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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #50 on: September 20, 2017, 04:47:02 PM »
Quote
The radiative impact of the dynamical cloud changes are found to be comparable in magnitude to that of the microphysical cloud changes, and act to further amplify the inter-hemispheric asymmetry of the aerosol radiative forcing.

Is this a major deviation from what has currently been assumed? if so, this is pretty cutting-edge stuff!

Not really.  Many have claimed that the radiative impact is quite high.  Others not so much.  This is still a highly debated topic.

The linked abstract concludes: "From simulations with different versions of GEOS meteorological fields we find that tropospheric ozone in GEOS-Chem v10-01 has a global production rate of 4960–5530 Tg a−1, lifetime of 20.9–24.2 days, burden of 345–357 Tg, and STE of 325–492 Tg a−1. Change in the intensity of tropical deep convection between these different meteorological fields is a major factor driving differences in the ozone budget."  Obviously, models that show an increase in atmospheric tropical deep convection (see the first attached image by Sherwood 2014) also show stronger effective radiative forcing and higher climate sensitivity (e.g. the middle panel of the second attached image [from Andrew 2015] shows ECS as high as 5C with high tropical deep convection).  The fact that scientists are still discussing which models are correct should not make people feel good, when we only have one planet to live on:

Lu Hu et al (2017), "Global budget of tropospheric ozone: Evaluating recent model advances with satellite (OMI), aircraft (IAGOS), and ozonesonde observations", Atmospheric Environment, Volume 167, October 2017, Pages 323-334, https://doi.org/10.1016/j.atmosenv.2017.08.036

http://www.sciencedirect.com/science/article/pii/S1352231017305484?utm_content=buffer39aa1&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "The global budget of tropospheric ozone is governed by a complicated ensemble of coupled chemical and dynamical processes. Simulation of tropospheric ozone has been a major focus of the GEOS-Chem chemical transport model (CTM) over the past 20 years, and many developments over the years have affected the model representation of the ozone budget. Here we conduct a comprehensive evaluation of the standard version of GEOS-Chem (v10-01) with ozone observations from ozonesondes, the OMI satellite instrument, and MOZAIC-IAGOS commercial aircraft for 2012–2013. Global validation of the OMI 700-400 hPa data with ozonesondes shows that OMI maintained persistent high quality and no significant drift over the 2006–2013 period. GEOS-Chem shows no significant seasonal or latitudinal bias relative to OMI and strong correlations in all seasons on the 2° × 2.5° horizontal scale (r = 0.88–0.95), improving on previous model versions. The most pronounced model bias revealed by ozonesondes and MOZAIC-IAGOS is at high northern latitudes in winter-spring where the model is 10–20 ppbv too low. This appears to be due to insufficient stratosphere-troposphere exchange (STE). Model updates to lightning NOx, Asian anthropogenic emissions, bromine chemistry, isoprene chemistry, and meteorological fields over the past decade have overall led to gradual increase in the simulated global tropospheric ozone burden and more active ozone production and loss. From simulations with different versions of GEOS meteorological fields we find that tropospheric ozone in GEOS-Chem v10-01 has a global production rate of 4960–5530 Tg a−1, lifetime of 20.9–24.2 days, burden of 345–357 Tg, and STE of 325–492 Tg a−1. Change in the intensity of tropical deep convection between these different meteorological fields is a major factor driving differences in the ozone budget."
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #51 on: September 20, 2017, 04:56:26 PM »
The linked article discusses a paleo event where synchronous halogen-rich volcanic eruptions in West Antarctica about 17.7 kya abruptly changed global climate by causing a stratospheric ozone depletion over Antarctica, in a manner not dissimilar to the ozone hole created over Antarctica circa the 1970's due to anthropogenic HFC emissions.  This shows not only the importance of accounting for the geographic distribution of changes in atmospheric ozone concentrations; but also that we have already triggered Hansen's ice-climate feedback mechanism that can cause abrupt climate change within decades of being triggered:

Joseph R. McConnell et al (2017), "Synchronous volcanic eruptions and abrupt climate change ∼17.7 ka plausibly linked by stratospheric ozone depletion", PNAS, vol. 114 no. 38 10035–10040, doi: 10.1073/pnas.1705595114

http://www.pnas.org/content/114/38/10035.short?utm_content=bufferc48cb&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Glacial-state greenhouse gas concentrations and Southern Hemisphere climate conditions persisted until ∼17.7 ka, when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the Southern Hemisphere, with many changes ascribed to a sudden poleward shift in the Southern Hemisphere westerlies and subsequent climate impacts. We used high-resolution chemical measurements in the West Antarctic Ice Sheet Divide, Byrd, and other ice cores to document a unique, ∼192-y series of halogen-rich volcanic eruptions exactly at the start of accelerated deglaciation, with tephra identifying the nearby Mount Takahe volcano as the source. Extensive fallout from these massive eruptions has been found >2,800 km from Mount Takahe. Sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface UV radiation indicate that the eruptions led to stratospheric ozone depletion. Rather than a highly improbable coincidence, circulation and climate changes extending from the Antarctic Peninsula to the subtropics—similar to those associated with modern stratospheric ozone depletion over Antarctica—plausibly link the Mount Takahe eruptions to the onset of accelerated Southern Hemisphere deglaciation ∼17.7 ka."
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #52 on: September 20, 2017, 05:11:15 PM »
In my experience scientists generally try to err on the side of least ERROR, and it is polite to assume that everyone, even those with whom we disagree, are following that in good faith. 

Hopefully, readers are aware that the term 'ERROR' must be considered in context.  ERROR in AR5 essentially means statistical variations from the model mean assuming the caveats and assumptions of the model are correct (which it is the responsibility of the reader to take into account).  Thus if the AR5 model does not include a module accounting for the chemical interactions of aerosols and reactive greenhouse gases (which is the case for many of the models included in AR5), then it is the readers responsibility to take this into account when considering the errors reported for those models (as AR5 does not make this correction for the reader).

Thus when trying to assess the risks of future climate change one would do well to consider that no AR5 model could match the high climate sensitivities observed in the paleoclimate record for such highly relevant cases as MIS 11c, as noted in the following quote from Hayhoe and Kopp (2016):

"A bias towards under-estimation is evident in predicting more recent rates of sea level rise, and other physical changes in the climate system, while scientific assessments over the past few decades have demonstrated a systematic tendency towards 'erring on the side of least drama'. Together, these limitations emphasize the need to stress-test ESMs against the paleoclimate record, and to build models and conduct simulations that explore potential catastrophic events and states of the world with low or unknown probability but profound consequences."

Edit: Currently, the best ESMs cannot match the highly sensitive climate response during MIS 11c (the Holsteinian Peak), see the attached image from Hansen & Sato 2011; which indicates that our current models are incomplete and thus their error bands do not reflect true probabilities of climate change impacts.
« Last Edit: September 20, 2017, 05:33:45 PM by AbruptSLR »
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #53 on: September 20, 2017, 05:54:38 PM »
Figure 5 of the reference on findings of the CloudSat & CALIPSO within the A-Train, shows a dramatic increase (more positive) in observed net cloud feedback as compared to prior assumptions.  This of course means that the associated effective radiative forcing, ERF, is higher than previously assumed.

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."

Caption: "Figure 5 Upper three panels are from Hartmann et al (1992) who estimate the contribution to the cloud radiative effects (CRE) of five classes of clouds as defined according to the ISCCP radiance classification (upper left). The bottom panels are the equivalent analysis but with classification determined by the radar-lidar data of CloudSat and CALIPSO where true cloud heights establish the types and cloud thickness (x axis) are from water and ice path information which is proportional to cloud optical depth. The differences in CRE between this latter analysis and that of Hartmann et al underscores the effects of misclassification of clouds on the interpretation of their radiative effects. Ci=cirrus, D.C.=Deep Convection, M.L.=multi-layer, AS=Altostratus, AC-Alto-cumulus, NS=Nimbostratus, St=stratus, SC=stratocumulus and Cu=cumulus."
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #54 on: September 20, 2017, 07:11:47 PM »
The first and second linked sources show that Shindell (2014) calculations show due to the efficacy of aerosols and ozone that the TCR is estimated to be lying within the range of 1.3 to 3.2 centigrade degrees, with a median value of 1.7 centigrade degrees.   This means that the lower bound of climate sensitivity cited in AR5 is too low, because of the assumptions that it made w.r.t. the efficacy of aerosols and ozone:

Shindell, D. T. (2014), "Inhomogeneous forcing and transient climate sensitivity", Nature Climate Change, doi: 10.1038/nclimate2136

http://www.nature.com/nclimate/journal/v4/n4/full/nclimate2136.html?foxtrotcallback=true

Also, the attached image by Shindell shows that the red TCR probability distribution function is skewed to the right, thus emphasizing higher values, the caption for the figure is given at the bottom of this post:

http://www.cccep.ac.uk/newsAndMedia/Releases/2014/Importance-of-new-study-on-the-sensitivity-of-the-Earths-climate.aspx

Extract: "Dr Shindell was a co-author on a paper by Alexander Otto and others, published in the journal ‘Nature Geoscience’ last year, which suggested that the value of the transient climate response lies between 0.9 and 2.0 centigrade degrees, with a median value of 1.3 centigrade degrees. However, Dr Shindell’s new paper shows that if a correction is made to the assumptions about aerosols and ozone, the transient climate response would be estimated to be higher, lying within the range of 1.3 to 3.2 centigrade degrees, with a median value of 1.7 centigrade degrees."

Also see:
http://www.realclimate.org/index.php/archives/2014/04/shindell-on-constraining-the-transient-climate-response/

&

David A. Stainforth, (2014), "Climate projection: Testing climate assumptions", Nature Climate Change4,248–249doi:10.1038/nclimate2172

Figure caption: "Figure shows representative probability distribution functions for TCR using the numbers from Shindell (2014) in a Monte Carlo calculation (Gaussian for Fghg and dTobs, lognormal fits for the skewed distributions for Faerosol+ozone+LU and E). The green line is if you assume exactly no difference between the effects of aerosols and GHGs; Red is if you estimate that difference using climate models; Dashed red is the small difference made by using a different start date (1850 instead of 1750)."

See also the linked SkS article entitled: "Challenges in Constraining Climate Sensitivity: Should IPCC AR5’s Lower Bound Be Revised Upward?", Posted on 11 June 2014 by John Fasullo

https://www.skepticalscience.com/challenges-constraining-climate-sensitivity.html
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jai mitchell

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Re: Radiative forcing and CO2eq
« Reply #55 on: September 20, 2017, 07:14:15 PM »
Quote
The radiative impact of the dynamical cloud changes are found to be comparable in magnitude to that of the microphysical cloud changes, and act to further amplify the inter-hemispheric asymmetry of the aerosol radiative forcing.

Is this a major deviation from what has currently been assumed? if so, this is pretty cutting-edge stuff!

Not really.  Many have claimed that the radiative impact is quite high.  Others not so much.  This is still a highly debated topic.

I meant about the inter-hemispheric amplication.
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Re: Radiative forcing and CO2eq
« Reply #56 on: September 24, 2017, 07:45:49 PM »
https://twitter.com/Peters_Glen/status/911889196905668609

Quote
RF from GHG reaches double CO₂ value (3.7W/m²) in ~2030, but total RF will remain close to CO₂ with aerosol cooling http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo3036.html

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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #57 on: September 24, 2017, 09:30:29 PM »
https://twitter.com/Peters_Glen/status/911889196905668609

Quote
RF from GHG reaches double CO₂ value (3.7W/m²) in ~2030, but total RF will remain close to CO₂ with aerosol cooling http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo3036.html

Thanks for the link, as the reference presents more reasonable data that does AR5.  Nevertheless, I am still concerned most people do not appreciate the risk associated with uncertainties (including both w.r.t. aerosols and cloud feedback), non-linear feedbacks (including from Arctic thermokarst lake emissions of GHGs), and dynamical climate attractors (including ENSO amplification of ECS).  I would feel a little bit better is the climate models could better simulate MIS 11; as I suspect that the WAIS collapsed during MIS 11, and that the associated ice-climate feedback from a similar abrupt collapse in the next few decades could push us into high ranges of Polar Amplification.
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jai mitchell

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Re: Radiative forcing and CO2eq
« Reply #58 on: September 25, 2017, 01:05:42 AM »
your concern is of course extremely valid, however, the timeline of 'collapse' in MIS-11 (and 5e) could be quite long.

https://s3.amazonaws.com/academia.edu.documents/45688326/science.281.5373.8220160516-12353-xh71hl.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1506297450&Signature=sCqwwOT7ZXrIpY8yBwIvq3rHWUw%3D&response-content-disposition=inline%3B%20filename%3DPleistocene_collapse_of_the_West_Antarct.pdf

interestingly, there is strong indication of east and central Antarctic ice mass gains during MIS-11 due to increased precipitation  https://www.nature.com/articles/srep41433?WT.feed_name=subjects_earth-and-environmental-sciences

the total contribution of sea level rise during MIS-11 from Greenland is gauged to be 6 meters though it took thousands of years to accomplish that melt.  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504289/

this value represents between 75% and 50% of the total potential range of sea level rise (9-12 Meters) during MIS-11  https://www.clim-past.net/12/1079/2016/cp-12-1079-2016.pdf
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #59 on: September 25, 2017, 03:52:23 AM »
your concern is of course extremely valid, however, the timeline of 'collapse' in MIS-11 (and 5e) could be quite long.

jai,

I appreciate both your validation of my concerns, and your paleoclimate information; however, while it is a little bit comforting that most of paleoclimate change occurs gradually, episodes associated with hosing events (like a 3m contribution to sea level rise from the abrupt collapse of the WAIS, as demonstrated by Hansen's ice-climate analysis) occur abruptly, and have occurred repeatedly in the paleo-record.  Furthermore, the point of my post was not to say that MIS 11 should serve as an analog for our current situation, but rather it demonstrates that Arctic Amplification can accelerate faster than our best current climate models can simulate.

Indeed, the linked article indicates that current climate models do not yet know how to correctly model the observed effects of local rapid warming (see the first attached image & the following extract)

Title: "Understanding Causes and Effects of Rapid Warming in the Arctic"

https://eos.org/project-updates/understanding-causes-and-effects-of-rapid-warming-in-the-arctic

Extract: "Although many individual consequences of changes in these Arctic climate parameters are known, their combined influence and relative importance for Arctic amplification are complicated to quantify and difficult to disentangle. As a result, there is not yet a consensus in the Arctic research community about the dominant mechanisms leading to the phenomenon of Arctic Amplification."

However, numerous paleo studies including Wolfe et al (2017) indicate that Arctic Amplification during periods warmer than the Holocene Thermal Maximum, was much higher than current models project (see the second attached image, and the considerations that the ocean heat content is already impacted by 267 years of anthropogenic global warming and as the ozone corrected value of CO2e is already above 530ppm):

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

http://www.geosociety.org/datarepository/2017/2017202.pdf

Best,
ASLR
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #60 on: September 25, 2017, 05:00:49 AM »
One example from MIS 5e of the possible abrupt collapse of the WAIS is indicated by O'Leary et al (2013), see the first image:

Michael J. O’Leary, Paul J. Hearty,William G. Thompson, Maureen E. Raymo, Jerry X. Mitrovica and Jody M.Webster (2013), doi:10.1038/ngeo1890

http://www.nature.com/ngeo/journal/v6/n9/full/ngeo1890.html
http://www.nature.com/ngeo/journal/v6/n9/fig_tab/ngeo1890_F1.html

Abstract: "During the last interglacial period, 127–116 kyr ago, global mean sea level reached a peak of 5–9  m above present-day sea level. However, the exact timing and magnitude of ice sheet collapse that contributed to the sea-level highstand is unclear. Here we explore this timing using stratigraphic and geomorphic mapping and uranium-series geochronology of fossil coral reefs and geophysical modelling of sea-level records from Western Australia. We show that between 127 and 119 kyr ago, eustatic sea level remained relatively stable at about 3–4 m above present sea level. However, stratigraphically younger fossil corals with U-series ages of 118.1±1.4 kyr are observed at elevations of up to 9.5 m above present mean sea level. Accounting for glacial isostatic adjustment and localized tectonics, we conclude that eustatic sea level rose to about 9 m above present at the end of the last interglacial. We suggest that in the last few thousand years of the interglacial, a critical ice sheet stability threshold was crossed, resulting in the catastrophic collapse of polar ice sheets and substantial sea-level rise."

Thus, a marine ice sheet collapse sometime between 119 kyr and 118.1+/- 1.4 kyr could explain the indicated abrupt sea level rise.  One possible explanation is that the paleo-WAIS went past a physical tipping point (see Pollard & DeConto 2015, & the second image) in that timeframe and became unstable and collapsed abruptly.
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #61 on: September 25, 2017, 04:01:07 PM »
The first linked article is entitled: "3M-year-old sediment tells the story of today's climate", and it discusses research about Lake El'gygytgyn, in Siberia, that began in 2009.  Even through the findings of this research has been available for years (see the last two linked references), ESMs have not been able to replicate that amount of Arctic Amplification documented by the Lake El'gygytgyn physical evidence.  This implies that the climate sensitivity of current estimates of effective radiative forcing need to be increased to appropriately capture the true climate change risks (including Hansen's ice-climate feedback mechanism due to 'freshwater hosing'):

https://www.eenews.net/stories/1060053182

Extract: "One of the "most astounding things" in the sediment, she said, was evidence that ancient summer temperatures in the region had spiked by as much as 14 degrees Fahrenheit higher than today, not just once, but several times in the past.

There is no direct way to measure the atmosphere of this ancient time, but repeated estimates from leaf stomata, ocean fossil studies and other remnants now put its carbon dioxide content at around 400 parts per million — about where it is today, largely due to the sharp rise of CO2 and other greenhouse gases since the Industrial Revolution began, literally gaining steam in the 1850s.

According to Brigham-Grette, that means the Earth is much more sensitive to climate change now, and it is speeding up as the planet tries to reach equilibrium from the new injection of heat.

The findings of the science team at Lake El'gygytgyn were also very hard for experts who use computer-driven climate models to understand. They pride themselves on being able to predict the speed of climate change in the future and also in the past by use of a technique called "hindcasting."

In the case of the late Pliocene, though, the models missed the ice melting. Yet the data collected from drilling in the Arctic and more recently from the Antarctic suggest it happened not just once, but repeatedly at both poles.

James White, a paleoclimatologist and climate modeler at the University of Colorado, Boulder, said Brigham-Grette's study is "one of the more important paleoclimate studies of the last 10 years."

"The fact that we don't get the Pliocene is a concern," he explained, because over the years, the modelers and the data gatherers have helped each other perfect their understanding of climate change and how to improve the models.

"We're not in equilibrium now, not even close," he asserted, as the planet's oceans struggle to distribute the new influx of heat.

A new Japanese study, published in February written by scientists from a team exploring ice cores drilled in Antarctica, found that ocean warming currents carrying heat from the tropics have become more unstable in the North Atlantic because of colder fresh water dripping from the melting ice of glaciers in Greenland. The phenomenon is called "freshwater hosing," which also appears to have happened in the ancient past.

"There's this attitude of 'Well, we're Americans, and we're going to tough it out and help people rebuild along our coastlines,'" she said. "Well, that's sort of stupid, because we're putting people and infrastructure back in harm's way.""



Gregory A. De Wet, Isla S. Castañeda, Robert M. DeConto & Julie Brigham-Grette  (February 2016), “A high-resolution mid-Pleistocene temperature record from Arctic Lake El'gygytgyn: A 50 kyr super interglacial from MIS 33 to MIS 31?”Earth and Planetary Science Letters 436:56-63 DOI: 10.1016/j.epsl.2015.12.021 

http://blogs.umass.edu/biogeochem/files/2016/01/de-Wet-et-al.-2016.pdf

&

Coletti, A. J., DeConto, R. M., Brigham-Grette, J., and Melles, M.: A GCM comparison of Pleistocene super-interglacial periods in relation to Lake El'gygytgyn, NE Arctic Russia, Clim. Past, 11, 979-989, doi:10.5194/cp-11-979-2015, 2015.

http://www.clim-past.net/11/979/2015/cp-11-979-2015.pdf
http://www.clim-past.net/11/979/2015/cp-11-979-2015.html
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #62 on: September 27, 2017, 10:52:07 AM »
The linked reference uses the ice sheet model Glimmer (& I note that all current ice sheet models cannot yet adequately model ice sheet behavior to accurately replicate abrupt ice mass loss from ice sheets) to improve our understanding of the differences between MIS 11 and MIS 5e, and identifies the AMOC as the contributing to the largest difference (as to why MIS 11 has a particularly high climate sensitivity).  Given the WAIS's instability and Hansen's ice-climate feedback mechanism (see the attached image from Hansen et al 2016), and the bipolar seesaw mechanism; I do not find this to be particularly surprising nor particularly comforting:

R. Rachmayani, M. Prange, D. J. Lunt, E. J. Stone & M. Schulz (23 September 2017), "Sensitivity of the Greenland Ice Sheet to interglacial climate forcing: MIS 5e versus MIS 11", Paleoceanography, DOI: 10.1002/2017PA003149 

http://onlinelibrary.wiley.com/doi/10.1002/2017PA003149/abstract?utm_content=buffer05e1a&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "The Greenland Ice Sheet (GrIS) is thought to have contributed substantially to high global sea levels during the interglacials of Marine Isotope Stage (MIS) 5e and 11. Geological evidence suggests that the mass loss of the GrIS was greater during the peak interglacial of MIS 11 than MIS 5e, despite a weaker boreal summer insolation. We address this conundrum by using the three-dimensional thermomechanical ice-sheet model Glimmer forced by CCSM3 climate model output for MIS 5e and MIS 11 interglacial time slices. Our results suggest a stronger sensitivity of the GrIS to MIS 11 climate forcing than to MIS 5e forcing. Besides stronger greenhouse gas radiative forcing, the greater MIS 11 GrIS mass loss relative to MIS 5e is attributed to a larger oceanic heat transport towards high latitudes by a stronger Atlantic meridional overturning circulation. The vigorous MIS 11 ocean overturning, in turn, is related to a stronger wind-driven salt transport from low to high latitudes promoting North Atlantic Deep Water formation. The orbital insolation forcing, which causes the ocean current anomalies, is discussed."
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jai mitchell

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Re: Radiative forcing and CO2eq
« Reply #63 on: September 27, 2017, 06:06:33 PM »
Thanks for that info ASLR.

the Pliocene is our better analog imo.

Of course, we really do not have a good analog in the paleoclimate since the rate of changes in GMT is orders of magnitude faster today than ever before.  The implications of lagging ocean surface temperatures coupled with ice sheet and glacier instability is explored by the Hansen work you cite. 

WRT WAIS this:  between 119 kyr and 118.1+/- 1.4 kyr is shocking but since the range of 3m rise goes to a negative value the uncertainty could mean 'instantaneous' or 'over 2,300 years'  Certainly not definitive.

the polar amplification trend under a regime of atmospheric translation of water vapor and associated latent heat to the poles, with implied changes in global atmospheric circulation regimes in the Hadley, Walker and Polar cells will be the big uncertainty that may drive this process more rapidly, though this will impact Greenland much more than Antarctica in the near term with WAIS primarily being reduced through regional warming and freshening of the Circumpolar Deep Water, as was recently observed through sea floor core sample analysis during the Pliocene.  https://link.springer.com/article/10.1007/s00367-016-0489-8

however, at this time I feel we have kind of hijacked this thread with off-topic discussion, can we relocate to a more appropriate thread for this? 
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #64 on: September 28, 2017, 09:42:00 AM »

WRT WAIS this:  between 119 kyr and 118.1+/- 1.4 kyr is shocking but since the range of 3m rise goes to a negative value the uncertainty could mean 'instantaneous' or 'over 2,300 years'  Certainly not definitive.

...

however, at this time I feel we have kind of hijacked this thread with off-topic discussion, can we relocate to a more appropriate thread for this?

While this discussion is relevant to effective radiative forcing this century, we can discontinue this discussion here if you feel that we are high-jacking this thread.

However, paleo calibrations aside, readers might ask themselves why, in January 2017, NOAA increased (from 2.0 meters) their extreme sea level rise by 2100 up to 2.5 +/- 0.15m (it is primarily because of their concern about WAIS stability):

Sweet, W.V., R.E. Kopp, C.P. Weaver, J. Obeysekera, R.M. Horton, E.R. Thieler and C. Zervas (2017) "Global and Regional Sea Level Rise Scenarios for the United States".



[url=https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf]https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf
[/url]

See also:
http://www.opc.ca.gov/webmaster/ftp/pdf/docs/rising-seas-in-california-an-update-on-sea-level-rise-science.pdf

Edit: Note that the probabilities given by Kopp 2014 were developed before DeConto & Pollard 2016 and thus are not current.

Edit 2: jai, if you are further interested in this topic, I made a related post (#1917) in the Conservative Scientists & its Consequences thread.
« Last Edit: September 29, 2017, 12:07:28 AM by AbruptSLR »
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AbruptSLR

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Re: Radiative forcing and CO2eq
« Reply #65 on: October 02, 2017, 08:19:51 PM »
The linked Columbia website (reflective James Hansen's thinking) on effective radiative forcing, and it calculates the effective radiative forcing of methane to include: "… simulated CH4-induced changes of O3 and stratospheric H2O …".

Title: "Radiative Forcings"

http://www.columbia.edu/~mhs119/Forcings/

Extract: "Fe provides a good prediction of the response to different forcing amounts.

The time dependent effective forcings relative to 1850 for the agents used in our computations are shown individually and as the total in the graph below."

See also:

Hansen et al (2017), "Young people’s burden: requirement of negative CO₂ emissions", Earth Syst. Dynam., 8, 577–616, https://doi.org/10.5194/esd-8-577-2017

https://www.earth-syst-dynam.net/8/577/2017/esd-8-577-2017.pdf

Extract: "The CH4 forcing includes its indirect effects, as increasing atmospheric CH4 causes tropospheric ozone (O3) and stratospheric water vapor to increase (Myhre et al., 2013)."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

jai mitchell

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Re: Radiative forcing and CO2eq
« Reply #66 on: October 07, 2017, 05:42:23 PM »
That last graphic is very interesting.

It shows a net forcing from 1850 of +2.5

However, measurements of ocean heat content as a proxy for Top-of-Atmosphere radiation imbalance (see: https://www.ocean-sci.net/12/925/2016/os-12-925-2016.pdf ) show that our current radiation imbalance is between 0.8 and 1.2 W/m^2.

of course, the imbalance of radiation is partially offset by changes in albedo and through blackbody emissions that increase as the earth warms (and it is warmer than 1850).  Though all indications are that the total albedo forcing is slightly positive since 1850 (less reflective). 

This then shows that on a globally averaged value, the temperature must increase somewhat to offset the current top-of-atmosphere energy imbalance.  Since blackbody emissions increase at fourth-power scales the temperature increase necessary will be slightly less than what has been observed (~ 1 C)  so this means that on a globally averaged temperature  scale about 0.8C is locked in at current TOA imbalance. 

This warming will not occur on the ocean surface, however, as has happend in the past, this warming will be represented in arctic amplification and land surface temperatures warming more than ocean surface temperatures.  Likely in proportion to shifts seen since 1850.

Then one must consider the end of fossil fuels to halt growing CO2 emissions and the subsequent halt in SO2 emissions, with some reductions in forcing from shortlived climate polutants, perhaps (at a very best case) 2/3 of the SO2 positive impact from halting emissions can be offset by shortlive climate pollutants and we will receive another +.23C from those combined effects.

so another +1.0C from today's value

Then we must include carbon cycle feedbacks and albedo feedbacks that operate on very short timelines (30-80 years) and we have a big ol question mark of locked in warming.  It starts with a minimum value of 300 GtC additional emissions from warming soils to this 300 GtC (Crowther 2016) http://www.nature.com/nature/journal/v540/n7631/full/nature20150.html?cookies=accepted

to this then add emissions from deeper soils that were not included in the Crowther study and are as much as 30% more than the surface soils value in Crowther, yeilding a total emissions value of 400 GtC http://newscenter.lbl.gov/2017/03/09/soils-carbon-climate/ 

These studies are much less rigorous than the recently published published 26-year study on mid-latitude forest soil carbon by Woods Hole and the release from these sources under warming conditions are so great that they are seen to potentially be enough to drive a self-perpetuating warming effecthttp://www.mbl.edu/blog/carbon-feedback-from-forest-soils-will-accelerate-global-warming-26-year-study-projects/ 

Note that there are 3,600 GtC in mid-latitude forest soils

In addition, another woods hole study, this of tropical forest carbon flows, shows that they are now either net neutral or positive emitters of CO2, which is very different from previous assumptions that they are carbon sinks.  https://www.theguardian.com/environment/2017/sep/28/alarm-as-study-reveals-worlds-tropical-forests-are-huge-carbon-emission-source

Finally, the changes in albedo will also produce future warming as Arctic sea ice disappears and cloud regimes move further northward.  This cloud regime movement is implicated to produce the 9C ESS value of locked in warming potential at our current GHG forcing levels as shown in Snyder (2016) https://www.nature.com/nature/journal/v538/n7624/abs/nature19798.html

It should be noted here that the -1.2W/m^2 is a low-end estimate of the total forcing impact of SO2 emissions since it does not include many potential indirect feedbacks, especially potential impacts on tropical cloud regimes and pacific ENSO patterns.
« Last Edit: October 07, 2017, 06:54:38 PM by jai mitchell »
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Tom_Mazanec

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Re: Radiative forcing and CO2eq
« Reply #67 on: June 15, 2019, 07:57:31 PM »
Here is a contributor to CO2e that I never would have guessed - hospital anesthesia:
https://www.cbc.ca/news/health/anesthetic-greenhouse-gases-1.5170662
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS