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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #150 on: February 28, 2014, 02:13:35 AM »
I want to let those who read this thread/folder that I have recently posted in the "Consequences" folder some relatively compelling information that the chances of a Super El Nino occurring from early summer 2014 to spring 2015, is increasing due to a projected increase in the westerly winds in the Western Pacific, which should strengthen an already strong Kelvin wave that is headed eastward across the Pacific.  See the following link:

http://forum.arctic-sea-ice.net/index.php/topic,730.msg21005.html#msg21005
« Last Edit: March 01, 2014, 04:45:17 AM by AbruptSLR »
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #151 on: March 02, 2014, 12:36:00 AM »
It is not pointed out in either of the two following linked research that as current estimates of "climate sensitivity" do not include this negative feedback; in order for Global Circulation Models, GCM's including this negative feedback to match historical records they will need to utilize higher effective "climate sensitivity" values; which should resulting in higher projections of global temperature increase, if plant growth/activity does not keep pace with the rate of future green house gas, GHC, emissions.  Also, see Reply #25.

Mikael Ehn, Joel A. Thornton, Einhard Kleist, Mikko Sipilä, Heikki Junninen, Iida Pullinen, Monika Springer, Florian Rubach, Ralf Tillmann, Ben Lee, Felipe Lopez-Hilfiker, Stefanie Andres, Ismail-Hakki Acir, Matti Rissanen, Tuija Jokinen, Siegfried Schobesberger, Juha Kangasluoma, Jenni Kontkanen, Tuomo Nieminen, Theo Kurtén, Lasse B. Nielsen, Solvejg Jørgensen, Henrik G. Kjaergaard, Manjula Canagaratna, Miikka Dal Maso et al (2014), " A large source of low-volatility secondary organic aerosol", Nature, 506, 476–479, doi:10.1038/nature13032


http://www.nature.com/nature/journal/v506/n7489/full/nature13032.html

Also, see:
http://www.bbc.com/news/science-environment-26340038


Abstract: "Forests emit large quantities of volatile organic compounds (VOCs) to the atmosphere. Their condensable oxidation products can form secondary organic aerosol, a significant and ubiquitous component of atmospheric aerosol, which is known to affect the Earth’s radiation balance by scattering solar radiation and by acting as cloud condensation nuclei. The quantitative assessment of such climate effects remains hampered by a number of factors, including an incomplete understanding of how biogenic VOCs contribute to the formation of atmospheric secondary organic aerosol. The growth of newly formed particles from sizes of less than three nanometres up to the sizes of cloud condensation nuclei (about one hundred nanometres) in many continental ecosystems requires abundant, essentially non-volatile organic vapours, but the sources and compositions of such vapours remain unknown. Here we investigate the oxidation of VOCs, in particular the terpene α-pinene, under atmospherically relevant conditions in chamber experiments. We find that a direct pathway leads from several biogenic VOCs, such as monoterpenes, to the formation of large amounts of extremely low-volatility vapours. These vapours form at significant mass yield in the gas phase and condense irreversibly onto aerosol surfaces to produce secondary organic aerosol, helping to explain the discrepancy between the observed atmospheric burden of secondary organic aerosol and that reported by many model studies. We further demonstrate how these low-volatility vapours can enhance, or even dominate, the formation and growth of aerosol particles over forested regions, providing a missing link between biogenic VOCs and their conversion to aerosol particles. Our findings could help to improve assessments of biosphere–aerosol–climate feedback mechanisms, and the air quality and climate effects of biogenic emissions generally."

Also, see the link to the following related reference:

Paasonen, P., et. al. (2013), "Evidence for negative climate feedback: warming increases aerosol number concentrations,", Nature Geoscience, 6, Pages: 438–442, doi: 10.1038/NGEO1800

http://www.nature.com/ngeo/journal/v6/n6/full/ngeo1800.html
“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: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #152 on: March 02, 2014, 07:00:02 PM »
The following reference brings focus to the seriousness of the issue that El Nino events on average induce drought conditions in most tropical rainforests (see attached image), as the reference looked at about 50-years of data and found "a two-fold increase of carbon cycle sensitivity to tropical temperature variations" primarily due to droughts.  As the average carbon cycle sensitivity of tropical lands is twice what our models are assuming, and we have been in a 15-year period without any strong El Nino events (due to the negative PDO); we can all well imagine what combine global warming and increasingly frequent strong El Nino events will do to the tropical rainforests for the coming positive phase of the PDO.  Also, remember that in the future when we transition to a negative PDO phase again, all that dead wood in the drought stricken tropical rainforests will be submerged in rain run-off causing more methane emissions (with a GWP 35 times that of carbon dioxide):


Xuhui Wang, Shilong Piao, Philippe Ciais, Pierre Friedlingstein, Ranga B. Myneni, Peter Cox, Martin Heimann, John Miller, Shushi Peng, Tao Wang, Hui Yang & Anping Chen, (2014), "A two-fold increase of carbon cycle sensitivity to tropical temperature variations", Nature, 506, 212–215, doi:10.1038/nature12915


http://www.nature.com/nature/journal/v506/n7487/full/nature12915.html#extended-data


Abstract: "Earth system models project that the tropical land carbon sink will decrease in size in response to an increase in warming and drought during this century, probably causing a positive climate feedback. But available data are too limited at present to test the predicted changes in the tropical carbon balance in response to climate change. Long-term atmospheric carbon dioxide data provide a global record that integrates the interannual variability of the global carbon balance. Multiple lines of evidence demonstrate that most of this variability originates in the terrestrial biosphere. In particular, the year-to-year variations in the atmospheric carbon dioxide growth rate (CGR) are thought to be the result of fluctuations in the carbon fluxes of tropical land areas. Recently, the response of CGR to tropical climate interannual variability was used to put a constraint on the sensitivity of tropical land carbon to climate change. Here we use the long-term CGR record from Mauna Loa and the South Pole to show that the sensitivity of CGR to tropical temperature interannual variability has increased by a factor of 1.9 ± 0.3 in the past five decades. We find that this sensitivity was greater when tropical land regions experienced drier conditions. This suggests that the sensitivity of CGR to interannual temperature variations is regulated by moisture conditions, even though the direct correlation between CGR and tropical precipitation is weak. We also find that present terrestrial carbon cycle models do not capture the observed enhancement in CGR sensitivity in the past five decades. More realistic model predictions of future carbon cycle and climate feedbacks require a better understanding of the processes driving the response of tropical ecosystems to drought and warming."


The caption for the attached image is (where CGR is "Carbon dioxide Growth Rate):

"CGR anomalies are from Mauna Loa Observatory and local MAT anomalies were derived from the CRU data set for the period 1960–2011. The correlation coefficients 0.23 and 0.28 are the critical thresholds at significance levels of 0.10 and 0.05 (n = 52), respectively."

In this figure, also note the high correlation between CGR and the north slope of Alaska, as El Nino events can push more warm water through the Bering Straits.
“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: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #153 on: March 05, 2014, 02:27:01 AM »
The following linked reference (with a free access pdf) indicates that equilibrium climate sensitivity cannot be reliably estimated from transient climate observations due to such reasons a the changes in ENSO response due to global warming as demonstrated by Kosaka and Xie (2013), [see reference at the end of the post].

Rose BEJ, KC Armour, DS Battisti, N Feldl and DDB Koll (2014) "The dependence of transient climate sensitivity and radiative feedbacks on the spatial pattern of ocean heat uptake", Geophysical Research Letters, 41, doi: 10.1002/2013GL058955

http://web.mit.edu/karmour/www/Rose_etal_GRL2014.pdf

Kosaka, Y., and S.-P. Xie (2013), Recent global-warming hiatus tied to equatorial Pacific surface cooling, Nature, 501, 403–407,
doi:10.1038/nature12534.

See also the following related abstract presented today at the APS meeting in Colorado:


Bulletin of the American Physical Society
APS March Meeting 2014
 Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session G40: Invited Session: The Physics of Climate
11:15 AM–2:15 PM, Tuesday, March 4, 2014
Chair: James Brasseur, Pennsylvania State University
Abstract: G40.00004 : Causes and consequences of time-varying climate sensitivity
1:03 PM–1:39 PM
Author:
  Kyle Armour
    (Massachusetts Institute of Technology)
Abstract: "While constraining climate sensitivity has long been a focus of climate science, this global and equilibrium metric provides only limited understanding of transient and regional changes over the coming centuries. Indeed, pronounced spatial and temporal variability of climate change has been observed, and climate models diverge strongly in projections of future warming. This intermodel spread is due, in part, to different representations of how global climate sensitivity (set by feedbacks linking surface warming to top-of-atmosphere radiative response) will vary in time as the Earth warms. Here I discuss mechanisms governing the time variation of climate sensitivity, and consider its implications for future climate prediction. I show that climate sensitivity depends fundamentally on the respective geographic patterns of local radiative feedbacks and surface warming, and thus it naturally varies in time as the pattern of surface warming evolves, activating feedbacks of different strengths in different regions. Further, the pattern of surface warming and the strength of local radiative feedbacks themselves (shortwave clouds feedbacks in particular) depend on regional ocean circulations and the resulting time-varying geographic pattern of ocean heat uptake. These results imply that equilibrium climate sensitivity cannot be reliably estimated from transient climate observations."

http://absimage.aps.org/image/MAR14/MWS_MAR14-2014-020936.pdf

Both of these documents imply that we cannot rely upon the CMIP5 to give reliable projections about future climate change.
“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: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #154 on: March 10, 2014, 10:53:15 AM »
The following linked reference reports that scientists have recently detected four new man-made gases that damage the ozone layer.  These new gases could possibly prevent the Antarctic ozone hole from healing itself, thus possibly resulting in sustained circumpolar winds around the Southern Ocean:

