Ice Apocalypse - Multiple Meters Sea Level Rise

[FishOutofWater]

Those gravity studies of Antarctic geology are very interesting to me. It appears to me that the WARS is not inactive, but similar to the tectonic situation in the Arctic ocean where there's very slow spreading along ridge segments.

It's impossible to do typical GPS land based tectonic studies there because the ice moves much faster than the rifting. However, the ongoing volcanic activity, while not definitive, is evidence supportive of ongoing activity along the long rift/transform fault system that crosses Antarctica.

Of course, this tectonic situation is relevant to glacial melting, isostatic adjustment and sea level rise. This rift zone will be a potential region of increasing volcanism as glaciers retreat and depressure deep magma reservoirs. Yes, this is a potential positive feedback.

[Tom_Mazanec]

AbruptSLR, no offense but wouldn't comments on Amazon deforestation and bark beetles belong on the deforestation thread?

[kassy]

There is a bit of local history behind it.

If the Emperor does not wish to step outside the palace you can hit the quote button and cross post.

[AbruptSLR]

ASLR, Have you noticed that JISAO monthly PDO index hasn't updated since Sept. 2018. ?

I have, and I attributed it to (without direct evidence) the Trump Administration's influence.

[AbruptSLR]

AbruptSLR, no offense but wouldn't comments on Amazon deforestation and bark beetles belong on the deforestation thread?

Tom,

When you consider cascading tipping points (and/or cascading positive feedbacks) in a domino effect, one cannot separate the separate domino tiles from the cascade (e.g. see Reply #663).

ASLR

[AbruptSLR]

There is a bit of local history behind it.

If the Emperor does not wish to step outside the palace you can hit the quote button and cross post.

kassy,

As I replied to Tom, from a scientific point of view it is not a good idea to evaluate climate risk from a bunch of scientific ivory towers; but rather one needs to consider all the self-reinforcing feedbacks as they begin to accelerate nonlinearly.

ASLR

[Tom_Mazanec]

21 beach towns soon to be underwater:
https://www.usatoday.com/story/money/2019/07/18/atlantic-city-key-west-beach-towns-will-be-under-water-climate-change/39697819/

[AbruptSLR]

The linked reference mathematically studies the dynamics of tipping cascades for complex networks and provides a worked example of the influence of global warming on the potential collapse of the Amazon rainforest.  Their findings (see image) indicate that for a high network coupling strength the Amazon rainforest has a high risk of collapse as GMSTA approaches 1.5C.  Of course the risk of the Amazon rainforest collapsing is only one of numerous examples of climate change related Earth Systems tipping cascades.

Jonathan Krönke et al. (2019), "Dynamics of Tipping Cascades on Complex Networks", arXiv:1905.05476v1

https://arxiv.org/abs/1905.05476

https://arxiv.org/pdf/1905.05476.pdf

Abstract: "Tipping points occur in a lot of systems in various disciplines such as ecology, climate science, economy or engineering. Tipping points are critical thresholds in system parameters or state variables at which a tiny perturbation can lead to a qualitative change of the system. Many systems with tipping points can be modeled as networks of coupled multistable subsystems, e.g. coupled patches of vegetation, connected lakes, interacting climate tipping elements or multiscale infrastructure systems. In such networks, tipping events in one subsystem are able to induce tipping cascades via domino effects. Here, we investigate the effects of network topology on the occurrence of such cascades. Numerical cascade simulations with a conceptual dynamical model for tipping points are conducted on Erdős-Rényi, Watts-Strogatz and Barabási-Albert networks. We find that clustered and spatially organized networks increase the vulnerability of networks and can lead to tipping of the whole network. This effect is only present in dynamical models of tipping interactions and is not captured by threshold models of contagion processes. We highlight how this result for global properties of the network can be linked to small-scale motifs such as feedback loops and feed-forward loops. Additionally, the model is applied to a network generated from moisture-recycling simulations of the Amazon rainforest and results of cascade simulations are compared to those from the model networks. Consistently, we observe that the spatially structured moisture-recycling network is more vulnerable to tipping cascades than more disordered random network topologies. These results could be useful to evaluate which systems are vulnerable or resilient due to their network topology and might help to design systems accordingly."

Caption: "FIG. 11. Average cascade size with respect to average degree and coupling strength for the network generated with moisture-flow simulations for the Amazon rainforest (N = 160)."

[AbruptSLR]

The linked article indicates that not only do climate scientists need to better evaluate domino cascades of natural feedback mechanisms, but they also need to better evaluate the ripple effects on socio-economic systems.  Finally, the article indicates that both climate scientists and decision makers should not let the complexity of such natural and socio-economic systems paralyze our ability to make decisions.

Title: "The Next Climate Frontier: Predicting a Complex Domino Effect"

https://www.scientificamerican.com/article/the-next-climate-frontier-predicting-a-complex-domino-effect/

Extract: "The report emphasizes that scientists need to look not only at how global warming is changing natural systems but also how those changes will set off their own ripple effects through other areas—for example, how the increasing threat of drought harms agriculture, which in turn affects the economy and food availability.
…
Still, experts acknowledge that ultimately, they will never be able to put odds on every single possible set of interactions, Mach says. Rather it will be a matter of improving the available information to make better calls on what actions to take wherever possible. “We still need to make decisions,” she says. “We can’t let the complexity paralyze us.”"

[AbruptSLR]

Policy makers are seriously underestimating the reinforcing & cascading nature of positive feedback mechanisms:

Juan C. Rocha et al. (21 Dec 2018), "Cascading regime shifts within and across scales", Science,  Vol. 362, Issue 6421, pp. 1379-1383, DOI: 10.1126/science.aat7850

https://science.sciencemag.org/content/362/6421/1379

Cascading effects of regime shifts
The potential for regime shifts and critical transitions in ecological and Earth systems, particularly in a changing climate, has received considerable attention. However, the possibility of interactions between such shifts is poorly understood. Rocha et al. used network analysis to explore whether critical transitions in ecosystems can be coupled with each other, even when far apart (see the Perspective by Scheffer and van Nes). They report different types of potential cascading effects, including domino effects and hidden feedbacks, that can be prevalent in different systems. Such cascading effects can couple the dynamics of regime shifts in distant places, which suggests that the interactions between transitions should be borne in mind in future forecasts.

Abstract
Regime shifts are large, abrupt, and persistent critical transitions in the function and structure of ecosystems. Yet, it is unknown how these transitions will interact, whether the occurrence of one will increase the likelihood of another or simply correlate at distant places. We explored two types of cascading effects: Domino effects create one-way dependencies, whereas hidden feedbacks produce two-way interactions. We compare them with the control case of driver sharing, which can induce correlations. Using 30 regime shifts described as networks, we show that 45% of regime shift pairwise combinations present at least one plausible structural interdependence. The likelihood of cascading effects depends on cross-scale interactions but differs for each type. Management of regime shifts should account for potential connections.

Title: "Risks of 'domino effect' of tipping points greater than thought, study says"

https://www.theguardian.com/environment/2018/dec/20/risks-of-domino-effect-of-tipping-points-greater-than-thought-study-says

Extract: "Policymakers have severely underestimated the risks of ecological tipping points, according to a study that shows 45% of all potential environmental collapses are interrelated and could amplify one another.

The authors said their paper, published in the journal Science, highlights how overstressed and overlapping natural systems are combining to throw up a growing number of unwelcome surprises."

[AbruptSLR]

…
It's impossible to do typical GPS land based tectonic studies there because the ice moves much faster than the rifting.
…
Of course, this tectonic situation is relevant to glacial melting, isostatic adjustment and sea level rise. This rift zone will be a potential region of increasing volcanism as glaciers retreat and depressure deep magma reservoirs. Yes, this is a potential positive feedback.

There are many land features that are not covered by glacial ice in West Antarctica, on both sides of the WARS rift system, as can roughly be seen by all of the bumps in the attached Google Earth image of West Antarctica.  Thus it is possible to do a GPS land based tectonic study, but it may not have the highest resolution.

I suspect that after 2045 volcanism and seismic activity will increase nonlinearly with continued warming.

[AbruptSLR]

The linked reference (& associated article) indicate that the occurrence of the so called 'hiatus' is an indication that ECS is higher than assumed by consensus climate models.  Furthermore, this research indicates that: "As ECS also affects the background warming rate under future scenarios with unmitigated anthropogenic forcing, the probability of a hyper-warming decade—over ten times the mean rate of global warming for the twentieth century—is even more sensitive to ECS."

Femke J. M. M. Nijsse, Peter M. Cox, Chris Huntingford, Mark S. Williamson (2019), "Decadal global temperature variability increases strongly with climate sensitivity", Nature Climate Change, DOI: 10.1038/s41558-019-0527-4

https://www.nature.com/articles/s41558-019-0527-4

Abstract: "Climate-related risks are dependent not only on the warming trend from GHGs, but also on the variability about the trend. However, assessment of the impacts of climate change tends to focus on the ultimate level of global warming, only occasionally on the rate of global warming, and rarely on variability about the trend. Here we show that models that are more sensitive to GHGs emissions (that is, higher equilibrium climate sensitivity (ECS)) also have higher temperature variability on timescales of several years to several decades. Counter-intuitively, high-sensitivity climates, as well as having a higher chance of rapid decadal warming, are also more likely to have had historical ‘hiatus’ periods than lower-sensitivity climates. Cooling or hiatus decades over the historical period, which have been relatively uncommon, are more than twice as likely in a high-ECS world (ECS = 4.5 K) compared with a low-ECS world (ECS = 1.5 K). As ECS also affects the background warming rate under future scenarios with unmitigated anthropogenic forcing, the probability of a hyper-warming decade—over ten times the mean rate of global warming for the twentieth century—is even more sensitive to ECS."

See also:

Title: "More sensitive climates are more variable climates"

https://www.sciencedaily.com/releases/2019/07/190722111921.htm

Extract: "A decade without any global warming is more likely to happen if the climate is more sensitive to carbon dioxide emissions, new research has revealed."

[FishOutofWater]

Yes, you're right that deformation rates could be determined from exposed peaks. Given that we already know that the rates must be pretty low that might be an appropriate scale to study the system independent of the issues with ice.

[AbruptSLR]

The linked reference uses the mid-Holocene warming to improve modelled projections of future Arctic Amplification under RCP 4.5.  Among other conclusions, the study emphasizes the importance of using warm (summer) season sea ice extent projections as input to cold season projections:

Yoshimori, M. and Suzuki, M.: The relevance of mid-Holocene Arctic warming to the future, Clim. Past, 15, 1375-1394, https://doi.org/10.5194/cp-15-1375-2019, 2019.

https://www.clim-past.net/15/1375/2019/

Abstract
There remain substantial uncertainties in future projections of Arctic climate change. There is a potential to constrain these uncertainties using a combination of paleoclimate simulations and proxy data, but such a constraint must be accompanied by physical understanding on the connection between past and future simulations. Here, we examine the relevance of an Arctic warming mechanism in the mid-Holocene (MH) to the future with emphasis on process understanding. We conducted a surface energy balance analysis on 10 atmosphere and ocean general circulation models under the MH and future Representative Concentration Pathway (RCP) 4.5 scenario forcings. It is found that many of the dominant processes that amplify Arctic warming over the ocean from late autumn to early winter are common between the two periods, despite the difference in the source of the forcing (insolation vs. greenhouse gases). The positive albedo feedback in summer results in an increase in oceanic heat release in the colder season when the atmospheric stratification is strong, and an increased greenhouse effect from clouds helps amplify the warming during the season with small insolation. The seasonal progress was elucidated by the decomposition of the factors associated with sea surface temperature, ice concentration, and ice surface temperature changes. We also quantified the contribution of individual components to the inter-model variance in the surface temperature changes. The downward clear-sky longwave radiation is one of major contributors to the model spread throughout the year. Other controlling terms for the model spread vary with the season, but they are similar between the MH and the future in each season. This result suggests that the MH Arctic change may not be analogous to the future in some seasons when the temperature response differs, but it is still useful to constrain the model spread in the future Arctic projection. The cross-model correlation suggests that the feedbacks in preceding seasons should not be overlooked when determining constraints, particularly summer sea ice cover for the constraint of autumn–winter surface temperature response.

[AbruptSLR]

he linked reference indicates how statistically unusual our current warming trend is when compared to any comparable period in the past 2,000 years.  While this is presented to confirm the consensus science position that anthropogenic climate change is real (& not due only to natural variability), these statistics would also be consistent with a relative high (higher than assumed by AR5) value for climate sensitivity.

PAGES 2k Consortium (2019), "Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era", Nature Geoscience, DOI: https://doi.org/10.1038/s41561-019-0400-0

https://www.nature.com/articles/s41561-019-0400-0

Abstract: "Multidecadal surface temperature changes may be forced by natural as well as anthropogenic factors, or arise unforced from the climate system. Distinguishing these factors is essential for estimating sensitivity to multiple climatic forcings and the amplitude of the unforced variability. Here we present 2,000-year-long global mean temperature reconstructions using seven different statistical methods that draw from a global collection of temperature-sensitive palaeoclimate records. Our reconstructions display synchronous multidecadal temperature fluctuations that are coherent with one another and with fully forced millennial model simulations from the Coupled Model Intercomparison Project Phase 5 across the Common Era. A substantial portion of pre-industrial (1300–1800 CE) variability at multidecadal timescales is attributed to volcanic aerosol forcing. Reconstructions and simulations qualitatively agree on the amplitude of the unforced global mean multidecadal temperature variability, thereby increasing confidence in future projections of climate change on these timescales. The largest warming trends at timescales of 20 years and longer occur during the second half of the twentieth century, highlighting the unusual character of the warming in recent decades."

[AbruptSLR]

From the first linked abstract from the 2019 EGU session on cascading tipping points I selected the second linked abstract to post here as it concludes that: "Despite chronological uncertainties, we find that the palaeoclimate evidence indicates early high latitude warming and impacts throughout the Earth System, …. Our synthesis demonstrates the high sensitivity of these tipping elements to climate warming, and suggests that immediate-future climates are precariously susceptible to analogous tipping cascades."

https://meetingorganizer.copernicus.org/EGU2019/orals/33082

https://meetingorganizer.copernicus.org/EGU2019/EGU2019-14095.pdf

[AbruptSLR]

As a follow-on to my last post, the linked abstract indicates that during the Eemian maximum the high Arctic was about four times warmer than the GMSTA at that time, while currently the high Arctic is only about two times warmer than the GMSTA.  As Arctic Amplification is a significant contributor to ECS, the linked abstract clearly indicates that as/when we approach Eemian conditions (GMSTA approximately equal to 2C) ECS will increase from what it has been in recent decades.

[AbruptSLR]

The linked article points out that the demand for cooling is expected to surge in the coming decades and that unless decision makers take climate change much more seriously than they current are, this surging demand for cooling will likely '… make the world hotter':

Title: "Guest post: Why demand for cooling could make the world hotter"

https://www.carbonbrief.org/guest-post-why-demand-for-cooling-could-make-the-world-hotter

Extract: "As records tumble across Europe in a second heatwave of the summer and as people across China and North America are also feeling the heat, we can literally sense how influential cooling is for our wellbeing, productivity and environment.

Cool buildings and vehicles, as well as cooling in industrial processes and “cold chains” that ensure our food and medicines are safe, are things we either take for granted or increasingly come to expect.

With demand for cooling expected to soar in major developing economies as the world becomes warmer and hundreds of millions of people become able to afford their first air conditioner, unmanaged cooling growth could cause a surge in greenhouse gas emissions and hamper our ability to manage global warming."

[AbruptSLR]

While the topic of the impact of Saharan dust on climate change is complex, as a simple rule of thumb, less dust in the future means more climate change (& more global warming).  Thus the factor that a meaningful percentage of climate model projections predict a significant decrease in Saharan dust generation, could well mean a higher climate sensitivity (than assumed by consensus climate science) in the coming decades:

Title: "What climate change means for globe-traveling Saharan dust"

https://www.dailyclimate.org/dust-in-the-wind-what-climate-change-means-for-globe-traveling-sahara-desert-dust-2639136457.html?rebelltitem=1#rebelltitem1

Extract: "There is currently no apparent trend in how much dust is blown away from the Sahara each year. Some decades, like the 1970s and 80s, have had more dust, while others had less. One study led by Evan tried to predict future dust amounts using computer modeling. A large fraction of the simulations, about 44 percent, showed a significant decrease in Saharan dust in the future."

Edit: I note that the cited research indicates that a reduction in Saharan dust production would both increase the number and the duration of Atlantic hurricane, and that both of these responses would likely advect more energy (through the atmosphere) from the Tropical Atlantic to the Arctic by hurricanes moving up the US Eastern seaboard; which would increase Arctic Amplification and consequently ECS.

[AbruptSLR]

If right-tail risks fatten in a cascade of tipping points, then the well over $2.1 trillion estimated to be spent on hardening of US infrastructure again extreme weather in the next five-years, may well be wasted and may likely act as a positive feedback to accelerate global warming (think of all the GHG generated to create all of that infrastructure hardening:

Title: "The coming $2.1 trillion extreme weather bonanza"

https://www.axios.com/coming-21-trillion-extreme-weather-bonanza-f6d7e2b3-ef87-44ca-939e-7cb743bf9114.html

Extract: "CDP's Sarda said that the five-year revenue estimate is actually likely to be larger than $2.1 trillion because that's only the sum from 224 companies that answered the survey in great detail. On top of those are roughly 6,775 companies that gave incomplete answers, in addition to the thousands or perhaps tens of thousands of startups yet to be created in response to the weather."

[Tom_Mazanec]

Here are the Canadian coasts most vulnerable in this century:
https://www.thestar.com/news/canada/2019/07/25/geoscientist-maps-out-the-canadian-coasts-where-climate-change-will-hit-hardest-this-century.html

[kassy]

the well over $2.1 trillion estimated to be spent on hardening of US infrastructure again extreme weather in the next five-years, may well be wasted and may likely act as a positive feedback to accelerate global warming

Cali has these nice cliff houses and they can safe the beaches or the cliffhouses but not both because crumbling cliffs give you nice beaches over time.

Anytime you do anything to the coast something further along the line changes. In the Netherlands we built these sand engines so we take some sand from somewhere and dump it around the coast.

To protect the West of the Netherlands against the sea, the beaches along the coast are artificially replenished every five years

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

There are many problematic east coast points in the US if cities use hard defenses. You add some life to the cities but you lose more natural barriers north.

[AbruptSLR]

While I appreciate the effort that consensus science is making by studying polar amplification with the PAMIP project (see the linked reference); this effort seems to me to err on the side of least drama by ignoring the ice-climate feedback mechanisms associated with ice mass loss from both ice shelves and ice sheets (also I note that Arctic Amplification was greater during the Eemian than the preliminary projections from PAMIP, which to me is more evidence that consensus climate science is erring on the side of least drama w.r.t. polar amplification):

Smith, D. M., Screen, J. A., Deser, C., Cohen, J., Fyfe, J. C., García-Serrano, J., Jung, T., Kattsov, V., Matei, D., Msadek, R., Peings, Y., Sigmond, M., Ukita, J., Yoon, J.-H., and Zhang, X.: The Polar Amplification Model Intercomparison Project (PAMIP) contribution to CMIP6: investigating the causes and consequences of polar amplification, Geosci. Model Dev., 12, 1139-1164, https://doi.org/10.5194/gmd-12-1139-2019, 2019.

https://www.geosci-model-dev.net/12/1139/2019/
https://www.geosci-model-dev.net/12/1139/2019/gmd-12-1139-2019.pdf

Abstract: "Polar amplification – the phenomenon where external radiative forcing produces a larger change in surface temperature at high latitudes than the global average – is a key aspect of anthropogenic climate change, but its causes and consequences are not fully understood. The Polar Amplification Model Intercomparison Project (PAMIP) contribution to the sixth Coupled Model Intercomparison Project (CMIP6; Eyring et al., 2016) seeks to improve our understanding of this phenomenon through a coordinated set of numerical model experiments documented here. In particular, PAMIP will address the following primary questions: (1) what are the relative roles of local sea ice and remote sea surface temperature changes in driving polar amplification? (2) How does the global climate system respond to changes in Arctic and Antarctic sea ice? These issues will be addressed with multi-model simulations that are forced with different combinations of sea ice and/or sea surface temperatures representing present-day, pre-industrial and future conditions. The use of three time periods allows the signals of interest to be diagnosed in multiple ways. Lower-priority tier experiments are proposed to investigate additional aspects and provide further understanding of the physical processes. These experiments will address the following specific questions: what role does ocean–atmosphere coupling play in the response to sea ice? How and why does the atmospheric response to Arctic sea ice depend on the pattern of sea ice forcing? How and why does the atmospheric response to Arctic sea ice depend on the model background state? What have been the roles of local sea ice and remote sea surface temperature in polar amplification, and the response to sea ice, over the recent period since 1979? How does the response to sea ice evolve on decadal and longer timescales?

A key goal of PAMIP is to determine the real-world situation using imperfect climate models. Although the experiments proposed here form a coordinated set, we anticipate a large spread across models. However, this spread will be exploited by seeking “emergent constraints” in which model uncertainty may be reduced by using an observable quantity that physically explains the intermodel spread. In summary, PAMIP will improve our understanding of the physical processes that drive polar amplification and its global climate impacts, thereby reducing the uncertainties in future projections and predictions of climate change and variability."

[AbruptSLR]

Yet another positive ice-climate feedback mechanism that consensus climate science has previously underestimated; in that the linked research indicates that Alaskan tidewater glaciers are losing mass 100 times faster than previously assumed:

D. A. Sutherland et al. (Jul 2019), "Direct observations of submarine melt and subsurface geometry at a tidewater glacier", Science  26, Vol. 365, Issue 6451, pp. 369-374
DOI: 10.1126/science.aax3528

https://science.sciencemag.org/content/365/6451/369

Abstract
Ice loss from the world’s glaciers and ice sheets contributes to sea level rise, influences ocean circulation, and affects ecosystem productivity. Ongoing changes in glaciers and ice sheets are driven by submarine melting and iceberg calving from tidewater glacier margins. However, predictions of glacier change largely rest on unconstrained theory for submarine melting. Here, we use repeat multibeam sonar surveys to image a subsurface tidewater glacier face and document a time-variable, three-dimensional geometry linked to melting and calving patterns. Submarine melt rates are high across the entire ice face over both seasons surveyed and increase from spring to summer. The observed melt rates are up to two orders of magnitude greater than predicted by theory, challenging current simulations of ice loss from tidewater glaciers.

See also:

Title: "Alaskan glaciers melting 100 times faster than previously thought"

https://www.nationalgeographic.com/environment/2019/07/alaskan-glaciers-melting-faster-than-previously-thought/

[nanning]

Thank you AbruptSLR for all the significant information.

[Rich]

Thank you AbruptSLR for all the significant information.

+1

The conclusion is not yet apparent in terms of how it will impact SLR projections, but it's always good to be aware of the progress in understanding melt of the non-floating ice.

I think after the current El Nino clears out, 2020 is going to give us a good look at the baseline SLR increase. Most of the non El-Nino years this decade have been in the 8mm / year range, far above the 3mm / year trendline.

Another year at or above the 8mm mark is going to start reverberating in financial markets. Flood insurance, coastal real estate, Muni bonds, property tax revenue, etc. The dominoes are lined up.

[AbruptSLR]

The Global Footprint Network calculates that today, July 29, 2019, is Earth Overshoot Day :

Title: "Earth Overshoot Day is July 29"

https://www.overshootday.org/

[AbruptSLR]

It looks like contrail cirrus radiative forcing will be several times more positive than previously assumed by consensus climate science:

Lisa Bock and Ulrike Burkhardt (2019), "Contrail cirrus radiative forcing for future air traffic", Atmos. Chem. Phys., 19, 8163-8174, https://doi.org/10.5194/acp-19-8163-2019

https://www.atmos-chem-phys.net/19/8163/2019/

Abstract
The climate impact of air traffic is to a large degree caused by changes in cirrus cloudiness resulting from the formation of contrails. Contrail cirrus radiative forcing is expected to increase significantly over time due to the large projected increases in air traffic. We use ECHAM5-CCMod, an atmospheric climate model with an online contrail cirrus parameterization including a microphysical two-moment scheme, to investigate the climate impact of contrail cirrus for the year 2050. We take into account the predicted increase in air traffic volume, changes in propulsion efficiency and emissions, in particular soot emissions, and the modification of the contrail cirrus climate impact due to anthropogenic climate change.

Global contrail cirrus radiative forcing increases by a factor of 3 from 2006 to 2050, reaching 160 or even 180 mW m−2, which is the result of the increase in air traffic volume and a slight shift in air traffic towards higher altitudes. Large increases in contrail cirrus radiative forcing are expected over all of the main air traffic areas, but relative increases are largest over main air traffic areas over eastern Asia. The projected upward shift in air traffic attenuates contrail cirrus radiative forcing increases in the midlatitudes but reinforces it in the tropical areas. Climate change has an insignificant impact on global contrail cirrus radiative forcing, while regional changes are significant. Of the emission reductions it is the soot number emission reductions by 50 % that lead to a significant decrease in contrail cirrus optical depth and coverage, leading to a decrease in radiative forcing by approximately 15 %. The strong increase in contrail cirrus radiative forcing due to the projected increase in air traffic volume cannot be compensated for by the decrease in initial ice crystal numbers due to reduced soot emissions and improvements in propulsion efficiency.

[AbruptSLR]

Virtually all consensus climate science models ignore the ice-climate feedback mechanisms associated with ice mass loss from ice shelves and ice sheet, but the linked reference about the Getz Ice Shelf finds that "… melting is enhanced where subglacial discharge freshwater flows across the grounding line."  This indicates yet another positive feedback as the basal meltwater form the marine glaciers flowing across the groundling line creates a syphon type effect to draw in more warm CDW to accelerate both the retreat of the grounding line and the ice melting from the underside of the ice shelves:

Wei, W., Blankenship, D. D., Greenbaum, J. S., Gourmelen, N., Dow, C. F., Richter, T. G., Greene, C. A., Young, D. A., Lee, S.-H., Kim, T.-W., Lee, W. S., Wåhlin, A., and Assmann, K. M.: Getz Ice Shelf melt enhanced by freshwater discharge from beneath the West Antarctic Ice Sheet, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-170, in review, 2019.

https://www.the-cryosphere-discuss.net/tc-2019-170/

Abstract. Antarctica's Getz Ice Shelf has been rapidly thinning in recent years, producing more meltwater than any other ice shelf in the world. The influx of freshwater is known to substantially influence ocean circulation and biological productivity, but relatively little is known about the factors controlling basal melt rate or how it is spatially distributed beneath the ice shelf. Also unknown is the relative importance of subglacial discharge from the grounded ice sheet in contributing to the export of freshwater from the ice shelf cavity. Here we compare the observed spatial distribution of basal melt rate to a new sub-ice shelf bathymetry map inferred from airborne gravity surveys and to locations of subglacial discharge from the grounded ice sheet. We find that melt rates are high where bathymetric troughs provide a pathway for warm Circumpolar Deep Water to enter the ice shelf cavity, and that melting is enhanced where subglacial discharge freshwater flows across the grounding line. This is the first study to address the relative importance of meltwater production of the Getz Ice Shelf from both ocean and subglacial sources.

[nanning]

Is there someone who has a list of all the positive feedbacks that have been found. What do all those positive feedbacks signify? Is it related to many observed phenomena we see happening earlier than expected?

[AbruptSLR]

The first linked article indicates that consensus climate scientists are not sure as to why recent methane emissions into the atmosphere are surging.

Title: "Earth's methane emissions are rising and we don't know why"

https://www.newscientist.com/article/2204466-earths-methane-emissions-are-rising-and-we-dont-know-why/

Extract: "Levels of a powerful greenhouse gas jumped again last year, continuing a surge in the past few years that researchers still cannot fully explain.

Atmospheric concentrations of methane climbed by 10.77 parts per billion in 2018, the second highest annual increase in the past two decades, according to provisional data released recently by US agency NOAA.

As, indicated by the last linked article, industry is under reporting their amounts of methane by as much as a factor of 100.  Maybe this has something to do with consensus climate scientists uncertainty on anthropogenic emission rates

Title: "Industrial methane emissions are 100 times higher than reported, researchers say"

https://phys.org/news/2019-06-industrial-methane-emissions-higher.html

Extract: "Emissions of methane from the industrial sector have been vastly underestimated, researchers from Cornell and Environmental Defense Fund have found."

[AbruptSLR]

Is there someone who has a list of all the positive feedbacks that have been found. What do all those positive feedbacks signify? Is it related to many observed phenomena we see happening earlier than expected?

The number of positive climate change feedback mechanisms are too numerous for the four linked Wikipedia articles to adequately cover.  Thus, you may be limited to scrolling back through this (& related) threads:

Title: "Climate change feedback"

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

&

Title: "Tipping points in the climate system"

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

&

Title: "Climate sensitivity"

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

&

Title: "Climate state"

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

Edit: As climate feedback mechanisms are too complex for current climate models to simulate our current risks of abrupt climate change, it is a good idea to examine the paleorecord:

Title: "Introduction to Abrupt Changes in the Earth’s Climate"

https://www.nap.edu/read/10136/chapter/3

&

Title: "Evidence of Abrupt Climate Change"

https://www.nap.edu/read/10136/chapter/4

&

Title: "Processes That Cause Abrupt Climate Change"

https://www.nap.edu/read/10136/chapter/5

[nanning]

Thank you very much ASLR for the links and an interesting book I didn't know Abrupt Climate Change: Inevitable Surprises (2002)

[AbruptSLR]

The linked reference concludes: "Our study thus emphasizes the general vulnerability of permafrost to abrupt decomposition, in particular the sea-level induced erosion, and the related potential to cause centennial-scale rises in atmospheric CO2, which might similarly happen in the future."  This research should remind us all that (as happen during Meltwater Pulses 1A & 1B) an abrupt increase in sea level due significant ice mass loss from Antarctica will likely lead to an abrupt (centennial) increase in GHG emissions from Arctic coastal permafrost degradation.  Consensus climate models do not currently consider this positive feedback mechanism:

Vera D Meyer et al. (2019), "Permafrost-carbon mobilization in Beringia caused by deglacial meltwater runoff, sea-level rise and warming", Environmental Research Letters, Vol 14, Number 8, https://doi.org/10.1088/1748-9326/ab2653

https://iopscience.iop.org/article/10.1088/1748-9326/ab2653

Abstract
During the last deglaciation (18–8 kyr BP), shelf flooding and warming presumably led to a large-scale decomposition of permafrost soils in the mid-to-high latitudes of the Northern Hemisphere. Microbial degradation of old organic matter released from the decomposing permafrost potentially contributed to the deglacial rise in atmospheric CO2 and also to the declining atmospheric radiocarbon contents (Δ14C). The significance of permafrost for the atmospheric carbon pool is not well understood as the timing of the carbon activation is poorly constrained by proxy data. Here, we trace the mobilization of organic matter from permafrost in the Pacific sector of Beringia over the last 22 kyr using mass-accumulation rates and radiocarbon signatures of terrigenous biomarkers in four sediment cores from the Bering Sea and the Northwest Pacific. We find that pronounced reworking and thus the vulnerability of old organic carbon to remineralization commenced during the early deglaciation (~16.8 kyr BP) when meltwater runoff in the Yukon River intensified riverbank erosion of permafrost soils and fluvial discharge. Regional deglaciation in Alaska additionally mobilized significant fractions of fossil, petrogenic organic matter at this time. Permafrost decomposition across Beringia's Pacific sector occurred in two major pulses that match the Bølling-Allerød and Preboreal warm spells and rapidly initiated within centuries. The carbon mobilization likely resulted from massive shelf flooding during meltwater pulses 1A (~14.6 kyr BP) and 1B (~11.5 kyr BP) followed by permafrost thaw in the hinterland. Our findings emphasize that coastal erosion was a major control to rapidly mobilize permafrost carbon along Beringia's Pacific coast at ~14.6 and ~11.5 kyr BP implying that shelf flooding in Beringia may partly explain the centennial-scale rises in atmospheric CO2 at these times. Around 16.5 kyr BP, the mobilization of old terrigenous organic matter caused by meltwater-floods may have additionally contributed to increasing CO2 levels.

[AbruptSLR]

Thank you very much ASLR for the links and an interesting book I didn't know Abrupt Climate Change: Inevitable Surprises (2002)

I should have previously noted that the 2002 NAS report on abrupt climate change was updated in 2013, as linked below:

NAS (2013) "Abrupt Impacts of Climate Change: Anticipating Surprises"

https://nas-sites.org/americasclimatechoices/other-reports-on-climate-change/abrupt-impacts-of-climate-change/

&

https://www.nap.edu/resource/18373/abrupt-climate-change-brief-FINAL-web.pdf

Edit, see also:

Title: "Abrupt climate change"

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

[AbruptSLR]

The linked reference implies that the stability of the ice in the Petermann catchment is likely less stable than consensus climate scientists currently assume:

Chambers, C., Greve, R., Altena, B., and Lefeuvre, P.-M.: On the possibility of a long subglacial river under the north Greenland ice sheet, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-141, in review, 2019.

https://www.the-cryosphere-discuss.net/tc-2019-141/

Abstract. Does a long subglacial river with a source deep in the interior of the Greenland ice sheet, drain into the sea at the Petermann Glacier grounding line? Basal topographic data shows a segmented valley extending from Petermann Fjord into the centre of Greenland, however the locations of radar scan lines, used to create the bedrock topography data, indicate that valley discontinuity is due to data interpolation. Simulations where the valley is opened are used to investigate effects on basal water and ice sheet sliding. The simulations indicate that the opening of this valley results in an uninterrupted water pathway from the interior along the valley that alters ice sheet sliding in the Petermann catchment and in areas of west Greenland. Along its length, the path of the valley progresses gradually down an ice surface slope causing a lowering of ice overburden pressure that could enable water flow along its path. The fact that the valley base appears to be relatively flat and follows a path along the interior ice divide that intersects the east and west basal hydrological basins, is presented as evidence that its present day form developed as a consequence of the overlying ice sheet rather than prior to ice sheet inception. Though considerable uncertainty remains, the results are consistent with a present day active long subglacial river system. The results raise issues concerning the need to better observe, understand, and simulate the complicated basal hydrology of the Greenland and other ice sheets.

[AbruptSLR]

While the linked article indicates that the amount of carbon emissions from current Arctic wildfires are unprecedented in the observed record.  This trend is likely to continue with continued global warming:

Title: "The Bizarre, Peaty Science of Arctic Wildfires"

https://www.wired.com/story/the-bizarre-peaty-science-of-arctic-wildfires/?verso=true

Extract: "“Arctic fires are rare, but they're not unprecedented. What is unprecedented is the number of fires that are happening. Never before have satellites around the planet seen this level of activity.”

Unprecedented, yes, but not unexplained. The Arctic is warming twice as fast as the rest of the planet, leading to the desiccation of vegetation, which fuels huge blazes. Fortunately for us, these wildfires typically threaten remote, sparsely populated areas. But unfortunately for the whole of humanity, so far this year Arctic fires have released some 121 megatonnes of CO2 into the atmosphere, more than what Belgium emits annually. That beats the previous Arctic record of 110 megatonnes of CO2, set in 2004—and we’re only in June."

[AbruptSLR]

We should all remember that new technologies are dramatically improving the fossil fuel industry's capability to continue to find and produce fossil fuel at marketable rates (even in the face of the growing use of sustainable energy).  Thus without adequate policy, anthropogenic GHG emissions are likely to continue along their current BAU pathway for at least several decades to come:

Title: "Drones could save the oil industry $50 billion"

https://www.axios.com/drones-oil-industry-impact-088b9e58-bcb0-4e48-882b-fa33e32fa753.html

Extract: "The oil-and-gas industry could realize $50 billion in cost-savings from wider deployment of drones over the next 5 years, a new Barclays report finds.

Why it matters: It's the sector that could see the greatest cost reductions over that period, as a "convergence" of tech developments — 5G, remote computing and AI — enable wider drone use in many industries."

[RoxTheGeologist]

I think if you really want to know where we are heading with emissions you simply have to follow the money, and investment banks have yet to actually stop funding oil, coal and gas infrastructure, and we have yet to control deforestation and industrial farming. It's not looking good.

That infrastructure has a long lead time to spend the money, 2 years or so, and then usually has a ROI over 10 years and thereafter it makes money. If the money is still flowing towards oil and gas how can we expect emissions to stop growing?

[AbruptSLR]

People should remember that climate sensitivity not only increases with increasingly positive feedback, but also with decreasingly negative feedbacks.  Furthermore, as climate sensitivity increases with increasing feedback variability, the fact that CO2 absorption by both land and ocean is more sensitive to climate variability than current thought by consensus science means that climate sensitivity is likely to increase faster than thought by consensus science due to possible future degradation of carbon sinks:

Tim DeVries, Corinne Le Quéré, Oliver Andrews, Sarah Berthet, Judith Hauck, Tatiana Ilyina, Peter Landschützer, Andrew Lenton, Ivan D. Lima, Michael Nowicki, Jörg Schwinger, and Roland Séférian (May 28, 2019), "Decadal trends in the ocean carbon sink", PNAS June 11, 2019 116 (24) 11646-11651; https://doi.org/10.1073/pnas.1900371116

https://www.pnas.org/content/116/24/11646

Significance
The ocean and land absorb anthropogenic CO2 from industrial fossil-fuel emissions and land-use changes, helping to buffer climate change. Here, we compare decadal variability of ocean CO2 uptake using three independent methods and find that the ocean could be responsible for as much as 40% of the observed decadal variability of CO2 accumulation in the atmosphere. The remaining variability is due to variability in the accumulation of carbon in the terrestrial biosphere. Models capture these variations, but not as strongly as the observations, implying that CO2 uptake by the land and ocean is more sensitive to climate variability than currently thought. Models must capture this sensitivity to provide accurate climate predictions.

Abstract
Measurements show large decadal variability in the rate of CO2 accumulation in the atmosphere that is not driven by CO2 emissions. The decade of the 1990s experienced enhanced carbon accumulation in the atmosphere relative to emissions, while in the 2000s, the atmospheric growth rate slowed, even though emissions grew rapidly. These variations are driven by natural sources and sinks of CO2 due to the ocean and the terrestrial biosphere. In this study, we compare three independent methods for estimating oceanic CO2 uptake and find that the ocean carbon sink could be responsible for up to 40% of the observed decadal variability in atmospheric CO2 accumulation. Data-based estimates of the ocean carbon sink from pCO2 mapping methods and decadal ocean inverse models generally agree on the magnitude and sign of decadal variability in the ocean CO 2 sink at both global and regional scales. Simulations with ocean biogeochemical models confirm that climate variability drove the observed decadal trends in ocean CO2 uptake, but also demonstrate that the sensitivity of ocean CO 2 uptake to climate variability may be too weak in models. Furthermore, all estimates point toward coherent decadal variability in the oceanic and terrestrial CO2 sinks, and this variability is not well-matched by current global vegetation models. Reconciling these differences will help to constrain the sensitivity of oceanic and terrestrial CO2 uptake to climate variability and lead to improved climate projections and decadal climate predictions.

[AbruptSLR]

We should all remember that the concept of cascading tipping points not only applies to climate sensitivity but also to coming potential society instabilities, as discussed in the linked article:

Title: "Lost Cities and Climate Change" by Kate Marvel (2019)

https://blogs.scientificamerican.com/hot-planet/lost-cities-and-climate-change/?amp;text=Lost

Extract: "… the adversity brought by climate change caused societies to break apart, magnified pre-existing divisions, and made desperate people easy prey for dangerous people.

“The climate has changed before,” say people who want to minimize the scale of the current challenge. I have never understood how anyone could find this comforting. The natural climate changes that have shaped human history have almost always been smaller and more regionally contained than the large-scale human-caused change we are currently experiencing. And even these changes have provoked suffering, scapegoating, and the collapse of civilizations.

I am often asked what frightens me most about climate change, whether I lie awake at night thinking about ocean hypoxia or arctic permafrost or other feedback processes that could turn a bad thing into a catastrophe. I am scared of the physical changes that await us on a warming planet, but the most important feedback process is the least well understood. The scariest thing about climate change is what it will make us do to each other."

[AbruptSLR]

More Arctic oil and gas developments are underway in Russia:

Title: "Russia’s biggest oil company announces more offshore Arctic drilling"

https://thebarentsobserver.com/en/industry-and-energy/2019/07/russias-biggest-oil-company-announces-more-offshore-arctic-drilling

Extract: "Five years after it found one of the largest oil fields in Arctic waters, Rosneft makes clear that more drilling in the Kara Sea is coming up."

[AbruptSLR]

Science did us all a favor by identifying the need to protect the ozone layer; which then lead to the adoption of the 1987 Montreal Protocol, and many consensus scientists point to this as an example of why we should all have confidence that the existing gestalt between consensus scientist and decision makers will prevent other possible climate tipping points from abruptly occurring.  However, it is premature for such consensus climate scientist from taking a victory lap about the success of the Montreal Protocol, particularly with regard to the recovery of the Antarctic ozone hole, as discussed in the linked reference.

The Antarctic ozone hole plays a critical role in potentially/likely triggering an ice apocalypse, by accelerating the Antarctic westerly winds (since the late 1970s); which has accelerated the upwelling of warm CDW that has accelerated the risk of an MICI-type of collapse of the WAIS.  Furthermore, an increase in atmospheric GHG concentrations also accelerates the Antarctic wind velocities, and as there is a sweet spot for the westerly wind velocity w.r.t. the upwelling of warm CDW; the fact that the recovery of the Antarctic ozone hole will be strung-out over several decades to come means the if the GHG emission continue for several more decades, the westerly wind velocities will likely stay in their current sweet spot, thus greatly increasing the risk of an ice apocalypse in the next several decades.

Xuekun Fang et al. (2019), "Challenges for the recovery of the ozone layer", Nature Geoscience,  12, 592–596, DOI: https://doi.org/10.1038/s41561-019-0422-7

https://www.nature.com/articles/s41561-019-0422-7

Abstract: "The recovery of stratospheric ozone from past depletion is underway owing to the 1987 Montreal Protocol and its subsequent amendments, which have been effective in phasing out the production and consumption of the major ozone-depleting substances (ODSs). However, there is uncertainty about the future rate of recovery. This uncertainty relates partly to unexpected emissions of controlled anthropogenic ODSs such as CCl3F and slower-than-expected declines in atmospheric CCl4. A further uncertainty surrounds emissions of uncontrolled short-lived anthropogenic ODSs (such as CH2Cl2 and CHCl3), which observations show have been increasing in the atmosphere through 2017, as well as potential emission increases in natural ODSs (such as CH3Cl and CH3Br) induced by climate change, changes in atmospheric concentrations of greenhouse gases N2O and CH4, and stratospheric geoengineering. These challenges could delay the return of stratospheric ozone levels to historical values, (for example, the abundance in 1980), by up to decades, depending on the future evolution of the emissions and other influencing factors. To mitigate the threats to future ozone recovery, it is crucial to ensure that the Montreal Protocol and its amendments continue to be implemented effectively in order to have firm control on future levels of ODSs. This action needs to be supported by an expansion of the geographic coverage of atmospheric observations of ODSs, by enhancing the ability of source attribution modelling, and by improving understanding of the interactions between climate change and ozone recovery."

[AbruptSLR]

This is just a reminder that the early CMIP6 evaluations of ECS have come in at a likely range of from 2.8C to 5.8C; and that these CMIP6 projection ignore the potential ice-climate feedbacks from a possible MICI-type of collapse of the WAIS beginning in the coming decades:

Title: "Guest post: Why results from the next generation of climate models matter"

https://www.carbonbrief.org/guest-post-why-results-from-the-next-generation-of-climate-models-matter

Extract: "Early results suggest ECS values from some of the new CMIP6 climate models are higher than previous estimates, with early numbers being reported between 2.8C (pdf) and 5.8C. This compares with the previous coupled model intercomparison project (CMIP5), which reported values between 2.1C to 4.7C. The IPCC’s fifth assessment report (AR5) assessed ECS to be “likely” in the range 1.5C to 4.5C and “very unlikely” greater than 6C. (These terms are defined using the IPCC methodology.)"

Image Caption: "Assessment range for ECS from IPCC AR5 (blue bar; thick bar denotes likely range, thin bar extending from it shows values below which ECS is “extremely unlikely” and above which ECS is “very unlikely”), range from CMIP5 (orange bar) and preliminary estimates of ECS values from new global climate models (red bar)."

See also:

Title: "International climate scientists discuss first results from a new set of climate model simulations at the CMIP6 Model Analysis Workshop in Barcelona, Spain"

https://www.wcrp-climate.org/news/wcrp-news/1478-cmip6-first-results

[AbruptSLR]

The attached abstract provides an update on progress being made to calibrate the DOMINOS (Disintegration of Marine Ice Sheet: Novel Optimized Simulations) model

https://meetingorganizer.copernicus.org/EGU2019/EGU2019-15396.pdf

See also:

Memon, S., Vallot, D., Zwinger, T., Åström, J., Neukirchen, H., Riedel, M., and Book, M.: Scientific workflows applied to the coupling of a continuum (Elmer v8.3) and a discrete element (HiDEM v1.0) ice dynamic model, Geosci. Model Dev., 12, 3001-3015, https://doi.org/10.5194/gmd-12-3001-2019, 2019.

https://www.geosci-model-dev.net/12/3001/2019/
https://www.geosci-model-dev.net/12/3001/2019/gmd-12-3001-2019.pdf

Abstract: "Scientific computing applications involving complex simulations and data-intensive processing are often composed of multiple tasks forming a workflow of computing jobs. Scientific communities running such applications on computing resources often find it cumbersome to manage and monitor the execution of these tasks and their associated data. These workflow implementations usually add overhead by introducing unnecessary input/output (I/O) for coupling the models and can lead to sub-optimal CPU utilization. Furthermore, running these workflow implementations in different environments requires significant adaptation efforts, which can hinder the reproducibility of the underlying science. High-level scientific workflow management systems (WMS) can be used to automate and simplify complex task structures by providing tooling for the composition and execution of workflows – even across distributed and heterogeneous computing environments. The WMS approach allows users to focus on the underlying high-level workflow and avoid low-level pitfalls that would lead to non-optimal resource usage while still allowing the workflow to remain portable between different computing environments. As a case study, we apply the UNICORE workflow management system to enable the coupling of a glacier flow model and calving model which contain many tasks and dependencies, ranging from pre-processing and data management to repetitive executions in heterogeneous high-performance computing (HPC) resource environments. Using the UNICORE workflow management system, the composition, management, and execution of the glacier modelling workflow becomes easier with respect to usage, monitoring, maintenance, reusability, portability, and reproducibility in different environments and by different user groups. Last but not least, the workflow helps to speed the runs up by reducing model coupling I/O overhead and it optimizes CPU utilization by avoiding idle CPU cores and running the models in a distributed way on the HPC cluster that best fits the characteristics of each model."

[AbruptSLR]

For your consideration from E3SM:

Title: "Disturbance at the Threshold: When Does Tree Mortality Break the Forest Carbon Cycle?" by Chris Gough

https://www.youtube.com/watch?v=d7sVosXLGAE&feature=youtu.be

[AbruptSLR]

It likely will be difficult for countries to leave Arctic oil & gas reserves untapped:

Title: "Why Is There So Much Oil in the Arctic?"

https://www.livescience.com/66008-why-oil-in-arctic.html

Extract: "In 2007, two Russian submarines plunged down 2.5 miles (4 kilometers) into the Arctic Ocean and planted a national flag onto a piece of continental shelf known as the Lomonosov Ridge. Rising from the center of the Arctic Basin, the flag sent a clear message to the surrounding nations: Russia had just laid claim to the vast oil and gas reserves contained in this underwater turf.

Russia's dramatic show of power had no legal weight — but it isn't the only nation that's trying to stake claims to the Arctic's vast depository of oil and gas. The United States, Norway, Sweden, Finland and China are all trying to cash in. It's no wonder: Projections show that the area of land and sea that falls within the Arctic Circle is home to an estimated 90 billion barrels of oil, an incredible 13% of Earth's reserves. It's also estimated to contain almost a quarter of untapped global gas resources.

Most of the oil that's been located in this region so far is on the land, just because it's easier to access. But now, countries are making moves to start extracting offshore, where the vast majority — 84% — of the energy is believed to occur.
...
And it could be a hard sell to make countries see that those reserves should remain untapped. In short, said Fraser, "I hope this region doesn't become too important [for energy production].""

[Stephan]

Hasn't it been stated some years ago from scientists, that ca. 70-80% of the already known gas, oil and coal reserves must be kept underground to prevent the earth to go beyond the 2°C goal?
So if further nations and companies explore new oil and gas reserves in the Arctic, they probably will  extract it, which will produce more CO₂. Who is able to stop them?

[DrTskoul]

Hasn't it been stated some years ago from scientists, that ca. 70-80% of the already known gas, oil and coal reserves must be kept underground to prevent the earth to go beyond the 2°C goal?
So if further nations and companies explore new oil and gas reserves in the Arctic, they probably will  extract it, which will produce more CO₂. Who is able to stop them?

They will extract it if there is demand. Make sure there is no demand. Stop all activities that use oil...

[AbruptSLR]

While complete Arctic sea ice loss is not guaranteed, the linked reference calculates that if this were to occur in the coming decades then the incremental increase of this one feedback alone would be the equivalent of 25 years of anthropogenic GHG emissions at the current rates.

Kristina Pistone et al. (20 June 2019), "Radiative Heating of an Ice‐Free Arctic Ocean", Geophysical Research Letters, https://doi.org/10.1029/2019GL082914

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL082914

Abstract: "During recent decades, there has been dramatic Arctic sea ice retreat. This has reduced the top‐of‐atmosphere albedo, adding more solar energy to the climate system. There is substantial uncertainty regarding how much ice retreat and associated solar heating will occur in the future. This is relevant to future climate projections, including the timescale for reaching global warming stabilization targets. Here we use satellite observations to estimate the amount of solar energy that would be added in the worst‐case scenario of a complete disappearance of Arctic sea ice throughout the sunlit part of the year. Assuming constant cloudiness, we calculate a global radiative heating of 0.71 W/m2 relative to the 1979 baseline state. This is equivalent to the effect of one trillion tons of CO2 emissions. These results suggest that the additional heating due to complete Arctic sea ice loss would hasten global warming by an estimated 25 years."