Support the Arctic Sea Ice Forum and Blog

Author Topic: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE  (Read 464906 times)

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2450 on: December 28, 2019, 07:21:23 AM »
The linked reference examines the case where freshwater hosing effectively shuts-down the AMOC (as in Hansen's ice-climate feedback mechanism); and finds that the ENSO moves to towards the Eastern Pacific; which I note is typically an indication of increased effective ECS:

Mark S. Williamson, Mat Collins, Sybren S. Drijfhout, Ron Kahana, Jennifer V. Mecking and Timothy M. Lenton (2017), "Effect of AMOC collapse on ENSO in a high resolution general circulation model", Climate Dynamics, DOI: 10.1007/s00382-017-3756-0

https://link.springer.com/article/10.1007/s00382-017-3756-0

Abstract: "We look at changes in the El Niño Southern Oscillation (ENSO) in a high-resolution eddy-permitting climate model experiment in which the Atlantic Meridional Circulation (AMOC) is switched off using freshwater hosing. The ENSO mode is shifted eastward and its period becomes longer and more regular when the AMOC is off. The eastward shift can be attributed to an anomalous eastern Ekman transport in the mean equatorial Pacific ocean state. Convergence of this transport deepens the thermocline in the eastern tropical Pacific and increases the temperature anomaly relaxation time, causing increased ENSO period. The anomalous Ekman transport is caused by a surface northerly wind anomaly in response to the meridional sea surface temperature dipole that results from switching the AMOC off. In contrast to a previous study with an earlier version of the model, which showed an increase in ENSO amplitude in an AMOC off experiment, here the amplitude remains the same as in the AMOC on control state. We attribute this difference to variations in the response of decreased stochastic forcing in the different models, which competes with the reduced damping of temperature anomalies. In the new high-resolution model, these effects approximately cancel resulting in no change in amplitude."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2451 on: December 28, 2019, 05:31:30 PM »
The linked article discusses the 'jellyfication' of the world's oceans, not only from climate change, but also from other human activities:

Title: "Jellyfish thrive in the man-made disruption of the oceans"

https://phys.org/news/2019-09-jellyfish-man-made-disruption-oceans.html

Extract: "Jellyfish have been on Earth longer than we have—they are believed to have roamed the oceans for nearly 600 million years.

But human activity, from over-fishing to plastic waste and climate change, has created an environment in which they are even more at home.

The proliferation of the jellyfish could lead to what some observers are calling the "jellyfication" of the oceans, which are facing profound changes according to a draft UN report due out on Wednesday."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2452 on: December 28, 2019, 05:34:27 PM »
The linked reference indicates that reduced plant nitrogen (N) and phosphorous (P) concentrations observed in plants subjected to accelerated growth associated with climate warming of a permafrost region in Tibet, means that those who were hoping that carbon emissions associated with permafrost degradation would be mitigated by increased carbon absorption due to accelerated plant growth are out of luck:

Fei Li, Yunfeng Peng, Susan M. Natali, Kelong Chen, Tianfeng Han, Guibiao Yang, Jinzhi Ding, Dianye Zhang, Guanqin Wang, Jun Wang, Jianchun Yu, Futing Liu & Yuanhe Yang (2 August 2017), "Warming effects on permafrost ecosystem carbon fluxes associated with plant nutrients", Ecology Ecological Society of America, DOI: 10.1002/ecy.1975

http://onlinelibrary.wiley.com/doi/10.1002/ecy.1975/abstract?utm_content=buffer9ccd4&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Large uncertainties exist in carbon (C)-climate feedback in permafrost regions, partly due to an insufficient understanding of warming effects on nutrient availabilities and their subsequent impacts on vegetation C sequestration. Although a warming climate may promote a substantial release of soil C to the atmosphere, a warming-induced increase in soil nutrient availability may enhance plant productivity, thus offsetting C loss from microbial respiration. Here, we present evidence that the positive temperature effect on carbon dioxide (CO2) fluxes may be weakened by reduced plant nitrogen (N) and phosphorous (P) concentrations in a Tibetan permafrost ecosystem. Although experimental warming initially enhanced ecosystem CO2 uptake, the increased rate disappeared after the period of peak plant growth during the early growing season, even though soil moisture was not a limiting factor in this swamp meadow ecosystem. We observed that warming did not significantly affect soil extractable N or P during the period of peak growth, but decreased both N and P concentrations in the leaves of dominant plant species, likely caused by accelerated plant senescence in the warmed plots. The attenuated warming effect on CO2 assimilation during the late growing season was associated with lowered leaf N and P concentrations. These findings suggest that warming-mediated nutrient changes may not always benefit ecosystem C uptake in permafrost regions, making our ability to predict the C balance in these warming-sensitive ecosystems more challenging than previously thought."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2453 on: December 28, 2019, 05:35:26 PM »
The linked reference indicates that Sudden Stratospheric Warming, SSW, events will likely become much more frequent in the Arctic with continued global warming.  If so, this would constitute another positive feedback mechanism for Arctic Amplification not adequately characterized by CMIP5/AR5:

Wanying Kang & Eli Tziperman (2017), "More frequent Sudden Stratospheric Warming events due to enhanced MJO forcing expected in a warmer climate", Journal of Climate, https://doi.org/10.1175/JCLI-D-17-0044.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0044.1?utm_content=buffer81f8c&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Sudden Stratospheric Warming (SSW) events influence the Arctic Oscillation and mid-latitude extreme weather. Observations show SSW events to be correlated with certain phases of Madden-Julian Oscillation (MJO), but the effect of the MJO on SSW frequency is unknown, and the teleconnection mechanism, its planetary wave propagation path and time scale are still not completely understood. We study the Arctic stratosphere response to increased MJO forcing expected in a warmer climate using two models: the comprehensive Whole Atmosphere Community Climate Model and an idealized dry dynamical core with and without MJO-like forcing. We show that the frequency of SSW events increases significantly in response to stronger MJO forcing, also affecting the averaged polar cap temperature. Two teleconnection mechanisms are identified: a direct propagation of MJO-forced transient waves to the Arctic stratosphere, and a nonlinear enhancement of stationary waves by the MJO-forced transient waves. The MJO-forced waves propagate poleward in the lower stratosphere and upper troposphere, and then upward. The cleaner results of the idealized model allow identifying the propagating signal and suggest a horizontal propagation time scale of 10-20 days, followed by additional time for upward propagation within the Arctic stratosphere, although there are significant uncertainties involved. Given that the MJO is predicted to be stronger in a warmer climate, these results suggest that SSW events may become more frequent, with possible implications on tropospheric high latitude weather. However, the effect of an actual warming scenario on SSW frequency involves additional effects besides a strengthening of the MJO, requiring further investigation."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2454 on: December 28, 2019, 05:36:31 PM »
Field observations indicate that the impact of light absorbing particles (LAPs) on snow albedo in the Arctic, North America and China is contributing more to global warming than previously assumed:

Cheng Dang, Stephen G. Warren, Qiang Fu, Sarah J. Doherty & Matthew Sturm (5 August 2017), "Measurements of light-absorbing particles in snow across the Arctic, North America, and China: effects on surface albedo", Journal of Geophysical Research Atmospheres, DOI: 10.1002/2017JD027070 

http://onlinelibrary.wiley.com/doi/10.1002/2017JD027070/abstract?utm_content=buffer427b2&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Using field observation, we perform radiative transfer calculations on snowpacks in the Arctic, China, and North America to quantify the impact of light-absorbing particles (LAPs) on snow albedo and its sensitivity to different factors. For new snow, the regional-averaged albedo reductions caused by all LAPs in the Arctic, North America, and China are 0.009, 0.012, and 0.077, respectively, of which the albedo reductions caused by black carbon (BC) alone are 0.005, 0.005, and 0.031, corresponding to a positive radiative forcing of 0.06, 0.3, and 3 Wm-2. The albedo reduction for old melting snow is larger than that of new snow by a factor of 2, for the same particulate concentrations; this leads to 3 – 8 times larger radiative forcing, in part due to higher solar irradiance in the melting season. These calculations used ambient snowpack properties; if all snowpacks were instead assumed to be optically thick, the albedo reduction would be 20-50% larger for new snow in the Arctic and North America and 120-300% larger for old snow. Accounting for non-BC LAPs reduces the albedo reduction by BC in the Arctic, North America, and China by 32%, 29% and 70% respectively for new snow and 11%, 7% and 51% for old snow. BC-in-snow albedo reduction computed using two-layer model agrees reasonably with that computed using multi-layer model. Biases in BC concentration or snow depth often lead to nonlinear biases in BC-induced albedo reduction."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2455 on: December 28, 2019, 05:38:04 PM »
The linked reference uses model projections to demonstrate that relatively large and rapid obduction (re-emergence) of anthropogenic carbon into the well-mixed surface layer in the ocean will contribute to limiting of future ocean uptake of carbon from the atmosphere:

Katsuya Toyama et. al. (2017), "Large Re-emergence of Anthropogenic Carbon Into the Ocean’s Surface Mixed Layer Sustained by the Ocean’s Overturning Circulation", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0725.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0725.1?utm_content=buffer00f0c&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "We evaluate the output from a widely used ocean carbon cycle model to identify the subduction and obduction (re-emergence) rates of anthropogenic carbon (Cant) for climatological conditions during the World Ocean Circulation Experiment (WOCE) era in 1995 using a new set of Lagrangian diagnostic tools. The principal scientific value of the Lagrangian diagnostics is in providing a new means to connect Cant re-emergence pathways to the relatively rapid renewal timescales of mode waters through the overturning circulation.

Our main finding is that for this model with 2.04 PgC/yr of uptake of Cant via gas exchange, the subduction and obduction rates across the base of the mixed layer (MLbase) are 4.96 PgC/yr and 4.50 PgC/yr, respectively, which are twice as large as the gas exchange at the surface. Given that there is net accumulation of 0.17 PgC/yr in the mixed layer itself, this implies the residual downward Cant transport of 1.40 PgC/yr across the MLbase is associated with diffusion. Importantly, the net patterns for subduction and obduction transports of Cant mirror the large-scale patterns for transport of water volume, thereby illustrating the processes controlling Cant uptake. Although the net transfer across the MLbase by compensating subduction and obduction is relatively smaller than the diffusion, localized pattern of Cant subduction and obduction implies significant regional impacts. The median timescale for re-emergence of obducting particles is short (less than 10 years), indicating that re-emergence should contribute to limiting future carbon uptake through its contribution to perturbing the Revelle factor for surface waters."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2456 on: December 28, 2019, 07:21:25 PM »
The data at the linked website shows that Dec 2019 the AIS has had the highest single day rate of surface is melt in the recorded record, and that form Nov 1 to Dec 28 2019, a lot of surface ice melt has occurred in the Amundsen Sea Embayment:

Title: "5-day forecast of the 2019-2020 Antarctica ice sheet SMB simulated by MARv3.10 forced by GFS"

http://climato.be/cms/index.php?climato=the-2020-melt-season-over-antarctica-as-simulated-by-marv3-10


“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

pietkuip

  • Frazil ice
  • Posts: 382
    • View Profile
  • Liked: 127
  • Likes Given: 305
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2457 on: December 29, 2019, 12:56:05 AM »
A good talk about what we don't know by the knowledgeable Julia Slingo, retired Chief Scientist at the UK Met Office. For example about the hydrology of ice shelves. Or about whether oceans and plants will continue to take up as much carbon as they have done up to now. Or about the equilibrium carbon sensitivity.



In the discussion she says that the precautionary principle should be adhered to, rather than eyeballing some kind of average.

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2458 on: December 29, 2019, 05:54:45 AM »
The linked reference indicates that the mid-Pliocene is frequently considered as a rough analogue to climate change this century.  The reported finding come from Pliocene Model Intercomparison Project (PlioMIP), which tends to err on the side of least drama.  Nevertheless, these finding indicate a marked expansion of the Hadley circulation (HC); which typically is an indicator of relatively strong associated positive climate feedback mechanism.

Shawn Corvec and Christopher G. Fletcher (2017), "Changes to the tropical circulation in the mid-Pliocene and their implications for future climate", Clim. Past, 13, 135–147, doi:10.5194/cp-13-135-2017

https://www.clim-past.net/13/135/2017/cp-13-135-2017.pdf

Abstract: "The two components of the tropical overturning circulation, the meridional Hadley circulation (HC) and the zonal Walker circulation (WC), are key to the re-distribution of moisture, heat and mass in the atmosphere. The mid- Pliocene Warm Period (mPWP; ~3.3–3 Ma) is considered a very rough analogue of near-term future climate change, yet changes to the tropical overturning circulations in the mPWP are poorly understood. Here, climate model simulations from the Pliocene Model Intercomparison Project (PlioMIP) are analyzed to show that the tropical overturning circulations in the mPWP were weaker than preindustrial circulations, just as they are projected to be in future climate change. The weakening HC response is consistent with future projections, and its strength is strongly related to the meridional gradient of sea surface warming between the tropical and subtropical oceans. The weakening of the WC is less robust in PlioMIP than in future projections, largely due to inter-model variations in simulated warming of the tropical Indian Ocean (TIO). When the TIO warms faster (slower) than the tropical mean, local upper tropospheric divergence increases (decreases) and the WC weakens less (more). These results provide strong evidence that changes to the tropical overturning circulation in the mPWP and future climate are primarily controlled by zonal (WC) and meridional (HC) gradients in tropical–subtropical sea surface temperatures."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2459 on: December 29, 2019, 05:56:29 AM »
The linked reference indicates that AR5 meaningfully underestimates future global warming from land use and land cover change (LULCC):

Natalie M Mahowald, Daniel Ward, Scott Doney, Peter Hess and James T Randerson (2017), "Are the impacts of land use on warming underestimated in climate policy?", Environmental Research Letters, https://doi.org/10.1088/1748-9326/aa836d

http://iopscience.iop.org/article/10.1088/1748-9326/aa836d
&
http://iopscience.iop.org/article/10.1088/1748-9326/aa836d/pdf

Abstract: "While carbon dioxide emissions from energy use must be the primary target of climate change mitigation efforts, land use and land cover change (LULCC) also represent an important source of climate forcing. In this study we compute time series of global surface temperature change separately for LULCC and non-LULCC sources (primarily fossil fuel burning), and show that because of the extra warming associated with the co-emission of methane and nitrous oxide with LULCC carbon dioxide emissions, and a co-emission of cooling aerosols with non-LULCC emissions of carbon dioxide, the linear relationship between cumulative carbon dioxide emissions and temperature has a two-fold higher slope for LULCC than for non-LULCC activities. Moreover, projections used in the Intergovernmental Panel on Climate Change (IPCC) for the rate of tropical land conversion in the future are relatively low compared to contemporary observations, suggesting that the future projections of land conversion used in the IPCC may underestimate potential impacts of LULCC. By including a "business as usual" future LULCC scenario for tropical deforestation, we find that even if all non-LULCC emissions are switched off in 2015, it is likely that 1.5°C of warming relative to the preindustrial era will occur by 2100. Thus, policies to reduce LULCC emissions must remain a high priority if we are to achieve the low to medium temperature change targets proposed as a part of the Paris Agreement. Future studies using integrated assessment models and other climate simulations should include more realistic deforestation rates and the integration of policy that would reduce LULCC emissions."

Extract: "Here we show that the slope of the cumulative carbon dioxide emissions and
temperature relationship is twice as high for LULCC than for non-LULCC processes
(Figure 2). This implies that carbon dioxide emissions from LULCC is associated
with twice the impact on climate as carbon dioxide emissions from non-LULCC
processes, at least until 2100."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2460 on: December 29, 2019, 06:02:31 AM »
I note that AR5/CMIP5 did not include the freshwater hosing mechanism cited in the linked reference:

Haijun Yang, Qin Wen, Jie Yao & Yuxing Wang (2017), "Bjerknes Compensation in Meridional Heat Transport under Freshwater Forcing and the Role of Climate Feedback", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0824.1

http://journals.ametsoc.org/doi/full/10.1175/JCLI-D-16-0824.1

Abstract: "Using a coupled Earth climate model, freshwater forcing experiments are performed to study the Bjerknes compensation (BJC) between meridional atmosphere heat transport (AHT) and meridional ocean heat transport (OHT). Freshwater hosing in the North Atlantic weakens the Atlantic meridional overturning circulation (AMOC) and thus reduces the northward OHT in the Atlantic significantly, leading to a cooling (warming) in the surface layer in the Northern (Southern) Hemisphere. This results in an enhanced Hadley cell and northward AHT. Meanwhile, the OHT in the Indo-Pacific is increased in response to the Hadley cell change, partially offsetting the reduced OHT in the Atlantic. Two compensations occur here: compensation between the AHT and the Atlantic OHT, and that between the Indo-Pacific OHT and the Atlantic OHT. The AHT change undercompensates the OHT change by about 60% in the extratropics, while the former overcompensates the latter by about 30% in the tropics due to the Indo-Pacific change. The BJC can be understood from the viewpoint of large-scale circulation change. However, the intrinsic mechanism of BJC is related to the climate feedback of the Earth system. The authors’ coupled model experiments confirm that the occurrence of BJC is an intrinsic requirement of local energy balance, and local climate feedback determines the extent of BJC, consistent with previous theoretical results. Even during the transient period of climate change, the BJC is well established when the ocean heat storage is slowly varying and its change is much weaker than the net local heat flux change at the ocean surface. The BJC can be deduced from the local climate feedback. Under the freshwater forcing, the overcompensation in the tropics is mainly caused by the positive longwave feedback related to clouds, and the undercompensation in the extratropics is due to the negative longwave feedback related to surface temperature change. Different dominant feedbacks determine different BJC scenarios in different regions, which are in essence constrained by local energy balance."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2461 on: December 29, 2019, 06:11:14 AM »
The linked reference demonstrates that climate response is dependent on the actual forcing pattern, and AR5 does not adequately model the true current model boundary conditions, nor the actual regional distributions of anthropogenic radiative forcing:

A. D. Haugstad, K. C. Armour, D. S. Battisti & B. E. J. Rose (27 July 2017), "Relative roles of surface temperature and climate forcing patterns in the inconstancy of radiative feedbacks", Geophysical Research Letters, DOI: 10.1002/2017GL074372 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL074372/abstract

Abstract: "Radiative feedbacks robustly vary over time in transient warming simulations. Published studies offer two explanations: (i) evolving patterns of ocean heat uptake (OHU) or radiative forcing give rise to OHU or forcing “efficacies” and (ii) evolving patterns of surface temperature change. This study seeks to determine whether these explanations are indeed distinct. Using an idealized framework of an aquaplanet atmosphere-only model, we show that radiative feedbacks depend on the pattern of climate forcing. Yet the same feedbacks arise when the temperature pattern induced by that climate forcing is prescribed in the absence of any forcing. These findings suggest the perspective that feedbacks are influenced by efficacies of forcing and OHU is equivalent to the perspective that feedbacks are dependent on the temperature patterns induced by those forcings. Prescribed surface temperature simulations are thus valuable for studying the temporal evolution of radiative feedbacks."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2462 on: December 29, 2019, 06:24:46 AM »
The linked reference indicates that the time required to recharge the Western Pacific warm water pool has decreased from 1.5–3.5 years, in the 1979–99 period, to 0.8–1.3 years, in the 2000–16 period.  This is a clear sign that climate sensitivity is likely accelerating from the recent past, due to increased El Nino events:

Zeng-Zhen Hu et al (2017), "On the Shortening of the Lead Time of Ocean Warm Water Volume to ENSO SST Since 2000", Scientific Reports 7, Article number: 4294, doi:10.1038/s41598-017-04566-z

http://www.nature.com/articles/s41598-017-04566-z

Abstract; "The possible factors associated with the shortening of lead time between ocean warm water volume (WWV) variability along the equatorial Pacific and El Niño–Southern Oscillation (ENSO) variability after 2000 are documented. It is shown that the shortening of lead time is due to frequency increases of both WWV and ENSO. During 1979–99 the dominant frequencies were 1.5–3.5 years for both the Niño3.4 and WWV indices. In contrast, during 2000–16, both indices had a relatively flatter spectrum and were closer to a white noise process with a relative maximum at 1.5–2.0 years for the Niño3.4 index and 0.8–1.3 years for the WWV index. The frequency change of ENSO and WWV were linked to a westward shift of the Bjerknes feedback region. The results here are consistent with previous argument that the westward shift of the air-sea coupling region will cause an increase of ENSO frequency, as the corresponding zonal advection feedback reduces the period and growth of coupled instability, thus favoring more frequent and weak El Niño events."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2463 on: December 29, 2019, 06:28:41 AM »
The linked reference indicates that a modeled doubling of atmospheric CO₂ concentrations (think of  CO2e) leads to poleward shifts in the wintertime ocean heat flux convergence (OHFC); which results in enhanced Polar Amplification as compared to prior analyses (like CMIP5):

H. A. Singh, P. J. Rasch & B. E. J. Rose (1 September 2017), "Increased Ocean Heat Convergence into the High Latitudes with CO2-Doubling Enhances Polar-Amplified Warming", Geophysical Research Letters, DOI: 10.1002/2017GL074561

http://onlinelibrary.wiley.com/doi/10.1002/2017GL074561/abstract?utm_content=buffer60507&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "We isolate the role of the ocean in polar climate change by directly evaluating how changes in ocean dynamics with quasi-equilibrium CO2-doubling impact high-latitude climate. With CO2-doubling, the ocean heat flux convergence (OHFC) shifts poleward in winter in both hemispheres. Imposing this pattern of perturbed OHFC in a global climate model results in a poleward shift in ocean-to-atmosphere turbulent heat fluxes (both sensible and latent) and sea ice retreat; the high-latitudes warm while the midlatitudes cool, thereby amplifying polar warming. Furthermore, midlatitude cooling is propagated to the polar mid-troposphere on isentropic surfaces, augmenting the (positive) lapse rate feedback at high latitudes. These results highlight the key role played by the partitioning of meridional energy transport changes between the atmosphere and ocean in high-latitude climate change."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2464 on: December 30, 2019, 01:17:02 AM »
The linked reference indicates that the IPCC underestimated methane emissions from livestock:

Julie Wolf, Ghassem R. Asrar and Tristram O. West (2017), "Revised methane emissions factors and spatially distributed annual carbon fluxes for global livestock", Carbon Balance and Management, 12:16, https://doi.org/10.1186/s13021-017-0084-y

https://cbmjournal.springeropen.com/articles/10.1186/s13021-017-0084-y

Abstract: "Background
Livestock play an important role in carbon cycling through consumption of biomass and emissions of methane. Recent research suggests that existing bottom-up inventories of livestock methane emissions in the US, such as those made using 2006 IPCC Tier 1 livestock emissions factors, are too low. This may be due to outdated information used to develop these emissions factors. In this study, we update information for cattle and swine by region, based on reported recent changes in animal body mass, feed quality and quantity, milk productivity, and management of animals and manure. We then use this updated information to calculate new livestock methane emissions factors for enteric fermentation in cattle, and for manure management in cattle and swine.

Results

Using the new emissions factors, we estimate global livestock emissions of 119.1 ± 18.2 Tg methane in 2011; this quantity is 11% greater than that obtained using the IPCC 2006 emissions factors, encompassing an 8.4% increase in enteric fermentation methane, a 36.7% increase in manure management methane, and notable variability among regions and sources. For example, revised manure management methane emissions for 2011 in the US increased by 71.8%. For years through 2013, we present (a) annual livestock methane emissions, (b) complete annual livestock carbon budgets, including carbon dioxide emissions, and (c) spatial distributions of livestock methane and other carbon fluxes, downscaled to 0.05 × 0.05 degree resolution.

Conclusions
Our revised bottom-up estimates of global livestock methane emissions are comparable to recently reported top-down global estimates for recent years, and account for a significant part of the increase in annual methane emissions since 2007. Our results suggest that livestock methane emissions, while not the dominant overall source of global methane emissions, may be a major contributor to the observed annual emissions increases over the 2000s to 2010s. Differences at regional and local scales may help distinguish livestock methane emissions from those of other sectors in future top-down studies. The revised estimates allow improved reconciliation of top-down and bottom-up estimates of methane emissions, will facilitate the development and evaluation of Earth system models, and provide consistent regional and global Tier 1 estimates for environmental assessments."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2465 on: December 30, 2019, 01:18:53 AM »
The linked reference address how the collapse of the WAIS can alter oceanic and atmospheric patterns, leading to Super Interglacial conditions:

Flavio Justino, Douglas Lindemann, Fred Kucharski, Aaron Wilson, David Bromwich, and Frode Stordal (2017), "Oceanic response to changes in the WAIS and astronomical forcing during the MIS31 superinterglacial", Clim. Past, 13, 1081–1095, https://doi.org/10.5194/cp-13-1081-2017

https://www.clim-past.net/13/1081/2017/cp-13-1081-2017.pdf

Abstract: "Marine Isotope Stage 31 (MIS31, between 1085 and 1055 ka) was characterized by higher extratropical air temperatures and a substantial recession of polar glaciers compared to today.  Paleoreconstructions and model simulations have increased the understanding of the MIS31 interval, but questions remain regarding the role of the Atlantic and Pacific oceans in modifying the climate associated with the variations in Earth’s orbital parameters. Multi-century coupled climate simulations, with the astronomical configuration of the MIS31 and modified West Antarctic Ice Sheet (WAIS) topography, show an increase in the thermohaline flux and northward oceanic heat transport (OHT) in the Pacific Ocean.  These oceanic changes are driven by anomalous atmospheric circulation and increased surface salinity in concert with a stronger meridional overturning circulation (MOC). The intensified northward OHT is responsible for up to 85% of the global OHT anomalies and contributes to the overall reduction in sea ice in the Northern Hemisphere (NH) due to Earth’s astronomical configuration. The relative contributions of the Atlantic Ocean to global OHT and MOC anomalies are minor compared to those of the Pacific.  However, sea ice changes are remarkable, highlighted by decreased (increased) cover in the Ross (Weddell) Sea but widespread reductions in sea ice across the NH."

Extract: "Based on coupled climate simulations performed under present day and boundary conditions representative of Marine Isotope Stage 31 (MIS31), our analyses provide evidence that under MIS31 climate conditions there was a remarkable reduction in sea ice distribution across the NH due to the astronomical configuration of that epoch. This contrasts with increases in sea ice area across the SH. The climate response to collapsing the WAIS is prominent in the vicinity of the Antarctic continent, whereas the effect of modification in the Earth orbital configuration extends worldwide.

It has furthermore been demonstrated that the MIS31 interglacial experienced significant changes in the Meridional Overturning Circulation (MOC). In the Atlantic, increases in the MOC are related to an intensified westerly atmospheric flow in the northern North Atlantic, leading to strong convective mixing. The main convection sites in MIS31 have also been shifted poleward compared to the control simulation (CTR) in concert with changes in the position of the meridional thermal gradient."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2466 on: December 30, 2019, 01:22:26 AM »
The linked references all provides evidence supporting Hansen's ice-climate interaction mechanism associated with ice mass loss from the WAIS:

Pepijn Bakker et al, Centennial-scale Holocene climate variations amplified by Antarctic Ice Sheet discharge, Nature (2016). DOI: 10.1038/nature20582

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature20582.html

Abstract: "Proxy-based indicators of past climate change show that current global climate models systematically underestimate Holocene-epoch climate variability on centennial to multi-millennial timescales, with the mismatch increasing for longer periods. Proposed explanations for the discrepancy include ocean–atmosphere coupling that is too weak in models, insufficient energy cascades from smaller to larger spatial and temporal scales, or that global climate models do not consider slow climate feedbacks related to the carbon cycle or interactions between ice sheets and climate. Such interactions, however, are known to have strongly affected centennial- to orbital-scale climate variability during past glaciations, and are likely to be important in future climate change. Here we show that fluctuations in Antarctic Ice Sheet discharge caused by relatively small changes in subsurface ocean temperature can amplify multi-centennial climate variability regionally and globally, suggesting that a dynamic Antarctic Ice Sheet may have driven climate fluctuations during the Holocene. We analysed high-temporal-resolution records of iceberg-rafted debris derived from the Antarctic Ice Sheet, and performed both high-spatial-resolution ice-sheet modelling of the Antarctic Ice Sheet and multi-millennial global climate model simulations. Ice-sheet responses to decadal-scale ocean forcing appear to be less important, possibly indicating that the future response of the Antarctic Ice Sheet will be governed more by long-term anthropogenic warming combined with multi-centennial natural variability than by annual or decadal climate oscillations."

&

Johannes Sutter, Paul Gierz, Klaus Grosfeld, Malte Thoma, Gerrit Lohmann (2016), "Ocean temperature thresholds for Last Interglacial West Antarctic Ice Sheet collapse", Geophysical Research Letters, DOI: 10.1002/2016GL067818

http://onlinelibrary.wiley.com/doi/10.1002/2016GL067818/full

Abstract: "The West Antarctic Ice Sheet (WAIS) is considered the major contributor to global sea level rise in the Last Interglacial (LIG) and potentially in the future. Exposed fossil reef terraces suggest sea levels in excess of 7 m in the last warm era, of which probably not much more than 2 m are considered to originate from melting of the Greenland Ice Sheet. We simulate the evolution of the Antarctic Ice Sheet during the LIG with a 3-D thermomechanical ice sheet model forced by an atmosphere-ocean general circulation model (AOGCM). Our results show that high LIG sea levels cannot be reproduced with the atmosphere-ocean forcing delivered by current AOGCMs. However, when taking reconstructed Southern Ocean temperature anomalies of several degrees, sensitivity studies indicate a Southern Ocean temperature anomaly threshold for total WAIS collapse of 2–3°C, accounting for a sea level rise of 3–4 m during the LIG. Potential future Antarctic Ice Sheet dynamics range from a moderate retreat to a complete collapse, depending on rate and amplitude of warming."

&

Julien P. Nicolas et. al. (2017), "January 2016 extensive summer melt in West Antarctica favoured by strong El Nino", Nature Communications, DOI: 10.1038/ncomms15799

http://www.ccpo.odu.edu/~klinck/Reprints/PDF/nicolasNatComm17.pdf

Abstract: "Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Nino event. The increase in the number of extreme El Nino events projected for the twenty-first century could expose the WAIS to more frequent major melt events."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2467 on: December 30, 2019, 01:26:43 AM »
The linked reference concludes: "... the specific equilibrium climate sensitivity which considers radiative forcing of CO2 and land ice sheet (LI) albedo, S[CO2,LI], is larger during interglacial states than during glacial conditions by more than a factor two."  This is not good news:

Peter Koehler, Lennert Stap, Anna von der Heydt, Bas de Boer, Roderik, S. W. van de Wal & Jonah Bloch-Johnson (4 October 2017), "A state-dependent quantification of climate sensitivity based on paleo data of the last 2.1 million years", Paleoceanography, DOI: 10.1002/2017PA003190

http://onlinelibrary.wiley.com/doi/10.1002/2017PA003190/abstract?utm_content=bufferc4dad&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "The evidence from both data and models indicates that specific equilibrium climate sensitivity S[X] — the global annual mean surface temperature change (ΔTg) as a response to a change in radiative forcing X (ΔR[X]) — is state-dependent. Such a state dependency implies that the best fit in the scatter plot of ΔTg versus ΔR[X] is not a linear regression, but can be some non-linear or even non-smooth function. While for the conventional linear case the slope (gradient) of the regression is correctly interpreted as the specific equilibrium climate sensitivity S[X], the interpretation is not straightforward in the non-linear case. We here explain how such a state-dependent scatter plot needs to be interpreted, and provide a theoretical understanding — or generalization — how to quantify S[X] in the non-linear case. Finally, from data covering the last 2.1 Myr we show that — due to state dependency — the specific equilibrium climate sensitivity which considers radiative forcing of CO2 and land ice sheet (LI) albedo, S[CO2,LI], is larger during interglacial states than during glacial conditions by more than a factor two."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2468 on: December 30, 2019, 01:29:56 AM »
The linked reference provides paleo data (from the past 360,000 years) that the ENSO assumes a La Nina like pattern during glacial periods and assumes an El Nino like pattern during rapidly changing portions of interglacial periods.  As we are in the most rapidly changing interglacial period on record, this is not good news:

Zhang, S., Li, T., Chang, F. et al. Chin. J. (2017), "Correspondence between the ENSO-like state and glacial-interglacial condition during the past 360 kyr", Ocean. Limnol., 35: 1018. https://doi.org/10.1007/s00343-017-6082-9

https://link.springer.com/article/10.1007/s00343-017-6082-9#citeas

Abstract: "In the warming world, tropical Pacific sea surface temperature (SST) variation has received considerable attention because of its enormous influence on global climate change, particularly the El Niño-Southern Oscillation process. Here, we provide new high-resolution proxy records of the magnesium/calcium ratio and the oxygen isotope in foraminifera from a core on the Ontong-Java Plateau to reconstruct the SST and hydrological variation in the center of the Western Pacific Warm Pool (WPWP) over the last 360 000 years. In comparison with other Mg/Ca-derived SST and δ18O records, the results suggested that in a relatively stable condition, e.g., the last glacial maximum (LGM) and other glacial periods, the tropical Pacific would adopt a La Niña-like state, and the Walker and Hadley cycles would be synchronously enhanced. Conversely, El Niño-like conditions could have occurred in the tropical Pacific during fast changing periods, e.g., the termination and rapidly cooling stages of interglacial periods. In the light of the sensitivity of the Eastern Pacific Cold Tongue (EPCT) and the inertia of the WPWP, we hypothesize an inter-restricted relationship between the WPWP and EPCT, which could control the zonal gradient variation of SST and affect climate change."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2469 on: December 30, 2019, 01:34:37 AM »
The linked reference studies the paleo decay of the Cordilleran ice sheet and finds that it lost most of its ice mass earlier than consensus science previously thought, and it lost much of its ice mass over a relatively short period.  Personally, I am concerned about the impact of rainfall at increasingly high latitudes (with warming) on both the Greenland Ice Sheet, on Arctic permafrost, and on the WAIS:

B. Menounos et al (10 Nov 2017), "Cordilleran Ice Sheet mass loss preceded climate reversals near the Pleistocene Termination", Science, Vol. 358, Issue 6364, pp. 781-784, DOI: 10.1126/science.aan3001

http://science.sciencemag.org/content/358/6364/781

Abstract: "The Cordilleran Ice Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were ice free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bølling-Allerød warmth halved the mass of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bølling-Allerød and Younger Dryas."

Disappearance of an ice sheet

The Cordilleran Ice Sheet is thought to have covered westernmost Canada until about 13,000 years ago, even though the warming and sea level rise of the last deglaciation had begun more than a thousand years earlier. This out-of-phase behavior has puzzled glaciologists because it is not clear what mechanisms could account for it. Menounos et al. report measurements of the ages of cirque and valley glaciers that show that much of western Canada was ice-free as early as 14,000 years ago—a finding that better agrees with the record of global ice volume (see the Perspective by Marcott and Shakun). Previous reconstructions seem not to have adequately reflected the complexity of ice sheet decay.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2470 on: December 30, 2019, 01:35:37 AM »
The linked open access article indicates that the cooling effects of future volcanic eruptions will be less with continued global warming.  This implies that ECS will be a little bit higher than consensus science has previously assumed, both with regard to paleo data and future projections:

Peter O. Hopcroft, Jessy Kandlbauer, Paul J. Valdes& R. Stephen J. Sparks (2017), "Reduced cooling following future volcanic eruptions", Climate Dynamics, pp 1–15, DOI: https://doi.org/10.1007/s00382-017-3964-7

https://link.springer.com/article/10.1007%2Fs00382-017-3964-7

Abstract: "Volcanic eruptions are an important influence on decadal to centennial climate variability. Large eruptions lead to the formation of a stratospheric sulphate aerosol layer which can cause short-term global cooling. This response is modulated by feedback processes in the earth system, but the influence from future warming has not been assessed before. Using earth system model simulations we find that the eruption-induced cooling is significantly weaker in the future state. This is predominantly due to an increase in planetary albedo caused by increased tropospheric aerosol loading with a contribution from associated changes in cloud properties. The increased albedo of the troposphere reduces the effective volcanic aerosol radiative forcing. Reduced sea-ice coverage and hence feedbacks also contribute over high-latitudes, and an enhanced winter warming signal emerges in the future eruption ensemble. These findings show that the eruption response is a complex function of the environmental conditions, which has implications for the role of eruptions in climate variability in the future and potentially in the past."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2471 on: December 30, 2019, 01:37:32 AM »
the Mid-Brunhes Event (MBE) coincides with MIS 11 (the Holsteinian) about 400,000 to 350,000 years ago, and marks a major transition to subsequent enhanced Arctic Amplification as discussed in the open access linked reference (see the first three attached images while the fourth image from another source help to clarify that after the MBE interglacial peak global mean peak temperatures have been higher).  Furthermore, the reference associates this change with the bipolar seesaw and episodic collapses of the WAIS.  This research clearly associates the bipolar seesaw mechanism with Hansen's ice-climate feedback and with Arctic Amplification. 

Cronin et al (2017), "Enhanced Arctic Amplification Began at the Mid-Brunhes Event ~400,000 years ago", Scientific Reports 7, Article No. 14475, doi: 10.1038/s41598-017-13821-2

https://www.nature.com/articles/s41598-017-13821-2

Extract: "Enhanced Arctic amplification at the MBE suggests a major climate threshold was reached at ~400 ka involving Atlantic Meridional Overturning Circulation (AMOC), inflowing warm Atlantic Layer water, ice sheet, sea-ice and ice-shelf feedbacks, and sensitivity to higher post-MBE interglacial CO₂ concentrations.

Southern Hemisphere ocean-atmosphere-sea ice processes are critical for understanding the MBE, specifically the idea that there is a bipolar seesaw operating between Northern and Southern Hemispheres on millennial timescales explain warmer interglacial condition in the Southern Hemisphere.  Barker et al. (2011) demonstrated that abrupt millennial-scale AMOC variability characterized the last 800 ka, albeit without the large amplitude shift seen in our Arctic records.  Holden et al. proposed a role for decreased stability of the West Antarctic Ice Sheet following the MBE, leading to AMOC slowdown during deglacials.  Thus, it is possible that ice sheet/ice shelf instability characterized both hemispheres providing the necessary non-linear dynamics to explain large amplitude temperature events in the Arctic Ocean.  However establishing the relationship between bottom temperature, sea ice and productivity during stadial and interstadial periods – require better sediment core resolution in the Arctic.  Nonetheless, the large shift in Arctic land ice, ice shelves and sea ice at the MBE, suggests an amplification of Arctic climate sensitivity related to higher interglacial CO₂ concentrations and associated feedbacks involving ice shelves and ice sheets, Heinrich-like events, AMOC-forcing Arctic Ocean temperature oscillations, and deeper submergence of Atlantic water in the central Arctic Basin."

Furthermore, the next linked reference studies the Last Glacial Termination, LGT, from 18,000 to 11,650 kya, and reconstructs the dynamic response of the Antarctic ice sheets to warming in this period and it clarifies the important role that the Pacific Ocean (and the ENSO) plays in both the bipolar seesaw and the ice-climate feedback mechanism.  The abstract from the linked reference concludes: "Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections.  With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise."

Fogwill, et. al. (2017), "Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the last Glacial Termination", Scientific Reports 7, Article number 39979, doi:10.1038/srep39979

https://www.nature.com/articles/srep39979
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2472 on: December 30, 2019, 03:55:17 AM »
Given that AR5 included no increased carbon-climate feedbacks from northern soils, the fact that the linked reference finds that this feedback mechanism is strong, helps to illustrate how far on the side of least drama that AR5 errs:

Koven et al. (2017), "Higher climatological temperature sensitivity of soil carbon in cold than warm climates", Nature Climate Change, doi:10.1038/nclimate3421

http://www.nature.com/articles/nclimate3421

Extract: "… we show that the climatological temperature control on carbon turnover in the top metre of global soils is more sensitive in cold climates than in warm climates and argue that it is critical to capture this emergent ecosystem property in global-scale models.

These results support projections of strong carbon-climate feedbacks from northern soils and demonstrate a method for ESMs to capture this emergent behavior."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2473 on: December 30, 2019, 03:58:10 AM »
The linked open access reference indicates that land use change will likely play a 50% larger role in future radiative forcing scenarios than previously assumed by the SSP scenarios:

Fuchs, R., Prestele, R., and Verburg, P. H.: A global assessment of gross and net land change dynamics for current conditions and future scenarios, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2017-121, in review, 2017.

https://www.earth-syst-dynam-discuss.net/esd-2017-121/
&
https://www.earth-syst-dynam-discuss.net/esd-2017-121/esd-2017-121.pdf

Abstract. The consideration of gross land changes, meaning all area gains and losses within a pixel or administrative unit (e.g. country), plays an essential role in the estimation of total land changes. Gross land changes affect the magnitude of total land changes, which feeds back to the attribution of biogeochemical and biophysical processes related to climate change in Earth System Models. Global empirical studies on gross land changes are currently lacking. Whilst the relevance of gross changes for global change has been indicated in the literature, it is not accounted for in future land change scenarios. In this study, we extract gross and net land change dynamics from large-scale and high-resolution (30–100 m) remote sensing products to create a new global gross and net change dataset. Subsequently, we developed an approach to integrate our empirically derived gross and net changes with the results of future simulation models, by accounting for the gross and net change addressed by the land use model and the gross and net change that is below the resolution of modelling. Based on our empirical data, we found that gross land change within 0.5-degree grid cells were substantially larger than net changes in all parts of the world. As 0.5-degree grid cells are a standard resolution of Earth System Models, this leads to an underestimation of the amount of change. This finding contradicts earlier studies, which assumed gross land changes to appear in shifting cultivation areas only. Applied in a future scenario, the consideration of gross land changes led to approximately 50 % more land changes globally compared to a net land change representation. Gross land changes were most important in heterogeneous land systems with multiple land uses (e.g. shifting cultivation, smallholder farming, and agro-forestry systems). Moreover, the importance of gross changes decreased over time due to further polarization and intensification of land use. Our results serve as empirical database for land change dynamics that can be applied in Earth System Models and Integrated Assessment Models.

Extract: "In this study, we could show that that, based on empirical data, gross land changes occur globally in every world region. This finding contradicts earlier studies, which assumed gross land changes to appear in shifting cultivation areas only. Applied to our future reference scenario, net land changes led globally to an average of 0.92% area change per year, while for gross land changes the average change rate was 1.35% per year. This is an increase of roughly 50% compared to the net change approach.  Empirical data contributed ca. 80% of changes in the future scenario we used. This highlights the importance of accounting for sub-pixel processes in global assessments. In our scenario, gross land changes appeared in regional patterns, most dominant in Eastern Europe, Turkey, the Sahel zone, the United States and development countries in transition, like the BRICS states (Brazil, Russia, India, China and South Africa). Large-scale and high-resolution remote sensing data was crucial for this kind of assessment. This highlights the increasing importance of land related remote sensing data in global assessments. With our approach, it is possible to further decrease uncertainties in land changes dynamics and related land atmosphere fluxes in ESMs.  This again, helps to improve accuracies for future mitigation and adaptation scenarios."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2474 on: December 30, 2019, 04:02:16 AM »
The linked reference discusses the threat of very-short-lived-substances to the expected recovery of the stratospheric ozone; which could mean that the AR5 ozone projections are wishful thinking.

Oram, D. E., Ashfold, M. J., Laube, J. C., Gooch, L. J., Humphrey, S., Sturges, W. T., Leedham-Elvidge, E., Forster, G. L., Harris, N. R. P., Mead, M. I., Samah, A. A., Phang, S. M., Ou-Yang, C.-F., Lin, N.-H., Wang, J.-L., Baker, A. K., Brenninkmeijer, C. A. M., and Sherry, D.: A growing threat to the ozone layer from short-lived anthropogenic chlorocarbons, Atmos. Chem. Phys., 17, 11929-11941, https://doi.org/10.5194/acp-17-11929-2017, 2017.

https://www.atmos-chem-phys.net/17/11929/2017/

Abstract. Large and effective reductions in emissions of long-lived ozone-depleting substance (ODS) are being achieved through the Montreal Protocol, the effectiveness of which can be seen in the declining atmospheric abundances of many ODSs. An important remaining uncertainty concerns the role of very short-lived substances (VSLSs) which, owing to their relatively short atmospheric lifetimes (less than 6 months), are not regulated under the Montreal Protocol. Recent studies have found an unexplained increase in the global tropospheric abundance of one VSLS, dichloromethane (CH2Cl2), which has increased by around 60 % over the past decade. Here we report dramatic enhancements of several chlorine-containing VSLSs (Cl-VSLSs), including CH2Cl2 and CH2ClCH2Cl (1,2-dichloroethane), observed in surface and upper-tropospheric air in East and South East Asia. Surface observations were, on occasion, an order of magnitude higher than previously reported in the marine boundary layer, whilst upper-tropospheric data were up to 3 times higher than expected. In addition, we provide further evidence of an atmospheric transport mechanism whereby substantial amounts of industrial pollution from East Asia, including these chlorinated VSLSs, can rapidly, and regularly, be transported to tropical regions of the western Pacific and subsequently uplifted to the tropical upper troposphere. This latter region is a major provider of air entering the stratosphere, and so this mechanism, in conjunction with increasing emissions of Cl-VSLSs from East Asia, could potentially slow the expected recovery of stratospheric ozone.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2475 on: December 30, 2019, 04:04:29 AM »
Increasing Arctic Amplification is closely related to the increase in low-elevation cloud cover, and the linked reference finds: "… that the response of low-level clouds in the Arctic to anthropogenic aerosols lies close to a theoretical maximum and is between 2 and 8 times higher than has been observed elsewhere."

Q. Coopman, T. J. Garrett, D. P. Finch & J. Riedi (3 January 2018), "High Sensitivity of Arctic Liquid Clouds to Long-Range Anthropogenic Aerosol Transport", Geophysical Research Letters, DOI: 10.1002/2017GL075795 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075795/full

Abstract: "The rate of warming in the Arctic depends upon the response of low-level microphysical and radiative cloud properties to aerosols advected from distant anthropogenic and biomass-burning sources. Cloud droplet cross-section density increases with higher concentrations of cloud condensation nuclei, leading to an increase of cloud droplet absorption and scattering radiative cross sections. The challenge of assessing the magnitude of the effect has been decoupling the aerosol impacts on clouds from how clouds change solely due to natural meteorological variability. Here we address this issue with large, multi-year satellite, meteorological, and tracer transport model data sets to show that the response of low-level clouds in the Arctic to anthropogenic aerosols lies close to a theoretical maximum and is between 2 and 8 times higher than has been observed elsewhere. However, a previously described response of arctic clouds to biomass-burning plumes appears to be overstated because the interactions are rare and modification of cloud radiative properties appears better explained by coincident changes in temperature, humidity, and atmospheric stability."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2476 on: December 30, 2019, 04:07:05 AM »
The linked reference by Marvel et al (2018) indicates that estimates of ECS based on "… recent observations and energy balance models are biased low …". 

Kate Marvel, Robert Pincus, Gavin A. Schmidt & Ron L. Miller (29 January 2018), "Internal variability and disequilibrium confound estimates of climate sensitivity from observations", Geophysical Research Letters, DOI: 10.1002/2017GL076468 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076468/full

Abstract: "An emerging literature suggests that estimates of equilibrium climate sensitivity (ECS) derived from recent observations and energy balance models are biased low because models project more positive climate feedbacks in the far future. Here, we use simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to show that across models, ECS inferred from the recent historical period (1979-2005) is indeed almost uniformly lower than that inferred from simulations subject to abrupt increases in CO2 radiative forcing. However, ECS inferred from simulations in which sea surface temperatures are prescribed according to observations is lower still. ECS inferred from simulations with prescribed sea surface temperatures is strongly linked to changes to tropical marine low clouds. However, feedbacks from these clouds are a weak constraint on long-term model ECS. One interpretation is that observations of recent climate changes constitute a poor direct proxy for long term sensitivity."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2477 on: December 30, 2019, 04:10:24 AM »
The linked reference indicates that human-induced land use change has a more positive feedback than recognized by AR5 models:

Gries, T., Redlin, M. & Ugarte, J.E. (2018), "Human-induced climate change: the impact of land-use change", Theor Appl Climatol, https://doi.org/10.1007/s00704-018-2422-8

https://rd.springer.com/article/10.1007%2Fs00704-018-2422-8?utm_content=bufferb6d5d&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "For hundreds of years, human activity has modified the planet’s surface through land-use practices. Policies and decisions on how land is managed and land-use changes due to replacement of forests by agricultural cropping and grazing lands affect greenhouse gas emissions. Agricultural management and agroforestry and the resulting changes to the land surface alter the global carbon cycle as well as the Earth’s surface albedo, both of which in turn change the Earth’s radiation balance. This makes land-use change the second anthropogenic source of climate change after fossil fuel burning. However, the scientific research community has so far not been able to identify the direction and magnitude of the global impact of land-use change. This paper examines the effects of net carbon flux from land-use change on temperature by applying Granger causality and error correction models. The results reveal a significant positive long-run equilibrium relationship between land-use change and the temperature series as well as an opposing short-term effect such that land-use change tends to lead to global warming; however, a rise in temperature causes a decline in land-use change."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2478 on: December 30, 2019, 04:11:18 AM »
The linked reference indicates that the continuing deforestation of mangrove forests is contributing to net CO₂ emissions:

Stuart E. Hamilton & Daniel A. Friess, (2018), "Global carbon stocks and potential emissions due to mangrove deforestation from 2000 to 2012", Nature Climate Change, volume 8, pages240–244, doi:10.1038/s41558-018-0090-4

http://www.nature.com/articles/s41558-018-0090-4

Abstract: "Mangrove forests store high densitie of organic carbon, which, when coupled with high rates of deforestation, means that mangroves have the potential to contribute substantially to carbon emissions. Consequently, mangroves are strong candidates for inclusion in nationally determined contributions (NDCs) to the United Nations Framework Convention on Climate Change (UNFCCC), and payments for ecosystem services (PES) programmes that financially incentivize the conservation of forested carbon stocks. This study quantifies annual mangrove carbon stocks from 2000 to 2012 at the global, national and sub-national levels, and global carbon emissions resulting from deforestation over the same time period. Globally, mangroves stored 4.19 Pg of carbon in 2012, with Indonesia, Brazil, Malaysia and Papua New Guinea accounting for more than 50% of the global stock. 2.96 Pg of the global carbon stock is contained within the soil and 1.23 Pg in the living biomass. Two percent of global mangrove carbon was lost between 2000 and 2012, equivalent to a maximum potential of 316,996,250 t of CO2 emissions."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2479 on: December 30, 2019, 05:47:08 PM »
The linked reference evaluates 19 previously proposed constraints on ECS, and it could not verify the applicability of 15 of these proposed constraints, but it did find that 4 of the 19 constraints "… all predict relatively high climate sensitivity."

 Peter M. Caldwell, Mark D. Zelinka, and Stephen A. Klein (2018), "Evaluating Emergent Constraints on Equilibrium Climate Sensitivity", Journal of Climate, https://doi.org/10.1175/JCLI-D-17-0631.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0631.1?utm_content=buffer3197b&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Emergent constraints are quantities which are observable from current measurements and have skill predicting future climate. This study explores 19 previously-proposed emergent constraints related to equilibrium climate sensitivity (ECS, the global-average equilibrium surface temperature response to CO2 doubling). Several constraints are shown to be closely related, emphasizing the importance for careful understanding of proposed constraints. A new method is presented for decomposing correlation between an emergent constraint and ECS into terms related to physical processes and geographical regions. Using this decomposition, one can determine whether the processes and regions explaining correlation with ECS correspond to the physical explanation offered for the constraint. Shortwave cloud feedback is generally found to be the dominant contributor to correlations with ECS because it is the largest source of inter-model spread in ECS. In all cases, correlation results from interaction between a variety of terms, reflecting the complex nature of ECS and the fact that feedback terms and forcing are themselves correlated with each other. For 4 of the 19 constraints, the originally-proposed explanation for correlation is borne out by our analysis. These 4 constraints all predict relatively high climate sensitivity. The credibility of 6 other constraints is called into question due to correlation with ECS coming mainly from unexpected sources and/or lack of robustness to changes in ensembles. Another 6 constraints lack a testable explanation and hence cannot be confirmed. The fact that this study casts doubt upon more constraints than it confirms highlights the need for caution when identifying emergent constraints from small ensembles."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2480 on: December 31, 2019, 08:33:55 AM »
Many SSP and RCP scenarios rely heavily on the use of climate-change mitigation efforts, but the linked reference casts doubt on the carbon uptake potential of BECCS:

Andreas Krause et al. (16 April 2018), "Large uncertainty in carbon uptake potential of land‐based climate‐change mitigation efforts" Global Change Biology, https://doi.org/10.1111/gcb.14144

https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14144

Abstract: "Most climate mitigation scenarios involve negative emissions, especially those that aim to limit global temperature increase to 2°C or less. However, the carbon uptake potential in land‐based climate change mitigation efforts is highly uncertain. Here, we address this uncertainty by using two land‐based mitigation scenarios from two land‐use models (IMAGE and MAgPIE) as input to four dynamic global vegetation models (DGVMs; LPJ‐GUESS, ORCHIDEE, JULES, LPJmL). Each of the four combinations of land‐use models and mitigation scenarios aimed for a cumulative carbon uptake of ~130 GtC by the end of the century, achieved either via the cultivation of bioenergy crops combined with carbon capture and storage (BECCS) or avoided deforestation and afforestation (ADAFF). Results suggest large uncertainty in simulated future land demand and carbon uptake rates, depending on the assumptions related to land use and land management in the models. Total cumulative carbon uptake in the DGVMs is highly variable across mitigation scenarios, ranging between 19 and 130 GtC by year 2099. Only one out of the 16 combinations of mitigation scenarios and DGVMs achieves an equivalent or higher carbon uptake than achieved in the land‐use models. The large differences in carbon uptake between the DGVMs and their discrepancy against the carbon uptake in IMAGE and MAgPIE are mainly due to different model assumptions regarding bioenergy crop yields and due to the simulation of soil carbon response to land‐use change. Differences between land‐use models and DGVMs regarding forest biomass and the rate of forest regrowth also have an impact, albeit smaller, on the results. Given the low confidence in simulated carbon uptake for a given land‐based mitigation scenario, and that negative emissions simulated by the DGVMs are typically lower than assumed in scenarios consistent with the 2°C target, relying on negative emissions to mitigate climate change is a highly uncertain strategy."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2481 on: December 31, 2019, 08:37:12 AM »
As indicated in the linked reference, tropical cloud cover is also migrating poleward; which is a positive feedback mechanism.  Thus while cloud feedback in some local areas may be becoming more negative; the global net cloud feedback is clearly becoming more positive, with increasing radiative forcing:

Masakazu Yoshimori et al. (2017), "The importance of ocean dynamical feedback for understanding the impact of mid-high latitude warming on tropical precipitation change", Journal of Climate, https://doi.org/10.1175/JCLI-D-17-0402.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0402.1?utm_content=bufferc45ef&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "It has been shown that asymmetric warming between the northern and southern hemisphere extratropics induces a meridional displacement of tropical precipitation. This shift is believed to be due to the extra energy transported from the differentially heated hemisphere through changes in the Hadley circulation. Generally, the column-integrated energy flux in the mean meridional overturning circulation follows the direction of the upper, relatively dry branch, and tropical precipitation tends to be intensified in the hemisphere with greater warming. This framework was originally applied to simulations that did not include ocean dynamical feedback, but was recently extended to take the ocean heat transport change into account. In the current study, an atmosphere-ocean general circulation model applied with a regional nudging technique is used to investigate the impact of extratropical warming on tropical precipitation change under realistic future climate projections. It is shown that warming at latitudes poleward of 40° causes the northward displacement of tropical precipitation from October to January. Warming at latitudes poleward of 60° alone has a much smaller effect. This change in the tropical precipitation is largely explained by the atmospheric moisture transport due to changes in the atmospheric circulation. The larger change in ocean heat transport near the equator, relative to the atmosphere, is consistent with the extended energy framework. The current study provides a complementary dynamical framework that highlights the importance of mid-latitude atmospheric eddies and equatorial ocean upwelling, where the atmospheric eddy feedback modifies the Hadley circulation resulting in the northward migration of precipitation and the ocean dynamical feedback damps the northward migration from the equator."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2482 on: December 31, 2019, 08:38:55 AM »
The linked reference indicates that terrestrial carbon sinks degrade more quickly when starting increased radiative forcing from pre-industrial conditions than from glacial conditions.  Thus Earth System Models, that were calibrated based on paleo data, should be recalibrated to expect faster loss of terrestrial carbon sinks for the rest of this century:

Adloff, M., Reick, C. H., and Claussen, M.: Earth system model simulations show different feedback strengths of the terrestrial carbon cycle under glacial and interglacial conditions, Earth Syst. Dynam., 9, 413-425, https://doi.org/10.5194/esd-9-413-2018, 2018.

https://www.earth-syst-dynam.net/9/413/2018/

Abstract. In simulations with the MPI Earth System Model, we study the feedback between the terrestrial carbon cycle and atmospheric CO2 concentrations under ice age and interglacial conditions. We find different sensitivities of terrestrial carbon storage to rising CO2 concentrations in the two settings. This result is obtained by comparing the transient response of the terrestrial carbon cycle to a fast and strong atmospheric CO2 concentration increase (roughly 900 ppm) in Coupled Climate Carbon Cycle Model Intercomparison Project (C4MIP)-type simulations starting from climates representing the Last Glacial Maximum (LGM) and pre-industrial times (PI). In this set-up we disentangle terrestrial contributions to the feedback from the carbon-concentration effect, acting biogeochemically via enhanced photosynthetic productivity when CO2 concentrations increase, and the carbon–climate effect, which affects the carbon cycle via greenhouse warming. We find that the carbon-concentration effect is larger under LGM than PI conditions because photosynthetic productivity is more sensitive when starting from the lower, glacial CO2 concentration and CO2 fertilization saturates later. This leads to a larger productivity increase in the LGM experiment. Concerning the carbon–climate effect, it is the PI experiment in which land carbon responds more sensitively to the warming under rising CO2 because at the already initially higher temperatures, tropical plant productivity deteriorates more strongly and extratropical carbon is respired more effectively. Consequently, land carbon losses increase faster in the PI than in the LGM case. Separating the carbon–climate and carbon-concentration effects, we find that they are almost additive for our model set-up; i.e. their synergy is small in the global sum of carbon changes. Together, the two effects result in an overall strength of the terrestrial carbon cycle feedback that is almost twice as large in the LGM experiment as in the PI experiment. For PI, ocean and land contributions to the total feedback are of similar size, while in the LGM case the terrestrial feedback is dominant.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Tom_Mazanec

  • Young ice
  • Posts: 4196
  • Earth will survive AGW...but will Homo sapiens?
    • View Profile
    • Planet Mazanec
  • Liked: 658
  • Likes Given: 510
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2483 on: December 31, 2019, 09:55:12 AM »
I learned through personal experience, when I was posting on AGW consequences, just how labor-intensive that is.
I think we should all give AbruptSLR our thanks for his posts on this thread.
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

blumenkraft

  • Guest
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2484 on: December 31, 2019, 06:39:38 PM »
I will!

Thanks a lot, AbruptSLR. A happy new year and keep up the great work. :)

Ken Feldman

  • Nilas ice
  • Posts: 1530
    • View Profile
  • Liked: 277
  • Likes Given: 149
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2485 on: December 31, 2019, 07:19:46 PM »
AbruptSLR does a great job of highlighting the potential impacts if we stay on what was termed "business as usual" energy scenarios from 10 years ago that drove the IPCC AR5 RCP 8.5 emissions pathway.  He ignores the fact that renewable energy is now cheaper than coal which makes RCP 8.5 to be a more extreme scenario than is possible.  Here are two articles on that subject.

http://nymag.com/intelligencer/2019/12/climate-change-worst-case-scenario-now-looks-unrealistic.html

Quote
We’re Getting a Clearer Picture of the Climate Future — and It’s Not as Bad as It Once Looked
By David Wallace-Wells

For once, the climate news might be better than you thought. It’s certainly better than I’ve thought.

You may not have noticed it, amid the flood of bad news about the “Emissions Gap” and the collapse of the COP25 climate conference in Madrid, but over the last few weeks a new narrative about the climate future has emerged, on balance encouraging, at least to an alarmist like me. It is this: As best as we can understand and project the medium- and long-term trajectories of energy use and emissions, the window of possible climate futures is probably narrowing, with both the most optimistic scenarios and the most pessimistic ones seeming, now, less likely.

Quote
The assumptions about those factors represent a variety of different no-policy futures, each reflecting different assumptions about the way the world’s energy systems and economies will evolve over the next decades. And the assumptions about those factors which are baked into RCP8.5 seem, by the year, more and more implausible — chiefly that global coal use, which is growing slowly, would dramatically increase over the rest of the century. Given that China is still opening new coal plants, and much of the developing world has yet to reach levels of prosperity where energy use explodes, some growth in coal is probably inevitable, perhaps even dramatic growth. But by 2100, RCP8.5 would require 6.5 times as much global coal use as we have today. That may be possible, given how much we don’t know about the path developing nations in south and southeast Asia and sub-Saharan Africa will take. But given recent drops in renewable pricing, and the positive signs for coal decline in the developed world, as a prediction about energy use RCP8.5 is probably closer to a “worst case,” outlier scenario than anything it would be fair to call “business as usual.”

https://thebreakthrough.org/issues/energy/3c-world

Quote
A 3C World Is Now “Business as Usual”
Dec 18, 2019

The world is on a path to warm around 3C above pre-industrial levels by 2100 under policies and commitments currently in place. This is a far cry from the 1.5C and 2C targets enshrined in the Paris agreements, but is also well short of the 4C to 5C warming in many “business as usual” baseline scenarios that continue to be widely used.

Two recently released reports — the International Energy Agency (IEA) 2019 World Energy Outlook (WEO) and the UN Environment Program (UNEP) 2019 Emissions Gap Report — both reflect current trends in clean energy technology costs and deployment and make the case that global emissions will be relatively flat over the next few decades. These estimates are on the low end of those in the latest set of fully integrated baseline scenarios featured in the energy modeling literature that intend to depict a world without climate policy — the Shared Socioeconomic Pathways (SSPs), developed for the upcoming 2021 IPCC 6th Assessment Report (AR6).

But what about by the end of the century? In this analysis, we take the 2040 IEA emissions projections and examine their implications for end-of-century warming. We find that IEA numbers imply that the most likely outcome of current policies is between 2.9-3.4C warming — which is reduced to around 2.7-3C warming if countries meet their current Paris Agreement commitments.


Quote
2040 fossil fuel and industry emissions for the three IEA scenarios compared to the range of baseline scenarios examined in the AR5 and the SSP Database. The SSP baseline and mitigation scenarios used by CMIP6 climate models in the upcoming IPCC AR6 are also shown for reference. IEA projections do not include emissions from industry, so FF&I values are calculated by adding a constant 2.4 GtCO2 reflecting 2018 industry emissions.

IEA CPS emissions in 2040 are in-between the SSP4-6.0 and SSP2-4.5 scenarios, and are in the bottom 15% of all the baseline scenarios in the SSP database. The SPS scenario is a bit below SSP2-4.5, and lower than any baseline scenarios — though this is not necessarily unexpected, as baseline scenarios exclude current commitments that have not yet been translated into policy.

Ken Feldman

  • Nilas ice
  • Posts: 1530
    • View Profile
  • Liked: 277
  • Likes Given: 149
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2486 on: December 31, 2019, 07:26:27 PM »
A couple of charts from that second linked reference above really make clear how extreme the RCP 8.5 (updated to SSP5-8.5 for AR6) scenario is compared to current energy use trends:

https://thebreakthrough.org/issues/energy/3c-world


Quote
Annual CO2 emissions from fossil fuel and industry in CPS and STPS IEA scenarios compared to the range of baseline scenarios examined in the SSP Database, as well as a subset of the baseline and mitigation scenarios chosen for use in the upcoming IPCC AR6 report.


Quote
Annual CO2 emissions from fossil fuel and industry in CPS and STPS IEA scenarios compared to the range of baseline scenarios examined in the SSP Database. Scenarios are extended from 2040 through 2100 by assuming constant emissions after 2040, or by assuming that the rate of emissions growth from 2030 to 2040 continues for the remainder of the century.

prokaryotes

  • Frazil ice
  • Posts: 258
    • View Profile
    • ClimateState.com
  • Liked: 48
  • Likes Given: 31
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2487 on: December 31, 2019, 07:43:41 PM »
RCP8.5 is probably closer to a “worst case,” outlier scenario than anything it would be fair to call “business as usual.”
How can that be if we factor in large scale warfare, or inundations tempering with nuke plants, or creating more wetland conditions, in turn creating more greenhouse gases? How is this the new worst case equated to BAU? As far as I know the hothouse climate state is a worst case scenario.

Quote
In the future, the Earth System could potentially follow many trajectories (12, 13), often represented by the large range of global temperature rises simulated by climate models (14). In most analyses, these trajectories are largely driven by the amount of greenhouse gases that human activities have already emitted and will continue to emit into the atmosphere over the rest of this century and beyond—with a presumed quasilinear relationship between cumulative carbon dioxide emissions and global temperature rise (14).

However, here we suggest that biogeophysical feedback processes within the Earth System coupled with direct human degradation of the biosphere may play a more important role than normally assumed, limiting the range of potential future trajectories and potentially eliminating the possibility of the intermediate trajectories.

We argue that there is a significant risk that these internal dynamics, especially strong nonlinearities in feedback processes, could become an important or perhaps, even dominant factor in steering the trajectory that the Earth System actually follows over coming centuries.
https://www.pnas.org/content/115/33/8252
CLIMATE STATE WEBSITE | YOUTUBE | VIMEO | TWITTER

Sam

  • Guest
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2488 on: December 31, 2019, 07:44:40 PM »
The unfortunate reality is that people do not behave logically. Neither does economics work in the way that free marketeers would wish to believe. People work diligently to protect their own interests. For many extremely wealthy interests that means distorting the political, social, and economic systems to ensure their investments continue to pay out.

That renewables are cheaper than coal and oil only now means that political and financial incentives and disincentives are being put in place to prevent economic factors from causing change. As with everything else, this is less effective than those interests would like, and far more effective than prudence necessitates to avoid calamity.

Said differently- economics will not save us because a whole lot of very financially interested parties have their very heavy hands on the scales. Wisdom and intellect won’t save us either for the same reason. Self interest also won’t save us for the same reason.

Add to all of those the time lags involved. People tend to act primarily based on felt pain. With climate change, by the time we feel the change it is already decades too late to act meaningfully.

ASLR does a great service for us in highlighting many of the papers that show the various factors involved. Under current rules, those won’t even be considered until a decade after they are published.

That of course is based on the lame idea that we need to base our decisions on settled science solely. Rather than using the precautionary principle (looking out through the windshield to see what’s coming) our rules require that the windshield be painted black and that we base our decisions on using binoculars to look at where we were in the past. 

Add to that the several year to decade long lag between the time the data comes into existence and the time the studies are completed and published and we are forced to base our decisions on information and reality that is at least a dozen years old.

Under that system we have no possibility of avoiding calamity and catastrophe. The real trajectory will then be based on the high end of the range of projected outcomes - made worse by our refusal to recognize our own limited understanding of the positive feedbacks that makes the reality even worse than our projections.

Sam

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2489 on: January 01, 2020, 04:06:21 AM »
Seawater percolation into below sea level layers of the firn in Antarctic ice shelves is not a good thing, and is more widespread than previously assumed:

Cook, S., Galton-Fenzi, B. K., Ligtenberg, S. R. M., and Coleman, R.: Brief Communication: Widespread potential for seawater infiltration on Antarctic ice shelves, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-146, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-146/

Abstract. Antarctica's future contribution to sea level change depends on the fate of its fringing ice shelves. One variable which may affect the rates of iceberg calving from ice shelves is the presence of liquid water, including the percolation of seawater into permeable firn layers. Here, we present evidence that most ice shelves around Antarctica have regions where permeable firn exists below sea level. The findings indicate that seawater infiltration onto ice shelves may be much more widespread in Antarctica than previously recognised. Our results present the most likely locations for seawater infiltration to occur, and may be used as an indicator of where future radar studies might be focussed.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2490 on: January 01, 2020, 04:07:48 AM »
The linked reference indicates that AR5 vintage models need to improve their representation of the stratosphere-troposphere coupling in order to better project coming extreme weather events, including those in Siberia:

Pengfei Zhang et al. (25 Jul 2018), "A stratospheric pathway linking a colder Siberia to Barents-Kara Sea sea ice loss", Science Advances, Vol. 4, no. 7, eaat6025, DOI: 10.1126/sciadv.aat6025

http://advances.sciencemag.org/content/4/7/eaat6025

Abstract: "Previous studies have extensively investigated the impact of Arctic sea ice anomalies on the midlatitude circulation and associated surface climate in winter. However, there is an ongoing scientific debate regarding whether and how sea ice retreat results in the observed cold anomaly over the adjacent continents. We present a robust “cold Siberia” pattern in the winter following sea ice loss over the Barents-Kara seas in late autumn in an advanced atmospheric general circulation model, with a well-resolved stratosphere. Additional targeted experiments reveal that the stratospheric response to sea ice forcing is crucial in the development of cold conditions over Siberia, indicating the dominant role of the stratospheric pathway compared with the direct response within the troposphere. In particular, the downward influence of the stratospheric circulation anomaly significantly intensifies the ridge near the Ural Mountains and the trough over East Asia. The persistently intensified ridge and trough favor more frequent cold air outbreaks and colder winters over Siberia. This finding has important implications for improving seasonal climate prediction of midlatitude cold events. The results also suggest that the model performance in representing the stratosphere-troposphere coupling could be an important source of the discrepancy between recent studies."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2491 on: January 01, 2020, 04:33:10 AM »
Per the linked article, recent consensus science overestimated the amount of methane absorbed by northern hemisphere forest soils:

Title: "Methane uptake from forest soils has ‘fallen by 77% in three decades’"

https://www.carbonbrief.org/methane-uptake-from-forest-soils-has-fallen-77-per-cent-three-decades

Extract: "The amount of methane absorbed by forest soils has fallen by an average of 77% in the northern hemisphere over the past 27 years, a new study finds.

The research, which analysed soil data taken from more than 300 studies, suggests that the world is currently “overestimating the role that forest soils play in trapping gas”, the lead author tells Carbon Brief."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2492 on: January 01, 2020, 04:36:18 AM »
The linked reference indicates that Permafrost carbon feedback (PCF) will be stronger than assumed by AR5 vintage climate change models:

Katey Walter Anthony, Thomas Schneider von Deimling, Ingmar Nitze, Steve Frolking, Abraham Emond, Ronald Daanen, Peter Anthony, Prajna Lindgren, Benjamin Jones, Guido Grosse. 21st-century modeled permafrost carbon emissions accelerated by abrupt thaw beneath lakes. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-05738-9

http://www.nature.com/articles/s41467-018-05738-9

Extract: "These finding demonstrate the need to incorporate abrupt thaw processes in earth system models for more comprehensive projection of the PCF this century."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2493 on: January 01, 2020, 04:38:50 AM »
The linked reference provides evidence that CMIP5 model projections 'have underestimated the cooling effect that aerosol particles have had on climate in recent decades"; which 'suggests that the models are not sensitive enough to increasing greenhouse gas concentrations in the atmosphere'.  In other words, this reference finds that the CMIP5 models (as a group) underestimate both TCR & ECS:

Trude Storelvmo et al. (29 August 2018), "Lethargic response to aerosol emissions in current climate models", Geophysical Research Letters, https://doi.org/10.1029/2018GL078298

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL078298

"Abstract
The global temperature trend observed over the last century is largely the result of two opposing effects – cooling from aerosol particles and greenhouse gas (GHG) warming. While the effect of increasing GHG concentrations on Earth's radiation budget is well‐constrained, that due to anthropogenic aerosols is not, partly due to a lack of observations. However, long‐term surface measurements of changes in downward solar radiation (SDSR), an often‐used proxy for aerosol radiative impact, are available worldwide over the last half‐century. We compare SDSR changes from ∼1,400 stations to those from the CMIP5 global climate simulations over the period 1961‐2005. The observed SDSR shows a strong early downward trend followed by a weaker trend‐reversal, broadly consistent with historical aerosol emissions. However, despite considerable changes to known aerosol emissions over time, the models show negligible SDSR trends, revealing a lethargic response to aerosol emissions, and casting doubt on the accuracy of their future climate projections.

Plain Language Summary
Observations of incoming solar radiation, as measured at approximately 1400 surface stations worldwide, show a strong downward trend from the 1960s to the 1980s, followed by a weaker trend reversal thereafter. These trends are thought to be due to changes in the amount of aerosol particles in the atmosphere, and we find support for that here in the temporal evolution of anthropogenic aerosol emissions. This is expected because aerosol particles reflect and/or absorb sunlight back to space, and have a net cooling effect on Earth's climate. However, we find that the current generation of climate models simulate negligible solar radiation trends over the last half‐century, suggesting that they have underestimated the cooling effect that aerosol particles have had on climate in recent decades. Despite this, climate models tend to reproduce surface air temperature over the time period in question reasonably well. This, in turn, suggests that the models are not sensitive enough to increasing greenhouse gas concentrations in the atmosphere, with important implications for their ability to simulate future climate."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2494 on: January 01, 2020, 04:40:18 AM »
The linked reference provide evidence that the ocean's 'biological carbon pump' is likely a positive feedback on climate change.  This likely positive feedback is underestimated in AR5 vintage consensus science climate models:

F.Boscolo-Galazz et al. (30 August 2018), "Temperature dependency of metabolic rates in the upper ocean: A positive feedback to global climate change?", Global and Planetary Change, https://doi.org/10.1016/j.gloplacha.2018.08.017

https://www.sciencedirect.com/science/article/pii/S0921818118301905

Abstract: "The temperature of seawater can affect marine plankton in various ways, including by affecting rates of metabolic processes. This can change the way carbon and nutrients are fixed and recycled and hence the chemical and biological profile of the water column. A variety of feedbacks on global climate are possible, especially by altering patterns of uptake and return of carbon dioxide to the atmosphere. Here we summarize and synthesize recent studies in the field of ecology, oceanography and ocean carbon cycling pertaining to possible feedbacks involving metabolic processes. By altering the rates of cellular growth and respiration, temperature-dependency may affect nutrient uptake and food demand in plankton and ultimately the equilibrium of pelagic food webs, with cascade effects on the flux of organic carbon between the upper and inner ocean (the “biological carbon pump”) and the global carbon cycle. Insights from modern ecology can be applied to investigate how temperature-dependent changes in ocean biogeochemical cycling over thousands to millions of years may have shaped the long-term evolution of Earth's climate and life. Investigating temperature-dependency over geological time scales, including through globally warm and cold climate states, can help to identify processes that are relevant for a variety of future scenarios."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2495 on: January 01, 2020, 04:41:55 AM »
The linked reference confirms both that the low end value of climate sensitivity given in AR5 is too low and that climate sensitivity increases with continued warming on the century scale:

Philip Goodwin (10 September 2018), "On the time evolution of climate sensitivity and future warming", Earth's Future, https://doi.org/10.1029/2018EF000889

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018EF000889

Abstract
The Earth's climate sensitivity to radiative forcing remains a key source of uncertainty in future warming projections. There is a growing realisation in recent literature that research must go beyond an equilibrium and CO2‐only viewpoint, towards considering how climate sensitivity will evolve over time in response to anthropogenic and natural radiative forcing from multiple sources. Here, the transient behaviour of climate sensitivity is explored using a modified energy balance model, in which multiple climate feedbacks evolve independently over time to multiple sources of radiative forcing, combined with constraints from observations and from the Climate Model Intercomparison Project phase 5 (CMIP5). First, a large initial ensemble of 107 simulations is generated, with a distribution of climate feedback strengths from sub‐annual to 102 year timescales constrained by the CMIP5 ensemble; including the Planck feedback, the combined water‐vapour lapse‐rate feedback, snow and sea‐ice albedo feedback, fast cloud feedbacks, and the cloud response to SST‐adjustment feedback. These 107 simulations are then tested against observational metrics representing decadal trends in warming, heat and carbon uptake, leaving only 4.6×103 history‐matched simulations consistent with both the CMIP5 ensemble and historical observations. The results reveal an annual‐timescale climate sensitivity of 2.1 °C (ranging from 1.6 to 2.8 °C at 95% uncertainty), rising to 2.9 °C (from 1.9 to 4.6 °C) on century timescales. These findings provide a link between lower estimates of climate sensitivity, based on the current transient state of the climate system, and higher estimates based on long‐term behaviour of complex models and palaeoclimate evidence.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2496 on: January 01, 2020, 04:54:04 AM »
The linked reference calculates a 15% chance that the AMOC could temporarily shutdown within the next 100-years; however, the reference does not consider the influence of a potential collapse of the WAIS on this probability:

Castellana, D., Baars, S., Wubs, F.W. et al. Transition Probabilities of Noise-induced Transitions of the Atlantic Ocean Circulation. Sci Rep 9, 20284 (2019) doi:10.1038/s41598-019-56435-6

https://www.nature.com/articles/s41598-019-56435-6

Abstract: "The Atlantic Meridional Overturning Circulation (AMOC) is considered to be a tipping element of the climate system. As it cannot be excluded that the AMOC is in a multiple regime, transitions can occur due to atmospheric noise between the present-day state and a weaker AMOC state. For the first time, we here determine estimates of the transition probability of noise-induced transitions of the AMOC, within a certain time period, using a methodology from large deviation theory. We find that there are two types of transitions, with a partial or full collapse of the AMOC, having different transition probabilities. For the present-day state, we estimate the transition probability of the partial collapse over the next 100 years to be about 15%, with a high sensitivity of this probability to the surface freshwater noise amplitude."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Tom_Mazanec

  • Young ice
  • Posts: 4196
  • Earth will survive AGW...but will Homo sapiens?
    • View Profile
    • Planet Mazanec
  • Liked: 658
  • Likes Given: 510
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2497 on: January 01, 2020, 06:13:55 AM »
Ken Feldman:
AbruptSLR's links almost always (since I've been following them) are about the likelihood that we have underestimated feedbacks and ECS. They are not that based on future emissions. Even if we follow a declining FF usage curve, we are still likely to see greater warming than we currently expect.
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

AbruptSLR

  • Multi-year ice
  • Posts: 19153
    • View Profile
  • Liked: 2124
  • Likes Given: 263
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2498 on: January 01, 2020, 08:36:47 AM »
The linked reference examines different MISI failure scenarios for the Thwaites Glacier and finds that "… uncertainty solely related to internal climate variability can be a large fraction of the total ice loss expected from Thwaites Glacier. We conclude that internal climate variability alone can be responsible for significant uncertainty in projections of sea-level rise and that large ensembles are a necessary tool for quantifying the upper bounds of this uncertainty."  If one were to consider MICI failure scenarios the skewed uncertainty would undoubtedly be greater still:

Robel et al. (2019), "Marine ice sheet instability amplifies and skews uncertainty in projections of future sea-level rise", PNAS, 6 (30), 14887-14892, https://doi.org/10.1073/pnas.1904822116

https://www.pnas.org/node/874167.full
&
https://www.pnas.org/content/pnas/116/30/14887.full.pdf

Significance
The potential for collapse of the Antarctic ice sheet remains the largest single source of uncertainty in projections of future sea-level rise. This uncertainty comes from an imperfect understanding of ice sheet processes and the internal variability of climate forcing of ice sheets. Using a mathematical technique from statistical physics and large ensembles of state-of-the-art ice sheet simulations, we show that collapse of ice sheets widens the range of possible scenarios for future sea-level rise. We also find that the collapse of marine ice sheets makes worst-case scenarios of rapid sea-level rise more likely in future projections.

Abstract
Sea-level rise may accelerate significantly if marine ice sheets become unstable. If such instability occurs, there would be considerable uncertainty in future sea-level rise projections due to imperfectly modeled ice sheet processes and unpredictable climate variability. In this study, we use mathematical and computational approaches to identify the ice sheet processes that drive uncertainty in sea-level projections. Using stochastic perturbation theory from statistical physics as a tool, we show mathematically that the marine ice sheet instability greatly amplifies and skews uncertainty in sea-level projections with worst-case scenarios of rapid sea-level rise being more likely than best-case scenarios of slower sea-level rise. We also perform large ensemble simulations with a state-of-the-art ice sheet model of Thwaites Glacier, a marine-terminating glacier in West Antarctica that is thought to be unstable. These ensemble simulations indicate that the uncertainty solely related to internal climate variability can be a large fraction of the total ice loss expected from Thwaites Glacier. We conclude that internal climate variability alone can be responsible for significant uncertainty in projections of sea-level rise and that large ensembles are a necessary tool for quantifying the upper bounds of this uncertainty.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

JD

  • New ice
  • Posts: 10
    • View Profile
  • Liked: 7
  • Likes Given: 18
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2499 on: January 01, 2020, 10:09:41 AM »
Ken Feldman:  Like Tom, I see ASLR's posts as trying to understand what possibility we have of climate change proving far worse than generally accepted.  Clearly that does not mean it definitely will be far worse, but it does show that there is more than zero chance of it being far worse.

Your charts of human CO2 emissions based on stated policies suggest that the emissions will flatten, but will remain at roughly the current levels, i.e. CO2 will increase linearly. 

As a simple thought experiment of what this might imply for the future climate, I looked at the CO2e data from NOAA https://esrl.noaa.gov/gmd/aggi/aggi.html.  Pre-industrial was 275 and CO2e was 496 at the end of 2018.  Taking the values for the last 10 years of CO2e and projecting them to 2100 with a simple linear projection I get a value of 778 for CO2e (assuming CO2e increases linearly if CO2 increases linearly)

778 is 1.5 doublings above pre-industrial.  At 3C per doubling this gives 4.5C temperature rise and clearly into the catastrophic territory for the impact on human civilisation.  So based on your charts I would say catastrophic climate change looks possible and even likely.

ASLR's posts have documented lots of issues that indicated this 4.5C projection may be too low. 
  • Climate sensitivity may be 5C per doubling, which would give a 7.5C temperature rise, way into catastrophic territory. 
  • CO2e in the atmosphere may increase at a faster rate than recently, even with the same CO2e emissions from humans (reduced %absorbed by the oceans, increased CO2e from permafrost melting, etc.) so the simple linear projection may be too low, again moving us way into catastrophic climate change territory.

So I can't see the point of worrying whether RCP8.5 is feasible or not, when it is clear that we have the potential to cause catastrophic climate change with our current policy.

ASLR: Thank you for all the hard work you do!