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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3350 on: June 18, 2020, 07:48:45 PM »
The linked reference (& associated linked article) large anomalies in the boundary of the Earth core-mantle.  To me this indicates that if sea level were to rise 3, or more, meters this century that such anomalies could trigger unexpected future responses from the Earth, possibly including a relatively rapid flip of the Earth's magnetic poles:

D. Kim et al. (12 Jun 2020), "Sequencing seismograms: A panoptic view of scattering in the core-mantle boundary region", Science, Vol. 368, Issue 6496, pp. 1223-1228
DOI: 10.1126/science.aba8972

https://science.sciencemag.org/content/368/6496/1223

Abstract
Scattering of seismic waves can reveal subsurface structures but usually in a piecemeal way focused on specific target areas. We used a manifold learning algorithm called “the Sequencer” to simultaneously analyze thousands of seismograms of waves diffracting along the core-mantle boundary and obtain a panoptic view of scattering across the Pacific region. In nearly half of the diffracting waveforms, we detected seismic waves scattered by three-dimensional structures near the core-mantle boundary. The prevalence of these scattered arrivals shows that the region hosts pervasive lateral heterogeneity. Our analysis revealed loud signals due to a plume root beneath Hawaii and a previously unrecognized ultralow-velocity zone beneath the Marquesas Islands. These observations illustrate how approaches flexible enough to detect robust patterns with little to no user supervision can reveal distinctive insights into the deep Earth.

See also:
Title: "The monstrous 'blobs' near Earth's core may be even bigger than we thought"

https://www.livescience.com/core-mantle-ulvz-blobs-enormous.html

Extract: "Deep within Earth, where the solid mantle meets the molten outer core, strange continent-size blobs of hot rock jut out for hundreds of miles in every direction. These underground mountains go by many names: "thermo-chemical piles," "large low-shear velocity provinces" (LLSVPs), or sometimes just "the blobs."

Geologists don't know much about where these blobs came from or what they are, but they do know that they're gargantuan. The two biggest blobs, which sit deep below the Pacific Ocean and Africa, account for nearly 10% of the entire mantle's mass, one 2016 study found — and, if they sat on Earth's surface, the duo would each extend about 100 times higher than Mount Everest. However, new research suggests, even those lofty analogies may be underestimating just how big the blobs really are.

"The structures we located are … thousands of kilometers across in scale," lead study author Doyeon Kim, a postdoctoral fellow at the University of Maryland, told Live Science in an email. According to Kim, that's an order of magnitude larger than typical features found along the blob's edge."


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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3351 on: June 18, 2020, 10:59:40 PM »
Wait. Allen et al. discuss _peak_ warming from a given amount of C injection, here specifically a trillion tons. This uses ECS to get the ultimate warming. Since that article was published in 2009, it is unfair to want them to have used CMIP6 values.

TCRE gives you the warming _during_ the emission process, ECS will give you the ultimate attained maximum temperature.

I do not see a reference to Hausfather using anything but ECS to calculate peak warming for given C injection. Stating that " he can easily use TCRE"  does not mean he did any such thing in a calculation for peak warming from a given amount of carbon injection. Please point me to the specific publication by Hausfather where he repeats the Allen calculation using TCRE. The way to do that is to integrate TCRE through the entire emission pathway but that will just give you ECS all over again, so i do not see the point in doing so, and i do not believe Hausfather did.

Now it may be that Hausfather is calculating something else other than peak warming for a given injection of C. Perhaps he is calculating a temperature evolution for for specific emission pathway that injects C and then withdraws it.  But again i see no citation to the literature. If someone has such a citation, I would appreciate.

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wili

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3352 on: June 19, 2020, 01:19:51 PM »
Tiny sand grains trigger massive glacial surges
Quote
"It's within the realm of possibility that we could get 1 to 3 meters of sea-level rise from West Antarctica within our lifetimes," Minchew says. This type of shearing mechanism in glacial surges could play a major role in determining the rates of sea-level rise you'd get from West Antarctica."

https://phys.org/news/2020-06-tiny-sand-grains-trigger-massive.html
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Lennart van der Linde

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3353 on: June 19, 2020, 01:42:53 PM »
Thnx, Wili.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3354 on: June 19, 2020, 04:32:22 PM »
Wait. Allen et al. discuss _peak_ warming from a given amount of C injection, here specifically a trillion tons. This uses ECS to get the ultimate warming. Since that article was published in 2009, it is unfair to want them to have used CMIP6 values.

TCRE gives you the warming _during_ the emission process, ECS will give you the ultimate attained maximum temperature.

I do not see a reference to Hausfather using anything but ECS to calculate peak warming for given C injection. Stating that " he can easily use TCRE"  does not mean he did any such thing in a calculation for peak warming from a given amount of carbon injection. Please point me to the specific publication by Hausfather where he repeats the Allen calculation using TCRE. The way to do that is to integrate TCRE through the entire emission pathway but that will just give you ECS all over again, so i do not see the point in doing so, and i do not believe Hausfather did.

Now it may be that Hausfather is calculating something else other than peak warming for a given injection of C. Perhaps he is calculating a temperature evolution for for specific emission pathway that injects C and then withdraws it.  But again i see no citation to the literature. If someone has such a citation, I would appreciate.

sidd

sidd,

First, you appear to misunderstand my posts, to the point that you are apparently putting words into my mouth (which is not appreciated).  My posts were about what Hausfather was doing with Allen et al. (2009) findings to imply that climate sensitivity is essentially linear (and thus essentially reversible).  So I make no points about Allen et al. (2009) but only about Hausfather.

Second, I previously provided the following about Hausfather's use of TCRE to project changes in GMSTA:

Title: "A 3C World Is Now “Business as Usual”"

https://thebreakthrough.org/issues/energy/3c-world

Extract: "Warming in the the two IEA scenarios is calculated based on the difference between cumulative fossil fuel and industry emissions in each scenario and that in the SSP2-4.5 scenario. These cumulative emissions differences are converted into additional warming based on the IPCC SR15 TCRE value of 1.65C per 1000 PgC, with a range from 0.8C to 2.5C / 1000 PgC reflecting uncertainties in climate sensitivity. Finally, this additional warming is added to RCP4.5 warming projections, with the average, low, and high TCRE-based additional warming values added to the average, low, and high RCP4.5 warming values, respectively."

Also, see the attached image from "A 3C World Is Now “Business as Usual" where Hausfather calculated GMSTA through 2100 using TCRE for two IEA scenarios; which is all that I care about for this discussion.

My point is that as a consensus climate scientist Hausfather frequently errs on the side of least drama by using linear feedback mechanisms, and ignoring uncertainty about other feedback mechanisms including nonlinear carbon-cycle feedbacks and ice-climate feedback mechanisms.

If you want to play with Hausfather's TCRE calculation procedures you can find them at the link below:

https://github.com/hausfath/SimMod

Edit: To be clear, Hausfather is very familiar with CMIP6 and yet in 2020 he was presenting Allen et al. (2009)'s findings as proof that climate sensitivity is essentially linear this century and thus so reversible that we can suck CO2 out of the atmosphere in the future to get back to safe conditions (which Hausfather suggests would be 2000 levels).
« Last Edit: June 19, 2020, 05:48:27 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3355 on: June 19, 2020, 06:04:16 PM »
The linked article indicates that deforestation in the Amazon in 2020 is on track to be at least as bad as in 2019 if not worse:

Title: "Scientists fear deforestation, fires and Covid-19 could create a 'perfect storm' in the Amazon"

https://www.cnn.com/2020/06/19/americas/amazon-fires-deforestation-rise-covid/index.html

Extract: "New data shows that fires in the Brazilian Amazon are on track to be just as bad as last year, if not worse, with an estimated 150,000 hectares of land deforested so far in 2020 at risk."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3356 on: June 19, 2020, 08:37:46 PM »
The linked reference indicates that it is increasingly unlikely that forests will be able to suck significant quantities of excess CO2 from the atmosphere:

William R. L. Anderegg et al. (19 Jun 2020), "Climate-driven risks to the climate mitigation potential of forests", Science, Vol. 368, Issue 6497, eaaz7005, DOI: 10.1126/science.aaz7005

https://science.sciencemag.org/content/368/6497/eaaz7005.full

"Risks to mitigation potential of forests
Much recent attention has focused on the potential of trees and forests to mitigate ongoing climate change by acting as sinks for carbon. Anderegg et al. review the growing evidence that forests' climate mitigation potential is increasingly at risk from a range of adversities that limit forest growth and health. These include physical factors such as drought and fire and biotic factors, including the depredations of insect herbivores and fungal pathogens. Full assessment and quantification of these risks, which themselves are influenced by climate, is key to achieving science-based policy outcomes."

Structured Abstract
BACKGROUND
Forests have considerable potential to help mitigate human-caused climate change and provide society with a broad range of cobenefits. Local, national, and international efforts have developed policies and economic incentives to protect and enhance forest carbon sinks—ranging from the Bonn Challenge to restore deforested areas to the development of forest carbon offset projects around the world. However, these policies do not always account for important ecological and climate-related risks and limits to forest stability (i.e., permanence). Widespread climate-induced forest die-off has been observed in forests globally and creates a dangerous carbon cycle feedback, both by releasing large amounts of carbon stored in forest ecosystems to the atmosphere and by reducing the size of the future forest carbon sink. Climate-driven risks may fundamentally compromise forest carbon stocks and sinks in the 21st century. Understanding and quantifying climate-driven risks to forest stability are crucial components needed to forecast the integrity of forest carbon sinks and the extent to which they can contribute toward the Paris Agreement goal to limit warming well below 2°C. Thus, rigorous scientific assessment of the risks and limitations to widespread deployment of forests as natural climate solutions is urgently needed.

ADVANCES
Many forest-based natural climate solutions do not yet rely on the best available scientific information and ecological tools to assess the risks to forest stability from climate-driven forest dieback caused by fire, drought, biotic agents, and other disturbances. Crucially, many of these permanence risks are projected to increase in the 21st century because of climate change, and thus estimates based on historical data will underestimate the true risks that forests face. Forest climate policy needs to fully account for the permanence risks because they could fundamentally undermine the effectiveness of forest-based climate solutions.

