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Telihod

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2050 on: December 01, 2019, 09:24:54 AM »
Is there an article about the possible effect of the sulphur reduction in shipping fuel coming next January? (My rough unscientific estimate that I did in 5 minutes is, that the SO2 reduction will be greater than the annual emissions of the whole of South America, but I would like to read about it from a proper source.)

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2051 on: December 01, 2019, 04:43:25 PM »
The risk of changes in climate state has been subject to scientific discussion/argument for a longtime.  In this regard, the upper panel of the first image illustrates how climate system response with a potential threshold (such as the WAIS ice mass loss or the change of the atmosphere into an equable pattern) can cause uncertainty of actual risk of consequences such as SLR; the lower panel of the first image illustrates how uncertainty associated with modeling and climate change forcing parameters, can result in considerably different projections of consequence (e.g. Expert A may incorrectly assume that the formation and degradation of the WAIS are merely functions of thermal considerations and thus are reversible; while Expert B may realize that due to positive feedback factors (such as MICI-type of failure) that the WAIS forms more slowly than it degrades, and that once the WAIS reaches a tipping point, it may degrade relatively quickly as compared to Expert A's opinion).

The second makes the same point as the first image, except that it adds time as a third ordinate in order to illustrate how climate states with potential thresholds can change with time with positive radiative forcing (note in this image one can effectively replace the terms of the Kyoto Accord with the Paris Agreement, as little has been achieved from decades of UN negotiations).  Next, I provide the third image as a follow-on to the second image in order to indicate that once the initial climate state is close to the potential threshold then a mere perturbation (such as an intense El Nino event, or a surge of icebergs from the Jakobshavn Glacier) can push the climate past the threshold into a new 'hothouse' climate state.

Regarding the height of the potential barrier between climate states, I note that in addition to inherent uncertainties about the sensitivities of various Earth Systems, Lenton et al. (2019) indicated that it was previously assumed that this barrier would be effective until at least 5C, and now many experts believe that this barrier could become ineffective at a GMSTA of closer to 2C.  If the previously linked discussion by Lenton et al. (2019) was not sufficient, I note here that pushing our climate state up the side of this barrier at a high rate of forcing can reduce the height of the barrier by both:

a. Given various Earth Systems insufficient time to dissipate surplus potential energy, such as giving the topical sea surface temperature (SST) insufficient time to dissipate heat into the deeper ocean thus potentially increasing topical ocean SST by 5C (from today); which would flip the atmosphere into an equable pattern, or giving ice-cliffs for key marine glaciers sufficient time to flow/creep thus potentially resulting in an abrupt MICI-type of glacial/ice sheet collapse.

b. A cascade of Earth System tipping points might be interrupted at slow rates of climate forcing, while climate momentum may be sufficient to continue a cascade of tipping points once it is initiated, say by a climate system perturbation.


Caption for first image: 'Illustrations of the Relationship of Inherent Systemic Uncertainty and Climate System Response (upper panel), and Inherent Systemic Uncertainty in Modeling and Forcing Parameters (lower panel), from Keller 2011'

Caption for the second image: 'Representation of Potential Pathways of Potential Climate Equilibrium State vs Global Warming with Time. Illustrated Pathways Are for: A Business as Usual Scenario; The Original (pre-2011) Kyoto Protocol Scenario; and A Potential "Survival Pathway", from Wasdell 2010'
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2052 on: December 01, 2019, 05:52:13 PM »
As SO2 emissions both have a significant negative impact on human heath and as it is easy to reduce such emissions using existing technology than are associated GHG emissions (see the linked article about reducing SO2 emissions from shipping); it is reasonable to assume that the trend of increasing SO2 emissions will be curtailed sooner that will be GHG emissions.  While from a health point of view this is good news; however, from a climate change risk perspective it is bad news as SO2 emissions represent a negative radiative forcing:

Title: "Shipping sector gears itself for new emissions regulations"

https://www.dw.com/en/shipping-sector-gears-itself-for-new-emissions-regulations/a-50836212

Extract: "From January 1, 2020, ships will be required by the IMO to reduce SO2 emissions by more than 80%. The options for doing so vary, from installing sulphur-removing technology known as scrubbers to moving away from oil-based fuel entirely. What doesn't vary all that much is the cost — complying with the new rules will be expensive.

This forthcoming measure only deals with sulphur though. Measures against carbon pollution, altogether harder to conceive and enforce, are yet to come.

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

Tom_Mazanec

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2053 on: December 01, 2019, 06:40:33 PM »
Yes, AbruptSLR. IIRC sulphur and carbon particulates were so high in the pre-Earth Day days that, from the Thirties to the Seventies global temperature actually declined slightly.
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2054 on: December 01, 2019, 06:44:08 PM »
The linked 2-year old Scribbler article highlights the fact that current climate model projections do not include potential future methane emissions associated with marine glacier/ice sheet retreat.  Society may soon regret such omissions.

"New Study: Ice Sheet Retreat Led to Rapid Methane Hydrate Release at End of Last Ice Age"

https://robertscribbler.com/2017/06/07/new-study-ice-sheet-retreat-led-to-rapid-methane-hydrate-release-at-end-of-last-ice-age/

Extract: "At the end of the last ice age, a warming world released a portion of its carbon stores into the atmosphere. The result was, ultimately, an increase in atmospheric CO2 by around 100 parts per million and in increase in atmospheric methane by around 300 parts per billion.
This increase in greenhouse gasses was a direct response to the Earth warming by approximately 4 degrees Celsius over the course of about 10,000 years. Under a present human-forced warming that is currently 1.2 C above late 19th Century averages and that is predicted to reach between 3.3 and 7 C warming this Century if fossil fuel burning continues, it is important to consider what additional carbon forcing the Earth System will produce under such an extreme and short-term temperature departure.

Researchers also indicated that places presently locked in surface ice — like Greenland and Antarctica — could generate further methane blow out risk as ice sheets melt, withdraw and remove pressure from the methane deposits beneath them.

These are important findings due to the fact that paleoclimate evidence of past large-scale hydrate release provides a study-identified mechanism for how permafrost hydrates and gas deposits are being liberated due to present warming, how such warming may increase their rate of liberation in the future, and how ice sheet withdrawal could contribute to this hydrate liberation trend. What remains highly uncertain is the ultimate volume of hydrate response to a given level of warming over a given period and how significantly such releases would contribute to the already very considerable heat forcing provided by human emissions. That said, the new study does add to serious concerns regarding the potential for future warming and greenhouse gas levels — which will tend to be higher than present model studies indicate due to generally not accounting for these kinds of Earth System carbon feedbacks."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2055 on: December 01, 2019, 06:46:02 PM »
The linked article suggests a future feedback between biomass fires in the Southern Hemisphere and decreasing albedo in Antarctica, with continued global warming.  To the best of my knowledge such a feedback is currently not included in any CMIP5, or in preliminary CMIP6, projections:

M. M. Arienzo et. al. (11 June 2017), "Holocene black carbon in Antarctica paralleled Southern Hemisphere climate", Journal of Geophysical Research -  Atmospheres; DOI: 10.1002/2017JD026599

http://onlinelibrary.wiley.com/doi/10.1002/2017JD026599/abstract?utm_content=bufferad755&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Black carbon (BC) and other biomass-burning (BB) aerosols are critical components of climate forcing but quantification, predictive climate modeling, and policy decisions have been hampered by limited understanding of the climate drivers of BB and by the lack of long-term records. Prior modeling studies suggested that increased Northern Hemisphere anthropogenic BC emissions increased recent temperatures and regional precipitation, including a northward shift in the Inter-Tropical Convergence Zone (ITCZ). Two Antarctic ice cores were analyzed for BC and the longest record shows that the highest BC deposition during the Holocene occurred ~8-6k years before present in a period of relatively high austral burning season and low growing season insolation. Atmospheric transport modeling suggests South America (SA) as the dominant source of modern Antarctic BC and, consistent with the ice-core record, climate model experiments using mid-Holocene and preindustrial insolation simulate comparable increases in carbon loss due to fires in SA during the mid-Holocene. SA climate proxies document a northward shifted ITCZ and weakened SA Summer Monsoon (SASM) during this period, with associated impacts on hydroclimate and burning. A second Antarctic ice core spanning the last 2.5k years documents similar linkages between hydroclimate and BC, with the lowest deposition during the Little Ice Age characterized by a southerly shifted ITCZ and strengthened SASM. These new results indicate that insolation-driven changes in SA hydroclimate and BB, likely linked to the position of the ITCZ, modulated Antarctic BC deposition during most of the Holocene and suggests connections and feedbacks between future BC emissions and hydroclimate."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2056 on: December 01, 2019, 06:53:36 PM »
'Ghost forests are most obvious on the Eastern US Coastal areas due to the Gulf Streams influence on regional SLR.  However, as more & more ice sheet mass loss occurs, this problem will become more common along coasts worldwide; which will reduce the effectiveness an important carbon sink:

