice shelf collapse in the form of a time dependent mask (Fig 4). These datasets were derived from CMIP5 near surface air temperature (tas) following the method described in Trusel et al. (2015), which results in annual surface melt. For ISMIP6, Luke Trussel prepared the bias corrected annual surface melt, which were used to generate the masks. Ice shelves are assumed to collapse following a 10 year period with annual surface melt above 725 mm (Trusel et al., 2015). Some experiments require to model ice shelf collapse and the ISMIP6 masks provided should be used in this case. For the other experiments, ice shelf collapse should not be included.

Models are free to decide on the appropriate method to simulate tributary glaciers' behavior following the collapse of ice shelves. As the masks were derived from observations, the observed ice shelf may not always corresponds to an ice shelf in the ISM. In the event that the ice shelf collapse mask corresponds to a region which an ISM considers to be grounded (ice sheet), the collapse should not be imposed. Similarly, in the event that applying the mask results in "iceberg" or regions of floating ice shelf that are now detached from the ice shelf, these floating part of the ice should be removed as well.

The datasets can be obtained from: sftp://transfer.ccr.buffalo.edu/projects/grid/ghub/ISMIP6/Projections/AIS/Ice_Shelf_Fracture/"

[AbruptSLR]

The retreat of Antarctic ice shelf calving front assumed by CMIP6 was based largely on ice shelf performance observed during the 1990s; however, the linked article confirms that the rate of calving from the Pine Island, and Thwaites, ice shelf/tongue in the past decade has been two to four time faster than that observed in the 1990s.  Consequently, these ice shelves are retreating faster than new ice is feed into them.  It looks likely at best we will need to wait until CMIP7 (or CMIP8) before this type of dynamic behavior is officially recognized in either AR7 or AR8:

Title: "One of Antarctica's fastest-shrinking glaciers just lost an iceberg twice the size of Washington, D.C."

https://www.livescience.com/pine-island-glacier-calving-retreat.html

Extract: "On its own, the recent calving event is not entirely surprising or particularly threatening to global sea levels; calving is a normal part of life for ice formations with sections that float on the water, according to NASA's Earth Observatory. Because ice at the edge of the glacier was already floating, this ice will not directly contribute to sea level rise when it inevitably melts.

However, over the past two decades, calving events have been occurring much more frequently at Pine Island Glacier and the neighboring Thwaites Glacier (also known as the "Doomsday Glacier") as the surrounding ocean warms due to global warming. While large calving events used to occur at Pine Island Glacier every four to six years, they've now become a near-annual occurrence, according to NASA. In the last decade, huge chunks of the glacier calved away in 2011, 2013, 2015, 2017, 2018 and now in 2020.

As a result, the Pine Island and Thwaites ice shelves are retreating inland faster than new ice can form. Scientists worry that this persistent retreat could be a sign that a runaway melting cycle is in effect: As comparatively warm sea water laps at the newly exposed edges of an ice shelf, melting accelerates, the ice shelf stretches and thins, and further calving becomes ever more likely."

[AbruptSLR]

While the linked article offers some consensus science discussions associated with the risk that the AMOC could shut down this century (which it suggests is very unlikely); it fails to discuss risks associate with possible freshwater hosing events associated with either the Beaufort Gyre or the WAIS, in the coming decades.  Thus, the actual risks are likely higher than indicated by this article.  Furthermore, I note that if the MOC were to slow abruptly in the coming decades the risk that the NH atmosphere might flip into an equable pattern, this century, would be markedly increased:

Title: "Guest post: Could the Atlantic Overturning Circulation ‘shut down’?"

https://www.carbonbrief.org/guest-post-could-the-atlantic-overturning-circulation-shut-down

Extract: "The latest research suggests that AMOC is very likely to weaken this century, but a collapse is very unlikely. However, scientists are some way from being able to define exactly how much warming might push AMOC past a tipping point.
…
Climate-model projections of global warming this century consistently point to a weakening of the AMOC. The most recent assessments of the Intergovernmental Panel on Climate Change (IPCC) – the fifth assessment report (AR5) and special report on oceans and cryosphere in a changing climate (SROCC) – both conclude that the AMOC is “very likely” to weaken over the 21st century.
…
If the freshwater input to the Atlantic were strong enough – from rapid melting of the Greenland ice sheet, for example – the blue dot would move to the right in the figure. According to Stommel’s model, at some point the strong AMOC state (red) becomes unsustainable and the AMOC collapses to the “off” state (blue). Then, even if the driving climate change were later reversed (the blue dot moving back to the left on the figure), the AMOC would stay on the blue curve and would not switch back on again until the climate had overshot the present day conditions in the opposite direction. This phenomenon is known as “hysteresis”.
…
While the fundamental mechanism that destabilises the AMOC in Stommel’s original model appears to be important in climate models, there are other processes that are trying to stabilise the AMOC. Many of these processes are difficult to model quantitatively, especially with the limited resolution that is possible with current computing power. So our AMOC projections will continue to be subject to quite some uncertainty for some time to come.

Taking all the evidence into account, the IPCC’s AR5 and SROCC concluded that an AMOC collapse before 2100 was “very unlikely” (pdf). However, the impacts of passing an AMOC tipping point would be huge, so it is best viewed as a “low probability, high impact” scenario."