Here, we synthesize current scientific understanding of the climate-driven risks to forests and highlight key issues for maximizing the effectiveness of forests as natural climate solutions. We lay out a roadmap for quantifying current and forecasting future risks to forest stability using recent advances in vegetation physiology, disturbance ecology, mechanistic vegetation modeling, large-scale ecological observation networks, and remote sensing. Finally, we review current efforts to use forests as natural climate solutions and discuss how these programs and policies presently consider and could more fully embrace physiological, climatic, and permanence uncertainty about the future of forest carbon stores and the terrestrial carbon sink.

OUTLOOK
The scientific community agrees that forests can contribute to global efforts to mitigate human-caused climate change. The community also recognizes that using forests as natural climate solutions must not distract from rapid reductions in emissions from fossil fuel combustion. Furthermore, responsibly using forests as natural climate solutions requires rigorous quantification of risks to forest stability, forests’ carbon storage potential, cobenefits for species conservation and ecosystem services, and full climate feedbacks from albedo and other effects. Combining long-term satellite records with forest plot data can provide rigorous, spatially explicit estimates of climate change–driven stresses and disturbances that decrease productivity and increase mortality. Current vegetation models also hold substantial promise to quantify forest risks and inform forest management and policies, which currently rely predominantly on historical data.

A more-holistic understanding and quantification of risks to forest stability will help policy-makers effectively use forests as natural climate solutions. Scientific advances have increased our ability to characterize risks associated with a number of biotic and abiotic factors, including risks associated with fire, drought, and biotic agent outbreaks. While the models that are used to predict disturbance risks of these types represent the cutting edge in ecology and Earth system science to date, relatively little infrastructure and few tools have been developed to interface between scientists and foresters, land managers, and policy-makers to ensure that science-based risks and opportunities are fully accounted for in policy and management contexts. To enable effective policy and management decisions, these tools must be openly accessible, transparent, modular, applicable across scales, and usable by a wide range of stakeholders. Strengthening this science-policy link is a critical next step in moving forward with leveraging forests in climate change mitigation efforts.

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3357 on: June 19, 2020, 09:25:33 PM »
My apologies if i misunderstood you on Hausfather and thanks for the github link.

sidd
 

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3358 on: June 20, 2020, 06:37:56 PM »
Corinne Le Quere makes a valid point that until there is a major change in our global socio-economic energy infrastructure, fossil fuel emission are likely to come back (or exceed) their pre-COVID-19 levels very quickly:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Hefaistos

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3359 on: June 21, 2020, 08:43:12 AM »
...
I believe that such evidence indicates that in coming decades we can expect more ice-climate feedback mechanisms than assumed in any CMIP6 model (including in E3SM1).

Ad hoc calvings is a natural phenomenon. It's also snowing a lot over Greenland and the surface mass balance goes up with maybe 600 gigatonnes each winter season.
Espen estimates this calving to be around 200 sq.km. How many tonnes might such a berg be? 1 gigaton? 10 gigatonnes? In any case, it's a rather negligible event in the bigger picture.

Such regular calvings are just part of the natural seasonal variations and no evidence of any drama in terms of "more ice-climate feedback mechanisms than assumed in any CMIP6 model (including in E3SM1)"
« Last Edit: June 21, 2020, 09:02:58 AM by Hefaistos »

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3360 on: June 21, 2020, 08:42:31 PM »
...
Such regular calvings are just part of the natural seasonal variations and no evidence of any drama in terms of "more ice-climate feedback mechanisms than assumed in any CMIP6 model (including in E3SM1)"

Hefaistos,

I have made well over a thousand posts specifically providing evidence that there is '… drama in terms of "more ice-climate feedback mechanisms than assumed in any CMIP6 model (including in E3SM1)"; however, I acknowledge that the topic of potential abrupt climate change this century is complex & thus potentially confusing to many readers, such as by your posts apparent effort to tie Greenland Surface Mass Balance, SMB, to ice-climate feedback mechanisms; whereas in reality Greenland SMB is more related to sea level rise than to ice-climate feedback mechanism; while ice-climate feedback is more related to surface ice melting together with ice calving.

Therefore, while readers potentially confused by your post could scroll back through this thread (and/or my posts on this topic in other threads) to find evidence of more ice-climate feedback mechanism than those assumed in E3SM1; I will provide a few simple lines of such evidence in this post. 

I begin with the first linked Wikipedia article on the North Atlantic Cold Blob (see the first attached image) that indicates that Mann and Rahmstorf were among to the first to suggest that this North Atlantic Cold Blob is likely created by global warming-induced meltwater primarily from Greenland, and that this blob is contributing to the observed slowdown of the AMOC (MOC).

Title: "Cold blob (North Atlantic)"

https://en.wikipedia.org/wiki/Cold_blob_(North_Atlantic)

Extract: "The cold blob in the North Atlantic (also called the North Atlantic warming hole) describes a cold temperature anomaly of ocean surface waters, affecting the Atlantic Meridional Overturning Circulation (AMOC) which is part of the thermohaline circulation, possibly related to global warming-induced melting of the Greenland ice sheet.

Climate scientists Michael Mann of Penn State and Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research suggested that the observed cold pattern during years of temperature records is a sign that the Atlantic Ocean's Meridional overturning circulation (AMOC) may be weakening.

Next, I provide the second link to a Wikipedia article on abrupt climate change that indicates that:

"… a variety of tipping elements could reach their critical point within this century under anthropogenic climate change".

It has been postulated that teleconnections, oceanic and atmospheric processes, on different timescales, connect both hemispheres during abrupt climate change.
"

Title: "Abrupt climate change"

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

Extract: "Possible tipping elements in the climate system include regional effects of global warming, some of which had abrupt onset and may therefore be regarded as abrupt climate change. Scientists have stated, "Our synthesis of present knowledge suggests that a variety of tipping elements could reach their critical point within this century under anthropogenic climate change".

It has been postulated that teleconnections, oceanic and atmospheric processes, on different timescales, connect both hemispheres during abrupt climate change."

In this regard, I provide the second attached image that illustrates one of many teleconnection be both hemispheres (related to the bipolar seesaw mechanism), that shows how an acceleration of the Westerly winds over the Southern Ocean (e.g. due to the Antarctic ozone hole and/or to increased atmospheric GHG concentrations) has increased Agulhas Leakage that is also working to cool the North Atlantic; which is also slowing the AMOC (just like the North Atlantic Cold Blob associated with Greenland meltwater).

Next, I provide the third attached image that shows how anthropogenically-induced Antarctic meltwater is currently inhibiting the cooling of Antarctic Circumpolar Deep Water (CDW); which, provides yet another ice-climate feedback mechanism to increase the future temperature of the CDW beneath Antarctic ice shelves and grounding lines for marine glaciers that then lead to a feedback loop for more ice melting and more warming of the CDW.  This image projects a significant amount of warming of the CDW between 2040 and 2050 at water depth that could contribute to potential future MICI-types of failures for key West Antarctic marine glaciers like the PIG and the Thwaites Glacier.

Next the following linked reference's finding that part of the E3SM version 1 projected high value of TCR (see the fourth image)  is due to a projected slowing of the AMOC; then this may well be because E3SM version 1 did a better job of evaluating the influence of freshwater hosing from glacier meltwater; then this implies that ice-climate feedbacks may likely have a much higher impact on increasing climate sensitivity than consensus climate science is currently acknowledging.

Aixue Hu et al. (17 April 2020), "Role of AMOC in transient climate response to greenhouse gas forcing in two coupled models", Journal of Climate, https://doi.org/10.1175/JCLI-D-19-1027.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-19-1027.1?af=R


Abstract
As the greenhouse gas concentrations increase, a warmer climate is expected. However, numerous internal climate processes can modulate the primary radiative warming response of the climate system to rising greenhouse gas forcing. Here the particular internal climate process that we focus on is the Atlantic Meridional Overturning Circulation (AMOC) – an important global scale feature of ocean circulation that serves to transport heat and other scalars, and we address the question of how the mean strength of AMOC can modulate the transient climate response. While the Community Earth System Model version 2 (CESM2) and the Energy Exascale Earth System Model version 1 (E3SM1) have very similar equilibrium/effective climate sensitivity, our analysis suggests that a weaker AMOC contributes in part to the higher transient climate response to a rising greenhouse gas forcing seen in E3SM1 by permitting a faster warming of the upper ocean and a concomitant slower warming of the subsurface ocean. Likewise the stronger AMOC in CESM2 by permitting a slower warming of the upper ocean leads in part to a smaller transient climate response. Thus, while the mean strength of AMOC does not affect the equilibrium/effective climate sensitivity, it is likely to play an important role in determining the transient climate response on the centennial timescale.


Finally, I note that the following linked reference, and associated linked article, concludes that Antarctic glacial meltwater is a 'climate response function' (CRF) that improves climate model projections (as currently consensus climate models ignore this CRF).  Furthermore, readers should be aware that James Hansen has previously identified this CRF as a positive ice-climate feedback mechanism that accelerates climate change:

“Antarctic Glacial Melt as a Driver of Recent Southern Ocean Climate Trends” by Craig D. Rye, John Marshall, Maxwell Kelley, Gary Russell, Larissa S. Nazarenko, Yavor Kostov, Gavin A. Schmidt and James Hansen, 9 April 2020, Geophysical Research Letters; DOI: 10.1029/2019GL086892

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086892

Abstract
Recent trends in Southern Ocean (SO) climate—of surface cooling, freshening, and sea ice expansion—are not captured in historical climate simulations. Here we demonstrate that the addition of a plausible increase in Antarctic meltwater to a coupled climate model can produce a closer match to a wide range of climate trends. We use an ensemble of simulations of the Goddard Institute for Space Studies Earth system model to compute “climate response functions” (CRFs) for the addition of meltwater. These imply a cooling and freshening of the SO, an expansion of sea ice, and an increase in steric height, all consistent with observations since 1992. The CRF framework allows one to compare the efficacy of Antarctic meltwater as a driver of SO climate trends, relative to greenhouse gas and surface wind forcing. The meltwater CRFs presented here strongly suggest that interactive Antarctic ice melt should be included in climate models.