Johannes C. Laube, Mike J. Newland, Christopher Hogan, Carl A. M. Brenninkmeijer, Paul J. Fraser, Patricia Martinerie, David E. Oram, Claire E. Reeves, Thomas Röckmann, Jakob Schwander, Emmanuel Witrant & William T. Sturges, (2014), "Newly detected ozone-depleting substances in the atmosphere", Nature Geoscience, doi:10.1038/ngeo2109


http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2109.html


Abstract: "Ozone-depleting substances emitted through human activities cause large-scale damage to the stratospheric ozone layer, and influence global climate. Consequently, the production of many of these substances has been phased out; prominent examples are the chlorofluorocarbons (CFCs), and their intermediate replacements, the hydrochlorofluorocarbons (HCFCs). So far, seven types of CFC and six types of HCFC have been shown to contribute to stratospheric ozone destruction. Here, we report the detection and quantification of a further three CFCs and one HCFC. We analysed the composition of unpolluted air samples collected in Tasmania between 1978 and 2012, and extracted from deep firn snow in Greenland in 2008, using gas chromatography with mass spectrometric detection. Using the firn data, we show that all four compounds started to emerge in the atmosphere in the 1960s. Two of the compounds continue to accumulate in the atmosphere. We estimate that, before 2012, emissions of all four compounds combined amounted to more than 74,000 tonnes. This is small compared with peak emissions of other CFCs in the 1980s of more than one million tonnes each year. However, the reported emissions are clearly contrary to the intentions behind the Montreal Protocol, and raise questions about the sources of these gases."
“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: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #155 on: March 10, 2014, 02:06:19 PM »
The following linked reference presents analyses that the low end of the transient climate sensitivity assumed by CMIP5-like GCM projections are highly unlikely, indicating that global warming will proceed faster than AR5 projections indicate, thus putting the WAIS/AIS at greater risk of rapid retreat:

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

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2136.html


Abstract: "Understanding climate sensitivity is critical to projecting climate change in response to a given forcing scenario. Recent analyses have suggested that transient climate sensitivity is at the low end of the present model range taking into account the reduced warming rates during the past 10–15 years during which forcing has increased markedly. In contrast, comparisons of modelled feedback processes with observations indicate that the most realistic models have higher sensitivities. Here I analyse results from recent climate modelling intercomparison projects to demonstrate that transient climate sensitivity to historical aerosols and ozone is substantially greater than the transient climate sensitivity to CO2. This enhanced sensitivity is primarily caused by more of the forcing being located at Northern Hemisphere middle to high latitudes where it triggers more rapid land responses and stronger feedbacks. I find that accounting for this enhancement largely reconciles the two sets of results, and I conclude that the lowest end of the range of transient climate response to CO2 in present models and assessments (<1.3 °C) is very unlikely."
“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: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #156 on: March 12, 2014, 03:45:52 PM »
Models such as the following can be used to reduce some of the uncertainties associated with the amount of carbon currently sequestered in the ocean; however, in a changing (non-stationary) ocean food-chain, care needs to be taken when projecting the amount of carbon expected to be sequestered in the ocean in the future, as under certain cases this negative feedback mechanism for climate change could be disrupted, and/or reversed into a positive feedback mechanism:

Siegel, D. A., K. O. Buesseler, S. C. Doney, S. F. Sailley, M. J. Behrenfeld, and P. W. Boyd (2014), Global assessment of ocean carbon export by combining satellite observations and food-web models, Global Biogeochem. Cycles, 28, doi:10.1002/2013GB004743.

http://onlinelibrary.wiley.com/doi/10.1002/2013GB004743/abstract

Abstract: "The export of organic carbon from the surface ocean by sinking particles is an important, yet highly uncertain, component of the global carbon cycle. Here we introduce a mechanistic assessment of the global ocean carbon export using satellite observations, including determinations of net primary production and the slope of the particle size spectrum, to drive a food-web model that estimates the production of sinking zooplankton feces and algal aggregates comprising the sinking particle flux at the base of the euphotic zone. The synthesis of observations and models reveals fundamentally different and ecologically consistent regional-scale patterns in export and export efficiency not found in previous global carbon export assessments. The model reproduces regional-scale particle export field observations and predicts a climatological mean global carbon export from the euphotic zone of ~6 Pg C yr−1. Global export estimates show small variation (typically < 10%) to factor of 2 changes in model parameter values. The model is also robust to the choices of the satellite data products used and enables interannual changes to be quantified. The present synthesis of observations and models provides a path for quantifying the ocean's biological pump."


See also:
http://www.science20.com/news_articles/ocean_food_web_key_global_carbon_cycle-131468
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #157 on: March 29, 2014, 01:38:24 PM »
The following linked research indicates that emissions of methane of biological origins increase rapidly with increasing warming, even on a seasonal, or ENSO, basis:

Gabriel Yvon-Durocher, Andrew P. Allen, David Bastviken, Ralf Conrad, Cristian Gudasz, Annick St-Pierre, Nguyen Thanh-Duc & Paul A. del Giorgio, (2014), "Methane fluxes show consistent temperature dependence across microbial to ecosystem scales", Nature, Volume: 507, pp: 488–491, doi:10.1038/nature13164

http://www.nature.com/nature/journal/v507/n7493/full/nature13164.html

Abstract:  "Methane (CH4) is an important greenhouse gas because it has 25 times the global warming potential of carbon dioxide (CO2) by mass over a century. Recent calculations suggest that atmospheric CH4 emissions have been responsible for approximately 20% of Earth’s warming since pre-industrial times. Understanding how CH4 emissions from ecosystems will respond to expected increases in global temperature is therefore fundamental to predicting whether the carbon cycle will mitigate or accelerate climate change. Methanogenesis is the terminal step in the remineralization of organic matter and is carried out by strictly anaerobic Archaea. Like most other forms of metabolism, methanogenesis is temperature-dependent. However, it is not yet known how this physiological response combines with other biotic processes (for example, methanotrophy, substrate supply, microbial community composition) and abiotic processes (for example, water-table depth) to determine the temperature dependence of ecosystem-level CH4 emissions. It is also not known whether CH4 emissions at the ecosystem level have a fundamentally different temperature dependence than other key fluxes in the carbon cycle, such as photosynthesis and respiration. Here we use meta-analyses to show that seasonal variations in CH4 emissions from a wide range of ecosystems exhibit an average temperature dependence similar to that of CH4 production derived from pure cultures of methanogens and anaerobic microbial communities. This average temperature dependence (0.96 electron volts (eV)), which corresponds to a 57-fold increase between 0 and 30°C, is considerably higher than previously observed for respiration (approximately 0.65 eV) and photosynthesis (approximately 0.3 eV). As a result, we show that both the emission of CH4 and the ratio of CH4 to CO2 emissions increase markedly with seasonal increases in temperature. Our findings suggest that global warming may have a large impact on the relative contributions of CO2 and CH4 to total greenhouse gas emissions from aquatic ecosystems, terrestrial wetlands and rice paddies."
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jai mitchell

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #158 on: March 30, 2014, 04:25:40 PM »
ASR

you posted this:
Rose BEJ, KC Armour, DS Battisti, N Feldl and DDB Koll (2014) "The dependence of transient climate sensitivity and radiative feedbacks on the spatial pattern of ocean heat uptake", Geophysical Research Letters, 41, doi: 10.1002/2013GL058955

http://web.mit.edu/karmour/www/Rose_etal_GRL2014.pdf

But it says:
Quote
Under qT , there are large
changes in the partition of
« Last Edit: March 30, 2014, 04:31:35 PM by jai mitchell »
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #159 on: March 30, 2014, 08:22:59 PM »
jai,

I am not sure what the partial quote that you provided means (or implies).

Best,
ASLR
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jai mitchell

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #160 on: March 31, 2014, 02:47:07 AM »
For some reason it isn't letting me finish the post,  one. . .last . . .try

The SST link to Hadley Broadening in the models of your linked paper does not hold up to analysis.  There is another factor, the authors in

http://www.clim-past.net/8/1169/2012/cp-8-1169-2012.pdf
Changes in the strength and width of the Hadley Circulation
since 1871
J. Liu1, M. Song1, Y. Hu2, and X. Ren3
Clim. Past, 8, 1169–1175, 2012
www.clim-past.net/8/1169/2012/
doi:10.5194/cp-8-1169-2012

See another possibility in some unknown long-cycle. but it is really, for them, just an unknown.  I know that there is ample evidence to indicate that Arctic Amplification can provide the additional broadening, The recent stagnation of pacific SST while broadening has occurred should be enough to winnow out a signal.

here Is their quote:

Quote
The strength and width of the Hadley Circulation during
the late 19th to early 20th century experienced substantial
changes that exceed the changes associated with global
warming in recent decades. A simple relationship between
the strength and width of the Hadley Circulation and surface
temperature is not supported. These findings are intriguing
and raise the question of whether the recent changes in the
Hadley Circulation are primarily due to greenhouse warming
or long-term change of the Hadley Circulation (e.g. variability
of the Hadley Circulation at centennial timescales).
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #161 on: March 31, 2014, 05:49:19 AM »
jai,

Thanks for completing your post; however, I am traveling now & will need to respond properly later.

Best,
ASLR
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #162 on: April 01, 2014, 11:44:33 AM »
jai,

While I have not studied meteorology, but I concur that the link between SST and Hadley Cell broadening seems tenuous; however, possibly observations over the next period of positive Interdecal Pacific Oscillation, IPO, (possibly for the coming approximately 15 years) will help to clarify this matter.

Best,
ASLR
“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: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #163 on: April 03, 2014, 01:38:26 AM »
I hope that the following linked article on a methanogenic burst in the end-Permain does not have any relevance to the next hundred years, but who knows:

Daniel H. Rothman, Gregory P. Fournier, Katherine L. French, Eric J. Alm, Edward A. Boyle, Changqun Cao, and Roger E. Summons, (2014), "Methanogenic burst in the end-Permian carbon cycle", PNAS, doi: 10.1073/pnas.1318106111

Significance: "The end-Permian extinction is the most severe biotic crisis in the fossil record. Its occurrence has been attributed to increased CO2 levels deriving from massive Siberian volcanism. However, such arguments have been difficult to justify quantitatively. We propose that the disruption of the carbon cycle resulted from the emergence of a new microbial metabolic pathway that enabled efficient conversion of marine organic carbon to methane. The methanogenic expansion was catalyzed by nickel associated with the volcanic event. We support this hypothesis with an analysis of carbon isotopic changes leading up to the extinction, phylogenetic analysis of methanogenic archaea, and measurements of nickel concentrations in South China sediments. Our results highlight the sensitivity of the Earth system to microbial evolution."

http://www.pnas.org/content/early/2014/03/26/1318106111.abstract

Abstract:  "The end-Permian extinction is associated with a mysterious disruption to Earth’s carbon cycle. Here we identify causal mechanisms via three observations. First, we show that geochemical signals indicate superexponential growth of the marine inorganic carbon reservoir, coincident with the extinction and consistent with the expansion of a new microbial metabolic pathway. Second, we show that the efficient acetoclastic pathway in Methanosarcina emerged at a time statistically indistinguishable from the extinction. Finally, we show that nickel concentrations in South China sediments increased sharply at the extinction, probably as a consequence of massive Siberian volcanism, enabling a methanogenic expansion by removal of nickel limitation. Collectively, these results are consistent with the instigation of Earth’s greatest mass extinction by a specific microbial innovation."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #164 on: April 08, 2014, 03:04:46 PM »
According to the linked research: "Researchers from Florida State University have discovered new evidence that permafrost thawing is releasing copious amounts of greenhouse gases into the atmosphere by way of plants."

http://www.sciencerecorder.com/news/permafrost-thawing-could-accelerate-global-warming-researchers-say/#ixzz2yIdHoYmP

Suzanne B. Hodgkins, Malak M. Tfaily, Carmody K. McCalley, Tyler A. Logan, Patrick M. Crill, Scott R. Saleska, Virginia I. Rich, and Jeffrey P. Chanton, (2014), "Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production: PNAS; doi: 10.1073/pnas.1314641111

http://www.pnas.org/content/early/2014/04/02/1314641111.full.pdf+html?sid=dbc4b3ae-7ce1-40a5-9990-c6561a32afcb

Abstract: "Carbon release due to permafrost thaw represents a potentially major positive climate change feedback. The magnitude of carbon loss and the proportion lost as methane (CH4) vs. carbon dioxide (CO2) depend on factors including temperature, mobilization of previously frozen carbon, hydrology, and changes in organic matter chemistry associated with environmental responses to thaw. While the first three of these effects are relatively well understood, the effect of organic matter chemistry remains largely unstudied. To address this gap, we examined the biogeochemistry of peat and dissolved organic matter (DOM) along a ∼40-y permafrost thaw progression from recently- to fully thawed sites in Stordalen Mire (68.35°N, 19.05°E), a thawing peat plateau in northern Sweden. Thaw-induced subsidence and the resulting inundation along this progression led to succession in vegetation types accompanied by an evolution in organic matter chemistry. Peat C/N ratios decreased whereas humification rates increased, and DOM shifted toward lower molecular weight compounds with lower aromaticity, lower organic oxygen content, and more abundant microbially produced compounds. Corresponding changes in decomposition along this gradient included increasing CH4 and CO2 production potentials, higher relative CH4/CO2 ratios, and a shift in CH4 production pathway from CO2 reduction to acetate cleavage. These results imply that subsidence and thermokarst-associated increases in organic matter lability cause shifts in biogeochemical processes toward faster decomposition with an increasing proportion of carbon released as CH4. This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures, permafrost carbon mobilization, and hydrologic changes."
« Last Edit: April 08, 2014, 05:51:29 PM by AbruptSLR »
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #165 on: April 10, 2014, 01:27:45 AM »
The linked reference by Shindell (2014) indicates that the low end of the climate sensitivity range evaluated by AR5 is very unlikely to be correct:

http://www.nature.com/nclimate/journal/v4/n4/full/nclimate2136.html

D.T. Shindell, "Inhomogeneous forcing and transient climate sensitivity", Nature Climate change, vol. 4, pp. 274-277, 2014. http://dx.doi.org/10.1038/nclimate2136


Abstract: "Understanding climate sensitivity is critical to projecting climate change in response to a given forcing scenario. Recent analyses have suggested that transient climate sensitivity is at the low end of the present model range taking into account the reduced warming rates during the past 10–15 years during which forcing has increased markedly. In contrast, comparisons of modelled feedback processes with observations indicate that the most realistic models have higher sensitivities. Here I analyse results from recent climate modelling intercomparison projects to demonstrate that transient climate sensitivity to historical aerosols and ozone is substantially greater than the transient climate sensitivity to CO2. This enhanced sensitivity is primarily caused by more of the forcing being located at Northern Hemisphere middle to high latitudes where it triggers more rapid land responses and stronger feedbacks. I find that accounting for this enhancement largely reconciles the two sets of results, and I conclude that the lowest end of the range of transient climate response to CO2 in present models and assessments (<1.3 °C) is very unlikely."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #166 on: April 22, 2014, 05:41:23 PM »
The linked two part reference demonstrates numerically how greater uncertainty associated with climate sensitivity results in a non-subjective increase in the expected damage associated with global warming:

'Scientific Uncertainty and Climate Change: Part I. Uncertainty and Unabated Emissions' by Stephan Lewandowsky, James S Risbey, Michael Smithson, Ben R Newell and John Hunter published in Climatic Change April 2014 doi: 10.1007/s10584-014-1082-7

http://link.springer.com/article/10.1007/s10584-014-1082-7

Abstract: "Uncertainty forms an integral part of climate science, and it is often used to argue against mitigative action. This article presents an analysis of uncertainty in climate sensitivity that is robust to a range of assumptions. We show that increasing uncertainty is necessarily associated with greater expected damages from warming, provided the function relating warming to damages is convex. This constraint is unaffected by subjective or cultural risk-perception factors, it is unlikely to be overcome by the discount rate, and it is independent of the presumed magnitude of climate sensitivity. The analysis also extends to “second-order” uncertainty; that is, situations in which experts disagree. Greater disagreement among experts increases the likelihood that the risk of exceeding a global temperature threshold is greater. Likewise, increasing uncertainty requires increasingly greater protective measures against sea level rise. This constraint derives directly from the statistical properties of extreme values. We conclude that any appeal to uncertainty compels a stronger, rather than weaker, concern about unabated warming than in the absence of uncertainty."

'Scientific Uncertainty and Climate Change: Part II. Uncertainty and Mitigation' byStephan Lewandowsky, James S Risbey, Michael Smithson and Ben R Newell published in Climatic Change April 2014 doi:10.1007/s10584-014-1083-6


Abstract: "In public debate surrounding climate change, scientific uncertainty is often cited in connection with arguments against mitigative action. This article examines the role of uncertainty about future climate change in determining the likely success or failure of mitigative action. We show by Monte Carlo simulation that greater uncertainty translates into a greater likelihood that mitigation efforts will fail to limit global warming to a target (e.g., 2 °C). The effect of uncertainty can be reduced by limiting greenhouse gas emissions. Taken together with the fact that greater uncertainty also increases the potential damages arising from unabated emissions (Lewandowsky et al. 2014), any appeal to uncertainty implies a stronger, rather than weaker, need to cut greenhouse gas emissions than in the absence of uncertainty."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #167 on: April 23, 2014, 03:43:22 PM »
The linked reference indicates that newly studies factors indicate that greenhouse gas emissions from thawing permafrost will likely be more significant than previously expected:

Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production by Suzanne B. Hodgkinsa,Malak M. Tfailya, Carmody K. McCalleyb, Tyler A. Loganc, Patrick M. Crilld, Scott R. Saleskab, Virginia I. Riche, and Jeffrey P. Chantona, published in PNAS on 7 April 2014. DOI: 10.1073/pnas.1314641111

http://www.pnas.org/content/early/2014/04/02/1314641111

Abstract: "Carbon release due to permafrost thaw represents a potentially major positive climate change feedback. The magnitude of carbon loss and the proportion lost as methane (CH4) vs. carbon dioxide (CO2) depend on factors including temperature, mobilization of previously frozen carbon, hydrology, and changes in organic matter chemistry associated with environmental responses to thaw. While the first three of these effects are relatively well understood, the effect of organic matter chemistry remains largely unstudied. To address this gap, we examined the biogeochemistry of peat and dissolved organic matter (DOM) along a ∼40-y permafrost thaw progression from recently- to fully thawed sites in Stordalen Mire (68.35°N, 19.05°E), a thawing peat plateau in northern Sweden. Thaw-induced subsidence and the resulting inundation along this progression led to succession in vegetation types accompanied by an evolution in organic matter chemistry. Peat C/N ratios decreased whereas humification rates increased, and DOM shifted toward lower molecular weight compounds with lower aromaticity, lower organic oxygen content, and more abundant microbially produced compounds. Corresponding changes in decomposition along this gradient included increasing CH4 and CO2 production potentials, higher relative CH4/CO2 ratios, and a shift in CH4 production pathway from CO2 reduction to acetate cleavage. These results imply that subsidence and thermokarst-associated increases in organic matter lability cause shifts in biogeochemical processes toward faster decomposition with an increasing proportion of carbon released as CH4. This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures, permafrost carbon mobilization, and hydrologic changes."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #168 on: April 24, 2014, 01:02:40 AM »
According to the following linked NASA article (see attached image, and quote below) the Congo Rainforest has been browning for over a decade:

http://www.jpl.nasa.gov/news/news.php?release=2014-124


http://www.nasa.gov/

Quote: "A new analysis of NASA satellite data shows Africa's Congo rainforest, the second-largest tropical rainforest in the world, has undergone a large-scale decline in greenness over the past decade. The research is one of the most comprehensive observational studies to explore the effects of long-term drought on the Congo rainforest using several independent satellite sensors."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #169 on: April 25, 2014, 08:47:46 PM »
The linked article indicates that increased levels of carbon dioxide in the atmosphere cause soil microbes to produce more carbon dioxide, accelerating climate change:

http://www.sciencemag.org/content/early/2014/04/23/science.1249534
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #170 on: April 27, 2014, 09:04:41 AM »
I think all the papers linked in this thread are the discovery of previously unknown positive feedbacks. Is this a biased sample, or should we be worried that basically every climate feedback discovered makes our situation seem worse, indicating that the remaining knowledge could have a similar bias, and that taking current knowledge at face value is in itself a conservative is a bad option?

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #171 on: April 27, 2014, 10:35:10 PM »
andy_t_roo,

Feel free to roll-up your sleeves and post well-documents examples of newly identified negative feedback factors.  All of the ones that I have come across only last for a few decades, if we stay on a business as usual path, and then the ones that I have seen have become positive once sufficient GHG has accumulated (eg some extra CO2/warming helps some plants grow [particularly in the desert]; too much CO2/warming typically stresses most current plants).

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #172 on: May 01, 2014, 03:28:16 PM »
The following link leads to a Science Codex article about extensive wildfires in Eastern Russia.

http://www.sciencecodex.com/wildfire_outbreak_in_far_eastern_russia-132564

I am concerned with the likely El Nino this year that we will see an unusually large number of wildfires this year (and next); which could serve to accelerate carbon release from both the tundra, and the tropical rainforest, in the near-term.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #173 on: May 02, 2014, 12:08:20 AM »
For my 2,000th post I would like to thank Neven for creating and supporting this Forum for discussing critical topics regarding climate change.  With a handle like AbruptSLR/ASLR (Abrupt Sea Level Rise) it is obvious that I am alarmed about climate change; but hopefully I am not alarmist, to the extent that alarmism can interfere with discussion, learning and action about climate change.  I have learned as much as I have shared in this Forum, and the most important lesson that I have learned is that while most people believe that climate change is real, even more people believe that it will not have a significant impact on themselves, individually, as indicated by the attached image/graph from the June issue of Scientific America.  This black & white version of the graph (the original is in color) not only shows that a large majority of the US public support legislation on climate change (that politicians have yet to pass) but more importantly this graph indicates that only about 10% (+/- 5%) believe that anthropogenic global warming is "extremely important" to them, personally.

While this is a complex topic, the following are a few examples of the nature of this problem:

(1) First, Professor Robert Stavins, of Harvard, was one of the authors of a section of the IPCC WG3 report, on the impacts of international climate negotiations, and he recently revealed that nearly 75% of the original draft was deleted in a meeting in Berlin in April 2014 at the insistence of government officials.

(2) Second, the following linked reference indicates how both northern wetlands continued thawing, and tropical wetlands, are resulting in larger methane emissions than scientist previously raised:

Merritt R. Turetsky, Agnieszka Kotowska, Jill Bubier, Nancy B. Dise, Patrick Crill, Ed R. C. Hornibrook, Kari Minkkinen, Tim R. Moore, Isla H. Myers-Smith, Hannu Nykänen, David Olefeldt, Janne Rinne, Sanna Saarnio, Narasinha Shurpali, Eeva-Stiina Tuittila, J. Michael Waddington, Jeffrey R. White, Kimberly P. Wickland, Martin Wilmking, (2014), "A synthesis of methane emissions from 71 northern, temperate, and subtropical wetlands", Global Change Biology; DOI: 10.1111/gcb.12580

http://onlinelibrary.wiley.com/doi/10.1111/gcb.12580/abstract;jsessionid=A40F171C06B171BF21CA5D4B19FEDEDC.f04t02

Abstract: "Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30-day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30-day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e.g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release."

(3) Finally, the following linked reference indicates that methane emissions from shale gas developments exceed official EPA estimates:

Dana R. Caulton, Paul B. Shepson, Renee L. Santoro, Jed P. Sparks, Robert W. Howarth, Anthony R. Ingraffea, Maria O. L. Cambaliza, Colm Sweeney, Anna Karion, Kenneth J. Davis, Brian H. Stirm, Stephen A. Montzka, and Ben R. Miller, (2014), "Toward a better understanding and quantification of methane emissions from shale gas development", Proceedings of the National Academy of Science, doi: 10.1073/pnas.1316546111.

http://www.pnas.org/content/early/2014/04/10/1316546111.abstract.html?etoc

Abstract: "The identification and quantification of methane emissions from natural gas production has become increasingly important owing to the increase in the natural gas component of the energy sector. An instrumented aircraft platform was used to identify large sources of methane and quantify emission rates in southwestern PA in June 2012. A large regional flux, 2.0–14 g CH4 s−1 km−2, was quantified for a ∼2,800-km2 area, which did not differ statistically from a bottom-up inventory, 2.3–4.6 g CH4 s−1 km−2. Large emissions averaging 34 g CH4/s per well were observed from seven well pads determined to be in the drilling phase, 2 to 3 orders of magnitude greater than US Environmental Protection Agency estimates for this operational phase. The emissions from these well pads, representing ∼1% of the total number of wells, account for 4–30% of the observed regional flux. More work is needed to determine all of the sources of methane emissions from natural gas production, to ascertain why these emissions occur and to evaluate their climate and atmospheric chemistry impacts."

Obviously, I feel that such climate change considerations paint an increasingly clear image that serious the consequences may be in society's future, including possibly abrupt sea level rise associated with the inherent instability of the WAIS.
“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: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #174 on: May 02, 2014, 04:17:56 AM »
As a follow-on to my prior post, Chris Giles at the Financial Times writes that China is likely to overtake the U.S. this year. Giles draws on a new report from the International Comparison Program (ICP) that looks at the size of economies not based on market exchange rates, but through the purchasing power of parity (PPP).  Giles extrapolates from this to show how the change in methodology gives China the upper hand, see the first attached associated image by Giles 2014, and the following edited quotes:
“In 2005, the ICP thought China’s economy was less than half the size of the US, accounting for only 43 per cent of America’s total. Because of the new methodology – and the fact that China’s economy has grown much more quickly – the research placed China’s GDP at 87 percent of the US in 2011. …
“… With the IMF expecting China’s economy to have grown 24 per cent between 2011 and 2014 while the US is expected to expand only 7.6 per cent, China is likely to overtake the US this year.”
This unexpectedly high growth of China's economy increases the likelihood that AGW will at least remain on the RCP 8.5 pathway indicated by the pink line in the second attached image (note that the black dots indicate the historical record).
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #175 on: May 04, 2014, 03:21:24 AM »
The linked reference by Mann et al (2014) indicates that a portion of the recent global temperature hiatus was due to a cooling phase of the Atlantic Multidecadal Oscillation, AMO.  When this cycle enters a warming phase, we can expect global temperatures to increase more rapidly:

Michael E. Mann, Byron A. Steinman and Sonya K. Miller, (2014), "On forced temperature changes, internal variability, and the AMO"; Geophysical Research Letters. DOI: 10.1002/2014GL059233


http://onlinelibrary.wiley.com/doi/10.1002/2014GL059233/abstract;jsessionid=1006C5060715BA752C10209E000795FF.f04t03

"Abstract
We estimate the low-frequency internal variability of Northern Hemisphere (NH) mean temperature using observed temperature variations, which include both forced and internal variability components, and several alternative model simulations of the (natural + anthropogenic) forced component alone. We then generate an ensemble of alternative historical temperature histories based on the statistics of the estimated internal variability. Using this ensemble, we show, first, that recent NH mean temperatures fall within the range of expected multidecadal variability. Using the synthetic temperature histories, we also show that certain procedures used in past studies to estimate internal variability, and in particular, an internal multidecadal oscillation termed the “Atlantic Multidecadal Oscillation” or “AMO”, fail to isolate the true internal variability when it is a priori known. Such procedures yield an AMO signal with an inflated amplitude and biased phase, attributing some of the recent NH mean temperature rise to the AMO. The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming. Claims of multidecadal “stadium wave” patterns of variation across multiple climate indices are also shown to likely be an artifact of this flawed procedure for isolating putative climate oscillations."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #176 on: May 06, 2014, 01:26:14 AM »
The linked reference (with a free access pdf) indicates yet another positive feedback mechanism for climate change (even if it is a slow response feedback mechanism):

Roth, R., Ritz, S. P., and Joos, F., (2014), "Burial-nutrient feedbacks amplify the sensitivity of carbon dioxide to changes in organic matter remineralisation", Earth Syst. Dynam. Discuss., 5, 473-528, doi:10.5194/esdd-5-473-2014.

http://www.earth-syst-dynam-discuss.net/5/473/2014/esdd-5-473-2014.pdf

"Abstract. Changes in the marine remineralization of particulate organic carbon (POC) and calcium carbonate potentially provide a positive feedback under climate change. The responses to changes in remineralization length scales are systematically mapped with the Bern3D ocean–sediment model for CO2 and tracer fields for which observations and palaeoproxies exist. Spatio-temporal evolutions are captured by empirical orthogonal functions. Results show that the "sediment burial-nutrient feedback" amplifies the initial response in atmospheric CO2 by a factor of four to seven. A temporary imbalance between the weathering flux and the burial of organic matter and calcium carbonate lead to sustained changes the ocean's phosphate and alkalinity inventory and in turn in surface nutrient availability, marine productivity, and atmospheric CO2. It takes decades to centuries to reorganize tracers and fluxes within the ocean, many millennia to approach equilibrium for burial fluxes, while δ13C signatures are still changing 200 000 years after the perturbation. CO2 sensitivity is with 1.7 ppm m−1 about fifty times larger for a unit change in the remineralisation depth of POC than of calcium carbonate. The results highlight the role of organic matter burial for atmospheric CO2 and the substantial impacts of seemingly small changes in POC remineralisation."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #177 on: May 06, 2014, 06:16:09 PM »
The linked reference indicates that a portion of the recent "hiatus" impact on mean global temperatures can be linked directly to volcanic activity that cannot be relied upon for continued cooling:

Benjamin D. Santer, Céline Bonfils, Jeffrey F. Painter, Mark D. Zelinka, Carl Mears, Susan Solomon, Gavin A. Schmidt, John C. Fyfe, Jason N. S. Cole, Larissa Nazarenko, Karl E. Taylor & Frank J. Wentz, (2014),  "Volcanic contribution to decadal changes in tropospheric temperature", Nature Geoscience, Vol. 7, pp 185–189; doi:10.1038/ngeo2098
 
http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2098.html

Abstract: "Despite continued growth in atmospheric levels of greenhouse gases, global mean surface and tropospheric temperatures have shown slower warming since 1998 than previously. Possible explanations for the slow-down include internal climate variability, external cooling influences, and observational errors. Several recent modelling studies have examined the contribution of early twenty-first-century volcanic eruptions to the muted surface warming. Here we present a detailed analysis of the impact of recent volcanic forcing on tropospheric temperature, based on observations as well as climate model simulations. We identify statistically significant correlations between observations of stratospheric aerosol optical depth and satellite-based estimates of both tropospheric temperature and short-wave fluxes at the top of the atmosphere. We show that climate model simulations without the effects of early twenty-first-century volcanic eruptions overestimate the tropospheric warming observed since 1998. In two simulations with more realistic volcanic influences following the 1991 Pinatubo eruption, differences between simulated and observed tropospheric temperature trends over the period 1998 to 2012 are up to 15% smaller, with large uncertainties in the magnitude of the effect. To reduce these uncertainties, better observations of eruption-specific properties of volcanic aerosols are needed, as well as improved representation of these eruption-specific properties in climate model simulations."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #178 on: May 07, 2014, 07:42:50 PM »
As indicated by the first attached image, the Bølling–Allerød interstadial warm period ran from c. 14,700 to 12,700 years before the present, and mean global temperatures got very close to today's temperatures.  The linked reference indicates that earth system teleconnections associated with the Bølling–Allerød interstadial warming rapidly resulted in methane emissions; thus indicating that the current AGW could trigger similar rapid methane emissions from wet lands:

Julia L. Rosen, Edward J. Brook, Jerey P. Severinghaus, Thomas Blunier, Logan E. Mitchell, James E. Lee, Jon S. Edwards and Vasileios Gkinis, (2014) "An ice core record of near-synchronous global climate changes at the Bølling transition", Nature Geoscience, DOI: 10.1038/NGEO2147

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2147.html

Abstract: "The abrupt warming that initiated the Bølling–Allerød interstadial was the penultimate warming in a series of climate variations known as Dansgaard–Oeschger events. Despite the clear expression of this transition in numerous palaeoclimate records, the relative timing of climate shifts in different regions of the world and their causes are subject to debate. Here we explore the phasing of global climate change at the onset of the Bølling–Allerød using air preserved in bubbles in the North Greenland Eemian ice core. Specifically, we measured methane concentrations, which act as a proxy for low-latitude climate, and the 15N/14N ratio of N2, which reflects Greenland surface temperature, over the same interval of time. We use an atmospheric box model and a firn air model to account for potential uncertainties in the data, and find that changes in Greenland temperature and atmospheric methane emissions at the Bølling onset occurred essentially synchronously, with temperature leading by 4.5 +21/-24 years. We cannot exclude the possibility that tropical climate could lag changing methane concentrations by up to several decades, if the initial methane rise came from boreal sources alone. However, because even boreal methane-producing regions lie far from Greenland, we conclude that the mechanism that drove abrupt change at this time must be capable of rapidly transmitting climate changes across the globe."

The authors conclude: "We draw three important conclusions from these results. First, because no methane sources are known in the immediate vicinity of Greenland, synchronous changes in temperature and methane emissions reveal rapid transmission of the Bølling climate signal over large spatial scales regardless of the origin of methane. Second, such rapid transmission nullifies the use of all but the most precise phase analyses to shed light on the cause of this abrupt climate change. Third, inherent uncertainties (that is, small analytical errors, firn smoothing and firn heterogeneity) complicate the interpretation of even very high-resolution ice core data, preventing us from distinguishing between significantly different atmospheric histories, and illustrating that ice core gas records from low accumulation sites or climate intervals cannot be interpreted at sub-decadal timescales."

Caption for the second attachment: "Phase relationship between Greenland temperature and methane emissions at the Bølling transition. The normalized pooled (black) and cumulative pooled (grey) histograms of the phase lag (modelled surface temperature start time minus methane emission start time) at the Bølling transition for 25 surface temperature histories and 30 methane emissions scenarios. The vertical black line marks the median of the cumulative histogram; the dotted vertical lines show the 95% confidence interval. The most likely lead of methane emissions over temperature is 4.5 +21/-24 years. Courtesy: Nature Geoscience and the authors."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #179 on: May 10, 2014, 12:40:51 AM »
The following linked reference indicates that as atmospheric CO2 concentrations increase, we cannot rely upon vegetation growth to limit further atmospheric CO2 concentration:

Kees Jan van Groenigen, Xuan Qi, Craig W. Osenberg, Yiqi Luo, Bruce A. Hungate, (2014), "Faster Decomposition Under Increased Atmospheric CO2 Limits Soil Carbon Storage", Science 2, Vol. 344 no. 6183 pp. 508-509, DOI: 10.1126/science.1249534

http://www.sciencemag.org/content/344/6183/508.abstract

Abstract: "Soils contain the largest pool of terrestrial organic carbon (C) and are a major source of atmospheric carbon dioxide (CO2). Thus, they may play a key role in modulating climate change. Rising atmospheric CO2 is expected to stimulate plant growth and soil C input but may also alter microbial decomposition. The combined effect of these responses on long-term C storage is unclear. Combining meta-analysis with data assimilation, we show that atmospheric CO2 enrichment stimulates both the input (+19.8%) and the turnover of C in soil (+16.5%). The increase in soil C turnover with rising CO2 leads to lower equilibrium soil C stocks than expected from the rise in soil C input alone, indicating that it is a general mechanism limiting C accumulation in soil."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #180 on: May 13, 2014, 06:35:38 PM »
The linked reference essentially eliminates any possibility of a relatively low value for Earth's equilibrium climate sensitivity:

J.R. Kummer and A.E. Dessler, (2014), "The impact of forcing efficacy on the equilibrium climate sensitivity", Geophysical Research Letters, DOI: 10.1002/2014GL06004

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060046/abstract

Abstract: "Estimates of the Earth's equilibrium climate sensitivity (ECS) from 20th-century observations predict a lower ECS than estimates from climate models, paleoclimate data, and interannual variability. Here we show that estimates of ECS from 20th-century observations are sensitive to the assumed efficacy of aerosol and ozone forcing (efficacy for a forcer is the amount of warming per unit global average forcing divided by the warming per unit forcing from CO2). Previous estimates of ECS based on 20th-century observations have assumed that the efficacy is unity, which in our study yields an ECS of 2.3 K (5%-95%-confidence range of 1.6-4.1 K), near the bottom of the IPCC's likely range of 1.5-4.5 K. Increasing the aerosol and ozone efficacy to 1.33 increases the ECS to 3.0 K (1.9-6.8 K), a value in excellent agreement with other estimates. Forcing efficacy therefore provides a way to bridge the gap between the different estimates of ECS."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #181 on: May 13, 2014, 06:59:20 PM »
Thanks for pointing that article out, ASLR. There's a nice discussion of it and of related articles at SkS: https://www.skepticalscience.com/sense-and-climate-sensitivity-kummer-dessler-2014.html
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #182 on: May 13, 2014, 09:05:29 PM »
Per the attached NOAA image for 2014 up to May 10 of the atmospheric methane concentration measured a Mauna Loa; methane concentration appear to be accelerating compared to the trend for the previous 7 years (2006-2013).  It is possible that as we are now entering an approximately 15-phase of positive PDO, we may see continued acceleration of atmospheric methane concentrations:
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #183 on: May 13, 2014, 10:27:16 PM »
As I was concerned that some readers may not understand my immediate prior post, I attached this NOAA image of the Mauna Loa Atmospheric Methane readings from 1983 to April 2014, showing the methane concentration trend that I mentioned from late 2006 to the end of 2013; and I also attach the following links to studies showing how AGW is increasing methane emissions from both the tropical wetlands and from northern wetlands (associated with permafrost decomposition):

http://www.natureworldnews.com/articles/6785/20140428/increase-in-greenhouse-gas-emissions-linked-to-wetlands.htm

http://www.climatecentral.org/news/arctic-methane-emissions-certain-to-trigger-warming-17374

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #184 on: May 14, 2014, 01:43:17 AM »
The following link leads to an Associated Press article about a GAO study finding the US natural gas wells are leaking methane into the atmosphere at an unexpectedly high rate, and that the US Federal government failed to adequately regulate these leaks:

http://www.washingtonpost.com/business/technology/fed-govt-failed-to-inspect-higher-risk-oil-wells/2014/05/11/812f21de-d8eb-11e3-a837-8835df6c12c4_story.html
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #185 on: May 15, 2014, 07:10:14 PM »
The attached image is from Wikipedia's site for "climate sensitivity" (see the following link), and the indicated NASA equilibrium climate sensitivity, ECS, analysis clearly shows that the mean value for the ECS is well above the 3 degrees C value commonly used by the IPCC and other researchers, due to the "right-skewed distribution".  Furthermore, we should remain aware that that the indicated ECS analysis results do not include the very real possibility that slow-response climate sensitivity feedback factors such as possible increases in albedo (and/or nature methane emissions) may occur faster than considered by the model simulations:

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

Figure caption from the August 2010 NASA equilibrium climate sensitivity analysis: "This image shows a frequency distribution of climate sensitivity, based on model simulations. Based on the cited Lindsey (2010) public-domain source: To understand how uncertainty about the underlying physics of the climate system affects climate predictions, scientists have a common test: they have a model predict what the average surface temperature would be if atmospheric carbon dioxide concentrations were to double pre-industrial levels (the climate sensitivity).

They run this simulation thousands of times, each time changing the starting assumptions of one or more processes. When they put all the predictions from these thousands of simulations onto a single graph, what they get is a picture of the most likely outcomes and the least likely outcomes.

The pattern that emerges from these types of tests is interesting. Few of the simulations result in less than 2 °C of warming—near the low end of estimates by the Intergovernmental Panel on Climate Change (IPCC). Some simulations result in significantly more than the 4 °C, which is at the high end of the IPCC estimates.

This pattern (statisticians call it a “right-skewed distribution”) suggests that if carbon dioxide concentrations double, the probability of very large increases in temperature is greater than the probability of very small increases.

Our ability to predict the future climate is far from certain, but this type of research suggests that the question of whether global warming will turn out to be less severe than scientists think may be less relevant than whether it may be far worse."

Some researchers imply that such model simulations may be biased in favor of higher climate sensitivity values compared to ECS determined from the historical record; however, I am concerned that the interpretations of the historical record are frequently incomplete, due to our incomplete understanding of this phenomenon, and that we should follow the Precautionary Principal in order to ensure public safety, and that we should use ECS values higher than 3 degrees for our decision making (to be direct I prefer a value of 4.5 degrees C for decision making).
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #186 on: May 15, 2014, 07:32:00 PM »
To provide an idea of the implications of using an ECS of 4.5 degrees C for decision making instead of a 3 degrees C value, I attach the accompany extract from Michael Mann's March 2014 Sci. Am. article on this topic.  Note the indicated "Faux Pause" that the Earth has experienced during the recent negative phase of the IPO (Interdecadal Pacific Oscillation), which will likely reverse to an active heating phase during the coming 15-30 yr positive phase (also note that during the 1997-98 El Nino event at the end of the last positive IPO phase, the Earth's mean global temperature (see the thin white curve) trend could be taken as following the 4.5 degrees C ECS value):
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #187 on: May 16, 2014, 04:57:40 PM »
The linked reference (with a free pdf) and attached image indicates that during the rapid global warming (but slower than today's warming) the climate sensitivity was between 6.8 to 7.8 degrees C; which if true is a very frightening value, and implies to me that the slow response feedback mechanisms must have contributed in a rapid manner to global warming, and that the study is referring to Earth System Sensitivity, ESS, instead of Equilibrium Climate Sensitivity, ECS:

Mark Pagani, Ken Caldeira, David Archer, James C. Zachos, (2006), "An Ancient Carbon Mystery", Science, doi:10.1126/science.1136841

http://people.earth.yale.edu/sites/default/files/files/Pagani/1_2006%20Pagani_Science.pdf

Abstract: "Sudden global warming 55 million years ago provides evidence for high climate sensitivity to atmospheric CO2, but the source of the carbon remains enigmatic."

Caption for attached image: "Carbon release during the PETM. The amount of carbon needed to explain a 5°C change in global mean temperature depends on pre-PETM CO2 conditions (see the first figure) and the climate sensitivity to CO2 doubling (including associated system feedbacks). The source of carbon released (and climate sensitivity) can be estimated from the carbon isotopic composition of the released carbon and the 13C excursion it produced. For example, assuming a carbon isotope excursion of –3 to –5‰, carbon from methane (with an average 13C value of –60‰, green bar) would imply a carbon input of 1800 to 3500 PgC and a climate sensitivity of 6.8 to 7.8°C per CO₂ doubling. Terrestrial/marine organic carbon refers to organic carbon derived from the primary production of terrestrial and/or marine plants."
« Last Edit: May 16, 2014, 11:44:12 PM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #188 on: May 16, 2014, 05:47:24 PM »
The linked reference (with a free pdf) and attached figure, indicate that in the early Pliocene (over 4 million years ago, when the world was about 4 degrees warmer than pre-industrial era and CO₂ concentrations were about 415ppm) that Earth Systems Sensitivity, ESS, was about 9.6 +/- 1.4 degrees C.  If true this is a terribly high value:

Mark Pagani, Zhonghui Liu, Jonathan LaRiviere, Ana Christina Ravelo (2009), "High Earth-System Climate Sensitivity determined from Pliocene CO2 Concentrations", Nature geoscience, doi:10.1038/NGEO724

http://people.earth.yale.edu/sites/default/files/files/Pagani/1_2009%20Pagani_NatureGeosci.pdf

Abstract: "Climate sensitivity refers to the mean-annual global temperature response to CO2 doubling due to the radiative effects of CO2 and associated feedbacks. The proposed range of climate sensitivity, ~1.5 to 4.5oC, represents fast-feedback sensitivity that incorporates changes in atmospheric water vapor, sea ice, and cloud and aerosol distributions. However, other feedbacks involving changes in continental ice extent, terrestrial ecosystems, non-CO2 greenhouse gas production, and other climate system parameters, operate on longer timescales and impact the temperature of the Earth. Warming related to a doubling of CO2 including all short- and long-term feedbacks is the Earth-system climate sensitivity. For this study, we evaluate the Earth-system climate sensitivity by reconstructing middle and early Pliocene CO2 concentrations when global temperatures were ~3 to 4oC warmer than pre-industrial conditions. We demonstrate that only a minor change in CO2 was associated with substantial global warming ~4.5 million years ago, with CO2 levels in the range of ~365 to 415 ppm during peak temperatures. Given estimates of global temperatures during the Pliocene, our results support a high Earth-system climate sensitivity for at least the past ~5 million."


Caption for Image: "Estimated CO2 trends considering probable oceanographic changes at each site. Each line represents a modified CO2slope for each site and the dashed green line (1012(alt)) represents an alternative nutrient scenario for Site 1012 (Supplementary Information). Vertical grey lines intersect CO2 concentrations at 3.0–3.3 and 4.0–4.2 Myr, the time intervals representing the Earth-system climate sensitivity estimates presented in the text."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #189 on: May 17, 2014, 12:55:08 AM »
In his latest May post, Robert Scribbler discusses:

"A Faustian Bargain on the Short Road to Hell: Living in a World at 480 CO2e
On the highway to a smokestack hell, Faust met a devil who said to him:
“Give me all your tomorrows, all your children and all your children’s children, and I will make this one day, for you, a paradise.”"

From this post, at the following link, I extract the following quotes

https://robertscribbler.wordpress.com/tag/earth-systems-sensitivity/

Quotes: "Fortunately for our exploration, there’s been a bit of work done on just this subject. Last year, MIT’s Advanced Global Atmospheric Gasses Experiment issued a report describing model data that determined the current CO2 equivalent forcing from all of the more than 50 greenhouse contributing trace gasses in the atmosphere. And the results were somewhat disconcerting. As of June of 2013, that amount was equal to 478 parts per million CO2. Or a CO2e of 478 parts per million when all the other greenhouse gasses were added to the already high and rapidly rising levels of CO2. Adding in the current rate of CO2 rise, we end up with about 480 parts per million of CO2e from all greenhouse gasses by this year. So if we’re talking about the total burden of all greenhouse gasses and the one that will be with us through the long term, 480 is, unfortunately, the number we should be dealing with and not 400.
….
So subtracting out the net effect of sulfates and other aerosols brings us to a total net forcing from all factors related to human changes to the atmosphere of about 425 ppm CO2e. A rather disturbing final number both due to its departure over the current 400 ppm CO2 value and due to the fact that though most greenhouse gasses have atmospheric residence times of decades to centuries, the cooling sulfates would likely last for 1-2 years before falling out entirely. This means that once fossil emissions stop, we may as well just add +55 ppm CO2e to the current total.
…..
Under the current regime, a CO2e of about 550 ppm, enough to warm the Earth between 5-6 C long term, is locked in within 25-30 years. A climate state that pushes the risk of a mini-runaway to moderate. Meanwhile, levels that would almost certainly set off a Permian or PETM type, anoxic ocean, extinction event, at around 800 ppm CO2e, become possible under BAU by 2060-2080."

While Robert Scribbler's summary of our current Faustian hell give in the prior quotes is bad enough, I would like to point out that from a public safety point of view it is non-conservative in that:
1. The GWP for methane is currently closer to 35 than to 25.
2. It is quite possible that ECS is closer to 4.5 than to 3
3. It is quite possible that ESS is closer to 9 than to 6
4. It is quite possible that society will follow a BAU emission path into the 2060-2080 timeframe.
5. It is very likely that we are entering a 15 to 30-year positive PDO/IPO phase which could temporary accelerate mean global warming in the coming critical timeframe.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #190 on: May 17, 2014, 01:42:47 AM »
In the following quote, from the linked website, Robert Howarth warns that using natural gas (whether conventional or unconventional) as a bridge fuel to future renewables is ill advised:

http://mediarelations.cornell.edu/2014/05/14/control-methane-now-greenhouse-gas-expert-warns/

Quote: "“We have to control methane immediately, and natural gas is the largest methane pollution source in the United States,” said Howarth, who explains in an upcoming journal article that Earth may reach the point of no return if average global temperatures rise by 1.5 to 2 degrees Celsius in future decades. “If we hit a climate-system tipping point because of methane, our carbon dioxide problem is immaterial. We have to get a handle on methane, or increasingly risk global catastrophe.”

Howarth’s study, “A Bridge to Nowhere: Methane Emissions and the Greenhouse Gas Footprint of Natural Gas,” will be published May 20 in the journal Energy Science and Engineering."

see also related information at the following link:

http://www.climatecentral.org/news/fracking-methane-emissions-catastrophe-17439
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #191 on: May 19, 2014, 04:52:36 PM »
As I have previously discussed both in this thread, and recently in the WAIS Collapse thread, the linked reference confirms that aerosol precursors from forests play an important part in currently partially suppressing mean global temperatures (due to cloud formation); however, as forests are projected to sustain possibly severe stress from climate change; this temporary climate change masking factor (forest emitted aerosol precursors) may start to decline in a few decades:

Francesco Riccobono, Siegfried Schobesberger, Catherine E. Scott, Josef Dommen, Ismael K. Ortega, Linda Rondo, João Almeida, Antonio Amorim, Federico Bianchi, Martin Breitenlechner, André David, Andrew Downard, Eimear M. Dunne, Jonathan Duplissy, Sebastian Ehrhart, Richard C. Flagan, Alessandro Franchin, Armin Hansel, Heikki Junninen, Maija Kajos, Helmi Keskinen, Agnieszka Kupc, Andreas Kürten,Alexander N. Kvashin, Ari Laaksonen, Katrianne Lehtipalo, Vladimir Makhmutov, Serge Mathot, Tuomo Nieminen, Antti Onnela, Tuukka Petäjä, Arnaud P. Praplan, Filipe D. Santos, Simon Schallhart, John H. Seinfeld, Mikko Sipilä, Dominick V. Spracklen, Yuri Stozhkov, Frank Stratmann, Antonio Tomé, Georgios Tsagkogeorgas, Petri Vaattovaara, Yrjö Viisanen, Aron Vrtala, Paul E. Wagner, Ernest Weingartner, Heike Wex, Daniela Wimmer, Kenneth S. Carslaw, Joachim Curtius, Neil M. Donahue, Jasper Kirkby, Markku Kulmala, Douglas R. Worsnop and Urs Baltensperger, (2014), "Oxidation Products of Biogenic Emissions Contribute to Nucleation of Atmospheric Particles",  Science 16 May 2014: Vol. 344 no. 6185 pp. 717-721. DOI: 10.1126/science.1243527

http://www.sciencemag.org/content/344/6185/717


Abstract: "Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #192 on: May 19, 2014, 11:13:00 PM »
The following reference information about the need to reduce methane emissions is a follow-up to my Reply #190:

Howarth, R. W. (2014), A bridge to nowhere: methane emissions and the greenhouse gas footprint of natural gas. Energy Science & Engineering. doi: 10.1002/ese3.35

http://onlinelibrary.wiley.com/doi/10.1002/ese3.35/abstract;jsessionid=D9EA215506FD37FF01FEF2E04CD8E3B8.f04t01

http://onlinelibrary.wiley.com/enhanced/doi/10.1002/ese3.35

Abstract: "In April 2011, we published the first peer-reviewed analysis of the greenhouse gas footprint (GHG) of shale gas, concluding that the climate impact of shale gas may be worse than that of other fossil fuels such as coal and oil because of methane emissions. We noted the poor quality of publicly available data to support our analysis and called for further research. Our paper spurred a large increase in research and analysis, including several new studies that have better measured methane emissions from natural gas systems. Here, I review this new research in the context of our 2011 paper and the fifth assessment from the Intergovernmental Panel on Climate Change released in 2013. The best data available now indicate that our estimates of methane emission from both shale gas and conventional natural gas were relatively robust. Using these new, best available data and a 20-year time period for comparing the warming potential of methane to carbon dioxide, the conclusion stands that both shale gas and conventional natural gas have a larger GHG than do coal or oil, for any possible use of natural gas and particularly for the primary uses of residential and commercial heating. The 20-year time period is appropriate because of the urgent need to reduce methane emissions over the coming 15–35 years."
« Last Edit: May 20, 2014, 09:05:17 PM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #193 on: May 20, 2014, 05:45:04 PM »
At the following link, werther, posts that attached methane plot observed a Barrow, Alaska, and he noted the rise in methane emissions this year and in the previous El Nino years of '94, '98 and '04.  This could spell bad news if the current positive phase of the PDO/IPO brings more frequent El Nino events for the next 15 to 20-years.

http://forum.arctic-sea-ice.net/index.php/topic,872.0.html
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #194 on: May 22, 2014, 04:01:43 PM »
The linked reference (with a free access pdf) cites that nanoparticulate iron from ice sheet meltwater can stimulate plankton growth; which theoretically could help to absorb more CO₂ (particularly in the short-term).  However, if ocean acidification eventually suppresses CO₂ sequestration by plankton then this short-term negative feedback mechanism could eventually turn into a positive feedback mechanism for global warming:

Jon R. Hawkings, Jemma L. Wadham, Martyn Tranter, Rob Raiswell, Liane G. Benning, Peter J. Statham, Andrew Tedstone, Peter Nienow, Katherine Lee & Jon Telling, (2014), "Ice sheets as a significant source of highly reactive nanoparticulate iron to the oceans", NATURE COMMUNICATIONS | 5:3929 | DOI: 10.1038/ncomms4929

http://www.nature.com/ncomms/2014/140521/ncomms4929/full/ncomms4929.html

Abstract: "The Greenland and Antarctic Ice Sheets cover ~\n10% of global land surface, but are rarely considered as active components of the global iron cycle. The ocean waters around both ice sheets harbour highly productive coastal ecosystems, many of which are iron limited. Measurements of iron concentrations in subglacial runoff from a large Greenland Ice Sheet catchment reveal the potential for globally significant export of labile iron fractions to the near-coastal euphotic zone. We estimate that the flux of bioavailable iron associated with glacial runoff is 0.40–2.54 Tg per year in Greenland and 0.06–0.17 Tg per year in Antarctica. Iron fluxes are dominated by a highly reactive and potentially bioavailable nanoparticulate suspended sediment fraction, similar to that identified in Antarctic icebergs. Estimates of labile iron fluxes in meltwater are comparable with aeolian dust fluxes to the oceans surrounding Greenland and Antarctica, and are similarly expected to increase in a warming climate with enhanced melting."

Also, see the Trends of the Southern Ocean about recent specific measurements of iron released from Antarctic ice sheet melt-water into the Southern Ocean.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #195 on: May 22, 2014, 08:37:13 PM »
As a follow-on to by Reply #173, I would like to cite the following linked reference (with free access pdf) that notes that public interest in climate change has decreased continuously since 2007 (see also the attached image and associate caption).  Without public interest it is difficult for me to see how decision makers will move society very much off of out current BAU pathway, indicating that we should at a minimum be considering ice mass loss scenarios for RCP 8.5:

William R L Anderegg and Gregory R Goldsmith, (2014),"Public interest in climate change over the past decade and the effects of the 'climategate' media event", Environ. Res. Lett. 9 054005, doi:10.1088/1748-9326/9/5/054005

http://iopscience.iop.org/1748-9326/9/5/054005/article

Abstract: "Despite overwhelming scientific consensus concerning anthropogenic climate change, many in the non-expert public perceive climate change as debated and contentious. There is concern that two recent high-profile media events—the hacking of the University of East Anglia emails and the Himalayan glacier melt rate presented in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change—may have altered public opinion of climate change. While survey data is valuable for tracking public perception and opinion over time, including in response to climate-related media events, emerging methods that facilitate rapid assessment of spatial and temporal patterns in public interest and opinion could be exceptionally valuable for understanding and responding to these events' effects. We use a novel, freely-available dataset of worldwide web search term volumes to assess temporal patterns of interest in climate change over the past ten years, with a particular focus on looking at indicators of climate change skepticism around the high-profile media events. We find that both around the world and in the US, the public searches for the issue as 'global warming,' rather than 'climate change,' and that search volumes have been declining since a 2007 peak. We observe high, but transient spikes of search terms indicating skepticism around the two media events, but find no evidence of effects lasting more than a few months. Our results indicate that while such media events are visible in the short-term, they have little effect on salience of skeptical climate search terms on longer time-scales."

Caption: "Princeton University and University of Oxford researchers found that negative media reports seem to have only a passing effect on public opinion, but that positive stories don't appear to possess much staying power, either. Measured by how often people worldwide scour the Internet for information related to climate change, overall public interest in the topic has steadily waned since 2007. To gauge public interest, the researchers used Google Trends to document the Internet search-engine activity for "global warming" (blue line) and "climate change" (red line) from 2004 to 2013. They examined activity both globally (top) and in the United States (bottom). The numbers on the left indicate how often people looked up each term based on its percentage of the maximum search volume at any given point in time. Credit: William Anderegg"
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #196 on: May 22, 2014, 08:46:33 PM »
As a follow-up to my Reply #195:

The linked reference with a free pdf (and associated quotes) indicates that most scientists err on the side of least drama (ESLD), which is in fact a scientific basis; which to be indicates that the public will not likely be roused from their current lack of interest in climate change, until they directly experience the impacts of climate change; as the ESLD model projections for climate change may not give them adequate information to take appropriate Precaution Principle actions to guard against the most severe climate change; therefore, we should likely consider RCP8.5 (BAU) as the most likely scenario for projecting ice mass loss from the WAIS this century:

Keynyn Brysse, Naomi Oreskes, Jessica O'Reilly, and Michael Oppenheimer, (2013), "Climate Change Prediction: Erring on the Side of Least Drama?", Global Environmental Change, Vol: 23, Issue 1, pp 327-337; http://dx.doi.org/10.1016/j.gloenvcha.2012.10.008

http://www.sciencedirect.com/science/article/pii/S0959378012001215

See the following link for the free pdf:

http://www.mudcitypress.com/PDF/leastdrama.pdf

Quote: "The directional bias toward erring on the side of least drama may act in opposition to what has become an important guideline in environmental policy in some institutions and governments: the precautionary principle. There are many different formulations and interpretations of the precautionary principle, both weak and strong, but generally speaking, the principle is interpreted in the context of climate change to mean that action in the face of potentially serious and/or irreversible climate risks should not have to wait for complete scientific certainty to be attained (an impossibility in any event). The United Nations Rio Declaration on Environment and Development, for example, defines the precautionary principle this way: ‘‘Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation’’ (UNEP, 1992, p. 3). While the costs of acting in the face of uncertainty must also be taken into account (Gollier, 2002), the precautionary principle suggests that the international climate change community should prepare for the worst while hoping for the best.  If climate scientists and assessors are erring on the side of least drama in their predictions, then they are not preparing policymakers and the public for the worst, because they are under predicting what the worst outcomes might be."

Dr. Oreskes states:
“What we’re proposing is that the core values of science, the core values of the scientific community — rationality, objectivity, dispassion, restraint, moderation — actually introduce a bias into scientific evaluation in cases where some possible outcomes are, in fact, dramatic.
“And that when scientists encounter outcomes that are potentially quite dramatic — or even potentially alarming — that it actually makes them uncomfortable. And they have a tendency, and I would argue subconsciously, to emphasize the more cautious range of their data, erring on the side of least drama. Erring on the side of the data that seems less dramatic and less alarming.
“The argument of the paper is that, this is really a problem, a source of bias.”
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #197 on: May 23, 2014, 01:39:10 AM »
The linked reference (with a free access pdf) discusses the findings of several simulations of the Pliocene climate. The Pliocene climate is possibly the closest paleo example of GHG and Earth System conditions to the situation that the world is currently moving towards.  Lessons learned from the study include that polar amplification (see the first attached image) is one of the dominate reasons for higher mean global temperatures during this period, and that this amplification was largely related to reductions in clear sky albedo (see the second attached image), due to such factors as reduction in Arctic Sea Ice and increases in high latitude vegetation.  As most GCM treat such changes in albedo as slow response factors that do not have a big impact this century, we should all be concerned that the lessons from the Pliocene indicate that polar amplification may make such changes in high-latitude albedo important this century and that GCMs should uses higher Earth System Sensitivity values:

Hill, D. J., Haywood, A. M., Lunt, D. J., Hunter, S. J., Bragg, F. J., Contoux, C., Stepanek, C., Sohl, L., Rosenbloom, N. A., Chan, W.-L., Kamae, Y., Zhang, Z., Abe-Ouchi, A., Chandler, M. A., Jost, A., Lohmann, G., Otto-Bliesner, B. L., Ramstein, G., and Ueda, H.: Evaluating the dominant components of warming in Pliocene climate simulations, Clim. Past, 10, 79-90, doi:10.5194/cp-10-79-2014, 2014.

http://www.clim-past.net/10/79/2014/cp-10-79-2014.html

"Abstract. The Pliocene Model Intercomparison Project (PlioMIP) is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO2 significantly higher than pre-industrial concentrations. The simulations of the mid-Pliocene warm period show global warming of between 1.8 and 3.6 °C above pre-industrial surface air temperatures, with significant polar amplification. Here we perform energy balance calculations on all eight of the coupled ocean–atmosphere simulations within PlioMIP Experiment 2 to evaluate the causes of the increased temperatures and differences between the models. In the tropics simulated warming is dominated by greenhouse gas increases, with the cloud component of planetary albedo enhancing the warming in most of the models, but by widely varying amounts. The responses to mid-Pliocene climate forcing in the Northern Hemisphere midlatitudes are substantially different between the climate models, with the only consistent response being a warming due to increased greenhouse gases. In the high latitudes all the energy balance components become important, but the dominant warming influence comes from the clear sky albedo, only partially offset by the increases in the cooling impact of cloud albedo. This demonstrates the importance of specified ice sheet and high latitude vegetation boundary conditions and simulated sea ice and snow albedo feedbacks. The largest components in the overall uncertainty are associated with clouds in the tropics and polar clear sky albedo, particularly in sea ice regions. These simulations show that albedo feedbacks, particularly those of sea ice and ice sheets, provide the most significant enhancements to high latitude warming in the Pliocene."
« Last Edit: May 23, 2014, 01:45:29 AM 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: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #198 on: May 23, 2014, 05:07:37 PM »
Given the critical importance of the current thawing of the permafrost, I post a long extract from the following linked article, indicating that the Arctic permafrost is more subject to degradation that many scientists previously thought, because the permafrost is not continuous (obviously accelerated GHG emissions from degraded permafrost would accelerate forcing on ice mass loss):

http://innovations.coe.berkeley.edu/vol7-issue8-feb2014/studying-the-arctic-tundra.html

Extract:
"The Arctic is critical to understanding the global climate. About half the carbon stored in the Earth’s soil is in the Arctic, where organic matter is locked in place by permanently frozen subsoil. As those regions thaw, the worry is that tiny microbes will start feeding on the long-stored organic material and start releasing large quantities of greenhouse gases.
“Our goal is to understand the structure beneath the subsurface,” says Hubbard. “How thick is the active layer? How thick is the permafrost? What are the variations in moisture content and geochemistry, and how do those variations influence greenhouse gas generation?”
Hubbard’s team is using geophysical tools—seismic, radar and electrical—to determine what’s beneath the ground. They also collect core samples that are analyzed back in Berkeley.
In seismic tests, researchers hit the tundra with a sledgehammer to send an acoustic pulse into the ground. The velocity of the pulse is sensitive to physical structure and reveals whether or not the deeper permafrost layers are frozen.
Last year, these seismic tests led to surprising results. Scientists thought the permafrost started about a half-meter below the ground surface and continued for hundreds of meters. But Hubbard’s team discovered unfrozen saline zones, starting about two meters below the top of the permafrost and running many meters deep.
“We chose the Barrow site because it is cold and had continuously frozen permafrost,” says Hubbard, laughing. “And we find out that the northernmost city in North America, with supposedly the most continuous permafrost area, is not really continuous. It could have big implications. There could be microbes right now that are active in this buried, unfrozen zone, with wintertime or even yearlong greenhouse respiration. We will be returning to the site this May to drill deep holes, collect gas samples and test this hypothesis.”
Hubbard’s team is also measuring the subsurface with ground penetrating radar, which sends electromagnetic waves into the ground that bounce off the interface between sublayers. The measurements are taken by pulling radar-equipped sleds across the Arctic tundra, either on foot or behind a snowmobile.
“We’ve found radar to be extremely helpful for mapping the active layer,” says Hubbard. “We’ve been going up there every freeze, winter, thaw and growing season for a few years and measuring the active layer dynamics—basically, the thaw depth.”
They also measure the moisture content, based on the subsurface’s ability to conduct electrical current. This electrical data is taken either by planting electrodes in the ground or pulling an electromagnetic sensor across the tundra.
All of these subsurface measurements of the Barrow Peninsula are critical to understanding how the Arctic is changing. But NGEE-Arctic also seeks to understand the relationship between the changes below ground to the land above.
“We’ve been taking kites mounted with sensors to image the land surface at the same time that we’re imaging the subsurface,” says Hubbard. In the past, they’ve also used landscape data mapped from a twin engine Cessna plane.
The goal is to transfer the knowledge of their detailed subsurface measurements to the scale used in standard climate models. Hubbard’s team measures subsurface features in centimeters, but the smallest element in a climate model is 30x30 kilometers—a million times larger.
“There is a tight coupling of the land surface and the below-ground expression,” says Hubbard. “We would like to be able to infer a lot about the subsurface from measuring the micro-topography. That would really help us to parameterize this big climate model, because it is easy to acquire topographic measurements.”
NGEE-Arctic is an ambitious, 10-year study that’s funded by the Department of Energy. Despite the harsh conditions of the fieldwork, scientists are very excited about the project."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #199 on: May 24, 2014, 01:29:50 AM »
Most likely the cited positive feedback factor associated with burial-nutrient in the ocean is a true slow respond feedback, but I wonder how ocean acidification will effect this mechanism:


Roth, R., Ritz, S. P., and Joos, F.: Burial-nutrient feedbacks amplify the sensitivity of carbon dioxide to changes in organic matter remineralisation, Earth Syst. Dynam. Discuss., 5, 473-528, doi:10.5194/esdd-5-473-2014, 2014.


http://www.earth-syst-dynam-discuss.net/5/473/2014/esdd-5-473-2014.pdf


Abstract. Changes in the marine remineralization of particulate organic carbon (POC) and calcium carbonate potentially provide a positive feedback under climate change. The responses to changes in remineralization length scales are systematically mapped with the Bern3D ocean–sediment model for CO2 and tracer fields for which observations and palaeoproxies exist. Spatio-temporal evolutions are captured by empirical orthogonal functions. Results show that the "sediment burial-nutrient feedback" amplifies the initial response in atmospheric CO2 by a factor of four to seven. A temporary imbalance between the weathering flux and the burial of organic matter and calcium carbonate lead to sustained changes the ocean's phosphate and alkalinity inventory and in turn in surface nutrient availability, marine productivity, and atmospheric CO2. It takes decades to centuries to reorganize tracers and fluxes within the ocean, many millennia to approach equilibrium for burial fluxes, while δ13C signatures are still changing 200 000 years after the perturbation. CO2 sensitivity is with 1.7 ppm m−1 about fifty times larger for a unit change in the remineralisation depth of POC than of calcium carbonate. The results highlight the role of organic matter burial for atmospheric CO2 and the substantial impacts of seemingly small changes in POC remineralisation.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson