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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #300 on: September 16, 2014, 12:27:46 AM »
The linked reference with a free pdf, indicates that GCM models calibrated to the Pliocene, indicate that high latitude albedo feedbacks were the most important positive feedback mechanisms for global warming in that period (which may serve as a model for where the Earth's climate is headed):

Hill, DJ, Haywood, AM, Hunter, SJ, Lunt, DJ, Bragg, FJ, Contoux, C, Ramstein, G, Jost, A, Stepanek, C, Lohmann, G, Sohl, L, Chandler, MA, Rosenbloom, NA, Otto-Bliesner, BL, Chan, W-L, Abe-Ouchi, A, Kamae, Y, Ueda, H and Zhang, Z (2014) Evaluating the dominant components of warming in Pliocene climate simulations. Climate of the Past, 10 (1). 79 - 90. ISSN 1814-9324

http://eprints.whiterose.ac.uk/80157/1/Evaluating%20the%20dominant%20components%20of%20warming%20in%20Pliocene.pdf

Abstract: "The Pliocene Model Intercomparison Project (PlioMIP) is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO 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."
“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 #301 on: September 18, 2014, 11:51:24 PM »
The reference cited below indicates that atmospheric hydroxyl-radical concentrations are about the same in the Northern and Southern Hemispheres.  This is bad news as it implies that methane emissions in the Northern Hemisphere are likely higher than researchers have previously assumed (as it was expected that the Northern Hemisphere would have more hydroxyl-radicals than the Southern Hemisphere, and it appears likely that greenhouse gases such as methane are consuming part of store of atmospheric hydroxyl-radicals in the Northern Hemisphere).

P. K. Patra, M.C. Krol, S. A. Montzka, T. Arnold, E. L. Atlas, B.R. Lintner, B.B. Stephens, B. Xiang, J. W. Elkins, P. J. Fraser, A. Ghosh, E. J. Hintsa, D. F. Hurst, K. Ishijima, P. B. Krummel, B.R. Miller, K. Miyazaki, F.L. Moore, J. Mühle, S. O’Doherty, R.G. Prinn, L.P. Steele, M. Takigawa, . J. Wang, R.F. Weiss, S.C. Wofsy, and D. Young, (2014), "Observational evidence for interhemispheric hydroxyl-radical parity", Nature, doi:10.1038/nature13721


http://www2.ucar.edu/atmosnews/just-published/12346/wheres-atmospheres-self-cleaning-power

Excerpt: "The results indicate that the northern/southern hemisphere ratio of OH is nearly equivalent at about .97, plus or minus .12. In contrast, state-of-the-art models have predicted an OH concentration that is 13-42% higher in the Northern Hemisphere.
The ratio is significant as scientists have relied on OH concentration to estimate emissions of certain gases, such as methane and carbon monoxide. The estimates of these emissions in the Northern Hemisphere may need to be revised if concentrations of OH are approximately the same as in the Southern Hemisphere, the authors said."

See also:
http://m.phys.org/news/2014-09-evidence-interhemispheric-hydroxyl-parity.html

This topic and paper are both discussed further in the Science folder, in the "hydroxyl missing ..." thread
“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 #302 on: September 19, 2014, 12:07:03 AM »
Jai Mitchell posted that there is an error in the signs of the terms in the following reference; however, as I do not know whether that is true, or not, I have decided to post the linked reference as it discusses potentially important absorbed solar radiation (ASR) – Arctic sea ice concentration (SIC) relationship. This ASR-SIC relationship is currently not represented in most of the current climate models, and thus the majority of GCM projections may possibly underestimate the important positive feedback mechanism of Arctic amplification, and if true this would mean that they underestimate projections of future increases in mean global warming:

Yong-Sang Choi, Baek-Min Kim, Sun-Kyong Hur, Seong-Joong Kim, Joo-Hong Kim and Chang-Hoi Ho, (2014), "Connecting early summer cloud-controlled sunlight and late summer sea ice in the Arctic", Journal of Geophysical Research Atmospheres DOI: 10.1002/2014JD022013

http://onlinelibrary.wiley.com/doi/10.1002/2014JD022013/abstract

Abstract: "This study demonstrates that absorbed solar radiation (ASR) at the top of the atmosphere in early summer (May–July) plays a precursory role in determining the Arctic sea ice concentration (SIC) in late summer (August–October). The monthly ASR anomalies are obtained over the Arctic Ocean (65°N–90°N) from the Clouds and the Earth's Radiant Energy System during 2000–2013. The ASR changes primarily with cloud variation. We found that the ASR anomaly in early summer is significantly correlated with the SIC anomaly in late summer (correlation coefficient, r  ≈ −0.8 with a lag of 1 to 4 months). The region exhibiting high (low) ASR anomalies and low (high) SIC anomalies varies yearly. The possible reason is that the solar heat input to ice is most effectively affected by the cloud shielding effect under the maximum TOA solar radiation in June and amplified by the ice-albedo feedback. This intimate delayed ASR-SIC relationship is not represented in most of current climate models. Rather, the models tend to over-emphasize internal sea ice processes in summer."

Edit: jai mitchell subsequently indicated that the signs in the original article are correct.
« Last Edit: October 19, 2014, 05:17:44 PM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #303 on: September 19, 2014, 02:17:26 AM »
The linked reference states: "There is an 80% probability that world population, now 7.2 billion, will increase to between 9.6 and 12.3 billion in 2100."  This is a clear increase over estimates from only a few months ago, and indicates that there is very little likelihood that anthropogenic radiative force will slow anytime soon; however, it very well may accelerate:

Patrick Gerland, Adrian E. Raftery, Hana Ševčíková, Nan Li, Danan Gu, Thomas Spoorenberg, Leontine Alkema, Bailey K. Fosdick, Jennifer Chunn, Nevena Lalic, Guiomar Bay, Thomas Buettner, Gerhard K. Heilig, & John Wilmoth, (2014), "World population stabilization unlikely this century", Science DOI: 10.1126/science.1257469 

http://www.sciencemag.org/content/early/2014/09/17/science.1257469

Abstract: "The United Nations recently released population projections based on data until 2012 and a Bayesian probabilistic methodology. Analysis of these data reveals that, contrary to previous literature, world population is unlikely to stop growing this century. There is an 80% probability that world population, now 7.2 billion, will increase to between 9.6 and 12.3 billion in 2100. This uncertainty is much smaller than the range from the traditional UN high and low variants. Much of the increase is expected to happen in Africa, in part due to higher fertility and a recent slowdown in the pace of fertility decline. Also, the ratio of working age people to older people is likely to decline substantially in all countries, even those that currently have young populations."

edit: attached is a related graphic produced by the Guardian
« Last Edit: September 19, 2014, 07:44:08 PM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #304 on: September 22, 2014, 07:31:55 PM »
The first post in this thread provides a graph of historical emissions through 2012 vs the RCP scenarios indicating that we were following RCP 8.5.  The attached image from the following link indicates that we are going to continue following RCP 8.5 through at least 2014:

http://www.globalcarbonproject.org/carbonbudget/14/files/GCP_budget_2014_v1.0_lowres.pdf

See also:

P. Friedlingstein, R. M. Andrew, J. Rogelj, G. P. Peters, J. G. Canadell, R. Knutti, G. Luderer, M. R. Raupach, M. Schaeffer, D. P. van Vuuren, & C. Le Quéré, (2014), "Persistent growth of CO2 emissions and implications for reaching climate targets", Nature Geoscience, doi:10.1038/ngeo2248

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2248.html


Abstract: "Efforts to limit climate change below a given temperature level require that global emissions of CO2 cumulated over time remain below a limited quota. This quota varies depending on the temperature level, the desired probability of staying below this level and the contributions of other gases. In spite of this restriction, global emissions of CO2 from fossil fuel combustion and cement production have continued to grow by 2.5% per year on average over the past decade. Two thirds of the CO2 emission quota consistent with a 2 °C temperature limit has already been used, and the total quota will likely be exhausted in a further 30 years at the 2014 emissions rates. We show that CO2 emissions track the high end of the latest generation of emissions scenarios, due to lower than anticipated carbon intensity improvements of emerging economies and higher global gross domestic product growth. In the absence of more stringent mitigation, these trends are set to continue and further reduce the remaining quota until the onset of a potential new climate agreement in 2020. Breaking current emission trends in the short term is key to retaining credible climate targets within a rapidly diminishing emission quota."
“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 #305 on: September 22, 2014, 10:46:19 PM »
As a follow-up to my post in Reply #313 (which is dependent on Fuss et al 2014 for much of its information), the following linked reference (& associated attached image); indicates just how much the current low range RCP scenarios are dependent upon Bioenergy with carbon capture and storage (BECCS) to achieve their stated goals (which the article indicates is quite a gamble).  Furthermore, the figure only shows CO₂ emissions and does not address other radiative forcing factors such as: black carbon, methane, HFC's, and future reductions in natural absorption of CO₂ by the ocean and/or land; nor do the mean global temperature increase projections include the probability that ECS may be meaningfully higher than 3.0.

Sabine Fuss, Josep G. Canadell, Glen P. Peters, Massimo Tavoni, Robbie M. Andrew, Philippe Ciais, Robert B. Jackson, Chris D. Jones, Florian Kraxner, Nebosja Nakicenovic, Corinne Le Quéré, Michael R. Raupach, Ayyoob Sharifi, Pete Smith & Yoshiki Yamagata, (2014), "Betting on negative emissions", Nature Climate Change, doi:10.1038/nclimate2392

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2392.html

Abstract: "Bioenergy with carbon capture and storage could be used to remove carbon dioxide from the atmosphere. However, its credibility as a climate change mitigation option is unproven and its widespread deployment in climate stabilization scenarios might become a dangerous distraction."
« Last Edit: September 22, 2014, 10:54:51 PM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #306 on: September 22, 2014, 11:55:17 PM »
The linked reference (with an open access pdf), indicates that the ability of land and ocean to act as a sink for CO₂ (ks) is being reduced; with intrinsic mechanisms causing ks to decline more strongly under high-emission, low-mitigation scenarios (such as RCP 8.5) as the carbon–climate system is perturbed further from a near-linear regime.  Furthermore, as we enter a period of more frequent, and typically stronger, El Nino events, we can expect ks to decline even further due to the adverse effect of El Nino events on tropical land vegetation:

M. R. Raupach, M. Gloor, J. L. Sarmiento, J. G. Canadell, T. L. Frölicher, T. Gasser, R. A. Houghton, C. Le Quéré, and C. M. Trudinger, (2014), "The declining uptake rate of atmospheric CO2 by land and ocean sinks", Biogeosciences, 11, 3453–3475, doi:10.5194/bg-11-3453-2014

http://www.biogeosciences.net/11/3453/2014/bg-11-3453-2014.pdf

Abstract: "Through 1959–2012, an airborne fraction (AF) of 0.44 of total anthropogenic CO2 emissions remained in the atmosphere, with the rest being taken up by land and ocean CO2 sinks. Understanding of this uptake is critical because it greatly alleviates the emissions reductions required for climate mitigation, and also reduces the risks and damages that adaptation has to embrace. An observable quantity that reflects sink properties more directly than the AF is the CO2 sink rate (ks), the combined land–ocean CO₂ sink flux per unit excess atmospheric CO2 above preindustrial levels. Here we show from observations that ks declined over 1959–2012 by a factor of about 1/3, implying that CO2 sinks increased more slowly than excess CO2. Using a carbon–climate model, we attribute the decline in ks to four mechanisms: slower-than-exponential CO2 emissions growth (~35% of the trend), volcanic eruptions (~25 %), sink responses to climate change (~20 %), and nonlinear responses to increasing CO2, mainly oceanic (~20 %). The first of these mechanisms is associated purely with the trajectory of extrinsic forcing, and the last two with intrinsic, feedback responses of sink processes to changes in climate and atmospheric CO2. Our results suggest that the effects of these intrinsic, nonlinear responses are already detectable in the global carbon cycle. Although continuing future decreases in ks will occur under all plausible CO2 emission scenarios, the rate of decline varies between scenarios in non-intuitive ways because extrinsic and intrinsic mechanisms respond in opposite ways to changes in emissions: extrinsic mechanisms cause ks to decline more strongly with increasing mitigation, while intrinsic mechanisms cause ks to decline more strongly under high-emission, low-mitigation scenarios as the carbon–climate system is perturbed further from a near-linear regime."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #307 on: September 23, 2014, 02:06:34 AM »
The following reference and the associated extract and attached image indicate that mean global temperature would have increased, during the recent hiatus period, at the rate projected by CMIP5 if not for the variable factors cited below (eg ENSO, volcanoes and incorrect mean global temperature measurements):

Markus Huber & Reto Knutti, (2014), "Natural variability, radiative forcing and climate response in the recent hiatus reconciled", Nature Geoscience, Volume: 7, Pages: 651–656, doi:10.1038/ngeo2228

http://www.nature.com/ngeo/journal/v7/n9/full/ngeo2228.html


Abstract: "Global mean surface warming over the past 15 years or so has been less than in earlier decades and than simulated by most climate models. Natural variability, a reduced radiative forcing, a smaller warming response to atmospheric carbon dioxide concentrations and coverage bias in the observations have been identified as potential causes. However, the explanations of the so-called ‘warming hiatus’ remain fragmented and the implications for long-term temperature projections are unclear. Here we estimate the contribution of internal variability associated with the El Niño/Southern Oscillation (ENSO) using segments of unforced climate model control simulations that match the observed climate variability. We find that ENSO variability analogous to that between 1997 or 1998 and 2012 leads to a cooling trend of about −0.06 °C. In addition, updated solar and stratospheric aerosol forcings from observations explain a cooling trend of similar magnitude (−0.07 °C). Accounting for these adjusted trends we show that a climate model of reduced complexity with a transient climate response of about 1.8 °C is consistent with the temperature record of the past 15 years, as is the ensemble mean of the models in the Coupled Model Intercomparison Project Phase 5 (CMIP5). We conclude that there is little evidence for a systematic overestimation of the temperature response to increasing atmospheric CO2 concentrations in the CMIP5 ensemble."

The following extract and caption for the attached image are from the following related Internet article:

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/aug/25/unpacking-unpaused-global-warming-climate-models-right

Extract: "Putting it all together, we have 0.17°C observed surface warming according to Cowtan & Way, and 0.13°C cooling from natural influences. If those natural factors hadn’t caused cooling since 1998, we would have seen 0.3°C global surface warming, right in line with climate model projections."

Figure Caption: "Mean of CMIP5 climate model ensemble surface temperature projections unadjusted (dotted orange) and adjusted for internal variability & external forcings (solid orange), vs. Met Office (solid black) and Cowtan & Way (dashed black) observed surface temperatures. Source; Nature Geoscience; Huber & Knutti (2014)."

Also see:
http://andthentheresphysics.wordpress.com/2014/08/19/understaning-the-pause/
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #308 on: September 23, 2014, 07:58:52 PM »
As a follow-up to my Reply #316, I would like to point-out that just because Huber & Knutti (2014) found that by correcting for ENSO, volcanoes, Cowtan & Way, that they found a good correlation between CMIP5 mean global temperature projections using an ECS of 3 degree C; does not mean: (a) that the ECS is currently 3 degree C; nor (b) the climate sensitivity will not increase significantly before the end of this century.

Reasons to suspect that ECS may be currently higher than 3 degrees C include (but are not limited to):
(a) The AMO is currently in a cooling phase, which Huber & Knutti did not correct for; & if they had then they would need a higher ECS to get the CMIP5 projections to match their corrected values.
(b) The ozone hole over Antarctica is venting heat into space; and as this heals itself austral summer temperature will be higher.
(c) The current slightly warmer temps and slightly high atmospheric CO2 concentrations are resulting in higher plant growth rates particularly in the tundra and deserts, which is resulting in unusually high CO2 absorption, and also unusually high secondary organic aerosol (SOA) emissions by boreal forests and shrubs that are temporarily reducing measured temperature increases; but will reverse to become positive feedback factors as temperature increases cause heat stress to these plants.
(d) The CMIP5 models assume that ECS should be applied uniformly around the globe, but Shindell (2014) showed that this is incorrect, and that making this mistake masks the fact that the ECS is higher than assumed.
(e) Asian & African air pollution is a stronger negative feedback than the CMIP5 models assume; thus as this air pollution is cleaned-up the true magnitude of the ECS will be revealed.

Reasons to suspect that the ECS will increase with time before the end of the century include (but are not limited to):
(a) Degradation of the permafrost is accelerating, which will increase both CO2, and methane, emissions.
(b) Degradation of methane hydrates will accelerate with time.
(c) The arctic sea ice will degrade faster than the CMIP5 assumes, which will decrease the albedo effect in this region.
(d) Wildfires and black carbon emissions are increasing; which will also decrease regional albedo.
(e) The oceans are shows signs that they will absorb less net CO2 in the future.
(d) The probable coming synchronization of the PDO/IPO and the AMO will promote El Nino like conditions that will result in distress of tropic plants that will increase ECS.

“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 #309 on: September 23, 2014, 08:20:05 PM »
The first linked article (and associated attached image) indicates that in 2013 the rate of Amazon deforestation has started to increase again; while the second linked article indicates that Brazil will refuse to participate in the UN's proposed new anti-deforestation plan; which are both bad news for climate change.

http://www.theguardian.com/environment/2014/sep/11/amazon-deforestation-jumps

http://www.ibtimes.co.uk/brazil-says-no-anti-deforestation-plans-difficulty-global-response-climate-change-1466803

Furthermore, most deforestation projections do not adequately consider the impact of growing human populations in primarily tropical rain forest areas (or Africa, South America, and Asia); as these additional people will likely degrade the tropical rain forests in order to maintain a minimum standard of living.

All of these considerations will contribute to higher global temperatures in the future than currently projected.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #310 on: September 23, 2014, 08:36:28 PM »
According to the linked articles, and the following references, sea ice extracts CO₂ from the atmosphere; thus the coming reduction in sea ice (first in the Arctic and some decades later in the Antarctic) will result in an increase in atmospheric CO₂.

http://www.sdu.dk/en/Om_SDU/Fakulteterne/Naturvidenskab/Nyheder/2014_09_22_seaice

http://www.reportingclimatescience.com/news-stories/article/arctic-sea-ice-removes-co2-from-atmosphere.html

References:
The relative contributions of biological and abiotic processes to carbon dynamics in subarctic sea ice, Polar Biology: Dorte Haubjerg Søgaard, David N. Thomas, Søren Rysgaard, Ronnie Nøhr Glud, Louiza Norman, Hermanni Kaartokallio, Thomas Juul-Pedersen, Nicolas-Xavier Geilfus. doi 10.1007/s00300-013-1396-3.
Ikaite crystal distribution in winter sea ice and implications for CO2 system dynamics, The Cryosphere: S. Rysgaard, D. H. Søgaard, M. Cooper, M. Pućko, K. Lennert, T. N. Papakyriakou, F. Wang, N. X. Geilfus, R. N. Glud, J. Ehn, D. F. McGinnis, K. Attard, J. Sievers, J. W. Deming, and D. Barber. doi:10.5194/tc-7-707-2013.
Frost flowers on young Arctic sea ice, The climatic, chemical and microbial significance of an emerging ice type, Journal of Geophysical Research Atmospheres: D. G. Barber, J. K. Ehn, M. Pućko, S. Rysgaard,  J. W. Deming,  J. S. Bowman, T. Papakyriakou, R. J. Galley and  D. H. Søgaard. doi: 10.1002/2014JD021736.
Autotrophic and heterotrophic activity in Arctic first-year sea ice: seasonal study from Malene Bight, SW Greenland, Marine Ecology: Dorte Haubjerg Søgaard, Morten Kristensen, Søren Rysgaard, Ronnie Nøhr Glud, Per Juel Hansen, Karen Marie Hilligsøe. doi:10.3354/meps08845.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #311 on: September 25, 2014, 06:35:13 PM »
The linked reference indicates that increased dependence on natural gas will slow the development of renewable technology and thus will not decrease global warming (and if leakage is significant then it could make matters worse):

Christine Shearer et al, (2014), "The effect of natural gas supply on US renewable energy and CO2 emissions", Environ. Res. Lett. 9 094008 doi:10.1088/1748-9326/9/9/094008

http://iopscience.iop.org/1748-9326/9/9/094008/

Abstract: "Increased use of natural gas has been promoted as a means of decarbonizing the US power sector, because of superior generator efficiency and lower CO2 emissions per unit of electricity than coal. We model the effect of different gas supplies on the US power sector and greenhouse gas (GHG) emissions. Across a range of climate policies, we find that abundant natural gas decreases use of both coal and renewable energy technologies in the future. Without a climate policy, overall electricity use also increases as the gas supply increases. With reduced deployment of lower-carbon renewable energies and increased electricity consumption, the effect of higher gas supplies on GHG emissions is small: cumulative emissions 2013–55 in our high gas supply scenario are 2% less than in our low gas supply scenario, when there are no new climate policies and a methane leakage rate of 1.5% is assumed. Assuming leakage rates of 0 or 3% does not substantially alter this finding. In our results, only climate policies bring about a significant reduction in future CO2 emissions within the US electricity sector. Our results suggest that without strong limits on GHG emissions or policies that explicitly encourage renewable electricity, abundant natural gas may actually slow the process of decarbonization, primarily by delaying deployment of renewable energy technologies."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #312 on: September 26, 2014, 12:50:51 AM »
The following link confirms that the Southern Ocean sea ice serves as a sink for CO₂; therefore, as global warming continued and this sea ice extent/volume is reduced, this loss with serve as a positive feedback mechanism:

Bruno Delille, Martin Vancoppenolle, Nicolas-Xavier Geilfus, Bronte Tilbrook, Delphine Lannuzel, Véronique Schoemann, Sylvie Becquevort, Gauthier Carnat, Daniel Delille, Christiane Lancelot, Lei Chou, Gerhard S. Dieckmann & Jean-Louis Tison, (2014), "Southern Ocean CO2 sink: The contribution of the sea ice", Journal of Geophysical Research: Oceans; DOI: 10.1002/2014JC009941

http://onlinelibrary.wiley.com/enhanced/doi/10.1002/2014JC009941/

Abstract: "We report first direct measurements of the partial pressure of CO2 (pCO2) within Antarctic pack sea ice brines and related CO2 fluxes across the air-ice interface. From late winter to summer, brines encased in the ice change from a CO2 large oversaturation, relative to the atmosphere, to a marked undersaturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO2 in the brines is driven by dilution with melting ice, dissolution of carbonate crystals, and net primary production. As the ice warms, its permeability increases, allowing CO2 transfer at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO2. We upscale these observations to the whole Antarctic sea ice cover using the NEMO-LIM3 large-scale sea ice-ocean and provide first estimates of spring and summer CO2 uptake from the atmosphere by Antarctic sea ice. Over the spring-summer period, the Antarctic sea ice cover is a net sink of atmospheric CO2 of 0.029 Pg C, about 58% of the estimated annual uptake from the Southern Ocean. Sea ice then contributes significantly to the sink of CO2 of the Southern Ocean."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #313 on: September 30, 2014, 09:55:56 PM »
The linked reference (with an open access pdf) indicates that zooplankton enhances mixing of the upper ocean.  Thus if excessive ocean acidification adversely affects the zooplankton (possibly by reducing the amount of phytoplankton that the zooplankton might feed on); then increasing atmospheric CO₂ concentrations may reduce the oceans ability to sequester atmospheric heat.  If so this would serve as a positive feedback mechanism that is currently not accounted from in any GCM model.

Wilhelmus, Monica M. and Dabiri, John O. (2014) Observations of large-scale fluid transport by laser-guided plankton aggregations. Physics of Fluids, 26 . Art. No. 101302. ISSN 1070-6631, DOI: http://dx.doi.org/10.1063/1.4895655.

http://authors.library.caltech.edu/50065/7/1.4895655.pdf

Abstract: "Diel vertical migration of plankton has been proposed to affect global ocean circulation to a degree comparable to winds and tides. This biomixing process has never been directly observed, however, due to the inability to predict its occurrence in situ or to reproduce it in a laboratory setting. Furthermore, it has been argued that the energy imparted to the ocean by plankton migrations occurs at the scale of individual organisms, which is too small to impact ocean mixing. We describe the development of a multi-laser guidance system that leverages the phototactic abilities of plankton to achieve controllable vertical migrations concurrently with laser velocimetry of the surrounding flow. Measurements in unstratified fluid show that the hydrodynamic interactions between neighboring swimmers establish an alternate energy transfer route from the small scales of individually migrating plankton to significantly larger scales. Observations of laser-induced vertical migrations of Artemia salina reveal the appearance of a downward jet, which triggers a Kelvin-Helmholtz instability that results in the generation of eddy-like structures with characteristic length scales much larger than the organisms. The measured energy spectrum is consistent with these findings and indicates energy input at large scales, despite the small individual size of the organisms. These results motivate the study of biomixing in the presence of stratification to assess the contribution of migrating zooplankton to local and global ocean dynamics. The laser control methodology developed here enables systematic study of the relevant processes."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #314 on: October 01, 2014, 05:20:03 PM »
The linked research discusses improved modeling of the influence of Black Carbon on global warming:

Øivind Hodnebrog, Gunnar Myhre, & Bjørn H. Samset, (2014), "How shorter black carbon lifetime alters its climate effect", Nature Communications, Volume: 5, Article number: 5065, doi:10.1038/ncomms6065

http://www.nature.com/ncomms/2014/140925/ncomms6065/abs/ncomms6065.html

Abstract: "Black carbon (BC), unlike most aerosol types, absorbs solar radiation. However, the quantification of its climate impact is uncertain and presently under debate. Recently, attention has been drawn both to a likely underestimation of global BC emissions in climate models, and an overestimation of BC at high altitudes. Here we show that doubling present day BC emissions in a model simulation, while reducing BC lifetime based on observational evidence, leaves the direct aerosol effect of BC virtually unchanged. Increased emissions, together with increased wet removal that reduces the lifetime, yields modelled BC vertical profiles that are in strongly improved agreement with recent aircraft observations. Furthermore, we explore the consequences of an altered BC profile in a global circulation model, and show that both the vertical profile of BC and rapid climate adjustments need to be taken into account in order to assess the total climate impact of BC."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #315 on: October 02, 2014, 01:19:38 AM »
Many scientists are concerned that the Earth may be headed towards a Pliocene type of climate this century due to global warming.  The linked reference indicates that changes in cloud cover/albedo for such conditions would rapidly induce the Equatorial Pacific Ocean into a permanent El Nino-like state.  As cloud albedo is a rapid response feedback mechanism, such a change could happen in as little as a few decades from now (say 2040-2050). Permanent El Nino-like conditions would telecommunicate large amounts of heat from the Equatorial Pacific directly to West Antarctica.

N. J. Burls and A. V. Fedorov, (2014), "Simulating Pliocene warmth and a permanent El Niño-like state: the role of cloud albedo", Paleoceanography, DOI: 10.1002/2014PA00264

http://onlinelibrary.wiley.com/doi/10.1002/2014PA002644/abstract

Abstract: "Available evidence suggests that during the early Pliocene (4-5 Ma) the mean east–west sea surface temperature (SST) gradient in the equatorial Pacific Ocean was significantly smaller than today, possibly reaching only 1-2°C. The meridional SST gradients were also substantially weaker, implying an expanded ocean warm pool in low latitudes. Subsequent global cooling led to the establishment of the stronger, modern temperature gradients. Given our understanding of the physical processes that maintain the present-day cold tongue in the east, warm pool in the west and hence sharp temperature contrasts, determining the key factors that maintained early Pliocene climate still presents a challenge for climate theories and models. This study demonstrates how different cloud properties could provide a solution. We show that a reduction in the meridional gradient in cloud albedo can sustain reduced meridional and zonal SST gradients, an expanded warm pool and warmer thermal stratification in the ocean, weaker Hadley and Walker circulations in the atmosphere. Having conducted a range of hypothetical modified cloud albedo experiments, we arrive at our Pliocene simulation, which shows good agreement with proxy SST data from major equatorial and coastal upwelling regions, the tropical warm pool, mid and high latitudes, and available subsurface temperature data. As suggested by the observations, the simulated Pliocene-like climate sustains a robust ENSO despite the reduced mean east–west SST gradient. Our results demonstrate that cloud albedo changes may be a critical element of Pliocene climate and that simulating the meridional SST gradient correctly is central to replicating the geographical patterns of Pliocene warmth."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #316 on: October 02, 2014, 01:46:10 AM »
The linked reference (with an open access pdf) indicates that CO₂ emissions from global primary energy demands will likely be significantly higher by 2020 than currently envisaged by RCP 8.5 (or other such BAU scenarios):

Jarvis, A. and Hewitt, C. N.: The "Business-As-Usual" growth of global primary energy use and carbon dioxide emissions – historical trends and near-term forecasts, Earth Syst. Dynam. Discuss., 5, 1143-1158, doi:10.5194/esdd-5-1143-2014, 2014.

http://www.earth-syst-dynam-discuss.net/5/1143/2014/esdd-5-1143-2014.html

Abstract: "We analyse the global primary energy use and total CO2 emissions time series since 1850 and show that their relative growth rates appear to exhibit periodicity with a fundamental timescale of ~60 years and with significant harmonic behaviour. Quantifying the inertia inherent in these dynamics allows forecasting of future "business as usual" energy needs and their associated CO2 emissions. Our best estimates for 2020 are 800 EJ yr−1 for global energy use and 14 Gt yr−1 for global CO2 emissions, with both being above almost all other published forecasts. This suggests the energy and total CO2 emissions landscape in 2020 may be significantly more challenging than currently envisaged."
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sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #317 on: October 02, 2014, 02:12:29 AM »
sorry, but i have to say this: Anybody who sees 60 year cycles in a 150 yr record is a numerologist.

Jarvis(2014) doi:10.5194/esdd-5-1143-2014 is numerology.

Unfortunately i read the paper.

sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #318 on: October 02, 2014, 03:44:08 AM »
sidd,

I cannot disagree with you, but we will see.

Best,
ASLR
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sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #319 on: October 02, 2014, 06:06:03 AM »
Sorry, i was short tempered in my comment on Jarvis. Apart from the numerology, I was really irked by the lack of attention to the literature. The list of references in the paper is so short as to be laughable. For example, I see no reference to Ruddiman. For a much better treatment, going back much further in time, just look at Ruddiman's work to see how an determined attempt to analyse human influence on climate might be constructed.

I will take the opportunity to point out Ruddiman's 2014 AGU Tyndall lecture



chekitout, is worth it. His latest book is very good too.

sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #320 on: October 02, 2014, 08:41:32 PM »
Thank you for the link. Ruddiman reminds me quite a lot of Alfred Wegeners hypothesis of continental drift. On the way to find facts pro and contra there are lots of worthy results found which stand alone.

Considering numerology and spectral analysis of data sets, my take is: our impact on climate change is much too big, this pattern will probably only be temporary. (I haven't read Jarvis(2014), sorry.)

The paleo-evidence, that the southern hemisphere responded to changes in the north, and then the other way round, will probably not hold this time. Our influence on climate is far to big, the delay observed in the ice cores could collapse. If I understand ASLR correctly, his WAIS collapse scenario is all about this.


AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #321 on: October 02, 2014, 10:38:45 PM »
sidd,

Thanks for the link to the Ruddiman video.  While I have heard of his theory before, this video added many details and numbers that I had never known before.  The detail that sticks-out most prominently for me is illustrated by the first attached image (from his video) that shows a 0.17oC drop in mean global surface temperature (as measured by ice core data) between 1550 and 1620 that apparently was primarily due to the death of almost 50 million Native Americans from Old World diseases.  Ruddiman also showed the second attached image (from his video) showing the climate sensitivity required to achieve this drop in global mean temperature for the associated drop in GHG (as measured by ice core); which is significantly greater that assumed in current GCM projections even when considering that changes in temperature due to changes in GHG is related to the log of the ratio of the new GHG concentration to the reference concentration (which might account for a most a factor of 2).  This seems to provide some support to the idea that the true magnitude of our current value of climate sensitivity is much higher than assumed in our current model projections, but that the true temperature rise is currently being masked by such factors as: the cyclic phasing of heat going into the ocean, negative forcing from air pollution, and a temporary burst of plant growth in the tundra and deserts due to recent increases in CO2.

Best,
ASLR
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sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #322 on: October 03, 2014, 05:33:35 AM »
"
(I haven't read Jarvis(2014), sorry.)

You have missed little. I wish i hadn't.

Re: Ruddiman
It is a pity that most are unaware of his works. I do not necessarily agree with all his conclusions. But the corpus he has doggedly put together over the last decade or so affirming his thesis of early anthro influence is undeniably strong. His last book, "Earth Transformed " ISBN-13: 978-1464107764 has closer detail, but a very great deal of his research is freely available on the web. And I am sure he will email anyone interested copies of his papers upon request.

Another set of overlooked works are those by Kidder and Worsley, of which I have spoken elsewhere.

sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #323 on: October 03, 2014, 04:26:16 PM »
The linked reference (with Bill Ruddiman as a co-author) cites that net effect of surface albedo changes from anthropogenic land cover  change (ALCC) amounts to a global warming of 0.73oC during the preindustrial era:

F. He, S.J. Vavrus, J. E. Kutzbach, W. F. Ruddiman, J. O. Kaplan, and K. M. Krumbach, (2014), "Simulating global and local surface temperature changes due to Holocene anthropgenic land cover change", Geophysical Res. Lett., 41: 1-7 doi:10.1002/2013GL058085.

https://courses.seas.harvard.edu/climate/eli/Courses/global-change-debates/Sources/06-Early-anthropogenic-warming/He-etal-2014.pdf

http://onlinelibrary.wiley.com/doi/10.1002/2013GL058085/abstract

Abstract: "Surface albedo changes from anthropogenic land cover change (ALCC) represent the second largest negative radiative forcing behind aerosol during the industrial era. Using a new reconstruction of ALCC during the Holocene era by Kaplan et al. (2011), we quantify the local and global temperature response induced by Holocene ALCC in the Community Climate System Model, version 4. We find that Holocene ALCC causes a global cooling of 0.17°C due to the biogeophysical effects of land-atmosphere exchange of momentum, moisture, and radiative and heat fluxes. On the global scale, the biogeochemical effects of Holocene ALCC from carbon emissions dominate the biogeophysical effects by causing 0.9°C global warming. The net effects of Holocene ALCC amount to a global warming of 0.73°C during the preindustrial era, which is comparable to the ~0.8°C warming during industrial times. On local to regional scales, such as parts of Europe, North America, and Asia, the biogeophysical effects of Holocene ALCC are significant and comparable to the biogeochemical effect."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #324 on: October 03, 2014, 10:28:40 PM »
The linked reference finds that degrading permafrost will produce more methane and less carbon dioxide that current Earth System Models assume; which when corrected will significantly increase projections of Arctic amplification:

Zhaosheng Fan, Jason C. Neff, Mark P. Waldrop, Ashley P. Ballantyne, Merritt R. Turetsky, (2014), "Transport of oxygen in soil pore-water systems: implications for modeling emissions of carbon dioxide and methane from peatlands", Biogeochemistry, doi:10.1007/s1053-014-0012-0.

http://link.springer.com/article/10.1007%2Fs10533-014-0012-0#page-1

Abstract: "Peatlands store vast amounts of soil carbon and are significant sources of greenhouse gases, including carbon dioxide (CO2) and methane (CH4) emissions. The traditional approach in biogeochemical model simulations of peatland emissions is to simply divide the soil domain into an aerobic zone above and an anaerobic zone below the water table (WT) and then calculate CO2 and CH4 emissions based on the assumed properties of these two discrete zones. However, there are major potential drawbacks associated with the traditional WT-based approach, because aerobic or anaerobic environments are ultimately determined by oxygen (O2) concentration rather than water content directly. Variations in O2 content above and below the WT can be large and thus may play an important role in partitioning of carbon fluxes between CO2 and CH4. In this paper, we propose an oxygen-based approach, which simulates the vertical and radial components of O2 movement and consumption through the soil aerobic and anaerobic environments. We then use both our oxygen-based and the traditional WT-based approaches to simulate CO2 and CH4 emissions from an Alaskan fen peatland. The results of model calibration and validation suggest that our physically realistic approach (i.e., oxygen-based approach) cause less biases on the simulated flux of CO2 and CH4. The results of model simulations also suggest that the traditional WT-based approach might substantially under-estimate CH4 emissions and over-estimate CO2 emissions from the fen due to the presence of anaerobic zones in unsaturated soil. Our oxygen-based approach can be easily incorporated into existing ecosystem or earth system models but will require additional validation with more extensive field observations to be implemented within biogeochemical models to improve simulations of soil C fluxes at regional or global scale."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #325 on: October 06, 2014, 02:47:13 AM »
The linked reference (with an open access pdf) proves that the Southern Ocean has been absorbing more heat than previously assumed by the CMIP5 projections; which, proves that ECS is meaningfully higher than 3.0 degrees.  This proves that the IPCC AR5 mean global temperature rise projections have erred on the low side:

Paul J. Durack, Peter J. Gleckler, Felix W. Landerer and Karl E. Taylor, (2014), "Quantifying Underestimates of Long-term Upper-Ocean Warming", Nature Climate Change, 4 (11), DOI: 10.1038/nclimate2389

http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/140926a_Duracketal_UpperOceanWarming.pdf

Abstract: "The global ocean stores more than 90% of the heat associated with observed greenhouse‐gas‐attributed global warming (Levitus et al., 2005; Church et al., 2011; Otto et al., 2013; Rhein et al., 2013). Using satellite altimetry observations and a large suite of climate models, we conclude that observed estimates of 0‐700 dbar global ocean warming since 1970 are likely biased low. This underestimation is attributed to poor sampling of the Southern Hemisphere, and limitations of the analysis methods that conservatively estimate temperature changes in data‐sparse regions (Gregory et al., 2004; Gouretski & Koltermann, 2007; Gille, 2008). We find that the partitioning of northern and southern hemispheric simulated sea surface height changes are consistent with precise altimeter observations, whereas the hemispheric partitioning of simulated upper‐ocean warming is inconsistent with observed in‐situ‐based ocean heat content estimates. Relying on the close correspondence between hemispheric‐scale ocean heat content and steric changes, we adjust the poorly constrained Southern Hemisphere observed warming estimates so that hemispheric ratios are consistent with the broad range of modelled results. These adjustments yield large increases (2.2‐7.1 x 1022 J 35yrs‐1) to current global upper‐ocean heat content change estimates, and have important implications for sea level, the planetary energy budget and climate sensitivity assessments."

See also:
http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/

« Last Edit: October 06, 2014, 02:54:15 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 #326 on: October 09, 2014, 12:26:37 AM »

The linked reference indicates that dimethylamine can significantly facilitate cloud formation, unfortunately ocean acidification is threatening to significantly reduce the amount of natural dimethylamine emitted into the atmosphere so unless society is interested in using dimethylamine in geoengineering, we are likely headed towards accelerating global warming as the ocean continues to acidify:

Kürten, A., Jokinen, T., Simon, M., Sipilä, M., Sarnela, N., Junninen, H., Adamov, A., Almeida, J., Amorim, A., Bianchi, F., Breitenlechner, M., Dommen, J., Donahue, N. M., Duplissy, J., Ehrhart, S., Flagan, R. C., Franchin, A., Hakala, J., Hansel, A., Heinritzi, M., Hutterli, M., Kangasluoma, J., Kirkby, J., Laaksonen, A., Lehtipalo, K., Leiminger, M., Makhmutov, V., Mathot, S., Onnela, A., Petäjä, T., Praplan, A. P., Riccobono, F., Rissanen, M. P., Rondo, L., Schobesberger, S., Seinfeld, J. H., Steiner, G., Tomé, A., Tröstl, J., Winkler, P. M., Williamson, C., Wimmer, D., Ye, P., Baltensperger, U., Carslaw, K. S., Kulmala, M., Worsnop, D. R., and Curtius, J., (2014), "Neutral molecular cluster formation of sulphuric acid-dimethylamine observed in real-time under atmospheric conditions", Proc. Natl. Acad. Sci., doi/10.1073/pnas.1404853111.


http://www.pnas.org/content/early/2014/10/02/1404853111

Abstract: "For atmospheric sulfuric acid (SA) concentrations the presence of dimethylamine (DMA) at mixing ratios of several parts per trillion by volume can explain observed boundary layer new particle formation rates. However, the concentration and molecular composition of the neutral (uncharged) clusters have not been reported so far due to the lack of suitable instrumentation. Here we report on experiments from the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research revealing the formation of neutral particles containing up to 14 SA and 16 DMA molecules, corresponding to a mobility diameter of about 2 nm, under atmospherically relevant conditions. These measurements bridge the gap between the molecular and particle perspectives of nucleation, revealing the fundamental processes involved in particle formation and growth. The neutral clusters are found to form at or close to the kinetic limit where particle formation is limited only by the collision rate of SA molecules. Even though the neutral particles are stable against evaporation from the SA dimer onward, the formation rates of particles at 1.7-nm size, which contain about 10 SA molecules, are up to 4 orders of magnitude smaller compared with those of the dimer due to coagulation and wall loss of particles before they reach 1.7 nm in diameter. This demonstrates that neither the atmospheric particle formation rate nor its dependence on SA can simply be interpreted in terms of cluster evaporation or the molecular composition of a critical nucleus."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #327 on: October 14, 2014, 01:32:32 AM »
The linked reference states that as atmospheric CO₂ levels increase C3 plants can absorb more CO₂, and as a result of this Earth System models overestimate the growth rate for CO2 in the future by as much as 16%.  However, these findings are not relevent if these C3 plants die in the future due to excessive climate change:

Ying Sun, Lianhong Gu, Robert E. Dickinson, Richard J. Norby, Stephen G. Pallardy and Forrest M. Hoffman, (2014), "Impact of mesophyll diffusion on estimated global land CO2 fertilization", PNAS, doi: 10.1073/pnas.1418075111

http://www.pnas.org/content/early/2014/10/10/1418075111

Abstract: "In C3 plants, CO2 concentrations drop considerably along mesophyll diffusion pathways from substomatal cavities to chloroplasts where CO2 assimilation occurs. Global carbon cycle models have not explicitly represented this internal drawdown and therefore overestimate CO2 available for carboxylation and underestimate photosynthetic responsiveness to atmospheric CO2. An explicit consideration of mesophyll diffusion increases the modeled cumulative CO2 fertilization effect (CFE) for global gross primary production (GPP) from 915 to 1,057 PgC for the period of 1901–2010. This increase represents a 16% correction, which is large enough to explain the persistent overestimation of growth rates of historical atmospheric CO2 by Earth system models. Without this correction, the CFE for global GPP is underestimated by 0.05 PgC/y/ppm. This finding implies that the contemporary terrestrial biosphere is more CO2 limited than previously thought."

See also:
http://www.reportingclimatescience.com/news-stories/article/climate-models-underestimate-plant-co2-uptake-says-study.html
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jai mitchell

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #328 on: October 14, 2014, 05:38:48 AM »
Jai Mitchell posted that there is an error in the signs of the terms in the following reference; however, as I do not know whether that is true, or not, I have decided to post the linked reference as it discusses potentially important absorbed solar radiation (ASR) – Arctic sea ice concentration (SIC) relationship. This ASR-SIC relationship is currently not represented in most of the current climate models, and thus the majority of GCM projections may possibly underestimate the important positive feedback mechanism of Arctic amplification, and if true this would mean that they underestimate projections of future increases in mean global warming:

Yong-Sang Choi, Baek-Min Kim, Sun-Kyong Hur, Seong-Joong Kim, Joo-Hong Kim and Chang-Hoi Ho, (2014), "Connecting early summer cloud-controlled sunlight and late summer sea ice in the Arctic", Journal of Geophysical Research Atmospheres DOI: 10.1002/2014JD022013

http://onlinelibrary.wiley.com/doi/10.1002/2014JD022013/abstract

Abstract: "This study demonstrates that absorbed solar radiation (ASR) at the top of the atmosphere in early summer (May–July) plays a precursory role in determining the Arctic sea ice concentration (SIC) in late summer (August–October). The monthly ASR anomalies are obtained over the Arctic Ocean (65°N–90°N) from the Clouds and the Earth's Radiant Energy System during 2000–2013. The ASR changes primarily with cloud variation. We found that the ASR anomaly in early summer is significantly correlated with the SIC anomaly in late summer (correlation coefficient, r  ≈ −0.8 with a lag of 1 to 4 months). The region exhibiting high (low) ASR anomalies and low (high) SIC anomalies varies yearly. The possible reason is that the solar heat input to ice is most effectively affected by the cloud shielding effect under the maximum TOA solar radiation in June and amplified by the ice-albedo feedback. This intimate delayed ASR-SIC relationship is not represented in most of current climate models. Rather, the models tend to over-emphasize internal sea ice processes in summer."

The paper is correct, the reporting of it has been opposite, stating that increased cloud cover led to increased concentration loss in late season.

By the way, good post on the interstadial ECS analysis.  This is the crux of the matter, most I have seen simply throw this part out, severely underestimating the ECS.  Current TOA is closer to .9 not .7 W/m^2 as evidenced by Durack and the indication is that the models work for the northern hemisphere but severely underestimate forcing for the southern hemisphere.  This indicates a severe underestimation of negative forcing from Northern Hemisphere aerosols. 

once these two factors are addressed and the residual fast feedbacks are included in the analysis, the .9 C(w/m^2) is going to also seem a bit low.
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #329 on: October 14, 2014, 05:05:39 PM »
jai,

Thanks for the clarification on the Choi et al (2014) paper, and for spreading the message that most models are currently assuming ECS values that are too low.

In this regards, and as a follow-up to my Reply #336, while it is true that currently plants are absorbing more CO₂ than most Earth System models were assuming; nevertheless, as the following linked reference makes clear if the plants are deforested (say due to world population increasing to 10 billion by 2050), or die from other causes (drought, flood, seasons shifting, insect infestation, heat stress, etc.) then the temporary current increase in CO₂ absorption by plants, will not buy us much in the long term:

Sandro Pütz, Jürgen Groeneveld, Klaus Henle, Christoph Knogge, Alexandre Camargo Martensen, Markus Metz, Jean Paul Metzger, Milton Cezar Ribeiro, Dantas de Paula, M. & Andreas Huth, (2014), "Long-term carbon loss in fragmented Neotropical forests." Nature Communications 5:5037 DOI:10.1038/ncomms6037

http://www.nature.com/ncomms/2014/141007/ncomms6037/full/ncomms6037.html
Abstract: "Tropical forests play an important role in the global carbon cycle, as they store a large amount of carbon (C). Tropical forest deforestation has been identified as a major source of CO2 emissions, though biomass loss due to fragmentation—the creation of additional forest edges—has been largely overlooked as an additional CO2 source. Here, through the combination of remote sensing and knowledge on ecological processes, we present long-term carbon loss estimates due to fragmentation of Neotropical forests: within 10 years the Brazilian Atlantic Forest has lost 69 (±14) Tg C, and the Amazon 599 (±120) Tg C due to fragmentation alone. For all tropical forests, we estimate emissions up to 0.2 Pg C y−1 or 9 to 24% of the annual global C loss due to deforestation. In conclusion, tropical forest fragmentation increases carbon loss and should be accounted for when attempting to understand the role of vegetation in the global carbon balance."

Also see:
http://phys.org/news/2014-10-brazil-rainforests-carbon-dioxide-previously.html#jCp
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #330 on: October 18, 2014, 12:17:58 AM »
In my Replies #219 and 221, I note that current measurements indicate that the magnetic poles are flipping at a rate that could reverse the poles by 180 degrees with about 200 years; however, the following linked reference provides paleo-evidence that this 180 degree flip could happen in as little at 100 years.  In my Reply #221 is speculate how the changes in magma circulation associated with such a rapid magnetic flip could increase tectonic activity (both seismic and volcanic); and  I also wonder whether the migration of the rotational axis of the Earth in the opposite direction (as the migration of the magnetic pole), due to the melting of the recent ice melting (see the following Chen et al 2013 reference at the end of this post) is helping to accelerate the migration of the magnetic pole, and will also contribute to a still greater acceleration of tectonic activity:


Leonardo Sagnotti, Giancarlo Scardia, Biagio Giaccio, Joseph C. Liddicoat, Sebastien Nomade, Paul R. Renne and Courtney J. Sprain, (2014), "Extremely rapid directional change during Matuyama-Brunhes geomagnetic polarity reversal", Geophys. J. Int., 199 (2): 1110-1124. doi: 10.1093/gji/ggu287

http://gji.oxfordjournals.org/content/199/2/1110.abstract

Abstract: " We report a palaeomagnetic investigation of the last full geomagnetic field reversal, the Matuyama-Brunhes (M-B) transition, as preserved in a continuous sequence of exposed lacustrine sediments in the Apennines of Central Italy. The palaeomagnetic record provides the most direct evidence for the tempo of transitional field behaviour yet obtained for the M-B transition. 40Ar/39Ar dating of tephra layers bracketing the M-B transition provides high-accuracy age constraints and indicates a mean sediment accumulation rate of about 0.2 mm yr–1 during the transition. Two relative palaeointensity (RPI) minima are present in the M-B transition. During the terminus of the upper RPI minimum, a directional change of about 180 ° occurred at an extremely fast rate, estimated to be less than 2 ° per year, with no intermediate virtual geomagnetic poles (VGPs) documented during the transit from the southern to northern hemisphere. Thus, the entry into the Brunhes Normal Chron as represented by the palaeomagnetic directions and VGPs developed in a time interval comparable to the duration of an average human life, which is an order of magnitude more rapid than suggested by current models. The reported investigation therefore provides high-resolution integrated palaeomagnetic and radioisotopic data that document the fine details of the anatomy and tempo of the M-B transition in Central Italy that in turn are crucial for a better understanding of Earth's magnetic field, and for the development of more sophisticated models that are able to describe its global structure and behaviour."

See also:
http://www.livescience.com/48333-magnetic-field-flip-within-100-years.html

http://www.redorbit.com/news/science/1113257987/earth-magnetic-field-flip-101614/


Chen, J.L., C.R. Wilson, J.C. Ries, B.D. Tapley, Rapid ice melting drives Earth's pole to the east, Geophys. Res. Lett., Vol. 40, 1-6, DOI: 10.1002/grl.50552, 2013. [Online Version] [PDF Preprint] [Nature News Coverage]
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #331 on: October 25, 2014, 12:54:41 AM »
Biogenic volatile organic compounds, associated with the conversion of forests to agriculture (in addition to changes in CO₂ and surface albedo), have been masking global warming (as I have mentioned in previous posts).  According to the following linked reference the amount of this masking from 1850 to 2000 was a net global radiative impact of −0.11 ± 0.17 W m−2 (cooling) (see the two attached images, with captions given after the abstract).  As global warming stresses plant growth, this masking factor will stop and global warming will accelerate.

Nadine Unger, (2014), "Human land-use-driven reduction of forest volatiles cools global climate", Nature Climate Change, Volume: 4, Pages: 907–910, doi:10.1038/nclimate2347

http://www.nature.com/nclimate/journal/v4/n10/full/nclimate2347.html

Abstract: "Human conversion of forest ecosystems to agriculture is a major driver of global change. Conventionally, the impacts of the historical cropland expansion on Earth’s radiation balance have been quantified through two opposing effects: the release of stored carbon to the atmosphere as CO2 (warming) versus the increase in surface albedo (cooling). Changing forest cover has a third effect on the global radiation balance by altering emissions of biogenic volatile organic compounds (BVOCs) that control the loadings of multiple warming and cooling climate pollutants: tropospheric ozone (O3), methane (CH4) and aerosols. Although human land cover change has dominated BVOC emission variability over the past century, the net effect on global climate has not been quantified. Here, I show that the effects of the global cropland expansion between the 1850s and 2000s on BVOC emissions and atmospheric chemistry have imposed an additional net global radiative impact of −0.11 ± 0.17 W m−2 (cooling). This magnitude is comparable to that of the surface albedo and land carbon release effects. I conclude that atmospheric chemistry must be considered in climate impact assessments of anthropogenic land cover change and in forestry for climate protection strategies."

Caption for first image: "Climate pollutants are calculated in this study. Barred black lines indicate uncertainty range. Uncertainties for climate pollutants are assigned a best estimate of ±100% based on a factor of two uncertainty in BVOC emissions."

Caption for second image: "The left column is the LAND case and the right column is the LAND-fixbvoc case. Individual results for the dominant inhomogeneous climate pollutants are shown for each case."
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sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #332 on: October 25, 2014, 04:44:24 AM »
The effect, as i remarked on realclimate, is zero to within error. I did some archeology on her (Unger's) previous papers, was not impressed. When she comes back with tighter error bars, i might pay attention.

sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #333 on: October 25, 2014, 03:02:51 PM »
Unger and trees. What should we plant?

From the abstract of G.Bala et.al. Combined climate and carbon-cycle effects of large-scale deforestation (2006):

Quote
afforestation projects in the tropics would be clearly beneficial in mitigating global-scale warming, but would be counterproductive if implemented at high latitudes and would offer only marginal benefits in temperate regions.
http://www.pnas.org/content/104/16/6550.abstract

I had some correspondence with author Bala in 2007.  The starting question was:

Quote
Does the LLNL work on "Trees to offset the carbon footprint?"discuss the following situation:

Coppiced willow grown by farmers in East Yorkshire, which has very little snow, is used for heating. The willow is regularly cropped and dried in the field before being used as fuel.

Is the displacement of fossil fuel counterbalanced by an albedo effect? If so,what is a rough estimate of this effect?
Later after a few exchanges

Quote
My questions summarised:

I think your research shows that if we wish to slow global warming:

1. Planting (or keeping) trees in tropical regions is good.

2. Planting trees in snowy areas is bad.

3. Planting trees in other areas may be good or bad.

Is this correct?
Bala replied

Quote
Points 1 and 2 are ok.
Point 3 should be "planting trees in other areas may offer little benefit."
This doesn't answer the questions I should have asked.
Quote
1. What should be planted?
2. How should the planting be managed?
3. What happens to the products?
4. How would this compare with the alternative use of the land?
For example, willow has a relatively high albedo and may not have the volatile organic compounds of pine. I know Unger and Bala are top scientists but are they asking the right questions?
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #334 on: October 25, 2014, 03:05:51 PM »
Should this tree stuff be elsewhere?
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Laurent

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #335 on: October 25, 2014, 04:13:11 PM »
GeoffBeacon, there is the "Garden" thread or the "global forest watch". If your point is solely on the albedo achieved by trees then stay there (but it doesn't look like it  ;)).

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #336 on: October 25, 2014, 07:33:04 PM »
Should this tree stuff be elsewhere?

Geoff,

Thank you for your post(s).  Feel free to post here if you want to discuss the overall topic of climate sensitivity and radiative forcing (which not only affects the potential collapse of the WAIS but also impacts almost every other aspect associated with climate change); however, if you want to address any specific issue in depth, then feel free to post in another thread.

Obviously, the topic of climate sensitivity and radiative forcing is a complex issue with a lot of chaotic interactions that  change with time and circumstances.  Therefore, I concur with sidd that we should question/challenge the findings of any given paper, or author, with the full understanding that excess uncertainties are not our friend but the enemy.  Your discussion about some of the various factors about what types of vegetation and in what locations, and in what circumstances, illustrates this quite well; and the big picture of the Unger paper (specific numbers aside) is that most planners have previously ignored the importance of BVOC in their efforts to understand the net impacts of vegetation including changes in: surface albedo, CO2 absorption/emission, resistance to drought/flood/fires, etc.  Recent research indicates that boreal forests not only decrease albedo in snowy areas (thus increasing warming) but also emit significant quantities of BVOCs (thus contributing to cooling).  Therefore, if increasing: insect infestations, droughts, permafrost degradation, forest fires, etc., leads to a decreasing in the boreal forests, the Earth may experience an acceleration of warming that is currently not accounted for in the vast majority of Global/General Circulation Model projections.

Best,
ASLR   
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GeoffBeacon

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #337 on: October 26, 2014, 11:43:42 AM »
ALSR

Thanks. That helps but is there a mistake here?
Quote
Recent research indicates that boreal forests not only decrease albedo in snowy areas (thus increasing warming) but also emit significant quantities of BVOCs (thus contributing to cooling).
I thought Unger was arguing that BVOCs contribute to warming:
Quote
Using sophisticated climate modeling, Unger calculated that a 30-percent decline in BVOC emissions between 1850 and 2000, largely through the conversion of forests to cropland, produced a net global cooling of about 0.1 degrees Celsius.
http://environment.yale.edu/news/article/yale-study-looks-at-how-global-conversion-of-forests-to-cropland-affected-climate/

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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #338 on: October 26, 2014, 03:32:20 PM »
Geoff,

Thanks for bringing up this apparent inconsistency in logic (either on my part or in my opinion on Unger's part, as I agree with sidd that Unger's error bars are too large to make any clear conclusion).  I this regard, in Reply #152 I made the following post, which presents very clear research indicating that VOC emissions from the boreal forest are a negative feedback factor.  Therefore, unless I am wrong, it is plausible that the cooling that Unger reports from the "sophisticated climate modeling" is not due to the reduction in BVOC's from cutting down the boreal forest, but due to other factors such as: change in albedo, change in snowfall patterns, or other factors that Unger may not have isolated adequately due to the large error bars on the input & output data.  I apologize for any confusion that I may be contributing to this matter:


The following is the quote from my Reply # 152:

"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
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GeoffBeacon

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #339 on: October 27, 2014, 03:23:36 AM »
ALSR

Wow. Thanks

Geoff
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #340 on: November 11, 2014, 09:51:09 PM »
Don't know if this is the right place for this, but it seems like an interesting new (to me) twist on the dynamics of melt:

http://www.latimes.com/science/sciencenow/la-sci-sn-underwater-rovers-robots-antarctica-eddies-ice-sheet-melting-climate-change-20141110-story.html

Underwater ‘storms’ may hold key to melting Antarctic ice

Quote
Scientists using robotic ocean gliders to wander frigid Antarctic waters say they may have discovered a mechanism behind the melting of polar ice shelves – miniature submarine “storms” that are lobbing packets of warmer water toward the continent..

The findings, published in the journal Nature Geoscience, shed light on the complicated currents that could potentially be contributing to the loss of West Antarctic ice.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #341 on: November 12, 2014, 04:42:48 PM »
Perhaps this is the article they referenced.

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2289.html

Eddy transport as a key component of the Antarctic overturning circulation.

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #342 on: November 12, 2014, 07:49:47 PM »
The linked reference indicates that positive feedback from absorbed solar radiation (ASR) due to changes in polar albedo can impact global temperatures relatively rapidly (within decades) from the original radiative forcing (anthropogenic GHG emissions).  This emphasizes that the influence of the change in polar albedo that Hansen & Sato (2012) show in the attached plot can happen within a few decades from now:

Aaron Donohoe, Kyle C. Armour, Angeline G. Pendergrass, and David S. Battisti, (2014), "Shortwave and longwave radiative contributions to global warming under increasing CO2", PNAS, doi: 10.1073/pnas.1412190111

http://www.pnas.org/content/early/2014/11/05/1412190111.abstract

Abstract:  "In response to increasing concentrations of atmospheric CO2, high-end general circulation models (GCMs) simulate an accumulation of energy at the top of the atmosphere not through a reduction in outgoing longwave radiation (OLR)—as one might expect from greenhouse gas forcing—but through an enhancement of net absorbed solar radiation (ASR). A simple linear radiative feedback framework is used to explain this counterintuitive behavior. It is found that the timescale over which OLR returns to its initial value after a CO2 perturbation depends sensitively on the magnitude of shortwave (SW) feedbacks. If SW feedbacks are sufficiently positive, OLR recovers within merely several decades, and any subsequent global energy accumulation is because of enhanced ASR only. In the GCM mean, this OLR recovery timescale is only 20 y because of robust SW water vapor and surface albedo feedbacks. However, a large spread in the net SW feedback across models (because of clouds) produces a range of OLR responses; in those few models with a weak SW feedback, OLR takes centuries to recover, and energy accumulation is dominated by reduced OLR. Observational constraints of radiative feedbacks—from satellite radiation and surface temperature data—suggest an OLR recovery timescale of decades or less, consistent with the majority of GCMs. Altogether, these results suggest that, although greenhouse gas forcing predominantly acts to reduce OLR, the resulting global warming is likely caused by enhanced ASR."
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sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #343 on: November 13, 2014, 02:46:51 AM »
heeheehee
that paper by Thompson left out one important player off camera, i added him.

The Kraken stirs.
Cold fires deep melt icy keeps.
Towers totter. Ramparts crumble.
Souring seas surge.
The Kraken stirs.

bligh8

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #344 on: November 13, 2014, 04:17:22 AM »
Now, was that Thompson or Purkey

Winnow with giant arms the slumbering green.
There hath he lain for ages and will lie
Battening upon huge sea-worms in his sleep,
Until the latter fire shall heat the deep;
Then once by man and angels to be seen,
In roaring he shall rise and on the surface die.

Or Tennyson
Fair Winds Sidd
w

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #345 on: November 13, 2014, 04:44:27 AM »
heeheehee
that paper by Thompson left out one important player off camera, i added him.

The Kraken stirs.
Cold fires deep melt icy keeps.
Towers totter. Ramparts crumble.
Souring seas surge.
The Kraken stirs.

sidd,

Neven is very worried about the methane hydrate Kraken in the Arctic Ocean, so please do not give him nightmares about the Weddell Sea clathrate gun Kraken.

Best
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sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #346 on: November 13, 2014, 08:42:53 AM »
Thompson fig 1 c

But the latest Purkey is very nice also.

I should be honest and say the image i added is not the Kraken, per se, but a close relative, the Leviathan, as in the image by Gustav Dore (that last e should have an acute symbol over it ...)

https://en.wikipedia.org/wiki/File:Destruction_of_Leviathan.png

sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #347 on: November 13, 2014, 07:23:45 PM »
With a hat-tip to jai Mitchell from the "Consequence" folder, I provide the following two references that indicate that climate sensitivity is likely higher than what is currently assumed in most IPCC cited GCM projections

Ken Caldeira and Ivana Cvijanovic, (2014), "Estimating the Contribution of Sea Ice Response to Climate Sensitivity in a Climate Model", J. Climate, 27, 8597–8607, doi: http://dx.doi.org/10.1175/JCLI-D-14-00042.1

http://journals.ametsoc.org/doi/full/10.1175/JCLI-D-14-00042.1

Abstract: "The response of sea ice to climate change affects Earth’s radiative properties in ways that contribute to yet more climate change. Here, a configuration of the Community Earth System Model, version 1.0.4 (CESM 1.0.4), with a slab ocean model and a thermodynamic–dynamic sea ice model is used to investigate the overall contribution to climate sensitivity of feedbacks associated with the sea ice loss. In simulations in which sea ice is not present and ocean temperatures are allowed to fall below freezing, the climate feedback parameter averages ~1.31 W m−2 K−1; the value obtained for control simulations with active sea ice is ~1.05 W m−2 K−1, indicating that, in this configuration of CESM1.0.4, sea ice response accounts for ~20% of climate sensitivity to an imposed change in radiative forcing. In this model, the effect of sea ice response on the longwave climate feedback parameter is nearly half as important as its effect on the shortwave climate feedback parameter. Further, it is shown that the strength of the overall sea ice feedback can be related to 1) the sensitivity of sea ice area to changes in temperature and 2) the sensitivity of sea ice radiative forcing to changes in sea ice area. An alternative method of disabling sea ice response leads to similar conclusions. It is estimated that the presence of sea ice in the preindustrial control simulation has a climate effect equivalent to ~3 W m−2 of radiative forcing."


Daniel R. Feldman, William D. Collins, Robert Pincus, Xianglei Huang, and Xiuhong Chen, (2014), " Far-infrared surface emissivity and climate", PNAS, doi: 10.1073/pnas.1413640111

http://www.pnas.org/content/early/2014/10/29/1413640111.abstract

Abstract: "Presently, there are no global measurement constraints on the surface emissivity at wavelengths longer than 15 μm, even though this surface property in this far-IR region has a direct impact on the outgoing longwave radiation (OLR) and infrared cooling rates where the column precipitable water vapor (PWV) is less than 1 mm. Such dry conditions are common for high-altitude and high-latitude locations, with the potential for modeled climate to be impacted by uncertain surface characteristics. This paper explores the sensitivity of instantaneous OLR and cooling rates to changes in far-IR surface emissivity and how this unconstrained property impacts climate model projections. At high latitudes and altitudes, a 0.05 change in emissivity due to mineralogy and snow grain size can cause a 1.8–2.0 W m−2 difference in the instantaneous clear-sky OLR. A variety of radiative transfer techniques have been used to model the far-IR spectral emissivities of surface types defined by the International Geosphere-Biosphere Program. Incorporating these far-IR surface emissivities into the Representative Concentration Pathway (RCP) 8.5 scenario of the Community Earth System Model leads to discernible changes in the spatial patterns of surface temperature, OLR, and frozen surface extent. The model results differ at high latitudes by as much as 2°K, 10 W m−2, and 15%, respectively, after only 25 y of integration. Additionally, the calculated difference in far-IR emissivity between ocean and sea ice of between 0.1 and 0.2, suggests the potential for a far-IR positive feedback for polar climate change."
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sidd

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #348 on: November 13, 2014, 10:22:16 PM »
2 quick comments:

1) I think a shortcoming of the Caldeira paper is the slab ocean, they need to put in a better ocean. Apart from the other advantages, a realistic ocean will allow them to get a timescale for the transition to ice free states. I dont like the bit where they let the ocean supercool, a better ocean would have let them finesse the difficulty.

2)The surface IR emissivity effect in the second reference must be looked at not primarily in terms of TOA radiative imbalance but rather in terms of modulating ocean heat flux to atmosphere. The effect operates in parallel with latent heat flux across open ocean surface, where it exists. Unfortunately, the major differences in this treatment from previous ones appear in regional patterns, which is exactly where both treatments are the weakest. The evidence one way or the other must come from observation, which we gain but slowly, rather than model intercomparison.

wili

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #349 on: November 14, 2014, 07:13:40 PM »
John Abraham has a piece in the Guardian on the Thompson/Heywood paper.

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/nov/13/warm-waters-are-melting-antarctica-from-below

Toward the end, he mentions: " I have a paper in press with Dr. Ted Scambos that identifies the potential for rapid sea level rise based on Antarctic melting. I hope to share our findings with you in the next few weeks."

Something to look forward to (though not without some dread!).
"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."