Ice Apocalypse - Multiple Meters Sea Level Rise

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This conclusion raises the issue that the unbelievably high ECS models are manipulated in a false way as a means to achieve a goal, namely the high ECS value.
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Your statement indicates that you are accusing many CMIP6 climate scientists of intentionally manipulating their models to achieve false projections.

Such a conspiracy theory is not worth addressing here.

[Hefaistos]

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This conclusion raises the issue that the unbelievably high ECS models are manipulated in a false way as a means to achieve a goal, namely the high ECS value.
...

Your statement indicates that you are accusing many CMIP6 climate scientists of intentionally manipulating their models to achieve false projections.

Such a conspiracy theory is not worth addressing here.

Yes, intentional or not, but that's my interpretation of what Zelinka et al says in "Causes of Higher Climate Sensitivity in CMIP6 Models" in Geophysical Research Letters.

I repeat the quote from the papers' Conclusions (my added italics/bold): "While some high ECS models closely match the observed record (e.g., Gettelman et al., 2019), others do not (e.g., Golaz et al., 2019). Do the former models achieve their results via unreasonably large negative aerosol forcings and/or substantial pattern effects (Kiehl, 2007; Stevens et al., 2016)? It is worth noting that cloud feedbacks are enhanced in CMIP6 primarily over the Southern Ocean, a region of efficient ocean heat uptake (Armour et al., 2016). This implies that the enhanced surface SW heating is less likely to manifest as surface warming during transient climate change than if the heating were focused elsewhere (Frey et al., 2017). This cloud feedback pattern could make it easier for high ECS models to simulate the observed surface temperature record without requiring a large negative aerosol radiative forcing or large historical era pattern effects."

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

[Hefaistos]

Kate Marvel has spent most of her career studying cloud feedback (which has proven to be key w.r.t. the high values of ECS projected by the high-end CMIP6 model projections) and in the linked opinion piece she acknowledges a good amount of uncertainty about projections of future climate change; which from a risk point of view is not good:

Title: "Global Warming: How Hot, Exactly, Is it Going to Get?"

https://blogs.scientificamerican.com/hot-planet/global-warming-how-hot-exactly-is-it-going-to-get/

Extract: "All climate models simulate a changing planet in response to a changing temperature. And, increasingly, we know why they disagree on that final warming. In the climate models that warm more, low, thick clouds appear to be changing in ways that reduce their sun-blocking power. In the models that warm less, these changes are smaller.

So scientists have devoted their time to measuring clouds, understanding them, and figuring out how to represent them in climate models. This work has paid off: the range of uncertainty is now changing. Unfortunately, it’s increased. Climate models that use more modern techniques to simulate clouds are now projecting more warming: five or six degrees Celsius in response to a doubling of carbon dioxide. To put those numbers in context, four and a half degrees is the difference between now and the last Ice Age.
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But the past is not the future, and we have good reason to believe that there are no analogues for the future into which we are hurtling."

She is quite skeptical to the unbelievably high ECS values of the majority of CMIP6 models, though:
"I find these high numbers hard to believe, but as a scientist it’s my job to find things hard to believe. My skepticism is rooted in clues from the planet’s past. At the height of the last Ice Age, temperatures were cooler and carbon dioxide levels lower. It’s hard to reconcile these measurements with extremely high climate sensitivities."

[AbruptSLR]

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"At the height of the last Ice Age, temperatures were cooler and carbon dioxide levels lower. It’s hard to reconcile these measurements with extremely high climate sensitivities."

Casual comments, like Kate Marvel's, tend to over-simplify the complexity of the behavior of the combined Earth Systems.  For instance, the linked article explains how hysteresis of various cloud feedback mechanisms need to be applied in order to correctly interpret many paleo climate responses, such as in the following quote from the linked article:

'

During the Pliocene, 3 million years ago, the atmospheric CO2 level was 400 ppm, similar to today, but Earth was 4 degrees hotter. This might be because we were cooling down from a much warmer, perhaps largely cloudless period, and stratocumulus clouds hadn’t yet come back.

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See also the two attached images from Schneider et al. (2019) that show hysteresis behavior in models associated with the PETM. 

Thus, when considering hysteresis, it is not hard to reconcile the paleorecord with high values of climate sensitivity.

Title: "A World Without Clouds"

https://www.quantamagazine.org/cloud-loss-could-add-8-degrees-to-global-warming-20190225/

Extract: "A state-of-the-art supercomputer simulation indicates that a feedback loop between global warming and cloud loss can push Earth’s climate past a disastrous tipping point in as little as a century.
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To see how the loss of clouds would affect the global temperature, Schneider and colleagues inverted the approach of global climate models, simulating their cloud patch at high resolution and parameterizing the rest of the world outside that box. They found that, when the stratocumulus clouds disappeared in the simulation, the enormous amount of extra heat absorbed into the ocean increased its temperature and rate of evaporation. Water vapor has a greenhouse effect much like CO2, so more water vapor in the sky means that more heat will be trapped at the planet’s surface. Extrapolated to the entire globe, the loss of low clouds and rise in water vapor leads to runaway warming — the dreaded 8-degree jump. After the climate has made this transition and water vapor saturates the air, ratcheting down the CO2 won’t bring the clouds back. “There’s hysteresis,” Schneider said, where the state of the system depends on its history. “You need to reduce CO2 to concentrations around present day, even slightly below, before you form stratocumulus clouds again.”

Paleoclimatologists said this hysteresis might explain other puzzles about the paleoclimate record. During the Pliocene, 3 million years ago, the atmospheric CO2 level was 400 ppm, similar to today, but Earth was 4 degrees hotter. This might be because we were cooling down from a much warmer, perhaps largely cloudless period, and stratocumulus clouds hadn’t yet come back.
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But other unforeseen changes and climate tipping points could accelerate us toward the cliff. “I’m worried,” said Kennett, the pioneering paleoceanographer who discovered the PETM and unearthed evidence of many other tumultuous periods in Earth’s history. “Are you kidding? As far as I’m concerned, global warming is the major issue of our time.”"

[AbruptSLR]

The linked open access reference concludes that CMIP6 projections find that:

"The major implication is that over coastal Antarctica, the surface warming by 2100 is stronger relative to the global mean surface warming for the low forcing compared to high forcing future scenarios."

This implies that SSP2-4.5, may very likely lead to higher SAT values over coastal Antarctica than say SSP5-8.5.  If so, this implies that if countries follow the Paris emission pledges then the ice shelves around Antarctica are more likely to disintegrate than following a BAU GHG emission pathway.

Thomas J. Bracegirdle et al. (28 May 2020), "Twenty first century changes in Antarctic and Southern Ocean surface climate in CMIP6", Atmospheric Science Letters, https://doi.org/10.1002/asl.984

https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/asl.984

Abstract: "Two decades into the 21st century there is growing evidence for global impacts of Antarctic and Southern Ocean climate change. Reliable estimates of how the Antarctic climate system would behave under a range of scenarios of future external climate forcing are thus a high priority. Output from new model simulations coordinated as part of the Coupled Model Intercomparison Project Phase 6 (CMIP6) provides an opportunity for a comprehensive analysis of the latest generation of state‐of‐the‐art climate models following a wider range of experiment types and scenarios than previous CMIP phases. Here the main broad‐scale 21st century Antarctic projections provided by the CMIP6 models are shown across four forcing scenarios: SSP1‐2.6, SSP2‐4.5, SSP3‐7.0 and SSP5‐8.5. End‐of‐century Antarctic surface‐air temperature change across these scenarios (relative to 1995–2014) is 1.3, 2.5, 3.7 and 4.8°C. The corresponding proportional precipitation rate changes are 8, 16, 24 and 31%. In addition to these end‐of‐century changes, an assessment of scenario dependence of pathways of absolute and global‐relative 21st century projections is conducted. Potential differences in regional response are of particular relevance to coastal Antarctica, where, for example, ecosystems and ice shelves are highly sensitive to the timing of crossing of key thresholds in both atmospheric and oceanic conditions. Overall, it is found that the projected changes over coastal Antarctica do not scale linearly with global forcing. We identify two factors that appear to contribute: (a) a stronger global‐relative Southern Ocean warming in stabilisation (SSP2‐4.5) and aggressive mitigation (SSP1‐2.6) scenarios as the Southern Ocean continues to warm and (b) projected recovery of Southern Hemisphere stratospheric ozone and its effect on the mid‐latitude westerlies. The major implication is that over coastal Antarctica, the surface warming by 2100 is stronger relative to the global mean surface warming for the low forcing compared to high forcing future scenarios."

[AbruptSLR]

In the linked YouTube video, Andrew Dessler discusses non-linear impacts of climate change, that will likely lead to surprises to decision makers (& the general public) who have waited too long to take effective climate action:

Title: "Stephen Schneider Lecture"

https://www.youtube.com/watch?v=0a90OzLMBC4&feature=youtu.be&t=1296

[AbruptSLR]

If you have the time, the linked YouTube video can bring you up to speed on ECS and cloud feedback:

Title: "ECS & cloud feedback symposium - virtual seminar 1", May 28, 2020 speakers: Maria Rugenstein, Brian Soden and Mark Zelinka (his talk comparing ECS values from CMIP5 with CMIP6 starts near minute 45):

https://www.youtube.com/watch?v=DuSD-rLCZNY&feature=youtu.be

[AbruptSLR]

The linked reference describes how the loss of Arctic sea ice is increasing climate variability around the world, including on the Pacific trade winds and Central Pacific El Nino events>

Charles F. Kennel and Elena Yulaeva, (2020), "Influence of Arctic sea-ice variability on Pacific trade winds", PNAS, 117 (6) 2824-2834, https://doi.org/10.1073/pnas.1717707117

https://www.pnas.org/content/117/6/2824

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

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

[Hefaistos]

Another recent paper highly critical of the unbelievably high ECS values of many CMIP6 models is "Past warming trend constrains future warming in CMIP6 models" by Tokarska et al in Science Advances, March 2020

"Our results show that most models with high climate sensitivity
(outside the AR5 likely range) or high transient response overestimate
recent warming trends, with differences that cannot be
explained by internal variability. This probably leads to future
warming projections being biased high. Thus, the raw ensemble
median and spread of future warming in CMIP6 (and therefore
most other variables that scale to first order with global mean temperature)
are not representative of a distribution constrained by
observed trends,"

DOI: 10.1126/sciadv.aaz9549
Open access.

Seems relevant to ask, have these CMIP models with unbelievably high ECS values got their fundamental physics reg. clouds and water vapor right?

[AbruptSLR]

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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). 

Second, per Mark Zelinka's talk in Reply #3256, the CMIP6 models (gold in the attached image) more closely match the observed mean-state liquid condensate fraction (LCF) in clouds that do the CMIP5 models (blue in the attached image).  So at least by this measure the CMIP6 models (on average) model fundamental physics better than did the CMIP5 models.

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Per the attached image, the weekly atmospheric CO2 concentration at Mauna Loa thru May 30, 2020 is well ahead of where it was at the same time last year.

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If you have the time, the linked YouTube video can bring you up to speed on ECS and cloud feedback:

Title: "ECS & cloud feedback symposium - virtual seminar 1", May 28, 2020 speakers: Maria Rugenstein, Brian Soden and Mark Zelinka (his talk comparing ECS values from CMIP5 with CMIP6 starts near minute 45):

https://www.youtube.com/watch?v=DuSD-rLCZNY&feature=youtu.be

The three attached images are from the Maria Rugenstein talk within the linked video and they show that due to the pattern effect different definitions of ECS result in different calculated values for ECS for the same model output.  Thus, as IPCC does not adjust for the author's method of calculating ECS in peer reviewed papers, reported ranges of ECS AR6 will contain more uncertainty than reported due to the scatter of ECS from different reported calculation methodologies.  Furthermore, the second image shows that for period of up to 5,000-years the indicated CMIP6 model could have an ECS of over 6.7C; thus if abrupt ice-climate feedback mechanisms (like abrupt loss of Arctic sea ice and/or abrupt MICI-type failure of the WAIS) occur in coming decades (which was not evaluated by any CMIP6 model) then ECS could increase faster towards the 6.7C value than illustrated by the second image.

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The linked reference indicates that the measured US fossil fuel CO2 emission were about 10% higher than previously indicated by the US EPA:

Sourish Basu et al. (June 1, 2020), "Estimating US fossil fuel CO2 emissions from measurements of 14C in atmospheric CO2", PNAS, https://doi.org/10.1073/pnas.1919032117

https://www.pnas.org/content/early/2020/05/29/1919032117

Significance
The vast majority of the world’s nations have pledged to reduce emissions of CO2 and other greenhouse gases and to track and report emissions using accounting methods based on economic statistics and emissions factors. Here, we present an independent method of emissions monitoring based directly on atmospheric observations and the strong fossil fuel CO2 detection capability afforded by precise measurements of 14CO2 in air samples obtained largely from NOAA’s air sampling network. The national total we derive for 2010 is larger than from available inventories, including the US EPA, but is within error bounds of the updated Vulcan emission data product. These results suggest that reported emissions can now be subject to independent and objective evaluation using atmospheric 14CO2 measurements.

Abstract
We report national scale estimates of CO2 emissions from fossil-fuel combustion and cement production in the United States based directly on atmospheric observations, using a dual-tracer inverse modeling framework and CO2 and Δ14CO2Δ14CO2 measurements obtained primarily from the North American portion of the National Oceanic and Atmospheric Administration’s Global Greenhouse Gas Reference Network. The derived US national total for 2010 is 1,653 ± 30 TgC yr−1 with an uncertainty (1σ1σ) that takes into account random errors associated with atmospheric transport, atmospheric measurements, and specified prior CO2 and 14C fluxes. The atmosphere-derived estimate is significantly larger (>3σ>3σ) than US national emissions for 2010 from three global inventories widely used for CO2 accounting, even after adjustments for emissions that might be sensed by the atmospheric network, but which are not included in inventory totals. It is also larger (>2σ>2σ) than a similarly adjusted total from the US Environmental Protection Agency (EPA), but overlaps EPA’s reported upper 95% confidence limit. In contrast, the atmosphere-derived estimate is within 1σ1σ of the adjusted 2010 annual total and nine of 12 adjusted monthly totals aggregated from the latest version of the high-resolution, US-specific “Vulcan” emission data product. Derived emissions appear to be robust to a range of assumed prior emissions and other parameters of the inversion framework. While we cannot rule out a possible bias from assumed prior Net Ecosystem Exchange over North America, we show that this can be overcome with additional Δ14CO2Δ14CO2 measurements. These results indicate the strong potential for quantification of US emissions and their multiyear trends from atmospheric observations.

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The linked reference, and associate article, indicate that '… a geomagnetic pulse under South America in 2016 shifted the magnetic field unexpectedly …'; which may have triggered '… a high-speed jet of liquid iron beneath Canada…'; which may have weakened the magnetic field beneath Canada, allowing the high-strength magnetic field beneath Siberia to accelerate the migration of the magnetic north pole towards Siberia since 2016.  Whether the acceleration in magnetic polar wander shown in the first attached image (from Nature 2019) is related to the high magnetic anomaly in the South Atlantic, see the second image (and Replies #113, #115 & #117), and thus possibly to Antarctic ice mass loss, is a matter worth investigating.

Title: "Earth's magnetic field is acting up and geologists don't know why"

https://www.nature.com/articles/d41586-019-00007-1?utm_source=twt_nnc&utm_medium=social&utm_campaign=naturenews&sf205680051=1

Extract: "First, that 2016 geomagnetic pulse beneath South America came at the worst possible time, just after the 2015 update to the World Magnetic Model.
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… scientist are working to understand why the magnetic field is changing so dramatically. Geomagnetic pulses, like the one that happened in 2016, might be traces back to 'hydromagnetic' waves arising from deep in the core.  And the fast motion of the north magnetic pole could be linked to a high-speed jet of liquid iron beneath Canada."

See also:

Earth's Magnetic Field has Moved Unexpectedly and Scientists Aren't Sure Why

https://www.newsweek.com/earth-magnetic-field-baffle-scientists-north-pole-siberia-canada-world-1286507

Extract: "Earth’s north magnetic pole is moving fast and in an unexpected way, baffling scientists involved in tracking its motions
…
"The error is increasing all the time,” Arnaud Chulliat, a geomagnetist at the University of Colorado Boulder and the National Oceanic and Atmospheric Administration (NOAA), told Nature. He said finding out the WMM had become inaccurate placed scientists in an “interesting situation” with experts wondering just what was going on.

According to Nature, a geomagnetic pulse under South America in 2016 shifted the magnetic field unexpectedly. This was exacerbated by the movement of the north magnetic pole. “The fact that the pole is going fast makes this region more prone to large errors,” Chulliat is quoted as saying.

Researchers are now trying to work out why the magnetic field is changing so quickly. They are studying the geomagnetic pulses, like the one that disrupted the WMM in 2016, which could, Nature reports, be the result of “hydromagnetic” waves emanating from Earth’s core.

To fix the World Magnetic Model, he and his colleagues fed it three years of recent data, which included the 2016 geomagnetic pulse. The new version should remain accurate, he says, until the next regularly scheduled update in 2020."

Per the linked website/video the South Atlantic Anomaly, in the Earth's magnetic field, is spreading towards Africa.  What will happen to this phenomenon if the WAIS collapses?

title: "Mysterious weak spot in the Earth's magnetic field is spreading: ESA"

https://www.msn.com/en-us/video/science/mysterious-weak-spot-in-the-earth-s-magnetic-field-is-spreading-esa/vi-BB14UBIk?ocid=msedgdhp

Extract: "A mysterious anomaly in the Earth's magnetic field that stretches from South America to Africa is spreading."

[AbruptSLR]

The linked article indicates that initial measures show that methane emissions have increased during the COVID-19 crisis, as compared to the same period in 2019, possibly due increase burning, and venting, of surplus natural gas supplies:

Title: "Detecting methane emissions during COVID-19"

https://phys.org/news/2020-06-methane-emissions-covid-.html

Extract: "An initial look at these data suggest a substantial increase in methane concentrations in 2020, compared to 2019. Claus Zehner, ESA's Copernicus Sentinel-5P mission manager, says, "An explanation for this could be that as a result of less demand for gas because of COVID-19, it is burned and vented—leading to higher methane emissions over this area."

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Per the linked article the Trump administration is on track to rescind requirements for U.S. oil & gas companies to reduce their methane emissions:

Title: " US readies repeal of methane rules for oil sector"

https://www.argusmedia.com/en/news/2110390-us-readies-repeal-of-methane-rules-for-oil-sector

Extract: "President Donald Trump's administration says it could rescind requirements for oil and gas companies to reduce their emissions of methane, a potent greenhouse gas, by the end of next month."

[AbruptSLR]

The linked open access reference helps to quantify the increasing methane emissions from boreal lakes primarily due to the increasing number of ice-free days:

Mingyang Guo et al. (19 May 2020), "Rising methane emissions from boreal lakes due to increasing ice-free days", Environmental Research Letters, Volume 15, Number 6, https://doi.org/10.1088/1748-9326/ab8254

https://iopscience.iop.org/article/10.1088/1748-9326/ab8254
https://iopscience.iop.org/article/10.1088/1748-9326/ab8254/pdf

Abstract
Lakes account for about 10% of the boreal landscape and are responsible for approximately 30% of biogenic methane emissions that have been found to increase under changing climate. However, the quantification of this climate-sensitive methane source is fraught with large uncertainty under warming climate conditions. Only a few studies have addressed the mechanism of climate impact on the increase of northern lake methane emissions. This study uses a large observational dataset of lake methane concentrations in Finland to constrain methane emissions with an extant process-based lake biogeochemical model. We found that the total current diffusive emission from Finnish lakes is 0.12 ± 0.03 Tg CH4 yr−1 and will increase by 26%–59% by the end of this century depending on different warming scenarios. We discover that while warming lake water and sediment temperature plays an important role, the climate impact on ice-on periods is a key indicator of future emissions. We conclude that these boreal lakes remain a significant methane source under the warming climate within this century.

[AbruptSLR]

The linked reference helps to identify the amount of the net increases in CH4 and N2O emissions from soil with continued global warming:

Shuwei Liu et al. (13 May 2020), "Increased soil release of greenhouse gases shrinks terrestrial carbon uptake enhancement under warming", Global Change Biology, https://doi.org/10.1111/gcb.15156

https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15156?af=R

Abstract
Warming can accelerate the decomposition of soil organic matter and stimulate the release of soil greenhouse gases (GHGs), but to what extent soil release of methane (CH4) and nitrous oxide (N2O) may contribute to soil C loss for driving climate change under warming remains unresolved. By synthesizing 1,845 measurements from 164 peer‐reviewed publications, we show that around 1.5°C (1.16–2.01°C) of experimental warming significantly stimulates soil respiration by 12.9%, N2O emissions by 35.2%, CH4 emissions by 23.4% from rice paddies, and by 37.5% from natural wetlands. Rising temperature increases CH4 uptake of upland soils by 13.8%. Warming‐enhanced emission of soil CH4 and N2O corresponds to an overall source strength of 1.19, 1.84, and 3.12 Pg CO2‐equivalent/year under 1°C, 1.5°C, and 2°C warming scenarios, respectively, interacting with soil C loss of 1.60 Pg CO2/year in terms of contribution to climate change. The warming‐induced rise in soil CH4 and N2O emissions (1.84 Pg CO2‐equivalent/year) could reduce mitigation potential of terrestrial net ecosystem production by 8.3% (NEP, 22.25 Pg CO2/year) under warming. Soil respiration and CH4 release are intensified following the mean warming threshold of 1.5°C scenario, as compared to soil CH4 uptake and N2O release with a reduced and less positive response, respectively. Soil C loss increases to a larger extent under soil warming than under canopy air warming. Warming‐raised emission of soil GHG increases with the intensity of temperature rise but decreases with the extension of experimental duration. This synthesis takes the lead to quantify the ecosystem C and N cycling in response to warming and advances our capacity to predict terrestrial feedback to climate change under projected warming scenarios.

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The linked reference indicates that new bathymetry from beneath the Getz Ice Shelf shows that the channels conveying modified CDW from the continental slope to beneath the ice shelf are deeper than previously assumed:

Romain Millan, Pierre St‐Laurent, Eric Rignot, Mathieu Morlighem, J. Mouginot and B. Scheuchl (30 May 2020), "Constraining an ocean model under Getz Ice Shelf, Antarctica, using a gravity‐derived bathymetry", Geophysical Research Letters, https://doi.org/10.1029/2019GL086522

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086522?af=R

Abstract
Getz Ice Shelf, the largest producer of ice shelf meltwater in Antarctica, buttresses glaciers that hold enough ice to raise sea level by 22 cm. We present a new bathymetry of its sub‐ice shelf cavity using a 3D inversion of airborne gravity data constrained by multibeam bathymetry at sea and a reconstruction of the bedrock from mass conservation on land. The new bathymetry is deeper than previously estimated with differences exceeding 500 m in a number of regions. When incorporated into an ocean model, it yields a better description of the spatial distribution of ice shelf melt, specifically along glacier grounding lines. While the melt intensity is overestimated because of a positive bias in ocean thermal forcing, the study reveals the main pathways along which warm oceanic water enters the cavity and corroborates the observed rapid retreat of Berry Glacier along a deep channel with a retrograde bed slope.

Plain Language Summary
The Getz Ice Shelf is a major ice shelf in West Antarctica that is rapidly melting. Its exposure to warm oceanic water has made it the largest producer of ice‐shelf meltwater in Antarctica. To understand its evolution and the impact on sea level rise of the glaciers that flow into it, it is essential to obtain a better description of the bathymetry beneath its hundreds of meters of floating ice. We use a combination of airborne gravity and other data to infer the depth of the cavity. We find the seabed to be in several regions more than 500 m deeper than previously reported, hence revealing one of the deepest ice shelf cavities in West Antarctica. When used in combination with an ocean model, the bathymetry helps to better explain the spatial variability in melt observed from remote sensing data, the pathways for warm waters to reach the ice shelf, and the recent evolution of selected glaciers.

[interstitial]

Romain Millan, Pierre St‐Laurent, Eric Rignot, Mathieu Morlighem, J. Mouginot and B. Scheuchl (30 May 2020), "Constraining an ocean model under Getz Ice Shelf, Antarctica, using a gravity‐derived bathymetry", Geophysical Research Letters, https://doi.org/10.1029/2019GL086522
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086522?af=R

wish I had access to the bathymetry map.

[sidd]

Re: bathymetry data

From the Millan paper:

"The data used in the manuscript are archived at datadryad.org (https://doi.org/10.7280/D1XM31). The bathymetry is already part of BedMachine v1 which is publicly available at https://nsidc.org/data/NSIDC-0756/ "

NSIDC bedmachine in the second link is the one for bathymetry

sidd

[nanning]

Via: https://sci-hub.tw/https://doi.org/10.1029/2019GL086522
BedMap images from the paper:

[interstitial]

Thanks everyone 

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Per the attached image, the weekly atmospheric CO2 concentration at Mauna Loa thru May 30, 2020 is well ahead of where it was at the same time last year.

Here is another representation of the atmospheric CO2 concentration peak thru May 2020 at Mauna Loa:

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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

Abstract
The ocean has absorbed the equivalent of 39% of industrial‐age fossil carbon emissions, significantly modulating the growth rate of atmospheric CO2 and its associated impacts on climate. Despite the importance of the ocean carbon sink to climate, our understanding of the causes of its interannual‐to‐decadal variability remains limited. This hinders our ability to attribute its past behavior and project its future. A key period of interest is the 1990s, when the ocean carbon sink did not grow as expected. Previous explanations of this behavior have focused on variability internal to the ocean or associated with coupled atmosphere/ocean modes. Here, we use an idealized upper ocean box model to illustrate that two external forcings are sufficient to explain the pattern and magnitude of sink variability since the mid‐1980s. First, the global‐scale reduction in the decadal‐average ocean carbon sink in the 1990s is attributable to the slowed growth rate of atmospheric pCO2. The acceleration of atmospheric pCO2 growth after 2001 drove recovery of the sink. Second, the global sea surface temperature response to the 1991 eruption of Mt Pinatubo explains the timing of the global sink within the 1990s. These results are consistent with previous experiments using ocean hindcast models with variable atmospheric pCO2 and with and without climate variability. The fact that variability in the growth rate of atmospheric pCO2 directly imprints on the ocean sink implies that there will be an immediate reduction in ocean carbon uptake as atmospheric pCO2 responds to cuts in anthropogenic emissions.

Plain Language Summary
Humans have added 440Pg of fossil fuel carbon to the atmosphere since 1750, driving up the atmospheric CO2 concentration. But not all of this carbon remains in the atmosphere. The ocean has absorbed 39%, substantially mitigating anthropogenic climate change. Though this “ocean carbon sink” is a critical climate process, our understanding of its mechanisms remains limited. Of great interest is the unexplained slow‐down of the ocean carbon sink in the 1990s and a subsequent recovery. In this work, we use a simple globally‐averaged model to show that two processes external to the ocean are sufficient to explain the slowing of the ocean carbon sink in the 1990s. First, a reduced rate of accumulation of carbon in the atmosphere after 1989 reduced the atmosphere–ocean gradient that drives the ocean sink. Second, the eruption of Mt Pinatubo led to changes in ocean temperature that modified the timing of the sink from 1991 to 2001. We illustrate that the most important control on the decade‐averaged magnitude of the ocean sink is variability in the growth rate of atmospheric CO2. This implies that as future fossil fuel emission cuts drive reduced growth of atmospheric CO2, the ocean sink will immediately slow down.

[AbruptSLR]

The linked open access reference presents conceptual models for Cryovolcanism in Arctic permafrost; which could emission increasing amounts of methane into the atmosphere with continued global warming:

Evgeny Chuvilin et al, Conceptual Models of Gas Accumulation in the Shallow Permafrost of Northern West Siberia and Conditions for Explosive Gas Emissions, Geosciences (2020). DOI: 10.3390/geosciences10050195

https://www.mdpi.com/2076-3263/10/5/195/htm

Abstract
Gas accumulation and pressurized unfrozen rocks under lakes (sublake taliks) subject to freezing in shallow permafrost may lead to explosive gas emissions and the formation of craters. Gas inputs into taliks may have several sources: microbially-mediated recycling of organic matter, dissociation of intrapermafrost gas hydrates, and migration of subpermafrost and deep gases through permeable zones in a deformed crust. The cryogenic concentration of gas increases the pore pressure in the freezing gas-saturated talik. The gradual pressure buildup within the confined talik causes creep (ductile) deformation of the overlying permafrost and produces a mound on the surface. As the pore pressure in the freezing talik surpasses the permafrost strength, the gas-water-soil mixture of the talik erupts explosively and a crater forms where the mound was. The critical pressure in the confined gas-saturated talik (2–2.5 MPa for methane) corresponds to the onset of gas hydrate formation. The conditions of gas accumulation and excess pressure in freezing closed taliks in shallow permafrost, which may be responsible for explosive gas emissions and the formation of craters, are described by several models.