Title: "“Ghost forests”: What they are and why they’re becoming more common"

http://www.cbsnews.com/news/ghost-forests-what-they-are-why-theyre-becoming-more-common/

Extract: "They're called "ghost forests" - dead trees along vast swaths of coastline invaded by rising seas, something scientists call one of the most visible markers of climate change.
The process has occurred naturally for thousands of years, but has accelerated in recent decades as polar ice melts and raises sea levels, scientists say, pushing salt water farther inland and killing trees in what used to be thriving freshwater plains.

Efforts are underway worldwide to determine exactly how quickly the creation of ghost forests is increasing. But scientists agree the startling sight of dead trees in once-healthy areas is an easy-to-grasp example of the consequences of climate change.

"I think ghost forests are the most obvious indicator of climate change anywhere on the Eastern coast of the U.S.," said Matthew Kirwan, a professor at Virginia Institute of Marine Science who is studying ghost forests in his state and Maryland. "It was dry, usable land 50 years ago; now it's marshes with dead stumps and dead trees.""
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2057 on: December 01, 2019, 06:56:37 PM »
The linked reference discusses state of the at surface temperature at the West Antarctic Divide for the past ~ 40,000 years (see image bottom panel).  Findings indicate that current climate models are challenged to hind cast the observed findings and that models with low climate sensitivities can be eliminated from consideration.  Furthermore, they find that an Antarctic Amplification of 2 to 3 time GMSTA.  These findings do not bode well for the stability of the WAIS with continued global warming:

Kurt M. Cuffey, Gary D. Clow, Eric J. Steig, Christo Buizert, T. J. Fudge, Michelle Koutnik, Edwin D. Waddington, Richard B. Alley, and Jeffrey P. Severinghaus (2016), "Deglacial temperature history of West Antarctica", PNAS, vol. 113 no. 50, 14249–14254, doi: 10.1073/pnas.1609132113

http://www.pnas.org/content/113/50/14249

Abstract: "The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth’s climate responds to various forcings, including a rise in atmospheric CO2. This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes’ sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was 11.3±1.8 ∘  11.3±1.8∘ C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted."

Extract: "Of greatest immediate interest, however, is our demonstration that the global deglacial temperature change was amplified by a factor of 2–3 in the Antarctic, that Antarctic warming was largely achieved by 15 ka in coherence with records from Southern Hemisphere mountain ranges, and that climate models of the deglaciation perform well on average, but that the ones with lowest sensitivity can be discounted. The early warming of the Southern Hemisphere, which our study helps to quantify, arose from combined effects of reduced northward oceanic heat transport, increased insolation, and increasing atmospheric CO2. Quantitative simulation of this phenomenon could provide an illuminating challenge for model studies."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2058 on: December 01, 2019, 06:59:01 PM »
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 warm SST region 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.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2059 on: December 01, 2019, 07:03:22 PM »
We would all do well to remember that periods of intense El Nino events typically lead to drought conditions in the Amazon as indicated by the findings of the first linked reference; which is not good news as it is generally accepted that increasing global warming will lead to more frequent intense El Nino events:

Amir Erfanian, Guiling Wang, and Lori Fomenko (2017), "Unprecedented drought over tropical South America in 2016: significantly under-predicted by tropical SST", Sci Rep.; 7: 5811, doi:  10.1038/s41598-017-05373-2

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5517600/

Abstract: "Tropical and sub-tropical South America are highly susceptible to extreme droughts. Recent events include two droughts (2005 and 2010) exceeding the 100-year return value in the Amazon and recurrent extreme droughts in the Nordeste region, with profound eco-hydrological and socioeconomic impacts. In 2015–2016, both regions were hit by another drought. Here, we show that the severity of the 2015–2016 drought ("2016 drought" hereafter) is unprecedented based on multiple precipitation products (since 1900), satellite-derived data on terrestrial water storage (since 2002) and two vegetation indices (since 2004). The ecohydrological consequences from the 2016 drought are more severe and extensive than the 2005 and 2010 droughts. Empirical relationships between rainfall and sea surface temperatures (SSTs) over the tropical Pacific and Atlantic are used to assess the role of tropical oceanic variability in the observed precipitation anomalies. Our results indicate that warmer-than-usual SSTs in the Tropical Pacific (including El Niño events) and Atlantic were the main drivers of extreme droughts in South America, but are unable to explain the severity of the 2016 observed rainfall deficits for a substantial portion of the Amazonia and Nordeste regions. This strongly suggests potential contribution of non-oceanic factors (e.g., land cover change and CO2-induced warming) to the 2016 drought."

See also:

Title: "Study finds human influence in the Amazon's third 1-in-100 year drought since 2005"

https://www.skepticalscience.com/human-influence-amazon-droughts.html

Extract: "The authors also found that the water temperatures alone could not adequately explain the size and severity of the 2015-2016 drought. This suggests that there are other factors involved as well. To be clear, the authors found that the relationship between water temperatures and drought worked well for prior droughts (the 2005 and 2010 droughts as well as 1983 and 1998 droughts, also El Niño years) but fell apart in 2015-2016. That is, using the relationship, the predicted 2015-2016 drought should not have been nearly as severe or as large as it was. The paper also reports that the 2015-2016 drought clearly exceeded that of the 100-year events in 2005 and 2010. So, in approximately one decade, this zone has had three 100-year events. Quite astonishing.

So why was SST unable to explain the 2015-2016 drought, like it had for past events? Part of it has to do with land-use changes. That is, human changes to the land surface such as deforestation. Another part is related to warming from greenhouse gases. It is clear that land-use changes can affect drought. As farmers deforest, for instance, they convert woodlands and forests into agricultural land. This changes not only the darkness (reflectivity) of the land, but it also impacts the transfer of water to and from the atmosphere (evapotranspiration).

One might ask how warming affects droughts. As air temperatures increase, air is able to evaporate water more rapidly and dry out surfaces. At the same time, air can contain more water vapor so that when rain does occur, it is more often in heavy downpours. These two changes underlie what is referred to as an accelerated hydrological cycle. Simply put, man-made warming is accelerating the movement of water through the ecosystem, which can cause drought even if precipitation does not decrease. Warming also causes changes in the large-scale patterns of air motion (atmospheric circulation) that reduces rainfall in this region."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2060 on: December 01, 2019, 07:06:24 PM »
The linked reference finds that the pH dependence of DMS results in a positive feedback for global warming and that the associated warming of Antarctica occurs at twice the rate of the global mean.  This is not good news for WAIS stability:

Schwinger, J., Tjiputra, J., Goris, N., Six, K. D., Kirkevåg, A., Seland, Ø., Heinze, C., and Ilyina, T.: Amplification of global warming through pH dependence of DMS production simulated with a fully coupled Earth system model, Biogeosciences, 14, 3633-3648, https://doi.org/10.5194/bg-14-3633-2017, 2017.

https://www.biogeosciences.net/14/3633/2017/?utm_content=bufferbbbbb&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "We estimate the additional transient surface warming ΔTs caused by a potential reduction of marine dimethyl sulfide (DMS) production due to ocean acidification under the high-emission scenario RCP8.5 until the year 2200. Since we use a fully coupled Earth system model, our results include a range of feedbacks, such as the response of marine DMS production to the additional changes in temperature and sea ice cover. Our results are broadly consistent with the findings of a previous study that employed an offline model set-up. Assuming a medium (strong) sensitivity of DMS production to pH, we find an additional transient global warming of 0.30 K (0.47 K) towards the end of the 22nd century when DMS emissions are reduced by 7.3 Tg S yr−1 or 31 % (11.5 Tg S yr−1 or 48 %). The main mechanism behind the additional warming is a reduction of cloud albedo, but a change in shortwave radiative fluxes under clear-sky conditions due to reduced sulfate aerosol load also contributes significantly. We find an approximately linear relationship between reduction of DMS emissions and changes in top of the atmosphere radiative fluxes as well as changes in surface temperature for the range of DMS emissions considered here. For example, global average Ts changes by −0. 041 K per 1 Tg S yr−1 change in sea–air DMS fluxes. The additional warming in our model has a pronounced asymmetry between northern and southern high latitudes. It is largest over the Antarctic continent, where the additional temperature increase of 0.56 K (0.89 K) is almost twice the global average. We find that feedbacks are small on the global scale due to opposing regional contributions. The most pronounced feedback is found for the Southern Ocean, where we estimate that the additional climate change enhances sea–air DMS fluxes by about 9 % (15 %), which counteracts the reduction due to ocean acidification."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2061 on: December 01, 2019, 07:08:08 PM »
Currently, management models do not adequately account for probable increases eutrophication associated with run-off of excessive nutrients/nitrogen due to changes in precipitation with continued global warming.  This can act as a positive feedback mechanism for more global warming:

E. Sinha, A. M. Michalak & V. Balaji (2017), "Eutrophication will increase during the 21st century as a result of precipitation changes", Science, Vol. 357, Issue 6349, pp. 405-408, DOI: 10.1126/science.aan2409

http://science.sciencemag.org/content/357/6349/405

Abstract: "Eutrophication, or excessive nutrient enrichment, threatens water resources across the globe. We show that climate change–induced precipitation changes alone will substantially increase (19 ± 14%) riverine total nitrogen loading within the continental United States by the end of the century for the “business-as-usual” scenario. The impacts, driven by projected increases in both total and extreme precipitation, will be especially strong for the Northeast and the corn belt of the United States. Offsetting this increase would require a 33 ± 24% reduction in nitrogen inputs, representing a massive management challenge. Globally, changes in precipitation are especially likely to also exacerbate eutrophication in India, China, and Southeast Asia. It is therefore imperative that water quality management strategies account for the impact of projected future changes in precipitation on nitrogen loading."

See also: "The Nitrogen Problem: Why Global Warming Is Making It Worse"

http://e360.yale.edu/features/the-nitrogen-problem-why-global-warming-is-making-it-worse

Extract: "New research shows that increases in rainfall and extreme weather because of climate change will increase the amount of nitrogen polluting rivers and other waterways. The findings underscore the urgency of reforming agriculture to dramatically reduce the use of nitrogen fertilizers."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2062 on: December 01, 2019, 07:10:17 PM »
The linked reference determines the paleoclimate sensitivity during the Middle Eocene at a latitude of 64 degrees 48 minutes in Canada (see the first image), and finds a regional climate sensitivity of about 13C.  The second image illustrates that these findings indicate exceptionally high values of Arctic Amplification during this period as the atmospheric carbon dioxide concentrations were found to be only about 490 ppm.  While the mean global surface temperature was warmer during the Middle Eocene than today, we are warming at a much faster rate and C02-equiv is already well about 490 ppm.  This does not bode well for our collective future:

Alexander P. Wolfe, Alberto V. Reyes, Dana L. Royer, David R. Greenwood, Gabriela Doria, Mary H. Gagen, Peter A. Siver and John A. Westgate (May 2017), "Middle Eocene CO2 and climate reconstructed from the sediment fill of a subarctic kimberlite maar", GEOLOGY, July 2017; v. 45; no. 7; p. 619–622, doi:10.1130/G39002.1


https://gsw.silverchair-cdn.com/gsw/Content_public/Journal/geology/45/7/10.1130_G39002.1/1/619.pdf?Expires=1502222555&Signature=bqBU8Y3KgwV619Rh98~HEPqPp~aWdJ3w9x893T75q0T5Bn70XB~7Xvjub8K7QrFGN5OhK1RYvai3Aw5yfCYLSjKnKMt7KIMCoZnbo8drd9wtDSqrfEqLJJYFd6X7WWR~nBW9BCmhI0t2QOV2QqS7xkvQPDLc~saDe8e9-V8rrwXRI~WR-KsTvbGe2wz~XUmEU3c-lt~TD1TLajAj4Cb5EVeLNGjtF~0pt2fdKtvHMbl8C9~r5TimyGysbu5vExwPrbZvpLvfjxzipB-l5fiD7QH9qCslsthuwWOPIGGCUquL0tI6lMHQZXugcX5ix1ge4Uj7Ed6RQVvB07liZCi7mA__&Key-Pair-Id=APKAIUCZBIA4LVPAVW3Q
&
http://www.geosociety.org/datarepository/2017/2017202.pdf

Abstract: "Eocene paleoclimate reconstructions are rarely accompanied by parallel estimates of CO2 from the same locality, complicating assessment of the equilibrium climate response to elevated CO2. We reconstruct temperature, precipitation, and CO2 from latest middle Eocene (ca. 38 Ma) terrestrial sediments in the post eruptive sediment fill of the Giraffe kimberlite in subarctic Canada. Mutual climatic range and oxygen isotope analyses of botanical fossils reveal a humid temperate forest ecosystem with mean annual temperatures (MATs) more than 17 °C warmer than present and mean annual precipitation ~4× present. Metasequoia stomatal indices and gas-exchange modeling produce median CO2 concentrations of ~630 and ~430 ppm, respectively, with a combined median estimate of ~490 ppm. Reconstructed MATs are more than 6 °C warmer than those produced by Eocene climate models forced at 560 ppm CO2. Estimates of regional climate sensitivity, expressed as ΔMAT per CO2 doubling above preindustrial levels, converge on a value of ~13 °C, underscoring the capacity for exceptional polar amplification of warming and hydrological intensification under modest CO2 concentrations once both fast and slow feedbacks become expressed."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2063 on: December 01, 2019, 07:11:45 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.  This is not good news:

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."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2064 on: December 01, 2019, 10:58:04 PM »
This linked article makes some of the points that I have been making using different terms:

Title: "Scientist's theory of climate's Titanic moment the 'tip of a mathematical iceberg'"

https://www.theguardian.com/environment/2019/dec/01/scientists-theory-of-climates-titanic-moment-the-tip-of-a-mathematical-iceberg

Extract: "Formula for climate emergency shows if ‘reaction time is longer than intervention time left’ then ‘we have lost control
...
“There are a range of these intervention times left,” Steffen says. “How long do we have before [the Greenland ice sheet] goes? Maybe we have 20 to 25 years and then we might be committed to losing Greenland.

“But the time we have left to intervene to stabilise coral reefs, for example, is a lot less than 30 years.

“Our reaction time has to be fast and to decarbonise by 2050 we have to really move now. That’s the point of [Schellnhuber’s] maths.

“To err on the side of danger is a stupid thing to do.”"
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2065 on: December 02, 2019, 12:38:59 AM »
“There are a range of these intervention times left,” Steffen says. “How long do we have before [the Greenland ice sheet] goes? Maybe we have 20 to 25 years and then we might be committed to losing Greenland.
Yet another dose of Hopium.

I cannot see how any change in behavior now would affect the fate of the Greenland glaciers. The ice thickness is decreasing now, temperatures will continue to rise even in the incredible scenario that the burning of fossil fuels would stop tomorrow.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2066 on: December 02, 2019, 01:11:11 AM »
The linked information confirms that the rate of GMSTA increase per decade is accelerating:

Title: "September Global Temperature Change"

https://www.co2.earth/global-warming-update

Extract: "Overall, the global annual temperature has increased at an average rate of 0.07°C (0.13°F) per decade since 1880 and at an average rate of 0.17°C (0.31°F) per decade since 1970.""

&

O. Hoegh-Guldberg et al. (20 Sep 2019), "The human imperative of stabilizing global climate change at 1.5°C", Science, Vol. 365, Issue 6459, eaaw6974, DOI: 10.1126/science.aaw6974

https://science.sciencemag.org/content/365/6459/eaaw6974

Extract: "Climate change is one of the greatest challenges for humanity. Global mean surface temperature (GMST) is increasing at the rate of 0.2° ± 0.1°C per decade, reaching 1.0°C above the pre-industrial period (reference period 1850–1900) in 2017."

&

Per the linked image James Hansen speculated that in 2018 GMSTA was increasing at a rate of about 0.38C per decade and is almost certainly still increasing.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2067 on: December 02, 2019, 01:14:38 AM »
The linked article investigates the role of vegetation masking under RCP 8.5 on the boreal forest region of northern Eurasia and finds a factor of 1.5 increase in spring surface air temperature (SAT) above that considered by prior research like CMIP5.  This is a key factor indicating that Arctic Amplification (& ECS) will likely be higher than projected in AR5:

Manabu Abe et. al. (19 August 2017), "Vegetation masking effect on future warming and snow albedo feedback in a boreal forest region of northern Eurasia according to MIROC-ESM", Journal of Geophysical Research Atmospheres, DOI: 10.1002/2017JD026957 

http://onlinelibrary.wiley.com/doi/10.1002/2017JD026957/abstract?utm_content=bufferfa31f&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "The earth system model, MIROC-ESM, in which the leaf area index (LAI) is calculated interactively with an ecological land model, simulated future changes in the snow water equivalent under the scenario of global warming. Using MIROC-ESM, the effects of the snow albedo feedback (SAF) in a boreal forest region of northern Eurasia were examined under the possible climate future scenario RCP8.5. The simulated surface air temperature (SAT) in spring greatly increases across Siberia and the boreal forest region, whereas the snow cover decreases remarkably only in western Eurasia. The large increase in SAT across Siberia is attributed to strong SAF, which is caused by both the reduced snow-covered fraction and the reduced surface albedo of the snow-covered portion due to the vegetation masking effect in those grid cells. A comparison of the future changes with and without interactive LAI changes shows that, in Siberia, the vegetation masking effect increases the spring SAF by about two or three times and enhances the spring warming by approximately 1.5 times. This implies that increases in vegetation biomass in the future are a potential contributing factor to warming trends and that further research on the vegetation masking effect is needed for reliable future projection."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2068 on: December 02, 2019, 01:25:28 AM »
The linked reference uses data from CALIPSO to determine that GFDL's model in CMIP5 was underestimating longwave surface cloud feedback; which is to say that GFDL's CMIP5 model was underestimating ECS (by underestiming how net positve cloud feedback currently is):

Ryan J. Kramer  Alexander V. Matus  Brian J. Soden  Tristan S. L'Ecuyer (03 May 2019), "Observation‐Based Radiative Kernels From CloudSat/CALIPSO", JGR Atmospheres, https://doi.org/10.1029/2018JD029021

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JD029021

Abstract: "Radiative kernels describe the differential response of radiative fluxes to small perturbations in state variables and are widely used to quantify radiative feedbacks on the climate system. Radiative kernels have traditionally been generated using simulated data from a global climate model, typically sourced from the model's base climate. Consequently, these radiative kernels are subject to model bias from the climatological fields used to produce them. Here, we introduce the first observation‐based temperature, water vapor, and surface albedo radiative kernels, developed from CloudSat's fluxes and heating rates data set, 2B‐FLXHR‐LIDAR, which is supplemented with cloud information from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). We compare the radiative kernels to a previously published set generated from the Geophysical Fluid Dynamics Laboratory (GFDL) model and find general agreement in magnitude and structure. However, several key differences illustrate the sensitivity of radiative kernels to the distribution of clouds. The radiative kernels are used to quantify top‐of‐atmosphere and surface cloud feedbacks in an ensemble of global climate models from the Climate Model Intercomparison Project Phase 5, showing that biases in the GFDL low clouds likely cause the GFDL kernel to underestimate longwave surface cloud feedback. Since the CloudSat kernels are free of model bias in the base state, they will be ideal for future analysis of radiative feedbacks and forcing in both models and observations and for evaluating biases in model‐derived radiative kernels."

Edit, see also:

Graeme Stephens et. al. (2017), "CloudSat and CALIPSO within the A-Train: Ten years of actively observing the Earth system", BAMS, https://doi.org/10.1175/BAMS-D-16-0324.1

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-16-0324.1?utm_content=bufferebbb9&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer
or
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-16-0324.1

Abstract: "The more than 10 years of observations jointly collected by CloudSat and CALIPSO satellites has resulted in new ways of looking at aerosol, clouds, and precipitation and new discoveries about processes that connect them.

One of the most successful demonstrations of an integrated approach to observe Earth from multiple perspectives is the A-Train satellite constellation (e.g. Stephens et al., 2002). The science enabled by this constellation flourished with the introduction of the two active sensors carried by the NASA CloudSat and the NASA/CNES Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellites that were launched together on April 28th, 2006. These two missions have provided a 10-year demonstration of coordinated formation flying that made it possible to develop integrated products and that offered new insights on key atmospheric processes. The progress achieved over this decade of observations, summarized in this paper, clearly demonstrate the fundamental importance of the vertical structure of clouds and aerosol for understanding the influences of the larger scale atmospheric circulation on aerosol, the hydrological cycle, the cloud-scale physics and on the formation of the major storm systems of Earth. The research also underscored inherent ambiguities in radiance data in describing cloud properties and how these active systems have greatly enhanced passive observation. It is now clear that monitoring the vertical structure of clouds and aerosol is essential and a climate data record is now being constructed. These pioneering efforts are to be continued with EarthCARE mission planned for launch in 2019."
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― Leon C. Megginson

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2069 on: December 02, 2019, 01:29:35 AM »
As the Greenland Ice Sheet is currently losing ice mass faster than Antarctica, and will likely do so for next few decades, the linked reference is relevant over that timeframe.  And it finds that freshwater hosing into the North Atlantic in their model both increased surface warming in the Southern Hemisphere (which would help to destabilize the WAIS in the next few decades); and increased positive feedback related to clouds in the tropics.  Both of these findings agree with Hansen's ice-climate feedback mechanism:

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

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2070 on: December 02, 2019, 08:30:42 AM »
From wunderground.com for some perspective about current extremely high rate of change:
"It is preoccupation with possessions, more than anything else, that prevents us from living freely and nobly" - Bertrand Russell
   Simple: minimize your possessions and be free and kind    It's just a mindset.       Refugees welcome

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2071 on: December 02, 2019, 12:48:53 PM »
The linked reference indicates that the frequency of extreme El Nino events will increase rapidly with relatively minor increases in GMSTA; while the frequency of extreme La Nina events will increase relatively little between 1.5 and 2C GMSTA.  This indicates that climate sensitivity is higher than assumed in AR5:

Guojian Wang et al (2017), "Continued increase of extreme El Niño frequency long after 1.5 °C warming stabilization", Nature Climate Change  7, 568–572,  doi:10.1038/nclimate3351

http://www.nature.com/nclimate/journal/v7/n8/full/nclimate3351.html?foxtrotcallback=true

Abstract: "The Paris Agreement aims to constrain global mean temperature (GMT) increases to 2 °C above pre-industrial levels, with an aspirational target of 1.5 °C. However, the pathway to these targets and the impacts of a 1.5 °C and 2 °C warming on extreme El Niño and La Niña events—which severely influence weather patterns, agriculture, ecosystems, public health and economies—is little known. Here, by analysing climate models participating in the Climate Model Intercomparison Project’s Phase 5 (CMIP5) under a most likely emission scenario, we demonstrate that extreme El Niño frequency increases linearly with the GMT towards a doubling at 1.5 °C warming. This increasing frequency of extreme El Niño events continues for up to a century after GMT has stabilized, underpinned by an oceanic thermocline deepening that sustains faster warming in the eastern equatorial Pacific than the off-equatorial region. Ultimately, this implies a higher risk of extreme El Niño to future generations after GMT rise has halted. On the other hand, whereas previous research suggests extreme La Niña events may double in frequency under the 4.5 °C warming scenario, the results presented here indicate little to no change under 1.5 °C or 2 °C warming."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2072 on: December 02, 2019, 12:52:16 PM »
The linked reference indicates that a modeled doubling of atmospheric CO₂ concentrations 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."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2073 on: December 02, 2019, 05:01:41 PM »
Hausfather provides a summary (in the linked article & attached associated images) on the progress to-date from CMIP6:

Title: "CMIP6: the next generation of climate models explained"

https://www.carbonbrief.org/cmip6-the-next-generation-of-climate-models-explained

Extract: "CMIP6 will consist of the “runs” from around 100 distinct climate models being produced across 49 different modelling groups. The effort is already a year behind schedule, and it appears increasingly unlikely that all the CMIP6 models will be available in time for inclusion in the AR6.

While the results from only around 20 CMIP6 models have been published so far, it is already evident that a number of them have a notably higher climate sensitivity than models in CMIP5. This higher sensitivity contributes to projections of greater warming this century – around 0.4C to 0.9C warmer than similar scenarios run in CMIP5 – though these warming projections may change as more models become available. Researchers are still working to assess why sensitivity values appear higher in the latest generation of models.

CMIP6 models available to-date have tended to show notably higher climate sensitivity than CMIP5 models. While only 19 CMIP6 models currently have the runs needed to calculate ECS, around half of those have an ECS higher than the upper end of the likely range – 1.5C to 4.5C – provided in the IPCC AR5. More than a third have a higher sensitivity than any of the models featured in CMIP5. These include models from a number of very prominent modeling groups – like the Community Earth System Model 2 (CESM2) and the Met Office HadGEM3 model. The transient climate response – a measure of shorter-term warming associated with increasing CO2 – is also notably higher in many CMIP6 models.

It appears increasingly likely that not all CMIP6 runs will be available by the October 2020 deadline to be included in the final IPCC report, due to be published in April 2021. However, CMIP6 runs ready in time for the AR6 will still be used by researchers in the future.

While climate models output comprises thousands of different climate variables, a lot of attention is focused on global surface temperatures. Two different experiments that examine surface temperatures are of particular interest: the model surface temperature “hindcast” – where modellers simulate the period from 1850 through to the present day – and the projections of future warming under different emission scenarios.

CMIP6 is a huge modelling effort, substantially more ambitious than CMIP5. This has led to some delays, with CMIP6 currently running at least a year behind schedule. While the IPCC AR6 is currently being drafted, only a relatively limited set of models are available, and it seems unlikely that all CMIP6 runs will be completed in time for the final AR6 draft."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2074 on: December 02, 2019, 05:08:18 PM »
While the success of the recently implemented (January 2019) Kigali Amendment to the Montreal Protocol (see the first image) is still being monitored; I provide the following link to the 2018 assessment of ozone depletion, with the associated image indicating that even after the emission of ozone depleting substances (ODSs) are controlled, the damage to atmospheric ozone lasts for decades longer:

Title: "Scientific Assessment of Ozone Depletion: 2018"

https://www.esrl.noaa.gov/csd/assessments/ozone/2018/
https://www.esrl.noaa.gov/csd/assessments/ozone/2018/downloads/2018OzoneAssessment.pdf
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2075 on: December 02, 2019, 05:23:21 PM »
Hausfather also provides the attached image of different GMSTA trends from observation, CMIP5 and CMIP6 (thru Dec 2019):

Title: "CMIP6: the next generation of climate models explained"

https://www.carbonbrief.org/cmip6-the-next-generation-of-climate-models-explained

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2076 on: December 02, 2019, 05:31:40 PM »
The following is a linked reference examining the "Impact of West Antarctic Ice Shelf melting on the Southern Ocean Hydrograph".  Such information helps to better assess the rate of activation of several ice-climate feedback mechanisms:

Nakayama, Y., Timmermann, R., and Hellmer, H.: Impact of West Antarctic Ice Shelf melting on the Southern Ocean Hydrography, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-244, in review, 2019.

https://www.the-cryosphere-discuss.net/tc-2019-244/

Abstract. Previous studies show accelerations of West Antarctic glaciers, implying that basal melt rates of these glaciers were previously small and increased in the middle of the 20th century. This enhanced melting is a likely source of the observed Ross Sea (RS) freshening, but its long-term impact on the Southern Ocean hydrography has never been investigated. Here, we conduct coupled sea-ice/ice-shelf/ocean simulations with different levels of ice shelf melting from West Antarctic glaciers. Freshening of RS shelf and bottom water is simulated with enhanced West Antarctic ice shelf melting, while no significant changes in shelf water properties are simulated when West Antarctic ice shelf melting is small. We further show that the freshening caused by glacial meltwater from ice shelves in the Amundsen and Bellingshausen Seas propagates further downstream along the East Antarctic coast into the Weddell Sea. Our experiments also show the timescales for the freshening signal to reach other regions around the Antarctic continent. The freshening signal propagates onto the RS continental shelf within a year of model simulation, while it takes roughly 5–10 years and 10–15 years to propagate into the region off Cape Darnley and into the Weddell Sea, respectively. This advection of freshening signal} possibly modulates the properties of dense shelf water and impacts the production of Antarctic Bottom Water.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2077 on: December 02, 2019, 05:33:06 PM »
The linked reference confirms that AR5 significantly underestimated natural emissions of methane from wetlands worldwide, and recommends that policy makers shoulder the responsibility of taking corrective actions associated with AR5s shortcomings on this matter:

Zhen Zhang, et al (2017), "Emerging role of wetland methane emissions in driving 21st century climate change", PNAS, vol. 114 no. 36,  9647–9652, doi: 10.1073/pnas.1618765114

http://www.pnas.org/content/114/36/9647.short?utm_content=buffer165f2&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

"Significance
Conventional greenhouse gas mitigation policies ignore the role of global wetlands in emitting methane (CH4) from feedbacks associated with changing climate. Here we investigate wetland feedbacks and whether, and to what degree, wetlands will exceed anthropogenic 21st century CH4 emissions using an ensemble of climate projections and a biogeochemical methane model with dynamic wetland area and permafrost. Our results reveal an emerging contribution of global wetland CH4 emissions due to processes mainly related to the sensitivity of methane emissions to temperature and changing global wetland area. We highlight that climate-change and wetland CH4 feedbacks to radiative forcing are an important component of climate change and should be represented in policies aiming to mitigate global warming below 2°C."

Abstract: "Wetland methane (CH4) emissions are the largest natural source in the global CH4 budget, contributing to roughly one third of total natural and anthropogenic emissions. As the second most important anthropogenic greenhouse gas in the atmosphere after CO2, CH4 is strongly associated with climate feedbacks. However, due to the paucity of data, wetland CH4 feedbacks were not fully assessed in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The degree to which future expansion of wetlands and CH4 emissions will evolve and consequently drive climate feedbacks is thus a question of major concern. Here we present an ensemble estimate of wetland CH4 emissions driven by 38 general circulation models for the 21st century. We find that climate change-induced increases in boreal wetland extent and temperature-driven increases in tropical CH4 emissions will dominate anthropogenic CH4 emissions by 38 to 56% toward the end of the 21st century under the Representative Concentration Pathway (RCP2.6). Depending on scenarios, wetland CH4 feedbacks translate to an increase in additional global mean radiative forcing of 0.04 W·m−2 to 0.19 W·m−2 by the end of the 21st century. Under the “worst-case” RCP8.5 scenario, with no climate mitigation, boreal CH4 emissions are enhanced by 18.05 Tg to 41.69 Tg, due to thawing of inundated areas during the cold season (December to May) and rising temperature, while tropical CH4 emissions accelerate with a total increment of 48.36 Tg to 87.37 Tg by 2099. Our results suggest that climate mitigation policies must consider mitigation of wetland CH4 feedbacks to maintain average global warming below 2 °C."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2078 on: December 02, 2019, 05:36:01 PM »
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."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2079 on: December 02, 2019, 05:38:33 PM »
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."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2080 on: December 02, 2019, 06:16:47 PM »
Stratospheric ozone is under assault from anthropogenic emissions (primarily from East Asia) of several chlorine-containing very short-lived substances (Cl-VSLSs).  This was certainly not envisioned by AR5 & almost certainly is not considered in AR6:

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/?utm_content=bufferb397a&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

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.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2081 on: December 02, 2019, 06:19:40 PM »
The linked open access Harvard report about addressing deep and persistent uncertainty about climate sensitivity, concludes: "The massive uncertainties afflicting climate change should be a prod to policy action."  Unfortunately, decision makers tend to use uncertainties about climate sensitivity as an excuse to take limited action rather than as '… a prod to policy action'.

Gernot Wagner & Richard J. Zeckhauser, (27 October 2017) "Confronting Deep and Persistent Climate Uncertainty", JEL codes: Q54, D81.

http://gwagner.com/wp-content/uploads/Wagner-Zeckhauser-HKS-2017-Deep-and-persistent-climate-uncertainty.pdf

Abstract: "Deep-seated, persistent uncertainty is a pernicious feature of climate change. One key parameter, equilibrium climate sensitivity, has eluded almost all attempts to pin down more precisely than a ‘likely’ range that has stalled at 1.5–4.5°C for over thirty-five years.
The marginal damages due to temperature increase rise rapidly. Thus, uncertainty in climate sensitivity significantly raises the expected costs of climate change above what they would be if the temperature increases were known to be close to a mean value 3.0°C. The costs of this uncertainty are compounded given that the distribution of possible temperature changes is strongly skewed toward higher values."

Extract: "Climate change has been labelled as “the greatest market failure the world has ever seen” (Stern, 2006), and “the mother of all externalities” (Tol, 2009). Tol (2009) continues by calling it: “larger, more complex, and more uncertain than any other environmental problem.” It is. And the uncertainty itself has multiple dimensions.

Despite important advances in other areas of climate science, we have discovered new uncertainties that make us even less confident about the range of equilibrium climate sensitivity than we were before the latest IPCC report was published. Given the increasing marginal costs of global warming, greater uncertainty, other factors equal, raises the returns from curbing greenhouse gases. The massive uncertainties afflicting climate change should be a prod to policy action."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2082 on: December 02, 2019, 06:22:09 PM »
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.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2083 on: December 02, 2019, 06:47:20 PM »
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."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2084 on: December 02, 2019, 08:24:20 PM »
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:

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.

In recent years in Brazil, the illegal loggers realised that the satellite monitoring system had a resolution of "X" hectare sized pixels. So they started to log in "Y" sized areas, where "Y" is less than "X".

Eventually, higher resolution satellite images spotted this. But too late to save many thousands of hectares of old growth forest.

I suppose the new generation of high resolution satellites will show us the extent of under-recorded land-use change, though whether Governments will do anything about it is another story.   
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2085 on: December 02, 2019, 08:28:13 PM »
The linked reference discuss the possibility that concern over possible abrupt ice mass loss from the WAIS could be used to tip climate policy into effective action:

Marc Wiedermann, Ricarda Winkelmann, Jonathan F. Donges, Christina Eder, Jobst Heitzig, Alexia Katsanidou, and E. Keith Smith (2019), "Can Antarctica tip climate policy?", arXiv:1911.10063v1

https://arxiv.org/abs/1911.10063
https://arxiv.org/pdf/1911.10063v1.pdf

Abstract: Vital parts of the climate system such as the West Antarctic Ice Sheet are at risk even within the aspired aims of the Paris Agreement to limit global temperature rise to 1.5°-2°C. Implementing effective climate policies critically depends on cascading effects from (anticipated) climate impacts to emission reductions via social tipping.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2086 on: December 02, 2019, 08:32:03 PM »
The linked reference discusses the threat of very-short-lived-substances to the expected recovery time for stratospheric ozone; which is a very real concern.

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.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2087 on: December 02, 2019, 08:36:22 PM »
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."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2088 on: December 02, 2019, 08:37:30 PM »
It looks like future methane emissions from shallow lakes in agricultural areas have likely been underestimated due to the synergy between nutrients (from the agriculture) and future warming:

Title: "Combined nutrients and warming massively increase methane emissions from lakes"

https://phys.org/news/2018-01-combined-nutrients-massively-methane-emissions.html

Extract: "Shallow lakes in agricultural landscapes will emit significantly greater amounts of methane, mostly in the form of bubbles (ebullition) in a warmer world, which is a potential positive feedback mechanism to climate warming.

The present study used the longest-running freshwater mesocosm climate change experiment in the world to investigate how warming and eutrophication might interact to change methane ebullition in the future.
The results here were striking as they showed that the combination of increased nutrient loading and warming had a synergistic effect on the ebullition of methane. In the absence of nutrient enrichment, warming alone increased annual methane ebullition by around 50 percent and its relative contribution to total methane emission rose from about 50 percent to 75 percent.
In stark contrast, when nutrient levels were high, warming increased total methane emission by at least six-fold, and in some cases, 17-fold, and the proportion of ebullition increased to 95 percent of total annual methane flux."

See also:

Thomas A. Davidson et al, Synergy between nutrients and warming enhances methane ebullition from experimental lakes, Nature Climate Change (2018). DOI: 10.1038/s41558-017-0063-z
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2089 on: December 02, 2019, 09:38:22 PM »
One for you, AbruptSLR.

https://www.bbc.co.uk/news/science-environment-50625396
Climate change: Study underpins key idea in Antarctic ice loss

Quote
It's long been suspected but scientists can now show conclusively that thinning in the ring of floating ice around Antarctica is driving mass loss from the interior of the continent.

A new study finds the diminishing thickness of ice shelves is matched almost exactly by an acceleration in the glaciers feeding in behind them.

What's more, the linkage is immediate.

It means we can't rely on a lag in the system to delay the rise in sea-levels as shelves melt in a warmer world.

The glaciers will speed up in tandem, dumping their mass in the ocean.

"The response is essentially instantaneous," said Prof Hilmar Gudmundsson from Northumbria University, UK.

"If you thin the ice shelves today, the increase in flow of the ice upstream will increase today - not tomorrow, not in 10 or 100 years from now; it will happen immediately," he told BBC News.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019GL085027?referrer_access_token=WhCD_O2u8vrIp__p6QmCw8OuACxIJX3yJRZRu4P4ertAV37hBANYo5mjX4PQ9l-KKBGgyo-3AdRM0FL43dCQqj52nh1z1h0qbATv733xW9nrcKWnqGhyOBuPJawI3XLSipmandS2ADwobhotGKS01w%3D%3D
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2090 on: December 02, 2019, 10:05:32 PM »
The linked research indicates that the Southern Ocean is absorbing less CO₂ than previously assumed, possibly due changes in the surface currents associate with changes in the westerlies.

Title: "Antarctic Ocean Discovery Warns of Faster Global Warming"

http://www.climatecentral.org/news/antarctic-ocean-discovery-warns-of-faster-global-warming-21865

Extract: "A group of scientists, including one from the University of Arizona, has new findings suggesting Antarctica's Southern Ocean — long known to play an integral role in climate change — may not be absorbing as much pollution as previously thought.

The old belief was the ocean pulled about 13 percent of the world’s carbon dioxide — a greenhouse gas that contributes to climate change — out of the atmosphere, helping put the brakes on rising global temperatures.

To reach their contradictory conclusion, the team used state-of-the-art sensors to collect more data on the Southern Ocean than ever before, including during the perilous winter months that previously made the research difficult if not impossible.

Some oceanographers suspect that less CO2 is being absorbed because the westerlies — the winds that ring the southernmost continent — are tightening like a noose. As these powerful winds get more concentrated, they dig at the water, pushing it out and away."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2091 on: December 02, 2019, 10:09:14 PM »
...
"If you thin the ice shelves today, the increase in flow of the ice upstream will increase today - not tomorrow, not in 10 or 100 years from now; it will happen immediately," he told BBC News.


Thanks, when I read the report I was too busy thinking about how quickly an MICI-mechanism might propagate upstream into the Byrd Subglacial Basin to provide a link to the research.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2092 on: December 02, 2019, 10:42:46 PM »
The linked reference confirms that effective values of ECS based on historical estimates were higher than previously assumed:

Timothy Andrews et al. (30 July 2018), "Accounting for Changing Temperature Patterns Increases Historical Estimates of Climate Sensitivity", Geophysical Research Letters, https://doi.org/10.1029/2018GL078887

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL078887

Abstract
Eight atmospheric general circulation models (AGCMs) are forced with observed historical (1871–2010) monthly sea surface temperature and sea ice variations using the Atmospheric Model Intercomparison Project II data set. The AGCMs therefore have a similar temperature pattern and trend to that of observed historical climate change. The AGCMs simulate a spread in climate feedback similar to that seen in coupled simulations of the response to CO2 quadrupling. However, the feedbacks are robustly more stabilizing and the effective climate sensitivity (EffCS) smaller. This is due to a pattern effect, whereby the pattern of observed historical sea surface temperature change gives rise to more negative cloud and longwave clear‐sky feedbacks. Assuming the patterns of long‐term temperature change simulated by models, and the radiative response to them, are credible; this implies that existing constraints on EffCS from historical energy budget variations give values that are too low and overly constrained, particularly at the upper end. For example, the pattern effect increases the long‐term Otto et al. (2013, https://doi.org/10.1038/ngeo1836) EffCS median and 5–95% confidence interval from 1.9 K (0.9–5.0 K) to 3.2 K (1.5–8.1 K).

Plain Language Summary
Recent decades have seen cooling over the eastern tropical Pacific and Southern Oceans while temperatures rise globally. Climate models indicate that these regional features, and others, are not expected to continue into the future under sustained forcing from atmospheric carbon dioxide increases. This matters because climate sensitivity depends on the pattern of warming, so if the past has warmed differently from what we expect in the future, then climate sensitivity estimated from the historical record may not apply to the future. We investigate this with a suite of climate models and show that climate sensitivity simulated for observed historical climate change is smaller than for long‐term carbon dioxide increases. The results imply that historical energy budget changes only weakly constrain climate sensitivity.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2093 on: December 02, 2019, 11:48:40 PM »
As some readers may tire of pessimistic science reports on climate change risks; I provide the linked article about a Middle Eastern businessman that plans to tow Antarctic icebergs to more tropical ocean water (such as the U.A.E.).  If an MICI-type of failure pushes an armada of icebergs into the Southern Ocean some decade from now, maybe a massive application of this technology could put the icebergs to beneficial use while concurrently cooling potential increases in tropical ocean SST values:

Title: "Why a Middle Eastern business thirsty for water can't just tow an iceberg from Antarctica"

https://www.abc.net.au/news/2019-08-14/why-a-middle-eastern-business-cant-just-tow-antarctica-iceberg/11318638

Key points:
•   A firm from the United Arab Emirates wants to tow an iceberg to provide fresh water
•   Experts and regulators have identified numerous assessments, requirements, and hurdles to the plan
•   The head of the firm remains "optimistic" he can secure relevant approvals

Edit, see also:

Title: "Icebergs could be towed from Antarctica to solve Cape Town drought, expert says"

https://news.sky.com/story/icebergs-could-be-towed-from-antarctica-to-solve-cape-town-drought-expert-says-11354852

Extract: "Plans have been unveiled to tow icebergs from Antarctica to South Africa to help solve Cape Town's crippling water shortage.

Mr Sloane, who led the re-floating of the Costa Concordia cruise liner in 2014, said his team could wrap passing icebergs in fabric skirts to protect them and reduce evaporation.

"We want to show that if there is no other source to solve the water crisis, we have another idea no one else has thought of yet," he said.

Large tankers would guide the blocks into the Benguela Current that flows along the west coast of southern Africa, before a milling machine would cut into the ice.

A single iceberg "could produce about 150 million litres per day for about a year," around 30% of Cape Town's needs, Mr Sloane said.

The director of the marine salvage firm Resolve Marine said he was planning to hold a conference later this month to try and sell the $130m (£95m) project to officials and investors."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2094 on: December 03, 2019, 04:57:49 PM »

 If an MICI-type of failure pushes an armada of icebergs into the Southern Ocean some decade from now, maybe a massive application of this technology could put the icebergs to beneficial use while concurrently cooling potential increases in tropical ocean SST values:


If some readers believe that it is totally unrealistic to assume that there could be sufficient economic benefits to pay for moving an armada of Southern Ocean icebergs to the tropical oceans (not only for freshwater supply but possibly for: OTEC (ocean thermal energy conversion); cooling of waste heat, etc.); then consider that:

1. Per the first image a nudge from oceangoing tugboats could push an iceberg out of the ACC and into one of the three indicated cold currents leading north from the Southern Ocean into the Pacific, Atlantic and Indian Oceans.

2. Per the second image these three cold current feed into warm currents that would carry any such icebergs directly to the tropical ocean regions of all three oceans without towing, and would slowly melt along the way, thus both cooling and freshening the surface waters of the tropical oceans.

3. Per the third image (showing a representative thermocline profile for tropical ocean regions) cooling of the SSTA in these regions would both slow/stop increase surface evaporation associated with global warming and for at least decades would prevent the tropical oceans SST from increase by 5C; which is projected to lead to an equable climate.

Such a form of geoengineering would be much less expensive than other currently conceived forms of geoengineering.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2095 on: December 03, 2019, 05:22:31 PM »
The first attached Global Carbon Project image essentially shows that the reductions in coal use have been balanced by an increase in natural gas (methane has up to a GWP 36-times that of CO2) consumption; while the reported increases in wind, solar and hydropower have largely been balanced by a decrease in nuclear power consumption.  Thus with regard to net CO2-equivalent emissions, we are just moving the deck chairs on the Titanic.

Edit: Current world population is about 7.75 billion people, and the second attached image shows the assumed population growth for the five SSP families of forcing scenarios.  As all scenarios assume a currently growing global population, this implies that GHG emission will continue to grow for some time due to population growth alone
« Last Edit: December 03, 2019, 09:29:25 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2096 on: December 03, 2019, 05:37:40 PM »
The linked reference look at CMIP5 model projections and finds that: "… using a single model to approximate the internal climate variability produces distributions that are too narrow and do not fully represent the uncertainty in the climate system property estimates."

Thus, in my opinion when AR6 looks at the final CMIP6 projections they should report the combined internal climate variabilities for all the reported CMIP6 models; which will likely be much higher than for the CMIP5 model projections.  The deep uncertainty associated with the full range of internal climate variability with CMIP6 will likely represent a significant climate risk:

Libardoni, A.G., C.E. Forest, A.P. Sokolov and E. Monier (2019): Underestimating Internal Variability Leads to Narrow Estimates of Climate System Properties. Geophysical Research Letters, 46(16), 10000-10007, doi: 10.1029/2019GL082442.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082442

Abstract: Probabilistic estimates of climate system properties often rely on the comparison of model simulations to observed temperature records and an estimate of the internal climate variability. In this study, we investigate the sensitivity of probability distributions for climate system properties in the Massachusetts Institute of Technology Earth System Model to the internal variability estimate. In particular, we derive probability distributions using the internal variability extracted from 25 different Coupled Model Intercomparison Project Phase 5 models. We further test the sensitivity by pooling variability estimates from models with similar characteristics. We find the distributions to be highly sensitive when estimating the internal variability from a single model. When merging the variability estimates across multiple models, the distributions tend to converge to a wider distribution for all properties. This suggests that using a single model to approximate the internal climate variability produces distributions that are too narrow and do not fully represent the uncertainty in the climate system property estimates.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2097 on: December 03, 2019, 06:14:40 PM »
The linked reference confirms that AR5 significantly underestimated natural emissions of methane from wetlands worldwide, and recommends that policy makers shoulder the responsibility of taking corrective actions associated with AR5s shortcomings on this matter:

The linked reference indicates that the IPCC underestimated methane emissions from livestock:

Given that we can measure the concentration of methane in the atmosphere and thus calculate the total net emissions (all sources minus all sinks), if two sources were underestimated that implies that another source (or multiple sources) were overestimated or that the sinks were underestimated.

Did either reference provide information about what other sources were overestimated or if the sinks were underestimated?

Here a pre-print paper providing a literature review of what "consensus scientists" think the global methane budget has been from 2000 to 2017.  It is probably a good preview of what will show up in IPCC AR6.

https://climatehomes.unibe.ch/~joos/papers/saunois19essddis.pdf

Quote
The Global Methane Budget 2000-2017

Abstract.

Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 are continuing to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). Assessing the relative importance of CH4 in comparison to CO2 is complicated by its shorter atmospheric lifetime, stronger warming potential, and atmospheric growth rate variations over the past decade, the causes of which are still debated. Two major difficulties in reducing uncertainties arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations). 

For the 2008-2017 decade, global methane emissions are estimated by atmospheric inversions (top-down approach) to be 572 Tg CH4 yr-1 (range 538-593, corresponding to the minimum and maximum estimates of the ensemble), of which 357 Tg CH4 yr-1 or ~60% are attributed to anthropogenic sources (range 50-65%). This total emission is 27 Tg CH4 yr-1 larger than the value estimated for the period 2000-2009 and 24 Tg CH4 yr-1 larger than the one reported in the previous budget for the period 2003-2012 (Saunois et al. 2016). Since 2012, global CH4 emissions have been tracking the carbon intensive scenarios developed by the Intergovernmental Panel on Climate Change (Gidden et al., 2019). Bottom-up methods suggest larger global emissions (737 Tg CH4 yr-1, range 583-880) than top-down inversion methods, mostly because of larger estimated natural emissions from sources such as natural wetlands, other inland water systems, and geological sources. However the strength of the atmospheric constraints on the top-down budget, suggest that these bottom-up emissions are overestimated. The latitudinal distribution of atmospheric-based emissions indicates a predominance of tropical emissions (~65% of the global budget, <30°N) compared to mid (~30%, 30°N-60°N) and high northern latitudes (~4%, 60°N-90°N). Our analyses suggest that uncertainties associated with estimates of anthropogenic emissions are smaller than those of natural sources, with top-down inversions yielding larger uncertainties than bottom-up inventories and models. The most important source of uncertainty in the methane budget is attributable to natural emissions, especially those from wetlands and other inland waters. Some global source estimates are smaller compared to the previously published budgets (Saunois et al. 2016; Kirschke et al. 2013), particularly for vegetated wetland emissions that are lower by about 35 Tg CH4 yr-1 due to efforts to partition vegetated wetlands and inland waters. Emissions from geological sources are also found to be smaller by 7 Tg CH4 yr-1, and wild animals by 8 Tg CH4 yr-1. However the overall discrepancy between bottom-up and top-down estimates has been reduced by only 5% compared to Saunois et al. (2016), due to a higher estimate of freshwater emissions resulting from recent research and the integration of emissions from estuaries. Priorities for improving the methane budget include: i) a global, high-resolution map of water-saturated soils and inundated areas emitting methane based on a robust classification of different types of emitting habitats; ii) further development of process-based models for inland-water emissions; iii) intensification of methane observations at local scales (e.g., FLUXNET-CH4 measurements and urban monitoring to constrain bottom-up land surface models, and at regional scales (surface networks and satellites) to constrain atmospheric inversions; iv) improvements of transport models and the representation of photochemical sinks in top-down inversions, and v) development of a 3D variational inversion system using isotopic and/or co-emitted species such as ethane. 

The data presented here can be downloaded from ICOS (https://doi.org/10.18160/GCP-CH4-2019; Saunois et al., 2019) and the Global Carbon Project. 

Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2098 on: December 03, 2019, 06:18:16 PM »
The linked reference confirms that effective values of ECS based on historical estimates were higher than previously assumed:

Timothy Andrews et al. (30 July 2018), "Accounting for Changing Temperature Patterns Increases Historical Estimates of Climate Sensitivity", Geophysical Research Letters, https://doi.org/10.1029/2018GL078887

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL078887

Abstract
Eight atmospheric general circulation models (AGCMs) are forced with observed historical (1871–2010) monthly sea surface temperature and sea ice variations using the Atmospheric Model Intercomparison Project II data set. The AGCMs therefore have a similar temperature pattern and trend to that of observed historical climate change. The AGCMs simulate a spread in climate feedback similar to that seen in coupled simulations of the response to CO2 quadrupling. However, the feedbacks are robustly more stabilizing and the effective climate sensitivity (EffCS) smaller. This is due to a pattern effect, whereby the pattern of observed historical sea surface temperature change gives rise to more negative cloud and longwave clear‐sky feedbacks. Assuming the patterns of long‐term temperature change simulated by models, and the radiative response to them, are credible; this implies that existing constraints on EffCS from historical energy budget variations give values that are too low and overly constrained, particularly at the upper end. For example, the pattern effect increases the long‐term Otto et al. (2013, https://doi.org/10.1038/ngeo1836) EffCS median and 5–95% confidence interval from 1.9 K (0.9–5.0 K) to 3.2 K (1.5–8.1 K).

Plain Language Summary
Recent decades have seen cooling over the eastern tropical Pacific and Southern Oceans while temperatures rise globally. Climate models indicate that these regional features, and others, are not expected to continue into the future under sustained forcing from atmospheric carbon dioxide increases. This matters because climate sensitivity depends on the pattern of warming, so if the past has warmed differently from what we expect in the future, then climate sensitivity estimated from the historical record may not apply to the future. We investigate this with a suite of climate models and show that climate sensitivity simulated for observed historical climate change is smaller than for long‐term carbon dioxide increases. The results imply that historical energy budget changes only weakly constrain climate sensitivity.

The last line of the abstract is worth repeating:

Quote
For example, the pattern effect increases the long‐term Otto et al. (2013, https://doi.org/10.1038/ngeo1836) EffCS median and 5–95% confidence interval from 1.9 K (0.9–5.0 K) to 3.2 K (1.5–8.1 K).

The consensus ECS is from 2.0 to 4.5 degrees K with most paleo evidence indicating a most likely ECS around 3 degrees K.  So with the adjustment, the one example given went from being outside of the consensus (at 1.9 K), to almost at the median value (3.2 K).

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2099 on: December 03, 2019, 06:51:10 PM »

Given that we can measure the concentration of methane in the atmosphere and thus calculate the total net emissions (all sources minus all sinks), if two sources were underestimated that implies that another source (or multiple sources) were overestimated or that the sinks were underestimated.


The attached NOAA plot of the atmospheric methane concentrations at the South Pole from 2006 to Dec 2, 2019 indicate that the trend line of this methane concentration is accelerating; thus if some methane sources are not changing then other sources are currently accelerating, and may accelerate even more in the future due to global warming.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson