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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #250 on: August 04, 2014, 05:58:09 PM »
The following link leads to information that since the last glacial maximum the northern and southern hemisphere have exhibited different glacial behaviors.  To my way of thinking, this likely means that most of the radiative forcing over this period was concentrated in the Northern Hemisphere, which means that the climate sensitivities of the GCMs used to model this period need to be corrected upwards so that the measured mean global temperature increases as earth came out of the last ice age were achieved with less radiative forcing than previously assumed (see also Replies #242, 246 & 247, which discuss related information that also support the conclusion that current GCM projections are based on climate sensitivity values are too low to match the paleo-record):


Henrik Rother, David Fink, James Shulmeister, Charles Mifsud, Michael Evans, and Jeremy Pugh, (2014), "The early rise and late demise of New Zealand’s last glacial maximum", PNAS, doi: 10.1073/pnas.1401547111

http://www.pnas.org/content/early/2014/07/23/1401547111.abstract


Abstract: "Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the last glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models. Here we present a suite of 58 cosmogenic exposure ages from 17 last-glacial ice limits in the Rangitata Valley of New Zealand, capturing an extensive record of glacial oscillations between 28–16 ka. The sequence shows that the local last glacial maximum in this region occurred shortly before 28 ka, followed by several successively less extensive ice readvances between 26–19 ka. The onset of Termination 1 and the ensuing glacial retreat is preserved in exceptional detail through numerous recessional moraines, indicating that ice retreat between 19–16 ka was very gradual. Extensive valley glaciers survived in the Rangitata catchment until at least 15.8 ka. These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early last glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #251 on: August 05, 2014, 06:35:17 PM »
While the following linked reference due emphasize the importance of the European forest with regard to climate change (see the link at the bottom for multiple reference on US forest management & climate change); nevertheless, this paper totally misses the importance of aerosols emitted by northern forests in promoting cloud cover, that will be lost if the northern forests are allowed to degrade rapidly:

Rupert Seidl, Mart-Jan Schelhaas, Werner Rammer & Pieter Johannes Verkerk, (2014), "Increasing forest disturbances in Europe and their impact on carbon storage", Nature Climate Change, doi:10.1038/nclimate2318


http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2318.html


Abstract: "Disturbances from wind, bark beetles and wildfires have increased in Europe’s forests throughout the twentieth century. Climatic changes were identified as a key driver behind this increase, yet how the expected continuation of climate change will affect Europe’s forest disturbance regime remains unresolved. Increasing disturbances could strongly impact the forest carbon budget, and are suggested to contribute to the recently observed carbon sink saturation in Europe’s forests. Here we show that forest disturbance damage in Europe has continued to increase in the first decade of the twenty-first century. On the basis of an ensemble of climate change scenarios we find that damage from wind, bark beetles and forest fires is likely to increase further in coming decades, and estimate the rate of increase to be +0.91 × 106 m3 of timber per year until 2030. We show that this intensification can offset the effect of management strategies aiming to increase the forest carbon sink, and calculate the disturbance-related reduction of the carbon storage potential in Europe’s forests to be 503.4 Tg C in 2021–2030. Our results highlight the considerable carbon cycle feedbacks of changing disturbance regimes, and underline that future forest policy and management will require a stronger focus on disturbance risk and resilience."

For US forest management & climate change see:

http://www.sciencedirect.com/science/journal/03781127/327

“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 #252 on: August 06, 2014, 02:29:43 AM »
Sleepy,

Thanks for the link.  Markku Kulmala is indeed very knowledgeable about low-volatility secondary organic aerosols.  See also, my Reply #151 about the following reference about how critical forests are to maintaining cloud cover:

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

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

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #253 on: August 07, 2014, 10:09:13 PM »
Per the following link of the SWERUS-C3 (Oden) expedition to the Arctic Ocean the team has found zones of high methane emissions from the seafloor in the Laptev Sea (see the first attached figure) and more recently carbon dioxide emissions from the over saturated water (due to the warming of the water west of Bennett Island) as indicated in the second attached image.  The first image from the Laptev Sea slope (in 62m of water), shows “elevated methane levels, about 10 times higher than background seawater":

http://swerus-c3.geo.su.se/index.php/swerus-media

Both of these trends will contribute to global warming at a much higher rate than assumed by the current CMIP5 GCM projections.
« Last Edit: August 08, 2014, 01:57:09 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 #254 on: August 08, 2014, 05:37:38 AM »
The attached image shows that without serious international regulation the CO2 equivalent contribution to global warming of HFCs could be as high by 2050 as the CFCs were contributing before the Montreal Protocol:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #255 on: August 08, 2014, 03:58:16 PM »
Sleepy,

Thanks for your comments, and the figure that I posted in Reply #259 comes from a 2011 estimate in a report that is available for free from the following link:

http://www.unep.org/dewa/portals/67/pdf/HFC_report.pdf

I concur that the data is this figure is a little bit dated, and some of my prior posts discuss other newly identified refrigerants that are accumulating in the atmosphere.  I concur that the plans to regulate such super GHGs are being phased in too slowly and that new gases are being formulated (for monopoly/oligopoly control) all the time.  I am concerned that many countries will say that they are regulating such super GHGs, while leaving loopholes for favorite son manufacturers with a patented refrigerant that is conveniently not covered by the regulations.

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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Bruce Steele

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #256 on: August 08, 2014, 05:08:25 PM »
ASLR, I found a link about Bennett Island and an odd cloud formation that forms over it. The
SWERUS-C3 cruise detected oversaturated water in the vicinity of Bennett Island. I was wondering if perhaps volcanism and Co2 seeps may be a contributor ? Biological decomposition may of course be driving the high pCo2 water detected there but maybe it is something else?

http://cimss.ssec.wisc.edu/goes/blog/archives/622

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #257 on: August 08, 2014, 06:19:14 PM »
Bruce,

Thanks for the very interesting link from March 2008, which attributes the recurring clouds to " orographically-induced cloud plumes, enhanced by a vertically propagating mountain wave", possibly associated with a recurring polynya near the island.  One possibility is that a warm ocean current has been interacting with Bennett Island to produce the polynya, and that with increasing global warming the current is getting stronger/warmer to the point that CO2 saturated in the surrounding cold water is now venting due to the upwelling of the warm current water.  This is just one possibility and we will need to watch to see if other factors are resulting in CO2 venting due to other causes.

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

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #258 on: August 09, 2014, 05:35:43 PM »
Last year, Exxon signed a $3.2 billion deal with Rosneft to drill in the Russian Arctic. The Rosneft-Exxon joint venture will be the first to drill commercially in a region that Russia estimates to hold more than 150 billion barrels of oil equivalent.  While some may think that this is business as usual, the fact that the joint venture will begin drilling later this month in the Kara Sea, and expect to complete their first well by October 2014 (see extract below from the following link), seems to me to be an acceleration of potential radiative force well beyond what was envisioned in RCP 8.5 (the BAU scenario):


http://voiceofrussia.com/uk/news/2014_08_09/Putin-says-West-still-keen-on-trade-with-Russia-despite-sanctions-1988/


Extract: "ExxonMobil's Waller said his company was ready to continue work in the Arctic operation and talked of "our long-term partnership. Here we see great prospects, and ready, with your permission [to Vladimir Putin] and work on".

 “The start of exploratory drilling in the Kara Sea is the most important event of the year for the global oil and gas industry. As a result of this work we are planning to discover a new Kara sea oil province. Developing of the Arctic shelf has a huge multiplicative effect on the whole Russian economy,” said Rosneft's Igor Sechin.

 Russia’s northernmost well, the Universitetskaya-1, will be drilled in open water during the ice-free drilling period from August to late October."

Edit: The following link (and associated extracts) indicates that drilling on the Universitetskaya-1 well began today and that this well is the first of 40 offshore Arctic test wells planned by Rosneft by 2018:

http://www.bloomberg.com/news/2014-08-08/exxon-to-start-drilling-arctic-exploration-well-with-rosneft.html

Extract: "Universitetskaya is the first of as many as 40 offshore wells Rosneft plans by 2018 to test the potential of the unexplored the Arctic Ocean. The geological structure targeted by the drilling is roughly the size of the city of Moscow and may contain as many as 9 billion barrels of oil ..."
« Last Edit: August 09, 2014, 06:00:59 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 #259 on: August 12, 2014, 12:57:00 AM »
The following link indicates that the Keystone XL pipeline could contribute to four times more GHG emissions than the State Department calculated.  However, the API says that this fact is irrelevant because the tar sand oil will produce that amount of emissions whether the Keystone XL pipeline is built, or not, as if the pipeline is not built, the resource will be developed and shipped by railroad (which might be worst for the environment than a pipeline):


http://www.startribune.com/politics/national/270670721.html

Extract: "The much-debated Keystone XL pipeline could produce four times more global warming pollution than the State Department calculated earlier this year, a new study concludes.
The U.S. estimates didn't take into account that the added oil from the pipeline would drop prices by about $3 a barrel, spurring consumption that would create more pollution, the researchers said.
Outside experts not connected to the study gave it mixed reviews. The American Petroleum Institute found the study to be irrelevant because regardless of the pipeline, the tar sands will be developed and oil will be shipped by railroad if not by pipeline, spokeswoman Sabrina Fang said.
The researchers estimate that the proposed pipeline, which would carry oil from tar sands in western Canada to refineries on the Texas Gulf Coast, would increase world greenhouse gas emissions by as much as 121 million tons of carbon dioxide a year."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #260 on: August 12, 2014, 05:51:04 PM »

The linked article focuses on the status of the OCO-2 satellite as of August 12 2014.   The first attached image (an artist's rendering) indicates that the OCO-2 satellite took its first un-calibrated data on August 6 2014, over New Guinea , and the background of that image show a model simulation of predicted CO₂ emission in Asia, showing how much CO₂ both India and China are putting into the air.  The second attached image (again an artist's rendering) illustrates how the OCO-2 satellite leads the "A-Train" of satellites around the world, which will allow for multiple measurements of the same areas from multiple platforms/instruments.  As global warming accelerates, the data from this A-Train will provide clearer documentation of just how large our challenge is:

http://phys.org/news/2014-08-nasa-carbon-counter-orbit.html
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #261 on: August 13, 2014, 01:24:34 AM »
The linked reference discusses key attributes of “brown carbon” from wildfires, airborne atmospheric particles that may have influenced current climate, while models have failed to take the material’s warming effects into account.

Rawad Saleh, Ellis S. Robinson, Daniel S. Tkacik, Adam T. Ahern, Shang Liu, Allison C. Aiken, Ryan C. Sullivan, Albert A. Presto, Manvendra K. Dubey, Robert J. Yokelson, Neil M. Donahue & Allen L. Robinson, (2014), "Brownness of organics in aerosols from biomass burning linked to their black carbon content", Nature Geoscience, doi:10.1038/ngeo2220


http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2220.html


Abstract: "Atmospheric particulate matter plays an important role in the Earth’s radiative balance. Over the past two decades, it has been established that a portion of particulate matter, black carbon, absorbs significant amounts of light and exerts a warming effect rivalling that of anthropogenic carbon dioxide. Most climate models treat black carbon as the sole light-absorbing carbonaceous particulate. However, some organic aerosols, dubbed brown carbon and mainly associated with biomass burning emissions, also absorbs light. Unlike black carbon, whose light absorption properties are well understood, brown carbon comprises a wide range of poorly characterized compounds that exhibit highly variable absorptivities, with reported values spanning two orders of magnitude. Here we present smog chamber experiments to characterize the effective absorptivity of organic aerosol from biomass burning under a range of conditions. We show that brown carbon in emissions from biomass burning is associated mostly with organic compounds of extremely low volatility. In addition, we find that the effective absorptivity of organic aerosol in biomass burning emissions can be parameterized as a function of the ratio of black carbon to organic aerosol, indicating that aerosol absorptivity depends largely on burn conditions, not fuel type. We conclude that brown carbon from biomass burning can be an important factor in aerosol radiative forcing."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #262 on: August 13, 2014, 01:36:10 AM »
The linked reference found that aerosol-cloud associated changes in the amount of the clouds and changes of their internal properties are both equally important in their contribution to cooling our planet. Moreover, they found that the total impact from the influence of aerosols on this type of cloud is almost double that estimated in the latest report of the United Nations Intergovernmental Panel on Climate Change.  These finding could lead to an increase in the observed global warming as China begins to clean-up its air pollution:

Yi-Chun Chen, Matthew W. Christensen, Graeme L. Stephens & John H. Seinfeld, (2014), "Satellite-based estimate of global aerosol–cloud radiative forcing by marine warm clouds", Nature Geoscience, doi:10.1038/ngeo2214

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2214.html

Abstract: "Changes in aerosol concentrations affect cloud albedo and Earth’s radiative balance. Aerosol radiative forcing from pre-industrial time to the present due to the effect of atmospheric aerosol levels on the micro- and macrophysics of clouds bears the largest uncertainty among external influences on climate change. Of all cloud forms, low-level marine clouds exert the largest impact on the planet’s albedo. For example, a 6% increase in the albedo of global marine stratiform clouds could offset the warming that would result from a doubling of atmospheric CO2 concentrations. Marine warm cloud properties are thought to depend on aerosol levels and large-scale dynamic or thermodynamic states. Here we present a comprehensive analysis of multiple measurements from the A-Train constellation of Earth-observing satellites, to quantify the radiative forcing exerted by aerosols interacting with marine clouds. Specifically, we analyse observations of co-located aerosols and clouds over the world’s oceans for the period August 2006–April 2011, comprising over 7.3 million CloudSat single-layer marine warm cloud pixels. We find that thermodynamic conditions—that is, tropospheric stability and humidity in the free troposphere—and the state of precipitation act together to govern the cloud liquid water responses to the presence of aerosols and the strength of aerosol–cloud radiative forcing."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #263 on: August 13, 2014, 02:46:47 AM »
The linked reference (with a free access pdf) provides evidence that the main source of uncertainty for Arctic climate variability, and its predictability, is the North Pacific.  As we know that the North Pacific is projected to warm-up over the next 25 years in order to synchronize with the North Atlantic, it seems likely that we can expect the Arctic to warm rapidly as the North Pacific warms:

Dmitry V. Sein, Nikolay V. Koldunov, Joaquim G. Pinto, William Cabos, (2014), "Sensitivity of simulated regional Arctic climate to the choice of coupled model domain", Tellus A, 66, 23966, http://dx.doi.org/10.3402/tellusa.v66.23966

http://www.tellusa.net/index.php/tellusa/article/view/23966


Abstract: "The climate over the Arctic has undergone changes in recent decades. In order to evaluate the coupled response of the Arctic system to external and internal forcing, our study focuses on the estimation of regional climate variability and its dependence on large-scale atmospheric and regional ocean circulations. A global ocean–sea ice model with regionally high horizontal resolution is coupled to an atmospheric regional model and global terrestrial hydrology model. This way of coupling divides the global ocean model setup into two different domains: one coupled, where the ocean and the atmosphere are interacting, and one uncoupled, where the ocean model is driven by prescribed atmospheric forcing and runs in a so-called stand-alone mode. Therefore, selecting a specific area for the regional atmosphere implies that the ocean–atmosphere system can develop ‘freely’ in that area, whereas for the rest of the global ocean, the circulation is driven by prescribed atmospheric forcing without any feedbacks. Five different coupled setups are chosen for ensemble simulations. The choice of the coupled domains was done to estimate the influences of the Subtropical Atlantic, Eurasian and North Pacific regions on northern North Atlantic and Arctic climate. Our simulations show that the regional coupled ocean–atmosphere model is sensitive to the choice of the modelled area. The different model configurations reproduce differently both the mean climate and its variability. Only two out of five model setups were able to reproduce the Arctic climate as observed under recent climate conditions (ERA-40 Reanalysis). Evidence is found that the main source of uncertainty for Arctic climate variability and its predictability is the North Pacific. The prescription of North Pacific conditions in the regional model leads to significant correlation with observations, even if the whole North Atlantic is within the coupled model domain. However, the inclusion of the North Pacific area into the coupled system drastically changes the Arctic climate variability to a point where the Arctic Oscillation becomes an ‘internal mode’ of variability and correlations of year-to-year variability with observational data vanish. In line with previous studies, our simulations provide evidence that Arctic sea ice export is mainly due to ‘internal variability’ within the Arctic region. We conclude that the choice of model domains should be based on physical knowledge of the atmospheric and oceanic processes and not on ‘geographic’ reasons. This is particularly the case for areas like the Arctic, which has very complex feedbacks between components of the regional climate system."
“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 #264 on: August 13, 2014, 02:39:32 PM »
The linked 2013 article focuses on changes in the Arctic Ocean, and indicates that changes in the plankton there could result in a positive feedback (that will likely become more important with time) associated both with lower dimethyl sulphide production and lower CO2 absorption: 

http://www.egu.eu/news/76/tiny-plankton-could-have-big-impact-on-climate/

This article states:

""If the tiny plankton blooms, it consumes the nutrients that are normally also available to larger plankton species,” explains Ulf Riebesell, a professor of biological oceanography at the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany and head of the experimental team. This could mean the larger plankton run short of food.

Large plankton play an important role in carbon export to the deep ocean, but in a system dominated by the so-called pico- and nanoplankton, less carbon is transported out of surface waters. “This may cause the oceans to absorb less CO2 in the future,” says Riebesell.

The potential imbalance in the plankton food web may have an even bigger climate impact. Large plankton are also important producers of a climate-cooling gas called dimethyl sulphide, which stimulates cloud-formation over the oceans. Less dimethyl sulphide means more sunlight reaches the Earth’s surface, adding to the greenhouse effect. “These important services of the ocean may thus be significantly affected by acidification.”

Ecosystems in the Arctic are some of the most vulnerable to acidification because the cold temperatures here mean that the ocean absorbs more carbon dioxide. “Acidification is faster there than in temperate or tropical regions,” explains the coordinator of the European Project on Ocean Acidification (EPOCA), Jean-Pierre Gattuso of the Laboratory of Oceanography of Villefranche-sur-Mer of the French National Centre for Scientific Research (CNRS).

The increasing acidity is known to affect some calcifying organisms in the Arctic, including certain sea snails, mussels and other molluscs. But scientists did not know until now how ocean acidification alters both the base of the marine food web and carbon transport in the ocean. ..."


Furthermore, this article points to the free pdfs available on this topic from the following special issue of Biogenosciences

http://www.biogeosciences.net/special_issue120.html
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #265 on: August 13, 2014, 03:22:01 PM »
Sleepy,

Thanks for the post.  Methane "Dragon Breaths" are disconcerting even if that have been happening for many years now.  While they appear to be: local, short-term, hard to predict, and hard to identify the methane source, and it is not clear to me that their occurrence is accelerating (or not); they still give the general impression that both the above water, and below water, permafrost regions are degrading more rapidly than GCM projections would have us believe.

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

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #266 on: August 14, 2014, 07:15:23 PM »
Sleepy,

On some other "dragon breath" readings that I have noted in Alaska in past years, when I waited a few months and checked back the researchers had re-calibrated their readings downward.  So we need to check for such possible revisions to reported readings.  But nevertheless, with increasing climate warming we should expect both more frequent and larger "dragon breaths".

Thanks again,
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 #267 on: August 15, 2014, 12:58:19 AM »
We will all see soon enough (in the coming decade or two) what this implications of thinning snow cover is on the Arctic Sea Ice area/extent stability, as discussed in the following linked reference:

Melinda A. Webster, Ignatius G. Rigor, Son V. Nghiem, Nathan T. Kurtz, Sinead L. Farrell, Donald K. Perovich andMatthew Sturm, (2014), "Interdecadal changes in snow depth on Arctic sea ice", Journal of Geophysical Research: Oceans, DOI: 10.1002/2014JC009985

http://onlinelibrary.wiley.com/doi/10.1002/2014JC009985/abstract


Abstract: "Snow plays a key role in the growth and decay of Arctic sea ice. In winter, it insulates sea ice from cold air temperatures, slowing sea ice growth. From spring into summer, the albedo of snow determines how much insolation is absorbed by the sea ice and underlying ocean, impacting ice melt processes. Knowledge of the contemporary snow depth distribution is essential for estimating sea ice thickness and volume, and for understanding and modeling sea ice thermodynamics in the changing Arctic. This study assesses spring snow depth distribution on Arctic sea ice using airborne radar observations from Operation IceBridge for 2009-2013. Data were validated using coordinated in situ measurements taken in March 2012 during the BRomine, Ozone, and Mercury EXperiment (BROMEX) field campaign. We find a correlation of 0.59 and root-mean-square error of 5.8 cm between the airborne and in situ data. Using this relationship and IceBridge snow thickness products, we compared the recent results with data from the 1937, 1954-1991 Soviet drifting ice stations. The comparison shows thinning of the snow pack, from 35.1 ± 9.4 cm to 22.2 ± 1.9 cm in the western Arctic, and from 32.8 ± 9.4 cm to 14.5 ± 1.9 cm in the Beaufort and Chukchi seas. These changes suggest a snow depth decline of 37 ± 29% in the western Arctic and 56 ± 33% in the Beaufort and Chukchi seas. Thinning is negatively correlated with the delayed onset of sea ice freeze-up during autumn."
“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 #268 on: August 16, 2014, 11:28:17 AM »
Sorry if I'm a bit more OT. As for my little excursion into refrigerants and my personal take on it, in Reply #260. Daikin released their R32 units last year and I've been wondering all year why there's still no real action with those units in Europe.
Here's the answer: http://www.coolingpost.com/uk-news/daikin-uk-in-no-hurry-with-r32/

And a quote.
“We should not forget that we do not have to start selling units with a GWP below 750 and a charge less than 3kg until 2025 so there is time for us to make the right choices along with the rest of the industry,” he said."

I seriously beg to differ...

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #269 on: August 16, 2014, 06:58:51 PM »
The linked reference indicates that for high rates of GHG emissions (such as we have now) "… there is little chance of a hiatus decade occurring beyond 2030, even in the event of a large volcanic eruption.  We further demonstrate that most non-volcanic hiatuses across CMIP5 models are associated with enhanced cooling in the equatorial Pacific linked to the transition to a negative IPO phase."

As I believe that we are now entering a positive phase of the IPO, this research implies that we may never see another negative phase of the IPO (in the foreseeable future); which implies that for the past couple of decades we have been living in a transitory "Faustian" paradise and that we are about to enter a "Faustian" inferno:

a) As La Nina's become less frequent and as El Nino's vent more sequestered heat from the ocean;
 b) As China cleans-up its aerosol emission;
c) As the North Pacific comes in sync with the North Atlantic in order to accelerate Arctic amplification;
d) As the permafrost (both on land and underwater) degradation accelerates;
e) As ocean acidification suppresses the production of dimethylsulphide (DMS);
f) As NH albedo increases due to reduced Arctic Sea Ice extent, reduced NH snow cover, and increased plant growth in the northern latitudes;
g) As the Arctic atmospheric OH supply diminishes thus increasing the GWP of regional atmospheric CH4;
h) As the frequency and extent of wildfires increase;
i) As the size of plankton diminishes, thus making it more difficult for the oceans to sequester CO₂;
j) As increasing upwelling (particularly in the Southern Ocean) increases CO₂ venting from the oceans;
k) As heat stress decreases the ability of terrestrial plants to sequester CO₂;
l) As world populations continue to grow and demand for energy, more meat and more material wealth;
m) As the amount of volatile organic compounds (VOCs) emitted by forests decrease (due to climate change related stress).

While I could go on, readers can review other posts in this trend for other positive forcing threats:


Nicola Maher, Alexander Sen Gupta and Matthew H. England, (2014), "Drivers of decadal hiatus periods in the 20th and 21st Centuries", Geophysical Research Letters, DOI: 10.1002/2014GL060527


http://onlinelibrary.wiley.com/doi/10.1002/2014GL060527/abstract


Abstract: "The latest generation of climate model simulations are used to investigate the occurrence of hiatus periods in global surface air temperature in the past and under two future warming scenarios. Hiatus periods are identified in three categories, (i) those due to volcanic eruptions, (ii) those associated with negative phases of the Interdecadal Pacific Oscillation (IPO) and (iii) those affected by anthropogenically released aerosols in the mid 20th Century. The likelihood of future hiatus periods is found to be sensitive to the rate of change of anthropogenic forcing. Under high rates of greenhouse gas emissions there is little chance of a hiatus decade occurring beyond 2030, even in the event of a large volcanic eruption. We further demonstrate that most non-volcanic hiatuses across CMIP5 models are associated with enhanced cooling in the equatorial Pacific linked to the transition to a negative IPO phase."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #270 on: August 17, 2014, 04:02:44 PM »
While I have linked to the following reference before regarding both the Antarctic Peninsula temperatures and the relation of the AMO to both AABW production and to the ABSL (which I related to CDW advection into the ASE).  However, now I would like to speculate on a possible delayed relationship between the AMO and the PDO, which could result in a significant warming of the North Pacific between now and 2040 in the same way that the Antarctic Peninsula is now the region on Earth with the most rapid surface warming:

Xichen Li,   David M. Holland, Edwin P. Gerber & Changhyun Yoo, (2014), "Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice", Nature 505, 538–542, doi:10.1038/nature12945


http://www.nature.com/nature/journal/v505/n7484/full/nature12945.html


Abstract: "In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming of any region on the planet, causing rapid changes in land ice. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution. Antarctic climate is influenced by, among other factors, changes in radiative forcing and remote Pacific climate variability, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen–Bellingshausen–Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation and sea-level change."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #271 on: August 18, 2014, 05:16:25 PM »
The attached SSTA image for the week of August 6 2014 illustrates the possibility that the North Pacific may be coming into synchronicity with the North Atlantic, as suggested by the following references:

Nicola Maher, Alexander Sen Gupta and Matthew H. England, (2014), "Drivers of decadal hiatus periods in the 20th and 21st Centuries", Geophysical Research Letters, DOI: 10.1002/2014GL060527

Seon Tae Kim, Wenju Cai, Fei-Fei Jin, Agus Santoso, Lixin Wu, Eric Guilyardi & Soon-Il An, (2014), "Response of El Niño sea surface temperature variability to greenhouse warming", Nature Climate Change, doi:10.1038/nclimate2326

Summer K. Praetorius, Alan C. Mix, (2014), "Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming", Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000

McGregor, S., A. Timmermann, M. F. Stuecker, M. H. England, M. Merrifield, F.-F. Jin and Y. Chikamoto, (2014), "Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming", Nature Climate Change; doi:10.1038/nclimate2330

Brigham-Grette, Julie; Melles, Martin; Minyuk, Pavel, et al., (2013) "Millennial scale change from Lake El’gygytgyn, NE Russia: Did we step or leap out of the Warm Pliocene into the Pleistocene?"
http://instaar.colorado.edu/meetings/AW2013/abstract_details.php?abstract_id=78
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #272 on: August 19, 2014, 03:55:10 PM »
The linked reference (with a free access pdf) indicates that deep-sea trawling disturbs the sequestration of carbon in the deep-sea trawled portion of the ocean, so that instead of settling to the seafloor, the disturbed carbon may acidify seawater, and/or escape into the atmosphere:


Antonio Pusceddu, Silvia Bianchelli, Jacobo Martín, Pere Puig, Albert Palanques, Pere Masqué, and Roberto Danovaro, (May 19, 2014), "Chronic and intensive bottom trawling impairs deep-sea biodiversity and ecosystem functioning", PNAS, doi: 10.1073/pnas.1405454111



http://www.pnas.org/content/early/2014/05/14/1405454111.full.pdf+html


Abstract: "Bottom trawling has many impacts on marine ecosystems, including seafood stock impoverishment, benthos mortality, and sediment resuspension. Historical records of this fishing practice date back to the mid-1300s. Trawling became a widespread practice in the late 19th century, and it is now progressively expanding to greater depths, with the concerns about its sustainability that emerged during the first half of the 20th century now increasing. We show here that compared with untrawled areas, chronically trawled sediments along the continental slope of the north-western Mediterranean Sea are characterized by significant decreases in organic matter content (up to 52%), slower organic carbon turnover (ca. 37%), and reduced meiofauna abundance (80%), biodiversity (50%), and nematode species richness (25%). We estimate that the organic carbon removed daily by trawling in the region under scrutiny represents as much as 60–100% of the input flux. We anticipate that such an impact is causing the degradation of deep-sea sedimentary habitats and an infaunal depauperation. With deep-sea trawling currently conducted along most continental margins, we conclude that trawling represents a major threat to the deep seafloor ecosystem at the global scale."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #273 on: August 20, 2014, 04:28:44 PM »
The linked reference (with a free access pdf) indicates that the leakage of warm saline water from the Agulhas Current into the Atlantic Ocean (see attached image), caused a positive feedback mechanism contributing to polar amplification during the Eemian; and that this mechanism could become increasingly important with increasing global warming today:

Turney, C. S.M. and Jones, R. T. (2010), Does the Agulhas Current amplify global temperatures during super-interglacials?. J. Quaternary Sci., 25: 839–843. doi: 10.1002/jqs.1423

http://onlinelibrary.wiley.com/doi/10.1002/jqs.1423/full

Abstract: "Future projections of climate suggest our planet is moving into a ‘super-interglacial’. Here we report a global synthesis of ice, marine and terrestrial data from a recent palaeoclimate equivalent, the Last Interglacial (ca. 130–116 ka ago). Our analysis suggests global temperatures were on average ∼1.5°C higher than today (relative to the AD 1961–1990 period). Intriguingly, we identify several Indian Ocean Last Interglacial sequences that suggest persistent early warming, consistent with leakage of warm, saline waters from the Agulhas Current into the Atlantic, intensifying meridional ocean circulation and increasing global temperatures. This mechanism may have played a significant positive feedback role during super-interglacials and could become increasingly important in the future. These results provide an important insight into a future 2°C climate stabilisation scenario."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #274 on: August 20, 2014, 04:42:27 PM »
The linked reference indicates that polar amplification contributed directly to summer temperatures being about 8 degrees C higher about 3.6 to 3.4 million years ago (when the partial pressure of CO₂ was about 400 ppm) than today.  This provides a strong cautionary note that as modern global warming continues, climate sensitivity is likely higher that currently assumed in the CMIP5 GCM projections:

Julie Brigham-Grette, Martin Melles, Pavel Minyuk, Andrei Andreev, Pavel Tarasov, Robert DeConto, Sebastian Koenig, Norbert Nowaczyk, Volker Wennrich, Peter Rosén, Eeva Haltia, Tim Cook, Catalina Gebhardt, Carsten Meyer-Jacob, Jeff Snyder, Ulrike Herzschuh, (2013), "Pliocene Warmth, Polar Amplification, and Stepped Pleistocene Cooling Recorded in NE Arctic Russia", Science, Vol. 340 no. 6139 pp. 1421-1427, DOI: 10.1126/science.1233137


http://www.sciencemag.org/content/340/6139/1421.abstract


Abstract: "Understanding the evolution of Arctic polar climate from the protracted warmth of the middle Pliocene into the earliest glacial cycles in the Northern Hemisphere has been hindered by the lack of continuous, highly resolved Arctic time series. Evidence from Lake El’gygytgyn, in northeast (NE) Arctic Russia, shows that 3.6 to 3.4 million years ago, summer temperatures were ~8°C warmer than today, when the partial pressure of CO2 was ~400 parts per million. Multiproxy evidence suggests extreme warmth and polar amplification during the middle Pliocene, sudden stepped cooling events during the Pliocene-Pleistocene transition, and warmer than present Arctic summers until ~2.2 million years ago, after the onset of Northern Hemispheric glaciation. Our data are consistent with sea-level records and other proxies indicating that Arctic cooling was insufficient to support large-scale ice sheets until the early Pleistocene."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #275 on: August 22, 2014, 04:45:40 PM »
The following linked reference states: "… that slowdown is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans, initiated by a recurrent salinity anomaly in the subpolar North Atlantic. Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years."  Michael Mann previously discussed this response (see Reply #151 in the "Potential Collapse Scenario for the WAIS" thread), while recent analysis indicates that the North Pacific will come into sync with the North Atlantic to promote global warming for the next 15 to 25 years (see Reply #280 in this thread):


Xianyao Chen, & Ka-Kit Tung, (2014), "Varying planetary heat sink led to global-warming slowdown and acceleration", Science, Vol. 345, no. 6199 pp. 897-903, DOI: 10.1126/science.1254937


http://www.sciencemag.org/content/345/6199/897


Abstract: "A vacillating global heat sink at intermediate ocean depths is associated with different climate regimes of surface warming under anthropogenic forcing: The latter part of the 20th century saw rapid global warming as more heat stayed near the surface. In the 21st century, surface warming slowed as more heat moved into deeper oceans. In situ and reanalyzed data are used to trace the pathways of ocean heat uptake. In addition to the shallow La Niña–like patterns in the Pacific that were the previous focus, we found that the slowdown is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans, initiated by a recurrent salinity anomaly in the subpolar North Atlantic. Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #276 on: August 22, 2014, 04:47:44 PM »
The linked reference provides evidence that CO₂ emissions from permafrost degradation will likely be higher than previously expected

Rose M. Cory, Collin P. Ward, Byron C. Crump, George W. Kling, (2014), "Sunlight controls water column processing of carbon in arctic fresh waters", Science, Vol. 345, no. 6199 pp. 925-928, DOI: 10.1126/science.1253119


http://www.sciencemag.org/content/345/6199/925


Abstract: "Carbon in thawing permafrost soils may have global impacts on climate change; however, the factors that control its processing and fate are poorly understood. The dominant fate of dissolved organic carbon (DOC) released from soils to inland waters is either complete oxidation to CO2 or partial oxidation and river export to oceans. Although both processes are most often attributed to bacterial respiration, we found that photochemical oxidation exceeds rates of respiration and accounts for 70 to 95% of total DOC processed in the water column of arctic lakes and rivers. At the basin scale, photochemical processing of DOC is about one-third of the total CO2 released from surface waters and is thus an important component of the arctic carbon budget."



See also:
http://www.laboratoryequipment.com/news/2014/08/sunlight-controls-fate-permafrosts-released-carbon

Extract: "… researchers show for the first time that sunlight, not microbial activity, dominates the production of carbon dioxide in Arctic inland waters.
"Our results suggest that sunlight, rather than biological processes, controls the fate of carbon released from thawing permafrost soils into Arctic surface waters," said aquatic geochemist Rose Cory, first author of the Science paper and an assistant professor in the U-M Department of Earth and Environmental Sciences.
Last year, the same team reported in PNAS that recently exposed carbon from thawed Alaskan permafrost is extremely sensitive to sunlight and can quickly be converted to carbon dioxide. Taken together, the two studies suggest that "we're likely to see more carbon dioxide released from thawing permafrost than people had previously believed," Cory said."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #277 on: August 23, 2014, 04:14:43 PM »
Many recent internet articles have referenced the Chen & Tung (2014) paper (about the possibility that the absorption of heat by the Atlantic Ocean, is primarily responsible for the global warming hiatus) while stating that the world should have about another 15-years of suppressed rates of global warming [see: Chen, X. & Tung, K.-K., (2014), "Varying planetary heat sink led to global-warming slowdown and acceleration", Science, Vol. 345, no. 6199, pp. 897-903, DOI: 10.1126/science.1254937].  This is premised on the assumptions that the AMO has about a 70-year period (so 35-year of heat and 35-years of cooling) and that the 35-year cooling period peaked in 2006, which could leave about 10-years of further cooling, assuming the AMO cycle is the dominate natural oscillation affecting mean global surface warming.

Nevertheless, many prominent scientists (who I agree with) indicate that they believe that the Chen & Tung (2014) conclusions are too simplistic, and that the larger story certainly includes interactions between the Pacific, Atlantic, Indian and Southern Oceans (not to mention aerosols, bio-cycles and numerous other feedback mechanisms).  Indeed, the first linked internet article writes:

Extract: "There is some heat going into the Atlantic, writes Kevin Trenberth, a researcher at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, in an email. But Trenberth—who was not involved in the current study—disagrees with how it's getting there.
Trenberth argues that processes in the Pacific Ocean drive changes in the North Atlantic current. The same basic mechanism that may drive heat into the Pacific—intense trade winds that pile up warm water in the western Pacific—has large ripple effects on the atmosphere.
Those ripples influence jet streams, or currents of air flowing through the atmosphere, across the U.S., and over the North Atlantic Ocean. And those atmospheric currents can drive changes in ocean currents."

http://news.nationalgeographic.com/news/2014/08/140821-global-warming-hiatus-climate-change-ocean-science/

Also the second linked article writes:

Extract: "Richard Alley, a geoscientist at Pennsylvania State University in University Park, says the study is interesting — “but whether it’s a completely different story or part of the same story is something I think is still coming out.”

Alley welcomes the focus on the Atlantic, however. “Those of us who work in palaeoclimate have for a very long time had an idea that the Atlantic matters,” he says. “The evidence from the ice ages is that there were huge North Atlantic changes that show up in climate records all over the world.”"

http://www.nature.com/news/atlantic-ocean-key-to-global-warming-pause-1.15755?utm_source=dlvr.it&utm_medium=tumblr


While Kim et al (2014) indicates that before 2040 CMIP5 models indicate that the amplitude of the ENSO phases will increase, indicating that when the El Nino events return for the next 25-years they are likely to be stronger than previously experienced leading to more abrupt climate change [see: Seon Tae Kim, Wenju Cai, Fei-Fei Jin, Agus Santoso, Lixin Wu, Eric Guilyardi & Soon-Il An, (2014), "Response of El Niño sea surface temperature variability to greenhouse warming", Nature Climate Change, doi:10.1038/nclimate2326].

Furthermore, McGregor et al (2014) illustrate the interaction between the Pacific, and Atlantic, Oceans [see: McGregor, S., A. Timmermann, M. F. Stuecker, M. H. England, M. Merrifield, F.-F. Jin and Y. Chikamoto, (2014), "Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming", Nature Climate Change; doi:10.1038/nclimate2330].

Also, Praetorius & Mix (2014) provide paleo-evidence of the importance of the synchronization of the North Pacific, and the North Atlantic, Oceans on Artic amplification: Summer K. Praetorius, Alan C. Mix, (2014), "Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming", Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000

Also the importance of the Pacific Ocean is indicated in: Nicola Maher, Alexander Sen Gupta and Matthew H. England, (2014), "Drivers of decadal hiatus periods in the 20th and 21st Centuries", Geophysical Research Letters, DOI: 10.1002/2014GL060527.

Also, for the important influence of the Indian see: Turney, C. S.M. and Jones, R. T. (2010), Does the Agulhas Current amplify global temperatures during super-interglacials?. J. Quaternary Sci., 25: 839–843. doi: 10.1002/jqs.1423.

Also, the importance of the surface melting of the Greenland Ice Sheet (see the attached figure of the extremely high recent GIS surface melting) is discussed in: Xu Zhang, Gerrit Lohmann, Gregor Knorr & Conor Purcell, (2014), "Abrupt glacial climate shifts controlled by ice sheet changes", Nature, doi:10.1038/nature13592.

In my opinion there are multiple masking factors contributing to the recent global warming hiatus, and that with strong anthropogenic radiative forcing, many of these masking factors will be gone in the next 10-years; which will reveal both a higher Equilibrium Climate Sensitivity, ECS, than 3 degrees C, and will cause a surge of mean global warming that will push many Earth Systems past tipping points that will accelerate long-term positive feedback factors such as accelerated: permafrost degradation, increase in NH albedo, and decreased absorption of heat by the ocean.
« Last Edit: August 23, 2014, 04:25:20 PM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #278 on: August 23, 2014, 04:41:57 PM »
Further to my last post, the linked Msadek et al (2014) reference confirms that as we return to a warm phase of the Atlantic Meridional Overturning Circulation (AMOC), and similarly the warm phase of the Atlantic Multidecadal Oscillation (AMO) within the next 10-years, that Arctic Sea Ice area:

Rym Msadek, T. L. Delworth, A. Rosati, W. Anderson, G. A. Vecchi, Y.-S. Chang, K. Dixon, R. G. Gudgel, W. Stern, A. Wittenberg, X. Yang, F. Zeng, R. Zhang, and S. Zhang, (2014), "Predicting a decadal shift in North Atlantic climate variability using the GFDL forecast system", Journal of Climate. DOI: 10.1175/JCLI-D-13-00476.1.

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00476.1

Abstract: "Decadal prediction experiments were conducted as part of CMIP5 using the GFDL-CM2.1 forecast system. The abrupt warming of the North Atlantic subpolar gyre (SPG) that was observed in the mid 1990s is considered as a case study to evaluate our forecast capabilities and better understand the reasons for the observed changes. Initializing the CM2.1 coupled system produces high skill in retrospectively predicting the mid-90s shift, which is not captured by the uninitialized forecasts. All the hindcasts initialized in the early 90s show a warming of the SPG, however, only the ensemble mean hindcasts initialized in 1995 and 1996 are able to reproduce the observed abrupt warming and the associated decrease and contraction of the SPG. Examination of the physical mechanisms responsible for the successful retrospective predictions indicates that initializing the ocean is key to predict the mid 90s warming. The successful initialized forecasts show an increased Atlantic Meridional Overturning Circulation and North Atlantic current transport, which drive an increased advection of warm saline subtropical waters northward, leading to a westward shift of the subpolar front and subsequently a warming and spin down of the SPG. Significant seasonal climate impacts are predicted as the SPG warms, including a reduced sea-ice concentration over the Arctic, an enhanced warming over central US during summer and fall, and a northward shift of the mean ITCZ. These climate anomalies are similar to those observed during a warm phase of the Atlantic Multidecadal Oscillation, which is encouraging for future predictions of North Atlantic climate."
« Last Edit: August 23, 2014, 04:47:13 PM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #279 on: August 23, 2014, 04:47:36 PM »
The linked reference indicates (based on data from a snow pit at the South Pole from 1984-2001), that as we enter a positive IPO phase with increased frequency and intensity of El Nino events, we can expect a marked increase in wildfires, that on balance will act as positive feedback mechanism:

Robina Shaheen, Mariana M. Abaunza, Teresa L. Jackson, Justin McCabe, Joël Savarino, and Mark H. Thiemens, (2014), "Large sulfur-isotope anomaly in nonvolcanic sulfate aerosol and its implications for the Archean atmosphere", PNAS, doi: 10.1073/pnas.1406315111.

http://www.pnas.org/content/early/2014/08/01/1406315111

Abstract: Sulfur-isotopic anomalies have been used to trace the evolution of oxygen in the Precambrian atmosphere and to document past volcanic eruptions. High-precision sulfur quadruple isotope measurements of sulfate aerosols extracted from a snow pit at the South Pole (1984–2001) showed the highest S-isotopic anomalies (Δ33S = +1.66‰ and Δ36S = +2‰) in a nonvolcanic (1998–1999) period, similar in magnitude to Pinatubo and Agung, the largest volcanic eruptions of the 20th century. The highest isotopic anomaly may be produced from a combination of different stratospheric sources (sulfur dioxide and carbonyl sulfide) via SOx photochemistry, including photoexcitation and photodissociation. The source of anomaly is linked to super El Niño Southern Oscillation (ENSO) (1997–1998)-induced changes in troposphere–stratosphere chemistry and dynamics. The data possess recurring negative S-isotope anomalies (Δ36S = −0.6 ± 0.2‰) in nonvolcanic and non-ENSO years, thus requiring a second source that may be tropospheric. The generation of nonvolcanic S-isotopic anomalies in an oxidizing atmosphere has implications for interpreting Archean sulfur deposits used to determine the redox state of the paleoatmosphere."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #280 on: August 26, 2014, 08:18:43 AM »
The linked reference has identified a significant increase in observed methane venting from the US Atlantic margin, many of which are probably associated with the decomposition of methane hydrates due to ongoing warming of intermediate waters, while some of the seeps may have been around for over 1,000 years.  The researcher project that there might be tens of thousands more scattered around the world, and this potentially high number of methane seeps could mean that we are dealing with a significant and heretofore unknown, and probably increasing, new source of greenhouse gases (see also discussion in the Science folder).


A. Skarke, C. Ruppel, M. Kodis, D. Brothers, & E. Lobecker, (2014), "Widespread methane leakage from the sea floor on the northern US Atlantic margin", Nature Geoscience, doi:10.1038/ngeo2232

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2232.html

Abstract: "Methane emissions from the sea floor affect methane inputs into the atmosphere1, ocean acidification and de-oxygenation, the distribution of chemosynthetic communities and energy resources. Global methane flux from seabed cold seeps has only been estimated for continental shelves, at 8 to 65 Tg CH4 yr−1, yet other parts of marine continental margins are also emitting methane. The US Atlantic margin has not been considered an area of widespread seepage, with only three methane seeps recognized seaward of the shelf break. However, massive upper-slope seepage related to gas hydrate degradation has been predicted for the southern part of this margin, even though this process has previously only been recognized in the Arctic. Here we use multibeam water-column backscatter data that cover 94,000 km2 of sea floor to identify about 570 gas plumes at water depths between 50 and 1,700 m between Cape Hatteras and Georges Bank on the northern US Atlantic passive margin. About 440 seeps originate at water depths that bracket the updip limit for methane hydrate stability. Contemporary upper-slope seepage there may be triggered by ongoing warming of intermediate waters, but authigenic carbonates observed imply that emissions have continued for more than 1,000 years at some seeps. Extrapolating the upper-slope seep density on this margin to the global passive margin system, we suggest that tens of thousands of seeps could be discoverable."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #281 on: August 28, 2014, 11:22:25 PM »
The following link provides very current and accurate information about world population and projections to 2100, including the attached graph showing a projection of a world population of 10.85 Billion people by July 1 2100 (the second attachment shows an associated table that gives dates for population milestones):

http://www.worldometers.info/world-population/
« Last Edit: August 29, 2014, 12:33:04 AM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #282 on: August 29, 2014, 01:14:15 AM »
Cloud radiative forcing (CRF) is a positive feedback factor for global warming, and according to the linked reference CRF from Tropical and Subtropical high cloud cover will increase with increasing global warming (thus increasing Equilibrium Climate Sensitivity with increasing warming):

A. T. Noda, M. Satoh, Y. Yamada, C. Kodama, and T. Seiki, (2014), "Responses of Tropical and Subtropical High-Cloud Statistics to Global Warming", Journal of Climate 2014 ; doi: http://dx.doi.org/10.1175/JCLI-D-14-00179.1


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00179.1

Abstract: "Data from global high-resolution, nonhydrostatic simulations, covering a period of one year and with horizontal grid sizes of 7 and 14 km, were analyzed to evaluate the response of high cloud to global warming. The results indicate that, in a warmer atmosphere, high cloud cover increases robustly, and associated longwave (LW) cloud radiative forcing (CRF) increases on average. To develop a better understanding of high-cloud responses to climate change, the geographical distribution of high-cloud size obtained from the model was analyzed and compared with observations. In warmer atmospheres, the contribution per cloud to CRF decreases for both the LW and shortwave (SW) components. However, because of significant increases in the numbers of high clouds in almost all cloud-size categories, the magnitude of both LW and SW CRF increases in the simulations. In particular, the contribution from an increase in the number of smaller clouds has more effect on the CRF change. It was also found that the ice and liquid-water paths decrease in smaller clouds and that particularly the former contributes to reduced LW CRF per high cloud."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #283 on: August 29, 2014, 05:01:20 PM »
Regarding the impact of atmospheric and ocean forcing on ice sheet mass balance (particularly on the WAIS mass loss) I provide the following quote from the 2014 SCAR conference in New Zealand:

"Projections of ice-sheet mass balance over the next centuries strongly depend on the atmospheric and oceanic forcings. During IPCC AR5, several groups produced projections but the methods to force the ice-sheet models differed substantially. One difficulty is that, within IPCC’s framework, atmospheric and oceanic fields from coupled AOGCMs are necessary but are available only by the end of an IPCC Assessment, too late to be used by ice-sheet modelers for their own simulations. Methods used to initialize ice-sheet models, to downscale AOGCM fields, to take into account surface mass balance-elevation feedbacks and to use ocean characteristics to initiate dynamic response of the ice sheets (calving, grounding line retreat) are other subjects that have been treated very differently by the various groups. We should take advantage of the variety of methods applied during AR5 to compare them and evaluate their impact on the results. The aims are improving the methods and agreeing on a common framework when producing ice-sheet mass balance model projections for the next 100 years. This should help to derive realistic ranges of uncertainties in ice-sheet projections."

As much of the increase in ocean heat content has been going to the Southern Ocean, the two attached images of steric contribution (which is dominated by heat content) to SLR from NOAA through June of 2014 for 0-700m, and 0 to 2000m, respectively, indicate that ocean heat content is still (though June 2014) increasing rapidly, which will increase Antarctic ice mass loss; whether the AOGCM projections correctly account for this major forcing factor, or not:

http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #284 on: August 31, 2014, 05:40:04 PM »
In the linked reference (see also the following reply), some of the main authors of the RCP scenarios concur with Shindell (2014) that the latest generation of climate models use values of climate sensitivity that are biased towards the low side.  Therefore, it is likely that future forcing scenarios will be calibrated towards higher values of climate sensitivity:

Steven J. Smith, Tom M. L. Wigley, Malte Meinshausen & Joeri Rogelj, (2014), "Questions of bias in climate models", Nature Climate Change, Volume: 4, Pages: 741–742, doi:10.1038/nclimate2345

http://www.nature.com/nclimate/journal/v4/n9/full/nclimate2345.html


Drew Shindell, (2014), "Reply to 'Questions of bias in climate models'", Nature Climate Change, Volume: 4, Pages: 742–743, doi:10.1038/nclimate2346

http://www.nature.com/nclimate/journal/v4/n9/full/nclimate2346.html
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #285 on: September 02, 2014, 04:30:21 AM »
The linked reference demonstrates the importance of both the lapse rate, and surface albedo, feedbacks on polar amplification in both the Arctic and more so in the Antarctic:

Rune G. Graversen, Peter L. Langen, and Thorsten Mauritsen, 2014: Polar Amplification in CCSM4: Contributions from the Lapse Rate and Surface Albedo Feedbacks. J. Climate, 27, 4433–4450.
doi: http://dx.doi.org/10.1175/JCLI-D-13-00551.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00551.1

Abstract: "A vertically nonuniform warming of the troposphere yields a lapse rate feedback by altering the infrared irradiance to space relative to that of a vertically uniform tropospheric warming. The lapse rate feedback is negative at low latitudes, as a result of moist convective processes, and positive at high latitudes, due to stable stratification conditions that effectively trap warming near the surface. It is shown that this feedback pattern leads to polar amplification of the temperature response induced by a radiative forcing. The results are obtained by suppressing the lapse rate feedback in the Community Climate System Model, version 4 (CCSM4). The lapse rate feedback accounts for 15% of the Arctic amplification and 20% of the amplification in the Antarctic region. The fraction of the amplification that can be attributed to the surface albedo feedback, associated with melting of snow and ice, is 40% in the Arctic and 65% in Antarctica. It is further found that the surface albedo and lapse rate feedbacks interact considerably at high latitudes to the extent that they cannot be considered independent feedback mechanisms at the global scale."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #286 on: September 03, 2014, 04:26:26 AM »
The linked research indicates that the longer melt season (and associated wind-driven vertical ocean water mixing and associate upwelling of nutrients) in the Arctic Ocean is resulting in a phytoplankton bloom in the boreal Fall (on top of the current bloom in the Spring).  This acts as a positive feedback mechanism both due to: (a) decrease albedo, and (b) the size of the phytoplankton is decreasing, so they do not sink and sequester CO2 as well as the past (large) plankton (i.e. resulting in reduced CO2 absorption):

Ardyna, M., M. Babin, M. Gosselin, E. Devred, L. Rainville, and J.-É. Tremblay (2014), Recent Arctic Ocean sea ice loss triggers novel fall phytoplankton blooms, Geophys. Res. Lett., 41, doi:10.1002/2014GL061047.

http://onlinelibrary.wiley.com/doi/10.1002/2014GL061047/abstract

Abstract: "Recent receding of the ice pack allows more sunlight to penetrate into the Arctic Ocean, enhancing productivity of a single annual phytoplankton bloom. Increasing river runoff may, however, enhance the yet pronounced upper ocean stratification and prevent any significant wind-driven vertical mixing and upward supply of nutrients, counteracting the additional light available to phytoplankton. Vertical mixing of the upper ocean is the key process that will determine the fate of marine Arctic ecosystems. Here we reveal an unexpected consequence of the Arctic ice loss: regions are now developing a second bloom in the fall, which coincides with delayed freeze up and increased exposure of the sea surface to wind stress. This implies that wind-driven vertical mixing during fall is indeed significant, at least enough to promote further primary production. The Arctic Ocean seems to be experiencing a fundamental shift from a polar to a temperate mode, which is likely to alter the marine ecosystem."


See also:
http://www.adn.com/article/20140901/study-sparser-thinner-arctic-ocean-ice-enabling-new-phytoplankton-blooms
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #287 on: September 08, 2014, 05:59:29 PM »
The linked reference indicates that with warming temperatures, microbes in the soil give off more carbon dioxide, a process that would act as a positive feedback factor, thus amplify climate change.


Kristiina Karhu, Marc D. Auffret, Jennifer A. J. Dungait, David W. Hopkins, James I. Prosser, Brajesh K. Singh, Jens-Arne Subke, Philip A. Wookey, Göran I. Ågren, Maria-Teresa Sebastià, Fabrice Gouriveau, Göran Bergkvist, Patrick Meir, Andrew T. Nottingham, Norma Salinas & Iain P. Hartley,  "Temperature sensitivity of soil respiration rates enhanced by microbial community response", Nature, 513, 81–84, doi:10.1038/nature13604


http://www.nature.com/nature/journal/v513/n7516/full/nature13604.html


Abstract: "Soils store about four times as much carbon as plant biomass, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease or increase warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #288 on: September 09, 2014, 08:30:28 PM »
The linked reference shows that a team of researchers from the US National Center for Atmospheric Research (NCAR) and the Centre for Australian Weather and Climate Research (CAWCR) demonstrated that, in certain conditions, current climate models can simulate the pause/hiatus.  This implies that as we leave the pause/hiatus period (that occurred due to natural variability, see the attached figure), that we are moving into a period of accelerated global warming:

Meehl, Gerald A., Haiyan Teng, and Julie M. Arblaster, “Climate model simulations of the observed early-2000s hiatus of global warming,” Nature Climate Change (2014), doi:10.1038/nclimate2357

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2357.html

Abstract: "The slowdown in the rate of global warming in the early 2000s is not evident in the multi-model ensemble average of traditional climate change projection simulations. However, a number of individual ensemble members from that set of models successfully simulate the early-2000s hiatus when naturally-occurring climate variability involving the Interdecadal Pacific Oscillation (IPO) coincided, by chance, with the observed negative phase of the IPO that contributed to the early-2000s hiatus. If the recent methodology of initialized decadal climate prediction could have been applied in the mid-1990s using the Coupled Model Intercomparison Project Phase 5 multi-models, both the negative phase of the IPO in the early 2000s as well as the hiatus could have been simulated, with the multi-model average performing better than most of the individual models. The loss of predictive skill for six initial years before the mid-1990s points to the need for consistent hindcast skill to establish reliability of an operational decadal climate prediction system."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #289 on: September 11, 2014, 02:05:52 AM »
According to the Union of Concerned Scientists, climate change has accelerated the deaths of tens of millions of trees in the Rocky Mountains over the past 15 years, victims of a triple assault of tree-killing insects, wildfires, and stress from heat and drought.  The first link leads to a free pdf of the Executive Summary and the second link leads to a free pdf of the 2014 full report:

http://www.ucsusa.org/assets/documents/global_warming/Rocky-Mountain-Forests-at-Risk-Executive-Summary.pdf

http://www.ucsusa.org/assets/documents/global_warming/Rocky-Mountain-Forests-at-Risk-Full-Report.pdf
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #290 on: September 11, 2014, 04:58:36 PM »
The WMO (World Meteorological Org) & the UNEP (UN Environment Programme), have issued their "Assessment for Decision-Makers - Scientific Assessment of Ozone Depletion: 2014" report, and a free access pdf of this report can be found at the following link:

http://montreal-protocol.org/Assessment_Panels/SAP/SAP2014_Assessment_for_Decision-Makers.pdf

While the report is somewhat optimistic about the global ozone situation, the situation in the Antarctic is in my opinion less optimistic as the ozone hole over Antarctica: (a) has already had much more impact on ice mass loss in Antarctica than would have occurred without the current hole (see the first attached image); (b) is projected to be slower to recover than in the rest of the world (see the second attached image comparing the Arctic situation with the Antarctic situation); and (c) is projected to gradually heal over the coming decades, nevertheless due to projected increases in GHG (see the third attached image showing different possible impacts of HFC's) it is likely that the geopotential well over Antarctic (caused by the current ozone hole) will be maintained by the increase in GHG, which will maintain the high Westerly winds and the associated melting of Antarctic ice shelf, and ice sheet, basal ice from upwelling warm CDW.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #291 on: September 12, 2014, 05:46:56 PM »
The linked internet article discusses many of the reasons to be concerned about the risks of HFC's that I briefly discussed in my immediate preceding post (Reply #299):

https://news.vice.com/article/the-recovery-of-the-ozone-layer-isnt-all-good-news
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #292 on: September 12, 2014, 06:28:27 PM »
The linked reference discusses the tight teleconnection between the positive SST skewness associated with ENSO during recent decades, and the warming of the Indian Ocean SSTs.  It should be noted that if/when warm water leaks from the Western Indian Ocean into the South Atlantic Ocean (see Reply #282), this could accelerate global warming due to associated changes in the Atlantic Meridional Overturning Circulation, AMOC:

Mathew Koll ROXY, Kapoor RITIKA, Pascal TERRAY, and Sébastien MASSON, (2014), "The curious case of Indian Ocean warming", Journal of Climate 2014 ; e-View

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00471.1?af=R


Abstract: "Recent studies have pointed out an increased warming over the Indian Ocean warm pool (central-east Indian Ocean characterized by sea surface temperatures greater than 28.0°C) during the past half-century, though the reasons behind this monotonous warming are still debated. The results here reveal a larger picture–that the western tropical Indian Ocean has been warming for more than a century, at a rate faster than any other region of the tropical oceans, and turns out to be the largest contributor to the overall trend in the global mean sea surface temperature (SST). During 1901-2012, while the Indian Ocean warm pool went through an increase of 0.7°C, the western Indian Ocean experienced anomalous warming of 1.2°C in summer SSTs. The warming of the generally cool western Indian Ocean against the rest of the tropical warm pool region alters the zonal SST gradients, and has the potential to change the Asian monsoon circulation and rainfall, as well as alter the marine food webs in this biologically productive region. The current study using observations and global coupled ocean-atmosphere model simulations gives compelling evidence that, besides direct contribution from greenhouse warming, the long-term warming trend over the western Indian Ocean during summer is highly dependent on the asymmetry in the El Niño Southern Oscillation (ENSO) teleconnection, and the positive SST skewness associated with ENSO during recent decades."
« Last Edit: September 12, 2014, 06:45:15 PM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #293 on: September 12, 2014, 06:34:21 PM »
A  co-ordinated 21 million dollar study to deploy a large field of Argo floats has been funded and although the link below doesn't specify the deep dive abilities of the new Argo floats I am sure they will be deployed. We may get a much better picture of the current state of the Southern Oceans  carbon cycle with the new pH sensors that are also part of this study. What is going on with Antarctic Bottom Water formation? A clearer picture is soon to arrive .

   https://scripps.ucsd.edu/news/southern-oceans-role-climate-regulation-ocean-health-goal-21-million-federal-grant

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #294 on: September 12, 2014, 06:40:37 PM »
Bruce,

Thanks for the post about the Argo buoy upgrading, which is good news.

In the area of less good news, the following link leads to an internet article showing how dam construction in the tropics is accelerating current methane production (by drowning tropical forests); while the attached image from Mauna Loa shows that the atmospheric methane concentration is continuing to increase steadily:

http://www.scientificamerican.com/article/drowned-tropical-forests-exacerbate-climate-change/

Best,
ASLR
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #295 on: September 12, 2014, 07:37:17 PM »
The following reference provides paleo evidence that equilibrium climate sensitivity, ECS, is greater during warming periods and lower during glacial climates.  As researchers normally assume that ECS is equal during either warming, or cooling, climate phases, this implies that as we enter a warming period GCM projections are typically non-conservative:

A. S. von der Heydt, P. Köhler, R. S. W. van de Wal and H. A. Dijkstra, (2014), "On the state dependency of fast feedback processes in (palaeo) climate sensitivity", Geophysical Research Letters; DOI: 10.1002/2014GL061121


http://onlinelibrary.wiley.com/doi/10.1002/2014GL061121/abstract


Abstract: "Palaeo data have been frequently used to determine the equilibrium (Charney) climate sensitivity Sa, and — if slow feedback processes (e.g. land ice-albedo) are adequately taken into account — they indicate a similar range as estimates based on instrumental data and climate model results. Many studies assume the (fast) feedback processes to be independent of the background climate state, e.g., equally strong during warm and cold periods. Here we assess the dependency of the fast feedback processes on the background climate state using data of the last 800 kyr and a box-model of the climate system for interpretation. Applying a new method to account for background state dependency, we find Sa = 0.61 ± 0.07 K (W m − 2) − 1 (± 1σ) using the latest LGMtemperature reconstruction and significantly lower climate sensitivity during glacial climates. Due to uncertainties in reconstructing the LGM temperature anomaly, Sa is estimated in the range Sa = 0.54 – 0.95 K (W m − 2) − 1."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #296 on: September 12, 2014, 10:26:16 PM »
The linked reference has a free access pdf, and indicates that the permafrost carbon feedback (PCF), is too low in all of the AR5 RCP scenarios; and that the PCF can increase the RCP 8.5 mean global temperature increase by also 8% by 2100:

Kevin Schaefer, Hugues Lantuit, Vladimir E Romanovsky, Edward A G Schuur and Ronald Witt, (2014), "The impact of the permafrost carbon feedback on global climate", Environ. Res. Lett. 9 085003, doi:10.1088/1748-9326/9/8/085003

http://iopscience.iop.org/1748-9326/9/8/085003

Abstract: "Degrading permafrost can alter ecosystems, damage infrastructure, and release enough carbon dioxide (CO2) and methane (CH4) to influence global climate. The permafrost carbon feedback (PCF) is the amplification of surface warming due to CO2 and CH4 emissions from thawing permafrost. An analysis of available estimates PCF strength and timing indicate 120 ± 85 Gt of carbon emissions from thawing permafrost by 2100. This is equivalent to 5.7 ± 4.0% of total anthropogenic emissions for the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathway (RCP) 8.5 scenario and would increase global temperatures by 0.29 ± 0.21 °C or 7.8 ± 5.7%. For RCP4.5, the scenario closest to the 2 °C warming target for the climate change treaty, the range of cumulative emissions in 2100 from thawing permafrost decreases to between 27 and 100 Gt C with temperature increases between 0.05 and 0.15 °C, but the relative fraction of permafrost to total emissions increases to between 3% and 11%. Any substantial warming results in a committed, long-term carbon release from thawing permafrost with 60% of emissions occurring after 2100, indicating that not accounting for permafrost emissions risks overshooting the 2 °C warming target. Climate projections in the IPCC Fifth Assessment Report (AR5), and any emissions targets based on those projections, do not adequately account for emissions from thawing permafrost and the effects of the PCF on global climate. We recommend the IPCC commission a special assessment focusing on the PCF and its impact on global climate to supplement the AR5 in support of treaty negotiation."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #297 on: September 12, 2014, 10:53:53 PM »
The linked reference indicates that most GCM projections to date have not modelled the sea ice albedo feedback mechanism correctly, and that corrected models will likely project higher rates of global warming:

Moon, W., and J. S. Wettlaufer (2014), "On the nature of the sea ice albedo feedback in simple models", J. Geophys. Res. Oceans, 119, doi:10.1002/2014JC009964.

http://onlinelibrary.wiley.com/doi/10.1002/2014JC009964/abstract

Abstract: "We examine the nature of the ice-albedo feedback in a long-standing approach used in the dynamic-thermodynamic modeling of sea ice. The central issue examined is how the evolution of the ice area is treated when modeling a partial ice cover using a two-category-thickness scheme; thin sea ice and open water in one category and “thick” sea ice in the second. The problem with the scheme is that the area evolution is handled in a manner that violates the basic rules of calculus, which leads to a neglected area evolution term that is equivalent to neglecting a leading-order latent heat flux. We demonstrate the consequences by constructing energy balance models with a fractional ice cover and studying them under the influence of increased radiative forcing. It is shown that the neglected flux is particularly important in a decaying ice cover approaching the transitions to seasonal or ice-free conditions. Clearly, a mishandling of the evolution of the ice area has leading-order effects on the ice-albedo feedback. Accordingly, it may be of considerable importance to reexamine the relevant climate model schemes and to begin the process of converting them to fully resolve the sea ice thickness distribution in a manner such as remapping, which does not in principle suffer from the pathology we describe."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #298 on: September 13, 2014, 09:50:59 AM »
The linked reference, with an open access pdf, investigates increases in the global net downward radiative flux imbalance at the top of Earth's atmosphere (N), between the mean for the 1985-1999 period and the mean for the 2000-2012 period; and present findings that indicate that N has clearly increased at a faster rate than that for the mean global surface temperature; which indicates that between these two period much of the energy imbalance has been going into the ocean (and other heat sinks):


Allan, R. P., C. Liu, N. G. Loeb, M. D. Palmer, M. Roberts, D. Smith, and P.-L. Vidale, (2014), "Changes in global net radiative imbalance 1985–2012", Geophys. Res. Lett., 41, 5588–5597, doi:10.1002/2014GL060962.

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060962/abstract

Abstract: "Combining satellite data, atmospheric reanalyses, and climate model simulations, variability in the net downward radiative flux imbalance at the top of Earth's atmosphere (N) is reconstructed and linked to recent climate change. Over the 1985–1999 period mean N (0.34 ± 0.67 Wm−2) is lower than for the 2000–2012 period (0.62 ± 0.43 Wm−2, uncertainties at 90% confidence level) despite the slower rate of surface temperature rise since 2000. While the precise magnitude of N remains uncertain, the reconstruction captures interannual variability which is dominated by the eruption of Mount Pinatubo in 1991 and the El Niño Southern Oscillation. Monthly deseasonalized interannual variability in N generated by an ensemble of nine climate model simulations using prescribed sea surface temperature and radiative forcings and from the satellite-based reconstruction is significantly correlated (r∼0.6) over the 1985–2012 period."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #299 on: September 13, 2014, 05:33:41 PM »
The linked reference clearly (0.97 correlation) links increasing GHGs with a (El Nino-like) warming of the Equatorial Pacific.  If this is true then one would expect the PDO/IPO to become more positive, which would likely increase the mean SST in the Northern Pacific; which would likely increase Arctic amplification:

Xiaoliang Song and Guang J. Zhang, (2014), "Role of Climate Feedback in El Niño-like SST Response to Global Warming", Journal of Climate; doi: http://dx.doi.org/10.1175/JCLI-D-14-00072.1


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00072.1


Abstract: "Under global warming from the doubling of CO2, the equatorial Pacific experiences an El Nino-like warming, as simulated by most global climate models. A new climate feedback and response analysis method (CFRAM) is applied to 10 years of hourly output of the slab ocean model version of the NCAR CCSM3.0 (CCSM3-SOM) to determine the processes responsible for this warming. Unlike the traditional surface heat budget analysis, the CFRAM can explicitly quantify the contributions of each radiative climate feedback, physical and dynamical process of GCM to temperature changes. The mean bias in the sum of partial SST changes due to each feedback derived with CFRAM in the tropical Pacific is negligible (0.5%) compared to the mean SST change from the CCSM3.0-SOM simulations, with spatial pattern correlation of 0.97 between the two. The analysis shows that the factors contributing to the El Nino-like SST warming in the central Pacific are different from that in the eastern Pacific. In the central Pacific, the largest contributor to El Nino-like SST warming is dynamical advection, followed by PBL diffusion, water vapor feedback, and surface evaporation. In contrast, in the eastern Pacific the dominant contributor to El Nino-like SST warming is cloud feedback, with water vapor feedback further amplifying the warming."
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