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Author Topic: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS  (Read 202455 times)

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #350 on: November 16, 2014, 09:54:37 AM »
In the following free access reference Hansen et al (2013) indicates that: (a) the fast-feedback climate sensitivity is at the high end of the 3 +/- 1 C range; and (b) that ice sheet response time to radiative forcing is faster than earlier researchers thought and consequently that the Antarctic hysteresis was less than previously expected:

Hansen J, Sato M, Russell G, Kharecha P.,  (2013), "Climate sensitivity, sea level and atmospheric carbon dioxide", Phil Trans R Soc A 371: 20120294, http://dx.doi.org/10.1098/rsta.2012.0294

http://rsta.royalsocietypublishing.org/content/371/2001/20120294.full

Abstract: "Cenozoic temperature, sea level and CO2 covariations provide insights into climate sensitivity to external forcings and sea-level sensitivity to climate change.  Climate sensitivity depends on the initial climate state, but potentially can be accurately inferred from precise palaeo-climate data. Pleistocene climate oscillations yield a fast-feedback climate sensitivity of 3 ± 1◦C for a 4Wm−2 CO2 forcing if Holocene warming relative to the Last Glacial Maximum (LGM) is used as calibration, but the error (uncertainty) is substantial and partly subjective because of poorly defined LGM global temperature and possible human influences in the Holocene. Glacial-to-interglacial climate change leading to the prior (Eemian) interglacial is less ambiguous and implies a sensitivity in the upper part of the above range, i.e. 3–4◦C for a 4Wm−2 CO2 forcing. Slow feedbacks, especially change of ice sheet size and atmospheric CO2, amplify the total Earth system sensitivity by an amount that depends on the time scale considered.  Ice sheet response time is poorly defined, but we show that the slow response and hysteresis in prevailing ice sheet models are exaggerated. We use a global model, simplified to essential processes, to investigate state dependence of climate sensitivity, finding an increased sensitivity towards warmer climates, as low cloud cover is diminished and increased water vapour elevates the tropopause. Burning all fossil fuels, we conclude, would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #351 on: November 16, 2014, 06:50:38 PM »
With a hat tip to Bruce Steele in the Science folder, the linked reference presents findings about a previously unknown positive feedback factor, where increasing ocean acidification (due to anthropogenic CO₂ emissions) is promoting biogenic activity in the sea-surface microlayer (SML) that can change oceanic-atmospheric processes like gas exchange and emissions of marine primary organic aerosols (POA), and note that some POA's have a negative feedback so a change in the SML that limits the emissions of such POA's would result in a positive feedback mechanism.

Galgani, L., Stolle. C., Endres, S., Schulz, K. G., Engel, A. (2014), Effects of ocean acidification on the biogenic composition of the seasurface microlayer: Results from a mesocosm study, J. Geophys. Res. Oceans, 119, doi: 10.1002/2014JC010188.

http://onlinelibrary.wiley.com/doi/10.1002/2014JC010188/abstract

Abstract: "The sea-surface microlayer (SML) is the ocean's uppermost boundary to the atmosphere and in control of climate relevant processes like gas exchange and emission of marine primary organic aerosols (POA). The SML represents a complex surface film including organic components like polysaccharides, proteins, and marine gel particles, and harbors diverse microbial communities. Despite the potential relevance of the SML in ocean-atmosphere interactions still little is known about its structural characteristics and sensitivity to a changing environment such as increased oceanic uptake of anthropogenic CO2. Here, we report results of a large scale mesocosm study, indicating that ocean acidification can affect the abundance and activity of microorganisms during phytoplankton blooms, resulting in changes in composition and dynamics of organic matter in the SML. Our results reveal a potential coupling between anthropogenic CO2 emissions and the biogenic properties of the SML, pointing to a hitherto disregarded feedback process between ocean and atmosphere under climate change."

See also:

http://www.geomar.de/index.php?id=4&no_cache=1&tx_ttnews%5Btt_news%5D=2158&tx_ttnews%5BbackPid%5D=185&L=1

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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #352 on: November 17, 2014, 08:02:18 PM »
The following linked Science Codex article indicates that more accurate modeling of the influence of rising global temperatures on soil microbes in Earth System Models may indicate lower carbon emissions than previously estimated (see extract):

http://www.sciencecodex.com/as_temperatures_rise_soil_will_relinquish_less_carbon_to_the_atmosphere_than_predicted-145738

Extract: "Tang and Riley recommend more research be conducted on these microbial and mineral interactions. They also recommend that these features ultimately be included in next-generation Earth system models, such as the Department of Energy's Accelerated Climate Modeling for Energy, or ACME."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #353 on: November 21, 2014, 05:08:42 PM »
The linked article indicates that decomposing crops could be responsible for one-fourth of the post-summer increase in atmospheric carbon dioxide levels.  Therefore, as global warming is temporarily stimulating crop (and vegetation) growth, it is also stimulating CO₂ emissions from decomposing crops (and vegetation), which is observed in the Keeling CO₂ curves:


Josh M. Gray, Steve Frolking, Eric A. Kort, Deepak K. Ray, Christopher J. Kucharik, Navin Ramankutty & Mark A. Friedl, (2014), "Direct human influence on atmospheric CO2 seasonality from increased cropland productivity", Nature, Volume: 515, Pages: 398–401, doi:10.1038/nature13957

http://www.nature.com/nature/journal/v515/n7527/full/nature13957.html

Abstract: "Ground- and aircraft-based measurements show that the seasonal amplitude of Northern Hemisphere atmospheric carbon dioxide (CO2) concentrations has increased by as much as 50 per cent over the past 50 years. This increase has been linked to changes in temperate, boreal and arctic ecosystem properties and processes such as enhanced photosynthesis, increased heterotrophic respiration, and expansion of woody vegetation. However, the precise causal mechanisms behind the observed changes in atmospheric CO2 seasonality remain unclear. Here we use production statistics and a carbon accounting model to show that increases in agricultural productivity, which have been largely overlooked in previous investigations, explain as much as a quarter of the observed changes in atmospheric CO2 seasonality. Specifically, Northern Hemisphere extratropical maize, wheat, rice, and soybean production grew by 240 per cent between 1961 and 2008, thereby increasing the amount of net carbon uptake by croplands during the Northern Hemisphere growing season by 0.33 petagrams. Maize alone accounts for two-thirds of this change, owing mostly to agricultural intensification within concentrated production zones in the midwestern United States and northern China. Maize, wheat, rice, and soybeans account for about 68 per cent of extratropical dry biomass production, so it is likely that the total impact of increased agricultural production exceeds the amount quantified here."
“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 #354 on: November 23, 2014, 03:47:16 PM »
The linked reference suggests that permafrost thawing is a possible source of the both the abrupt carbon release and the associated abrupt increase in mean global temperature at the onset of the Bolling/Allerod, and that a similar occurrence could happen with continued global warming:

Peter Köhler, Gregor Knorr and Edouard Bard, (2014), "Permafrost thawing as a possible source of abrupt carbon release at the onset of the Bølling/Allerød", Nature Communications 5:5520; DOI: 10.1038/ncomms6520

http://www.nature.com/ncomms/2014/141120/ncomms6520/full/ncomms6520.html

Abstract: "One of the most abrupt and yet unexplained past rises in atmospheric CO2 (>10 p.p.m.v. in two centuries) occurred in quasi-synchrony with abrupt northern hemispheric warming into the Bølling/Allerød, ~14,600 years ago. Here we use a U/Th-dated record of atmospheric Δ14C from Tahiti corals to provide an independent and precise age control for this CO2 rise. We also use model simulations to show that the release of old (nearly 14C-free) carbon can explain these changes in CO2 and Δ14C. The Δ14C record provides an independent constraint on the amount of carbon released (~125 Pg C). We suggest, in line with observations of atmospheric CH4 and terrigenous biomarkers, that thawing permafrost in high northern latitudes could have been the source of carbon, possibly with contribution from flooding of the Siberian continental shelf during meltwater pulse 1A. Our findings highlight the potential of the permafrost carbon reservoir to modulate abrupt climate changes via greenhouse-gas feedbacks."

See also:
http://www.reportingclimatescience.com/news-stories/article/did-permafrost-melt-cause-abrupt-ice-age-co2-rise.html
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #355 on: December 27, 2014, 10:17:38 AM »
At the minimum the linked reference indicates that "priming" from microbe-driven decomposition of organics will partially offset "protection" from global warming due to storage of organic carbon into the soil (see the attached image and the associated caption from the linked Princeton University website below).

Benjamin N. Sulman, Richard P. Phillips, A. Christopher Oishi, Elena Shevliakova, and Stephen W. Pacala, (2014), "Microbe-driven turnover offsets mineral-mediated storage of soil carbon under elevated CO₂", Nature Climate Change, DOI: 10.1038/nclimate2436

http://www.nature.com/nclimate/journal/v4/n12/full/nclimate2436.html

Abstract: "The sensitivity of soil organic carbon (SOC) to changing environmental conditions represents a critical uncertainty in coupled carbon cycle–climate models. Much of this uncertainty arises from our limited understanding of the extent to which root–microbe interactions induce SOC losses (through accelerated decomposition or ‘priming) or indirectly promote SOC gains (via ‘protection’ through interactions with mineral particles). We developed a new SOC model to examine priming and protection responses to rising atmospheric CO2. The model captured disparate SOC responses at two temperate free-air CO2 enrichment (FACE) experiments. We show that stabilization of ‘new’ carbon in protected SOC pools may equal or exceed microbial priming of ‘old’ SOC in ecosystems with readily decomposable litter and high clay content (for example, Oak Ridge5). In contrast, carbon losses induced through priming dominate the net SOC response in ecosystems with more resistant litters and lower clay content (for example, Duke). The SOC model was fully integrated into a global terrestrial carbon cycle model to run global simulations of elevated CO2 effects. Although protected carbon provides an important constraint on priming effects, priming nonetheless reduced SOC storage in the majority of terrestrial areas, partially counterbalancing SOC gains from enhanced ecosystem productivity."

See also:

http://blogs.princeton.edu/research/2014/12/22/dirty-pool-soils-large-carbon-stores-could-be-freed-by-increased-co2-plant-growth-nature-climate-change/

Caption: "Researchers based at Princeton University report that an increase in human-made carbon dioxide in the atmosphere could initiate a chain reaction between plants and microorganisms that would unsettle one of the largest carbon reservoirs on the planet — soil. The researchers developed the first computer model to show at a global scale the complex interaction between carbon, plants and soil. The model projected changes (above) in global soil carbon as a result of root-soil interactions, with blue indicating a greater loss of soil carbon to the atmosphere. (Image by Benjamin Sulman, Princeton Environmental Institute).
“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 #356 on: December 27, 2014, 10:49:07 AM »
The following two linked articles indicate the importance of ecosystem changes as positive feedback mechanisms.  The first link discusses the role of the artic ground squirrels in accelerating permafrost loss; while the second linked article discusses how the recovery of beavers (from near extinction) is accelerating methane emissions from the ponds that the beavers form:

Nigel Golden, Susan Natali and Nikita Zimov, (2014), "Consequences of artic ground squirrels on soil carbon loss from Siberian tundra", Fall AGU Conference

https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/20090

Abstract: "A large pool of organic carbon (C) has been accumulating in the Arctic for thousands of years. Much of this C has been frozen in permafrost and unavailable for microbial decomposition. As the climate warms and permafrost thaws, the fate of this large C pool will be driven not only by climatic conditions, but also by ecosystem changes brought about by arctic animal populations. In this project we studied arctic ground squirrels (Spermophilus parryii), which are widely-distributed throughout the Arctic. These social mammals create subterranean burrows that mix soil layers, increase aeration, alter soil moisture and temperature, and redistribute soil nutrients, all of which may impact microbial decomposition. We examined the effects of arctic ground squirrel activity on soil C mineralization in dry heath tundra underlain by continuous permafrost in the Kolyma River watershed in northeast Siberia, Russia. Vegetation cover was greatly reduced on the ground squirrel burrows (80% of ground un-vegetated), compared to undisturbed sites (35% of ground un-vegetated). Soils from ground squirrel burrows were also significantly dryer and warmer. To examine effects of ground squirrel activity on microbial respiration, we conducted an 8-day incubation of soil fromburrows and from adjacent undisturbed tundra. In addition, we assessed the impact of nutrient addition by including treatments with low and high levels of nitrogen addition. Microbial respiration (per gram soil) was three-fold higher in incubated soils from the undisturbed sites compared to soils collected from the burrows. The lower rates of respiration from the disturbed soils may have been a result of lower carbon quality or low soil moisture. High nitrogen addition significantly increased respiration in the undisturbed soils, but not in the disturbed burrow soils, which suggests that microbial respiration in the burrow soils was not primarily limited by nitrogen. These results demonstrate the importance of wildlife activity on soil C vulnerability in the Arctic. As C is moved from protected permafrost pools to thawed soils, burrowing animals, such as the arctic ground squirrel, may play an increasingly important role in regulating the transfer of C from soils to the atmosphere."


Colin J. Whitfield, Helen M. Baulch, Kwok P. Chun, Cherie J. Westbrook, (2014), "Beaver-mediated methane emission: The effects of population growth in Eurasia and the Americas," AMBIO, DOI 10.1007/s13280-014-0575-y

http://link.springer.com/article/10.1007%2Fs13280-014-0575-y

For free pdf:

http://download.springer.com/static/pdf/318/art%253A10.1007%252Fs13280-014-0575-y.pdf?auth66=1419673355_e93e914f89a314746aa7f58aa8e2a709&ext=.pdf

Abstract: "Globally, greenhouse gas budgets are dominated by natural sources, and aquatic ecosystems are a prominent source of methane (CH4) to the atmosphere. Beaver (Castor canadensis and Castor fiber) populations have experienced human-driven change, and CH4 emissions associated with their habitat remain uncertain. This study reports the effect of near extinction and recovery of beavers globally on aquatic CH4 emissions and habitat. Resurgence of native beaver populations and their introduction in other regions accounts for emission of 0.18–0.80 Tg CH4 year−1 (year 2000). This flux is approximately 200 times larger than emissions from the same systems (ponds and flowing waters that became ponds) circa 1900. Beaver population recovery was estimated to have led to the creation of 9500–42 000 km2 of ponded water, and increased riparian interface length of >200 000 km. Continued range expansion and population growth in South America and Europe could further increase CH4 emissions."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

wili

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #357 on: December 27, 2014, 05:18:43 PM »
Thanks for this, ASLR.

These are the sorts of potential or already observed biological factors that, as far as I've seen, people like Archer and Schmit are not figuring in when they say assuredly that the permafrost cap over sea bed methane hydrates can only very slowly be thawed. All sorts of creatures new to that part of the world's oceans are moving in to the ESAS, and many more are likely to move there in the near future. Counting on behavior in previous epochs does not necessarily help much here, since new species have presumably evolved since those times that could have different behaviors.
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #358 on: December 27, 2014, 07:34:04 PM »
wili,
Thanks for pointing out the positive feedback risks from marine life moving into the Arctic Ocean as it is projected to warm rapidly in the coming decades.  The following lengthy National Geographic article discusses numerous other ecosystems positive feedback risks (that are not yet fully considered in ESM projections) including those from: (a) invasive insects moving into the boreal area (see the page 4 link and associated quote); (b) heat/water stress on plants/trees that cannot spread as fast as the changing climate; (c) wildfires in the boreal areas that will spread black carbon around the Arctic; etc.:

http://environment.nationalgeographic.com/environment/global-warming/missing-carbon/#page=1

http://environment.nationalgeographic.com/environment/global-warming/missing-carbon/#page=4

Quote: "Right now global warming, ironically, may be helping forestall even more warming, by speeding the growth of carbon-absorbing trees. But balanced against that are warning signs—hints that northern ecosystems could soon turn against us. Eventually, warming in the far north may have what scientists call a positive feedback effect, in which warming triggers new floods of carbon dioxide in the atmosphere, driving temperatures higher.
Worrisome signs begin on the aircraft approach to Anchorage. As the route skirts the hundred-mile-wide (161-kilometer-wide) Kenai Peninsula, ugly gray gaps appear in the dark green canopy of spruce below. Since the early 1990s bark beetles have been on the rampage in the Kenai, killing spruce on more than 2-million acres (809,000 hectares) there. Farther south in the Kenai, says Glenn Juday, a forest ecologist at the University of Alaska, skeletal trees stretch from horizon to horizon. "It's the largest single area of trees killed by insects in North America," says Juday. "No outbreak this size has happened in the past 250 years."
The vast tracts of dead trees will ultimately send their carbon back to the atmosphere when decay or fire consumes them. A warming climate is likely to blame, Juday and others believe. Warmth favors the beetle by speeding up its life cycle and improving its chance of surviving the winter. And as Juday has found in his study area, warming also stresses the hardy northern trees, making them less able to fight off infestation.
…."

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

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #359 on: December 31, 2014, 01:22:58 AM »
The linked reference (with an open access pdf) indicates: " … substantial positive forcings from the direct modifications and agriculture sectors, particularly from India, China, and southeast Asia … ".  The authors take this finding as a cause for optimism that now that the source of this positive forcing has been identified that policy can be developed to counter act this forcing; unless the bureaucrats in this areas are slow to take action or if demand for more food prevents them from taking action. 

Ward, D. S. and Mahowald, N. M. , (2014), "Local sources of global climate forcing from different categories of land use activities", Earth Syst. Dynam. Discuss., 5, 1751-1792, doi:10.5194/esdd-5-1751-2014.

http://www.earth-syst-dynam-discuss.net/5/1751/2014/esdd-5-1751-2014.html

Abstract. "Identifying and quantifying the sources of climate impacts from land use and land cover change (LULCC) is necessary to optimize policies regarding LULCC for climate change mitigation. These climate impacts are typically defined relative to emissions of CO2, or sometimes emissions of other long-lived greenhouse gases. Here we use previously published estimates of the radiative forcing (RF) of LULCC that include the short-lived forcing agents O3 and aerosols, in addition to long-lived greenhouse gases and land albedo change, for six projections of LULCC as a metric for quantifying climate impacts. The LULCC RF is attributed to three categories of LULCC activities: direct modifications to land cover, agriculture, and wildfire response, and sources of the forcing are ascribed to individual grid points for each sector. Results for the year 2010 show substantial positive forcings from the direct modifications and agriculture sectors, particularly from India, China, and southeast Asia, and a smaller magnitude negative forcing response from wildfires. The RF from direct modifications, mainly deforestation activities, exhibits a large range in future outcomes for the standard future scenarios implying that these activities, and not agricultural emissions (which lead to more consistent RFs between scenarios), will drive the LULCC RF in the future. We show that future forest area change can be used as a predictor of the future RF from direct modification activities, especially in the tropics, suggesting that deforestation-prevention policies that value land based on its C-content may be particularly effective at mitigating climate forcing originating in the tropics from this sector. Although, the response of wildfire RF to tropical land cover changes is not as easily scalable and yet imposes a non-trivial feedback onto the total LULCC RF."
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #360 on: January 01, 2015, 07:22:38 PM »
The linked Jamstec press release from Oct 2014 indicates that changes in the depth of snow cover in the pan-Arctic region is 50% more effective at influence changes in the permafrost soil temperatures than are changes in the air temperature.  Therefore, as shrub growth in the tundra accelerates (due to global warming) the snow will increasingly be retained by the shrub over which will prevent the snow from reaching the ground to insulate the permafrost.  Such feedback mechanisms can accelerate permafrost degradation faster than current GCMs project:

http://www.jamstec.go.jp/e/about/press_release/20141020/
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AbruptSLR

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #361 on: January 05, 2015, 09:11:48 AM »
The linked reference indicates that the longer growing season in the Arctic (largely due to polar amplification) is resulting in a greater abundance of deciduous shrubs in the tundra (as observed by satellites); which according to their models is increasing net carbon dioxide uptake.  However, while it may well be true that this deciduous shrub growth is serving as a temporary carbon dioxide sink, it is most likely only absorbing the extra carbon dioxide being emitted by the degradation of the permafrost, leaving the associated methane emissions in the atmosphere.  Furthermore, the change in albedo associated with the shrub growth is accelerating the permafrost degradation faster than the shrubs are serving as a carbon sink; which in a few decades will result in a net positive feedback mechanism.

Shannan K. Sweet, Kevin L. Griffin, Heidi Steltzer, Laura Gough and Natalie T. Boelman, (2014), "Greater deciduous shrub abundance extends tundra peak season and increases modeled net CO2 uptake", Global Change Biology, DOI: 10.1111/gcb.12852


http://onlinelibrary.wiley.com/doi/10.1111/gcb.12852/abstract

Abstract: "Satellite studies of the terrestrial Arctic report increased summer greening and longer overall growing and peak seasons since the 1980s, which increases productivity and the period of carbon uptake. These trends are attributed to increasing air temperatures and reduced snow cover duration in spring and fall. Concurrently, deciduous shrubs are becoming increasingly abundant in tundra landscapes, which may also impact canopy phenology and productivity. Our aim was to determine the influence of greater deciduous shrub abundance on tundra canopy phenology and subsequent impacts on net ecosystem carbon exchange (NEE) during the growing and peak seasons in the arctic foothills region of Alaska. We compared deciduous shrub-dominated and evergreen/graminoid-dominated community-level canopy phenology throughout the growing season using the normalized difference vegetation index (NDVI). We used a tundra plant-community specific leaf area index (LAI) model to estimate LAI throughout the green season, and a tundra specific NEE model to estimate the impact of greater deciduous shrub abundance and associated shifts in both leaf area and canopy phenology on tundra carbon flux. We found that deciduous shrub canopies reached the onset of peak greenness 13 days earlier and the onset of senescence 3 days earlier compared to evergreen/graminoid canopies, resulting in a 10-day extension of the peak season. The combined effect of the longer peak season and greater leaf area of deciduous shrub canopies almost tripled the modeled net carbon uptake of deciduous shrub communities compared to evergreen/graminoid communities, while the longer peak season alone resulted in 84% greater carbon uptake in deciduous shrub communities. These results suggest that greater deciduous shrub abundance increases carbon uptake not only due to greater leaf area, but also due to an extension of the period of peak greenness, which extends the period of maximum carbon uptake."
“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 #362 on: January 07, 2015, 10:31:29 AM »
The linked article indicates that the higher than previously assumed absorption of carbon dioxide by the tropical rain forest has been masking the full extent of current radiative forcing/climate sensitivity; which is disturbing given the sensitivity of the tropical rainforest to degradation from both El Nino events and from deforestation (with a growing indigenous population in such areas):

David Schimel, Britton B. Stephens, and Joshua B. Fisher, (2014), "Effect of increasing CO2 on the terrestrial carbon cycle", PNAS, doi: 10.1073/pnas.1407302112

http://www.pnas.org/content/early/2014/12/25/1407302112.abstract?sid=93b960e2-60a2-43bb-b2db-8e8f4c4a347b

Abstract: "Feedbacks from the terrestrial carbon cycle significantly affect future climate change. The CO2 concentration dependence of global terrestrial carbon storage is one of the largest and most uncertain feedbacks. Theory predicts the CO2 effect should have a tropical maximum, but a large terrestrial sink has been contradicted by analyses of atmospheric CO2 that do not show large tropical uptake. Our results, however, show significant tropical uptake and, combining tropical and extratropical fluxes, suggest that up to 60% of the present-day terrestrial sink is caused by increasing atmospheric CO2. This conclusion is consistent with a validated subset of atmospheric analyses, but uncertainty remains. Improved model diagnostics and new space-based observations can reduce the uncertainty of tropical and temperate zone carbon flux estimates. This analysis supports a significant feedback to future atmospheric CO2 concentrations from carbon uptake in terrestrial ecosystems caused by rising atmospheric CO2 concentrations. This feedback will have substantial tropical contributions, but the magnitude of future carbon uptake by tropical forests also depends on how they respond to climate change and requires their protection from deforestation."

Significance: "Feedbacks from terrestrial ecosystems to atmospheric CO2 concentrations contribute the second-largest uncertainty to projections of future climate. These feedbacks, acting over huge regions and long periods of time, are extraordinarily difficult to observe and quantify directly. We evaluated in situ, atmospheric, and simulation estimates of the effect of CO2 on carbon storage, subject to mass balance constraints. Multiple lines of evidence suggest significant tropical uptake for CO2, approximately balancing net deforestation and confirming a substantial negative global feedback to atmospheric CO2 and climate. This reconciles two approaches that have previously produced contradictory results. We provide a consistent explanation of the impacts of CO2 on terrestrial carbon across the 12 orders of magnitude between plant stomata and the global carbon cycle."
“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 #363 on: January 10, 2015, 07:35:25 PM »
The linked reference characterizes the unprecedented scale of the recent and projected growth of the global middle-class.  The first attached image shows that a lot of the growth of the middle class though 2030 is projected to occur in South, and East, Asia.  The implications of the carbon foot print of this trend almost guarantees that the world will follow a radiative forcing pathway greater than RCP 8.5 25% CL.

Clara Brandi & Max Büge, (2014), "A cartography of the new middle classes in developing and emerging countries", Discussion Paper / Deutsches Institut für Entwicklungspolitik, ISSN 1860-0441.

http://www.die-gdi.de/uploads/media/DP_35.2014.pdf

Abstract: "The world is experiencing a structural change on an unprecedented scale: it is becoming less poor and more middle-class. The growth of emerging middle classes has profound implications for global development. Yet, although the emergence of middle classes across the globe and its potential effects are set high on the agendas of researchers and policy-makers, an often neglected fact is that middle-class characteristics vary greatly from one country to another. Upon closer look, there is not one new global middle class but a variety of very different burgeoning middle classes. This paper aims to highlight the differences in middle-class growth, size and consumption capacities in developing and emerging economies. To take account of this heterogeneousness, the paper presents a novel middle-class typology that includes nine different “types” of middle classes, ranging from small and affluent middle classes to large middle classes with low spending capacity.  The typology allows for comparing different middle classes across countries and is a useful tool for more fine-grained research and policy analysis. Against that background, the paper points to fruitful avenues for future research with regards to interpreting the role of the rising middle classes in the context of economic growth, democracy and civic values as well as environmental challenges."

To put this risk into prospective, if the effective climate sensitivity by 2100 is close to 6 C, and the mean global surface temperature increase by 2100 is about 9 C; then the second attached image indicates that one would need to go back over 40-million years to the Eocene before one would encounter such extreme conditions (which of course would not be in equilibrium by 2100, under such a likely scenario).
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #364 on: January 11, 2015, 06:11:54 PM »
While the timescale of the ocean's burial-nutrient feedbacks are on the order of thousands of years, the surprisingly high sensitivity of this positive feedback mechanism(s) means that future generations will clearly pay a price for our current foolishness:

R. Roth, S. P. Ritz, and F. Joos, (2014), "Burial-nutrient feedbacks amplify the sensitivity of atmospheric carbon dioxide to changes in organic matter remineralisation", Earth Syst. Dynam., 5, 321–343, www.earth-syst-dynam.net/5/321/2014/, doi:10.5194/esd-5-321-2014

http://www.earth-syst-dynam.net/5/321/2014/esd-5-321-2014.pdf


Abstract. "Changes in the marine remineralisation of particulate organic matter (POM) and calcium carbonate potentially provide a positive feedback with atmospheric CO2 and climate change. The responses to changes in remineralisation length scales are systematically mapped with the Bern3D ocean–sediment model for atmospheric CO2 and tracer fields for which observations and palaeoproxies exist. Results show that the “sediment burial-nutrient feedback” amplifies the response in atmospheric CO2 by a factor of four to seven. A transient imbalance between the weathering flux and the burial of organic matter and calcium carbonate lead to sustained changes in the ocean’s phosphate and alkalinity inventory and in turn in surface nutrient availability, marine productivity, and atmospheric CO2. It takes decades to centuries to reorganise tracers and fluxes within the ocean, many millennia to approach equilibrium for burial fluxes, while delta13C signatures are still changing 200 000 years after the perturbation. At 1.7 ppmm−1, atmospheric CO2 sensitivity is about fifty times larger for a unit change in the remineralisation depth of POM than of calcium carbonate. The results highlight the role of organic matter burial in atmospheric CO2 and the substantial impacts of seemingly small changes in POM remineralisation."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #365 on: January 14, 2015, 01:19:44 AM »
The linked reference clarifies the contribution of volcanic eruptions amid other factors that contributed to the recent faux "warming hiatus":

Benjamin D. Santer, Susan Solomon, Céline Bonfils, Mark D. Zelinka, Jeffrey F. Painter, Francisco Beltran, John C. Fyfe, Gardar Johannesson, Carl Mears, David A. Ridley, Jean-Paul Vernier and Frank J. Wentz, (2015), "Observed multi-variable signals of late 20th and early 21st century volcanic activity", Geophysical Research Letters, DOI: 10.1002/2014GL062366

http://onlinelibrary.wiley.com/doi/10.1002/2014GL062366/abstract

Abstract: "The relatively muted warming of the surface and lower troposphere since 1998 has attracted considerable attention. One contributory factor to this “warming hiatus" is an increase in volcanically-induced cooling over the early 21st century. Here, we identify the signals of late 20th and early 21st century volcanic activity in multiple observed climate variables. Volcanic signals are statistically discernible in spatial averages of tropical and near-global SST, tropospheric temperature, net clear-sky short-wave radiation, and atmospheric water vapor. Signals of late 20th and early 21st century volcanic eruptions are also detectable in near-global averages of rainfall. In tropical-average rainfall, however, only a Pinatubo-caused drying signal is identifiable. Successful volcanic signal detection is critically dependent on removal of variability induced by the El Niño/Southern Oscillation (ENSO)."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #366 on: January 14, 2015, 01:28:26 AM »
The linked reference discusses the potential carbon emission contributions from future peatland fires:

Merritt R. Turetsky, Brian Benscoter, Susan Page, Guillermo Rein, Guido R. van der Werf & Adam Watts, (2015), "Global vulnerability of peatlands to fire and carbon loss", Nature Geoscience, Volume: 8, Pages: 11–14, doi:10.1038/ngeo2325

http://www.nature.com/ngeo/journal/v8/n1/full/ngeo2325.html

Abstract: "Globally, the amount of carbon stored in peats exceeds that stored in vegetation and is similar in size to the current atmospheric carbon pool. Fire is a threat to many peat-rich biomes and has the potential to disturb these carbon stocks. Peat fires are dominated by smouldering combustion, which is ignited more readily than flaming combustion and can persist in wet conditions. In undisturbed peatlands, most of the peat carbon stock typically is protected from smouldering, and resistance to fire has led to a build-up of peat carbon storage in boreal and tropical regions over long timescales. But drying as a result of climate change and human activity lowers the water table in peatlands and increases the frequency and extent of peat fires. The combustion of deep peat affects older soil carbon that has not been part of the active carbon cycle for centuries to millennia, and thus will dictate the importance of peat fire emissions to the carbon cycle and feedbacks to the climate."

See also:
http://www.nature.com/articles/ngeo2325.epdf?referrer_access_token=qwqHzdwsLbdMYyiamHU-CdRgN0jAjWel9jnR3ZoTv0NhED8L6FSpdKd-X4E9LaMC7WiLOszsE3S88VKZwEe0YCQkPcw2TwWpCl8RmXhdqAE%3D

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #367 on: January 15, 2015, 06:47:57 PM »
The linked (open access) reference (and attached image) indicate that the influence of CO₂ will limit some of the possible increases in terrestrial evapotranspiration, ET, that would otherwise be associated with global warming.  Nevertheless, the Arctic region is projected to have the largest increase in ET by 2100; which will contribute to Arctic Amplification (particularly under SRES A2 or other scenarios with stronger radiative forcing pathways):

Shufen Pan, Hanqin Tian, Shree R.S. Dangal, Qichun Yang, Jia Yang, Chaoqun Lu, Bo Tao, Wei Ren & Zhiyun Ouyang, (2015), "Responses of global terrestrial evapotranspiration to climate change and increasing atmospheric CO2 in the 21st century", Earth's Future, DOI: 10.1002/2014EF000263

http://onlinelibrary.wiley.com/enhanced/doi/10.1002/2014EF000263/

Abstract: "Quantifying the spatial and temporal patterns of the water lost to the atmosphere through land surface evapotranspiration (ET) is essential for understanding the global hydrological cycle, but remains much uncertain. In this study, we use the Dynamic Land Ecosystem Model to estimate the global terrestrial ET during 2000–2009 and project its changes in response to climate change and increasing atmospheric CO2 under two IPCC SRES scenarios (A2 and B1) during 2010–2099. Modeled results show a mean annual global terrestrial ET of about 549 (545–552) mm yr−1 during 2000–2009. Relative to the 2000s, global terrestrial ET for the 2090s would increase by 30.7 mm yr−1 (5.6%) and 13.2 mm yr−1 (2.4%) under the A2 and B1 scenarios, respectively. About 60% of global land area would experience increasing ET at rates of over 9.5 mm decade−1 over the study period under the A2 scenario. The Arctic region would have the largest ET increase (16% compared with the 2000s level) due to larger increase in temperature than other regions. Decreased ET would mainly take place in regions like central and western Asia, northern Africa, Australia, eastern South America, and Greenland due to declines in soil moisture and changing rainfall patterns. Our results indicate that warming temperature and increasing precipitation would result in large increase in ET by the end of the 21st century, while increasing atmospheric CO2 would be responsible for decrease in ET, given the reduction of stomatal conductance under elevated CO2."

Caption: "Temporal pattern of change in terrestrial ET: Global (a), low latitude (b), mid-latitude (c) and high latitude (d) as a function of climate and increasing atmospheric CO2 under A2 and B1 scenarios."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #368 on: January 16, 2015, 12:44:17 AM »
The following two linked references indicate that measurement show that North America snow has a much lower albedo than previously expected, meaning that the identified trend will serve as a positive feedback mechanism for global warming:

Doherty, S. J., C. Dang, D. A. Hegg, R. Zhang, and S. G. Warren (2014), Black carbon and other light-absorbing particles in snow of central North America, J. Geophys. Res. Atmos., 119, 12,807–12,831, doi:10.1002/2014JD022350.

http://onlinelibrary.wiley.com/doi/10.1002/2014JD022350/abstract

Abstract: "Vertical profiles of light-absorbing particles in seasonal snow were sampled from 67 North American sites. Over 500 snow samples and 55 soil samples from these sites were optically analyzed for spectrally resolved visible light absorption. The optical measurements were used to estimate black carbon (BC) mixing ratios in snow ( ), contributions to absorption by BC and non-BC particles, and the absorption Ångström exponent of particles in snow and local soil. Sites in Canada tended to have the lowest BC mixing ratios (typically ~5–35 ng g−1), with somewhat higher  in the Pacific Northwest (typically ~5–40 ng g−1) and Intramountain Northwest (typically 10–50 ng g−1). The Northern U.S. Plains sites were the dirtiest, with  typically ~15–70 ng g−1 and multiple sample layers with >100 ng g−1 BC in snow. Snow water samples were also chemically analyzed for standard anions, selected carbohydrates, and various elements. The chemical and optical data were input to a Positive Matrix Factorization analysis of the sources of particulate light absorption. These were soil, biomass/biofuel burning, and fossil fuel pollution. Comparable analyses have been conducted for the Arctic and North China, providing a broad, internally consistent data set. As in North China, soil is a significant contributor to snow particulate light absorption in the Great Plains. We also examine the concentrations and sources of snow particulate light absorption across a latitudinal transect from the northern U.S. Great Plains to Arctic Canada by combining the current data with our earlier Arctic survey."


Dang, C., and D. A. Hegg (2014), Quantifying light absorption by organic carbon in Western North American snow by serial chemical extractions, J. Geophys. Res. Atmos., 119, 10,247–10,261, doi:10.1002/2014JD022156.

http://onlinelibrary.wiley.com/doi/10.1002/2014JD022156/abstract


Abstract: "Light-absorbing particulates (LAPs) in snow, namely black carbon (BC), organic carbon (OC), and iron oxides, can reduce snow albedo and influence regional and global climate. Partitioning light absorption by LAPs to BC and non-BC (i.e., OC and iron oxides) is important yet difficult due to both technical limitations and the complicated nature of LAPs. In this work, we applied serial chemical extractions on LAP samples acquired from snow samples in western North America to study the light absorption by different types of OC. We also estimated the light absorption due to iron oxides. Based on these chemical analyses, we then compared our estimation of the non-BC light absorption with that from an optical method. The results suggest that humic-like substances (sodium hydroxide (NaOH)-soluble), polar OCs (methanol-soluble), and iron oxides are responsible for 9%, 4%, and 14% (sample means) of the total light absorption, respectively, in our samples, though it should also be noted that there is great variance in these means. The total light absorption due to non-BC LAPs estimated by chemical methods is lower than that estimated by optical method by about 10% in all sampling regions. Reasons for this difference are explored."

Edit - See also:

http://www.slate.com/blogs/future_tense/2015/01/13/greenland_s_dark_snow_is_coming_to_america_photos.html
« Last Edit: January 16, 2015, 01:07:35 AM by AbruptSLR »
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #369 on: January 16, 2015, 01:54:32 AM »
"… a study by the Centre on the Problems of Ecology and Productivity of Forests at the Russian Academy of Sciences has warned that, due to unsustainable forest policy in Russia and negative climate impacts, net CO2 absorption by the country's forests may drop to zero towards the mid-2040s."

http://www.scientificamerican.com/article/russia-s-forests-overlooked-in-climate-change-fight1/
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #370 on: January 19, 2015, 05:18:08 PM »
From a climate change point of view, the fact that the richest 1 percent will own more than the other 99 percent by 2016, is a positive feedback for global warming for reasons include: (a) it induces the poorer people to have a higher birthrates in order to survive in old age; (b) it promotes fossil fuel dependent growth focused capitalism; and (c) it helps to degrade the natural environment (which currently absorbs a lot of CO₂).

http://www.oxfam.org/en/pressroom/pressreleases/2015-01-19/richest-1-will-own-more-all-rest-2016

Quote: "The combined wealth of the richest 1 percent will overtake that of the other 99 percent of people next year unless the current trend of rising inequality is checked, Oxfam warned today ahead of the annual World Economic Forum meeting in Davos."

See also:

http://www.sacbee.com/news/business/article7514303.html

Extract: "The richest 1 percent of the population will own more than half the world's wealth by 2016, Oxfam International said in a report released as the World Economic Forum begins in Davos, Switzerland.
Oxfam said the world's richest people saw their share of global wealth jump to 48 percent last year from 44 percent in 2009. Rising inequality is holding back the fight against global poverty as the world's biggest companies lobby the U.S. and European Union for beneficial tax changes at a time when average taxpayers are still paying the bill for the financial crisis, Oxfam said."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #371 on: January 19, 2015, 09:54:48 PM »
The linked article quantifies yet another positive feedback factor that was not fully accounted for in AR5; which is the release of organic carbon from glaciers and ice sheets:

Eran Hood, Tom J. Battin, Jason Fellman, Shad O'Neel & Robert G. M. Spencer, (2015), "Storage and release of organic carbon from glaciers and ice sheets", Nature Geoscience, doi:10.1038/ngeo2331

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2331.html

Abstract: "Polar ice sheets and mountain glaciers, which cover roughly 11% of the Earth's land surface, store organic carbon from local and distant sources and then release it to downstream environments. Climate-driven changes to glacier runoff are expected to be larger than climate impacts on other components of the hydrological cycle, and may represent an important flux of organic carbon. A compilation of published data on dissolved organic carbon from glaciers across five continents reveals that mountain and polar glaciers represent a quantitatively important store of organic carbon. The Antarctic Ice Sheet is the repository of most of the roughly 6 petagrams (Pg) of organic carbon stored in glacier ice, but the annual release of glacier organic carbon is dominated by mountain glaciers in the case of dissolved organic carbon and the Greenland Ice Sheet in the case of particulate organic carbon. Climate change contributes to these fluxes: approximately 13% of the annual flux of glacier dissolved organic carbon is a result of glacier mass loss. These losses are expected to accelerate, leading to a cumulative loss of roughly 15 teragrams (Tg) of glacial dissolved organic carbon by 2050 due to climate change — equivalent to about half of the annual flux of dissolved organic carbon from the Amazon River. Thus, glaciers constitute a key link between terrestrial and aquatic carbon fluxes, and will be of increasing importance in land-to-ocean fluxes of organic carbon in glacierized regions."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #372 on: January 19, 2015, 10:28:13 PM »
The linked reference (with an open access pdf) emphasizes our current poor understanding of the current and future atmospheric compositions with regard to ozone and hydroxyl ions as emphasized by the following extract showing that the hydroxyl driven lifetime for methane predicted by different models differ by a factor of 2 (which is not very reassuring).  Furthermore, the attached associated image shows the projected extent of damage to land plant life of future ground-level ozone concentrations, which is another positive feedback for global warming.

Extract: "The oxidation capacity of the atmosphere remains poorly characterised in a number of environmentally sensitive regions, with an order of magnitude difference between measurements and models. Both measurements and our understanding of the key chemical processes have large uncertainties. One example of this lack of understanding is the uncertainty in future methane concentrations, with models predicting •OH driven lifetimes that differ by a factor of 2."

S. Madronich,   M. Shao,   S. R. Wilson,   K. R. Solomon,   J. D. Longstreth and   X. Y. Tang, (2015), "Changes in air quality and tropospheric composition due to depletion of stratospheric ozone and interactions with changing climate: implications for human and environmental health",  Photochem. Photobiol. Sci.,14, 149-169, DOI: 10.1039/C4PP90037E


http://pubs.rsc.org/en/content/articlelanding/2015/pp/c4pp90037e#!divAbstract

Abstract: "UV radiation is an essential driver for the formation of photochemical smog, which includes ground-level ozone and particulate matter (PM). Recent analyses support earlier work showing that poor outdoor air quality is a major environmental hazard as well as quantifying health effects on regional and global scales more accurately. Greater exposure to these pollutants has been linked to increased risks of cardiovascular and respiratory diseases in humans and is associated globally with several million premature deaths per year. Ozone also has adverse effects on yields of crops, leading to loss of billions of US dollars each year. These detrimental effects also may alter biological diversity and affect the function of natural ecosystems. Future air quality will depend mostly on changes in emission of pollutants and their precursors, but changes in UV radiation and climate will contribute as well. Significant reductions in emissions, mainly from the energy and transportation sectors, have already led to improved air quality in many locations. Air quality will continue to improve in those cities/states that can afford controls, and worsen where the regulatory infrastructure is not available. Future changes in UV radiation and climate will alter the rates of formation of ground-level ozone and photochemically-generated particulate matter and must be considered in predictions of air quality. The decrease in UV radiation associated with recovery of stratospheric ozone will, according to recent global atmospheric model simulations, lead to increases in ground-level ozone at most locations. If correct, this will add significantly to future ground-level ozone trends. However, the spatial resolution of these global models is insufficient to inform policy at this time, especially for urban areas. UV radiation affects the atmospheric concentration of hydroxyl radicals, ˙OH, which are responsible for the self-cleaning of the atmosphere. Recent measurements confirm that, on a local scale, ˙OH radicals respond rapidly to changes in UV radiation. However, on large (global) scales, models differ in their predictions by nearly a factor of two, with consequent uncertainties for estimating the atmospheric lifetime and concentrations of key greenhouse gases and air pollutants. Projections of future climate need to consider these uncertainties. No new negative environmental effects of substitutes for ozone depleting substances or their breakdown-products have been identified. However, some substitutes for the ozone depleting substances will continue to contribute to global climate change if concentrations rise above current levels."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #373 on: January 20, 2015, 06:42:01 PM »
The linked reference provides evidence that water stress (associated with global warming) is contributing to changes in temperate forest structure including a 50% decline in large trees.  This identified trend could serve as a positive feedback for global warming.

Patrick J. McIntyre, James H. Thorne, Christopher R. Dolanc, Alan L. Flint, Lorraine E. Flint, Maggi Kelly, and David D. Ackerly, (2015), "Twentieth-century shifts in forest structure in California: Denser forests, smaller trees, and increased dominance of oaks", PNAS, doi: 10.1073/pnas.1410186112

http://www.pnas.org/content/early/2015/01/14/1410186112

Significance
Declines in the number of large trees in temperate and tropical forests have attracted attention, given their disproportionate importance to forest structure, function, and carbon storage. Yet, factors responsible for these declines are unclear. By comparing historic (1930s) and contemporary (2000s) surveys of California forests, we document that across 120,000 km2, large trees have declined by up to 50%, corresponding to a 19% decline in average basal area and associated biomass, despite large increases in small tree density. Contemporary forests also exhibit increased dominance by oaks over pines. Both large tree declines and increased oak dominance were associated with increases in climatic water deficit, suggesting that water stress may be contributing to changes in forest structure and function across large areas.

Abstract
We document changes in forest structure between historical (1930s) and contemporary (2000s) surveys of California vegetation through comparisons of tree abundance and size across the state and within several ecoregions. Across California, tree density in forested regions increased by 30% between the two time periods, whereas forest biomass in the same regions declined, as indicated by a 19% reduction in basal area. These changes reflect a demographic shift in forest structure: larger trees (>61 cm diameter at breast height) have declined, whereas smaller trees (<30 cm) have increased. Large tree declines were found in all surveyed regions of California, whereas small tree increases were found in every region except the south and central coast. Large tree declines were more severe in areas experiencing greater increases in climatic water deficit since the 1930s, based on a hydrologic model of water balance for historical climates through the 20th century. Forest composition in California in the last century has also shifted toward increased dominance by oaks relative to pines, a pattern consistent with warming and increased water stress, and also with paleohistoric shifts in vegetation in California over the last 150,000 y.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #374 on: January 21, 2015, 12:36:09 AM »
The linked reference provides physical measurements of the attenuation of sinking particulate organic carbon flux due to warming of ocean waters.  This provides direct evidence that the oceans will absorb less CO₂ with increasing global warming; which is a clear positive feedback mechanism:

Chris M. Marsay, Richard J. Sanders, Stephanie A. Henson, Katsiaryna Pabortsava, Eric P. Achterberg, and Richard S. Lampitt, (2015), "Attenuation of sinking particulate organic carbon flux through the mesopelagic ocean", PNAS, doi: 10.1073/pnas.1415311112

http://www.pnas.org/content/early/2015/01/02/1415311112.abstract


Abstract: "The biological carbon pump, which transports particulate organic carbon (POC) from the surface to the deep ocean, plays an important role in regulating atmospheric carbon dioxide (CO2) concentrations. We know very little about geographical variability in the remineralization depth of this sinking material and less about what controls such variability. Here we present previously unpublished profiles of mesopelagic POC flux derived from neutrally buoyant sediment traps deployed in the North Atlantic, from which we calculate the remineralization length scale for each site. Combining these results with corresponding data from the North Pacific, we show that the observed variability in attenuation of vertical POC flux can largely be explained by temperature, with shallower remineralization occurring in warmer waters. This is seemingly inconsistent with conclusions drawn from earlier analyses of deep-sea sediment trap and export flux data, which suggest lowest transfer efficiency at high latitudes. However, the two patterns can be reconciled by considering relatively intense remineralization of a labile fraction of material in warm waters, followed by efficient downward transfer of the remaining refractory fraction, while in cold environments, a larger labile fraction undergoes slower remineralization that continues over a longer length scale. Based on the observed relationship, future increases in ocean temperature will likely lead to shallower remineralization of POC and hence reduced storage of CO2 by the ocean."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #375 on: January 21, 2015, 01:26:16 AM »
The linked reference indicates that positive feedback associated with temperature, water vapor and clouds dominate Arctic Amplification and that surface albedo feedback is the second main contributor:

Pithan, F. and T. Mauritsen (2014), "Arctic amplification dominated by temperature feedbacks in contemporary climate models", Nature Geoscience, 7, 181-184, doi:10.1038/ngeo2071

http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2071.html

Abstract: " Climate change is amplified in the Arctic region. Arctic amplification has been found in past warm and glacial periods, as well as in historical observations and climate model experiments. Feedback effects associated with temperature, water vapour and clouds have been suggested to contribute to amplified warming in the Arctic, but the surface albedo feedback—the increase in surface absorption of solar radiation when snow and ice retreat—is often cited as the main contributor. However, Arctic amplification is also found in models without changes in snow and ice cover. Here we analyse climate model simulations from the Coupled Model Intercomparison Project Phase 5 archive to quantify the contributions of the various feedbacks. We find that in the simulations, the largest contribution to Arctic amplification comes from a temperature feedbacks: as the surface warms, more energy is radiated back to space in low latitudes, compared with the Arctic. This effect can be attributed to both the different vertical structure of the warming in high and low latitudes, and a smaller increase in emitted blackbody radiation per unit warming at colder temperatures. We find that the surface albedo feedback is the second main contributor to Arctic amplification and that other contributions are substantially smaller or even oppose Arctic amplification."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #376 on: January 22, 2015, 05:05:36 PM »
"The fuse is blown...this thing is falling apart"

"The community is very conservative in general with timescales. All the indications we've collected in the past decades are actually pointing towards shorter timescales than what the models are able to replicate..."

Shockingly honest interview with Rignot:

https://www.youtube.com/watch?x-yt-ts=1421782837&x-yt-cl=84359240&v=ANBHZfH4l6M#t=72

(Thanks to todaysguestis at robertscribbler's blog, and apologies if this has already been linked.)
« Last Edit: January 22, 2015, 05:17:33 PM by wili »
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #377 on: January 22, 2015, 06:04:00 PM »
wili,

Thanks for the link to the great interview with Rignot at the 2014 AGU. 

Many people incorrectly assume that because GCM hindcasts of the paleo-record match the record to within the broad error margins of the paleo-record that society is safe from future abrupt climate change (including from ASLR) because our current generation of GCM projections (which are typically calibrated assuming constant values for Equilibrium Climate Sensitivity, ECS, and consequently higher values for slow response contributors to high Earth System Sensitivity, ESS) do not yet indicate sufficient risk.  Such thinking is particularly naïve (as indicated by Rignot) for reasons including:

1.  Paleo-models do not (cannot) differentiate between cases with constant ECS and high ESS from more likely cases of rapidly increasing (with global warming) ECS and relative lower values of ESS.  Numerous Earth System Models, ESMs, confirm that ECS (which controls temperature increase for a given radiative forcing on the time-scale of a century) do increase with increasing temperatures and if Sherwood et al 2014 are correct about the influence of tropical atmospheric convective mixing, then the rate of ECS increase could be fast (say increasing from 3 C to 10 C by 2100).
2.  In the Paleo-thread I discuss how the interactions of earth systems (such as polar albedo and tropical rainforests) can chaotically interact with the ENSO to ratchet the world's into progressively higher climate states (with progressively higher values of ECS).
3. I have pointed out in this thread and others that temporary negative feedback mechanisms such as Asian aerosols, a burst of land-based vegetation growth, and the growth of the Antarctic sea ice extent, will likely weaken (or reverse) dramatically over the next few decades, which will make it clear that we have been living in a "Fool's Paradise" in recent decades.  Also, with regard to Antarctic sea ice extent, I would like to note that we are now entering into warming phases for both the PDO and the AMO which will make El Nino events, which will telecommunicate more tropical energy to the West Antarctic, particularly in the October to February timeframe when El Nino events can cause the ABSL to direct more warm CDW into the Amundsen Bellingshausen Seas area; and this combination of warmer ocean water and warmer atmospheres in Western Antarctica will lead to reduced local sea ice extent and consequently to a reduced sea ice albedo during the Austral Spring and Summer months.

Best,
ASLR
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #378 on: January 23, 2015, 12:58:29 AM »
The linked reference (with an open access preprint) provides a discussion of a new framework for understanding climate sensitivity using adjustments that are responses to forcings that are not controlled by global mean warming.  This new approach offers the promise of reducing some of the uncertainties associated with the range of climate sensitivity:

Sherwood, S. C., S. Bony, O. Boucher, C. Bretherton, P. M. Forster, J. M. Gregory and B. Stevens, (2014), "Adjustments in the forcing-feedback framework for understanding climate change", Bull. Amer. Meteorol. Soc., doi: http://dx.doi.org/10.1175/BAMS-D-13-00167.1


http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-13-00167.1

For an open access pre-print:

http://web.science.unsw.edu.au/~stevensherwood/forcefeed_v2.2.1.pdf

Abstract: "The traditional forcing-feedback framework has provided an indispensable basis for discussing global climate changes. However, as analysis of model behavior has become more detailed, shortcomings and ambiguities in the framework have become more evident and physical effects unaccounted for by the traditional framework have become interesting. In particular, the new concept of adjustments, which are responses to forcings that are not mediated by the global mean temperature, has emerged. This concept, related to the older ones of climate efficacy and stratospheric adjustment, is a more physical way of capturing unique responses to specific forcings. We present a pedagogical review of the adjustment concept, why it is important, and how it can be used. The concept is particularly useful for aerosols, where it helps to organize what has become a complex array of forcing mechanisms.  It also helps clarify issues around cloud and hydrological response, transient vs. equilibrium climate change, and geoengineering."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #379 on: January 24, 2015, 07:36:32 PM »
As a follow-up to my immediate prior post #387, I would like to note that now that AR5 has been released, the IPCC should now be working on new radiative forcing scenarios to replace the Recommended Concentration Pathway, RCP, scenarios, and that hopefully the IPCC will include some of Sherwood et al 2014's thinking about adjustments to the forcing-feedback framework.  In this regards I make the following comments:

1.  The current anthropogenic aerosol allowances within the RCP scenario are dependent on the amount of economic activity assumed within the scenario.  Thus RCP 8.5 has a large amount of negative feedback from large anthropogenic aerosols.  As we now know that at least China will make a dramatic effort to cut aerosol emissions while maintaining a relatively high consumption-driven economic level; hopefully the IPCC will break-out the anthropogenic aerosol forcing component to allow scientists to reduce these large negative feedbacks from their forcing models.

2. As the oceans have been absorbing excess heat for the past 15 to 20-years of the negative phase of the PDO/IPO cycle; and the oceans will also most certainly be increasing their surface temperatures faster than normal for the next 15 to 30 years; hopefully either the IPCC will require the use of state of the art Earth System Models, ESMs, that can capture this reality (which will active strong positive feedback mechanisms faster than previously assumed); and/or will require GCM projections to use adjustment factors to more accurately model this reality.

3.  Ocean acidification can act as a positive feedback by encouraging the reproduction of smaller plankton that do not sink down to remove carbon from the atmospheric cycle, and at high levels can kill many types of plankton.  Again advanced ESMs many capture this reality, otherwise GCM projections should have adjustment factors to correct for this consideration.

4. As the world climate is temporarily ratcheted upwards into more active climate states by seemingly chaotic phenomena (such as extreme El Nino events, and/or events will large drops in Arctic Sea Ice extents), many positive feedback mechanisms many be strengthened (eg: drought/flood impacts on tropical rainforests and/or degradation of permafrost) sufficiently to keep the climate in the higher state of activity, which would require GCM projections to use an adjustment factor for increasing values of Equilibrium Climate Sensitivity, ECS, on time-frames of decades.

5. Lastly, I re-iterate that the RCP scenarios assumed tighter uncertainly ranges for anthropogenic emissions under the assumption that policy makers would enact policies to better control these emissions.  Therefore, I believe that any future scenarios should better assess uncertainties associated with the impacts of such alternate fossil fuels as fracking, tar sands, etc. and for economic development in the 3rd world where regulations on GHG emissions are lacks.
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #380 on: January 26, 2015, 05:36:06 PM »
The linked paper indicates that it is likely that not only will extreme El Nino events become twice as frequent due to global warming by 2100 but so will extreme La Nina events.  To my way of thinking this implies still more stress on the Tropical Rainforests, which will result in a stronger positive feedback mechanism than previously thought:

Wenju Cai, Guojian Wang, Agus Santoso, Michael J. McPhaden, Lixin Wu, Fei-Fei Jin, Axel Timmermann, Mat Collins, Gabriel Vecchi, Matthieu Lengaigne, Matthew H. England, Dietmar Dommenget, Ken Takahashi & Eric Guilyardi, (2015), "Increased frequency of extreme La Niña events under greenhouse warming", Nature Climate Change, doi:10.1038/nclimate2492


http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2492.html


Abstract: "The El Niño/Southern Oscillation is Earth’s most prominent source of interannual climate variability, alternating irregularly between El Niño and La Niña, and resulting in global disruption of weather patterns, ecosystems, fisheries and agriculture. The 1998–1999 extreme La Niña event that followed the 1997–1998 extreme El Niño event switched extreme El Niño-induced severe droughts to devastating floods in western Pacific countries, and vice versa in the southwestern United States. During extreme La Niña events, cold sea surface conditions develop in the central Pacific, creating an enhanced temperature gradient from the Maritime continent to the central Pacific. Recent studies have revealed robust changes in El Niño characteristics in response to simulated future greenhouse warming, but how La Niña will change remains unclear. Here we present climate modelling evidence, from simulations conducted for the Coupled Model Intercomparison Project phase 5, for a near doubling in the frequency of future extreme La Niña events, from one in every 23 years to one in every 13 years. This occurs because projected faster mean warming of the Maritime continent than the central Pacific, enhanced upper ocean vertical temperature gradients, and increased frequency of extreme El Niño events are conducive to development of the extreme La Niña events. Approximately 75% of the increase occurs in years following extreme El Niño events, thus projecting more frequent swings between opposite extremes from one year to the next."

See also:
http://www.carbonbrief.org/blog
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #381 on: January 30, 2015, 01:08:43 AM »
The linked reference indicates that injecting CO₂ into a brine-rock environment will not sequester as much CO₂ as previously assumed.  This implies that it will be more difficult to stay off of a BAU pathway.

Yossi Cohen and Daniel H. Rothman, (2015) "Long-time evolution of sequestered CO2 in porous media", the Proceedings of the Royal Society A

Abstract: "CO2 sequestration in subsurface reservoirs is important for limiting atmospheric CO2 concentrations. However, a complete physical picture able to predict the structure developing within the porous medium is lacking. We investigate theoretically reactive transport in the long-time evolution of carbon in the brine-rock environment. As CO2 is injected into a brine-rock environment, a carbonate-rich region is created amid brine. Within the carbonate-rich region minerals dissolve and migrate from regions of high concentration to low concentration, along with other dissolved carbonate species. This causes mineral precipitation at the interface between the two regions. We argue that precipitation in a small layer reduces diffusivity, and eventually causes mechanical trapping of the CO2. Consequently, only a small fraction of the CO2 is converted to solid mineral; the remainder either dissolves in water or is trapped in its original form. We also study the case of a pure CO2 bubble surrounded by brine and suggest a mechanism that may lead to a carbonate-encrusted bubble due to structural diffusion."

See:
http://newsoffice.mit.edu/2015/carbon-dioxide-sequestration-doubts-0120

http://www.reportingclimatescience.com/news-stories/article/carbon-sequestration-may-not-work-says-study.html
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #382 on: February 04, 2015, 05:55:42 PM »
The linked article (and associated image & extract) indicates that GHG emissions from farming rose 13% after 1990.  With a growing world population and a growing global middle class, this trend will be difficult to reverse anytime soon:

http://www.climatecentral.org/news/farming-now-worse-for-climate-than-deforestation-18629

Extract: "Greenhouse gases released by farming, such as methane from livestock and rice paddies, and nitrous oxides from fertilizers and other soil treatments rose 13 percent after 1990, the study concluded. Agricultural climate pollution is mostly caused by livestock. Cows and buffalo are the worst offenders — their ruminating guts and decomposing waste produce a lot of methane. They produce so much methane, and eat so much fertilized feed, that livestock are blamed for two-thirds of agriculture’s climate pollution every year."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #383 on: February 07, 2015, 12:12:43 AM »
The linked article indicates that on relatively long time-scales CO₂ emissions from mid-ocean ridge eruptions can be a meaningful positive forcing mechanism.  This makes me wonder what would happen to the rate of such eruptions if the WAIS were to effectively collapse by 2100:

Maya Tolstoy, (2015), "Mid-ocean ridge eruptions as a climate valve", Geophysical Research Letters, DOI: 10.1002/2014GL063015

http://onlinelibrary.wiley.com/doi/10.1002/2014GL063015/abstract

Abstract: "Seafloor eruption rates, and mantle melting fueling eruptions, may be influenced by sea-level and crustal loading cycles at scales from fortnightly to 100 kyr. Recent mid-ocean ridge eruptions occur primarily during neap tides and the first 6 months of the year, suggesting sensitivity to minor changes in tidal forcing and orbital eccentricity. An ~100 kyr periodicity in fast-spreading seafloor bathymetry, and relatively low present-day eruption rates, at a time of high sea-level and decreasing orbital eccentricity suggest a longer term sensitivity to sea-level and orbital variations associated with Milankovitch cycles. Seafloor spreading is considered a small but steady contributor of CO2 to climate cycles on the 100 kyr time scale, however this assumes a consistent short-term eruption rate. Pulsing of seafloor volcanic activity may feed back into climate cycles, possibly contributing to glacial/inter-glacial cycles, the abrupt end of ice ages, and dominance of the 100 kyr cycle."

See also:

http://www.nbcnews.com/science/environment/scientists-link-underwater-eruptions-climate-change-n301746
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #384 on: February 25, 2015, 04:42:38 PM »
The linked reference indicates that continued ocean acidification of the Southern Ocean under dynamic light conditions will result in a reduction in CO₂ sequestration into the Southern Ocean; thus indicating that greater dependence on an intense use of solar radiation management, SRM, will be likely in order to counter this trend.  Unfortunately, the most likely form of SRM accelerates ocean acidification which would require still more dependence on heavy SRM use; resulting in a likely anthropogenic positive feedback driving atmosphere CO₂ levels upward even if/when geoengineering is applied (say after 2050):

Hoppe, C. J. M., Holtz, L.-M., Trimborn, S. and Rost, B. (2015), Ocean acidification decreases the light-use efficiency in an Antarctic diatom under dynamic but not constant light. New Phytologist. doi: 10.1111/nph.13334

http://onlinelibrary.wiley.com/doi/10.1111/nph.13334/abstract?utm_content=bufferbc7d4&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

• Summary: "There is increasing evidence that different light intensities strongly modulate the effects of ocean acidification (OA) on marine phytoplankton. The aim of the present study was to investigate interactive effects of OA and dynamic light, mimicking natural mixing regimes.
• The Antarctic diatom Chaetoceros debilis was grown under two pCO2 (390 and 1000 μatm) and light conditions (constant and dynamic), the latter yielding the same integrated irradiance over the day. To characterize interactive effects between treatments, growth, elemental composition, primary production and photophysiology were investigated.
• Dynamic light reduced growth and strongly altered the effects of OA on primary production, being unaffected by elevated pCO2 under constant light, yet significantly reduced under dynamic light. Interactive effects between OA and light were also observed for Chl production and particulate organic carbon quotas.
• Response patterns can be explained by changes in the cellular energetic balance. While the energy transfer efficiency from photochemistry to biomass production (Φe,C) was not affected by OA under constant light, it was drastically reduced under dynamic light. Contrasting responses under different light conditions need to be considered when making predictions regarding a more stratified and acidified future ocean."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #385 on: March 03, 2015, 04:50:47 PM »
The following article indicates that the world's recovering economy and the growing middle class appetite for meat & high-end produce, likely spells an acceleration of deforestation of the Amazon and other tropical rainforests.

http://www.newscientist.com/article/dn27056-amazon-deforestation-soars-after-a-decade-of-stability.html#.VPXWx6PTlMs


Extract: "Deforestation in the Amazon has skyrocketed in the past half a year, according to analysis of satellite images issued by Brazil's non-profit research institute, IMAZON.
The results compared the deforestation in a particular month with figures from the same month a year before, and the difference ranged from a 136 per cent increase in August to a 467 per cent rise in October.

"Rates have way more than doubled over the equivalent period in the previous year," says Phillip Fearnside, an ecologist with Brazil's Amazon research agency INPA. And the numbers probably underestimate the problem, because the satellite system used, DETER, can only recognise clearings larger than 250,000 square metres. Many farm plots are smaller than that.



Several factors may be to blame, according to Fearnside. As the world economy continues to recover, demand has increased for beef and soybeans – commodities that are often produced on deforested land – and so too have the prices for these risen on the global market. The Brazilian currency, the real, has been gaining strength, which has spurred investment in new agricultural projects.

Fearnside also blames an update to Brazil's Forest Code, enacted in 2012, which includes an amnesty for individuals who cleared rainforest illegally before 2008. "The expectation now is that if you violate the law and cut down the forest without a permit, you'll eventually be pardoned," he says. "It's a very perverse message.""
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #386 on: March 03, 2015, 05:54:49 PM »
People who are counting on the continued increase of CO₂ absorbed by global warming stimulated plant growth may be in for an unpleasant surprise for reasons including increased insect activity (see link & extract below), but also due to such factors as: heat stress, ozone stress, droughts & floods, and wildfires:

http://www.newscientist.com/article/dn27064-hungry-insects-may-halve-forest-carbon-sink-capacity.html?cmpid=RSS

Extract: " Previous studies showed increased carbon dioxide levels upped the rate of photosynthesis in trees by approximately 50 per cent.
Bugs, however, could lessen this capacity dramatically, according to a new study. "Insects may change in response to elevated carbon dioxide levels and limit or compromise the capacity of forests to serve as carbon sinks," says Richard Lindroth, an ecologist at the University of Wisconsin-Madison."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #387 on: March 26, 2015, 03:57:16 PM »
The linked article indicates that increasing human pressure (especially from farming) on northern latitude wetlands is resulting in a growing positive feedback mechanism:

Ana Maria Roxana Petrescu et. al. (2015), "Uncertain climate footprint of wetlands under human pressure", Proceedings of the National Academy of Science, PNAS Early Edition, doi: 10.1073/pnas.1416267112


http://www.pnas.org/content/early/2015/03/19/1416267112


Abstract: "Significant climate risks are associated with a positive carbon–temperature feedback in northern latitude carbon-rich ecosystems, making an accurate analysis of human impacts on the net greenhouse gas balance of wetlands a priority. Here, we provide a coherent assessment of the climate footprint of a network of wetland sites based on simultaneous and quasi-continuous ecosystem observations of CO2 and CH4 fluxes. Experimental areas are located both in natural and in managed wetlands and cover a wide range of climatic regions, ecosystem types, and management practices. Based on direct observations we predict that sustained CH4 emissions in natural ecosystems are in the long term (i.e., several centuries) typically offset by CO2 uptake, although with large spatiotemporal variability. Using a space-for-time analogy across ecological and climatic gradients, we represent the chronosequence from natural to managed conditions to quantify the “cost” of CH4 emissions for the benefit of net carbon sequestration. With a sustained pulse–response radiative forcing model, we found a significant increase in atmospheric forcing due to land management, in particular for wetland converted to cropland. Our results quantify the role of human activities on the climate footprint of northern wetlands and call for development of active mitigation strategies for managed wetlands and new guidelines of the Intergovernmental Panel on Climate Change (IPCC) accounting for both sustained CH4 emissions and cumulative CO2 exchange."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #388 on: March 27, 2015, 04:50:10 PM »
The linked reference indicates that the permafrost will increasingly become a carbon source with increasing global warming:

Charles D. Kovena, David M. Lawrence and William J. Rileya (2015), "Permafrost carbon−climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics", Proceedings of the National Academy of Sciences (PNAS), doi: 10.1073/pnas.1415123112

http://www.pnas.org/content/112/12/3752.abstract

Abstract: "Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the post-thaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon−nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #389 on: March 29, 2015, 11:52:49 AM »
The linked reference (with an open access paper) indicates that climate change has caused the breeding seasons of Asian and Formosan subterranean termites to overlap in South Florida (& their breeding seasons may soon also overlap in Hawaii & Taiwan), resulting in cross breeding a new "super" termite that is much worse than either of its two parents (that are already two of the most destructive termites in the world).  It is unknown whether the hybrid super termites are fertile; however, as they live for about 20-years, they can still cause much damage even if infertile.

I note that termites are the second largest source of global natural methane emissions as they produce the gas as part of their normal digestive process.  Therefore, if with continued climate change, such "super" termites become more widespread, then these insects could become yet another positive feedback mechanism (particularly if they spread into the Amazon & Congo rainforests).


Chouvenc T, Helmick EE, Su N-Y (2015) Hybridization of Two Major Termite Invaders as a Consequence of Human Activity. PLoS ONE 10(3): e0120745. doi:10.1371/journal.pone.0120745

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0120745


Abstract: "While hybridization of an invasive species with a native species is a common occurrence, hybridization between two invasive species is rare. Formosan subterranean termites (Coptotermes formosanus) and Asian subterranean termites (C. gestroi) are both ecologically successful and are the two most economically important termite pests in the world. Both species have spread throughout many areas of the world due to human activity; however, their distributions overlap in only three narrow areas because of distinct ecological requirements. In south Florida, where C. formosanus and C. gestroi are both invasive, the dispersal flight seasons of both species overlapped for the first time on record in 2013 and 2014. Pairings of heterospecific individuals were readily observed in the field and C. gestroi males preferentially engaged in mating behavior with C. formosanus females rather than females from their own species. In the laboratory, heterospecific and conspecific pairings had an equal colony establishment rate, but heterospecific incipient colonies had twice the growth rate of conspecific incipient colonies, suggesting a potential case of hybrid vigor. As all pre-zygotic barriers were lifted between the two species in the field, the apparent absence of post-zygotic barriers in the laboratory raises the possibility for introgressive hybridization in south Florida. While laboratory observations remain to be confirmed in the field, and the alate hybrid fertility is currently unknown, our results raise a tangible concern about the hybridization of two major destructive pest species. Such hybridization would likely be associated with a new economic impact."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #390 on: September 30, 2015, 07:49:29 PM »
While the linked reference focuses on the projected rapid increase in Antarctic soil fungi with continued global warming; I point-out that fungi & bacteria can also colonize on the surface of sufficiently warm ice; and if this were to occur at a rate paralleling the growing Antarctic soil fungi then an associated increase in Antarctic albedo could become a meaningful issue before 2100:

Newsham KK, Hopkins DW, Carvalhais LC, Fretwell PT, Rushton SP, O'Donnell AG, Dennis PG (2015) Relationship between soil fungal diversity and temperature in the maritime Antarctic. Nature Climate Change. doi: 10.1038/nclimate2806

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2806.html

Abstract: "Soil fungi have pivotal ecological roles as decomposers, pathogens and symbionts. Alterations to their diversity arising from climate change could have substantial effects on ecosystems, particularly those undergoing rapid warming that contain few species. Here, we report a study using pyrosequencing to assess fungal diversity in 29 soils sampled from a 1,650 km climatic gradient through the maritime Antarctic, the most rapidly warming region in the Southern Hemisphere. Using a ‘space-for-time’ substitution approach, we show that soil fungal diversity is higher in warmer habitats, with increases of 4.7 (observed) and 11.3 (predicted) fungal taxa per degree Celsius rise in surface temperature along the transect. Among 22 predictor variables, air temperature was the strongest and most consistent predictor of diversity. We propose that the current rapid warming in the maritime Antarctic (0.34 °C per decade6) will facilitate the colonization of soil by a wider diversity of fungi than at present, with data from regression models suggesting 20–27% increases in fungal species richness in the southernmost soils by 2100. Such increases in diversity, which provide a sentinel for changes at lower latitudes, are likely to have substantial effects on nutrient cycling and, ultimately, productivity in the species-poor soils of maritime Antarctica."

Also see:
http://www.9news.com.au/national/2015/09/29/01/04/temperature-affects-fungi-in-antarctica


Extract: "Author Paul Dennis told AAP the research proved temperature change was the main factor that determined soil fungal diversity and could affect soil nutrients.
"It is important because this is the most rapidly warming part of Antarctica and out of everything that we measured to try and understand what controls fungal diversity, we've found temperature is the key thing," Dr Dennis said.
"Given that the region is warming, that means the communities are already changing and will continue to change.""
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #391 on: November 02, 2015, 04:52:00 PM »
The linked article discusses the increasing trend for expanding sub-arctic farming in Alaska; which will decrease albedo, which will increase temperatures, which will increase farming and thus qualifies as a positive feedback cycle:

http://www.npr.org/2015/11/01/453337333/rising-temperatures-kick-start-sub-arctic-farming-in-alaska

Extract: " In fact, 2014 ranked as the warmest year on record in Alaska. Rick Thoman, a climatologist with the National Weather Service, says that's not just a fluke, it's a trend.
"What the last century of weather observations and climate observations in Alaska are telling us is that over the last couple of decades it's been significantly warmer over most of Alaska than it was during the middle and later part of the 20th Century," Thoman says.
He says the long-term average temperature for Bethel for an entire year had been 29 degrees, but in 2014 it was nearly 35 degrees. That's only six degrees difference, but it's significant because now it's right above freezing, which allows more things to grow outside."
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Re: Selected Forcing Factor for Abrupt SLR from the Collapse of the WAIS
« Reply #392 on: January 11, 2016, 11:07:42 PM »
The linked reference documents how while large Antarctic icebergs melt they provide nutrients into the nearby waters that induce local plankton blooms that absorb CO₂, and thus act as a negative feedback mechanism as more large icebergs are calved with continuing global warming.  While their research should be used to update ESM projections, the authors do not consider the case of the WAIS collapsing this century, which (together with ocean acidification) could result in more Southern Ocean plankton die-offs and fewer plankton blooms, eventually resulting in a positive feedback for global warming:

Luis P. A. M. Duprat, Grant R. Bigg & David J. Wilton (2016), "Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs", Nature Geoscience, doi:10.1038/ngeo2633


http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2633.html


Abstract: "Primary productivity is enhanced within a few kilometres of icebergs in the Weddell Sea owing to the input of terrigeneous nutrients and trace elements during iceberg melting. However, the influence of giant icebergs, over 18 km in length, on marine primary production in the Southern Ocean is less well studied. Here we present an analysis of 175 satellite images of open ocean colour before and after the passage of 17 giant icebergs between 2003 and 2013. We detect substantially enhanced chlorophyll levels, typically over a radius of at least 4–10 times the iceberg’s length, that can persist for more than a month following passage of a giant iceberg. This area of influence is more than an order of magnitude larger than that found for sub-kilometre scale icebergs or in ship-based surveys of giant icebergs. Assuming that carbon export increases by a factor of 5–10 over the area of influence, we estimate that up to a fifth of the Southern Ocean’s downward carbon flux originates with giant iceberg fertilization. We suggest that, if giant iceberg calving increases this century as expected, this negative feedback on the carbon cycle may become more important."

See also:
https://www.washingtonpost.com/news/energy-environment/wp/2016/01/11/the-surprising-way-that-huge-icebergs-slow-down-climate-change-a-little/
“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 #393 on: January 14, 2016, 04:33:17 PM »
The linked reference compares 35-years of European Centre Medium-range Weather Forecasts are analyzed to study the relationship between the ENSO and Antarctic weather by season, using 9 El Nino & 9 La Nina events.  While the findings are informative, I would be cautious in extending their findings to project too far into the future as: (a) our current Super El Nino is atypical and may not match the pattern that the authors observed, and (b) climate change is non-stationary, and projections of future behavior is best addressed by state-of-the-art ESMs (like ACME), and not by linearly extending recent observed behavior:

Lee J. Welhouse, Matthew A. Lazzara, Linda M. Keller, Gregory J. Tripoli, and Matthew H. Hitchman (2016), "Composite Analysis of the effects of ENSO events on Antarctica", Journal of Climate ; doi: http://dx.doi.org/10.1175/JCLI-D-15-0108.1


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0108.1


Abstract: "Previous investigations of the relationship between the El Niño Southern Oscillation (ENSO) and Antarctic climate have focused on regions which are impacted by both El Niño and La Niña, which favors analysis over the Amundsen and Bellingshausen Seas (ABS). Here, 35 years (1979-2013) of European Centre for Medium-range Weather Forecasts Reanalysis-Interim (ERA-Interim) data are analyzed to investigate the relationship between ENSO and Antarctica for each season using a compositing method which includes 9 El Niño and 9 La Niña periods. Composites of 2 m temperature (T2 m), sea level pressure (SLP), 500 hPa geopotential height, sea surface temperatures (SST) and 300 hPa geopotential height anomalies were calculated separately for El Niño minus neutral and La Niña minus neutral conditions, to provide an analysis of features associated with each phase of ENSO. These anomaly patterns can differ in important ways from El Niño minus La Niña composites, which may be expected from the geographical shift in tropical deep convection and associated pattern of planetary wave propagation into the Southern Hemisphere. The primary new result is the robust signal, during La Niña, of cooling over East Antarctica. This cooling is found from December through August. The link between the Southern Annular Mode (SAM) and this cooling is explored. Both El Niño and La Niña experience the weakest signal during austral autumn. The peak signal for La Niña occurs during austral summer, while El Niño is found to peak during austral spring."

See also:
http://journals.ametsoc.org/page/connectingthetropics
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson