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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3450 on: July 06, 2020, 07:54:03 PM »
The linked reference discusses human fingerprints on joint changes in global temperature, rainfall and continental aridity:

Bonfils, C.J.W., Santer, B.D., Fyfe, J.C. et al. Human influence on joint changes in temperature, rainfall and continental aridity. Nat. Clim. Chang. (2020). https://doi.org/10.1038/s41558-020-0821-1

https://www.nature.com/articles/s41558-020-0821-1

Abstract: "Despite the pervasive impact of drought on human and natural systems, the large-scale mechanisms conducive to regional drying remain poorly understood. Here we use a multivariate approach to identify two distinct externally forced fingerprints from multiple ensembles of Earth system model simulations. The leading fingerprint, FM1(x), is characterized by global warming, intensified wet–dry patterns and progressive large-scale continental aridification, largely driven by multidecadal increases in greenhouse gas (GHG) emissions. The second fingerprint, FM2(x), captures a pronounced interhemispheric temperature contrast, associated meridional shifts in the intertropical convergence zone and correlated anomalies in precipitation and aridity over California, the Sahel and India. FM2(x) exhibits nonlinear temporal behaviour: the intertropical convergence zone moves southwards before 1975 in response to increases in hemispherically asymmetric sulfate aerosol emissions, and it shifts northwards after 1975 due to reduced sulfur dioxide emissions and the GHG-induced warming of Northern Hemisphere landmasses. Both fingerprints are statistically identifiable in observations of joint changes in temperature, rainfall and aridity during 1950–2014. We show that the reliable simulation of these changes requires combined forcing by GHGs, direct and indirect effects of aerosols, and large volcanic eruptions. Our results suggest that GHG-induced aridification may be modulated regionally by future reductions in sulfate aerosol emissions."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3451 on: July 07, 2020, 07:02:34 PM »
Per the linked reference & associated article, the earliest that mitigation measures could limit GMSTA increase would be by 2035:

Samset, B.H., Fuglestvedt, J.S. & Lund, M.T. Delayed emergence of a global temperature response after emission mitigation. Nat Commun 11, 3261 (2020). https://doi.org/10.1038/s41467-020-17001-1

https://www.nature.com/articles/s41467-020-17001-1

Abstract: "A major step towards achieving the goals of the Paris agreement would be a measurable change in the evolution of global warming in response to mitigation of anthropogenic emissions. The inertia and internal variability of the climate system, however, will delay the emergence of a discernible response even to strong, sustained mitigation. Here, we investigate when we could expect a significant change in the evolution of global mean surface temperature after strong mitigation of individual climate forcers. Anthropogenic CO2 has the highest potential for a rapidly measurable influence, combined with long term benefits, but the required mitigation is very strong. Black Carbon (BC) mitigation could be rapidly discernible, but has a low net gain in the longer term. Methane mitigation combines rapid effects on surface temperature with long term effects. For other gases or aerosols, even fully removing anthropogenic emissions is unlikely to have a discernible impact before mid-century."

See also:

Title: "There’s no quick fix for climate change"

https://www.theverge.com/21315822/climate-change-global-temperature-study-decades-fix

Extract: "It could take decades before cuts to greenhouse gases actually affect global temperatures, according to a new study. 2035 is probably the earliest that scientists could see a statistically significant change in temperature — and that’s only if humans take dramatic action to combat climate change.

Specifically, 2035 is the year we might expect to see results if we switch from business-as-usual pollution to an ambitious path that limits global warming to under 2 degrees Celsius — the target laid out in the Paris climate agreement. The world isn’t on track to meet that goal, so we might not see the fruits of our labor until even later. That means policymakers need to be ready for the long haul, and we’re all going to need to be patient while we wait for the changes we make now to take effect."
“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 #3452 on: July 07, 2020, 10:17:20 PM »
Per the linked Copernicus article June 2020 was almost tied as the warmest June in the Copernicus record:

Title: "Surface air temperature for June 2020"

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

Extract: "Global temperatures were much above average in June 2020. The month as a whole was:
•   0.53°C warmer than the average June from 1981-2010;
•   less than a marginal 0.01°C cooler than June 2019, the warmest June in this data record;
•   warmer by 0.1°C than June 2016, the third warmest June."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3453 on: July 07, 2020, 11:26:27 PM »
The linked article indicates that it may soon be practicable to determine Antarctic sea ice thickness using two satellites in tandem:

Title: "Esa and Nasa line up satellites to measure Antarctic sea-ice"

https://www.bbc.com/news/science-environment-53326490

Extract: "Authorisation was given on Tuesday for Europe's Cryosat-2 spacecraft to raise its orbit by just under one kilometre.

This will hugely increase the number of coincident observations it can make with the Americans' Icesat-2 mission.

One outcome from this new strategy will be the first ever reliable maps of Antarctic sea-ice thickness.

Currently, the floes in the far south befuddle efforts to measure their vertical dimension.

Heavy snow can pile on top of the floating ice, hiding its true thickness. Indeed, significant loading can even push Antarctic sea-ice under the water.

But researchers believe the different instruments on the two satellites working in tandem can help them tease apart this complexity."
“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
« Reply #3454 on: July 08, 2020, 05:06:15 PM »
The linked reference discusses the extreme Arctic Ocean waves that will occur with continued global warming.  Such extreme waves will also decrease sea ice extent and will act as a positive feedback mechanism for more warming:

Mercé Casas‐Prat, Xiaolan L. Wang. Projections of extreme ocean waves in the Arctic and potential implications for coastal inundation and erosion. Journal of Geophysical Research: Oceans, 2020; DOI: 10.1029/2019JC015745

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JC015745

Abstract
The Arctic Ocean wave climate is undergoing a dramatic change due to the sea ice retreat. This study presents simulations of the Arctic regional wave climate corresponding to the surface winds and sea ice concentrations as simulated by five CMIP5 (Coupled Model Intercomparison Project Phase 5) climate models for the historical (1975‐‐2005) and RCP8.5 scenario future (2081‐‐2100) periods. The annual maximum significant wave height is projected to increase up to 6 m offshore and up to 2‐3 times greater than the corresponding 1979‐‐2005 value along some coastlines, as waves become more exposed to the fall storms there. The connection between the Atlantic Ocean and the Arctic wave climates is projected to strengthen due to increase of swell influence. Changes in the wave direction also seem to indicate a weakening of the Beaufort High illustrated by a counterclockwise rotation of the mean wave direction for extreme conditions in the Western Arctic. The projected changes in wave conditions lead to a general increase of the wave‐driven erosion and inundation potential along the Arctic coastlines. Potentially hazardous extreme wave events are projected to become significantly more frequent and more intense. For example, in the Beaufort coastlines a once‐in‐20 year event under the historical (1979‐‐2005) climate is projected to occur, on average, once every 2‐5 years during 2081‐‐2100. This is a pressing issue as it affects many Arctic coastal communities, as well as existing and emerging Arctic infrastructure and activities, with some of them having already suffered severe wave‐induced damage in the past years.

Plain Language Summary
The Arctic Ocean wave climate is drastically changing with remarkable sea ice retreat. This study presents simulations of historical and future wave climates for the Arctic Ocean. The results show that the largest waves will be significantly higher and longer by the end of the century as the ice‐free season lengthens and waves become more exposed to storms in autumn. Moreover, the Arctic wave climate was projected to be more influenced by ocean waves remotely generated in the North Atlantic, which will be able to propagate to higher latitudes. This could also lead to changes in the typical wave direction patterns in the Arctic. The more energetic waves projected for the future are likely to pose a hazard to the Arctic coastlines, as the extreme wave events that can cause erosion and inundation will be more frequent and intense. This is a pressing issue as it affects many existing Arctic coastal communities and Arctic infrastructure and activities, some of which have already suffered severe damage in the past years.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3455 on: July 08, 2020, 06:08:38 PM »
To my thinking the linked reference suggests that climate sensitivity is relatively high:

Mariano S. Morales et al. (2020), "Six hundred years of South American tree rings reveal an increase in severe hydroclimatic events since mid-20th century", PNAS, https://doi.org/10.1073/pnas.2002411117

https://www.pnas.org/content/early/2020/07/02/2002411117.short?rss=1

Significance
The SADA is an annually-resolved hydroclimate atlas in South America that spans the continent south of 12°S from 1400 to 2000 CE. Based on 286 tree ring records and instrumentally-based estimates of soil moisture, the SADA complements six drought atlases worldwide filling a geographical gap in the Southern Hemisphere. Independently validated with historical records, SADA shows that the frequency of widespread severe droughts and extreme pluvials since the 1960s is unprecedented. Major hydroclimate events expressed in the SADA are associated with strong El Niño Southern Oscillation (ENSO) and Southern Annular Mode (SAM) anomalies. Coupled ENSO-SAM anomalies together with subtropical low-level jet intensification due to increasing greenhouse gas emissions may cause more extreme droughts and pluvials in South America during the 21st century.

Abstract
South American (SA) societies are highly vulnerable to droughts and pluvials, but lack of long-term climate observations severely limits our understanding of the global processes driving climatic variability in the region. The number and quality of SA climate-sensitive tree ring chronologies have significantly increased in recent decades, now providing a robust network of 286 records for characterizing hydroclimate variability since 1400 CE. We combine this network with a self-calibrated Palmer Drought Severity Index (scPDSI) dataset to derive the South American Drought Atlas (SADA) over the continent south of 12°S. The gridded annual reconstruction of austral summer scPDSI is the most spatially complete estimate of SA hydroclimate to date, and well matches past historical dry/wet events. Relating the SADA to the Australia–New Zealand Drought Atlas, sea surface temperatures and atmospheric pressure fields, we determine that the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) are strongly associated with spatially extended droughts and pluvials over the SADA domain during the past several centuries. SADA also exhibits more extended severe droughts and extreme pluvials since the mid-20th century. Extensive droughts are consistent with the observed 20th-century trend toward positive SAM anomalies concomitant with the weakening of midlatitude Westerlies, while low-level moisture transport intensified by global warming has favored extreme rainfall across the subtropics. The SADA thus provides a long-term context for observed hydroclimatic changes and for 21st-century Intergovernmental Panel on Climate Change (IPCC) projections that suggest SA will experience more frequent/severe droughts and rainfall events as a consequence of increasing greenhouse gas emissions.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3456 on: July 08, 2020, 06:19:52 PM »
Freshening of AABW should also work to slow the MOC:

S. Aoki et al. (01 July 2020), "Freshening of Antarctic Bottom Water off Cape Darnley, East Antarctica", Journal of Geophysical Research: Oceans, https://doi.org/10.1029/2020JC016374

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JC016374?af=R

Abstract
Recently, a source of Antarctic Bottom Water (AABW) was identified off Cape Darnley at the eastern end of the Weddell‐Enderby Basin. However, the behavior and long‐term variability of Cape Darnley Bottom Water (CDBW) are not clearly understood. Hydrographic observations from 1974 to 2016 were compared, and a decade‐long bottom temperature record was analyzed to clarify multi‐decadal changes in the CDBW in this region and its downstream influences. In the Cooperation Sea, CDBW spread northwestward with its deepest part reaching to approximately 4900 dbar. CDBW freshening of 0.001–0.003 dec‐1 was revealed. In the Cosmonaut Sea, long‐term AABW warming of approximately 0.01–0.03°C dec‐1 was prominent in the deep basin, while freshening was detected on the upper continental slope. Spatial patterns suggest that an inter‐basin deep transport of excess freshwater is carried by CDBW and fed into the Weddell Gyre, which might act as an abyssal freshwater buffer.

Plain Language Summary
Global oceans' abyss is filled with the cold, dense water fed from the Antarctic coastal margin. The Weddell Sea is the most voluminous supplier of this bottom water. In addition to the well‐known source of the bottom water, new source regions are discovered recently: continental shelf off Cape Darnley, East Antarctica, is one of such regions. Vast parts of the ocean around Antarctica is experiencing freshening for these decades, possibly related to an accelerating ice mass discharge from the Antarctic continent. In contrast, the abyssal Weddell Sea has been known to be warming significantly, acting like a huge heat buffer. Our study shows the newly‐discovered bottom water off Cape Darnley is carrying an increasing amount of freshwater and feeding the excess freshwater into the abyssal Weddell Sea. This suggests that the Weddell Sea experiences changes that originate from a distant, continental source.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3457 on: July 08, 2020, 06:31:00 PM »
Clearly, potential abrupt SLR associated with the AIS is a climate risk factor that needs to be planned for:

Verschuur, J., Le Bars, D., Katsman, C.A. et al. Implications of ambiguity in Antarctic ice sheet dynamics for future coastal erosion estimates: a probabilistic assessment. Climatic Change (2020). https://doi.org/10.1007/s10584-020-02769-4

https://link.springer.com/article/10.1007/s10584-020-02769-4

Abstract: "Sea-level rise (SLR) can amplify the episodic erosion from storms and drive chronic erosion on sandy shorelines, threatening many coastal communities. One of the major uncertainties in SLR projections is the potential rapid disintegration of large fractions of the Antarctic ice sheet (AIS). Quantifying this uncertainty is essential to support sound risk management of coastal areas, although it is neglected in many erosion impact assessments. Here, we use the island of Sint Maarten as a case study to evaluate the impact of AIS uncertainty for future coastal recession. We estimate SLR-induced coastal recession using a probabilistic framework and compare and contrast three cases of AIS dynamics within the range of plausible futures. Results indicate that projections of coastal recession are sensitive to local morphological factors and assumptions made on how AIS dynamics are incorporated into SLR projections and that underestimating the potential rapid mass loss from the AIS can lead to ill-informed coastal adaptation decisions."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3458 on: July 08, 2020, 08:02:46 PM »
The linked reference suggests that the high-end CMIP6 models may have used aerosol feedbacks that were too high.  Of course, if these aerosol feedbacks are decreased in the CMIP7 models than projections of future GMSTA would likely increase:

Flynn, C. M. and Mauritsen, T.: On the climate sensitivity and historical warming evolution in recent coupled model ensembles, Atmos. Chem. Phys., 20, 7829–7842, https://doi.org/10.5194/acp-20-7829-2020, 2020.

https://www.atmos-chem-phys.net/20/7829/2020/

Abstract
The Earth's equilibrium climate sensitivity (ECS) to a doubling of atmospheric CO2, along with the transient climate response (TCR) and greenhouse gas emissions pathways, determines the amount of future warming. Coupled climate models have in the past been important tools to estimate and understand ECS. ECS estimated from Coupled Model Intercomparison Project Phase 5 (CMIP5) models lies between 2.0 and 4.7 K (mean of 3.2 K), whereas in the latest CMIP6 the spread has increased to 1.8–5.5 K (mean of 3.7 K), with 5 out of 25 models exceeding 5 K. It is thus pertinent to understand the causes underlying this shift. Here we compare the CMIP5 and CMIP6 model ensembles and find a systematic shift between CMIP eras to be unexplained as a process of random sampling from modeled forcing and feedback distributions. Instead, shortwave feedbacks shift towards more positive values, in particular over the Southern Ocean, driving the shift towards larger ECS values in many of the models. These results suggest that changes in model treatment of mixed-phase cloud processes and changes to Antarctic sea ice representation are likely causes of the shift towards larger ECS. Somewhat surprisingly, CMIP6 models exhibit less historical warming than CMIP5 models, despite an increase in TCR between CMIP eras (mean TCR increased from 1.7 to 1.9 K). The evolution of the warming suggests, however, that several of the CMIP6 models apply too strong aerosol cooling, resulting in too weak mid-20th century warming compared to the instrumental record.
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Tom_Mazanec

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3459 on: July 08, 2020, 08:11:40 PM »
AbruptSLR, if you are right and they are wrong at some point reality will exceed the projections and force them to admit they were wrong. When do you think this might occur?
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3460 on: July 08, 2020, 08:18:17 PM »
The linked reference discusses insights on how to better quantify future methane emissions from wetlands with continued global warming:

Chang, K.-Y., Riley, W. J., Crill, P. M., Grant, R. F., and Saleska, S. R.: Hysteretic temperature sensitivity of wetland CH4 fluxes explained by substrate availability and microbial activity, Biogeosciences Discuss., https://doi.org/10.5194/bg-2020-177, in review, 2020.

https://www.biogeosciences-discuss.net/bg-2020-177/

Abstract. Methane (CH4) emissions from wetlands are likely increasing and important in global climate change assessments. However, contemporary terrestrial biogeochemical model predictions of CH4 emissions are very uncertain, at least in part due to prescribed temperature sensitivity of CH4 production and emission. While statistically consistent apparent CH4 emission temperature dependencies have been inferred from meta-analyses across microbial to ecosystem scales, year-round ecosystem-scale observations have contradicted that finding. Using flux observations and mechanistic modeling in two heavily studied high-latitude research sites (Stordalen, Sweden, and Utqiaġvik, Alaska, USA), we show here that substrate-mediated hysteretic microbial and abiotic interactions lead to intra-seasonally varying temperature sensitivity of CH4 production and emission. We find that seasonally varying substrate availability drives lower and higher modeled methanogen biomass and activity, and thereby CH4 production, during the earlier and later periods of the thawed season, respectively. Our findings demonstrate the uncertainty of inferring CH4 emission or production from temperature alone, and highlight the need to represent microbial and abiotic interactions in wetland biogeochemical models.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3461 on: July 08, 2020, 08:19:24 PM »
AbruptSLR, if you are right and they are wrong at some point reality will exceed the projections and force them to admit they were wrong. When do you think this might occur?

I think that a lot of things will become clearer in the 2030 to 2035 timeframe.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3462 on: July 08, 2020, 08:39:14 PM »
Per Hausfather it is still likely that 2020 will be the warmest year on record.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3463 on: July 08, 2020, 11:59:37 PM »
For those who are interested I provide the following link to a July 7, 2020 virtual seminar on ECS organized by Andrew Dessler (see the attached agenda)

Title: "ECS Virtual Seminar 2"

https://www.youtube.com/watch?v=_98ZnqB6yL0&feature=youtu.be

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3464 on: July 09, 2020, 02:43:12 AM »
ShortBrutishNasty asked me what the US Army Corps of Engineers is planning to do to defend Miami from SLR.  Therefore, I provide the following:

Title: "A $4.6 Billion Plan To Storm-Proof Miami"

https://www.npr.org/2020/06/13/875725714/a-4-6-billion-plan-to-storm-proof-miami

Extract: "Thirteen-foot-high floodwalls could line part of Miami's waterfront, under a proposed Army Corps of Engineers plan being developed to protect the area from storm surge. The $4.6 billion plan is one of several drafted by the Corps of Engineers to protect coastal areas in the U.S, which face increased flood risks stoked by climate change. Similar projects are already underway in Norfolk, VA and Charleston, SC.

The plan for Miami-Dade County, which is open for public comment, is intended to protect the 2.8 million people who live there from coastal flooding and storm surge during tropical storms and hurricanes. Many are concerned that the system of floodwalls, pumps and surge barriers doesn't directly address a threat many in South Florida are already dealing with more frequently than storms: rising sea levels. Chronic flooding is a problem for some neighborhoods in Miami-Dade County during heavy rain events and seasonal king tides.
...
The Corps of Engineers plan calls for storm surge gates to be installed on three waterways that open onto Biscayne Bay, including the Miami River. That's a commercially important waterway, with cargo terminals and repair facilities.

Chief Resilience Officer for Miami-Dade County Jim Murley says: "You have navigation issues, we have drainage issues and water quality issues, all of which have to be factored into the ultimate design of any kind of gate."

The plan also calls for a series of pumps and floodwalls along Miami's waterfront. North of downtown, the floodwalls would be anywhere from one foot to 13 feet high, depending on the location. From the Miami River—in the heart of downtown—stretching south along the shoreline, a storm surge barrier as high as 36 feet would rise from the floor of Biscayne Bay.

The project manager for the Corps of Engineers, Holly Carpenter, says exact dimensions and design of the surge barrier haven't yet been determined. "It's definitely at a conceptual level," she says. "We're concerned more about the feasibility of the type of measures recommended.""

See also:

Title: "Miami-Dade Back Bay Coastal Storm Risk Management Feasibility Study"

https://www.saj.usace.army.mil/MiamiDadeBackBayCSRMFeasibilityStudy/

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3465 on: July 09, 2020, 06:49:15 AM »
Re: "It's definitely at a conceptual level,"

I think the concept needs to expand to include massive retreat.

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3466 on: July 09, 2020, 09:06:17 AM »
The Miami SLR mitigation effort with building walls will generate a lot of CO₂ emissions.
Miami is build on porous limestone, if I remember correctly, so I think the water will come up behind the walls and therefore render the mitigation effort useless apart from exceptional storm surges. Massive retreat seems inevitable.
Am I correct with this line of thinking?
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3467 on: July 09, 2020, 01:37:26 PM »
nanning, IIRC salt water is already getting into the Miami ground water, so you are probably right.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3468 on: July 09, 2020, 04:02:39 PM »
The Miami SLR mitigation effort with building walls will generate a lot of CO₂ emissions.
Miami is build on porous limestone, if I remember correctly, so I think the water will come up behind the walls and therefore render the mitigation effort useless apart from exceptional storm surges. Massive retreat seems inevitable.
Am I correct with this line of thinking?
Yes you are correct.
With rising sea levels more pumping is required to keep the roads clear from king floods which appear slightly more often every year. But pumping out the water will slowly refill the voids in the limestone from below, accompanied by a replacement of fresh ground water depots beneath Miami and surroundings by brackish saltier water.
It is too late just to be concerned about Climate Change

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3469 on: July 09, 2020, 04:19:04 PM »
The Miami SLR mitigation effort with building walls will generate a lot of CO₂ emissions.
Miami is build on porous limestone, if I remember correctly, so I think the water will come up behind the walls and therefore render the mitigation effort useless apart from exceptional storm surges. Massive retreat seems inevitable.
Am I correct with this line of thinking?

I believe that the Corps is proposing to inject/pump freshwater into the porous limestone in order create an underground hydraulic head to limit saltwater from mixing with the local groundwater; however, I do not believe that this method will work for high levels of SLR.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3470 on: July 09, 2020, 04:39:10 PM »
If one considers not only CO2-equivalent but also ice-climate (including freshwater hosing) feedback, then it is plausible that by the end of this century that we could (collectively) be in equable climatic conditions comparable to the Early Eocene as discussed in the linked reference:

Jiang Zhu et al. (18 Sep 2019), "Simulation of Eocene extreme warmth and high climate sensitivity through cloud feedbacks", Science Advances, Vol. 5, no. 9, eaax1874, DOI: 10.1126/sciadv.aax1874

https://advances.sciencemag.org/content/5/9/eaax1874

Abstract: "The Early Eocene, a period of elevated atmospheric CO2 (>1000 ppmv), is considered an analog for future climate. Previous modeling attempts have been unable to reproduce major features of Eocene climate indicated by proxy data without substantial modification to the model physics. Here, we present simulations using a state-of-the-art climate model forced by proxy-estimated CO2 levels that capture the extreme surface warmth and reduced latitudinal temperature gradient of the Early Eocene and the warming of the Paleocene-Eocene Thermal Maximum. Our simulations exhibit increasing equilibrium climate sensitivity with warming and suggest an Eocene sensitivity of more than 6.6°C, much greater than the present-day value (4.2°C). This higher climate sensitivity is mainly attributable to the shortwave cloud feedback, which is linked primarily to cloud microphysical processes. Our findings highlight the role of small-scale cloud processes in determining large-scale climate changes and suggest a potential increase in climate sensitivity with future warming."

In a number of my posts in this thread I have cited a number of different scenarios that could lead to 'Hothouse Earth' conditions in the next century (see the quoted post).  Generally, I get the feeling that many readers consider such scenarios as extremely long-tail events that they can safely ignore.  However, it is possible that we have already crossed the trigger point for a chain-reaction of freshwater perturbations that might guarantee 'Hothouse Earth' conditions in the next century even if we collectively start cutting back significantly on GHG emission (say to SSP 1).  As I recently noted, both a release of relatively freshwater from the Beaufort Gyre into the North Atlantic, and the currently low levels of Arctic Sea Ice Extent, could serve to abruptly increase the magnitude and frequency of intense El Nino events; which could trigger an MICI-type of collapse of the WAIS (via telecommunication of Tropical Pacific energy to West Antarctica); which could trigger an abrupt acceleration of ice mass loss from marine terminating glaciers in Greenland (via the bipolar seesaw mechanism); which collectively might slow the MOC sufficiently this century to lead to a mean 5C increase in SSTA in the Tropical Oceans by early next century; which might be sufficient to flip the NH into an equable atmospheric pattern (see the first three attached images).

Tapio Schneider , Colleen M. Kaul and Kyle G. Pressel (2019), "Possible climate transitions from breakup of stratocumulus decks under greenhouse warming", Nature Geoscience, https://doi.org/10.1038/s41561-019-0310-1

https://www.nature.com/articles/s41561-019-0310-1

Abstract: "Stratocumulus clouds cover 20% of the low-latitude oceans and are especially prevalent in the subtropics. They cool the Earth by shading large portions of its surface from sunlight. However, as their dynamical scales are too small to be resolvable in global climate models, predictions of their response to greenhouse warming have remained uncertain. Here we report how stratocumulus decks respond to greenhouse warming in large-eddy simulations that explicitly resolve cloud dynamics in a representative subtropical region. In the simulations, stratocumulus decks become unstable and break up into scattered clouds when CO2 levels rise above 1,200 ppm. In addition to the warming from rising CO2 levels, this instability triggers a surface warming of about 8 K globally and 10 K in the subtropics. Once the stratocumulus decks have broken up, they only re-form once CO2 concentrations drop substantially below the level at which the instability first occurred. Climate transitions that arise from this instability may have contributed importantly to hothouse climates and abrupt climate changes in the geological past. Such transitions to a much warmer climate may also occur in the future if CO2 levels continue to rise."

However, Romps (2020) points out that once the CO2 levels match equable climate conditions (such as due to carbon cycle feedbacks such as occurred during the Eocene/PETM), where global mean surface temperatures are near 300K, that there is a risk that a perturbation (such as a rapid release of methane from high-latitude methane hydrate decomposition due to the equable climate conditions) could rapidly increase ECS from the 6.6C cited by Zhu et al. (2019) up to the much higher values shown in the fourth attached image.

David M. Romps (2020), "Climate Sensitivity and the Direct Effect of Carbon Dioxide in a Limited-Area Cloud-Resolving Model", J. Climate, 33 (9): 3413–3429, https://doi.org/10.1175/JCLI-D-19-0682.1

https://journals.ametsoc.org/jcli/article/33/9/3413/344997/Climate-Sensitivity-and-the-Direct-Effect-of

Abstract
Even in a small domain, it can be prohibitively expensive to run cloud-resolving greenhouse gas warming experiments due to the long equilibration time. Here, a technique is introduced that reduces the computational cost of these experiments by an order of magnitude: instead of fixing the carbon dioxide concentration and equilibrating the sea surface temperature (SST), this technique fixes the SST and equilibrates the carbon dioxide concentration. Using this approach in a cloud-resolving model of radiative–convective equilibrium (RCE), the equilibrated SST is obtained as a continuous function of carbon dioxide concentrations spanning 1 ppmv to nearly 10 000 ppmv, revealing a dramatic increase in equilibrium climate sensitivity (ECS) at higher temperatures. This increase in ECS is due to both an increase in forcing and a decrease in the feedback parameter. In addition, the technique is used to obtain the direct effects of carbon dioxide (i.e., the rapid adjustments) over a wide range of SSTs. Overall, the direct effect of carbon dioxide offsets a quarter of the increase in precipitation from warming, reduces the shallow cloud fraction by a small amount, and has no impact on convective available potential energy (CAPE).
« Last Edit: July 09, 2020, 05:19:57 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3471 on: July 09, 2020, 04:46:51 PM »
The linked reference (open access in the ncbi link) indicates that a pre-industrial GMSTA baseline near 1750 is likely appreciably lower then with a late-19th century baseline.  If so, this clearly indicates that climate sensitivity is likely higher than assumed by consensus climate science:

Andrew P. Schurer, Michael E. Mann, Ed Hawkins, Simon F. B. Tett, and Gabriele C. Hegerl (2017), "Importance of the Pre-Industrial Baseline in Determining the Likelihood of Exceeding the Paris Limits", Nature Climate Change, 7 (8), pp 563-567, doi: 10.1038/nclimate3345

https://www.nature.com/articles/nclimate3345
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5544117/

Abstract
During the Paris conference in 2015, nations of the world strengthened the United Nations Framework Convention on Climate Change by agreeing to holding ‘the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C’ (ref. 1). However, ‘pre-industrial’ was not defined. Here we investigate the implications of different choices of the pre-industrial baseline on the likelihood of exceeding these two temperature thresholds. We find that for the strongest mitigation scenario RCP2.6 and a medium scenario RCP4.5, the probability of exceeding the thresholds and timing of exceedance is highly dependent on the pre-industrial baseline; for example, the probability of crossing 1.5 °C by the end of the century under RCP2.6 varies from 61% to 88% depending on how the baseline is defined. In contrast, in the scenario with no mitigation, RCP8.5, both thresholds will almost certainly be exceeded by the middle of the century with the definition of the pre-industrial baseline of less importance. Allowable carbon emissions for threshold stabilization are similarly highly dependent on the pre-industrial baseline. For stabilization at 2 °C, allowable emissions decrease by as much as 40% when earlier than nineteenth-century climates are considered as a baseline.

Extract: "Despite remaining uncertainties there are at least two robust implications of our findings. Firstly, mitigation targets based on the use of a late-19th century baseline are probably overly optimistic and potentially substantially underestimate the reductions in carbon emissions necessary to avoid 1.5°C or 2°C warming of the planet relative to pre-industrial. Secondly, while pre-industrial temperature remains poorly defined, a range of different answers can be calculated for the estimated likelihood of global temperatures reaching certain temperature values. We would therefore recommend that a consensus be reached as to what is meant by pre-industrial temperatures to reduce the chance of conclusions which appear contradictory, being reached by different studies and to allow for a more clearly defined framework for policymakers and stakeholders."
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kassy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3472 on: July 09, 2020, 04:55:48 PM »
'Hothouse Earth' conditions in the next century

It is partly the time frame. It is rather abstract and many people figure that someone will solve it somewhere along the way. The amount of damage locked in is already staggering. The waters encroaching on Florida now are the result of what we did years ago , similar with the waters lapping at Antarctica´s underbelly and the acidification to come.

Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3473 on: July 09, 2020, 05:34:51 PM »
'Hothouse Earth' conditions in the next century

It is partly the time frame. It is rather abstract and many people figure that someone will solve it somewhere along the way. The amount of damage locked in is already staggering. The waters encroaching on Florida now are the result of what we did years ago , similar with the waters lapping at Antarctica´s underbelly and the acidification to come.

kassy,

The point that you make that many/most people discount long-tail future risks actually means that those risks are actually greater than if people took those risks more seriously.  Thus, while Romps (2020) risks of extremely high values of ECS (well over 6.6C) after some scenario of a chain of tipping points (say a release of freshwater hosing from the Beaufort Gyre slowing the MOC leading to an abrupt collapse of the WAIS which might drive tropical ocean SSTA above 5C that might trigger an equable climate) that could lead to an equable climate next century and then some perturbation (say an abrupt release of methane from Arctic methane hydrates) could driving ECS well above 6.6C due to CO2 concentrations say by 2300.  Thus, there is at least a reason for researchers like Romps to continue their research in the global mean temperature range from 300K to 325K.

Best,
ASLR
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3474 on: July 09, 2020, 06:27:37 PM »
The linked pdf (& associate other linked information) helps to explain why the observed extratropical (high latitude) shift in stratocumulus to cumulus clouds is leading to a positive cloud feedback that is ignored by CMIP5 projects but is captured by high-end CMIP6 projections.  This physical explanation helps to provide more confidence in the relatively high climate sensitivity values projected by the high-end CMIP6 models.  Finally, I note that if E3SMv1 is roughly correct that TCR is about 2.93C and ECS is about 5.3C then the risk of a chain of freshwater hosing events tipping points (domino effect) leading to an equable climate is higher than currently assumed by consensus climate science.

Title: "Investigating the role of stratocumulus to cumulus transitions in the extratropical cloud optical depth feedback"; October 2019.

https://www.giss.nasa.gov/meetings/cfmip2019/s8/4_ivy_tan.pdf

Extract: "Preliminary results suggest that shifts from Sc to Cu clouds constitute a positive cloud optical depth feedback over the Southern Ocean, but the shifts are in the opposite direction in the 12-year period examined because the mid-latitude surface temperature cooled."

See also:

Title: "CFMIP 2019 Meeting on Clouds, Precipitation, Circulation, and Climate Sensitivity"

https://www.giss.nasa.gov/meetings/cfmip2019/agenda.html

See also:

Ivy Tan & Trude Storelvmo (25 February 2019), "Evidence of Strong Contributions From Mixed‐Phase Clouds to Arctic Climate Change", Geophysical Research Letters
Volume 46, Issue 5, https://doi.org/10.1029/2018GL081871

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL081871

Abstract
Underestimation of the proportion of supercooled liquid in mixed‐phase clouds in climate models has called into question its impact on Arctic climate change. We show that correcting for this bias in the CESM model can either enhance or reduce Arctic amplification depending on the microphysical characteristics of the clouds as a corollary to the cloud phase feedback. Replacement of ice with liquid in the cloud phase feedback results in more downward longwave radiation, which is effectively trapped as heat at the surface in the Arctic due to its unique stable stratification conditions, and this ultimately leads to a more positive lapse rate feedback. The larger the ice particles are to begin with, the stronger Arctic amplification becomes due to the lower precipitation efficiency of liquid droplets compared to ice crystals. Our results emphasize the importance of realistic representations of microphysical processes in mixed‐phase clouds, particularly in the Arctic.

Plain Language Summary
Warming of Earth's Arctic at a faster pace relative to the rest of the globe is referred to as “Arctic amplification.” Mixed‐phase clouds consisting of both liquid droplets and ice crystals are ubiquitous in Earth's Arctic. The ratio of liquid to ice in mixed‐phase clouds is typically underestimated in climate models and has been shown to lead to underestimates in global warming by underestimating the strength of the “cloud phase feedback.” Replacement of cloud ice with liquid as Earth warms results in more reflected sunlight to space. Therefore, a low cloud liquid bias results in a global overestimate of the negative cloud phase feedback. In this study, we find that correcting this low bias can simultaneously reduce Arctic amplification by reducing longwave radiation to the surface that is trapped as heat in the Arctic. However, the effect is highly sensitive to the size of the cloud particles. Ice particles typically precipitate faster than liquid droplets so replacement of larger ice particles with liquid results in longer‐lived clouds that radiate more longwave radiation to the surface, which ultimately leads to enhanced Arctic amplification. The results of this study emphasize the importance of realistic representations of mixed‐phase cloud microphysics in climate models.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3475 on: July 09, 2020, 06:52:22 PM »
The linked WMO report indicates about a 20% chance that one year in the next five years will have a GMSTA (with a late 19th century baseline) of at least 1.5C:

Title: "Global Annual to Decadal Climate Update Target years: 2020 and 2020-2024"

https://hadleyserver.metoffice.gov.uk/wmolc/WMO_GADCU_2019.pdf

Extract: "
• Annual global temperature is likely to be at least 1°C warmer than preindustrial levels (defined as the 1850-1900 average) in each of the coming 5 years and is very likely to be within the range 0.91 – 1.59°C

• It is unlikely (~20% chance) that one of the next 5 years will be at least 1.5°C warmer than preindustrial levels, but the chance is increasing with time

• It is likely (~70% chance) that one or more months during the next 5 years will be at least 1.5°C warmer than preindustrial levels"

See also:

Title: "The Lead Centre for Annual-to-Decadal Climate Prediction collects and provides hindcasts, forecasts and verification data from a number of contributing centres worldwide."

https://hadleyserver.metoffice.gov.uk/wmolc/

See also:

Title: "New climate predictions assess global temperatures in coming five years"

https://public.wmo.int/en/media/press-release/new-climate-predictions-assess-global-temperatures-coming-five-years

Extract: "The annual mean global temperature is likely to be at least 1° Celsius above pre-industrial levels (1850-1900) in each of the coming five years (2020-2024) and there is a 20% chance that it will exceed 1.5°C in at least one year, according to new climate predictions issued by the World Meteorological Organization (WMO)."

See also:

https://twitter.com/WMO
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Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3476 on: July 09, 2020, 08:30:55 PM »
The Miami SLR mitigation effort with building walls will generate a lot of CO₂ emissions.
Miami is build on porous limestone, if I remember correctly, so I think the water will come up behind the walls and therefore render the mitigation effort useless apart from exceptional storm surges. Massive retreat seems inevitable.
Am I correct with this line of thinking?

I believe that the Corps is proposing to inject/pump freshwater into the porous limestone in order create an underground hydraulic head to limit saltwater from mixing with the local groundwater; however, I do not believe that this method will work for high levels of SLR.

It wont work for low levels of SLR either.  As mentioned upthread, the ground is porous limestone and water already comes up from it during the highest high tides of the year.  There's no way to cap every pore with concrete. 


AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3477 on: July 09, 2020, 09:55:56 PM »
The Miami SLR mitigation effort with building walls will generate a lot of CO₂ emissions.
Miami is build on porous limestone, if I remember correctly, so I think the water will come up behind the walls and therefore render the mitigation effort useless apart from exceptional storm surges. Massive retreat seems inevitable.
Am I correct with this line of thinking?

I believe that the Corps is proposing to inject/pump freshwater into the porous limestone in order create an underground hydraulic head to limit saltwater from mixing with the local groundwater; however, I do not believe that this method will work for high levels of SLR.

It wont work for low levels of SLR either.  As mentioned upthread, the ground is porous limestone and water already comes up from it during the highest high tides of the year.  There's no way to cap every pore with concrete.

You raise a valid concern (for low levels of SLR or even just high tides), and while I do not have sufficient time to investigate the Miami situation; I suspect that the USACE (US Army Corps of Engineers) is planning on directing leakage from the porous limestone into multiple catchment basins that would then be pumped into the bay.  While it sound inefficient to pump freshwater into the limestone and then to collect and pump the leakage into the bay; political pressure makes it impossible to plan for the retreat that sidd is recommending.
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FishOutofWater

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3478 on: July 09, 2020, 10:44:17 PM »
The ACE plan won't keep the water out of Miami but it will keep the money flowing to the ACE. It's a perpetual job machine for the ACE. I suggest that they get the situation in New Orleans under better control before starting another huge project that is likely to fail.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3479 on: July 10, 2020, 12:29:33 AM »
The ACE plan won't keep the water out of Miami but it will keep the money flowing to the ACE. It's a perpetual job machine for the ACE. I suggest that they get the situation in New Orleans under better control before starting another huge project that is likely to fail.

While I concur that the USACE's efforts may be a waste of money in the long-term; nevertheless, in the short-term political pressure will turn climate change into a gift that keeps on giving to the USACE not only in Florida and Louisiana, but also in: Maine, Mass., Conn., R.I., New York, New Jersey, Maryland, Delaware, D.C., Virginia, N.C., S.C., Georgia, P.R., Alabama, Miss., Texas, California, Oregon, Washington State; Hawaii and Alaska.
« Last Edit: July 10, 2020, 03:59:36 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3480 on: July 10, 2020, 06:23:55 PM »
Note that in the attached image from the linked article on the WMO's 5-year projection for GMSTA that 'pre-industrial' is taken to have a baseline of 1850-1900; while using a baseline of 1720 could increase the projected 'pre-industrial' GMSTA values by up to 0.2C.

Title: "Guest post: Global warming edges closer to Paris Agreement 1.5C limit"

https://www.carbonbrief.org/guest-post-global-warming-edges-closer-to-paris-agreement-1-5c-limit

Extract: "The latest forecast (pdf) from the World Meteorological Organization (WMO) suggests that over the next five years there is a 24% chance of the global average temperature exceeding 1.5C above pre-industrial levels for at least one year.

Most scientific studies consider modern warming to be relative to the average from 1850 to 1900 – and the 2018 special report on 1.5C by the Intergovernmental Panel on Climate Change (IPCC) and the WMO forecast both use this.

However, this is not the “true” pre-industrial climate because substantial fossil fuel burning began a century earlier at the start of the Industrial Revolution. The earlier date has not typically been used in climate science since there is not enough coverage of weather data before 1850 to allow a confident estimate for an earlier baseline – and it was originally considered that the difference would be small.

Recent work shows that the difference is, indeed, fairly small and still uncertain – possibly up to 0.2C. But this is enough to make a difference of up to about a decade to the year at which 1.5C could be considered to be breached.

Caption: "Observed and predicted changes in annual global mean temperature. The blue band shows the WMO forecast of possible annual changes in the next five years, starting from current data, with darker blue showing higher probabilities. The green bands show tests of the forecast method against observed data, which are shown in black. The grey band shows the range of annual temperatures from the CMIP5 model projections that do not start from current data. Numbers on the left show the changes relative to the average of 1981-2010, and on the right, changes relative to “pre-industrial” (1850-1900). Both the CMIP5 projections and the WMO forecast use anthropogenic forcings from the RCP4.5 scenario. For further details see the WMO 2020-2024 forecast. Credit: Leon Hermanson"
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3481 on: July 10, 2020, 07:00:26 PM »
The linked (open access) reference describes a positive feedback for reducing Arctic Sea Ice in the Eurasian Basin of the Arctic Ocean (>70oE) associated with a weakening of the cold halocline and associated increased oceanic heat flux from warm Atlantic Water to the surface mixed layer.  Such a feedback could contribute to a near future (in coming decades) albedo flip due to reduce Arctic Sea Ice (particularly in association with a future potential Beaufort Gyre freshwater hosing event):

Igor V. Polyakov et al. (2020), "Weakening of cold halocline layer exposes sea ice to oceanic heat in the eastern Arctic Ocean", J. Climate, https://doi.org/10.1175/JCLI-D-19-0976.1

https://journals.ametsoc.org/jcli/article/doi/10.1175/JCLI-D-19-0976.1/353233/Weakening-of-cold-halocline-layer-exposes-sea-ice

Abstract: "A 15-year duration record of mooring observations from the eastern (>70°E) Eurasian Basin (EB) of the Arctic Ocean is used to show and quantify the recently increased oceanic heat flux from intermediate-depth (∼150-900 m) warm Atlantic Water (AW) to the surface mixed layer (SML) and sea ice. The upward release of AW heat is regulated by the stability of the overlying halocline, which we show has weakened substantially in recent years. Shoaling of the AW has also contributed, with observations in winter 2017-2018 showing AW at only 80 m depth, just below the wintertime surface mixed layer (SML), the shallowest in our mooring records. The weakening of the halocline for several months at this time implies that AW heat was linked to winter convection associated with brine rejection during sea ice formation. This resulted in a substantial increase of upward oceanic heat flux during the winter season, from an average of 3-4 W/m2 in 2007-2008 to >10 W/m2 in 2016-2018. This seasonal AW heat loss in the eastern EB is equivalent to a more than a two-fold reduction of winter ice growth. These changes imply a positive feedback as reduced sea ice cover permits increased mixing, augmenting the summer-dominated ice-albedo feedback."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3482 on: July 10, 2020, 08:16:16 PM »
The research on Soil Organic Carbon, SOC, cited in the linked article and associated reference will be incorporated into models like E3SMv2; which will allow such advanced climate models to account for topographical and environmental controllers of associated GHG emission/sequestering feedbacks that are currently ignored by climate models (including those in CMIP6).  While this may seem esoteric, I am concerned that potential freshwater hosing events in the coming decades (e.g. from the Beaufort Gyre, from the WAIS and from the GIS) many abruptly increase tropical ocean SSTAs (due to a slowing of the MOC); which may warm GMSTA sufficiently to release substantial amounts of GHGs, from the SOC, into the atmosphere; which could (in coming centuries) contribute to sustained 'Hot House' global conditions (resulting from temporary freshwater hosing events):

Title: "Argonne soil carbon research reduces uncertainty in predicting climate change impacts"

https://www.eurekalert.org/pub_releases/2020-07/dnl-asc070920.php

Extract: "The scaling algorithms that he and his collaborators created as part of the research are important to Earth system models, like the DOE's Energy Exascale Earth System Model, in addition to predicting changes in climate more accurately.

Scaling, Mishra noted, is an issue which has traditionally been ignored in biogeochemical/natural sciences, where it was believed that properties or processes associated with one spatial scale can be applied at both smaller or larger scales. In reality, however this is not the case.

Current Earth system models, which are used to predict the future global carbon climate feedbacks and associated climate changes, operate at coarse spatial scales (50-100 km) and are currently unable to represent environmental controllers and their effect on soil organic carbon in a manner consistent with field observations."

See also:

K.Adhikari aet al. (2020), "Importance and strength of environmental controllers of soil organic carbon changes with scale", Geoderma, https://doi.org/10.1016/j.geoderma.2020.114472

https://www.sciencedirect.com/science/article/pii/S0016706120305139

Abstract
Spatial heterogeneity in environmental factors on the land surface moderates exchanges of water, energy, and greenhouse gases between the land and the atmosphere. However, appropriately representing this heterogeneity in earth system models remains a critical scientific challenge. We used a large dataset of environmental factors (n = 31) representing soil-forming factors, field observations of soil organic carbon (SOC) (n = 6213), and a machine-learning algorithm (Cubist) to analyze the scaling behavior of SOC across the conterminous United States. We found that various environmental factors are significant predictors of SOC stocks at different spatial scales. Out of the 31 environmental factors we investigated, only 13 were significant predictors of SOC stocks at spatial scales ranging from 100 m to 50 km. Overall, topographic variables had higher influence at finer scales, whereas climatic variables were more important at coarser scales. The model performance worsened with increasing scale or the spatial resolution of prediction (R2 = 0.38–0.65). The strength of environmental controls (median regression coefficient) on SOC weakened with scale, and we represented them using mathematical functions (R2 = 0.38–0.98). Both the mean and variance of SOC stocks decreased linearly with increasing the scale in soils of the conterminous United States. Fitted linear functions accounted for 81% and 82% of the variability in the mean and variance of SOC, respectively. We also found linear relationships among mean and high-order moments of SOC (R2 = 0.51–0.97). Improved understanding of the scaling behavior of SOC stocks and their environmental controllers can improve earth system model benchmarking and may eventually improve representation of the spatial heterogeneity of land surface biogeochemistry.

“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
« Reply #3483 on: July 11, 2020, 05:48:06 PM »
This post is just a general comment about the public perception of long-tail climate risk w.r.t. the fact that all of the CMIP radiative forcing scenarios are dominated by GHG emissions/concentrations/pathways and largely ignore freshwater hosing events.

First, paleo freshwater hosing events (like mega-lake drainage, or abrupt marine glacier/ice sheet collapses) tend to only produce temporary impacts on TCR; a fact to which many consensus climate scientists point at to justify their largely ignoring freshwater hosing events in their projections but instead use high GHG emissions scenarios as a substitute to address their perception of long-tail risks.  Unfortunately, the current rate of anthropogenic global warming is so high that the temporary impacts of freshwater hosing on TCR (as indicated by E3SMv1 can push TCR up to at least 2.93C) will likely not have dissipated before other climate tipping points are triggered this century.

Second, two major ways that freshwater hosing temporarily increase TCR (for multiple decades) are: a) a slowdown of the MOC that rapidly increases tropical ocean SSTs that rapidly makes net cloud feedback more positive; and b) shifts of stratocumulus to cumulus clouds over the Southern Ocean that also makes cloud feedback more positive.

Third, consensus climate scientists frequently complain that freshwater hosing events are difficult to model in the global models and that they do not have sufficient budgets to evaluate such events.  However, Romps (2020) shows that global climate models run approximately 30-times faster when driven by changes in SST (sea surface temperature).  Thus, as numerous regional models have already been run with freshwater hosing events that provide clear projections of changes in SST due to such hosing events; it should be practicable for CMIP7 to adopt at least one high-end hybrid forcing scenario that include both changes in GHG emissions with time and periodic abrupt changes in SSTs associated with potential freshwater hosing events like a freshwater release from the Beaufort Gyre and/or from MICI-type of partial collapse of the WAIS in coming decades.

If consensus climate scientists were to adopt such a high-end hybrid forcing scenario including freshwater hosing events; the public perception of the actual climate risk from 'long-term' events would likely change abruptly.
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Tom_Mazanec

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3484 on: July 11, 2020, 06:02:50 PM »
Quote
If consensus climate scientists were to adopt such a high-end hybrid forcing scenario including freshwater hosing events; the public perception of the actual climate risk from 'long-term' events would likely change abruptly.
I imagine the public would say this is a conspiracy of scientists to hoax the public to get more money and power.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3485 on: July 11, 2020, 09:59:15 PM »
Quote
If consensus climate scientists were to adopt such a high-end hybrid forcing scenario including freshwater hosing events; the public perception of the actual climate risk from 'long-term' events would likely change abruptly.
I imagine the public would say this is a conspiracy of scientists to hoax the public to get more money and power.

Which is exactly what many people are already saying about RCP8.5 & SSP5.  So if these consensus scientists are already being criticized for including a high-end case they might as well include a high-end case that better accounts for the risks represented by possible/probable freshwater hosing events (just don't call it a hybrid).
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3486 on: July 12, 2020, 04:01:02 PM »
...

Coletti, A. J., DeConto, R. M., Brigham-Grette, J., and Melles, M.: A GCM comparison of Pleistocene super-interglacial periods in relation to Lake El'gygytgyn, NE Arctic Russia, Clim. Past, 11, 979-989, doi:10.5194/cp-11-979-2015, 2015.

http://www.clim-past.net/11/979/2015/cp-11-979-2015.pdf
http://www.clim-past.net/11/979/2015/cp-11-979-2015.html

Abstract: "Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stages (MISs) 1 (9 ka), 5e (127 ka), 11c (409 ka) and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the mean temperature of the warmest month (MTWM) indicate conditions up to 0.4, 2.1, 0.5 and 3.1 °C warmer than today during MIS 1, 5e, 11c and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer (JJA) orbital forcing, the extraordinary warmth of MIS 11c compared to the other interglacials in the Lake El'gygytgyn temperature proxy reconstructions remains difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice and circum-Arctic land ice feedbacks on the modeled climate of the Beringian interior. Simulations accounting for climate–vegetation–land-surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on northeast Asian temperature during the warmth of stages 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic Ocean does have some effect on Lake El'gygytgyn's regional climate, but the exceptional warmth of MIS l1c remains enigmatic compared to the modest orbital and greenhouse gas forcing during that interglacial."

Extract: "The timing of significant warming in the circum-Arctic can be linked to major deglaciation events in Antarctica, demonstrating possible interhemispheric linkages between the Arctic and Antarctic climate on glacial–interglacial timescales, which have yet to be explained."

...

This is a reminder that in Beltan et al (2020) the authors warn that a GMSTA of 1.5oC is sufficient to trigger a rapid retreat of the WAIS.  Furthermore, the authors refer to a 5 oC increase of the surface water temperature within the study area in the Antarctic coastal waters which is associated with various factors including stratification of regional waters (due to freshening), warming of the surface water from the atmosphere and local upwelling of warm CDW.  Furthermore, the first attached image (Fig 5) shows that within 1,000 years of the majority of local ice mass loss has occurred; while the second image (Fig 6) shows the two step paleo warming process (& I note that in the modern world we are currently past Step 1).  Also, I note that the model that Beltran et al. (2020) could simulate MISI behavior but not MICI behavior thus I include the third attached image from Pollard and DeConto showing that using one version of an MICI model projected similar ice mass loss from Antarctica by 2170 that took the Beltran et al (2020) model approximately 1000 years to achieve.

Catherine Beltran et al. (2020), "Southern Ocean temperature records and ice-sheet models demonstrate rapid Antarctic ice sheet retreat under low atmospheric CO2 during Marine Isotope Stage 31", Quaternary Science Reviews, Volume 228, 106069, https://doi.org/10.1016/j.quascirev.2019.106069

https://www.sciencedirect.com/science/article/abs/pii/S0277379119306122

Highlights

Quantification of the Southern Ocean warming during MIS31 using molecular temperature reconstructions at high latitudes.

Sustained surface Southern Ocean warming & collapse of the sub-Antarctic ocean fronts under low atmospheric CO2 conditions.

Use of sea surface temperature data to test scenarios for the AIS retreat using coupled ice-sheet/ice-shelf model.

Two steps WAIS retreat: 1) mild ocean warming forcing ice margin retreat 2) rapid ocean warming as the ice sheet retreats.

We show that the Paris Agreement target temperature of 1.5°C is sufficient to drive runaway retreat of the WAIS.

Abstract
Over the last 5 million years, the Earth’s climate has oscillated between warm (interglacial) and cold (glacial) states. Some particularly warm interglacial periods (i.e. ‘super-interglacials’) occurred under low atmospheric CO2 and may have featured extensive Antarctic ice sheet collapse. Here we focus on an extreme super-interglacial known as Marine Isotope Stage 31 (MIS31), between 1.085 and 1.055 million years ago and is the subject of intense discussion. We reconstructed the first Southern Ocean and Antarctic margin sea surface temperatures (SSTs) from organic biomarkers and used them to constrain numerical ice sheet-shelf simulations. Our SSTs indicate that the ocean was on average 5 °C (±1.2 °C) warmer in summer than today between 50 °S and the Antarctic ice margin. Our most conservative ice sheet simulation indicates a complete collapse of the West Antarctic Ice Sheet (WAIS) with additional deflation of the East Antarctic Ice Sheet. We suggest the WAIS retreated because of anomalously high Southern Hemisphere insolation coupled with the intrusion of Circumpolar Deep Water onto the continental shelf under poleward-intensified winds leading to a shorter sea ice season and ocean warming at the continental margin. In this scenario, the extreme warming we observed likely reflects the extensively modified oceanic and hydrologic system following ice sheet collapse. Our work highlights the sensitivity of the Antarctic ice sheets to minor oceanic perturbations that could also be at play for future changes.


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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3487 on: July 12, 2020, 04:23:13 PM »
With a hat-tip to Andreas T, the linked twitter thread presents a: "Sequence of schematic figures illustrating some ideas on how ice shelf pinning points may develop during glacial retreat"

https://twitter.com/rdlarter/status/1272834862706237440

To me this is relevant to the area upstream of the pinning points for the Thwaites Ice Tongue and the expanding subglacial cavity at the base of this ice tongue.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3488 on: July 12, 2020, 04:38:26 PM »
With a hat-tip to gerontocrat, the two attached images of Greenland surface ice melt indicates that the 2020 melt season for Greenland has been well above average so far, and also I note that the calving season for key Greenland marine-terminating glaciers is starting to accelerate.  Both of this trends indicate that at least the North Atlantic cold blob is not going to dissipate anytime soon, and the it will likely continue to strengthen in coming years.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3489 on: July 12, 2020, 06:10:13 PM »
While the linked reference indicates that after the mid-Pleistocene transition (1,250 to 700 kyr ago) that periods of slow AMOC circulation resulted in a slow storage of carbon from the atmosphere into the deep ocean.  However, the linked associated article makes it clear that the current slowing of the AMOC will not result in such a slow sequestration of carbon into the deep ocean, but rather:

"… that less carbon-laden water will sink in the north, at the same time, in the Southern Ocean, any carbon already arriving in the deep water will likely keep bubbling up without any problem. The result: carbon will continue to build in the air, not the ocean."

Farmer, J.R., Hönisch, B., Haynes, L.L. et al. Deep Atlantic Ocean carbon storage and the rise of 100,000-year glacial cycles. Nat. Geosci. 12, 355–360 (2019). https://doi.org/10.1038/s41561-019-0334-6

https://www.nature.com/articles/s41561-019-0334-6

Abstract: "Over the past three million years, Earth’s climate oscillated between warmer interglacials with reduced terrestrial ice volume and cooler glacials with expanded polar ice sheets. These climate cycles, as reflected in benthic foraminiferal oxygen isotopes, transitioned from dominantly 41-kyr to 100-kyr periodicities during the mid-Pleistocene 1,250 to 700 kyr ago (ka). Because orbital forcing did not shift at this time, the ultimate cause of this mid-Pleistocene transition remains enigmatic. Here we present foraminiferal trace element (B/Ca, Cd/Ca) and Nd isotope data that demonstrate a close linkage between Atlantic Ocean meridional overturning circulation and deep ocean carbon storage across the mid-Pleistocene transition. Specifically, between 950 and 900 ka, carbonate ion saturation decreased by 30 µmol kg−1 and phosphate concentration increased by 0.5 µmol kg−1 coincident with a 20% reduction of North Atlantic Deep Water contribution to the abyssal South Atlantic. These results demonstrate that the glacial deep Atlantic carbon inventory increased by approximately 50 Gt during the transition to 100-kyr glacial cycles. We suggest that the coincidence of our observations with evidence for increased terrestrial ice volume reflects how weaker overturning circulation and Southern Ocean biogeochemical feedbacks facilitated deep ocean carbon storage, which lowered the atmospheric partial pressure of CO2 and thereby enabled expanded terrestrial ice volume at the mid-Pleistocene transition."

Title: "Carbon Lurking in Deep Ocean Threw Ancient Climate Switch, Say Researchers"

https://www.ldeo.columbia.edu/news-events/carbon-lurking-deep-ocean-threw-ancient-climate-switch-say-researchers

Extract: "The strength of the AMOC is believed to fluctuate naturally, but it appears to have weakened by an unusual 15 percent since the mid-20th century.

Farmer said that if the AMOC continues weakening now, it is probable that less carbon-laden water will sink in the north, at the same time, in the Southern Ocean, any carbon already arriving in the deep water will likely keep bubbling up without any problem. The result: carbon will continue to build in the air, not the ocean."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3490 on: July 12, 2020, 06:28:56 PM »
The video embedded in the linked article confirms that research in both Tahiti and Barbados confirms that at periods in the past sea level has increased at rates of 10-ft per century; which if replicated in coming decades would have major impacts on global socio-economic systems:

Title: "How High Can Seas Rise? On a Tropical Isle, the Answers Are Not Always Obvious."

https://www.ldeo.columbia.edu/news-events/how-high-can-seas-rise-tropical-isle-answers-are-not-always-obvious

Extract: "A 2009 study done in Barbados by other researchers suggests that 121,000 years ago, seas rose as much as 9 feet in just a century—perhaps due to a sudden collapse of the Western Antarctic Ice Sheet. If it could happen then, it could happen now, said Raymo. Using the newly exacting methods, she wanted to see if it really was so.

Barbados is a good place to start, though, she said, not only because of its fossil corals, but because it is close to the equator and relatively isolated from most effects except water level itself. “We like to call Barbados the dipstick of sea level,” she said."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3491 on: July 13, 2020, 12:16:22 AM »
... the current slowing of the AMOC ,,,
...

Title: "Carbon Lurking in Deep Ocean Threw Ancient Climate Switch, Say Researchers"

https://www.ldeo.columbia.edu/news-events/carbon-lurking-deep-ocean-threw-ancient-climate-switch-say-researchers

Extract: "The strength of the AMOC is believed to fluctuate naturally, but it appears to have weakened by an unusual 15 percent since the mid-20th century.
...

AMOC isn't currently slowing.

The following links to research papers show the opposite, the AMOC seems to be strengthening currently.
https://www.researchgate.net/publication/338658885_Pending_recovery_in_the_strength_of_the_meridional_overturning_circulation_at_26_N

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017GL076350

https://os.copernicus.org/articles/15/809/2019/

These results and other research indicating a current strengthening of the AMOC have been discussed in the following posts:

https://forum.arctic-sea-ice.net/index.php/topic,2205.msg240256.html#msg240256
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg272111.html#msg272111
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg271113.html#msg271113

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3492 on: July 13, 2020, 02:26:45 AM »
The linked reference confirms that the CMIP6 models project a significant decline of the AMOC this century, and I note that the CMIP6 projections to not consider the impacts of significant freshwater hosing events that might occur this century such as a partial collapse of the WAIS and/or a flux of relatively freshwater from the Beaufort Gyre.  A slowing of the AMOC slows the MOC; which results in increased SSTAs in the tropical regions that leads to more evaporation that leads to more high altitude cloud formations that leads to higher ECS values in the coming decades:

W. Weijer et al. (24 May 2020), "CMIP6 Models Predict Significant 21st Century Decline of the Atlantic Meridional Overturning Circulation", Geophysical Research Letters, https://doi.org/10.1029/2019GL086075

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086075?af=R

Abstract
We explore the representation of the Atlantic Meridional Overturning Circulation (AMOC) in 27 models from the CMIP6 multi‐model ensemble. Comparison with RAPID and SAMBA observations suggests that the ensemble mean represents the AMOC strength and vertical profile reasonably well. Linear trends over the entire historical period (1850‐2014) are generally neutral, but many models exhibit an AMOC peak around the 1980's. Ensemble‐mean AMOC decline in future (SSP) scenarios is stronger in CMIP6 than CMIP5 models. In fact, AMOC decline in CMIP6 is surprisingly insensitive to the scenario at least up to 2060. We find an emergent relationship among a majority of models between AMOC strength and 21st century AMOC decline. Constraining this relationship with RAPID observations suggests that the AMOC might decline between 6 and 8 Sv (34‐45%) by 2100. A smaller group of models projects much less AMOC weakening of only up to 30%.

Plain Language Summary
The Atlantic Meridional Overturning Circulation (AMOC) is a circulation pattern in the Atlantic Ocean that is an important component of the climate system, due to its ability to redistribute and sequester heat and carbon. An accurate representation of the AMOC is a critical test for climate models and essential for building confidence in their projections. Here we investigate the AMOC in 27 climate models that contributed simulations to the Coupled Model Intercomparison Project phase 6 (CMIP6). We find that many models reproduce the observed AMOC quite well, but there are still several models in which the AMOC is too weak or too strong. Most models suggest a slight upward trend in the AMOC from 1850 to the 1980's. Simulations representing different scenarios for future socioeconomic development suggest a stronger AMOC decline compared to previous assessments. Using direct measurements of the AMOC since 2004 and an emerging across‐model relationship between AMOC decline in the 21st century and their present‐day mean state, we find that the majority of CMIP6 models point to an end of century AMOC weakening of 34%‐45% of its present‐day strength. A smaller group of models projects much less weakening of only up to 30% of its present state.

In addition to the quoted reference that indicates that CMIP6 projects a strong decline in the AMOC by about 34% to 45% by 2100; Liu et al. (2020) confirms that:

"The AMOC has been observed to slow down over the past decade in the Rapid Climate Change (RAPID) array at 26.5°N in the North Atlantic, although this AMOC slowdown can be part of natural climate variability, considering the relatively short observational period."

Wei Liu et al. (26 Jun 2020), Climate impacts of a weakened Atlantic Meridional Overturning Circulation in a warming climate", Science Advances, Vol. 6, no. 26, eaaz4876< DOI: 10.1126/sciadv.aaz4876

https://advances.sciencemag.org/content/6/26/eaaz4876

Abstract
While the Atlantic Meridional Overturning Circulation (AMOC) is projected to slow down under anthropogenic warming, the exact role of the AMOC in future climate change has not been fully quantified. Here, we present a method to stabilize the AMOC intensity in anthropogenic warming experiments by removing fresh water from the subpolar North Atlantic. This method enables us to isolate the AMOC climatic impacts in experiments with a full-physics climate model. Our results show that a weakened AMOC can explain ocean cooling south of Greenland that resembles the North Atlantic warming hole and a reduced Arctic sea ice loss in all seasons with a delay of about 6 years in the emergence of an ice-free Arctic in boreal summer. In the troposphere, a weakened AMOC causes an anomalous cooling band stretching from the lower levels in high latitudes to the upper levels in the tropics and displaces the Northern Hemisphere midlatitude jets poleward.

Also, the linked Carbon Brief article confirms that the AMOC is projected to decline with continued global warming.

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

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

Extract: "The latest research suggests that AMOC is very likely to weaken this century, but a collapse is very unlikely."
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Hefaistos

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3493 on: July 13, 2020, 11:07:22 AM »
The Liu et al paper refers to other research that uses AMOC data up until 2017, which are claimed to show a slight slowdown of the AMOC. Developments since then seem to contradict that. The latest AMOC data are from September 2018.

Desbruyères et al, 2019, Ocean Sci., 15, 809–817 clearly demonstrate that the AMOC is currently strengthening, and they even give a bold forecast for the coming years:

"An easily observed surface quantity – the rate of warm to cold transformation of water masses at high latitudes – is found to lead the observed AMOC at 45∘ N by 5–6 years and to drive its 1993–2010 decline and its ongoing recovery, with suggestive prediction of extreme intensities for the early 2020s."

AMOC is forecasted to have "extreme intensities" in the coming years, as the AMOC is 'downstream' with a lag of 5 to 6 years from the already intensified warm to cold transformation of water masses at high latitudes.

CMIP6 models should probably try to include these recent research findings as well.
Also, Liu et al use the already defunct RCP8.5 for all their GIGO simulations.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3494 on: July 13, 2020, 06:40:39 PM »
The Liu et al paper refers to other research that uses AMOC data up until 2017, which are claimed to show a slight slowdown of the AMOC. Developments since then seem to contradict that. The latest AMOC data are from September 2018.

Desbruyères et al, 2019, Ocean Sci., 15, 809–817 clearly demonstrate that the AMOC is currently strengthening, and they even give a bold forecast for the coming years:
...

Hefaistos,

Everyone agrees that there are natural fluctuations of the AMOC/MOC that are superimposed on the anthropogenic forced trends.  Thus, some of the annual data that you focus on reminds me of the discussions a few years ago about the 'faux hiatus' in the GMSTA trend of growth.

In this regard, the following linked reference's finding that part of the E3SM version 1 projected high value of TCR 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 than other CMIP5, & CMIP6, models.  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.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3495 on: July 13, 2020, 09:37:58 PM »
The linked article indicates that the NSF is concerned about the stability of the Thwaites Glacier and that a collapse of Thwaites could then trigger a collapse of the WAIS:

Title: "‘Teetering at the edge’: Scientists warn of rapid melting of Antarctica’s ‘Doomsday glacier’"

https://www.independent.co.uk/environment/thwaites-glacier-antarctic-melting-doomsday-climate-a9616966.html

Extract: "The Thwaites glacier is 74,000 square miles, roughly the size of the UK. The ice melt draining from Thwaites into the Amundsen Sea already accounts for 4 per cent of global sea-level rise but scientists are concerned its continued existence is hanging in the balance as the world warms.

“The big question is how quickly it becomes unstable. It seems to be teetering at the edge,” Paul Cutler, programme director for Antarctic glaciology at America’s National Science Foundation told the Financial Times this week.

“It is a keystone for the other glaciers around it in West Antarctica,” he said. “If you remove it, other ice will potentially start draining into the ocean too.”"
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3496 on: July 13, 2020, 10:19:09 PM »
The two attached images represent Hausfather's and Schmidt's projection of GMSTA for 2020 based on data thru June 2020, respectively.  These projections indicate a good chance that 2020 may be the warmest year on record.

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3497 on: July 14, 2020, 12:21:27 AM »
The attached image from the linked website indicates that Brown projects an 85% chance that 2020 will be the warmest year on record based on data thru June 2020:

Subtitle: "Operational forecast"

https://www.weatherclimatehumansystems.org/global-temperature-forecast

Extract: "Below are hind-casts and a real-time forecast of global temperature over the next several years, modified from the method published in Brown and Caldeira (2020)."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3498 on: July 14, 2020, 03:43:22 AM »
Miami vs The Sea - Part 17: Injection Wells

Without a lot of fanfare, Miami Beach has retreated from using injection wells in response to its sunny day flooding issues.  From  http://www.mbrisingabove.com/your-city-at-work/stormwater-program/stormwater-pumps/  :

"It’s important to note that most pump station systems in the city were initially converted to direct water into injection wells. Injection wells are devices that help push water and other material underground. However, this option was no longer viable because the city is not only facing the effects of rising sea level but also dealing with a reduced capacity for soil to store rain water which equals to a reduced capacity to push water underground. The existing pump stations are no longer connected to injection wells and are instead directed to outfalls."

With regard to these stormwater pumps:

a) the city began installing them around 2014
b) there were to be 60 in total
c) each one pumps 233 gallons per second
d) they work better when they have electricity and
e) total project cost was around $300 million. 


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Tom_Mazanec

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3499 on: July 14, 2020, 11:33:34 AM »
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