Ice Apocalypse - Multiple Meters Sea Level Rise

[Lennart van der Linde]

While AbruptSLR is doing a great job in highlighting potential dangers of climate change, he is focusing on the very low-probability extreme climate change scenarios. If you read the articles he links to, they often focus on hypothetical extreme model runs to show what could happen in the case of runaway carbon emissions. He has recently posted papers with 4 times increases in CO2 concentrations and 5 or 11 times increases in methane concentrations. Those are scenarios well beyond even the extremes of RCP 8.5.
[...]
Also, renewable energy is now cheaper than coal and is quickly becoming cheaper than natural gas and EVs are poised to outsell ICEs in the coming decade. As a result, we're probably going to end up on an emissions path between RCP 2.6 and 4.5.
So there are many reasons to hope. I agree with AbruptSLR and many posters on this site that we need to get off of fossil fuels as quickly as possible and I also agree with the consensus climate scientists that it's not too late. Don't give up hope.

I never read ASLR's posts as a reason for despair. On the contrary: he shows the urgency of taking the collective action that can at this point hopefully still prevent the worst-case risks from materializing. Many mainstream communications focus on current best-estimates, without being or making people aware of the severe fat tail risks. Sutton 2018 proposes to improve on this lack of clear risk communication by using this simple figure below that shows the probability of very high climate sensitivity and its likely impacts, concluding that the highest risk is in the small, but significant chance of very high climate sensitivity and related impacts:
https://www.earth-syst-dynam.net/9/1155/2018/

Not being aware of this risk increases the chance of insufficient collective climate action (mitigation and adaptation), and would therefore increase the chance of eventual depair, in case worst-case scenario's would turn into reality. Since we don't know the real probability distribution for sure, we're in a situation of deep uncertainty, which makes strong climate action all the more urgent as a precaution against finding out that a high climate sensitivity appears to be more likely than mainstream science thought so far.

[gerontocrat]

...

Abrupt SLR,

Cheer me up. Are there any significant -ve feedbacks that do not require active input by us humans that could at least slow Armageddon for a day or two?

While there are many negative climate change feedback mechanisms (see the linked article), some people feel comforted by that fact that currently global warming is increasing Net Primary Productivity of plants; which might be beneficial if society can some how follow a SSP1-type of pathway (see the attached image) sooner rather than later:

Title: "Climate change feedback"

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

Extract: "Net Primary Productivity
Net primary productivity changes in response to increased CO2, as plants photosynthesis increased in response to increasing concentrations. However, this effect is swamped by other changes in the biosphere due to global warming."

Thanks AbruptSLR for trying.

The link shown by you is the one I found last week. I have to say it felt like being on a bicycle playing chicken against a Mack Truck. I guess it was a forlorn hope.

As the cliché has it - "It is what it is".

While AbruptSLR is doing a great job in highlighting potential dangers of climate change, he is focusing on the very low-probability extreme climate change scenarios.  If you read the articles he links to, they often focus on hypothetical extreme model runs to show what could happen in the case of runaway carbon emissions.  He has recently posted papers with 4 times increases in CO2 concentrations and 5 or 11 times increases in methane concentrations.

But then one reads about the Royal Meteorological Society meeting on the climate of the Pliocene on April 3, i.e. today.

The important message is that these dire effects manifested with CO2 at around 400  ppm, i.e. without massive increases in CO2 or methane emissions.

https://www.theguardian.com/science/2019/apr/03/south-pole-tree-fossils-indicate-impact-of-climate-change
Last time CO2 levels were this high, there were trees at the South Pole

Trees growing near the South Pole, sea levels 20 metres higher than now, and global temperatures 3C-4C warmer. That is the world scientists are uncovering as they look back in time to when the planet last had as much carbon dioxide in the atmosphere as it does today.

Using sedimentary records and plant fossils, researchers have found that temperatures near the South Pole were about 20C higher than now in the Pliocene epoch, from 5.3m to 2.6m years ago.

Many scientists use sophisticated computer models to predict the impacts of human-caused climate change, but looking back in time for real-world examples can give new insights.

The Pliocene was a “proper analogy” and offered important lessons about the road ahead, said Martin Siegert, a geophysicist and climate-change scientist at Imperial College London. “The headline news is the temperatures are 3-4C higher and sea levels are 15-20 metres higher than they are today. The indication is that there is no Greenland ice sheet any more, no West Antarctic ice sheet and big chunks of East Antarctic [ice sheet] taken,” he said.

[wdmn]

While AbruptSLR is doing a great job in highlighting potential dangers of climate change, he is focusing on the very low-probability extreme climate change scenarios. If you read the articles he links to, they often focus on hypothetical extreme model runs to show what could happen in the case of runaway carbon emissions. He has recently posted papers with 4 times increases in CO2 concentrations and 5 or 11 times increases in methane concentrations. Those are scenarios well beyond even the extremes of RCP 8.5.
[...]
Also, renewable energy is now cheaper than coal and is quickly becoming cheaper than natural gas and EVs are poised to outsell ICEs in the coming decade. As a result, we're probably going to end up on an emissions path between RCP 2.6 and 4.5.
So there are many reasons to hope. I agree with AbruptSLR and many posters on this site that we need to get off of fossil fuels as quickly as possible and I also agree with the consensus climate scientists that it's not too late. Don't give up hope.

I never read ASLR's posts as a reason for despair. On the contrary: he shows the urgency of taking the collective action that can at this point hopefully still prevent the worst-case risks from materializing. Many mainstream communications focus on current best-estimates, without being or making people aware of the severe fat tail risks. Sutton 2018 proposes to improve on this lack of clear risk communication by using this simple figure below that shows the probability of very high climate sensitivity and its likely impacts, concluding that the highest risk is in the small, but significant chance of very high climate sensitivity and related impacts:
https://www.earth-syst-dynam.net/9/1155/2018/

Not being aware of this risk increases the chance of insufficient collective climate action (mitigation and adaptation), and would therefore increase the chance of eventual depair, in case worst-case scenario's would turn into reality. Since we don't know the real probability distribution for sure, we're in a situation of deep uncertainty, which makes strong climate action all the more urgent as a precaution against finding out that a high climate sensitivity appears to be more likely than mainstream science thought so far.

Very well said Lennart; probabilities with deep uncertainty really don't tell us much beyond the current state of our thinking. Or in this case, the current state of thinking that all the panelists (and the political overseers) on the IPCC can agree on.

[rboyd]

I find AbruptSLR to be a refreshing break from the UN Climate Circus prognostications, which continually use sleights of hand (ignoring increased natural emissions, restrictive confidence intervals, low values for climate sensitivity, ignoring the growth in methane levels, assumptions of massive rollouts of hypothetical technologies, assuming a frictionless rollout of renewables etc.) to be able to say that "we can still do it and keep growing" from every report.

His posts remind us that there definitely are possible climate devils out there which we should not be taking the risk of triggering - i.e. The Precautionary Principle. In addition the scientific community/policy keeps taking its time to catch up to the likes of Hansen and others.

[AbruptSLR]

While AbruptSLR is doing a great job in highlighting potential dangers of climate change, he is focusing on the very low-probability extreme climate change scenarios.
...

Fat-tailed risk means different things to different people.  The first image is from: NAS (2013), "Abrupt Impacts of Climate Change: Anticipating Surprises - Chapter: 4 The Way Forward"; which makes it clear that the NAS (National Academy of Sciences) believes that right-sided, fat-tailed risk can be much higher than that for normal risk distributions commonly assumed by consensus science.

https://www.nap.edu/read/18373/chapter/6#151

Caption for first image: "FIGURE The graph on the left represents the skewed distribution of uncertainties with a “fat tail.” The mean likelihood of occurrence at the level of severity anticipated is represented by a dotted line. The area to the left of the mean represents the likelihood for impacts less severe (the “a little better” case), while the area to the right shows the greater likelihood for extreme impacts (spanning “a little worse” to “a lot worse” cases). The graph on the right compares the normal distribution (black line) to the “fat tail” distribution (blue line). For some changes, more research has shown that the distribution of possible outcomes includes less likelihood of the most severe outcomes."

Three reasons why I concur with the NAS that we should anticipate abrupt climate change risk, are:
1. As shown in the second image, ice-climate feedback is increasingly conveying warm Circumpolar Deep Water, CDW, towards the grounding lines of key WAIS marine glaciers.

2. As shown in the third image, if we stay on SSP5-baseline through about 2035 then we will exceed a GMSTA of 2C by 2040; which approximately matches Mid-Pliocene conditions.

3. As shown in the fourth image, Pollard, DeConto & Alley (2018) have calculated a rapid MICI-type of abrupt ice mass loss primarily from the WAIS, once we approximately reach Mid-Pliocene conditions.

[Sleepy]

Since we all know how 2018 ended (emissions wise), here's a nice and simple animation of our collective climate actions since 1965 by Robert Wilson:
https://twitter.com/countcarbon/status/1112430555021434882

Also noticeable are the disturbances caused by economic crises.

[AbruptSLR]

The linked reference (with my emphasis added to the abstract) highlights the critical nature, and the challenges, of climate scientists communicating climate change risk to the public.  In this regard, I think that it is critical to protect the intrinsic motivation of climate scientists, from politics, and to my mind this means that the public needs to vote out of office denialist leaders (such as those promoting the Keystone pipeline, etc.) and to vote into to office leaders who recognize and defend the integrity of the scientific process:

Entradas et al. "Public communication by climate scientists: what, with whom and why?", Climatic Change, pp 1–17, DOI https://doi.org/10.1007/s10584-019-02414-9

https://rd.springer.com/article/10.1007%2Fs10584-019-02414-9

Abstract: "Public communication of science has increasingly been recognised as a responsibility of scientists (Leshner, Science p. 977, 2003). Climate scientists are often reminded of their responsibility to participate in the public climate debate and to engage the public in meaningful conversations that contribute to policy-making (Fischhoff 2013). However, our understanding about climate scientists’ interactions with the public and the factors that drive or inhibit them is at best limited. In a new study, we show that it is the most published and not necessarily the most senior, which often talk in public, and it is primarily intrinsic motivation (as opposed to extrinsic reward), which drive them to engage in public communication. Political orientations, academic productivity and awareness of controversy, the topic raises in the public domain, were also important determinants of a climate’s scientist public activity. Future research should explore what is required to protect the intrinsic motivation of scientists."

[AbruptSLR]

In the way of communicating with the public, Netflix is starting a new miniseries documentary entitled "Our Planet", and the linked clip introduces the episode on glaciers (focused on marine glaciers).  The beauty and artistry shown in this miniseries will keep the public engaged while they subconsciously get the message that urgent action is needed:

Title: "Our Planet – Glacier"

[AbruptSLR]

The first image shows selected NOAA ONI values thru JFM of 2019; which confirms that the 2018-19 ENSO season officially registered an El Nino event.  Typically, the boreal spring GMSTA temperatures following an El Nino event are higher than normal which is indicated by the second image showing NCEP/NCAR daily values of GMSTA thru April 3, 2019.  This implies that the GMSTA for 2019 are very likely going to be above average as predicted by Gavin Schmidt in the third image (which also indicates that we are collective approaching the aspirational 1.5C goal very quickly).

[AbruptSLR]

The first attached image from the linked Twitter feed, shows various SLR projections.  In this image the intermediate ranges have two values where the indicated report gave most likely SLR values both with, and without, MICI behavior.  To me the drop in projected SLR from FAR (1990) to AR4 (2007) [& to AR5 (2013)] was politically driven; while the subsequent increase in projected SLR shown in NCA4 (2017) is based on the current state of ice sheet modeling capabilities.

https://twitter.com/AGrinsted/status/1087708547729768450

Furthermore, the second attached image gives numerical values for 2017 projected SLR values; with values as high a 2.5m by 2100, when following RCP 8.5.  I suspect that in coming years, the current SLR projections will increase to still higher values:

https://science2017.globalchange.gov/chapter/12/

[AbruptSLR]

The consequence of that warming is seen in Banks Island thaw slumps:  Extremes of summer climate trigger thousands of thermokarst landslides in a High Arctic environment
  Antoni G. Lewkowicz & Robert G. Way  -  Nature Communications volume 10, Article number: 1329 (2019)

Abstract:

Retrogressive thaw slumps (RTS) – landslides caused by the melt of ground ice in permafrost – have become more common in the Arctic, but the timing of this recent increase and its links to climate have not been fully established. Here we annually resolve RTS formation and longevity for Banks Island, Canada (70,000 km2) using the Google Earth Engine Timelapse dataset. We describe a 60-fold increase in numbers between 1984 and 2015 as more than 4000 RTS were initiated, primarily following four particularly warm summers. Colour change due to increased turbidity occurred in 288 lakes affected by RTS outflows and sediment accumulated in many valley floors. Modelled RTS initiation rates increased by an order of magnitude between 1906–1985 and 2006–2015, and are projected under RCP4.5 to rise to >10,000 decade−1 after 2075. These results provide additional evidence that ice-rich continuous permafrost terrain can be highly vulnerable to changing summer climate.

paper and pictures at link

The following linked article elaborates on this topic:

Title: "Guest post: Arctic warming is causing a 60-fold increase in permafrost landslides"

https://www.carbonbrief.org/guest-post-arctic-warming-causing-60-fold-increase-permafrost-landslides

[AbruptSLR]

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

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

https://thwaitesglacier.org/projects/dominos

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

The linked reference provides field data of how 'melt-under-cutting' can control calving of relevant marine glaciers.  As the subglacial meltwater exits the Thwaites Glacier at the base of the Thwaites Ice Tongue, I believe that this data will be useful for helping the DOMINOS computer program to project the rate of future calving in this critical area of Thwaites once the ice tongue degrades sufficiently:

Penelope How et al. (30 January 2019), "Calving controlled by melt-under-cutting: detailed calving styles revealed through time-lapse observations", Annals of Glaciology, https://doi.org/10.1017/aog.2018.28

https://www.cambridge.org/core/journals/annals-of-glaciology/article/calving-controlled-by-meltundercutting-detailed-calving-styles-revealed-through-timelapse-observations/237F39F3239C4B9A04589D34BA5C93E5

Abstract: "We present a highly detailed study of calving dynamics at Tunabreen, a tidewater glacier in Svalbard. A time-lapse camera was trained on the terminus and programmed to capture images every 3 seconds over a 28-hour period in August 2015, producing a highly detailed record of 34 117 images from which 358 individual calving events were distinguished. Calving activity is characterised by frequent events (12.8 events h−1) that are small relative to the spectrum of calving events observed, demonstrating the prevalence of small-scale calving mechanisms. Five calving styles were observed, with a high proportion of calving events (82%) originating at, or above, the waterline. The tidal cycle plays a key role in the timing of calving events, with 68% occurring on the falling limb of the tide. Calving activity is concentrated where meltwater plumes surface at the glacier front, and a ~ 5 m undercut at the base of the glacier suggests that meltwater plumes encourage melt-under-cutting. We conclude that frontal ablation at Tunabreen may be paced by submarine melt rates, as suggested from similar observations at glaciers in Svalbard and Alaska. Using submarine melt rate to calculate frontal ablation would greatly simplify estimations of tidewater glacier losses in prognostic models."

Edit, see also:

M. Temminghoff et al. (2018), "Characterization of the englacial and subglacial drainage system in a high Arctic cold glacier by speleological mapping and ground-penetrating radar", Geografiska Annaler: Series A, Physical Geography, https://doi.org/10.1080/04353676.2018.1545120

https://www.tandfonline.com/doi/abs/10.1080/04353676.2018.1545120?journalCode=tgaa20

Abstract: "This paper presents new data obtained by speleological surveys and ground-penetrating radar (GPR) on a cut-and-closure conduit in Scott Turnerbreen, a small cold glacier in Svalbard, Norwegian Arctic. We use these data to propose criteria for the identification of cut-and-closure conduits from GPR data. In addition, we describe subglacial and englacial structures exposed in the conduit, which shed light on the former dynamic behaviour of the glacier. The glacier bed consists of a thick layer of subglacial traction till, from which till-filled fractures extend upward into the ice. These observations show that Scott Turnerbreen was formerly warm-based, and are consistent with a surge or surge-like behaviour. The channel system was also imaged using GPR. Varying channel morphologies have distinctive signatures on GPR profiles, allowing the identification and mapping of englacial drainage systems in situations where direct access is impossible."

[AbruptSLR]

If you want to know a little more about tipping point risks, visit John Englander's archives on this topic at:

Title: "tipping point archives"

https://www.johnenglander.net/sea-level-rise-blog/tag/tipping-point/

Extract: "Greenland’s Ice is Melting Four Times Faster than Thought—What it Means – National Geographic"

[AbruptSLR]

As pointed out in the linked article, we do not know what the Earth tipping point is to trigger a domino-effect of positive feedback mechanisms; which is why we should stay well below 2C (say 1.5C) at all times.

Title: "Why Positive Climate Feedbacks Are So Bad"

https://www.wri.org/blog/2018/08/why-positive-climate-feedbacks-are-so-bad

Extract: "Unfortunately, we don’t know exactly where the planetary thresholds lie. Scientists (including the Hothouse Earth authors) believe they are likely to be near 2 degrees C and that the risks increase dramatically above that level of global warming. But we can’t rule out the possibility that it is closer at hand. Hence the goal of the Paris Climate agreement to stay well below 2 degrees C and attempt to limit warming to 1.5 degrees C (2.7 degrees F)."

[AbruptSLR]

The linked reference demonstrates that the expansion of US croplands (primarily into grasslands) between 2008 and 2012, markedly increased carbon emissions (primarily from soil organic carbon stocks).  With the increasing world population demanding more food, we can expect future similar land use changes will also increase carbon emissions:

Seth A Spawn et al. (2019), "Carbon emissions from cropland expansion in the United States", Environmental Research Letters, Vol. 14, No. 4

https://iopscience.iop.org/article/10.1088/1748-9326/ab0399/meta

Abstract
After decades of decline, croplands are once again expanding across the United States. A recent spatially explicit analysis mapped nearly three million hectares of US cropland expansion that occurred between 2008 and 2012. Land use change (LUC) of this sort can be a major source of anthropogenic carbon (C) emissions, though the effects of this change have yet to be analyzed. We developed a data-driven model that combines these high-resolution maps of cropland expansion with published maps of biomass and soil organic carbon stocks (SOC) to map and quantify the resulting C emissions. Our model increases emphasis on non-forest—i.e. grassland, shrubland and wetland—above and belowground biomass C stocks and the response of SOC to LUC—emission sources that are frequently neglected in traditional C accounting. These sources represent major emission conduits in the US, where new croplands primarily replace grasslands. We find that expansion between 2008–12 caused, on average, a release of 55.0 MgC ha−1 (SDspatial = 39.9 MgC ha−1), which resulted in total emissions of 38.8 TgC yr−1 (95% CI = 21.6–55.8 TgC yr−1). We also find wide geographic variation in both the size and sensitivity of affected C stocks. Grassland conversion was the primary source of emissions, with more than 90% of these emissions originating from SOC stocks. Due to the long accumulation time of SOC, its dominance as a source suggests that emissions may be difficult to mitigate over human-relevant time scales. While methodological limitations regarding the effects of land use legacies and future management remain, our findings emphasize the importance of avoiding LUC emissions and suggest potential means by which natural C stocks can be conserved.

[AbruptSLR]

The linked reference indicates that current positive soil moisture feedbacks near 1.5C can strongly impact land use changes, LUC, carbon emission that were not considered in the assessments from the Paris Agreement.  This indicates that many of the low emission scenarios assessed under the Paris Agreement are not as safe as assumed by consensus climate science.

Sonia I. Seneviratne et al. (2018), "Climate extremes, land–climate feedbacks and land-use forcing at 1.5°C", Philosophical Transactions of the Royal Society A, https://doi.org/10.1098/rsta.2016.0450

https://royalsocietypublishing.org/doi/full/10.1098/rsta.2016.0450

Abstract: "This article investigates projected changes in temperature and water cycle extremes at 1.5°C of global warming, and highlights the role of land processes and land-use changes (LUCs) for these projections. We provide new comparisons of changes in climate at 1.5°C versus 2°C based on empirical sampling analyses of transient simulations versus simulations from the ‘Half a degree Additional warming, Prognosis and Projected Impacts’ (HAPPI) multi-model experiment. The two approaches yield similar overall results regarding changes in climate extremes on land, and reveal a substantial difference in the occurrence of regional extremes at 1.5°C versus 2°C. Land processes mediated through soil moisture feedbacks and land-use forcing play a major role for projected changes in extremes at 1.5°C in most mid-latitude regions, including densely populated areas in North America, Europe and Asia. This has important implications for low-emissions scenarios derived from integrated assessment models (IAMs), which include major LUCs in ambitious mitigation pathways (e.g. associated with increased bioenergy use), but are also shown to differ in the simulated LUC patterns. Biogeophysical effects from LUCs are not considered in the development of IAM scenarios, but play an important role for projected regional changes in climate extremes, and are thus of high relevance for sustainable development pathways.
This article is part of the theme issue ‘The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'."

Extract: "We further highlight that the regional amplification of hot extremes identified in many land regions with transitional conditions between dry and wet climates can be related to soil moisture feedbacks. As a consequence, any regional biogeophysical modifications of land processes, e.g. through land-use changes affecting land-cover type or land management—and thereby albedo or moisture fluxes—are found to strongly affect these regional changes in climate extremes, especially for low-emissions scenarios. This result is critical for the development of future climate projections and IAM scenarios, since biogeophysical feedbacks of simulated changes in land use are not considered in the development of IAM models and could modify the identified optimal mitigation pathways, in particular for low-emissions scenarios."

[AbruptSLR]

As a follow-on to my last post, the linked reference confirms that the low emissions scenarios evaluated under the Paris Agreement are not as safe as previously assumed by consensus climate science.  This supports concerns that a domino-effect cascade of positive feedback mechanisms could occur when GMSTA is between 1.5 and 2C:

Felipe Feijoo et al. (2019), "Climate and carbon budget implications of linked future changes in CO2 and non-CO2 forcing", Environmental Research Letters, Vol 14, No. 4

https://iopscience.iop.org/article/10.1088/1748-9326/ab08a9/meta

Abstract
The approximate proportional relationship between cumulative carbon emissions and instantaneous global temperature rise (the carbon budget approximation) has proven to be a useful concept to translate policy-relevant temperature objectives into CO2 emissions pathways. However, when non-CO2 forcing is changing along with CO2 forcing, errors in the approximation increases. Using the GCAM model to produce an ensemble of ~3000 scenarios, we show that linked changes in CO2 forcing, aerosol forcing, and non-CO2 greenhouse gas (GHG) forcing lead to an increase in total non-CO2 forcing over the 21st century across mitigation scenarios. This increase causes the relationship between instantaneous temperature and cumulative CO2 emissions to become more complex than the proportional approximation often assumed, particularly for low temperature objectives such as 1.5 °C. The same linked changes in emissions also contribute to a near-term increase in aerosol forcing that effectively places a limit on how low peak temperature could be constrained through GHG mitigation alone. In particular, we find that 23% of scenarios that include CCS (but only 1% of scenarios that do not include CCS) achieve a temperature objective of 1.5 °C without temperature overshoot.

[AbruptSLR]

Since we all know how 2018 ended (emissions wise),
…

For those who do not know how 2018 ended (emissions wise), I provide the attached image indicating that CO2 emissions were very close to those in the RCP 8.5 scenario.

[AbruptSLR]

The first linked reference (Willeit et al 2019) and the associated Real Climate article, provides an example of how consensus science findings can inappropriately serve to encourage decision makers to continue on with BAU behavior (for at least several more years) for reasons including:

1. The research indicates that an ECS value of 3C is characteristic for the past 3 million year paleo record; without stating that ECS during glacial periods is nonlinearly lower than during interglacial periods (see Li Lo et al. 2017 and the first attached image).  Thus as we are in an interglacial period Willeit et al 2019 finding indicate that ECS is currently nonlinearly higher than 3C as supported by initial finding from CMIP6 projections.

2. The Willeit et al 2019 findings are the first time that models have been able to match the past 3 million year paleo record; which indicates that earlier guidance was non-conservative as the new findings show a strong sensitivity of the cryosphere to atmospheric CO₂ concentrations.  Furthermore, Willeit et al. 2019 do not use a dynamic model for the WAIS, and thus their findings would average out any multi-decadal change in the planetary energy imbalance noted by Hansen et al (2016).

Finally, I note that the second attached image from the Real Climate article shows that for the last 3 million years GMSTA has not been above 2C thus, if we collectively exceed the 2C value we may well be subject to abrupt climate change surprises as cautioned by the NAS in 2013.

M. Willeit et al. (03 Apr 2019), "Mid-Pleistocene transition in glacial cycles explained by declining CO2 and regolith removal", Science Advances, Vol. 5, no. 4, eaav7337, DOI: 10.1126/sciadv.aav7337

http://advances.sciencemag.org/content/5/4/eaav7337

Abstract
Variations in Earth’s orbit pace the glacial-interglacial cycles of the Quaternary, but the mechanisms that transform regional and seasonal variations in solar insolation into glacial-interglacial cycles are still elusive. Here, we present transient simulations of coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. We show that a gradual lowering of atmospheric CO2 and regolith removal are essential to reproduce the evolution of climate variability over the Quaternary. The long-term CO2 decrease leads to the initiation of Northern Hemisphere glaciation and an increase in the amplitude of glacial-interglacial variations, while the combined effect of CO2 decline and regolith removal controls the timing of the transition from a 41,000- to 100,000-year world. Our results suggest that the current CO2 concentration is unprecedented over the past 3 million years and that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary.

See also:

Title: "First successful model simulation of the past 3 million years of climate change"

http://www.realclimate.org/index.php/archives/2019/04/first-successful-model-simulation-of-the-past-3-million-years-of-climate-change/#more-22376

Extract: "The simulations further suggest that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary. Ice sheet evolution is very sensitive to temperature, and the initiation of NH glaciation at around 3 million years ago would not have been possible in the model if global temperature would have been higher than 2°C relative to preindustrial during the early Quaternary."
&

Li Lo et al (2017), Nonlinear climatic sensitivity to greenhouse gases over past 4 glacial/interglacial cycles", Scientific Reports 7, No. 4626, DOI: https://doi.org/10.1038/s41598-017-04031-x

https://www.nature.com/articles/s41598-017-04031-x

Abstract: "The paleoclimatic sensitivity to atmospheric greenhouse gases (GHGs) has recently been suggested to be nonlinear, however a GHG threshold value associated with deglaciation remains uncertain. Here, we combine a new sea surface temperature record spanning the last 360,000 years from the southern Western Pacific Warm Pool with records from five previous studies in the equatorial Pacific to document the nonlinear relationship between climatic sensitivity and GHG levels over the past four glacial/interglacial cycles. The sensitivity of the responses to GHG concentrations rises dramatically by a factor of 2–4 at atmospheric CO2 levels of >220 ppm. Our results suggest that the equatorial Pacific acts as a nonlinear amplifier that allows global climate to transition from deglacial to full interglacial conditions once atmospheric CO2 levels reach threshold levels."

[sidd]

Re: "Willeit et al. 2019 do not use a dynamic model for the WAIS"

yes ...

Re: " and thus their findings would average out any multi-decadal change in the planetary energy imbalance noted by Hansen et al (2016)."

How so ? Where does Hansen state this ?

sidd

[Sleepy]

I haven't followed but maybe one of the two papers attached below?

Just popped in to post this nice(?) podcast with Glen Peters (one of the lead authors in WG6-AR3-Ch3):
https://kleinmanenergy.upenn.edu/energy-policy-now/hard-look-negative-emissions

[Sciguy]

Since we all know how 2018 ended (emissions wise),
…

For those who do not know how 2018 ended (emissions wise), I provide the attached image indicating that CO2 emissions were very close to those in the RCP 8.5 scenario.

There's actually some good news in that graph.  We were above the RCP 8.5 line a few years ago and are now below it, even with the increase in emissions in 2018. So we're already on a better emissions path than 8.5 and current economic conditions can allow us to get below the RCP 4.5 emissions track before 2030.

With renewables now cheaper than coal and almost at parity with natural gas, we can expect emissions to plateau over the next few years and begin to decrease rapidly after the mid-2020s.

Also, electric vehicles (EVs) are approaching cost parity with internal combustion engine (ICE) vehicles and with the decrease in battery costs, EVs will soon be cheaper than ICEs.  It's not a big reach to think that by the 2030s no new ICE vehicles will be manufactured.

An emissions pathway between RCP 2.6 and 4.5 is achievable with current technology.

[AbruptSLR]

Re: "Willeit et al. 2019 do not use a dynamic model for the WAIS"

yes ...

Re: " and thus their findings would average out any multi-decadal change in the planetary energy imbalance noted by Hansen et al (2016)."

How so ? Where does Hansen state this ?

sidd

Typically freshwater hosing events in the North Atlantic have a longer lasting impact on the MOC than do freshwater hosing events in the Southern Ocean, because the freshwater is more contained in the North Atlantic; while it is more quickly dispersed around the Southern Ocean.  This can be seen in the attached image of the multidecadal impact of freshwater hosing events in the NH and SH on planetary energy imbalance from Hansen et al (2016).

[sidd]

So how does freshwater hosing "average out any multi-decadal change in the planetary energy imbalance " ?

If you have a static antarctica, then there is no freshwater hosing in the south. So how does confining hosing to the north average out any multi-decadal change in the planetary energy imbalance ?

sidd

[Sleepy]

Mornin', maybe I still don't follow but a static Antarctica would lower the planet's energy imbalance.

[sidd]

Re:  a static Antarctica would lower the planet's energy imbalance.

How so ?

if you mean the albedo effect, a static antarctica would have static albedo, while a dynamic one would have albedo effect waxing and waning with ice sheet advance and retreat. But i do not see how that changes energy imbalance. You got to get the static antarctica albedo "correct" in the sense if you make the static antarctic ice sheet too big or too small, your model for the last 3 million years will be wildly wrong. Which it isnt, in fact it even gets the mid pleistocene transition right.

so that tells me that the large scale features of the glacial interglacial cycles can be captured with just the northern ice sheet + ocean + land model while leaving antarctica constant. That is a surprising result, since antarctica is such a strong control on southern ocean, but that also seems to say it didnt do anything too weird in the last 3 million years. Yet we know that the typical glacial to interglacial transition has antarctic ice sheet going out to continental shelf edge, and retreating back into WAIS deglaciation on occasion in interglacials. But that isn't necessary to put in the model to get the macro oscillations and most of detail correct. Amazing. I thought you would need to put Antarctica in.

But it is only one model, of course. I'm sure more such models which can explain the last 3 megayear will show up.


sidd

[Sleepy]

Hansen is talking about the effect of ice sheet disintegration and freshwater hosing, which provides the obvious negative feedback and cooling but at the same time increases the planet's energy imbalance. See (b) in the image ASLR posted above, it's in section 3.4 of that paper.

Edit; might as well add the link: https://www.atmos-chem-phys.net/16/3761/2016/

[AbruptSLR]

The linked 2018 study by Niels Jungbluth and Christoph Meil, entitled: "Aviation and Climate Change: Best practice for calculation of the global warming potential", uses radiative-forcing-index (RFI) factors to indicate that CO₂ emissions from aircraft directly into the upper atmosphere have higher global warming potential that CO₂ emitted at ground level.  As air transport is increasing at a more rapid rate than global population, this is a significant challenge for limiting global warming that is underestimated by consensus climate science:

http://esu-services.ch/fileadmin/download/jungbluth-2018-RFI-best-practice.pdf

Abstract
Aircrafts have a contribution to global warming that is higher than their CO2-emissions alone. The gap between science on the one side and the missing of applicable GWP (global-warming potential) factors for relevant emissions on the other is a shortcoming for carbon footprint (CF) calculations. Here we present the state-of-the-art for accounting. Approaches are ranging from RFI (radiative-forcing-index) factors of 1 to 2.7 that can be multiplied with the direct CO2 emissions in order to calculate the total global warming potential of aviation services.  An RFI of 2 on total aircraft CO2 (or 5.2 for the CO2 in higher atmosphere) is identified as best practice because it is based on the correct interpretation of the most recent scientific publications. This factor can be multiplied with the CO2 emissions in the higher atmosphere for calculating the GWP of transport services provided by aircrafts.

[AbruptSLR]

So how does freshwater hosing "average out any multi-decadal change in the planetary energy imbalance " ?

If you have a static antarctica, then there is no freshwater hosing in the south. So how does confining hosing to the north average out any multi-decadal change in the planetary energy imbalance ?

sidd

Willeit et al 2019 compare their model output to the paleo-record.  The paleo-record definitely includes multi-decadal changes in planetary energy from abrupt ice mass loss from Antarctica (as demonstrated by Hansen et al 2016); however, Willeit et al 2019 does not; yet they claim an excellent match with the paleo-record.  To resolve this matter, I propose that the paleo-record that Willeit et al 2019 are looking at does not have sufficiently high resolution to observe the relatively quick pulse in planetary energy imbalance due to a dynamic WAIS, but that the paleo-record does have a sufficiently high resolution to observe the longer pulse in planetary energy imbalance from a freshwater hosing event in the North Atlantic.  Willeit et al. 2019 then incorrectly ignores the contribution from WAIS hosing events while over emphasizing the contribution from North Atlantic hosing events.

[AbruptSLR]

The linked reference addresses changes in land surface albedo from 1700 to the early 2000's and finds that over this period that changes in radiative forcing associated with land surface albedo significantly offset radiative forcing associated with carbon emissions, over this period.  For me this raises the risk that land cover changes (LCC) since 1700 may have masked relatively high values of ECS. Furthermore, the attached image of Table 4 from that He et al. (2018) indicates a high degree of uncertainty about what the true value of LCC has been over this period.
Thus this represents a risk that current carbon budgets bases on consensus climate models may be too large, as radiative forcing from carbon emissions may increase much more rapidly than can be offset by future changes in LCC.

T. He et al. (2018), "5.06 - Land Surface Albedo", Reference Module in Earth Systems and Environmental Sciences, Comprehensive Remote Sensing, Volume 5, Pages 140-162, https://doi.org/10.1016/B978-0-12-409548-9.10370-7

https://www.sciencedirect.com/science/article/pii/B9780124095489103707

Abstract: Land surface albedo is one of the key controlling geophysical parameters in the energy budget studies, and its temporal and spatial variation is closely related to the global climate change and regional weather and environment. This article provides a comprehensive review for algorithms used for deriving surface broadband albedo with various geostationary and polar-orbiting satellite data in recent decades and brief introductions on some widely used satellite albedo products, followed by analyses of global albedo climatologies, long-term trends in surface albedo, and reviews of surface albedo-induced radiative effects and albedo-based geoengineering efforts."
&

Extract: "Generally, the radiative forcings due to changes in surface albedo are thought to be able to compromise that from carbon emissions since the 1700s (Bala et al., 2007; Lyons et al., 2008; Randerson et al., 2006). However, uncertainties reported in recent IPCC Assessment Reports and journal publications are quite large in the surface albedo radiative forcing estimates since 1750 (Table 4)."

[AbruptSLR]

While many people ignore the influence of the rate of radiative forcing on the safe remaining carbon budget; the following are selected reasons why higher rates of anthropogenic radiative forcing decrease the amount of safe remaining carbon budget:

1. Earth's natural living systems need time to adapt to climate change, so the faster the rate of change the further extant biological systems will remain.  Let alone the fact that mankind is dependent on many of these natural biological systems; many of these land-based and oceanic biological systems act as carbon sinks and those that cannot adapt fast enough will result in a reduction of the associated carbon sinks.

2. The risk of cascading positive feedback mechanism increases with faster rates of climate forcing, both due to thermal momentum and due to fact that the peaks of many positive feedback systems are transient (e.g. methane emissions from thermokarst lakes), so if they are given time to dissipate they will not be present to tip an interconnected feedback mechanism, and vice versa.

3. Faster rates of radiative forcing can temporarily increase weather variability, and as weather variability is directly related to climate sensitivity, temporarily greater weather variability creates temporarily higher values of climate sensitivity.

4. Many ice-climate feedback mechanisms are transient due to the limited supply of the driving ice (freshwater) source.  Thus faster rates of radiative forcing will cause such transient positive ice-climate feedback mechanisms to overlap with other activated feedbacks (e.g. carbon emissions from projected land use changes).

5. Many negative feedback mechanisms (e.g. indirect aerosol feedbacks) dissipate much more quickly than to related positive feedback mechanisms (e.g. permafrost degradation).  Thus using up the carbon budget limit following a BAU pathway will result in a more abrupt increase in climate change, if society then responds to the carbon budget limit and severely limits negative feedbacks such as indirect aerosols mechanisms.

[AbruptSLR]

The linked reference confirms that: "Climate change is an issue which elicits low engagement, even among concerned segments of the public."  Furthermore, it indicates the current communication of consensus science is insufficient to significantly motivate public engagement in Climate Action.  This low public engagement implies that pathways with higher radiative forcing are more likely to be followed than those with lower radiative forcing:

Morris, B.S., Chrysochou, P., Christensen, J.D. et al. (2019), "Stories vs. facts: triggering emotion and action-taking on climate change", Climatic Change, pp 1–18, https://doi.org/10.1007/s10584-019-02425-6

https://rd.springer.com/article/10.1007%2Fs10584-019-02425-6

Abstract: "Climate change is an issue which elicits low engagement, even among concerned segments of the public. While research suggests that the presentation of factual information (e.g., scientific consensus) can be persuasive to some audiences, there is also empirical evidence indicating that it may also increase resistance in others. In this research, we investigate whether climate change narratives structured as stories are better than informational narratives at promoting pro-environmental behavior in diverse audiences. We propose that narratives structured as stories facilitate experiential processing, heightening affective engagement and emotional arousal, which serve as an impetus for action-taking. Across three studies, we manipulate the structure of climate change communications to investigate how this influences narrative transportation, measures of autonomic reactivity indicative of emotional arousal, and pro-environmental behavior. We find that stories are more effective than informational narratives at promoting pro-environmental behavior (studies 1 and 3) and self-reported narrative transportation (study 2), particularly those with negatively valenced endings (study 3). The results of study 3 indicate that embedding information in story structure influences cardiac activity, and subsequently, pro-environmental behavior. These findings connect works from the fields of psychology, neuroscience, narratology, and climate change communication, advancing our understanding of how narrative structure influences engagement with climate change through emotional arousal, which likely incites pro-environmental behavior as the brain’s way of optimizing bodily budgets."

[AbruptSLR]

I note that USGCRP (2017) Chapter 15: Potential Surprises provides the following supporting evidence for their medium confidence assertion that consensus climate models underestimate paleo reconstructions of climate sensitivity

Extract: "The second half of this key finding is based upon the tendency of global climate models to underestimate, relative to geological reconstructions, the magnitude of both long-term global mean warming and the amplification of warming at high latitudes in past warm climates (e.g., Salzmann et al. 2013; Goldner et al. 2014; Caballeo and Huber 2013; Lunt et al. 2012)."

Note USGCRP (2017) classifies Medium Confidence as: "Suggestive evidence (a few sources, limited consistency, models incomplete, methods emerging, etc.), competing schools of thought"

Furthermore, the guide to USGCRP (2017) classifies these "Potential Surprises" as 'potential low probability/high consequence "surprises" resulting from climate change' and as 'high-risk tails and bounding scenarios'; and acknowledge that 'knowledge gaps' exist that limit their ability to precisely define the probability/risks associated with these "surprises".

https://science2017.globalchange.gov/chapter/front-matter-guide/

Extract: "Complementing this use of risk-focused language and presentation around specific scientific findings in the report, Chapter 15: Potential Surprises provides an overview of potential low probability/high consequence “surprises” resulting from climate change. This includes its analyses of thresholds, also called tipping points, in the climate system and the compounding effects of multiple, interacting climate change impacts whose consequences may be much greater than the sum of the individual impacts. Chapter 15 also highlights critical knowledge gaps that determine the degree to which such high-risk tails and bounding scenarios can be precisely defined, including missing processes and feedbacks."

[AbruptSLR]

I provide the following link about pre-2017 research on the rate of subsea permafrost degradation, and associated methane emissions, in the ESAS.  This research identifies numerous mechanisms that could accelerate methane emissions from the ESAS faster than assumed in AR5:

Natalia Shakhova, et al (2017), "Current rates and mechanisms of subsea permafrost degradation in the East Siberian Arctic Shelf", Nature Communications 8, Article number: 15872,
doi:10.1038/ncomms15872

http://www.nature.com/articles/ncomms15872

Abstract: "The rates of subsea permafrost degradation and occurrence of gas-migration pathways are key factors controlling the East Siberian Arctic Shelf (ESAS) methane (CH4) emissions, yet these factors still require assessment. It is thought that after inundation, permafrost-degradation rates would decrease over time and submerged thaw-lake taliks would freeze; therefore, no CH4 release would occur for millennia. Here we present results of the first comprehensive scientific re-drilling to show that subsea permafrost in the near-shore zone of the ESAS has a downward movement of the ice-bonded permafrost table of ∼14 cm year−1 over the past 31–32 years. Our data reveal polygonal thermokarst patterns on the seafloor and gas-migration associated with submerged taliks, ice scouring and pockmarks. Knowing the rate and mechanisms of subsea permafrost degradation is a prerequisite to meaningful predictions of near-future CH4 release in the Arctic."

See also:

http://envisionation.co.uk/index.php/nick-breeze/203-subsea-permafrost-on-east-siberian-arctic-shelf-now-in-accelerated-decline

[AbruptSLR]

In contrast to some earlier (overly simplified) consensus research, the linked reference finds that "… interactions between convective aggregation and the spatial distribution of SST appear …" to increase ECS.  As ice-climate feedbacks tend to increase SST gradients; Coppin & Bony (2018)'s finding indicate that ice-climate feedbacks will increase ECS.

David Coppin and Sandrine Bony (28 November 2018), "On the Interplay Between Convective Aggregation, Surface Temperature Gradients, and Climate Sensitivity", JAMES, https://doi.org/10.1029/2018MS001406

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018MS001406

Abstract: "This study explores the extent to which convective aggregation interacts with sea surface temperature (SST) and affects climate sensitivity. For this purpose, radiative‐convective equilibrium simulations are run with a general circulation model coupled to an ocean mixed layer, and several types of perturbations are imposed to the ocean‐atmosphere system. Convective aggregation turns out to be much more sensitive to temperature in coupled experiments than in prescribed SST experiments. But changes in convective aggregation induced by a doubling of the CO2 concentration are always smaller than changes associated with the transition from a non‐aggregated to an aggregated state. If aggregation changes were acting alone, they would exert a strong negative feedback on global mean surface temperature. However, in a coupled framework, aggregation changes interact with the SST and generate SST gradients that strengthen the positive low‐cloud feedback associated with changes in SST pattern. This overcompensates the negative feedback due to aggregation changes and leads to a larger equilibrium climate sensitivity than in the absence of SST gradients. Although this effect might be model specific, interactions between convective aggregation and the spatial distribution of SST appear crucial to assess the impact of convective aggregation on climate sensitivity."

See also:

Cook, T. (2019), Improving estimates of long-term climate sensitivity, Eos, 100, https://doi.org/10.1029/2019EO116981. Published on 05 March 2019.

https://eos.org/research-spotlights/improving-estimates-of-long-term-climate-sensitivity

Extract: "In contrast to earlier studies, which found that aggregation decreases climate sensitivity when coupled with a simplified ocean, the team instead found that aggregation can increase it. Because these results indicate that aggregation strongly interacts with sea surface temperature gradients, this study casts significant doubt on the appropriateness of using experiments with fixed and uniform sea surface temperatures to understand the effects of convective aggregation on climate sensitivity."

[AbruptSLR]

In contrast to overly-simplified consensus climate models, improved modeling of root dynamics in the more advanced E3SM; finds that climate change driven root dynamics will result in a net loss in plant induced carbon sequestration in the soil; which of course implies higher values of ECS than assumed by earlier consensus climate models:

B. A. Drewniak (03 January 2019), "Simulating Dynamic Roots in the Energy Exascale Earth System Land Model", JAMES,

https://doi.org/10.1029/2018MS001334

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018MS001334

Abstract: "Roots are important contributors to plant development, functioning to provide nutrients and water for plant growth. However, roots and their functions are often simplified in Earth system models, which limit the feedback of root foraging strategy on plant productivity, and their impacts on the carbon cycle. The goal of this study is to introduce a new method to resolve the vertical structure of roots over time. The method allows plasticity of rooting depth distribution under nonuniform profiles of water and nitrogen, which influences aboveground dynamics. The dynamic root model optimizes root distribution for both water and nitrogen uptake but gives priority to plant water demands. I implement this new method in the Energy Exascale Earth System model. The resulting root distribution maintains agreement with observations in most ecosystems and marginally improves the gross primary productivity estimated by the model, compared to satellite observations. Increases in gross primary productivity are simulated in desert and boreal ecosystems. However, the model does not capture deep roots in the dry tropics, and therefore, productivity losses are observed in parts of the Amazon and the African savannah. I discuss details of the model algorithm, along with some sensitivity studies that shed light on the model behavior in water‐limited ecosystems. The study shows that additional model processes, such as climate dependent root depth, root hydraulics, root form and function, and better nitrogen uptake, should be considered to improve the root water uptake in the Energy Exascale Earth System Land Model (ELM)."
&

Extract: "Globally, the net effect is a loss of productivity and carbon storage."

[AbruptSLR]

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."

[AbruptSLR]

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."

[AbruptSLR]

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.""

[AbruptSLR]

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

[AbruptSLR]

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.

[AbruptSLR]

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.

[AbruptSLR]

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.

[AbruptSLR]

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.

[AbruptSLR]

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."

[AbruptSLR]

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

[vox_mundi]

Glaciers Crumble and Sea Levels Rise In This New Weather Channel Immersive Mixed Reality Clip 
https://www.theverge.com/2019/4/9/18302006/sea-level-rise-charleston-norfolk-glaciers-climate-change-the-weather-channel



The scene is from The Weather Channel’s latest mixed reality segment, which connects the flooding of tomorrow to the melting glaciers and sea level rise of today.

[AbruptSLR]

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."

[AbruptSLR]

…
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.

[AbruptSLR]

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.