[AbruptSLR]

It may take years to revise the environmental damage done by the Trump administration, even if Trump loses the 2020 election:

Title: "Trump orders agencies cut environment reviews, citing 'economic emergency'"

https://www.theguardian.com/us-news/2020/jun/04/trump-environment-reviews-cut-economic-emergency

Extract: "The Trump administration continued to weaken core environmental protections in the US by announcing a pair of policies to cut reviews for large infrastructure projects and downplay the health benefits of rules to curb pollution."

[AbruptSLR]

The linked article no only indicates that climate change is currently happening faster that consensus climate scientists previously thought was the case; it also indicates that consensus climate science has a limited understanding of the cooling (negative feedback) impact of anthropogenic aerosols.  The article concludes that the current reduction in anthropogenic aerosols will soon help climate scientists to better understand/delineate the cooling (negative feedback) impact of anthropogenic aerosol emissions:

Title: "COVID-19 pandemic a 'bonanza' for climate scientists"

https://newseu.cgtn.com/news/2020-06-06/COVID-19-pandemic-a-bonanza-for-climate-scientists-R5dfA13QYM/index.html

Extract: "The problem with the future, of course, is that it is, by definition, uncertain. That has been reflected in recent climate modeling, which has often underestimated the effects of global warming. It is happening faster than many experts expected, with possibly more extreme results, and in ways we still do not completely understand.
...
It is not so much the drop in carbon dioxide emissions that stokes Meinshausen's excitement. CO2 has been building up in the Earth's atmosphere for centuries and staying there. A few months of lower output will make very little difference to the overall picture. It is approaching dangerous levels beyond which we will have to extract it – via natural or artificial "carbon sinks" such as forests or carbon-capture technology.

No, Meinshausen's fascination is on a reduction in other man-made aerosols, many of which do not last long in the air but actually block the intensity of the sun's rays while they are there. They slow global warming.
...
"If we know how much the aerosols cool, then we can much better quantify how the Earth is going to warm to CO2 because that aerosol-cooling effect is our biggest uncertainty."

In other words, scientists now have a window to peer into the future."

[Sciguy]

It may take years to revise the environmental damage done by the Trump administration, even if Trump loses the 2020 election:

Title: "Trump orders agencies cut environment reviews, citing 'economic emergency'"

https://www.theguardian.com/us-news/2020/jun/04/trump-environment-reviews-cut-economic-emergency

Extract: "The Trump administration continued to weaken core environmental protections in the US by announcing a pair of policies to cut reviews for large infrastructure projects and downplay the health benefits of rules to curb pollution."

If Democrats hold the House, take the Senate, and win the Presidency, which is looking increasingly likely these days, they can use the Congressional Review Act to undo an executive rules finalized after May 19, 2020.  (Republicans did this to several Obama rules, including clean air act rules meant to curtail carbon emissions, in 2017).

https://regulatorystudies.columbian.gwu.edu/upcoming-cra-deadline-has-implications-regulatory-oversight-congress

Upcoming CRA Deadline has Implications for Regulatory Oversight by Congress
Daniel R. Pérez
December 11, 2019   

Download the Commentary (PDF)

In 2017, the 115th Congress made historic use of the Congressional Review Act (CRA), previously described as an “arcane” or “obscure” tool, to eliminate 15 rules issued under the Obama administration. Depending on the outcome of the presidential election next fall, we may see the CRA used again.

Although the 117th Congress won’t convene until January 3, 2021, a looming deadline will affect what regulations they could eliminate using expedited procedures. According to the recently-released 2020 House calendar, any rules issued after May 19, 2020 may be subject to review by the 117th Congress. If Trump is reelected, this may not matter, since he could veto any disapprovals sent to his desk. Yet, statements by Trump administration officials suggest they are aware of the upcoming deadline and acting to finalize high-priority rules before the window opens. Rules issued within the window could face greater risk of being overturned—particularly under the scrutiny of a different group of political principals, depending on the outcome of the 2020 elections. However, agencies will have to weigh the benefit of rushing to publish their rules against the risk of shortchanging the quality of their supporting analyses.

[rboyd]

The pattern in the US for the past few decades has been that the Republicans gut regulations, then the Democrats complain about it but do nothing to reverse the change when elected. Both are the parties of big business. Same goes for tax cuts for the rich, Bush Sr. was the last to raise such taxes and he quickly got the boot.

The last "good" President was Nixon, he brought in the EPA! Then downhill from Reagan (Carter wasn't that good either).

Same unfortunately goes for my own Canada between the Conservatives and the Liberals.

[Sciguy]

The pattern in the US for the past few decades has been that the Republicans gut regulations, then the Democrats complain about it but do nothing to reverse the change when elected. Both are the parties of big business. Same goes for tax cuts for the rich, Bush Sr. was the last to raise such taxes and he quickly got the boot.

The last "good" President was Nixon, he brought in the EPA! Then downhill from Reagan (Carter wasn't that good either).

Same unfortunately goes for my own Canada between the Conservatives and the Liberals.

I think this post illustrates how little foreign observers understand American politics.  While in the broad spectrum of political views, Republicans and Democrats appear pretty similar, in the day to day governing they are very different.  And many of the incremental changes that help millions of people in the US (and around the world) aren't reported in the world press.

Take a look at the small number (out of thousands of regulations imposed during the eight years of the Obama administration) of regulations that were overturned using the Congressional Review Act in 2017:

https://www.npr.org/2017/04/09/523064408/republicans-are-using-an-obscure-law-to-repeal-some-obama-era-regulations

Republicans Are Using An Obscure Law To Repeal Some Obama-Era Regulations

April 9, 2017

The House and Senate have voted to repeal more than a dozen regulations approved in the final six months of Obama's presidency, among them:

    The Interior Department's stream-protection rule, which prevented mountaintop removal coal operations from dumping the rubble into stream valleys.
    The Securities and Exchange Commission's oil anti-corruption rule, which requires energy companies to report payments made to foreign governments.
    The broadband-privacy rule, put in place by the FCC which required Internet service providers to get their subscribers' permission before selling their data to third parties.
    A rule regarding the Alaska National Wildlife Refuges, which, among other things, barred the hunting of bears in Alaska using aircraft.

These rules probably weren't even reported in the foreign press when they were issued.  However, when they were repealed it was big news.  So it's understandable that foreigners might not understand the actual differences between Republican and Democratic administrations. 

[AbruptSLR]

14mm contribution to SLR by both the AIS and GIS between 2003 and 2019 is significant, and is an indication that ice mass loss is beginning to dominate SLR:

Title: "Report: Ice loss from Antarctica and Greenland account for roughly a half-inch of sea level rise between 2003 and 2019"

https://www.tunisiesoir.com/science/report-ice-loss-from-antarctica-and-greenland-account-for-roughly-a-half-inch-of-sea-level-rise-between-2003-and-2019-20782-2020/

Extract: "The results provide insights into how the polar ice sheets are changing, demonstrating definitively that small gains of ice in East Antarctica are dwarfed by massive losses in West Antarctica. The scientists found the net loss of ice from Antarctica, along with Greenland’s shrinking ice sheet, has been responsible for 0.55 inches (14 millimeters) of sea level rise between 2003 and 2019 — slightly less than a third of the total amount of sea level rise observed in the world’s oceans.

The findings come from NASA’s Ice, Cloud and land Elevation Satellite 2 (ICESat-2), which launched in 2018 to make detailed global elevation measurements, including over Earth’s frozen regions. By comparing the recent data with measurements taken by the original ICESat from 2003 to 2009, researchers have generated a comprehensive portrait of the complexities of ice sheet change and insights about the future of Greenland and Antarctica.
 
The study found that Greenland’s ice sheet lost an average of 200 gigatons of ice per year, and Antarctica’s ice sheet lost an average of 118 gigatons of ice per year."

[Hefaistos]

...
"If we know how much the aerosols cool, then we can much better quantify how the Earth is going to warm to CO2 because that aerosol-cooling effect is our biggest uncertainty."

In other words, scientists now have a window to peer into the future."

Counter-intuitive then that the LT temperature anomalies have dropped a lot since the lockdowns started. Satellite data from UAH6 and RSS MSU show the same, and also the CSFR which is a mix of various data sources shows a significant drop starting from March.
These LT temperature data are our best indicators of the thermal energy in the atmosphere.

This drop comes instead of the expected increase due to massively reduced aerosols. Or at least we would expect to see more of a constant temperature anomaly.

The drop is similar to what we had in 2016, coming out of the strong El Nino. Nothing like that provides an explanation this year.

What could the explanation be?
What is the expected increase in forcing from aerosol reduction?

[AbruptSLR]

...
"If we know how much the aerosols cool, then we can much better quantify how the Earth is going to warm to CO2 because that aerosol-cooling effect is our biggest uncertainty."

In other words, scientists now have a window to peer into the future."

Counter-intuitive then that the LT temperature anomalies have dropped a lot since the lockdowns started. Satellite data from UAH6 and RSS MSU show the same, and also the CSFR which is a mix of various data sources shows a significant drop starting from March.
These LT temperature data are our best indicators of the thermal energy in the atmosphere.

This drop comes instead of the expected increase due to massively reduced aerosols. Or at least we would expect to see more of a constant temperature anomaly.

The drop is similar to what we had in 2016, coming out of the strong El Nino. Nothing like that provides an explanation this year.

What could the explanation be?
What is the expected increase in forcing from aerosol reduction?

The linked Copernicus article and the first attached image from Hausfather indicates that May 2020 was the warmest May in recorded history; which then caused Hausfather to increase his projection (see the second attached image) that most likely 2020 will be the warmest year on record (using data thru the end of May 2020).  As CO2 emissions are down for the first five months of 2020; this increases the probability that the associated reduction in anthropogenic aerosol emission due to COVID-19 is contributing to high GMSTAs (in a neutral ENSO year) more than expected by consensus climate models:

Title: "Surface air temperature for May 2020"

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

Extract: "Globally, May was 0.63°C warmer than the average May from 1981-2010, the warmest May in this data record. The last twelve-month period was close to 0.7°C warmer than average, matching the warmest twelve-month period."

[AbruptSLR]

...
If Democrats hold the House, take the Senate, and win the Presidency, which is looking increasingly likely these days, they can use the Congressional Review Act to undo an executive rules finalized after May 19, 2020.  (Republicans did this to several Obama rules, including clean air act rules meant to curtail carbon emissions, in 2017).
...

Politics is a murky business, but the linked article makes the case that most of the Trump administration's environmental rollbacks will take years to be reversed:

Title: "Most Trump environmental rollbacks will take years to be reversed"

https://www.skepticalscience.com/trump-environmental-rollbacks-take-years-to-reverse.html

Extract: "After EPA disbanded its particulate matter scientific review panel, the Union of Concerned Scientists independently brought panel experts together to make recommendations anyway. They concluded that “the current suite of primary fine particle (PM2.5) annual and 24-hour standards are not protective of public health. Both of these standards should be revised to new levels.” EPA’s Clean Air Scientific Advisory Committee, however, set aside those recommendations, and Wheeler has signaled that he does not intend to strengthen the PM2.5 standard. The rule is open for public comments until June 29.

Asked how long it might take a new administration to revise the standard, Goldman of UCS replied that, “We have no real legal precedent for this situation where a legitimate scientific process wasn’t followed. It would probably require another rulemaking process, so a few years at best.”
…
If Biden wins the election, the multi-year rulemaking process to curb pollutants can begin in 2021. The U.S. will have lost valuable time, but could then begin reducing emissions to meet its Paris pledges and seek to re-establish the position it took as a leader in global climate negotiations when Biden was vice president during the Obama administration. Biden likely would need supportive majorities in both the House and the Senate to succeed with such efforts."

[FishOutofWater]

The central and eastern equatorial Pacific has rapidly cooled over the past three months. It may or may not evolve into a La Niña event but increased equatorial upwelling of cool water has cooled the atmosphere over a large area. However, the heat content of the global oceans are at record highs and this upwelling will increase heat uptake by the oceans.

[kassy]

Counter-intuitive then that the LT temperature anomalies have dropped a lot since the lockdowns started.

Looking at the graph it usually goes down in the early part of the year. Biggest peak on these is 2016. Might be a response to the state of winter ice?

And musing on it´s interesting how these peaks are created.
What was the date for the 2016 peak?
What was the date for the 2020 peak?

I think a lot is timing of ice and snow cover because these influence the anomaly most.

We do have a covid drop but we also had a pretty unexpected winter scenario so tying this plot to the covid emission drop is pretty hard.

[Hefaistos]

Counter-intuitive then that the LT temperature anomalies have dropped a lot since the lockdowns started.

Looking at the graph it usually goes down in the early part of the year. Biggest peak on these is 2016. Might be a response to the state of winter ice?

And musing on it´s interesting how these peaks are created.
What was the date for the 2016 peak?
What was the date for the 2020 peak?

I think a lot is timing of ice and snow cover because these influence the anomaly most.

We do have a covid drop but we also had a pretty unexpected winter scenario so tying this plot to the covid emission drop is pretty hard.

1. Thermal energy is strongly down in the atmosphere from February/March, according to all available/updated satellite data. (UAH6, RSS and CFSR). The decline is similar to 2016, when Earth came out of a strong El Nino. No such thing this year. Part of it might be a seasonal effect, but hardly all of it.

2. Aerosols are down a lot. How much? Haven't seen any data yet, but air traffic alone seems to be down 90 % or so. I will make a quick net estimate below, and for the sake of the argument I will guess that aerosols are down by 50%.

3. Forcing from aerosols has been estimated many times, and recent estimates are really high, at -1.14 W/sq.m:

The linked reference, and associated article, indicate that the aerosol-cloud feedback is more negative than previously assumed by consensus climate scientists.  Thus as aerosol emissions decrease (as they have done during the COVID-19 crisis) the Earth will warm faster than previously projected by consensus climate science (such as projected in AR5):
Otto P. Hasekamp et al. Analysis of polarimetric satellite measurements suggests stronger cooling due to aerosol-cloud interactions, Nature Communications (2019). DOI: 10.1038/s41467-019-13372-2
https://www.nature.com/articles/s41467-019-13372-2
"The resulting estimate of RFaciaci = −1.14 Wm−2−2 (range between −0.84 and −1.72 Wm−2−2) is more than a factor 2 stronger than the IPCC estimate that includes also other aerosol induced changes in cloud properties.

4. CO2 levels are at maximum ever, as well as methane. Forcing remains highest ever from CO2 and CO2eq. See attached figure from IPCC. Total forcing is 3.10 W/sq.m.
https://en.wikipedia.org/wiki/Radiative_forcing

Just a quick back of the envelop calculation to sum things up here:
Total forcing including aerosols would then be 3.10 - 1.14 = 1.96
If aerosols are down 50%, we would get an increased net forcing of 3.10 - 0.57 = 2.53
Thus, the net forcing is up from 2.0 to 2.5, or an increase with 25%.

Where is this effect to be seen? Not in the atmosphere, according to point 1.
When the masking effect of aerosols is lifted, we would expect to see an immediate effect on the thermal energy in the atmosphere. But there is no trace of such an effect, au contraire...

[AbruptSLR]

...

Where is this effect to be seen? Not in the atmosphere, according to point 1.
When the masking effect of aerosols is lifted, we would expect to see an immediate effect on the thermal energy in the atmosphere. But there is no trace of such an effect, au contraire...

Per the attached image of Hausfather's projection of the 2020 GMSTA based on data thru May 2020, the effect of reduced aerosol since January 2020 can seen in relatively high surface temperature anomalies (as predicted by models such as those in CMIP6). Furthermore, in the linked article, Hausfather concludes that with regard to differences between troposphere temperature and climate change model projections that: "… there is little evidence to-date that the model/observation differences imply that the climate is less sensitive to greenhouse gases."

Title: "Study: Why troposphere warming differs between models and satellite data"

https://www.carbonbrief.org/study-why-troposphere-warming-differs-between-models-and-satellite-data

Extract: "The most common measure of global temperature rise is here on the Earth’s surface, but scientists also gather data on how temperatures in the atmosphere high above us are changing.
Of particular interest is the troposphere – the lowest layer of the atmosphere where almost all of our weather occurs. To track temperatures, scientists use satellites, which have been providing data since they were first launched in the late 1970s.
Since around the start of the 21st century, the tropospheric warming recorded by satellites has been slower than the rate projected by climate models. In a new study, published in Nature Geoscience, researchers find that these differences are outside the range of what we would expect from natural variability.
…
Ultimately, the paper finds that while there is a mismatch between climate models and observations in the troposphere since the year 2000, there is little evidence to-date that the model/observation differences imply that the climate is less sensitive to greenhouse gases. The results suggest that while these short-term differences between models and observations are a subject of great scientific interest, it does not diminish the reality of long-term human-driven warming."

See also:

Santer, B. D. et al. (2017) Causes of differences in model and satellite tropospheric warming rates, Nature Geoscience, doi:10.1038/ngeo2973

https://www.nature.com/articles/ngeo2973

Abstract
In the early twenty-first century, satellite-derived tropospheric warming trends were generally smaller than trends estimated from a large multi-model ensemble. Because observations and coupled model simulations do not have the same phasing of natural internal variability, such decadal differences in simulated and observed warming rates invariably occur. Here we analyse global-mean tropospheric temperatures from satellites and climate model simulations to examine whether warming rate differences over the satellite era can be explained by internal climate variability alone. We find that in the last two decades of the twentieth century, differences between modelled and observed tropospheric temperature trends are broadly consistent with internal variability. Over most of the early twenty-first century, however, model tropospheric warming is substantially larger than observed; warming rate differences are generally outside the range of trends arising from internal variability. The probability that multi-decadal internal variability fully explains the asymmetry between the late twentieth and early twenty-first century results is low (between zero and about 9%). It is also unlikely that this asymmetry is due to the combined effects of internal variability and a model error in climate sensitivity. We conclude that model overestimation of tropospheric warming in the early twenty-first century is partly due to systematic deficiencies in some of the post-2000 external forcings used in the model simulations.

[Hefaistos]

Counter-intuitive then that the LT temperature anomalies have dropped a lot since the lockdowns started.

I think a lot is timing of ice and snow cover because these influence the anomaly most.

We do have a covid drop but we also had a pretty unexpected winter scenario so tying this plot to the covid emission drop is pretty hard.

More or less the same volume of ice has been molten out in the Arctic during the last 10 years, see attached figure from Gerontocrat. What's "unexpected"?

Still searching for the elusive effect of the reduction in aerosols. A reduction of aerosols is expected to show up quickly in temperature data and in radiative forcings!

We have had three big volcanic eruptions in the recent decades, and there has been almost no time lags involved, when aerosols increased. Mt Pinatubo in June 1991 is the latest one, and well researched. This might serve as a proxy for the current reduction in aerosols.

"Radiative Climate Forcing by the Mount Pinatubo Eruption" by Minnis et al from 1993 says in the Abstract: "The volcanic aerosols caused a strong cooling effect immediately: the amount of cooling increased through September 1991 as shortwave forcing increased relative to longwave forcing."
https://www.researchgate.net/publication/6039761_Radiative_Climate_Forcing_by_the_Mount_Pinatubo_Eruption

[kassy]

1) There was a strong arctic jet keeping the cold air there. That was different from the previous few years.

2) Mount Pinatubo added aerosols that are not there. There is also research that talked about eruptions influencing climate going to certain heights in the atmosphere and it also depends on their location on earth. Can´t quite remember how they relate.

Basically this signal adds blocking in areas where there usually is none so it´s effect is much bigger then a reduction in areas where we make it.

Other factors are the types of pollution. Typical particle size etc. There was a huge drop in China but there were still emissions and as rboyd wrote they have more efficient coal plants.

So basically we first have to work out the usual emission mix. Then the drop and then test it vs some climate system runs and voila we have a paper.

This is the part where i just wait for the paper. Some people should be looking at the shipping lanes because there was already going to be a change there due to policy so they will be the first related papers to show up i think. 

[FishOutofWater]

Low level aerosols do not have the same impacts as stratospheric aerosols caused by volcanic injection of sulfuric acid into the stratosphere. The residence time of aerosols in the stratosphere can be several years after a volcanic eruption. This discussion is off track.

[AbruptSLR]

The linked reference indicates that:

"… current estimates of additional global warming from the permafrost carbon feedback are too low.

J. C. Bowen, C. P. Ward, G. W. Kling and R. M. Cory (09 June 2020), "Arctic amplification of global warming strengthened by sunlight oxidation of permafrost carbon to CO2", Geophysical Research Letters,  https://doi.org/10.1029/2020GL087085

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL087085

Abstract
Once thawed, up to 15% of the ∼1,000 Pg of organic carbon (C) in arctic permafrost soils may be oxidized to carbon dioxide (CO2) by 2100, amplifying climate change. However, predictions of this amplification strength ignore the oxidation of permafrost C to CO2 in surface waters (photomineralization). We characterized the wavelength dependence of permafrost dissolved organic carbon (DOC) photomineralization and demonstrate that iron catalyzes photomineralization of old DOC (4,000‐6,300 a BP) derived from soil lignin and tannin. Rates of CO2 production from photomineralization of permafrost DOC are two‐fold higher than for modern DOC. Given that model predictions of future net loss of ecosystem C from thawing permafrost do not include the loss of CO2 to the atmosphere from DOC photomineralization, current predictions of an average of 208 Pg C loss by 2299 may be too low by ~14%.

Plain Language Summary
The thawing of organic carbon stored in arctic permafrost soils, and its oxidation to carbon dioxide (a greenhouse gas), is predicted to be a major, positive feedback on global warming. However, current estimates of the magnitude of this feedback do not include the oxidation of permafrost soil organic carbon flushed to sunlit lakes and rivers. Here we show that ancient dissolved organic carbon (> 4,000 years old) draining permafrost soils is readily oxidized to carbon dioxide by sunlight. As a consequence, current estimates of additional global warming from the permafrost carbon feedback are too low.

[AbruptSLR]

The linked article indicates that as global socio-economic systems re-open after the COVID-19 initial lockdowns; that anthropogenic GHG emissions are rebounding very quickly, partially due to workers preferring to use cars instead of mass transit for their commutes:

Title: "'Surprisingly rapid' rebound in carbon emissions post-lockdown"

https://www.theguardian.com/environment/2020/jun/11/carbon-emissions-in-surprisingly-rapid-surge-post-lockdown

Extract: "Busier roads to blame, with fears of worse to come as workers shun public transport"

[Lennart van der Linde]

Not sure if this has passed here:
https://www.nature.com/articles/d41586-020-01484-5?fbclid=IwAR0juyzGRJPR8NrXbrFG16D5CuEzWig2EqG3j69tqFvDjsWurgDpn5GB-10

"Short-term tests validate long-term estimates of climate change
Six-hour weather forecasts have been used to validate estimates of climate change hundreds of years from now. Such tests have great potential — but only if our weather-forecasting and climate-prediction systems are unified. How sensitive is climate to atmospheric carbon dioxide levels? For a doubling of CO2 concentration from pre-industrial levels, some models predict an alarming long-term warming of more than 5 °C. But are these estimates believable? Writing in the Journal of Advances in Modeling Earth Systems, Williams et al. have tested some of the revisions that have been made to one such model by assessing its accuracy for very short-term weather forecasts. The results are not reassuring — they support the estimates... their result provides some of the best current evidence that climate sensitivity could indeed be 5 °C or greater. In short, these results, published in a specialist journal, and probably read by few climate policymakers, carry a far-reaching message: we cannot afford to be complacent. It seems that cloud adjustment to climate change is not going to give us breathing space. Instead, we need to redouble our efforts to cut emissions."

Wiliams et al 2020, Use of Short‐Range Forecasts to Evaluate Fast Physics Processes Relevant for Climate Sensitivity:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019MS001986

"Abstract
The configuration of the Met Office Unified Model being submitted to CMIP6 has a high climate sensitivity. Previous studies have suggested that the impact of model changes on initial tendencies in numerical weather prediction (NWP) should be used to guide their suitability for inclusion in climate models. In this study we assess, using NWP experiments, the atmospheric model changes which lead to the increased climate sensitivity in the CMIP6 configuration, namely, the replacement of the aerosol scheme with GLOMAP‐mode and the introduction of a scheme for representing the turbulent production of liquid water within mixed‐phase cloud. Overall, the changes included in this latest configuration were found to improve the initial tendencies of the model state variables over the first 6 hr of the forecast, this timescale being before significant dynamical feedbacks are likely to occur. The reduced model drift through the forecast appears to be the result of increased cloud liquid water, leading to enhanced radiative cooling from cloud top and contributing to a stronger shortwave cloud radiative effect. These changes improve the 5‐day forecast in traditional metrics used for numerical weather prediction. This study was conducted after the model was frozen and the climate sensitivity of the model determined; hence, it provides an independent test of the model changes contributing to the higher climate sensitivity. The results, along with the large body process‐orientated evaluation conducted during the model development process, provide reassurance that these changes are improving the physical processes simulated by the model."

[AbruptSLR]

The linked reference concludes that:

"A mechanism for ozone layer reduction during rapid warming is increased convective transport of ClO. Hence, ozone loss during rapid warming is an inherent Earth system process with the unavoidable conclusion that we should be alert for such an eventuality in the future warming world."

John E. A. Marshall et al. (27 May 2020), "UV-B radiation was the Devonian-Carboniferous boundary terrestrial extinction kill mechanism", Science Advances, Vol. 6, no. 22, eaba0768, DOI: 10.1126/sciadv.aba0768

https://advances.sciencemag.org/content/6/22/eaba0768

Abstract
There is an unexplained terrestrial mass extinction at the Devonian-Carboniferous boundary (359 million years ago). The discovery in east Greenland of malformed land plant spores demonstrates that the extinction was coincident with elevated UV-B radiation demonstrating ozone layer reduction. Mercury data through the extinction level prove that, unlike other mass extinctions, there were no planetary scale volcanic eruptions. Importantly, the Devonian-Carboniferous boundary terrestrial mass extinction was coincident with a major climatic warming that ended the intense final glacial cycle of the latest Devonian ice age. A mechanism for ozone layer reduction during rapid warming is increased convective transport of ClO. Hence, ozone loss during rapid warming is an inherent Earth system process with the unavoidable conclusion that we should be alert for such an eventuality in the future warming world.

[AbruptSLR]

The linked article, and associated linked reference, indicate N20 releases from future permafrost degradation are likely higher than previously assumed by consensus climate science:

Title: "Nitrogen in permafrost soils may exert great feedbacks on climate change"

https://www.eurekalert.org/pub_releases/2020-06/ioap-nip061220.php

Extract: "Decomposition of organic matter is slow in low temperatures. Exacerbating this, there would have to be high competition amongst organisms for what little nitrogen there was in a form that they can use. So there couldn't be much nitrogen left over to contribute to N2O releases.

In recent years however, a growing number of papers have started to hint that there might be very high N2O emissions from such soils, perhaps as much as those from tropical forests or croplands, which suggests that there's a gap in our understanding of what happens to nitrogen in permafrost soils.

To get to the bottom of the issue, Dr. Michael Dannenmann from the Karlsruhe Institute of Technology and Dr. Chunyan Liu from the Institute of Atmospheric Physics at the Chinese Academy of Sciences with their colleagues have established the "NIFROCLIM" project in a high-latitude permafrost region in northeast China that is part of the Eurasian permafrost complex--the world's largest permafrost area."

See also:

Ramm, E., Liu, C., Wang, X. et al. The Forgotten Nutrient—The Role of Nitrogen in Permafrost Soils of Northern China. Adv. Atmos. Sci. (2020). https://doi.org/10.1007/s00376-020-0027-5

https://link.springer.com/article/10.1007/s00376-020-0027-5
https://link.springer.com/content/pdf/10.1007/s00376-020-0027-5.pdf

[AbruptSLR]

Not sure if this has passed here:

https://www.nature.com/articles/d41586-020-01484-5

...

Lennart,

Thanks for this post (noting that I did indeed cite this reference in May, in Replies: #3236 & #3244), as I think that this is a very significant finding that merits more attention than it appears to be getting.

Best,
ASLR

[Lennart van der Linde]

I did indeed cite this reference in May, in Replies: #3236 & #3244

Ah, good, I suspected so, but didn't check carefully. Merits attention indeed.

[AbruptSLR]

Per the linked article it may soon be easier to develop Canadian oilsands than was previously the case:
Title: "Oilsands projects approved by AER would no longer need final stamp from government under new red tape reduction legislation"

https://edmontonjournal.com/news/politics/oil-sands-projects-approved-by-aer-would-no-longer-need-final-stamp-from-government-under-new-red-tape-reduction-legislation/

Extract: "Oilsands projects that get the green light from the Alberta Energy Regulator will go ahead without a final stamp of approval from cabinet if an omnibus bill tabled by the UCP government passes."