Plain Language Summary
Climate models do not capture recent Southern Ocean (SO) climate trends of surface cooling, freshening, and sea ice expansion. Here we demonstrate that including a realistic increase in Antarctic meltwater can improve a model's representation of SO trends. We use an ensemble of simulations of the Goddard Institute for Space Studies Earth system model. Model results suggest that Antarctic meltwater drives a cooling and freshening of the SO and an expansion of winter sea ice, all consistent with observations. Results suggest that a better representation of Antarctic ice melt should be included in climate models.


See also:

Title: "Melting Glaciers Cool the Southern Ocean – Might Explain the Recent Antarctic Cooling and Sea Ice Expansion"

https://scitechdaily.com/melting-glaciers-cool-the-southern-ocean-might-explain-the-recent-antarctic-cooling-and-sea-ice-expansion/

Extract: "Research suggests glacial melting might explain the recent decadal cooling and sea ice expansion across Antarctica’s Southern Ocean.

Tucked away at the very bottom of the globe surrounding Antarctica, the Southern Ocean has never been easy to study. Its challenging conditions have placed it out of reach to all but the most intrepid explorers. For climate modelers, however, the surface waters of the Southern Ocean provide a different kind of challenge: It doesn’t behave the way they predict it would. “It is colder and fresher than the models expected,” says Craig Rye, a postdoc in the group of Cecil and Ida Green Professor of Oceanography John Marshall within MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).

In recent decades, as the world warms, the Southern Ocean’s surface temperature has cooled, allowing the amount of ice that crystallizes on the surface each winter to grow. This is not what climate models anticipated, and a recent study published in Geophysical Research Letters attempts to disentangle that discrepancy. “This paper is motivated by a disagreement between what should be happening according to simulations and what we observe,” says Rye, the lead author of the paper who is currently working remotely from NASA’s Goddard Institute for Space Studies, or GISS, in New York City.

When this increase in glacial melt was added to the model, it led to sea surface cooling, decreases in salinity, and expansion of sea ice coverage that are consistent with observed trends in the Southern Ocean during the last few decades. Their model results suggest that meltwater may account for the majority of previously misunderstood Southern Ocean cooling.

The model shows that a warming climate may be driving, in a counterintuitive way, more sea ice by increasing the rate of melting of Antarctica’s glaciers. According to Marshall, the paper may solve the disconnect between what was expected and what was observed in the Southern Ocean, and answers the conundrum he and Kostov pointed to in 2016. “The missing process could be glacial melt.”"
« Last Edit: June 21, 2020, 11:28:36 PM by AbruptSLR »
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Tom_Mazanec

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3361 on: June 21, 2020, 11:35:44 PM »
To get back to the OP of this thread, if there is to be multiple meters of SLR this century, this implies an average per year of multiple cm per year, which has not happened. What is the SLR for the last twelve months and how does that compare to the average over the last decade? Do you expect them to go up in a curve? Or do you expect a rise of a cm a month for a decade? How would the change in current SLR happen to get such a huge rise in this century?
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3362 on: June 21, 2020, 11:56:27 PM »
Re: How would the change in current SLR happen to get such a huge rise

MWP1A. Blanchon, 2009.

https://forum.arctic-sea-ice.net/index.php/topic,622.msg119679.html#msg119679

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3363 on: June 22, 2020, 12:24:34 AM »
For those who have no idea what types of freshwater hosing mechanisms that E3SM1 includes, I provide the linked PowerPoint presentation as an example of ice melting beneath two large Antarctic ice shelves (the FRIS and the RIS, see the first image).  The second image shows how glacial meltwater advects from Queen Maud Land to the Weddell Sea where it creates a freshwater cap that allows warm CDW to flow beneath the FRIS as shown in the third image.  The fourth associated image gives a simplistic representation of some of the interactions between the Antarctic Circumpolar Current, various gyres, various ice shelves and various the outputs of Antarctic Bottom Water that feed into the MOC.

The extract focuses on ongoing research efforts including better analyzing the identified ice shelf melt domino effect and the different tipping point mechanisms for the FRIS and the RIS and the impacts of such tipping points on ice-climate feedback in future versions of E3SM.

Title: "Tipping points in melting beneath Antarctic Ice Shelves A Tale of Two Ice Shelves" by Hoffman et al June 11, 2020.

https://e3sm.org/wp-content/uploads/2020/06/200611_M_Hoffman.pdf

Extract:
"Ongoing
• Analysis and paper on ice shelf melt domino effect
• Continue 3DGM preindustrial control
   • Complete Cryo config. model description paper
   • Finally permit historical & future scenario runs for Cryo Campaign!
• Finalize SORRM mesh and configuration
   • Begin v2 production runs for Cryo Campaign
Time-permitting
• Investigate regional & global climate impacts of freshwater flux increase after FRIS tipping point
• Investigate theoretical Ross Ice Shelf melt tipping point
   • Are regional & global climate impacts different than for FRIS tipping point?"
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3364 on: June 22, 2020, 02:41:38 AM »
Tom,

In response to your Reply #3361:

First, regarding the current SLR I like to use Aviso; however, they are currently down for emergency server work but when they are backup you can look as the Jason-2 and/or Jason-3 satellite data at the first link (also, for ease of reference, I attached the first image of Jason-3 SLR data through early 2019 and the second image of all Aviso records from Dec 1992 to August 2019).  Also, you can look at the second linked article that has images like the third attached that shows very clear SLR acceleration at Norfolk, Virginia.

https://www.aviso.altimetry.fr/en/data/products/ocean-indicators-products/mean-sea-level/products-images.html
&
US Sea-Level Report Cards: 2019 Data Adds to Trend in Acceleration
https://phys.org/news/2020-02-sea-level-cards-trend.html

Second, sidd provided a reference to Meltwater Pulse 1A; which is a period that exhibited multiple meters of SLR per century.

Third, to get multiple meters of sea level rise this century would require at least the initiation of an MICI-type of collapse of the WAIS starting no later than 2060 but possibly initiating as early as 2035.  Also, I note that E3SM1 only assumes MISI-type of marine glacier response this century.  If you want to watch a nice video of this topic go back to the original post of this thread and watch prokaryotes' video about the 'Ice Apocalypse' article by Eric Holthaus 2017.

Finally, the fourth image shows that in 2017, NOAA formally recognized the risk (to SLR) that the WAIS might at least partially collapse this century under the right conditions.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3365 on: June 22, 2020, 02:50:08 AM »
Also, in the linked 2019 article, Rob DeConto (a very straight shooter) says that the basic conclusions of the DeConto & Pollard (2016) reference about MICI risks remains unchanged:

Title: "Doomsday Postponed? The Takeaway From the Big New Antarctica Studies"

https://www.motherjones.com/environment/2019/02/doomsday-postponed-the-takeaway-from-the-big-new-antarctica-studies/

Extract: "“We still see a dangerous threat,” Rob DeConto, one of the authors of the 2016 paper, said in an email to Grist. “I don’t really see ice fracture as an optional process that can be excluded from ice sheet models.”

“If the pace of calving we observe in Greenland today someday becomes widespread around the edges of the vastly bigger Antarctic ice sheet, it could cause very fast sea-level rise,” DeConto said. “This was the take home message from our 2016 paper. Based on all the work that has followed, that basic conclusion remains unchanged.”"
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3366 on: June 22, 2020, 10:07:51 AM »
The research in the linked reference confirms that as global anthropogenic GHG emissions are reduced, there will be an interim phase where the ocean carbon sink will slow down and not offset climate change as much as in the past. That extra carbon dioxide will remain in the atmosphere and contribute to additional warming.

Galen A. McKinley et al. (03 June 2020), "External Forcing Explains Recent Decadal Variability of the Ocean Carbon Sink", AGU Advances, https://doi.org/10.1029/2019AV000149

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019AV000149

...

The linked article elaborates on the implications of this reference and indicates that the authors plan to investigate whether the recent drop in CO2 emissions due to COVID-19 has resulted in a less CO2 absorption by the ocean;

Title: "Ocean May Absorb Less CO2 as Man-Made Carbon Emissions Are Cut"

https://scitechdaily.com/ocean-may-absorb-less-co2-as-man-made-carbon-emissions-are-cut/

Extract: "Investigating how the Pinatubo eruption impacted global climate, and thus the ocean carbon sink, and whether the drop in emissions due to COVID-19 is reflected in the ocean are among the research team’s next plans.

By understanding variability in the ocean carbon sink, the scientists can continue to refine projections of how the ocean system will slow down.

McKinley cautions that as global emissions are cut, there will be an interim phase where the ocean carbon sink will slow down and not offset climate change as much as in the past. That extra carbon dioxide will remain in the atmosphere and contribute to additional warming, which may surprise some people, she said.

“We need to discuss this coming feedback. We want people to understand that there will be a time when the ocean will limit the effectiveness of mitigation actions, and this should also be accounted for in policymaking,” she said."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3367 on: June 22, 2020, 11:39:31 AM »
What will be the first hint that a MICI is starting?
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3368 on: June 22, 2020, 09:47:56 PM »
When ice shelves disappear and 100m freboard ice cliffs front directly to ocean.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3369 on: June 22, 2020, 11:56:27 PM »
To get back to the OP of this thread, if there is to be multiple meters of SLR this century, this implies an average per year of multiple cm per year, which has not happened. What is the SLR for the last twelve months and how does that compare to the average over the last decade? Do you expect them to go up in a curve? Or do you expect a rise of a cm a month for a decade? How would the change in current SLR happen to get such a huge rise in this century?

Hi Tom,

The tyranny of exponential growth. Let's take current SLR at 3mm/year. And a doubling time of 15 years (suggested by Hansen) - possibly optimistic given 6-fold increase in Antarctica in the last 30 years. In 75 years - 5 doublings produces 96mm/year in 2095. 96cm/decade = near enough 1m/decade by end of century. So MISI and MICI are interesting concepts and potentially have a large impact on SLR and need investigating but to a large extent are a diversion from the main problem. Another issue is only reporting SLR up to 2100. From the above this would be approx 1.75m SLR by 2100. That's OK to manage you say. But in 10 years after 2100 there would be another 2m SLR. In the decade after that potentially another 4m. I haven't seen any evidence suggesting that exponential growth would stop. What height wall do you build in 2100? A 2m high wall which will be useless in 10 years time. Let's make it 4m high then. That massively increases the cost and that will still be defunct in 20 to 30 years time. Answer: You don't build the wall at all. Like with covid-19, never play with exponential growth.


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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3370 on: June 23, 2020, 12:07:48 AM »
What will be the first hint that a MICI is starting?

To add a small amount of details to sidd's observation that the first hint of a MICI-type of failure mode for the WAIS can only begin where/when the ice shelf, or ice tongue, disappears and a 100m freeboard for the ice cliff face exists where the subsequent icebergs/melange can float away into the ocean I note that, in my opinion.

1. The location most at risk of initiating a MICI-type of failure is the area at the base of the Thwaites Ice Tongue where there is a  subglacier cavity (see the first image) that is actively being enlarged by relatively warm modified CDW from the associated ASE seafloor trough (see the second image) that is being flushed in & out of the cavity by daily tidal cycles.  Furthermore, the third image show upstream of the two subsea mounts that currently pins the seaboard end of the Thwaites Ice Tongue, there is a trough thru the Thwaites Gateway that leads directly into the Byrd Subglacial Basin, BSB, with a negative slope.

2. The fourth image shows baking's annotation on the Thwaites Ice Tongue on June 1, 2020; which in my opinion suggests the possibility that the Thwaites Ice Tongue could disappear as early as 2030 to 2035; which might expose an over 100m high ice cliff freeboard height at the upstream side of the subglacial cavity in that area that could propagate an MICI-type of failure mechanism down the trough thru the Thwaites gateway directly into the BSB.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3371 on: June 23, 2020, 12:21:52 AM »
The linked article indicates that on June 20, 2020; the Arctic (north of 66.6 oN) experienced its highest recorded temperature and summer had not even begun.

Title: "Arctic records its hottest temperature ever"

https://www.cbsnews.com/news/arctic-hottest-temperature-ever/

Extract: "Alarming heat scorched Siberia on Saturday as the small town of Verkhoyansk (67.5°N latitude) reached 100.4 degrees Fahrenheit, 32 degrees above the normal high temperature. If verified, this is likely the hottest temperature ever recorded in Siberia and also the hottest temperature ever recorded north of the Arctic Circle, which begins at 66.5°N."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3372 on: June 23, 2020, 12:56:26 AM »
Also, in the linked 2019 article, Rob DeConto (a very straight shooter) says that the basic conclusions of the DeConto & Pollard (2016) reference about MICI risks remains unchanged:

Title: "Doomsday Postponed? The Takeaway From the Big New Antarctica Studies"

https://www.motherjones.com/environment/2019/02/doomsday-postponed-the-takeaway-from-the-big-new-antarctica-studies/

Extract: "“We still see a dangerous threat,” Rob DeConto, one of the authors of the 2016 paper, said in an email to Grist. “I don’t really see ice fracture as an optional process that can be excluded from ice sheet models.”

“If the pace of calving we observe in Greenland today someday becomes widespread around the edges of the vastly bigger Antarctic ice sheet, it could cause very fast sea-level rise,” DeConto said. “This was the take home message from our 2016 paper. Based on all the work that has followed, that basic conclusion remains unchanged.”"

We're still waiting for the updated numbers from the DeConto and Pollard study, first promised in early 2019.

https://www.anthropology-news.org/index.php/2020/04/22/scientists-predict-the-future-for-antarctic-ice/?utm_source=rss&utm_medium=rss&utm_campaign=scientists-predict-the-future-for-antarctic-ice

Quote
The research with Pollard incorporated the IPCC’s Representative Concentration Pathways (RCP) into their ice sheet models, comparing the sea level rises associated with the various greenhouse gas emission scenarios that the IPCC uses to compare global circulation models. Their results—with their model including MICI for the first time—showed a meter of sea level rise coming from Antarctica by 2100, which was considerably higher than the likely range of 0.26–0.82m projected in IPCC’s Fifth Assessment Report (2013). However, DeConto told us in the audience that RCP2.6, a scenario that assumes rapid, successful global efforts to bring down carbon emissions worldwide, greatly reduces the risk of such a large, quick rise in sea level. He noted a “role for policy,” emphasizing that our climate future can still be adjusted through swift and serious policy action.

To my surprise, DeConto then launched into a frank discussion about how the article that resulted from their research was not included in the 2019 IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC), an assessment meant to update world decision makers on exactly the subject matter Pollard and DeConto had been working on. He, and the expert community he is aligned with, had realized that in their models “the climate forcing went too warm, too fast.” DeConto and Pollard immediately went to work fixing the issue but as he put it, the quantification “was not there” in time for SROCC.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3373 on: June 23, 2020, 01:02:49 AM »
For future reference, here is a look at what the end state will look like:
http://www.worlddreambank.org/D/DUBIA.HTM
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3374 on: June 23, 2020, 01:21:46 AM »
The link study reports on an updated survey of sea level experts for their projections of future sea level rise.

https://www.nature.com/articles/s41612-020-0121-5

Quote
Published: 08 May 2020

Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from an expert survey

Benjamin P. Horton, Nicole S. Khan, Niamh Cahill, Janice S. H. Lee, Timothy A. Shaw, Andra J. Garner, Andrew C. Kemp, Simon E. Engelhart & Stefan Rahmstorf

Climate and Atmospheric Science volume 3, Article number: 18 (2020)

Abstract

Sea-level rise projections and knowledge of their uncertainties are vital to make informed mitigation and adaptation decisions. To elicit projections from members of the scientific community regarding future global mean sea-level (GMSL) rise, we repeated a survey originally conducted five years ago. Under Representative Concentration Pathway (RCP) 2.6, 106 experts projected a likely (central 66% probability) GMSL rise of 0.30–0.65 m by 2100, and 0.54–2.15 m by 2300, relative to 1986–2005. Under RCP 8.5, the same experts projected a likely GMSL rise of 0.63–1.32 m by 2100, and 1.67–5.61 m by 2300. Expert projections for 2100 are similar to those from the original survey, although the projection for 2300 has extended tails and is higher than the original survey. Experts give a likelihood of 42% (original survey) and 45% (current survey) that under the high-emissions scenario GMSL rise will exceed the upper bound (0.98 m) of the likely range estimated by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, which is considered to have an exceedance likelihood of 17%. Responses to open-ended questions suggest that the increases in upper-end estimates and uncertainties arose from recent influential studies about the impact of marine ice cliff instability on the meltwater contribution to GMSL rise from the Antarctic Ice Sheet.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3375 on: June 23, 2020, 02:52:35 AM »
In the linked reference, Pollard and DeConto largely confirm their 2016 projections for the WAIS.  Furthermore, if they were adopt the TCR and ECS values from E3SM1 (one of the CMIP6 models) then their projected collapse dates for the WAIS under RCP8.5 would most likely be significantly earlier than indicated by the attached image.

Pollard, D. and DeConto, R.: Improvements in one-dimensional grounding-line parameterizations in an ice-sheet model with lateral variations, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2020-131, in review, 2020.

https://www.geosci-model-dev-discuss.net/gmd-2020-131/
https://www.geosci-model-dev-discuss.net/gmd-2020-131/gmd-2020-131.pdf

Abstract. The use of a boundary-layer parameterization of buttressing and ice flux across grounding lines in a two-dimensional ice-sheet model is improved by allowing general orientations of the grounding line. This and another modification to the model's grounding-line parameterization are assessed in two settings: a narrow fjord-like domain (MISMIP+), and in future simulations of West Antarctic ice retreat under RCP8.5-based climates. The new modifications are found to have significant effects on the fjord results, which are now within the envelopes of other models in the MISMIP+ intercomparison. In contrast, the modifications have little effect on West Antarctic retreat, presumably because dynamics in the wider major Antarctic basins are adequately represented by the model's previous simpler one-dimensional formulation. As future grounding lines retreat across very deep bedrock topography in the West Antarctic simulations, buttressing is weak and deviatoric stress measures exceed the ice yield stress, implying that structural failure at these grounding lines would occur. We suggest that these grounding-line quantities should be examined in similar projections by other ice models, to better assess the potential for future structural failure.

Caption: "Figure 7. Equivalent global sea level rise in simulations of future West Antarctic ice retreat with climate forcing based on the RCP8.5 greenhouse gas scenario. The sea-level rise calculation accounts for ice grounded below sea level, which if melted contributes only its ice-overflotation amount. Thin lines: with previous model (no modifications, version A). Medium lines: with new 2-D grounding-line orientation (section 2.1, version B). Thick lines: with new 2-D orientation and new grid-cell weighting of imposed grounding-line velocities (section 2.2, version C). Blue: control (perpetual modern climate). Green: with RCP8.5 forcing, without hydrofracturing or cliff failure. Red: with RCP8.5 forcing, with hydrofracturing and cliff failure."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3376 on: June 23, 2020, 03:37:56 AM »
While the linked op/ed article does not appear to offer any new information; nevertheless, it may (or may not) be an indicator that consensus climate science may increase the range of climate sensitivity values in AR6:

Title: "Climate change: Scotland's emissions rise as world heads for catastrophic 5C of global warming – Dr Richard Dixon"

https://www.scotsman.com/news/opinion/columnists/climate-change-scotlands-emissions-rise-world-heads-catastrophic-5c-global-warming-dr-richard-dixon-2891584

Extract: "Scientists putting together the latest global assessment of climate change science revealed that a better understanding of the role of clouds in a warmer world mean a key assumption that has held steady for 30 years may be wrong, meaning the Earth’s atmosphere is more sensitive to changes in greenhouse gases than previously thought.

The early indications are that business-as-usual predictions of the world reaching a disastrous 3C of warming by 2100 should now be revised upwards to a catastrophic 5C. This would also mean that the already very difficult goal of keeping the temperature rise below 1.5C is beyond humanity’s ability."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3377 on: June 23, 2020, 03:44:47 AM »
The linked reference, and associated linked article, indicates that private land purchases are accelerating tropical deforestation.

Davis, K.F., Koo, H.I., Dell’Angelo, J. et al. Tropical forest loss enhanced by large-scale land acquisitions. Nat. Geosci. (2020). https://doi.org/10.1038/s41561-020-0592-3

https://www.nature.com/articles/s41561-020-0592-3

Abstract: "Tropical forests are vital for global biodiversity, carbon storage and local livelihoods, yet they are increasingly under threat from human activities. Large-scale land acquisitions have emerged as an important mechanism linking global resource demands to forests in the Global South, yet their influence on tropical deforestation remains unclear. Here we perform a multicountry assessment of the links between large-scale land acquisitions and tropical forest loss by combining a new georeferenced database of 82,403 individual land deals—covering 15 countries in Latin America, sub-Saharan Africa and Southeast Asia—with data on annual forest cover and loss between 2000 and 2018. We find that land acquisitions cover between 6% and 59% of study-country land area and between 2% and 79% of their forests. Compared with non-investment areas, large-scale land acquisitions were granted in areas of higher forest cover in 11 countries and had higher forest loss in 52% of cases. Oil palm, wood fibre and tree plantations were consistently linked with enhanced forest loss while logging and mining concessions showed a mix of outcomes. Our findings demonstrate that large-scale land acquisitions can lead to elevated deforestation of tropical forests, highlighting the role of local policies in the sustainable management of these ecosystems."

See also:

Title: "Land purchases by private companies accelerate tropical deforestation, data shows"

https://www.carbonbrief.org/land-purchases-by-private-companies-accelerate-tropical-deforestation-data-shows

Extract: "The buying up of tropical forest by private companies and foreign governments enhances deforestation in the majority of cases, new data confirms.

Palm oil, wood fibre and tree plantations were the commodities most consistently linked with increased tropical deforestation over the past two decades, according to the study.

The assessment, published in Nature Geosciences, explores the consequences of more than 80,000 land deals made from 2000 to 2018 across 15 countries in South America, sub-Saharan Africa and south-east Asia."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3378 on: June 23, 2020, 03:54:14 PM »
In the linked reference, Pollard and DeConto largely confirm their 2016 projections for the WAIS.  Furthermore, if they were adopt the TCR and ECS values from E3SM1 (one of the CMIP6 models) then their projected collapse dates for the WAIS under RCP8.5 would most likely be significantly earlier than indicated by the attached image.

Pollard, D. and DeConto, R.: Improvements in one-dimensional grounding-line parameterizations in an ice-sheet model with lateral variations, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2020-131, in review, 2020.

https://www.geosci-model-dev-discuss.net/gmd-2020-131/
https://www.geosci-model-dev-discuss.net/gmd-2020-131/gmd-2020-131.pdf

...
Caption: "Figure 7. Equivalent global sea level rise in simulations of future West Antarctic ice retreat with climate forcing based on the RCP8.5 greenhouse gas scenario. The sea-level rise calculation accounts for ice grounded below sea level, which if melted contributes only its ice-overflotation amount. Thin lines: with previous model (no modifications, version A). Medium lines: with new 2-D grounding-line orientation (section 2.1, version B). Thick lines: with new 2-D orientation and new grid-cell weighting of imposed grounding-line velocities (section 2.2, version C). Blue: control (perpetual modern climate). Green: with RCP8.5 forcing, without hydrofracturing or cliff failure. Red: with RCP8.5 forcing, with hydrofracturing and cliff failure."

In a perfect world after the Trump administration ends in January 2021, the DOE would reach-out to Pollard & DeConto (2020, see the first attached image); and engage their input for E3SMv4 which should provide input to CMIP7 (see the second attached image).  This would give us all a much better idea of the climate risks that we all are facing.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3379 on: June 23, 2020, 05:49:47 PM »
Now that the field phase of the International Thwaites Glacier Collaboration is complete, I can recommend periodically monitoring the linked websites in the coming weeks & months for updates as the field data is analyzed from the eight associated projects (see the attached image):

Title: "The International Thwaites Glacier Collaboration"

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

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

See also:

For the project Twitter site, see:

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

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

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

https://thwaitesglacier.org/projects/dominos

Extract: "Currently, it is difficult to model calving and its complex interactions with atmospheric and oceanic conditions. The DOMINOS team will use a novel ice-dynamic model suite coupled with an ocean forcing model suite. This model suite includes a discrete element model capable of simulating coupled fracture and ice-flow processes, a 3D full Stokes continuum model, and the continental scale ice-dynamics model BISICLES. Ice dynamics models will be coupled to an ocean forcing model suite including simple plume models, intermediate complexity 2-layer ocean models and fully 3D regional ocean models. This hierarchical approach will use high-fidelity process models to inform and constrain the sequence of lower-order models needed to extrapolate improved understanding to larger scales and has the potential to radically reduce uncertainty of rates of marine ice sheet collapse and associated sea level rise."
&

Furthermore, I note that the Thwaites Drainage Basin can merge together with the Pine Island Drainage Basin as the Thwaites Glacier Eastern Shear Margin migrates outward (& I note that this outward migration has been accelerated by the recent reduction in ice shelf buttressing on the Southwest Tributary Glacier.

Title: "Thwaites Interdisciplinary Margin Evolution - The Role of Shear Margin Dynamics in the Future Evolution of Thwaites Drainage Basin (TIME)"

https://thwaitesglacier.org/projects/time

Extract: "If the Thwaites Glacier Eastern Shear Margin migrates outwards it could join the Pine Island Glacier, connecting the two glaciers which are already making large contributions to sea-level rise."

See also:
Title: "Melting at Thwaites grounding zone and its control on sea level (MELT)"

https://thwaitesglacier.org/projects/melt

Extract: "MELT is an ice-based project to understand how warm waters are affecting the Thwaites Glacier at the grounding line – the point where the glacier goes afloat to become ice shelf. This will allow the glacier’s potential sea-level contribution to be more accurately predicted."
&

Title: "Thwaites Offshore Research (THOR)"

https://thwaitesglacier.org/projects/thor

Extract: "Thwaites Offshore Research (THOR) is a ship-based and ice-based project that will examine the sedimentary records both offshore from the glacier and beneath the ice shelf, together with glacial landforms on the sea bed, to reconstruct past changes in ocean conditions and the glaciers response to these changes."
&

Title: "Geophysical Habitat of Subglacial Thwaites (GHOST)"

https://thwaitesglacier.org/projects/ghost

Extract: "GHOST is an ice-based project which will examine the bed beneath the Thwaites Glacier, to assess whether conditions are likely to allow rapid retreat, or if the retreat may slow or stop due to a ridge 70 km inland."
&

Title: "Geological History Constraints on the Magnitude of Grounding-Line Retreat in the Thwaites Glacier System (GHC)"

https://thwaitesglacier.org/projects/ghc

Extract: "GHC will gather information about past ice sheet behavior and relative sea level change in the Thwaites Glacier system. Determining the timing and magnitude of past episodes of thinning and retreat and subsequent re-advance is important to provide a context for the current and future behavior of Thwaites Glacier and its influence on global sea level."
&

Title: "Thwaites-Amundsen Regional Survey and Network Integrating Atmosphere-Ice-Ocean Processes (TARSAN)"

https://thwaitesglacier.org/projects/tarsan

Extract: "TARSAN is a ship-based project studying how atmospheric and oceanic processes are influencing the behavior of the Thwaites and Dotson Ice Shelves – neighboring ice shelves which are behaving differently."
&

Title: "Processes, drivers, Prediction: modeling the History and Evolution of Thwaites (PROPHET)"

https://thwaitesglacier.org/projects/prophet

Extract: "PROPHET is a computer modelling based project which aims to improve the representation of several key processes (calving, ice damage and basal conditions), which are not currently characterized well in large scale ice-flow models."
&

Title: "The Future of Thwaites Glacier and its Contribution to Sea-level Rise Science Coordination Office Proposal (SCO)"

https://thwaitesglacier.org/projects/sco

Extract: "The ITGC Science Coordination Office coordinates the eight funded research projects to deliver the best possible science for the funding agencies and the public of both the US and UK."

In addition to the MICI work that Pollard and DeConto are doing, I note that the Disintegration of Marine Ice-sheets Using Novel Optimised Simulations (DOMINOS) is also work on MICI modeling.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3380 on: June 23, 2020, 06:42:07 PM »
In the linked reference, Pollard and DeConto largely confirm their 2016 projections for the WAIS.  Furthermore, if they were adopt the TCR and ECS values from E3SM1 (one of the CMIP6 models) then their projected collapse dates for the WAIS under RCP8.5 would most likely be significantly earlier than indicated by the attached image.

Pollard, D. and DeConto, R.: Improvements in one-dimensional grounding-line parameterizations in an ice-sheet model with lateral variations, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2020-131, in review, 2020.

https://www.geosci-model-dev-discuss.net/gmd-2020-131/
https://www.geosci-model-dev-discuss.net/gmd-2020-131/gmd-2020-131.pdf

Abstract. The use of a boundary-layer parameterization of buttressing and ice flux across grounding lines in a two-dimensional ice-sheet model is improved by allowing general orientations of the grounding line. This and another modification to the model's grounding-line parameterization are assessed in two settings: a narrow fjord-like domain (MISMIP+), and in future simulations of West Antarctic ice retreat under RCP8.5-based climates. The new modifications are found to have significant effects on the fjord results, which are now within the envelopes of other models in the MISMIP+ intercomparison. In contrast, the modifications have little effect on West Antarctic retreat, presumably because dynamics in the wider major Antarctic basins are adequately represented by the model's previous simpler one-dimensional formulation. As future grounding lines retreat across very deep bedrock topography in the West Antarctic simulations, buttressing is weak and deviatoric stress measures exceed the ice yield stress, implying that structural failure at these grounding lines would occur. We suggest that these grounding-line quantities should be examined in similar projections by other ice models, to better assess the potential for future structural failure.

Caption: "Figure 7. Equivalent global sea level rise in simulations of future West Antarctic ice retreat with climate forcing based on the RCP8.5 greenhouse gas scenario. The sea-level rise calculation accounts for ice grounded below sea level, which if melted contributes only its ice-overflotation amount. Thin lines: with previous model (no modifications, version A). Medium lines: with new 2-D grounding-line orientation (section 2.1, version B). Thick lines: with new 2-D orientation and new grid-cell weighting of imposed grounding-line velocities (section 2.2, version C). Blue: control (perpetual modern climate). Green: with RCP8.5 forcing, without hydrofracturing or cliff failure. Red: with RCP8.5 forcing, with hydrofracturing and cliff failure."

Why did they do a new paper using the "extreme" (their word) RCP 8.5 scenario (red line in their graph)?  I think most scientists recognize that RCP 8.5 is incredibly unrealistic now, given the complete collapse of coal mining and the rapid ascent of wind and solar.



The current forcings, continued, is somewhere between RCP 4.5 and 2.6.  It's represented by the blue line in their graph.  It would appear to be more realistic, if less sensational.



Quote
Figure  7.  Equivalent  global  sea  level  rise  in  simulations  of  future  West  Antarctic  ice  retreat  with  climate  forcing  based  on  the  RCP8.5 greenhouse gas scenario. The sea-level rise calculation accounts for ice grounded below sea level, which if melted contributes only its ice-over-260 flotation  amount. Thin  lines:  with  previous  model  (no  modifications,  version  A).Medium  lines:  with  new  2-D  grounding-line  orientation (section 2.1, version B). Thick lines: with new 2-D orientation and new grid-cell weighting of imposed grounding-line velocities (section 2.2, version C). Blue: control (perpetual modern climate). Green: with RCP8.5 forcing, without hydrofracturing or cliff failure. Red: with RCP8.5 forcing, with hydrofracturing and cliff failure.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3381 on: June 23, 2020, 07:01:58 PM »
...

Why did they do a new paper using the "extreme" (their word) RCP 8.5 scenario (red line in their graph)?  I think most scientists recognize that RCP 8.5 is incredibly unrealistic now, given the complete collapse of coal mining and the rapid ascent of wind and solar.
...

The current forcings, continued, is somewhere between RCP 4.5 and 2.6.  It's represented by the blue line in their graph.  It would appear to be more realistic, if less sensational.
...

In my opinion (as I do not speak for either Pollard or DeConto) they likely believe that good risk management demands the evaluation of an 'extreme' case even if the RCP 8.5 scenario is not followed explicitly but that would achieve the equivalent radiative forcing such as would be the case if TCR were to be 2.93C and/or ECS were to be 5.2C as projected by E3SM1 (but was left out of their analysis by necessity); as currently no model is capable of exactly simulating future climate change.

Edit: Another risk factor that using the RCP 8.5 scenario might help to cover in the Pollard & DeConto 2020 model, would be the risk that they are underestimating the current negative feedback associated with anthropogenic aerosol emissions, so that when those emissions are reduced in the future (and/or as during the COVID-19 situation) there may be higher radiative forcing than assumed say by RCP 6.0.

Edit2: The Pollard & DeConto (2020) model closely associates the lose of the buttressing ice shelves with future local austral summer surface temperatures that are sufficiently high to produce sufficient surface meltwater to induce hydrofracturing of the ice shelves.  However, particularly for the Thwaites Ice Tongue this assumption may not be necessary for the near-term loss of the Thwaites Ice Tongue.  Thus Pollard & DeConto (2020)'s inclusion of RCP 8.5 could help to deal with extreme risks associated with such an early loss of the Thwaites Ice Tongue even if RCP 8.5 is not followed explicitly.

Edit3: The Pollard & DeConto (2020) model also does not account for the large amount of surplus freshwater accumulated in the Beaufort Gyre which could discharge sufficient relatively freshwater into the North Atlantic to significantly slow the AMOC (MOC) at anytime; which, per the bipolar seesaw mechanism would induce an abrupt increase in surface temperatures in West Antarctica (advected from the Tropical Pacific).  Thus their evaluation of RCP 8.5 helps to address this climate risk even if anthropogenic GHG emissions turnout to be lower than assumed by RCP 8.5 in coming years.
« Last Edit: June 24, 2020, 12:30:22 AM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3382 on: June 23, 2020, 10:40:10 PM »
More information has come in on the CMIP 6 models and Realclimate has an update:

http://www.realclimate.org/index.php/archives/2020/06/sensitive-but-unclassified-part-ii/#more-23118

Quote
Sensitive but unclassified: Part II
Filed under:

    Climate modelling Climate Science

— gavin @ 13 June 2020

The discussion and analysis of the latest round of climate models continues – but not always sensibly.

In a previous post, I discussed the preliminary results from the ongoing CMIP6 exercise – an international, multi-institutional, coordinated and massive suite of climate model simulations – and noted that they exhibited a wider range of equilibrium climate sensitivities (ECS) than in previous phases (CMIP5 and earlier) and wider than the assessed range based on observational constraints (of many kinds).

Since then, more model results have been added to the archive, and thanks to Mark Zelinka, we can see some of the analysis as it updates in real time.



Quote
Since my first post, there have been a number of papers have looked at the skill of these models to see whether there are some key observational data that might help in constraining the sensitivity (and by extension, the projections into the future). One set of papers has focused on the global mean trends from 1990 or so onward which is a period of stable or declining aerosol trends and which might therefore be a closer test of the models’ transient sensitivity to CO2 than earlier periods. Notably Tokarska et al. (2020) and Njisse et al. (2020) suggest that many of the high ECS group warm substantially faster than observed over this period and therefore should be downweighted in the constrained projections of the future.

Quote
In the meantime, claims that climate sensitivity is much higher, or that worst cases scenarios need to be revised upwards, are premature.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3383 on: June 23, 2020, 11:40:53 PM »
More information has come in on the CMIP 6 models and Realclimate has an update:

Quote
Since my first post, there have been a number of papers have looked at the skill of these models to see whether there are some key observational data that might help in constraining the sensitivity (and by extension, the projections into the future). One set of papers has focused on the global mean trends from 1990 or so onward which is a period of stable or declining aerosol trends and which might therefore be a closer test of the models’ transient sensitivity to CO2 than earlier periods. Notably Tokarska et al. (2020) and Njisse et al. (2020) suggest that many of the high ECS group warm substantially faster than observed over this period and therefore should be downweighted in the constrained projections of the future.

Quote
In the meantime, claims that climate sensitivity is much higher, or that worst cases scenarios need to be revised upwards, are premature.

While Gavin Schmidt is more than welcome to express his opinions, first he is only one man and not the whole AR6 committee; and second in AR5 the committee did not apply a downweighting factor to some of the inappropriate low estimates of ECS included in their assessment.

Edit: Also, I note that if AR6 does decide to us weighting factors on ECS projections then they should also downweight the Russian (INM CM4/5) projection of ECS.
« Last Edit: June 24, 2020, 12:33:15 AM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3384 on: June 23, 2020, 11:53:39 PM »
From the attached image of two of Hausfather's tweets today there is a reasonable probability that GMSTA will reach 4.7C following an emissions path well below that assumed for RCP 8.5; and he encourages people to make more efforts to reduce GHG emissions.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3385 on: June 24, 2020, 01:03:27 AM »
Mmm. I hope Gavin expands on the meltwater hypothesis some more at realclimate. One consequence (which is in the Golledge paper linked from the twitter thread) is increased melt from Antarctica, which will add to the effect ...

Need better analysis of ice melt impact on oceans for CMIP7 or faster. In this context i have been consulting the hosing experiments, but they are a limited tool compared to the CMIP ensembles. I wonder if anyone is doing hosing with CMIP6 models ?

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3386 on: June 24, 2020, 02:44:16 AM »
Mmm. I hope Gavin expands on the meltwater hypothesis some more at realclimate. One consequence (which is in the Golledge paper linked from the twitter thread) is increased melt from Antarctica, which will add to the effect ...

Need better analysis of ice melt impact on oceans for CMIP7 or faster. In this context i have been consulting the hosing experiments, but they are a limited tool compared to the CMIP ensembles. I wonder if anyone is doing hosing with CMIP6 models ?

sidd

sidd,

If you want to look at the whole CMIP6 they you can look at the following reference:


Lyu et al (2020), "Regional Dynamic Sea Level Simulated in the CMIP5 and CMIP6 Models: Mean Biases, Future Projections, and Their Linkages", Journal of Climate,  33 (15): 6377–6398, https://doi.org/10.1175/JCLI-D-19-1029.1

https://journals.ametsoc.org/jcli/article/33/15/6377/346684/Regional-Dynamic-Sea-Level-Simulated-in-the-CMIP5

Abstract
The ocean dynamic sea level (DSL) is an important component of regional sea level projections. In this study, we analyze mean states and future projections of the DSL from the global coupled climate models participating in phase 5 and phase 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively). Despite persistent biases relative to observations, both CMIP5 and CMIP6 simulate the mean sea level reasonably well. The equatorward bias of the Southern Hemisphere westerly wind stress is reduced from CMIP5 to CMIP6, which improves the simulated mean sea level in the Southern Ocean. The CMIP5 and CMIP6 DSL projections exhibit very similar features and intermodel uncertainties. With several models having a notably high climate sensitivity, CMIP6 projects larger DSL changes in the North Atlantic and Arctic associated with a larger weakening of the Atlantic meridional overturning circulation (AMOC). We further identify linkages between model mean states and future projections by looking for their intermodel relationships. The common cold-tongue bias leads to an underestimation of DSL rise in the western tropical Pacific. Models with their simulated midlatitude westerly winds located more equatorward tend to project larger DSL changes in the Southern Ocean and North Pacific. In contrast, a more equatorward location of the North Atlantic westerly winds or a weaker AMOC under current climatology is associated with a smaller weakening of the AMOC and weaker DSL changes in the North Atlantic and coastal Arctic. Our study provides useful emergent constraints for DSL projections and highlights the importance of reducing model mean-state biases for future projections.

However, I am not convinced that Lyu et al. (2020) gives proper consideration of the E3SMv1 or the E3SMv1.1, both of which clearly consider the influence of ice meltwater on both the MOC and on TCR.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3387 on: June 24, 2020, 09:04:39 AM »
E3SMvx is the one to watch. Are they stable yet ?

Another thing i want to see the models get right is ITCZ.

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3388 on: June 24, 2020, 10:27:00 AM »
...

Edit: Also, I note that if AR6 does decide to us weighting factors on ECS projections then they should also downweight the Russian (INM CM4/5) projection of ECS.

INM CM4 and CM5 models are among the ones that track actual temperature developments best. So might be a good idea to keep them - maybe they are the ones that will be demonstrated to have gotten the hydro cycle, as well as the cloud feedback right?
In the first attached 'spaghetti' chart, the INM CM4 is one of the blue ones near the bottom of the spaghetti bowl. Rather close to the actual HadCrut temperatures compared to many high-flying models.
In the second attached chart models are compared in terms of contributions to ECS from different factors.
In the third attached chart models are compared in terms of cloud feedback contributions.

The high-flying models have more to prove in terms of tracking actual temperatures, than their more realistic competitors. So what's the argument, ASLR, why should they be "downweighted", as you propose? Because they don't err on the side of maximum ECS drama?

https://www.climate-lab-book.ac.uk/comparing-cmip5-observations/
https://link.springer.com/article/10.1134/S000143381004002X

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3389 on: June 24, 2020, 05:07:42 PM »
E3SMvx is the one to watch. Are they stable yet ?

Another thing i want to see the models get right is ITCZ.

sidd

Currently, DOE is working on E3SMv2 and you can monitor progress at the linked newsletter archive website:

Title: "E3SM Floating Points"

https://e3sm.org/about/news/newsletter-archive/

See also:

https://us18.campaign-archive.com/?u=11f9e1f9713b9366390852682&id=08d955a3d9
&
https://us18.campaign-archive.com/?u=11f9e1f9713b9366390852682&id=d44c939329

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3390 on: June 24, 2020, 05:39:57 PM »
...
The high-flying models have more to prove in terms of tracking actual temperatures, than their more realistic competitors. So what's the argument, ASLR, why should they be "downweighted", as you propose? Because they don't err on the side of maximum ECS drama?
...

It is clear that climate change is more complex than any current model can simulate, thus it is bad science to keep focusing on relatively simple models and then demanding unreasonable accuracy from more nonlinear models, as the use of simple models for a complex system entails a large degree of climate risk.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3391 on: June 24, 2020, 07:02:03 PM »
...

Edit: Also, I note that if AR6 does decide to us weighting factors on ECS projections then they should also downweight the Russian (INM CM4/5) projection of ECS.

INM CM4 and CM5 models are among the ones that track actual temperature developments best. So might be a good idea to keep them - maybe they are the ones that will be demonstrated to have gotten the hydro cycle, as well as the cloud feedback right?
<-- cut -->
https://www.climate-lab-book.ac.uk/comparing-cmip5-observations/
https://link.springer.com/article/10.1134/S000143381004002X
The problem in the statement above is the word "actual". What is actual?

From the same climate-lab-book page link provided (so clear and obvious that it would be hard to miss. Surprising that it was not mentioned when presenting the evidence):
 
"The simulation data uses spatially complete coverage of surface air temperature whereas the observations use a spatially incomplete mix of air temperatures over land and sea surface temperatures over the ocean. It is expected that this factor alone would cause the observations to show smaller trends than the simulations."

How well do the various models perform if the above factor was applied to observational temperature or use of a more spatially complete data set? e,g. Cowtan and Way (although not perfect widely accepted to be a more accurate record of global temperature increase. Remember - here we're trying to evaluate the accuracy of the models over a relatively short time period (not track global temperatures over a long time period).


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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3392 on: June 24, 2020, 07:22:09 PM »
...
The high-flying models have more to prove in terms of tracking actual temperatures, than their more realistic competitors. So what's the argument, ASLR, why should they be "downweighted", as you propose? Because they don't err on the side of maximum ECS drama?
...

It is clear that climate change is more complex than any current model can simulate, thus it is bad science to keep focusing on relatively simple models and then demanding unreasonable accuracy from more nonlinear models, as the use of simple models for a complex system entails a large degree of climate risk.

It's also bad science to focus on the few models that appear to be outliers, denigrate the vast majority of other models and ignore the paleoclimate evidence that supports a lower ECS.

The aforementioned Zeke Hausfather has a good article on this:

https://thebreakthrough.org/issues/energy/cold-water-hot-models

Quote
Cold Water on Hot Models
Feb 11, 2020

News headlines have recently warned about “troubling” new warming projections from climate models that are “running red hot.” In reality, these only represent a small subset of the new models currently being developed — most of which are not running notably “hot.” And many of the “hot” models do a relatively poor job of reproducing past temperature changes, an important test of model skill. Climate scientists use many different lines of evidence to estimate how sensitive the climate is to increasing greenhouse gas concentrations, and it is premature to conclude that climate sensitivity is likely higher than we previously thought.



Quote
Many high sensitivity models have poor hindcasts

Climate models provide both projections of future warming and “hindcasts” of past temperatures. These hindcasts can be used as a tool to evaluate the performance of models, though historical temperatures are only one of many hundreds of different variables that climate models generate.

A number of the higher sensitivity models in CMIP6 have had trouble accurately “hindcasting” historical temperatures. Some show almost no warming over the 20th century — with cooling effects from aerosols almost completely counterbalancing rising atmospheric greenhouse gas concentrations — followed by a massive warming spike in recent decades. Others show too much warming over the past 150 years.



Quote
High sensitivity models (in red) generally show more warming than observations over the last three decades, while those with a TCR of around 2.2C or less (in blue) tend to agree much better with observations. High ECS models tend to have high TCR, though the two measures of sensitivity are not perfectly correlated. In this case, all the models in the figure with an ECS above 5C (except for one — CESM2) also have a TCR value above 2.5C.

Quote
Climate sensitivity should be based on multiple lines of evidence

Models are an important way that climate scientists estimate sensitivity, but they’re far from the only one. Sensitivity can also be estimated by applying emergent constraints to climate models — for example, identifying which models perform better on observable metrics such as cloud behavior that are correlated with climate sensitivity. Sensitivity can also be inferred from the instrumental temperature records over the past 150 years, as well as from climate proxy records from the Earth’s more distant past — periods such as recent ice ages, the Pliocene, or the Eocene.

By considering these multiple lines of evidence — rather than just a subset of the latest climate models — we get a more nuanced view of climate sensitivity than if we only rely on the latest climate models. The figure below shows the climate sensitivity range inferred from various types of studies, based on a review of 142 estimates published between 2001 and 2018.



Quote
These new 5C ECS models should remind us that large uncertainties (and long tails of risk) remain, but they do not by themselves overturn the long-term consensus that climate sensitivity is likely somewhere around 3C (+/- 1.5C) per doubling of CO2.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3393 on: June 24, 2020, 08:37:18 PM »
...
It's also bad science to focus on the few models that appear to be outliers, denigrate the vast majority of other models and ignore the paleoclimate evidence that supports a lower ECS.

The aforementioned Zeke Hausfather has a good article on this:

https://thebreakthrough.org/issues/energy/cold-water-hot-models
...

Similar arguments that Hausfather makes about the hot CMIP6 model projections could be made about any CMIP model as no model is perfect but some models are useful.  Therefore, I recommend that AR6 consider all CMIP6 model results without downweighting any of the projections as there is clearly a lot of uncertainty associated with all model projections.

Furthermore, I recommend that AR6 include a meaningful write-up about climate risks and unknowns so that decision makers cannot say in the future that they were not warned.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3394 on: June 25, 2020, 12:27:36 AM »

The problem in the statement above is the word "actual". What is actual?

From the same climate-lab-book page link provided (so clear and obvious that it would be hard to miss. Surprising that it was not mentioned when presenting the evidence):
 
"The simulation data uses spatially complete coverage of surface air temperature whereas the observations use a spatially incomplete mix of air temperatures over land and sea surface temperatures over the ocean. It is expected that this factor alone would cause the observations to show smaller trends than the simulations."

How well do the various models perform if the above factor was applied to observational temperature or use of a more spatially complete data set? e,g. Cowtan and Way (although not perfect widely accepted to be a more accurate record of global temperature increase. Remember - here we're trying to evaluate the accuracy of the models over a relatively short time period (not track global temperatures over a long time period).

Good question!
Moyhu has a nice portal where you can follow various temperature data. It's updated each day.
I plotted six series with land and ocean temps in the attached chart.
Cowtan and Way - dark green
HadCrut - red
GISS - light brown
NOAA - dark brown
BEST - light green
Temp LS Mesh - lila

CW updating is lagging.
All series are showing the same development, with small variations.
To answer your question, no, it wouldn't change the evaluation. Models are running hot irrespective of which temperature data you use.

https://moyhu.blogspot.com/p/latest-ice-and-temperature-data.html

Here is a description of the method for creating Temp LS Mesh, which is a similar attempt to CW to create more spatially complete data by applying statistical methods.

https://moyhu.blogspot.com/2019/10/new-femloess-method-of-integrating.html
https://moyhu.blogspot.com/p/a-guide-to-global-temperature-program.html
« Last Edit: June 25, 2020, 01:12:18 AM by Hefaistos »

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3395 on: June 25, 2020, 11:16:07 AM »
...

Good question!
Moyhu has a nice portal where you can follow various temperature data. It's updated each day.
...

Something is going wrong at Moyhu as for instance, the first attached image from the linked Moyhu website shows that no month in 2020 has been the warmest on record.

http://www.moyhu.org.s3.amazonaws.com/data/freq/ncep.html

Yet, NOAA, NASA and Copernicus (see the second attached image where Hausfather uses Copernicus data thru the end of May 2020 to project that 2020 will be the warmest year on record) all indicate that all months thru May 2020 were the warmest on record.

Thus until Moyhu's data falls in line with the observed NOAA, NASA and Copernicus observed data, I am inclined to ignore all data from Moyhu.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3396 on: June 25, 2020, 11:23:45 AM »
...
Seems relevant to ask, have these CMIP models with unbelievably high ECS values got their fundamental physics reg. clouds and water vapor right?

First, no model is perfect but some models are useful (& thus should not be ignored). 

Models that can be characterized as GIGO should be ignored.
...

Of course if the CMIP models are assuming that feedback from aerosol emissions are less negative than that feedback actually is then then the CMIP5 projections might be matching the recently observed record by using two wrongs to make a right; while the high-end CMIP6 projections might not match the observed record as well but may be projecting the future better if/when anthropogenic aerosol emissions are reduced (such as they have been for the first five months of 2020 when the month GMSTA values have been at record highs).  Thus, when uncertainty is involved who is to say what constitutes garbage in-garbage out (GIGO) w.r.t. modeling; however, the climate risks associated with the high-end CMIP6 projections are so high as to justify the adoption of the Precautionary Principle.

New research paper published that evaluates CMIP6 models.
"Context for interpreting equilibrium climate sensitivity and transient climate response from the CMIP6 Earth system models" by Meehl et al. Science Advances  24 Jun 2020, Vol. 6, no. 26,
From the Abstract
"....Here we review and synthesize the latest developments in ECS and TCR values in CMIP, compile possible reasons for the current values as supplied by the modeling groups, and highlight future directions. Cloud feedbacks and cloud-aerosol interactions are the most likely contributors to the high values and increased range of ECS in CMIP6."

Accompanying presentation of the research:
"Increased warming in latest generation of climate models likely caused by clouds
New representations of clouds are making models more sensitive to carbon dioxide"
Jun 24, 2020 - by Laura Snider

"“Cloud-aerosol interactions are on the bleeding edge of our comprehension of how the climate system works, and it’s a challenge to model what we don’t understand,” Meehl said. “These modelers are pushing the boundaries of human understanding, and I am hopeful that this uncertainty will motivate new science.”"

Can you really model something that you don't understand? Yes, you can. But it will definitely be GIGO.

https://advances.sciencemag.org/content/6/26/eaba1981
DOI: 10.1126/sciadv.aba1981

https://news.ucar.edu/132741/increased-warming-latest-generation-climate-models-likely-caused-clouds

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3397 on: June 25, 2020, 11:38:27 AM »
The linked open access reference indicates that over the past two decades that sea spray aerosols has significantly changed the aerosol light scattering properties over the Zeppelin observatory, Svalbard.  This raises the question as to whether this trend is contributing to Arctic Amplification?

Heslin-Rees, D., Burgos, M., Hansson, H.-C., Krejci, R., Ström, J., Tunved, P., and Zieger, P.: From a polar to a marine environment: has the changing Arctic led to a shift in aerosol light scattering properties?, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2020-521, in review, 2020.

https://www.atmos-chem-phys-discuss.net/acp-2020-521/

Abstract. The study of long-term trends in aerosol optical properties is an important task to understand the underlying aerosol processes influencing the change of climate. The Arctic, as the place where climate change manifests most, is an especially sensitive region of the world. Within this work, we use a unique long-term data record of key aerosol optical properties from Zeppelin observatory, Svalbard, to ask the question of whether the environmental changes of the last two decades in the Arctic are reflected in the observations. We perform a trend analysis of the measured particle light scattering and backscattering coefficients and the derived scattering Ångström exponent and hemispheric backscattering fraction. In contrast to previous studies, the effect of in-cloud scavenging and potential sampling losses at the site is taken explicitly into account in the trend analysis. The analysis is combined with a back trajectory analysis and satellite-derived sea ice data, to support the interpretation of the observed trends. We find that the optical properties of aerosol particles have undergone clear and significant changes in the past two decades. The scattering Angström exponent and the particle light scattering coefficient exhibit statistically significant decreasing of between −4.9 and −6.3 % per year (using wavelengths of λ = 450 and 550 nm) and increasing trends of between 2.3 and 2.9 % per year (at a wavelength of λ = 550 nm), respectively. The magnitudes of the trends vary depending on the season. These trends indicate a shift to an aerosol dominated more by coarse-mode particles, most likely the result of increases in the relative amount of sea spray aerosol. We show that changes in air mass circulation patterns, specifically an increase in air masses from the south-west, are responsible for the shift in aerosol optical properties, while the decrease of Arctic sea ice in the last two decades had only a marginal influence on the observed trends.

Extract: "Aerosol composition at ZEP has undergone significant changes over the last two decades, manifesting in a clear shift of aerosol light scattering properties. The statistically significant increasing trend in σsp of ∼2.4 to 2.9%yr−1 combined with a statistically significant decreasing trend in α of around -4.9 to 6.3%yr−1 , demonstrates that aerosol observed at ZEP have become more dominated by coarse-mode particles over time, which in turn contribute a greater proportion to the scattering of light. There is a clear open water dependency on α, suggesting that the increasing trend is a result of marine influences leading to increased transport of SSA to the site. The strong decrease of Arctic sea ice over the last decades, leading to more open water, is, however, not the main reason for the increased contribution of SSA. Here, we demonstrate, that the growing marine influence is originating from an increasing time back trajectories spend over the open water particularly south-west from Svalbard. As such, the changes in air circulation patterns have resulted in a characteristic shift of ZEP, from an Arctic towards a more marine dominated site.

ZEP is a site that requires detailed analysis, given the significance and magnitude of the observed trends. The results in this study suggest that climate-related changes are influencing the transportation of aerosol particles in and to the Arctic region, as well as the processing and sources of particles. It is important to note that the results are site dependent and that no general conclusions for the entire Arctic can be made."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3398 on: June 25, 2020, 11:47:57 AM »
The linked reference discusses a new method that "… can thus help to reveal hidden “climate surprises” and to assess the uncertainties of dangerous climate events."  Furthermore, when the authors applied the method to all monthly 2D variables of the RCP8.5 scenario of the CMIP5 projection; they found that:

"More than half of all simulations show abrupt shifts of more than 4 standard deviations on a time scale of 10 years."

Sebastian Bathiany, Johan Hidding and Marten Scheffer (2020), "Edge Detection Reveals Abrupt and Extreme Climate Events", J. Climate , 33 (15): 6399–6421, https://doi.org/10.1175/JCLI-D-19-0449.1

https://journals.ametsoc.org/jcli/article/33/15/6399/346908/Edge-Detection-Reveals-Abrupt-and-Extreme-Climate

Abstract: "The most discernible and devastating impacts of climate change are caused by events with temporary extreme conditions (“extreme events”) or abrupt shifts to a new persistent climate state (“tipping points”). The rapidly growing amount of data from models and observations poses the challenge to reliably detect where, when, why, and how these events occur. This situation calls for data-mining approaches that can detect and diagnose events in an automatic and reproducible way. Here, we apply a new strategy to this task by generalizing the classical machine-vision problem of detecting edges in 2D images to many dimensions (including time). Our edge detector identifies abrupt or extreme climate events in spatiotemporal data, quantifies their abruptness (or extremeness), and provides diagnostics that help one to understand the causes of these shifts. We also publish a comprehensive toolset of code that is documented and free to use. We document the performance of the new edge detector by analyzing several datasets of observations and models. In particular, we apply it to all monthly 2D variables of the RCP8.5 scenario of the Coupled Model Intercomparison Project (CMIP5). More than half of all simulations show abrupt shifts of more than 4 standard deviations on a time scale of 10 years. These shifts are mostly related to the loss of sea ice and permafrost in the Arctic. Our results demonstrate that the edge detector is particularly useful to scan large datasets in an efficient way, for example multimodel or perturbed-physics ensembles. It can thus help to reveal hidden “climate surprises” and to assess the uncertainties of dangerous climate events."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3399 on: June 25, 2020, 12:00:35 PM »
The linked reference indicates that methane photoproduction in the surface waters of the ocean lead to a supersaturation of those waters; which, leads to sustained methane emissions from the global oceans into the atmosphere:

Y. Li et al. (20 June 2020), "The contribution of methane photoproduction to the oceanic methane paradox", Geophysical Research Letters, https://doi.org/10.1029/2020GL088362

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL088362?af=R

Abstract
Although methanogenesis is considered a strictly anaerobic process, oxygen‐replete surface open‐ocean waters are usually supersaturated with methane (CH4), a phenomenon termed the oceanic methane paradox. Here we report that abiotic methane photoproduction from chromophoric dissolved organic matter (CDOM) significantly contributes to this paradox. Methane photoproduction was observed during solar‐simulated irradiations of various waters collected along the land‐ocean continuum. Methane photoproduction rates decreased seaward, whereas its relative production efficiency and the methane‐to‐carbon‐monoxide (CO) photoproduction ratio (ΔCH4/ΔCO) both followed a reversed trend. Remote‐sensing modeling incorporating a ΔCH4/ΔCO–CDOM absorption relationship yielded an annual methane photoproduction of 118 Gg for the global open ocean, accounting for 20‐60% of the open‐ocean methane efflux and being of comparable magnitude to the upper‐ocean methane microbial‐oxidation sink. The photodegradation of CDOM thus plays an important role in maintaining supersaturated methane concentrations in the oxygenated upper ocean and in sustaining oceanic methane emissions to the atmosphere.

Plain Language Summary
Methane is the second most important greenhouse gas after carbon dioxide, and the global ocean is a significant source of it to the atmosphere. In aquatic environments, methane is thought to be exclusively produced by microbes that degrade organic matter in the absence of oxygen. Contradictorily, the oxygen‐rich waters of the surface open ocean are almost always supersaturated with methane, containing higher concentrations than deeper in the water column. This apparent contradiction is often called the oceanic methane paradox. Here, we demonstrate that the degradation of dissolved organic matter by sunlight in the surface ocean represents an important mechanism of methane production that is capable of maintaining the supersaturation of methane in the surface ocean and of sustaining methane emissions to the atmosphere on a global scale. This study thus suggests that the photochemical production of methane is an important contributor to the oceanic methane paradox.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson