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Messages - AbruptSLR

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1
Reply #256 indicates that an increase in Agulhas leakage (see the attached image) contributes to a slowing down of the AMOC (which increased climate sensitivity); and the linked reference confirms that Agulhas leakage is projected to increase with continued anthropogenic global warming:

Tim, N., Zorita, E., Emeis, K.-C., Schwarzkopf, F. U., Biastoch, A., and Hünicke, B.: Influence of position and strength of westerlies and trades on Agulhas leakage and South Benguela Upwelling, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2019-16, in review, 2019.

https://www.earth-syst-dynam-discuss.net/esd-2019-16/

Abstract. The westerlies and trade winds over the South Atlantic and Indian Ocean are important drivers of the regional oceanography around Southern Africa, including features such as the Agulhas current, the Agulhas leakage and the Benguela upwelling. The Agulhas leakage is the transport of warm and saline water from the Indian Ocean into the South Atlantic. The leakage is stronger during intensified westerlies and probably also when the wind systems are shifted poleward. Here we analyzed the wind stress of different observational and modelled atmospheric data sets (covering the last two millennia, the recent decades and the 21st century) with regard to the intensity and position of the south-easterly trades and the westerlies. The analysis reveals that variations of both wind systems go hand in hand. A poleward shift and intensification of westerlies and trades took place during the recent decades. Furthermore, the upwelling in South Benguela slightly intensified and the characteristics of the water masses fed into the upwelling region changed with a poleward shift of the trades. Projections for strength and position of the westerlies in the 21st century depend on assumed CO2 emissions. In the strongest emission scenario a further southward displacement will occur, whereas a northward shift is modelled in the weakest emission scenario, possibly due to the dominating driving effect of ozone recovery. Thus, the Agulhas leakage has intensified during the last decades and is projected to increase if greenhouse gas emission are not reduced. This will have a small impact on Benguela upwelling strength, but will have consequences for water mass characteristics in the upwelling region. An increased contribution of Agulhas water to the upwelling feed water masses will import more preformed nutrients and oxygen into the upwelling region.

2
This is a follow-on post to my Reply #939,  which reviewed selected abstracts from the 2018 WAIS Workshop.  This post provides selected quotes and annotations from somewhat more technical abstracts to better access the current stability of the PIG/Thwaites combined catchment basin, and its risk of transitioning from its current state of a slow MISI-type of collapse to a potentially fast MICI-type of collapse (in the coming decades):

1. Wilson et al. (2018) indicate that with regards to the PIG/Thwaites catchment basin that: " Low mantle viscosity shortens the GIA response time scale from thousands of years, to hundreds or even tens of years."  In this regards I note that: a) the GIA is too slow to pin either the PIG or Thwaites Glacier; b) the high GIA means that early GRACE (gravitational) assessments of ice mass loss from this basin are too low because they did not correct for the mass of magma moving into the basin, and c) the high GIA will result in strong seismic/volcanic activity if/when a MICI-type of collapse occurs.
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/WilsonT2018.pdf

Extract: "Deformation rates measured by GPS in the Amundsen Embayment region are some of the fastest rates ever recorded for glacial isostatic adjustment (GIA).  GIA modeling indicates a very low mantle viscosity, consistent with seismic observations in this region (Barletta et al., 2018).  Low mantle viscosity shortens the GIA response time scale from thousands of years, to hundreds or even tens of years."
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2. Muro et al. (2018), indicate that the bed conditions for the Thwaites Glacier are highly variable.  While consensus sciences like to focus on the sticky bed conditions that might slow the rate of ice mass loss under a MISI-type of future scenario, under a MICI-type of scenario with ice cliff failures initiating near the base of the Thwaites Ice Tongue; such local sticky bed conditions may have little influence on the rate of ice mass loss, as the calved bergy bits would float away from the calving ice face.
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/MutoA2018.pdf

Extract: "Seismic measurements on Thwaites Glacier show a spatially variable bed, with implications for ice-sheet stability. … Modeling suggests that the grounding-line-retreat rate in response to oceanic warming is strongly influenced by such variations in bed character as well as by the topography, highlighting the need for more geophysical surveys to reveal the bed conditions for Thwaites Glacier and other important outlets."
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3. Nakayama et al. (2018) discuss "Pathway of Circumpolar Deep Water into Pine Island and Thwaites ice shelf cavities and to their grounding lines".  They find that: "… submesoscales are formed due to instabilities associated with the positive potential vorticity patches located in the sub ice-shelf mixed layer, particularly near strong topographic features."  Consensus scientists may believe that the influence of such submesoscale vorticity patches is random; however, in my opinion the paleorecord of rapid ice shelf collapse and of grounding line retreat for the PIG and Thwaites Glacier indicate that they submesocale vorticity patches contribute to the formation of groves the promote basal ice melting in these ice shelves.
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/NakayamaY2018.pdf

Extract: "We calculate time-mean and time-evolving fields of velocity and investigate the mechanisms of how CDW is transported into the ice shelf cavities and to their grounding lines. We find a prominent submesoscale variability in the ice cavity, with scales of motion O(1-5km) and Rossby numbers O(1). Preliminary analysis shows that these submesoscales are formed due to instabilities associated with the positive potential vorticity patches located in the sub ice-shelf mixed layer, particularly near strong topographic features."
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4. Parizek et al. (2018)'s work is entitled: "Ice Cliffs: A Region Primed for Enhanced Flow or Failure?", as some consensus scientists were hoping that high stresses upstream of an ice cliff face would accelerate ice thinning sufficiently to inhibit ice cliff failure modes; however, this research indicates that that is not the case.
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/Parizek_B_2018.pdf

Extract: "Therefore, our findings indicate that while higher stresses enhance flow thinning, they do not necessarily cause cliffs to go away."
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5. Bassis et al (2018)'s work is entitled: "Anatomy of the Marine Ice Cliff Instability".  Some consensus scientists have discounted MICI projections on the basis that the physics of this mechanism is not sufficiently understood to be accepted.  In this regards, Bassis et al (2018) use fracture mechanics to better understand: a) the formation of localize rifts that can help destabilize ice shelves and b) detail the mechanics of how tall ice cliffs on grounded marine glacier fail.  Such research is key to getting MICI-types of projections accepted into future consensus science documents like CMIP7 and AR7.

https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/BassisJ2018.pdf

Extract: "We first tested the model by applying it to study the formation of localized rifts in shear zones of idealized ice shelves. These experiments show that wide rifts localize along the shear margins and portions of the ice shelf where the stress in the ice exceeds the yield strength. These rifts decrease the buttressing capacity of the ice shelves, but can also extend to become the detachment boundary of icebergs. Next, application of the model to idealized glaciers shows that for grounded glaciers, failure localizes near the terminus in “serac” type slumping events followed by buoyant calving of the submerged portion of the glacier. The combination of further failure and ductile flow cause the glacier to thin towards buoyancy resulting in a floating ice tongue consisting of yielded ice—similar to what is currently observed at Jakobshavn Glacier in Greenland."
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6. McCormack et al. (2018)'s work is entitled: "The impact of bed elevation resolution on Thwaites Glacier ice dynamics".  Their findings indicate that ice model meshes need to be on the order of 500m in order to adequately represent the ice behavior for the threshold of the Thwaites Glacier.  As most consensus science models have not used this level of mesh resolution, the findings of ice mass loss projections presented in such consensus documents as AR5 cannot be relied upon to adequately characterize the risks of rapid ice mass loss initiation in the Thwaites Glacier threshold region:
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/McCormackF2018.pdf

Extract: "The modeled velocities converge for increasing bed elevation resolution and for most of the basin the differences between the 250 m and 500 m simulation velocities are within 5%, which is within the bounds of uncertainty associated with the velocity datasets used to initialize our model simulations. Our results indicate that a bed elevation of 500 m resolution is sufficient in simulating ice dynamics (velocities, basal shear stresses, strain rates) consistent with those using the higher resolution bed elevation data."

3
Hansen warned that if Canadian tar sands are developed, it is game over for climate change action.

Title: "Canada’s Tar Sands Province Elects a Combative New Leader Promising Oil & Pipeline Revival"

https://insideclimatenews.org/news/18042019/tar-sands-future-alberta-premier-conservative-jason-kenney-pipelines-carbon-tax-trudeau

Extract: "The home province of Canada's tar sands elected a combative, conservative leader this week who came out swinging on the side of the country's struggling oil industry. Jason Kenney promised to cancel Alberta's carbon tax, lift a cap on greenhouse gas emissions from the tar sands and create a "war room" to combat the oil industry's opponents."

4
As those who are serious will look at the abstracts from the 2018 WAIS Workshop (see linked agenda), to better access the current stability of the PIG/Thwaites combined catchment basin, and its risk of transitioning from its current state of a slow MISI-type of collapse to a potentially fast MICI-type of collapse (in the coming decades), in this post I will only provide annotated highlights of key abstracts to better characterize this very real risk:

1. Schroeder et al (2018) indicate that: "… thickness change of the Thwaites Eastern Ice Shelf between 1978 and 2009, revealing the loss of over half of its thickness over the past three decades."  As the Eastern Thwaites Ice Shelf continues to thin, its risk of abrupt collapse increases rapidly in coming decades:
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/SchroederD2018.pdf

2. Hoffman et al (2018) indicate that: "Remote-sensing observations and modeling suggest that marine ice-sheet instability may already be occurring for the Thwaites Glacier Basin, West Antarctica. … our results highlight that glacier speed and ice discharge respond quickly to transient forcing (i.e., climate variability) and changes in ice-front geometry, complicating predictions of ice discharge flux on decadal timescales."  This indicates that while the PIG/Thwaites catchment basin is currently in a MISI-state it could transition to a MICI-state on decadal timescales.
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/HoffmanA2018.pdf

3. Schwans et al (2018) indicate that: "Results demonstrate how the timing and pattern of GL retreat on TG depend on bed character, and highlight key areas of TG’s ice tongue that are critical to its stability on short timescales."  I have previously noted that the most likely location for ice cliff fails to begin in the PIG/Thwaites basin is near the base of the Thwaites Ice Tongue (& once initiated could relatively rapidly spread to adjoining areas after the Thwaites Eastern Ice Shelf collapses); and Schwans et al (2018) confirm the critical risk that ice cliff failure many begin in this location on short-timescales.
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/SchwansE2018_0.pdf

4. Lenaerts et al. (2018) indicate that: "Remote sensing data indicate that the Thwaites Glacier (TG) system has experienced rapidly enhanced solid ice discharge, grounding line retreat on a reverse-sloping bed, and ice shelf thinning since the 1990s. Contemporaneous observations of surface mass balance (SMB) indicate that catchment-wide accumulation has not changed; … Controversially, our analysis indicates that high snowfall events on the TG are not controlled by the Amundsen Sea Low, but are clearly linked to atmospheric blocking at mid-latitudes. This atmospheric pattern, aided by the unique location and geometry of TG, enables intrusion of marine air that originates at lower latitudes."  This indicates that near-term increases in snowfall that could increase the stability of the PIIS and Thwaites Eastern Ice Shelf, is not occurring; however, there is a likely potential that high snowfall rates could occur in the PIG/Thwaites basin in a few decades after the key ice shelves have collapsed and ice failures are occurring (and the increased gravitational driving for of such future snowfall would accelerate any ice cliff failures occurring at that future time).
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/LenaertsJ2018.pdf

5. Neff & Steig (2018) indicate that: "Ice and sediment core data suggest that initiation of ice-shelf retreat and ice loss in the ASE may have been in response to atmosphere-ocean forcing from the strong 1939-42 El Niño. … A deep ice core at Hercules Dome, near where East Antarctica meets West in the Transantarctic Mountains, would provide critical boundary conditions for the magnitude and rate of ice-sheet collapse during the last interglacial period (120-130 kyr)."  This implies that data from the strong 1939-42 El Nino event could be used to better calibrate the risk of rapid grounding line retreat at ice-ocean-atmosphere interfaces as shown in the attached first image for the Hercules Dome site.
https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/NeffP2018.pdf

6. Chu et al. (2018) indicate that:  "These new observations reveal that subglacial water is being actively routed from Bentley trench into the Pine Island Catchment, mirroring ice flow directions. We find that variations in subglacial hydrology instead of small-scale basal roughness explain the location of the western margin of PIG. Through examinations of bed echo characteristics, our results also show that basal water draining from the Bentley Trench flows into an extensive area of distributed water in the upper Pine Island Catchment, but switches to more concentrated flow paths as the water approaches the grounding line. This water transition is similar to one discovered beneath Thwaites Glacier, suggesting t

5
The linked articles discuss: 1) how climate change can increase the number of lightning strikes that cause wildfires, and 2) how the increasing number of intense wildfires can trigger thunderstorms than cause more lightning caused wildfires.  This is a positive feedback mechanism that in under-represented in consensus climate change models:

Title: "Climate change increasing risks of lightning-ignited fires"

https://www.sciencedaily.com/releases/2018/05/180531084415.htm

Extract: "Fires ignited by lightning have and will likely continue to increase across the Mediterranean and temperate regions in the Southern Hemisphere under a warmer climate, according to a new study co-led by a Portland State University researcher.

The study, published online in May in the journal Geophysical Research Letters, examined the observed and forecasted relationship between lightning-ignited fires, rising temperatures across the Southern Hemisphere and natural climate variability in three leading climate drivers that affect weather worldwide: El Niño-La Niña, the Indian Ocean Dipole and the Southern Annular Mode.

Climate change is amplifying climate-fire teleconnections, or the strength of long-distance relationships between weather patterns and fire During the onset of the 21st century, lightning-ignited fires were tightly coupled with upward trends in the SAM and rising temperatures across the Southern Hemisphere

"We think that by having warmer oceans and warmer temperatures in general, we're going to see higher evaporation and heat transfer, and thus higher frequency of convective storms that in turn results in more lightning-ignited fires," Holz said. "And with a climate mode such as SAM stuck in its positive, fire-prone phase that seems to amplify climate change, it doesn't look good.""
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Title: "Here’s an Especially Terrifying New Danger from the Rise in Wildfires"

https://www.motherjones.com/environment/2019/01/heres-an-especially-terrifying-new-danger-from-the-rise-in-wildfires/

Extract: "They can spawn their own thunderstorms, a phenomenon scientists believe can spark additional blazes far away.

… fire-triggered thunderstorms—technically known as pyrocumulonimbus clouds, or “pyroCbs.”"

6
If it isn't measured then nothing will be done about it; thus hopefully decision makers will do something now that Pendrill et al (2019) have improved measurements of the relationship of expanding forestry and agriculture on deforestation and the associated reduction in carbon sinks:

Florence Pendrill et al. (2019), "Agricultural and forestry trade drives large share of tropical deforestation emissions", Global Environmental Change, Volume 56, Pages 1-10, https://doi.org/10.1016/j.gloenvcha.2019.03.002

https://www.sciencedirect.com/science/article/pii/S0959378018314365

Abstract: "Deforestation, the second largest source of anthropogenic greenhouse gas emissions, is largely driven by expanding forestry and agriculture. However, despite agricultural expansion being increasingly driven by foreign demand, the links between deforestation and foreign demand for agricultural commodities have only been partially mapped. Here we present a pan-tropical quantification of carbon emissions from deforestation associated with the expansion of agriculture and forest plantations, and trace embodied emissions through global supply chains to consumers. We find that in the period 2010–2014, expansion of agriculture and tree plantations into forests across the tropics was associated with net emissions of approximately 2.6 gigatonnes carbon dioxide per year. Cattle and oilseed products account for over half of these emissions. Europe and China are major importers, and for many developed countries, deforestation emissions embodied in imports rival or exceed emissions from domestic agriculture. Depending on the trade model used, 29–39% of deforestation-related emissions were driven by international trade. This is substantially higher than the share of fossil carbon emissions embodied in trade, indicating that efforts to reduce greenhouse gas emissions from land-use change need to consider the role of international demand in driving deforestation. Additionally, we find that deforestation emissions are similar to, or larger than, other emissions in the carbon footprint of key forest-risk commodities. Similarly, deforestation emissions constitute a substantial share (˜15%) of the total carbon footprint of food consumption in EU countries. This highlights the need for consumption-based accounts to include emissions from deforestation, and for the implementation of policy measures that cross these international supply-chains if deforestation emissions are to be effectively reduced."

Caption for image: "Fig. 1. Emissions sources for deforestation-related carbon dioxide emissions are diverse and vary by region. Emissions embodied in production are quantified for each commodity group within each country (here summarised by region). A region’s width on the x-axis corresponds to the embodied emissions produced in that region, while the y-axis shows the share of emission attributed to each commodity group within each region, implying that the rectangles within the plot are scaled according to the emissions embodied in each region-commodity combination. The percentages within the rectangles indicate the share of the total (2.6 GtCO2 yr−1) embodied emissions. For forestry products, the results show emissions associated with tree-plantation expansion, but not emissions due to clearing purely for timber without subsequent land-use expansion."

7
I many ways the Arctic is a 'canary in the coal mine' warning of coming rapid climate change as discussed in the linked reference:

Twila A. Moon et al. ( 07 March 2019), "The Expanding Footprint of Rapid Arctic Change", Earth's Future, https://doi.org/10.1029/2018EF001088

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018EF001088

Abstract: "Arctic land ice is melting, sea ice is decreasing, and permafrost is thawing. Changes in these Arctic elements are interconnected, and most interactions accelerate the rate of change. The changes affect infrastructure, economics, and cultures of people inside and outside of the Arctic, including in temperate and tropical regions, through sea level rise, worsening storm and hurricane impacts, and enhanced warming. Coastal communities worldwide are already experiencing more regular flooding, drinking water contamination, and coastal erosion. We describe and summarize the nature of change for Arctic permafrost, land ice, and sea ice, and its influences on lower latitudes, particularly the United States. We emphasize that impacts will worsen in the future unless individuals, businesses, communities, and policy makers proactively engage in mitigation and adaptation activities to reduce the effects of Arctic changes and safeguard people and society."

8
As a follow-on to my last post, I quickly note that PDFs for impacts are currently estimated by integrated assessment modelling (IAM), however, some lead authors of AR5 warn against over relying on the IAM projections included in AR5, see the first linked website.

Title: "Integrated assessment modelling"

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

Extract: "While the Intergovernmental Panel on Climate Change (IPCC) relies heavily on integrated modeling, IPCC Fifth Assessment Report lead author Thomas Bruckner cautions against overinterpreting the results from such modeling."

In addition to the overly simplistic nature of the IAM used by AR5 (such as they ignore interactions between impacting factors such as SLR, tides, storm surge, rainfall runoff, barometric pressures, etc.), but they largely ignore the matter of biocapacity and anthropogenic ecological footprint (see the attached image and the second linked website):

Title: "Earth Overshoot Day"

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

Extract: "(World Biocapacity / World Ecological Footprint ) × 365" 

Footnote: When do you guess that Earth Overshoot Day will occur in 2019?

9
While I have previously cited Sutton (2018) and previously provided the first attached image; about how AR5 could have better communicated climate risk in the 'WGI AR5 Summary', I suspect that it is advisable here to revisit this topic as it may apply to up-coming 'WGI AR6 Summary'. 

First, I note that five of the CMIP6 projections (all from the most advanced ESMs) are citing a most likely value for ECS of at least 5.3K; while in the first image AR5 assumed the most likely value of ECS was about 3K.  Furthermore, while a PDF for ECS from AR6 is not currently available; if one assumes that the most advance CMIP6 ESM projections are correct and translates the PDF for ECS (5.3K-3K) 2.3K to right and assumes the shape of the right-skewed PDF to match that by Marvel et al in the second image [from: Armour (2016)], but shifted 2.3K to the right, then it is easy to understand that the climate risk, this century, from a plausible high-impact scenario (PPHIS) would be tens of times higher than that indicated by Sutton (2018) for the consensus science implied (but not well communicated) by AR5.

Second, if Hansen et al (2016) is correct about the ice-climate feedback (see the third image of the transient impact on Earth's energy imbalance in the coming decades) and SLR risks associated with a potential collapse of the WAIS in the coming decades; then one would need to add these climate risks to those indicated by CMIP6.

Third, as PPHIS climate risk is not only a function of ECS and ice-climate feedbacks, but also anthropogenic forcing pathways, I provide the fourth image showing 2017 consensus climate science projections 2100 GMSTA for low and high forcing scenarios.  As I have previously shown that we could be a 2K GMSTA well before 2040 by following SSP5, and that Pollard, DeConto and Alley (2018) indicate that if we reach 2K GMSTA the WAIS will begin a MICI-type of collapse; we should not feel too comfortable that we will avoid PPHIS cases:

Sutton, R. T. (2018) ESD ideas: a simple proposal to improve the contribution of IPCC WGI to the assessment and communication of climate change risks. Earth System Dynamics, 9 (4). pp. 1155-1158. ISSN 2190-4987 doi: https://doi.org/10.5194/esd-9-1155-2018

https://www.earth-syst-dynam.net/9/1155/2018/

Extract: "I suggest the WGI authors should agree on a modest number of key parameters for which an assessed physically plausible high-impact scenario (PPHIS) or storyline (e.g. Zappa and Shepherd, 2017) can be provided. This should be done for core parameters such as climate sensitivity and TCRE (the transient climate response to cumulative carbon emissions: Allen et al., 2009; Matthews et al., 2009) and could also be done for some large-scale impact-relevant metrics (informed by WGII), such as the magnitude of increases in extreme rainfall.

Below are three examples of how PPHIS could be used by WGI, adapted from the WGI AR5 Summary for Policymakers. In these examples all the information used can be found somewhere within the AR5 report, but the synthesis and communication (including framing) of this information is different.
1.   ECS. It is very unlikely that ECS is greater than 6 ∘C (medium confidence) but this value may be considered a physically plausible high-impact scenario (PPHIS). If realised, such a value for ECS would very likely result in an increase in global mean temperature by 2100 well above 2 ∘C relative to 1850–1900 under all RCP scenarios except RCP2.6 (high confidence).
2.   Sea level. A partial collapse of the marine-based sectors of the Antarctic ice sheet is considered unlikely during the 21st century (medium confidence). However, if realised this PPHIS could cause an additional contribution to sea level rise of up to several tenths of a metre during the 21st century (medium confidence).
3.   Atlantic Meridional Overturning Circulation (AMOC). It is very unlikely that the AMOC will undergo an abrupt transition or collapse in the 21st century for the scenarios considered (medium confidence). However, if it did occur such a transition would have very large rapid (decadal timescale) impacts on the regional climate of the North Atlantic and surrounding continents (high confidence) and substantial impacts on the climate of regions further afield (medium confidence). (More quantitative information on impacts could and should be provided.)"

Caption for first image: "Figure 1A schematic representation of how climate change risk depends on equilibrium climate sensitivity (ECS). (a) A possible likelihood distribution consistent with the IPCC AR5 assessment that “Equilibrium climate sensitivity is likely in the range 1.5 to 4.5 ∘C (high confidence), extremely unlikely less than 1 ∘C (high confidence) and very unlikely greater than 6 ∘C (medium confidence)”. (b) A schematic illustration of the fact that, for a given emissions scenario, the cost of impacts and adaptation rises very rapidly (shown here as an exponential damage function) with ECS. (c) In this example, the resultant risk (quantified here as likelihood × impact) is highest for high ECS values. The precise shape of the risk curve is dependent on assumptions about the shape of the likelihood and damage functions at high sensitivity (Weitzman, 2011) (figure by Ed Hawkins).

10
The linked reference discusses the implications of outburst meltwater discharges from beneath the paleo Pine Island Bay marine glacier, and discusses the implications of these paleo findings on the contemporary marine glaciers (like PIG and Thwaites):

Kirkham, J. D., Hogan, K. A., Larter, R. D., Arnold, N. S., Nitsche, F. O., Golledge, N. R., and Dowdeswell, J. A.: Past water flow beneath Pine Island and Thwaites glaciers, West Antarctica, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-67, in review, 2019.

https://www.the-cryosphere-discuss.net/tc-2019-67/

Abstract. Outburst floods from subglacial lakes beneath the Antarctic Ice Sheet modulate ice flow velocities over periods of months to years. Although subglacial lake drainage events have been observed from satellite altimetric data, little is known about their role in the long term evolution of ice sheet basal hydrology. Here, we systematically map and model past water flow through an extensive area containing over 1000 subglacial channels and 19 former lake basins exposed on over 19,000 km2 of seafloor by the retreat of Pine Island and Thwaites glaciers, West Antarctica. At 560 m wide and 50 m deep on average, the channels offshore of present day Pine Island and Thwaites glaciers are approximately twice as deep, three times as wide, and cover an area over 400 times larger than the terrestrial meltwater channels comprising the Labyrinth in the Antarctic Dry Valleys. The channels incised into bedrock offshore of contemporary Pine Island and Thwaites glaciers would have been capable of accommodating discharges of up to 8.8 × 106 m3 s−1. We suggest that the channels were formed by episodic, high magnitude discharges from subglacial lakes trapped during ice sheet advance and retreat over multiple glacial periods. Our results document the widespread influence of episodic subglacial drainage events during past glacial periods, in particular beneath large ice streams similar to those that continue to dominate contemporary ice-sheet discharge.

Furthermore, I note that in Reply #242, I discuss Smith et al. (2017) that a subglacial lake drainage event from beneath the Thwaites Glacier ended in 2014, and another such drainage event can be expected as soon as 2032 to 2034.

Smith et. al. (2017), "Connected subglacial lake drainage beneath Thwaites Glacier, West Antarctica", The Cryosphere, 11, 451–467, doi:10.5194/tc-11-451-2017

See also, Replies #243 & #673.

11
Wipneus posted (in the 'PIG has calved' thread) a high-resolution version of the attached image of a pair of major cracks/crevasses in the PIIS as captured by the Landsat 8 satellite on April 6, 2019 with a solar elevation of 1.45 degrees.  In previous years when I have observed comparable cracks in the PIIS in the March/April timeframe, a major calving event occurred in July of that year.  If such a major calving event happens this austral winter, it would be a clear indication that the influence of warm CDW on PIIS stability is much stronger than previously assumed by consensus climate scientists.  If so, this may lead to a MICI-type of grounding retreat in the combined Pine Island/Thwaites Glaciers drainage basin than assumed by current glacial models.


12
The fact that permafrost degradation is likely resulting in about twelve times higher nitrous oxide emissions than consensus science assumed, is bad enough; but to me it is worse that the findings cited below are an indication that a cascade of positive feedback mechanisms are currently being activated:

Title: "The warming Arctic permafrost may be releasing more nitrous oxide than previously thought"

https://phys.org/news/2019-04-arctic-permafrost-nitrous-oxide-previously.html

Extract: "Now, a recent paper shows that nitrous oxide emissions from thawing Alaskan permafrost are about twelve times higher than previously assumed. "Much smaller increases in nitrous oxide would entail the same kind of climate change that a large plume of CO2 would cause" says Jordan Wilkerson, first author and graduate student in the lab of James G. Anderson, the Philip S. Weld Professor of Atmospheric Chemistry at Harvard."

See also:

Jordan Wilkerson et al, Permafrost nitrous oxide emissions observed on a landscape scale using the airborne eddy-covariance method, Atmospheric Chemistry and Physics (2019). DOI: 10.5194/acp-19-4257-2019

13
The linked reference indicates a positive feedback mechanism between early spring rainfall over the Arctic Ocean and increasing reduction in Arctic sea ice albedo, initiated by changes in surface ablation caused by the early rain.  This positive feedback mechanism could contribute to the Arctic albedo flip projected by Hansen many years ago:

Dou, T., Xiao, C., Liu, J., Han, W., Du, Z., Mahoney, A. R., Jones, J., and Eicken, H.: A key factor initiating surface ablation of Arctic sea ice: earlier and increasing liquid precipitation, The Cryosphere, 13, 1233-1246, https://doi.org/10.5194/tc-13-1233-2019, 2019.

https://www.the-cryosphere.net/13/1233/2019/

Abstract
Snow plays an important role in the Arctic climate system, modulating heat transfer in terrestrial and marine environments and controlling feedbacks. Changes in snow depth over Arctic sea ice, particularly in spring, have a strong impact on the surface energy budget, influencing ocean heat loss, ice growth and surface ponding. Snow conditions are sensitive to the phase (solid or liquid) of deposited precipitation. However, variability and potential trends of rain-on-snow events over Arctic sea ice and their role in sea-ice losses are poorly understood. Time series of surface observations at Utqiaġvik, Alaska, reveal rapid reduction in snow depth linked to late-spring rain-on-snow events. Liquid precipitation is key in preconditioning and triggering snow ablation through reduction in surface albedo as well as latent heat release determined by rainfall amount, supported by field observations beginning in 2000 and model results. Rainfall was found to accelerate warming and ripening of the snowpack, with even small amounts (such as 0.3 mm recorded on 24 May 2017) triggering the transition from the warming phase into the ripening phase. Subsequently, direct heat input drives snowmelt, with water content of the snowpack increasing until meltwater output occurs, with an associated rapid decrease in snow depth. Rainfall during the ripening phase can further raise water content in the snow layer, prompting onset of the meltwater output phase in the snowpack. First spring rainfall in Utqiaġvik has been observed to shift to earlier dates since the 1970s, in particular after the mid-1990s. Early melt season rainfall and its fraction of total annual precipitation also exhibit an increasing trend. These changes of precipitation over sea ice may have profound impacts on ice melt through feedbacks involving earlier onset of surface melt.

14
Some readers may find the linked reference to provide positive news that if higher GMSTA and increased carbon dioxide concentrations result in more BVOCs then this should result in a feedback mechanism with a net negative radiative forcing contribution.  That said, these finding also indicate that ECS may well have been higher than assumed by consensus science prior to the beginning of the industrial era (circa 1750), as land use change likely resulted in decreased BVOC emissions between 1750 and say 2000.  Also, if we continue following a BAU pathway for several more decades, associated vegetation degradation (say due to excessive GMSTA and abrupt changes in precipitation patterns, and an increase in pests), may result in a future will lower BVOC emissions, rather than higher BVOC emissions:

Sporre, M. K., Blichner, S. M., Karset, I. H. H., Makkonen, R., and Berntsen, T. K.: BVOC–aerosol–climate feedbacks investigated using NorESM, Atmos. Chem. Phys., 19, 4763-4782, https://doi.org/10.5194/acp-19-4763-2019, 2019.

https://www.atmos-chem-phys.net/19/4763/2019/

Abstract
Both higher temperatures and increased CO2 concentrations are (separately) expected to increase the emissions of biogenic volatile organic compounds (BVOCs). This has been proposed to initiate negative climate feedback mechanisms through increased formation of secondary organic aerosol (SOA). More SOA can make the clouds more reflective, which can provide a cooling. Furthermore, the increase in SOA formation has also been proposed to lead to increased aerosol scattering, resulting in an increase in diffuse radiation. This could boost gross primary production (GPP) and further increase BVOC emissions. In this study, we have used the Norwegian Earth System Model (NorESM) to investigate both these feedback mechanisms. Three sets of experiments were set up to quantify the feedback with respect to (1) doubling the CO2, (2) increasing temperatures corresponding to a doubling of CO2 and (3) the combined effect of both doubling CO2 and a warmer climate. For each of these experiments, we ran two simulations, with identical setups, except for the BVOC emissions. One simulation was run with interactive BVOC emissions, allowing the BVOC emissions to respond to changes in CO2 and/or climate. In the other simulation, the BVOC emissions were fixed at present-day conditions, essentially turning the feedback off. The comparison of these two simulations enables us to investigate each step along the feedback as well as estimate their overall relevance for the future climate.

We find that the BVOC feedback can have a significant impact on the climate. The annual global BVOC emissions are up to 63 % higher when the feedback is turned on compared to when the feedback is turned off, with the largest response when both CO2 and climate are changed. The higher BVOC levels lead to the formation of more SOA mass (max 53 %) and result in more particles through increased new particle formation as well as larger particles through increased condensation. The corresponding changes in the cloud properties lead to a −0.43 W m−2 stronger net cloud forcing. This effect becomes about 50 % stronger when the model is run with reduced anthropogenic aerosol emissions, indicating that the feedback will become even more important as we decrease aerosol and precursor emissions. We do not find a boost in GPP due to increased aerosol scattering on a global scale. Instead, the fate of the GPP seems to be controlled by the BVOC effects on the clouds. However, the higher aerosol scattering associated with the higher BVOC emissions is found to also contribute with a potentially important enhanced negative direct forcing (−0.06 W m−2). The global total aerosol forcing associated with the feedback is −0.49 W m−2, indicating that it has the potential to offset about 13 % of the forcing associated with a doubling of CO2.

15
In my last post I underlined a statement by DeConto et al (2018) that major grounding line retreat would occur in the WAIS after GMSTA reaches/exceeds 2K above pre-industrial.  As some readers believe that they are 'protected' from such an occurrence by the fact that many consensus science PDFs put such an event in the fat-right-tailed portion of such consensus PDF.  However, here I note that the longer we stay on a BAU pathway, the more such consensus PDFs shift/skew to the right as indicated by the first image.

Furthermore, the second image shows how a time-dependent PDF for ECS is much more right-skewed than are uncorrected values of ECS base on simple models using observed records from recent decades.  Thus, the more time that passes since pre-industrial anthropogenic forcing began, the higher the value of ECS needs to be used to determine GMSTA.


Finally, for this post, the third image shows that because consensus science claims a high degree of uncertainty about the true value of aerosol feedback, they use both high and low values to form a blended PDF (shown in grey) for use for reporting to decision makers.  However, nature does not use blended PDFs, and many recent studies indicate that aerosol feedback has been more negative in recent decades than previously assumed; which implies the TCR may be significantly higher (per the brown PDF) than consensus science currently assumes.

16
Abstracts of presentations and poster sessions for the 2018 WAIS Workshop can be found at the first following linked website.  From the eight pages of linked abstracts, I have selected three that highlight the risks of MICI types of ice mass loss from the WAIS and I have underlined some sentences that are particularly concerning from these three abstracts (but feel free to post and comment on other abstracts that I did not select):

Title: "WAIS 2018 Agenda"
Title: "Poster Session 1, Monday afternoon: The Vulcan Mind Meld"
Title: "Poster Session 2, Tuesday Afternoon: The Picard Maneuver"

https://docs.google.com/document/d/170BqLjDDVX2cAe0Mr_qwtwTIdPoPtYC6fQYcWB0l7As/edit
&

Title: "Across the Great Divide: The Flow-to-Fracture Transition and the Future of the West Antarctic Ice Sheet", by Richard B. Alley, Byron R. Parizek, Knut Christianson, Robert M. DeConto, David Pollard and Sridhar Anandakrishna

https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/Alley_R.pdf

Abstract: "Physical understanding, modeling, and available data indicate that sufficient warming and retreat of Thwaites Glacier, West Antarctica will remove its ice shelf and generate a calving cliff taller than any extant calving fronts, and that beyond some threshold this will generate faster retreat than any now observed. Persistent ice shelves are restricted to cold environments. Ice-shelf removal has been observed in response to atmospheric warming, with an important role for meltwater wedging open crevasses, and in response to oceanic warming, by mechanisms that are not fully characterized. Some marine-terminating glaciers lacking ice shelves “calve” from cliffs that are grounded at sea level or in relatively shallow water, but more-vigorous flows advance until the ice is close to flotation before calving. For these vigorous flows, a calving event shifts the ice front to a position that is slightly too thick to float, and generates a stress imbalance that causes the ice front to flow faster and thin to flotation, followed by another calving event; the rate of retreat thus is controlled by ice flow even though the retreat is achieved by fracture. Taller cliffs generate higher stresses, however, favoring fracture over flow. Deformational processes are often written as power-law functions of stress, with ice deformation increasing as approximately the third power of stress, but subcritical crack growth as roughly the thirtieth power, accelerating to elastic-wave speeds with full failure. Physical understanding, models based on this understanding, and the limited available data agree that, above some threshold height, brittle processes will become rate-limiting, generating faster calving at a rate that is not well known but could be very fast. Subaerial slumping followed by basal-crevasse growth of the unloaded ice is the most-likely path to this rapid calving. This threshold height is probably not too much greater than the tallest modern cliffs, which are roughly 100 m."
&

Title: "Towards Process-based Models of Marine Ice-cliff instability", by Doug Benn, Jeremy Bassis, Jan Åström, Joe Todd & Thomas Zwinger

https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/Benn_D.pdf

Abstract: "The finite strength of ice places a limit on ice cliff height above sea level (freeboard) (Hanson and Hooke, 2003; Bassis and Walker, 2012). When this height is exceeded, ice cliff failure can occur. This calving mechanism is currently hypothetical, but could become widespread if deep calving cliffs are exposed on marine ice sheets following the disintegration of fringing ice shelves. Runaway ice-cliff failure or the Marine Ice-cliff Instability (MICI) could lead to much more rapid ice loss of the West Antarctic Ice Sheet than the well-established Marine Ice-Sheet Instability (MISI) processes (Pollard et al., 2015; DeConto and Pollard, 2016). It is relatively straightforward to define height thresholds for ice-cliff failure based on field or laboratory measurements of the yield strength of ice, but methods for rates of ice loss remain rudimentary. The current generation of models employs simple rate functions tuned to match observed or prescribed calving rates. Because of the potentially great importance of MICI for future sea-level rise, there is an urgent need for well-founded models of ice cliff instability to enable reliable predictions of ice loss under different forcings.

In this talk, we present preliminary results of investigations into marine ice cliff instability using the Helsinki Discrete Element Model (HiDEM) and Elmer/Ice. We find that the large longitudinal stress gradients at tall ice fronts trigger complex mixed-mode dynamic behaviors, including brittle failure, viscous deformation, and enhanced viscous flow along shear zones. Crucially, brittle and viscous processes are complexly linked: the rate and pattern of fracture development depends on the rheology and stress history of the glacier.  Furthermore, fractures influence the larger scale flow of ice tens of ice thicknesses away from the calving front. This creates considerable challenges for modelling, because approaches that rely on alternating between elastic and viscous models (e.g. Vallot et al., 2018) yield results that depend on time-step size. We shall address this problem using a fully visco-elastic version of HiDEM (in development) to explore how interactions between brittle and viscous processes control rates of ice flow and ice-front retreat where the ice-cliff stability threshold is exceeded. The ultimate aim is to use insights from process-based models to develop parameterizations of MICI for regional scale predictive models."
&

Title: "Climatic Thresholds for WAIS Retreat: Onset of Widespread Ice Shelf Hydrofracturing and Ice Cliff Calving in a Warming World", by Rob DeConto, David Pollard, Knut Christianson, Richard B. Alley & Byron R. Parizek

https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/WAIS2018.pdf

Abstract: "The loss or thinning of buttressing ice shelves and accompanying changes in grounding zone stress balance are commonly implicated as the primary trigger for grounding line retreat, such as that observed in Amundsen Sea outlet glaciers today. Ice-shelf thinning is mostly attributed to the presence of warm ocean waters beneath the shelves. However, climate model projections indicate that summer air temperatures could soon exceed the threshold for widespread meltwater production on ice-shelf surfaces. This has serious implications for the future stability of ice shelves, because they are vulnerable to the propagation of water-induced flexural stresses and water-aided crevasse penetration, often referred to as ‘hydrofracturing’. Once initiated, the rate of shelf loss through hydrofracturing can far exceed that caused by sub-surface oceanic melting, and could result in the complete loss of some buttressing ice shelves, with marine-terminating grounding lines suddenly becoming calving ice fronts. In places where those exposed (unbuttressed) ice fronts are thick enough (>900m), deviatoric stresses can exceed the strength of the ice, and the cliff face will fail through brittle processes leading to rapid calving like that seen in analogous settings on Greenland such as Jakobshavn and Helheim. 
 
Here we explore the implications of hydrofacturing and subsequent ice-cliff collapse in a warming climate, by parameterizing these processes in a hybrid ice sheet-shelf model. Model physical parameters controlling sensitivity of surface crevasse penetration to meltwater and ice-cliff calving rate (a function of cliff height above the stress-balance threshold for brittle failure) are based on observations of calving in analogous settings, and model performance relative to observed mass loss and paleo sea-level estimates. Including these processes and exploring a range of atmospheric and ocean climate forcing scenarios, we find the potential for major future WAIS retreat if global mean temperature rises more than ~2ºC above preindustrial. We also find that strict mitigation, with net negative carbon emissions initiated ~2060 substantially reduces the magnitude and rate of long-term WAIS retreat. In simulations following a ‘worst case’ RCP8.5 scenario, the model produces rates of equivalent sea level rise that would be measured in cm per year by the end of this century. Importantly, parameterized Antarctic calving rates at thick ice fronts are not allowed to exceed those observed in Greenland today. This may be an overly conservative assumption, considering the very different spatial scales and physical settings of Antarctic outlet glaciers like Thwaites. Clearly the potential for mechanical/brittle processes to deliver ice to the ocean, in addition to viscous and basal processes, needs to be better constrained through more complete, physically based model representations of calving."

Edit, for those who do not understand the implications of Alley et al. (2018)'s comment that ice deformation is a power-function of stress, I attach an image that translates this underlying ice-cliff behavior into terms of calving rate (deformation) per year for various values of marine glacier freeboard (ice face height minus water depth) and relative water depth (which combine determine the primary stresses near the ice cliff face).

17
W.r.t. the linked article on the rapid pace of climate change in the Bering Sea, I note that the author fails to point out the clear telecommunication link between the Tropical/Equatorial Pacific Ocean and the Bering Sea.  This telecommunication link indicates that a rapid pace of climate change in the Bering Sea (& of the associated PDO index) indicates that the ENSO cycle is moving rapidly towards more frequent El Nino events and less frequent La Nina events; which is an indication that ECS is relatively high (say in the 5 K range, & see the three attached images):

Title: "Pace of Bering Sea changes startles scientists"

https://apnews.com/0c9a94b339974e9ca9d860fa180d45ea

Extract: "Winter storm surge flooding is the latest indication that something’s off-kilter around the Bering Strait, the gateway from the Pacific Ocean to the Arctic Ocean. Rapid, profound changes tied to high atmospheric temperatures, a direct result of climate change, may be reordering the region’s physical makeup. Ocean researchers are asking themselves if they’re witnessing the transformation of an ecosystem.

The Bering Sea last winter saw record-low sea ice. Climate models predicted less ice, but not this soon, said Seth Danielson, a physical oceanographer at the University of Alaska Fairbanks.

“The projections were saying we would’ve hit situations similar to what we saw last year, but not for another 40 or 50 years,” Danielson said."

18
...
It is especially useful for non-scientists and newbies.

Many readers seem to think of the topic of catastrophic climate change as if it were Pandora's Box, and if they do not look at the topic then they will be safe from all of the climate risks within.  Unfortunately, Pandora's Box (or Markov's Blanket) is actually the fact that most of mankind is unwilling to face the reality of nature, and they prefer to living in their own preconditioned dreamworld where, in their minds, they cannot be held accountable for anthropogenic climate change, including its fat right tail.  This actual Pandora's Box (Markov's Blanket) effectively inhibits the enactment of measures (like worldwide regulations and progressive carbon taxes) that would maintain appropriate margins of safety (e.g. see the linked article which errs on the side of least drama [ESLD]); and it effectively inhibits/delays legal action that could be taken using whatever laws exist to protect society against such unreasonably low margins of safety:

Title: "Climate study warns of vanishing safety window—here’s why"

https://www.nationalgeographic.com/environment/2019/03/climate-change-model-warns-of-difficult-future/

Extract: "Millions of possible scenarios were analyzed, and only a few are acceptable, the scientists said.

Global emissions are currently over 40 billion tons a year and increased the last two years. Meanwhile the International Energy Agency announced on March 11 that oil consumption will continue to grow over the next five years, driven by increased demand for jet fuel and petrochemicals."

Edit, see also:

Title: "There’s Just 1 Reason Republican Politicians Are Fully Attacking The Green New Deal"

https://cleantechnica.com/2019/04/07/theres-just-1-reason-the-right-is-fully-attacking-the-green-new-deal/

Extract: "There is so much noise in politics. Some politicians — and perhaps even some political parties — live on that noise. The United States has a horrible voter turnout rate.

Additionally, the Republican Party has demonstrated in numerous cases that it is extremely eager to limit voting and make it harder.

The Green New Deal — which of course isn’t a specific policy proposal, simply a broad vision of how the US should live up to its duties on a topic that threatens the future of human society — actually has broad support of Americans. If you explain it to them, it’s completely logical and easy to get behind.

That’s why it gets attacked so vociferously by the political right wing. It is a threat to polluting energy sources and people like it — people like the idea of clean energy, clean air, clean water, and a more pleasant and livable future with a higher quality of life."

19
Methane emissions from ice sheets are currently ignored by consensus climate science, but the linked reference (& associated linked article) demonstrate that the Greenland Ice Sheet releases significant quantities of methane, and the researchers suspect that the Antarctic Ice Sheet is potentially an even larger source of methane emissions:

Guillaume Lamarche-Gagnon et al. Greenland melt drives continuous export of methane from the ice-sheet bed, Nature (2018). DOI: 10.1038/s41586-018-0800-0

https://www.nature.com/articles/s41586-018-0800-0

Abstract: "Ice sheets are currently ignored in global methane budgets. Although ice sheets have been proposed to contain large reserves of methane that may contribute to a rise in atmospheric methane concentration if released during periods of rapid ice retreat, no data exist on the current methane footprint of ice sheets. Here we find that subglacially produced methane is rapidly driven to the ice margin by the efficient drainage system of a subglacial catchment of the Greenland ice sheet. We report the continuous export of methane-supersaturated waters (CH4(aq)) from the ice-sheet bed during the melt season. Pulses of high CH4(aq) concentration coincide with supraglacially forced subglacial flushing events, confirming a subglacial source and highlighting the influence of melt on methane export. Sustained methane fluxes over the melt season are indicative of subglacial methane reserves that exceed methane export, with an estimated 6.3 tonnes (discharge-weighted mean; range from 2.4 to 11 tonnes) of CH4(aq) transported laterally from the ice-sheet bed. Stable-isotope analyses reveal a microbial origin for methane, probably from a mixture of inorganic and ancient organic carbon buried beneath the ice. We show that subglacial hydrology is crucial for controlling methane fluxes from the ice sheet, with efficient drainage limiting the extent of methane oxidation to about 17 per cent of methane exported. Atmospheric evasion is the main methane sink once runoff reaches the ice margin, with estimated diffusive fluxes (4.4 to 28 millimoles of CH4 per square metre per day) rivalling that of major world rivers. Overall, our results indicate that ice sheets overlie extensive, biologically active methanogenic wetlands and that high ates of methane export to the atmosphere can occur via efficient subglacial drainage pathways. Our findings suggest that such environments have been previously underappreciated and should be considered in Earth’s methane budget."

See also:
Title: "Melting ice sheets release tons of methane into the atmosphere, study finds"

https://phys.org/news/2019-01-ice-sheets-tons-methane-atmosphere.html

Extract: "The Greenland Ice Sheet emits tons of methane according to a new study, showing that subglacial biological activity impacts the atmosphere far more than previously thought.

Professor Jemma Wadham, Director of Bristol's Cabot Institute for the Environment, who led the investigation, said: "A key finding is that much of the methane produced beneath the ice likely escapes the Greenland Ice Sheet in large, fast flowing rivers before it can be oxidized to CO2, a typical fate for methane gas which normally reduces its greenhouse warming potency."

Lead author, Guillaume Lamarche-Gagnon, from Bristol's School of Geographical Sciences, said: "What is also striking is the fact that we've found unequivocal evidence of a widespread subglacial microbial system. Whilst we knew that methane-producing microbes likely were important in subglacial environments, how important and widespread they truly were was debatable. Now we clearly see that active microorganisms, living under kilometres of ice, are not only surviving, but likely impacting other parts of the Earth system. This subglacial methane is essentially a biomarker for life in these isolated habitats."

With Antarctica holding the largest ice mass on the planet, researchers say their findings make a case for turning the spotlight to the south. Mr Lamarche-Gagnon added: "Several orders of magnitude more methane has been hypothesized to be capped beneath the Antarctic Ice Sheet than beneath Arctic ice-masses. Like we did in Greenland, it's time to put more robust numbers on the theory.""

20
As a follow-on to my last post, I provide the two attached images of how warm CDW can contact marine sediment in the Southern Ocean that might contain methane hydrates (and the heat in the warm CDW may degrade any surface zone of methane hydrate in the contacted local seafloor).

First, warm CDW water enter the Weddell Gyre from the north and then travels along the coast of the Queen Maud Land, as shown in the first image from the following website for the Andrex project that is actively monitoring this behavior:

http://www.noc.soton.ac.uk/ooc/PROJECTS/andrex/

The caption for the first image is:

"Schematic of the circulation in the Weddell Sea (in black). The red arrows represent the escape route from the Weddell Sea. The white arrows are the eastern branches of the Weddell Gyre."

Furthermore, if it is not clear, in the image the white arrows should indicate warm CDW entrained in the eastern end of the Weddell Gyre from the ACC to the north.

Second, upwelling of CDW can bring warm water in contact with the coastal seafloor as shown in the second image.

Edit:

The third image shows that in addition to the Weddell Gyre that is also the Ross Gyre and the Un-named Gyre that bring warm CDW into contact with the coastal seafloor in different parts of Antarctica.

21
The first two attached images related to the Antarctic ozone hole come from the linked web article; and the first attached image gives an idea of the size of the Antarctic ozone hole; while the second attached image shows where the ozone layer exists in a typical atmosphere.

http://www.mnn.com/green-tech/research-innovations/blogs/joe-farman-ozone-hole-discoverer-dies-at-82#

Another positive feedback mechanism particular to the Antarctic, that is not being captured by CMIP5 projections, is the feedback between the recent increase in warm CDW volume and the recent increase upper tropospheric methane concentration over East Antarctica (also see discussion in several other threads including the "Methane" thread and the "Southern Ocean" thread).

 As I have posted on in multiple threads: (a) the volume of warm CDW in the Southern Ocean has been increasing; (b) the current ozone hole occurrence over Antarctica is driving circumpolar winds and associated circumpolar currents to the south thus inducing more upwelling of warm CDW onto the continental shelf; and (c) the reduced production of AABW is entraining a smaller volume of CDW thus resulting in an increased age of the CDW.  The result of the increase volume of warm CDW crowded toward the south means that the thickness of the CDW water layer flowing on to the continental shelf is increasing, resulting in an increasing amount of methane hydrate decomposition.

As shown in the third attached figure, unlike the Arctic that has a convex geopotential height topology which tends to disperse local methane emissions; the Antarctic has a concave geopotential height topology which tends to concentrate any local methane emissions (such as the marine methane hydrate emissions cited above) over the South Pole area (see the fourth image).  Furthermore, the extreme cold over the East Antarctic reduces the rate of chemical oxidation of the methane to carbon dioxide thus resulting in a further concentration of methane in the troposphere over the East Antarctic.  However, as GHG contributes to the concavity of the geopotential height topology over Antarctica; this provides a positive feedback mechanism to further accelerate (or at least maintain) the velocity of the circumpolar winds, which should increase the circumpolar current velocity (as well as moving it to the south); which should push more warm CDW onto the Antarctic continental shelf thus decomposing more methane hydrate; and resulting in an increased rate of local ice sheet mass loss and an increased probability of the collapse of the WAIS this century.

22
As indicated by the first two attached images (the first image shows that ECS for E3SMv1 was equal to or less than that for five ESM projections; while the second image shows that for E3SMv1 not only is the ECS value near 5.3C but the value for TCR is near 2.93C), it is highly likely that CMIP6 will support higher ranges for both TCR & ECS than for the consensus climate science ranges cited in AR5 (which were used to estimate the remaining carbon budget at that time).  The following provides random thoughts as to why the likely CMIP6 findings are probably a better representation of our current climate risks.

With regards to CMIP5's input to AR5's climate sensitivity estimates
:
1.   CMIP5 underestimated the stratospheric (including from water vapor & methane) contributions to radiative forcing.
2.   CMIP5 likely underestimated the negative forcing from indirect aerosol feedback mechanisms.
3.   CMIP5 used estimated atmospheric GHG concentrations while CMIP6 uses estimated GHG emissions.
4.   The CMIP6 Earth System Models are more advanced than the CMIP5 models, such as including input from permafrost degradation that CMIP5 ignored (& better assessment of interactions between various feedback mechanisms).
5.   CMIP6 includes the impacts of some freshwater hosing feedback mechanisms while CMIP5 did not include any.

With regards to AR5's paleo-record input to climate sensitivity estimates
:
1.   AR5 likely did not adequately correct for Land Use Changes when estimating climate sensitivity since the Neolithic period.
2.   AR5 likely ESLD when accounting for the negative feedback from natural VOC's and their associated SOCs.

With regards to AR5's observed record input to climate sensitivity estimates:
1.   AR5 assumed GHG emissions efficacy (including location of emissions & interaction with anthropogenic aerosols) values that ESLD.
2.   AR5 blended together values of climate sensitivity calculated by different methods without correcting these differently defined values of climate sensitivity to a common definition.


23
This is just a quick reminder that if/when the WAIS collapses this century, the altitude of the associated land surface will drop to sea level; which would immediately increase Antarctic Amplification (see the linked article); without any consideration of changes in albedo:

Title: "Land height could help explain why Antarctica is warming slower than the Arctic"

https://phys.org/news/2017-05-height-antarctica-slower-arctic.html

Extract: "Temperatures in the Arctic are increasing twice as fast as in the rest of the globe, while the Antarctic is warming at a much slower rate. A new study published in Earth System Dynamics, a journal of the European Geosciences Union, shows that land height could be a "game changer" when it comes to explaining why temperatures are rising at such different rates in the two regions."

See also:

Marc Salzmann, The polar amplification asymmetry: role of Antarctic surface height, Earth System Dynamics (2017). DOI: 10.5194/esd-8-323-2017


24
Reply #576 on: February 06, 2019, 08:17:33 PM
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg188317.html#msg188317
Quote
Both DeConto and Pollard were originally co-authors on the new paper. They later recused themselves because they felt the results coming from Edwards’s statistical model were not consistent with what they were seeing from their own physics-based glacier model.

Thanks!

See also Reply #705:

On Edwards et al 2019:
'The claim that MICI is "not necessary" to reproduce past sea level high stands is both not really true and not really useful. The uncertainty range about what could have been the contribution of Antarctica to sea level during the Pliocene is 5-20 m and during the Last Interglacial it is 3.6-7.4 m. DeConto and Pollard’s model without MICI can reproduce up to 6 m and 5.5 m respectively for these two period (see Edwards et al. E.D. Fig. 4). So yes it can reproduce the lower part of the ranges. But most of the Pliocene range cannot be reproduced with the no-MICI assumption. What the figure shows is that the model with MICI covers a much bigger par of the possible Antarctic contribution for these periods. And still, even including MICI, the model can only explain a maximum of 12 m contribution for the Pliocene. Which means additional mechanisms would be necessary to cover the whole range of possible Antarctic contribution for that period. The claim that MICI is “not necessary” is also not very useful practically because projections with MICI are used to make high-end sea level scenarios. The important information is then is it possible or not? If it was not possible then it would be good news and decision makers wouldn't need to take it into account. "Not necessary" only has an impact on low-end scenarios, for which MICI would already not be used anyways.'

25
This is just a reminder that most consensus science climate models do not do a good job of matching the observed increase of upwelling of relatively warm CDW (circumpolar deep water):

L Bruce Railsback (February 11, 2019), "Sidedness of Divergence as a Key to Understanding Southern Ocean Upwelling in the Overturning Circulation of the Oceans", Modern Approaches in Oceanography and Petrochemical Sciences, Volume 2 - Issue 4, DOI: 10.32474/MAOPS.2019.02.000143

https://lupinepublishers.com/ocean-journal/fulltext/sidedness-of-divergence-as-a-key-to-understanding-southern-ocean.ID.000143.php

Abstract: "Sidedness of divergence helps resolve a present discordance in our understanding of upwelling in the Southern Ocean, and thus it contributes to the evolving recognition of the oceans’ overturning circulation. Divergence can be two-sided (one water mass rises and moves apart in two flows, as is commonly envisioned) or one-sided (one water mass rises and moves away from another that does not move in the opposite direction). Upwelling in the Southern Ocean can be envisioned as a one-sided divergence north of a two-sided divergence. In the more northern one-sided divergence, deep to intermediate waters above or from North Atlantic Deep Water (NADW) upwell into the Antarctica Circumpolar Current (ACC) and move north. In the more southern and two-sided divergence, North Atlantic Deep Water (NADW) upwells and diverges southward into the Antarctic Coastal Current (ACoC) or Polar Current (PC) and northward into the ACC, mixing with the waters upwelled in the northern divergence. Understanding the northern upwelling as one-sided and the southern as two-sided thus eliminates an either/or conundrum that has evolved in the literature. It also allows the two modes of Southern Ocean upwelling (northern in the ACC and southern in the Antarctic Divergence) to be seen in the same comparative light as the two modes of upwelling postulated at global scale (upwelling in the Southern Ocean and upwelling or vertical mixing in the Indo-Pacific): in each comparison, the former involves the greater flux of water, whereas the latter involves water richer in geochemical tracers indicative of greater time and/or distance traveled at depth."
&

Title: "Ocean upwelling and increasing winds"

https://phys.org/news/2015-09-ocean-upwelling.html

Extract: "We show that the intensity with which CDW is upwelling onto the west Antarctic Peninsula today has not occurred for ~7,000 years. We also determine that CDW upwelling was even greater between 9,700 and 7,000 years ago, a time when the southern westerly wind belt was in a more southerly position than present. Our records therefore substantiate the close coupling of intensified/more poleward southern westerly winds with enhanced penetration of warm CDW onto the west Antarctic Peninsula continental shelf.

Given the response of CDW upwelling to modest Holocene climate variability demonstrated here, we conclude that continued intensification and poleward migration of the southern westerly winds in coming decades will further intensify warm-water upwelling onto the west Antarctic Peninsula continental shelf. Greater CDW upwelling will threaten ice shelf stability and limits the capacity of the Southern Ocean to act as a sink for anthropogenic CO2."

26
Quote
Title: "EIA's Annual Energy Outlook 2019 projects growing oil, natural gas, renewables production"
https://www.eia.gov/todayinenergy/detail.php?id=38112
That graph, ASLR, is depressing.  Renewables need to climb 2 orders of magnitude beyond the EIA's expectations to serious displace oil & gas.  The only good news is that the EIA is likely underestimating renewables - I hope by 2 orders of magnitude!

Not to be a 'Doubting Thomas', but unless fossil fuel production is restricted (by regulation and/or by progressive tax) why wouldn't the circa 10 billion people on the planet in 2050 use both the EIA projected fossil fuel production as well as all of the renewable energy supplies that you are envisioning (including for refrigeration/cooling, air travel and increased standards of living for the underdeveloped populations)?

27
As my last post did not address unconventional fossil fuel reserves e.g. (oil/tar sands, oil/gas shales):

Title: "Unconventional Fossil Fuels Factsheet"

http://css.umich.edu/factsheets/unconventional-fossil-fuels-factsheet
&
http://css.umich.edu/sites/default/files/Unconventional_Fossil_Fuels_Factsheet_CSS13-19_e2018.pdf

Extract: "Globally, fossil fuels supply 81% of primary energy. In 2017, 80% of U.S. primary energy consumption came from fossil fuels. Conventional and unconventional fossil fuels differ in their geologic locations and accessibility; conventional fuels are often found in discrete, easily accessible reservoirs, while unconventional fuels may be found within pore spaces throughout a wide geologic formation, requiring advanced extraction technologies. If unconventional oil resources (oil shale, oil sands, extra heavy oil, and natural bitumen) are taken into account, the global oil reserves quadruple current conventional reserves. The price of crude oil increased 223% from 2000 to 2013, making unconventional fossil fuels more cost-competitive. However, in 2017, the price of crude oil fell to $50.8 per barrel from its 2013 peak of $97.98. The Energy Policy Act of 2005 includes provisions to promote U.S. oil sands, oil shale, and unconventional natural gas development."

28
When the fossil fuel industry is actively adding to oil & gas proven reserves and production, it is difficult for me to believe that any of the Paris Agreement goals will be met:

Title: "EIA's Annual Energy Outlook 2019 projects growing oil, natural gas, renewables production"

https://www.eia.gov/todayinenergy/detail.php?id=38112

The first image shows the EIA's January 2019 US Oil & Gas production projections through 2050.
The second image shows BP's estimates of years of remaining fossil fuels assuming consumption at 2015 rates and estimated reserves per 2016 (I note that this only shows conventional reserves).

29
For those who are interested, the following links provide access to information from the CMIP6 Model Analysis Workshop from March 25-28, 2019 in Barcelona:

Title: Abstract Book for Poster Presentations"

https://cmip6workshop19.sciencesconf.org/data/AbstractBook.pdf
&

Title: "Poster slides from the CMIP6 Workshop"

https://cmip6workshop19.sciencesconf.org/data/Session2_PosterSlides.pdf

The attached image from the post by Axel Lauer, Veronika Eyring, and Manuel Schlund indicates that some of the preliminary CMIP6 models have ECS values over 5.5C.

30
Hansen warned consensus climate scientists not to over emphasize the carbon sink associated with the multidecadal spurt of climate change induced plant growth, such as the observed 'Arctic greening'.  Now, recent research (see linked articles) indicates that substantial parts of the Arctic are turning brown due to a combination of extreme weather, invasive insects and increased wildfires.  If (as is likely) this Arctic browning trend continues, not only will much of the sequestered carbon be returned to the atmosphere, but also the associated reductions in albedo will act as a positive feedback from more global warming:

Title: "Climate change made the Arctic greener. Now parts of it are turning brown."

https://www.sciencenews.org/article/climate-change-arctic-browning

Extract: "Warming trends bring more insects, extreme weather and wildfires that wipe out plants

For more than 35 years, satellites circling the Arctic have detected a “greening” trend in Earth’s northernmost landscapes. Scientists have attributed this verdant flush to more vigorous plant growth and a longer growing season, propelled by higher temperatures that come with climate change. But recently, satellites have been picking up a decline in tundra greenness in some parts of the Arctic. Those areas appear to be “browning.”"
&

Title: "Extreme Weather Is Turning the Arctic Brown, Signaling Ecosystem’s Inability to Adapt to Climate Change"

https://www.smithsonianmag.com/smart-news/extreme-weather-turning-arctic-brown-signaling-ecosystems-inability-adapt-climate-change-180970896/

Extract: "Vegetation affected by extreme warming absorbs up to 50 percent less carbon than healthy green heathland"


31
The linked article indicates that the oil & gas industry are succeeding to ensure that oil and gas supplies exceed demand for many years to come:

Title: "Companies are finding lots of oil again"

https://www.axios.com/oil-discovery-increase-2019-72761320-0cbe-4ae3-942a-a815e69f1fe6.html

Extract: "The oil industry is finding lots of hydrocarbons thus far in 2019, putting discoveries on pace to grow by 30% this year if they keep it up, the consultancy Rystad Energy said this week.

The push for substantial new discoveries shows no signs of slowing down, with another 35 high impact exploration wells expected to be drilled this year, both onshore and offshore," Rystad wrote.

Bigger-than-expected U.S. shale growth has also eased concerns.

"Forecasts of a supply gap persist, but they’re being pushed further out into the future," Bloomberg reported in late January, and IEA has warned against complacency."

32
If nothing else, the findings of the linked reference could be used to better calibrate state-of-the-art ESM climate change projections w.r.t. the risks of future 'extreme ocean anoxic event conditions':

D. Hülse, S. Arndt, A. Ridgwell (15 March 2019), "Mitigation of Extreme Ocean Anoxic Event Conditions by Organic Matter Sulfurization", Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2018PA003470

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018PA003470

Abstract
Past occurrences of widespread and severe anoxia in the ocean have frequently been associated with abundant geological evidence for free hydrogen sulfide (H2S) in the water column, so‐called euxinic conditions. Free H2S may react with, and modify, the chemical structure of organic matter settling through the water column and in marine sediments, with hypothesized implications for carbon sequestration. Here, taking the example of Ocean Anoxic Event 2, we explore the potential impact of organic matter sulfurization on marine carbon and oxygen cycling by means of Earth system modeling. Our model experiments demonstrate that rapid sulfurization (ksulf≥ = 105 M−1 year−1) of organic matter in the water column can drive a more than 30% enhancement of organic carbon preservation and burial in marine sediments and hence help accelerate climate cooling and Ocean Anoxic Event 2 recovery. As a consequence of organic matter sulfurization, we also find that H2S can be rapidly scavenged and the euxinic ocean volume reduced by up to 80%—helping reoxygenate the ocean as well as reducing toxic H2S emissions to the atmosphere, with potential implications for the kill mechanism at the end‐Permian. Finally, we find that the addition of organic matter sulfurization induces a series of additional feedbacks, including further atmospheric CO2 drawdown and ocean reoxygenation by the creation of a previously unrecognized net source of alkalinity to the ocean as H2S is scavenged and buried.

33
If nothing else, the findings of the linked reference could be used to better calibrate state-of-the-art ESM climate change projections w.r.t. 'the role of the Southern Ocean in abrupt transitions and hysteresis' in the MOC:

Sophia K.V. Hines, Andrew F. Thompson, Jess F. Adkins (15 March 2019), "The Role of the Southern Ocean in Abrupt Transitions and Hysteresis in Glacial Ocean Circulation", Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2018PA003415

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018PA003415

Abstract: "High‐latitude Northern Hemisphere climate during the last glacial period was characterized by a series of abrupt climate changes, known as Dansgaard‐Oeschger events, which were recorded in Greenland ice cores as shifts in the oxygen isotopic composition of the ice. These shifts in inferred Northern Hemisphere high‐latitude temperature have been linked to changes in Atlantic meridional overturning strength. The response of ocean overturning circulation to forcing is nonlinear and a hierarchy of models have suggested that it may exist in multiple steady state configurations. Here, we use a time‐dependent coarse‐resolution isopycnal model with four density classes and two basins, linked by a Southern Ocean to explore overturning states and their stability to changes in external parameters. The model exhibits hysteresis in both the steady state stratification and overturning strength as a function of the magnitude of North Atlantic Deep Water formation. Hysteresis occurs as a result of two nonlinearities in the model—the surface buoyancy distribution in the Southern Ocean and the vertical diffusivity profile in the Atlantic and Indo‐Pacific basins. We construct a metric to assess circulation configuration in the model, motivated by observations from the Last Glacial Maximum, which show a different circulation structure from the modern. We find that circulation configuration is primarily determined by North Atlantic Deep Water density. The model results are used to suggest how ocean conditions may have influenced the pattern of Dansgaard‐Oeschger events across the last glacial cycle."

34
For those of you who are interested in the topic of natural gas hydrates, you can review the multiple papers linked at the following website for the 2018 Active Special Issues in JGR: Solid Earth on: "Gas Hydrates in Porous Media: Linking Laboratory and Field Scale Phenomena":

https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)2169-9356.HYDRATE1


35
As I raised the topic of the South Atlantic Anomaly in at least Replies #113, 115, 161, 167, 168, 170, 172, 175 and 442, I provide a linked a recent reference on this topic:

Nasuddin, K. A., Abdullah, M., and Abdul Hamid, N. S.: Characterization of the South Atlantic Anomaly, Nonlin. Processes Geophys., 26, 25-35, https://doi.org/10.5194/npg-26-25-2019, 2019.

https://www.nonlin-processes-geophys.net/26/25/2019/

Abstract
This research intends to characterize the South Atlantic Anomaly (SAA) by applying the power spectrum analysis approach. The motivation to study the SAA region is due to its nature. A comparison was made between the stations in the SAA region and outside the SAA region during the geomagnetic storm occurrence (active period) and the normal period where no geomagnetic storm occurred. The horizontal component of the data of the Earth's magnetic field for the occurrence of the active period was taken on 11 March 2011 while for the normal period it was taken on 3 February 2011. The data sample rate used is 1 min. The outcome of the research revealed that the SAA region had a tendency to be persistent during both periods. It can be said that the region experiences these characteristics because of the Earth's magnetic field strength. Through the research, it is found that as the Earth's magnetic field increases, it is likely to show an antipersistent value. This is found in the high-latitude region. The lower the Earth's magnetic field, the more it shows the persistent value as in the middle latitude region. In the region where the Earth's magnetic field is very low like the SAA region it shows a tendency to be persistent.

36
The linked reference (& associated linked articles) discusses linkages between natural VOCs and anthropogenic aerosols in producing secondary organic aerosols, SOAs, and recommends that climate models be updated to include their new findings, particularly regarding cloud formation.  At best this will improve future climate projections; while at worse it may indicate that there is not a surplus of SOAs, so that any future reduction in SOAs (say due to deforestation and/or a reduction in anthropogenic aerosol emissions) may result in a reduction of low altitude clouds, which would then result in an increase in ECS:

Gordon McFiggans, Thomas F. Mentel, Jürgen Wildt, Iida Pullinen, Sungah Kang, Einhard Kleist, Sebastian Schmitt, Monika Springer, Ralf Tillmann, Cheng Wu, Defeng Zhao, Mattias Hallquist, Cameron Faxon, Michael Le Breton, Åsa M. Hallquist, David Simpson, Robert Bergström, Michael E. Jenkin, Mikael Ehn, Joel A. Thornton, M. Rami Alfarra, Thomas J. Bannan, Carl J. Percival, Michael Priestley, David Topping, Astrid Kiendler-Scharr. Secondary organic aerosol reduced by mixture of atmospheric vapours. Nature, 2019; 565 (7741): 587 DOI: 10.1038/s41586-018-0871-y

https://www.nature.com/articles/s41586-018-0871-y

Abstract: "Secondary organic aerosol contributes to the atmospheric particle burden with implications for air quality and climate. Biogenic volatile organic compounds such as terpenoids emitted from plants are important secondary organic aerosol precursors with isoprene dominating the emissions of biogenic volatile organic compounds globally. However, the particle mass from isoprene oxidation is generally modest compared to that of other terpenoids. Here we show that isoprene, carbon monoxide and methane can each suppress the instantaneous mass and the overall mass yield derived from monoterpenes in mixtures of atmospheric vapours. We find that isoprene ‘scavenges’ hydroxyl radicals, preventing their reaction with monoterpenes, and the resulting isoprene peroxy radicals scavenge highly oxygenated monoterpene products. These effects reduce the yield of low-volatility products that would otherwise form secondary organic aerosol. Global model calculations indicate that oxidant and product scavenging can operate effectively in the real atmosphere. Thus highly reactive compounds (such as isoprene) that produce a modest amount of aerosol are not necessarily net producers of secondary organic particle mass and their oxidation in mixtures of atmospheric vapours can suppress both particle number and mass of secondary organic aerosol. We suggest that formation mechanisms of secondary organic aerosol in the atmosphere need to be considered more realistically, accounting for mechanistic interactions between the products of oxidizing precursor molecules (as is recognized to be necessary when modelling ozone production)."


See also:

Title: "Atmospheric reaction networks affecting climate are more complex than was thought"

https://www.nature.com/articles/d41586-019-00263-1?WT.ec_id=NATURE-20190131&utm_source=nature_etoc&utm_medium=email&utm_campaign=20190131&sap-outbound-id=D1AA71230F3906FBC3FB4A289A2C302D001C6D66

Extract: "Plants take up carbon dioxide and release volatile organic compounds (VOCs), in a similar way to how other organisms breathe in oxygen and exhale CO2. These VOCs are oxidized in the atmosphere and then contribute substantially to the burden of tiny particles suspended in the air, which are known as aerosols. Aerosols produced from VOCs are known as secondary organic aerosols (SOAs), and affect both air quality and Earth’s climate. The total rate of SOA production was thought to be the sum of the individual rates associated with the oxidation of each VOC. But writing in Nature, McFiggans et al. show that a more accurate description is needed to improve the representation of SOAs in computational models of air quality and climate.

The effect of aerosols on climate depends on the fraction of tiny particles that can seed cloud formation. In this regard, both the number of particles per unit volume and the size of particles are crucial9. Low-volatility HOMs produced from monoterpene oxidation have a key role in growing aerosol particles of approximately 1–2 nanometres in diameter to sizes large enough to seed clouds (60–100 nm). These HOMs might also be directly involved in the initial steps of forming nanometre-sized particles in the atmosphere10. It will be necessary to include the HOM scavenging observed by McFiggans et al. in global models that explicitly consider particle formation and growth, to understand the climatic implications."
&

Title: "Unexpected link between air pollutants from plants and humanmade emissions"

https://www.sciencedaily.com/releases/2019/01/190130161701.htm

Extract: "Scientists are a step closer to understanding what controls fine particulate matter in the Earth's atmosphere after identifying new linkages between natural contaminants and with humanmade pollutants."

37
The linked reference discusses paleo-evidence that volcanic activity (including from Antarctica) "… increased global arc flux in the Permian leading to elevated background levels of atmospheric CO2 conducive to producing an environmental crisis …".  Not to seem melodramatic but if an MICI-type of WAIS collapse triggers an increased amount of volcanic activity in Antarctica; I wonder how much the associated volcanic emissions of CO₂ might contribute to subsequent global warming:

For reference: the first attached image shows:  Middle Jurassic Gondwana reconstruction showing three large igneous provinces (after Storey & Kyle 1997); Ferrar, Karoo and Chon Aike, and the location of the Weddell Sea Triple Junction (WSTJ) after Elliot & Fleming 2000.  DML, Dronning Maud Land; FI, Falkland Islands; while the second attached image shows the modern tectonic plate margins and faults.


D.A. Nelson et al. Tracking voluminous Permian volcanism of the Choiyoi Province into central Antarctica, Lithosphere (2019). DOI: 10.1130/L1015.1

https://pubs.geoscienceworld.org/gsa/lithosphere/article/569744/Tracking-voluminous-Permian-volcanism-of-the

Abstract: "Permian volcanic deposits are widespread throughout southwestern Gondwana and record voluminous silicic continental arc volcanism (e.g., Choiyoi Province) that may have contributed to Permian global warming and environmental degradation. Many Permian volcanic deposits of southwestern Gondwana (southern South America, southern Africa, West Antarctica and eastern Australia), however, remain to be accurately correlated to magmatic source regions along the active paleo-Pacific margin of Gondwana, and this lack of correlation limits our understanding of the timing and distribution of voluminous volcanism. Here we present detrital zircon U-Pb and Hf isotope data for Permian volcaniclastic sedimentary rocks from the Ellsworth Mountains, Pensacola Mountains, and the Ohio Range of central Antarctica in southwestern Gondwana used to determine their volcanic source along the paleo-Pacific margin of Gondwana. Rocks in central Antarctica record Permian (ca. 268 Ma) volcanism with a mean zircon εHfi of -0.04 ± 4.8 (2 standard deviation). Comparison of these zircon age and Hf data with compilations for adjacent regions along the Gondwana margin suggest derivation of the Antarctic zircons from a major episode of Permian explosive arc volcanism that is broadly synchronous with, and geochemically similar to, the voluminous Choiyoi Province in South America. This correlation also relates the source of synchronous volcaniclastic deposits in the Karoo Basin, South Africa, to the same major Permian volcanic episode associated with the Choiyoi Province. In aggregate, geochemical data from Permian zircon in central Antarctica support an along-arc variation in geochemistry, with isotopically enriched high-flux magmatism associated with thicker crust and lithospheric mantle in South America, and isotopically depleted magmatism and thinner crust and lithospheric mantle in Australia. The timing of inferred Choiyoi-related explosive arc volcanism recorded in the Antarctic sector, South African sector, and South American sector is contemporaneous with a documented increase in global arc flux, an increase in atmospheric CO2, a decrease in δ13C of benthic marine fossils, and mass extinction events. We suggest that the Choiyoi Province and correlated arc volcanism along the Gondwana margin contributed to increased global arc flux in the Permian leading to elevated background levels of atmospheric CO2 conducive to producing an environmental crisis during mafic large igneous province emplacement, and may serve as an example of continental arc outgassing exerting a first order control on climate."
&

See also the associated linked article:

Title: "Permian volcanism contributed to atmospheric greenhouse gas content in Antarctica"

https://phys.org/news/2019-04-permian-volcanism-contributed-atmospheric-greenhouse.html

Extract: "These new age data for the Choiyoi Province correlate with a global increase in arc magmatic flux, a decrease in delta-13C, and an increase in global atmospheric CO2 that began prior to emplacement of the Siberian Traps. Consequently, these findings support recent advancements in the field that point to arc flare-up events as contributing a first-order control on atmospheric greenhouse gas content. Major environmental degradation and mass extinction events, ultimately, may have been the result of high magmatic flux events, such as the Choiyoi Province occurring synchronously, or near synchronously, with a Large Igneous Province event, such as the Siberian Traps or the Mishna.

This finding represents the southernmost documented extension of this broad volcanic and magmatic province that is distinct from continental arc activity recorded in the central Transantarctic mountains, Marie Byrd Land, Zealandia, and Australia."

38
79North is a critical marine terminating glacier in Northeast Greenland (see the attached image).  The linked reference discusses how sensitive the associated ice tongue (79NG) is to basal ice melting from relatively warm Atlantic Water (AW).  I wonder whether a MICI-type of WAIS collapse beginning circa 2040 might influence the MOC sufficiently to force more AW beneath 79NG by mid-century, which might lead to a collapse of the 79NG which then might trigger a surge of 79North:

Anhaus, P., Smedsrud, L. H., Årthun, M., and Straneo, F.: Sensitivity of submarine melting on North East Greenland towards ocean forcing, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-35, in review, 2019.

https://www.the-cryosphere-discuss.net/tc-2019-35/

Abstract. The Nioghalvfjerdsbræ (79NG) is a floating ice tongue on Northeast Greenland draining a large part of the Greenland Ice Sheet. A CTD profile from a rift on the ice tongue close to the northern front shows that Atlantic Water (AW) is present in the cavity below, with maximum temperature of approximately 1 °C at 610 m depth. The AW present in the cavity thus has the potential to drive submarine melting along the ice base. Here, we simulate melt rates from the 79NG with a 1D numerical Ice Shelf Water (ISW) plume model. A meltwater plume is initiated at the grounding line depth (600 m) and rises along the ice base as a result of buoyancy contrast to the underlying AW. Ice melts as the plume entrains the warm AW. Maximum simulated melt rates are 50–76 m yr−1 within 10 km of the grounding line. Within a zone of rapid decay between 10 km and 20 km melt rates drop to roughly 6 m yr−1. Further downstream, melt rates are between 15 m yr−1 and 6 m yr−1. The melt-rate sensitivity to variations in AW temperatures is assessed by forcing the model with AW temperatures between 0.1–1.4 °C, as identified from the ECCOv4 ocean state estimate. The melt rates increase linearly with rising AW temperature, ranging from 10 m yr−1 to 21 m yr−1 along the centerline. The corresponding freshwater flux ranges between 11 km3 yr−1 (0.4 mSv) and 30 km3 yr−1 (1.0 mSv), which is 5 % and 12 % of the total freshwater flux from the Greenland Ice Sheet since 1995, respectively. Our results improve the understanding of processes driving submarine melting of marine-terminating glaciers around Greenland, and its sensitivity to changing ocean conditions.

39

Maybe, the truth can only appear in aggregate, arising out of an ecosystem of different kinds of stories that rub up against one another in surprising ways."

What we probably need is for a modern-day Leo Tolstoy to write a forward looking equivalent of "War and Peace" framing multiple individual stories all of which contribute to the overarching trends of both climate change and technological change in our information-based era.  Short of that it may be difficult to engage the hearts and minds of the public for an increasingly likely Ice Apocalypse this century.

40
The linked article discusses: "Why is the story of climate catastrophe so hard to tell?"

Title: "Down to Earth - Why is the story of climate catastrophe so hard to tell?"

https://newrepublic.com/article/153505/case-climate-alarmism-nathaniel-rich-david-wallace-wells-review

Extract: "How do you talk about an emergency when it seems as if no one is listening? For years, journalists, scientists, and activists concerned with the ongoing horror of climate catastrophe have faced this problem. Arguably the most important issue of our time, climate change is a known ratings killer. If you aren’t already a victim of climate-related disaster, the issue can feel far away, and many readers find the unrelenting rise of global warming too disturbing, or simply too overwhelming, to contemplate. “No one wants to read about climate,” a literary agent once told me, “It’s too depressing.”

Climate change is huge, abstract, and wickedly complex, so it resists the kind of easy narrative that might make it stick in a reader’s mind or suggest concrete policy.

Some voices have broken through to mass audiences—Bill McKibben, Naomi Klein—mostly in expository styles geared toward sharing information and analysis. But where, at least in nonfiction, are the storytellers who can sing songs of impending doom, who can bring the horror that is already upon us into focus, and help us see our own places within it?

Wallace-Wells’s piece, too, produced an immediate backlash from the climate intelligentsia, partly because he got some of the science wrong, overstating certain risks, but also because the piece was charged with the cardinal sin of being “alarmist.” People didn’t like how Wallace-Wells was talking about climate change, and the science internet exploded with heated discussion of the “right way” to approach it.

We know it’s going to be bad, but human activity today could still make the future worse. So it’s true both that we are too late and that there is no time to be lost. Yet if we get the framing of this story wrong—if we see the issue as a matter of individual consumer choice, for example, or choose a purely emotional rather than an explicitly political framing—we risk missing the point altogether.

This is one of the fundamental difficulties of any international action on climate change: Less economically developed nations are not about to halt growth and give up on the increases in living standards achieved by burning fossil fuels, gains already achieved by richer nations at the expense of a stable climate.

As climate change “begins to seem inescapable, total—it may cease to be a story and become, instead, an all-encompassing background. No longer a narrative, it would recede into what literary theorists call metanarrative, succeeding those—like religious truth or faith in progress—that have governed the culture of earlier eras.” This will, in turn, affect all our stories. “When we can no longer pretend that climate suffering is distant—in time or place—we will stop pretending about it and start pretending within it.” In this imagined future, “even romantic comedies would be staged under the sign of warming, as surely as screwball comedies were extruded by the anxieties of the Great Depression.”

It’s not surprising that writers can struggle to tell new stories about climate change, stewing as we are in the midst of it. At the very least, these are unprecedented times that call for new kinds of narratives—or perhaps new forms, entirely—that help make sense of our interrelated lives on a warming planet.

Maybe, the truth can only appear in aggregate, arising out of an ecosystem of different kinds of stories that rub up against one another in surprising ways."

41
As the material in the linked Rolling Stone article is copyrighted, you will need to click on the link to see what Bill McKibben thinks may be coming:

Excerpts from “FALTER: Has the Human Game Begun to Play Itself Out?” by Bill McKibben. Published by Henry Holt and Company April 16th 2019. Copyright © 2019 by Bill McKibben. All rights reserved.

https://www.rollingstone.com/politics/politics-features/bill-mckibben-falter-climate-change-817310/?fbclid=IwAR3kcTeT459goV7M--SzoQ7IfxSLXKiiGXF1nrOQHoA7JqkwJiMHdE7wbrw

42
If you are looking for convenient yet specific information about what atmospheric surface concentrations for 43 different GHGs the different SSP scenarios specified from 2000 to 2500, then you can visit the linked website:

Title: "Greenhouse Gas Factsheets"

http://greenhousegases.science.unimelb.edu.au/#!/view

Extract: "This webpage offers comprehensive, interactive plots, factsheets and data download options for atmospheric surface concentrations of 43 greenhouse gases and 3 equivalent gas time series from 2000 years ago to the year 2500."


43
The linked article by Robert Kopp calls for governments (both in the USA and around the world) fund institutions of higher learning (e.g. universities) to set-up sustained programs on "scientific climate risk management".

Title: "HOW CLIMATE RESEARCH CAN ADAPT TO THE IMMINENT THREAT OF GLOBAL WARMING"

https://psmag.com/environment/how-climate-research-needs-to-adapt

Extract: "It's time for the climate science research enterprise to focus on integrating fundamental science inquiry with risk management.

Historically, climate science has been primarily curiosity-driven—scientists seeking fundamental understanding of the way our planet works because of the inherent interest in the problem.

Now it's time for the climate science research enterprise to adopt an expanded approach, one that focuses heavily on integrating fundamental science inquiry with risk management.

It is possible—if emissions are high, and ice-sheet physics unstable—that the world could see six feet or more of global average sea-level rise over the course of this century, with substantially more in some regions.  It is also possible—if emissions are low, or ice-sheet physics fairly stable—that it could be just two feet.

When the scientists discover that a benchmark is going to be hit—for example, when ice-sheet observations and modeling make clear whether we are on course for two feet or six feet of sea-level rise in this century—the engineers, planners, and policymakers can adjust accordingly.

This long-term, iterative process is a break with current practices. It requires sustained relationships that are not a good fit for much of the academic scientific enterprise, which is driven by curious individuals and funded by short-term grants.

… climate risk-focused partnerships often lack institutional stability; most are the products of a small number of visionary individuals and many are funded one small grant at a time. And yet stability is critical for science that is intended to support decades of chronic risk management.

That's why I believe it is worth considering a national investment in our universities that is analogous to that of cooperative extension but applied to scientific climate risk management.

These are not easy or cheap changes to make. But they are both easy and inexpensive when compared to the costs of climate change and the costs of the climate risk management decisions they will help inform."

Edit:  For an example of the type of 'scientific climate risk management' that Robert Kopp is talking about, see the following linked article (which does not consider ice-climate feedback mechanisms impacts on ECS this century).

John A. Hall, Christopher P. Weaver, Jayantha Obeysekera, Mark Crowell, Radley M. Horton, Robert E. Kopp, et al. (24 Jan 2019), "Rising Sea Levels: Helping Decision-Makers Confront the Inevitable", Coastal Management, Vol 47, Issue 2, Pages 127-150, https://doi.org/10.1080/08920753.2019.1551012

https://www.tandfonline.com/doi/abs/10.1080/08920753.2019.1551012?journalCode=ucmg20

Abstract

Sea-level rise (SLR) is not just a future trend; it is occurring now in most coastal regions across the globe. It thus impacts not only long-range planning in coastal environments, but also emergency preparedness. Its inevitability and irreversibility on long time scales, in addition to its spatial non-uniformity, uncertain magnitude and timing, and capacity to drive non-stationarity in coastal flooding on planning and engineering timescales, create unique challenges for coastal risk-management decision processes. This review assesses past United States federal efforts to synthesize evolving SLR science in support of coastal risk management. In particular, it outlines the: (1) evolution in global SLR scenarios to those using a risk-based perspective that also considers low-probability but high-consequence outcomes, (2) regionalization of the global scenarios, and (3) use of probabilistic approaches. It also describes efforts to further contextualize regional scenarios by combining local mean sea-level changes with extreme water level projections. Finally, it offers perspectives on key issues relevant to the future uptake, interpretation, and application of sea-level change scenarios in decision-making. These perspectives have utility for efforts to craft standards and guidance for preparedness and resilience measures to reduce the risk of coastal flooding and other impacts related to SLR.

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The Early Paleozoic Era ran from about 542 million, to about 251 million, years ago, and included a major extinction event at the end of the Ordovician period (485 to 443 million years ago).  The linked new research on biodiversity in these periods, offers some insights on our current period of a Sixth Extinction event.  The finding of the new research [Rasmussen et al. (2019)], the very large extinction event during the end of the Ordovician period was not primarily due to global cooling (as was previously assumed) but rather by climate change associated with increased volcanic activity.  As high levels of GHG emissions from strong volcanic activity can abruptly increase global warming, the Rasmussen et al. (2019) findings suggest that biological systems do not adapt well to abrupt increases in GMSTA; which has gloomy implications for our likely pathway this century:

Title: "New research about biodiversity reveals the importance of climate on today's abundance of life"

https://phys.org/news/2019-04-biodiversity-reveals-importance-climate-today.html

Extract: "Biodiversity Natural history museum paleontologists in Copenhagen and Helsinki have succeeded in mapping historical biodiversity in unprecedented detail. For the first time, it is possible to compare the impact of climate on global biodiversity in the distant past—a result that paints a gloomy picture for the preservation of present-day species richness. The study has just been published in the prestigious American journal, Proceedings of the National Academy of Sciences (PNAS).

Furthermore, we find that the very large extinction event at the end of the Ordovician period (485—443 million years ago), when upwards of 85 percent of all species disappeared, was not "a brief ice age—as previously believed—but rather a several million years long crisis interval with mass extinctions. It was most likely prompted by increased volcanic activity. It took nearly 40 million years to rectify the mess before biodiversity was on a par with levels prior to this period of volcanic caused death and destruction," says Christian Mac Ørum."
&

Christian M. Ø. Rasmussen et al. Cascading trend of Early Paleozoic marine radiations paused by Late Ordovician extinctions, Proceedings of the National Academy of Sciences (2019). DOI: 10.1073/pnas.1821123116

https://www.pnas.org/content/116/15/7207

Significance

The first 120 million years of Phanerozoic life witnessed significant changes in biodiversity levels. Attempts to correlate these changes to potential short-term environmental drivers have been hampered by the crude temporal resolution of current biodiversity estimates. We present a biodiversity curve for the Early Paleozoic with high temporal precision. It shows that once equatorial sea-surface temperatures fell to present-day levels during the early Mid Ordovician, marine biodiversity accumulation accelerated dramatically. However, this acceleration ceased as increased volcanism commenced during the mid-Late Ordovician. Since biodiversity levels were not restored for at least ∼35 million years, this finding redefines the nature of the end Ordovician mass extinctions and further reframes the Silurian as a prolonged recovery interval.

Abstract

The greatest relative changes in marine biodiversity accumulation occurred during the Early Paleozoic. The precision of temporal constraints on these changes is crude, hampering our understanding of their timing, duration, and links to causal mechanisms. We match fossil occurrence data to their lithostratigraphical ranges in the Paleobiology Database and correlate this inferred taxon range to a constructed set of biostratigraphically defined high-resolution time slices. In addition, we apply capture–recapture modeling approaches to calculate a biodiversity curve that also considers taphonomy and sampling biases with four times better resolution of previous estimates. Our method reveals a stepwise biodiversity increase with distinct Cambrian and Ordovician radiation events that are clearly separated by a 50-million-year-long period of slow biodiversity accumulation. The Ordovician Radiation is confined to a 15-million-year phase after which the Late Ordovician extinctions lowered generic richness and further delayed a biodiversity rebound by at least 35 million years. Based on a first-differences approach on potential abiotic drivers controlling richness, we find an overall correlation with oxygen levels, with temperature also exhibiting a coordinated trend once equatorial sea surface temperatures fell to present-day levels during the Middle Ordovician Darriwilian Age. Contrary to the traditional view of the Late Ordovician extinctions, our study suggests a protracted crisis interval linked to intense volcanism during the middle Late Ordovician Katian Age. As richness levels did not return to prior levels during the Silurian—a time of continental amalgamation—we further argue that plate tectonics exerted an overarching control on biodiversity accumulation.

45
I think that it is always good to compare observed versus consensus science projections, and in this regards, the February 2018 Climate Lab Book article by Ed Hawkins compares observed GMSTA versus CMIP5 projections, with the attached image from the linked article showing comparisons for FAR, SAR, TAR, AR4 & AR5 thru 2035.

Title: "Comparing CMIP5 & observations"

https://www.climate-lab-book.ac.uk/comparing-cmip5-observations/

Extract about the first image: "In addition, the figure below updates Fig. 1.4 from IPCC AR5, which compares projections from previous IPCC Assessment Reports with subsequent observations. The HadCRUT4.4 observations from 2013-2015 are added as black squares. Note that previous reports made differing assumptions about future emissions. This figure has not yet been updated to include 2016-7 temperature data."

Note the original caption for AR5 Fig. 1.4 is: "Figure 1.4 |  Estimated changes in the observed globally and annually averaged surface temperature anomaly relative to 1961–1990 (in °C) since 1950 compared with the range of projections from the previous IPCC assessments. Values are harmonized to start from the same value in 1990. Observed global annual mean surface air temperature anomaly, relative to 1961–1990, is shown as squares and smoothed time series as solid lines (NASA (dark blue), NOAA (warm mustard), and the UK Hadley Centre (bright green) reanalyses). The coloured shading shows the projected range of global annual mean surface air temperature change from 1990 to 2035 for models used in FAR (Figure 6.11 in Bretherton et al., 1990), SAR (Figure 19 in the TS of IPCC, 1996), TAR (full range of TAR Figure 9.13(b) in Cubasch et al., 2001). TAR results are based on the simple climate model analyses presented and not on the individual full three-dimensional climate model simulations. For the AR4 results are presented as single model runs of the CMIP3 ensemble for the historical period from 1950 to 2000 (light grey lines) and for three scenarios (A2, A1B and B1) from 2001 to 2035. The bars at the right-hand side of the graph show the full range given for 2035 for each assessment report. For the three SRES scenarios the bars show the CMIP3 ensemble mean and the likely range given by –40% to +60% of the mean as assessed in Meehl et al. (2007). The publication years of the assessment reports are shown. See Appendix 1.A for details on the data and calculations used to create this figure."

To me this first image together with the second image (note one needs to add about 0.26C to GMSTA relative to 1961 to 1990 in order to compare to GMSTA values relative to the last 19th century) indicate several things including:

1.  The FAR estimates of GMSTA were reasonable, and then politics influenced the consensus science SAR & TAR estimates to make them err on the side of least drama.

2. The mean GMSTA projection using the SRES A1B radiative forcing scenario underestimate the observed GMSTA values thru 2018 (& projected by Gavin Schmidt thru 2019) shown in the second image.  This raises the prospect that consensus climate science thru AR5 may have underestimated climate sensitivity.

46
The linked reference indicates that since mid-2014 AABW has been warming at an accelerating rate:

Gregory C. Johnson, Sarah G. Purkey, Nathalie V. Zilberman & Dean Roemmich  (13 February 2019), "Deep Argo Quantifies Bottom Water Warming Rates in the Southwest Pacific Basin", Geophysical Research Letters,https://doi.org/10.1029/2018GL081685

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL081685

Abstract
Data reported from mid‐2014 to late 2018 by a regional pilot array of Deep Argo floats in the Southwest Pacific Basin are used to estimate regional temperature anomalies from a long‐term climatology as well as regional trends over the 4.4 years of float data as a function of pressure. The data show warm anomalies that increase with increasing pressure from effectively 0 near 2,000 dbar to over 10 (±1) m°C by 4,800 dbar, uncertainties estimated at 5–95%. The 4.4‐year trend estimate shows warming at an average rate of 3 (±1) m°C/year from 5,000 to 5,600 dbar, in the near‐homogeneous layer of cold, dense bottom water of Antarctic origin. These results suggest acceleration of previously reported long‐term warming trends in the abyssal waters in this region. They also demonstrate the ability of Deep Argo to quantify changes in the deep ocean in near real‐time over short periods with high accuracy.

Plain Language Summary
The coldest waters that fill much of the deep ocean worldwide originate near Antarctica. Temperature data collected from oceanographic cruises around the world at roughly 10‐year intervals show that these near‐bottom waters have been warming on average since the 1990s, absorbing a substantial amount of heat. Data from an array of robotic profiling Deep Argo floats deployed in the Southwest Pacific Ocean starting in mid‐2014 reveal that near‐bottom waters there have continued to warm over the past 4.4 years. Furthermore, these new data suggest an acceleration of that warming rate. These data show that Deep Argo floats are capable of accurately measuring regional changes in the deep ocean. The ocean is the largest sink of heat on our warming planet. A global array of Deep Argo floats would provide data on how much Earth's climate system is warming and possibly improve predictions of future warming.

47
Apparently, illegal logging (primarily by Chinese companies) is contributing to a radical deforestation of Mozambique (see image).  This is just one example of how quickly anthrogenic damage can be done to the biosphere.

Title: "Mozambique reforms timber sector to counter illegal logging"

https://www.reuters.com/article/us-mozambique-forest-logging/mozambique-reforms-timber-sector-to-counter-illegal-logging-idUSKBN1KG1F8

48
The linked reference [Box et al. (2019)] finds that: "The Arctic biophysical system is now clearly trending away from its 20th Century state and into an unprecedented state, with implications not only within but beyond the Arctic."

Jason E Box et al. (2019), "Key indicators of Arctic climate change: 1971–2017", Environmental Research Letters, Vol. 14, No. 4.

https://iopscience.iop.org/article/10.1088/1748-9326/aafc1b/meta

Abstract: "Key observational indicators of climate change in the Arctic, most spanning a 47 year period (1971–2017) demonstrate fundamental changes among nine key elements of the Arctic system. We find that, coherent with increasing air temperature, there is an intensification of the hydrological cycle, evident from increases in humidity, precipitation, river discharge, glacier equilibrium line altitude and land ice wastage. Downward trends continue in sea ice thickness (and extent) and spring snow cover extent and duration, while near-surface permafrost continues to warm. Several of the climate indicators exhibit a significant statistical correlation with air temperature or precipitation, reinforcing the notion that increasing air temperatures and precipitation are drivers of major changes in various components of the Arctic system. To progress beyond a presentation of the Arctic physical climate changes, we find a correspondence between air temperature and biophysical indicators such as tundra biomass and identify numerous biophysical disruptions with cascading effects throughout the trophic levels. These include: increased delivery of organic matter and nutrients to Arctic near‐coastal zones; condensed flowering and pollination plant species periods; timing mismatch between plant flowering and pollinators; increased plant vulnerability to insect disturbance; increased shrub biomass; increased ignition of wildfires; increased growing season CO2 uptake, with counterbalancing increases in shoulder season and winter CO2 emissions; increased carbon cycling, regulated by local hydrology and permafrost thaw; conversion between terrestrial and aquatic ecosystems; and shifting animal distribution and demographics. The Arctic biophysical system is now clearly trending away from its 20th Century state and into an unprecedented state, with implications not only within but beyond the Arctic. The indicator time series of this study are freely downloadable at AMAP.no."
&

See also:

Title: "Researchers Warn Arctic Has Entered 'Unprecedented State' That Threatens Global Climate Stability"

https://www.commondreams.org/news/2019/04/08/researchers-warn-arctic-has-entered-unprecedented-state-threatens-global-climate

Extract: "But, as UNEP acting executive director Joyce Msuya noted at the time, "What happens in the Arctic does not stay in the Arctic.""

49
The two linked articles discuss recent research that does not necessarily indicate an increased risk of abrupt climate change this century; but they both provide new information that can be used to better calibrate future advance ESM projections, so I provide this post as general background information (note the image comes from the first article):

Title: "Melting glaciers causing sea levels to rise at ever greater rates"

https://phys.org/news/2019-04-glaciers-sea-greater.html

Extract: "Glaciers have lost more than 9 trillion tons (that is 9,625,000,000,000 tons) of ice between 1961 and 2016, which has resulted in global sea levels rising by 27 millimeters in this period. The largest contributors were glaciers in Alaska, followed by the melting ice fields in Patagonia and glaciers in the Arctic regions. Glaciers in the European Alps, the Caucasus and New Zealand were also subject to significant ice loss; however, due to their relatively small glacierized areas, they played only a minor role when it comes to the rising global sea levels."
&

Title: "Carbon lurking in deep ocean threw ancient climate switch, say researchers"

https://phys.org/news/2019-04-carbon-lurking-deep-ocean-threw.html

Extract: "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."

50
Climate warming that is expected to reduce soil moisture, and therefore increase soil aeration, of Northern peatlands.  Thus, the finding of the linked reference that increased soil drying will decrease soil organic carbon (SOC) stocks in peatlands, implies that ECS will be higher, this century, than previously assumed by consensus climate science:

Anna M. Laine et al. Warming impacts on boreal fen CO 2 exchange under wet and dry conditions, Global Change Biology (2019). DOI: 10.1111/gcb.14617

https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14617

Abstract: "Northern peatlands form a major soil carbon (C) stock. With climate change, peatland C mineralization is expected to increase, which in turn would accelerate climate change. A particularity of peatlands is the importance of soil aeration, which regulates peatland functioning and likely modulates the responses to warming climate. Our aim is to assess the impacts of warming on a southern boreal and a sub‐arctic sedge fen carbon dioxide (CO2) exchange under two plausible water table regimes: wet and moderately dry. We focused this study on minerotrophic treeless sedge fens, as they are common peatland types at boreal and (sub)arctic areas, which are expected to face the highest rates of climate warming. In addition, fens are expected to respond to environmental changes faster than the nutrient poor bogs. Our study confirmed that CO2 exchange is more strongly affected by drying than warming. Experimental water level draw‐down (WLD) significantly increased gross photosynthesis and ecosystem respiration. Warming alone had insignificant impacts on the CO2 exchange components, but when combined with WLD it further increased ecosystem respiration. In the southern fen, CO2 uptake decreased due to WLD, which was amplified by warming, while at northern fen it remained stable. As a conclusion, our results suggest that a very small difference in the WLD may be decisive, whether the C sink of a fen decreases, or whether the system is able to adapt within its regime and maintain its functions. Moreover, the water table has a role in determining how much the increased temperature impacts the CO2 exchange."

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