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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #500 on: April 22, 2016, 07:51:15 PM »
The linked reference (& submitted pdf) uses the CESM to study the differences & similarities between El Ninos and global warming induced El Nino-like SST patterns in the tropical Pacific Ocean (see the attached image).  Among numerous other finding, the study confirms that continued global warming will increase the frequency of intense El Nino events; which will mean more droughts in the tropics which will mean less CO₂ absorption by the rainforests and more CO₂ and CH4 emissions from dead and rotting rainforest vegetation:

Fukai Liu, Yiyong Luo, Jian Lu & Xiuquan Wan (15 April 2016), "Response of the tropical Pacific Ocean to El Niño versus global warming", Climate Dynamics, pp 1-22, DOI 10.1007/s00382-016-3119-2



http://link.springer.com/article/10.1007%2Fs00382-016-3119-2
http://wxmaps.org/jianlu/Liu_Luo_Lu.CLDY15.submitted.pdf


Abstract: "Climate models project an El Niño-like SST response in the tropical Pacific Ocean to global warming (GW). By employing the Community Earth System Model and applying an overriding technique to its ocean component, Parallel Ocean Program version 2, this study investigates the similarity and difference of formation mechanism for the changes in the tropical Pacific Ocean under El Niño and GW. Results show that, despite sharing some similarities between the two scenarios, there are many significant distinctions between GW and El Niño: (1) the phase locking of the seasonal cycle reduction is more notable under GW compared with El Niño, implying more extreme El Niño events in the future; (2) in contrast to the penetration of the equatorial subsurface temperature anomaly that appears to propagate in the form of an oceanic equatorial upwelling Kelvin wave during El Niño, the GW-induced subsurface temperature anomaly manifest in the form of off-equatorial upwelling Rossby waves; (3) while significant across-equator northward heat transport (NHT) is induced by the wind stress anomalies associated with El Niño, little NHT is found at the equator due to a symmetric change in the shallow meridional overturning circulation that appears to be weakened in both North and South Pacific under GW; and (4) heat budget analysis shows that the maintaining mechanisms for the eastern equatorial Pacific warming are also substantially different."
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #501 on: April 22, 2016, 11:10:09 PM »
Old guard IPCC scientists (such as Michael Oppenheimer, see linked article & extract) appear to believe that Hansen et al (2016) concatenated worst, worst, worst case possibility of abrupt sea level rise & associated feedbacks; and consequently they ignore such cases.

http://www.climatecentral.org/news/fate-of-worlds-coastlines-melting-antarctic-ice-20270

Extract: "“The Hansen paper has an extra level of speculation,” Oppenheimer said. “The way I read it is as an interesting scenario, where a lot of worst-case outcomes are concatenated to produce a worst, worst, worst case possibility. It’s a nightmare which is very unlikely to actually come true.”
The paper’s findings rest on a key assumption — that the rate of melting of Antarctic ice will be exponential rather than gradual. The research doesn’t investigate whether that assumption is correct."

Again, Oppenheimer is a long-time participant in the Intergovernmental Panel on Climate Change (IPCC), and per Wikipedia:
Extract: "Together with Jessica O'Reilly and Naomi Oreskes, Oppenheimer discussed the case of the West Antarctic Ice Sheet assessment in IPCC reports in a Social Studies of Science paper 2012. The possible disastrous outcome of a disintegration of the WAIS for global sea levels was assessed in the IPCC Third Assessment Report but was barely addressed in the IPCC Fourth Assessment Report. IPCC authors were less confident about predictions of WAIS disintegration not only due to new science results published since the Third Assessment, but also due to reasons of internal "culture", such as changes of IPCC chairpersons, authors teams, and chapter organization made which it too difficult to project the range of possible futures for the WAIS as desired by governments."
However, it is not only DeConto & Pollard and the unpublished NOAA projections about ASLR that make the Hansen et al (2016) doubling-times for SLR plausible as indicated by some of the following:

- The first attached animation made by solartim27 shows that the pinned iceberg in front of the residual Thwaites Ice Tongue is now (between April 6 & 19 2016) moving; which raises the plausibility that the main Thwaites ice stream might have an unsupported cliff face (subject to cliff failures) by this coming austral summer.

- The second attached image shows the ICC – Reanalyzer Southern Hemisphere Surface Temp Anom forecast from April 22 to 27 2016, indicating El Nino heat telecommunication to the WAIS and also numerous cold spots in the Southern Ocean associated ice melting (which contributes directly to Hansen's ice-climate feedback mechanism).

- The third image shows Gavin Schmidt's current projection for the 12-month running average GMST anom by the end of 2016; which shows an upper projection just under 1.5C above pre-industrial (which according to the Paris Pact ambitious goal should never occur).

- Per the fourth image from Maslowski et al 2012 the Arctic sea ice voume could be close to zero in the boreal summer between 2016 & 2019; which might abruptly increase Arctic Amplification (which would both increase future GMST anomalies and which could trigger a roughly 10mm SLR contribution from the Greenland Ice Sheet in the next decade that would help to destabilize the WAIS by both raising the sea level in Antarctica and by slowing the oceanic conveyor belt).

Wieslaw Maslowski, Jaclyn Clement Kinney, Matthew Higgins, and Andrew Roberts (February 21, 2012), "The Future of Arctic Sea Ice", Annu. Rev. Earth Planet. Sci. 2012. 40:625–54, doi: 10.1146/annurev-earth-042711-105345

http://www.oc.nps.edu/NAME/Maslowski%20et%20al.%202012%20EPS%20Future%20of%20Arctic%20Sea%20Ice.pdf
« Last Edit: April 22, 2016, 11:30:39 PM by AbruptSLR »
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #502 on: April 23, 2016, 11:38:04 AM »
Rignot et al (2016) show that marine terminating glaciers in Uummannaq & Vaigat fjords West Greenland are deeper and thus more vulnerable to ocean melting than previously realized (see image), and the linked Phys. Org. article indicates that the OMG project is finding comparably over-deep bathymetry (as compared to previous bathymetries) in most other parts of Greenland's glacial fjords:

E. Rignot, I. Fenty, Y. Xu, C. Cai, I. Velicogna, C. Ó Cofaigh, J. A. Dowdeswell, W. Weinrebe, G. Catania & D. Duncan (2016), "Bathymetry data reveal glaciers vulnerable to ice-ocean interaction in Uummannaq and Vaigat glacial fjords, West Greenland", Geophysical Research Letters, DOI: 10.1002/2016GL067832


http://onlinelibrary.wiley.com/doi/10.1002/2016GL067832/abstract;jsessionid=4EC9EE456E3EBCA8359224938B13DC86.f02t01

Abstract: "Marine-terminating glaciers play a critical role in controlling Greenland's ice sheet mass balance. Their frontal margins interact vigorously with the ocean, but our understanding of this interaction is limited, in part, by a lack of bathymetry data. Here we present a multibeam echo sounding survey of 14 glacial fjords in the Uummannaq and Vaigat fjords, west Greenland, which extends from the continental shelf to the glacier fronts. The data reveal valleys with shallow sills, overdeepenings (>1300 m) from glacial erosion, and seafloor depths 100–1000 m deeper than in existing charts. Where fjords are deep enough, we detect the pervasive presence of warm, salty Atlantic Water (AW) (>2.5°C) with high melt potential, but we also find numerous glaciers grounded on shallow (<200 m) sills, standing in cold (<1°C) waters in otherwise deep fjords, i.e., with reduced melt potential. Bathymetric observations extending to the glacier fronts are critical to understand the glacier evolution."



See also:
http://phys.org/news/2016-04-greenland-glaciers.html#jCp

 
Extract: "Researchers from the University of California, Irvine; NASA's Jet Propulsion Laboratory, Pasadena, California; and other research institutions combined all observations their various groups had made during shipboard surveys of the seafloors in the Uummannaq and Vaigat fjords in west Greenland between 2007 and 2014 with related data from NASA's Operation Icebridge and the NASA/U.S. Geological Survey Landsat satellites. They used the combined data to generate comprehensive maps of the ocean floor around 14 Greenland glaciers. Their findings show that previous estimates of ocean depth in this area were as much as several thousand feet too shallow.
Why does this matter? Because glaciers that flow into the ocean melt not only from above, as they are warmed by sun and air, but from below, as they are warmed by water.
In most of the world, a deeper seafloor would not make much difference in the rate of melting, because typically ocean water is warmer near the surface and colder below. But Greenland is exactly the opposite. Surface water down to a depth of almost a thousand feet (300 meters) comes mostly from Arctic river runoff. This thick layer of frigid, fresher water is only 33 to 34 degrees Fahrenheit (1 degree Celsius). Below it is a saltier layer of warmer ocean water. This layer is currently more than more than 5 degrees F (3 degrees C) warmer than the surface layer, and climate models predict its temperature could increase another 3.6 degrees F (2 degrees C) by the end of this century.


Rignot and Fenty are co-investigators in NASA's five-year Oceans Melting Greenland (OMG) field campaign, which is creating similar charts of the seafloor for the entire Greenland coastline. Fenty said that OMG's first mapping cruise last summer found similar results. "Almost every glacier that we visited was in waters that were far, far deeper than the maps showed.""

Caption: "A comparison of the newly compiled map of the Uummannaq fjord area (left) and an older map (right). Red areas indicate shallower depths, blues and purples deeper."
“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: Hansen et al paper: 3+ meters SLR by 2100
« Reply #503 on: April 23, 2016, 06:05:28 PM »
Climate change is a "wicked problem" best interpreted using chaos theory, and in this regards, I have previously posted the attached image showing climatic trend lines with periodic strange attractors & with, and without, ratcheting quasi-static equilibrium states.  Obviously, the climatic trend line with the ratcheting quasi-static equilibrium state shows accelerated global warming.
In my prior posts where I have cited this image, I have discussed how multi-decadal feedback mechanisms such as the PDO/IPO, AMO, ENSO and bi-polar seesaw cycles can accelerate global warming via Polar Amplification & ice-climate feedback.  In this post I would like to use this image to re-iterate how recent quasi-static equilibrium states in numerous Earth Systems have biased recent scientific (e.g. AR5) projections towards lower estimates of climate sensitivity than we are about to experience in the coming several decades.  Such considerations include:

- Recent multi-decadal cycles such as the PDO/IPO/AMO have sequestered above average amounts of radiative energy into the oceans; where it is now available to not only increase water evaporation into the atmosphere, but also to melt marine & marine terminating glacial ice.

- Recent increases in CO₂ have stimulated plant growth that have accelerated the sequestering of carbon on land and in the oceans where it is available to be re-emitted back into the atmosphere due to climate change induced feedbacks like: wildfires, droughts, floods, pests, and ocean upwelling.

- Recent glacial ice melting have resulted in cold spots in both the North Atlantic, and Southern, Oceans; which have both suppressed measured GMST values and which are promoting ice-climate feedback mechanisms (ala Hansen et al 2016).

- The dissolution of the USSR occurred in Dec 1991 and was immediately followed by a reduction in the rate of increase of CH4 concentration as shown in the second attached image showing Mauna Loa's CH4 concentrations thru March 2016.  After the 2008 the rate of increase of atmospheric methane concentration accelerated (with the recovering global economy, fracking and increase in meat consumption), and due to the lag time associate with the GWP10 for methane we are only now starting to experience the temperature consequences of this acceleration of methane concentrations (note that can be thought of as a quasi-static economic equilibrium feedback mechanism for ratcheting considerations).

- The Arctic Sea Ice volume has been decreasing faster than the reduction in ASIE, resulting in a thinning of the Arctic Sea Ice.  Now that the recent/current Super El Nino has telecommunicated both heat and humidity into the Arctic, we are about to reap the consequences of decreased albedo from a darker ocean and reduce snow cover and ice-climate feedback from Greenland Ice Sheet meltwater.

Such strange attractor quasi-static equilibrium ratcheting mechanisms are not considered by the potentially higher TCR, ECS and ESS values that I have discussed previously (which could have been masked primarily by aerosols which are also being cleaned-up rapidly), but they do address why I believe that it is reasonable to take the upper end of Schmidt's GMST projection for 2016 or just below 1.5C above pre-industrial (see the third re-posed image); and also address why it is reasonable to consider that hydrofracturing could be widespread in ice shelf and coastal regions of the Western Antarctic beginning in the 2030-2040 timeframe; which would support NOAA's warning that we might experience 3m of SLR (say 2.5m from the WAIS) by 2050-2060.


See also:
http://www.marketwatch.com/(S(rnrsydaynixa5x55oiibxm45))/story/these-two-changes-in-the-ocean-are-downright-scary-2016-04-22?platform=hootsuite

Extract: "The oceans are warmer and more acidic than ever before in recorded history, and likely ever since modern humans evolved. That should worry everyone alive today.
Why? As go the oceans, so goes the health of the globe. Oceans produce more than half the oxygen we breathe, and are critical to regulating the climate. They have absorbed at least 90% of the heat from global warming since 1970, and continue to absorb 2 billion tons of carbon dioxide every year, equal to the weight of all the oil carried by supertankers annually.
This carbon dioxide makes seawater more acidic and kills off many animals that have shells, including many of the smallest animals that feed life in the ocean."

Edit: I add a fourth image of the age of the Arctic sea ice with the following caption.  This figure relates to the recent reduction in Arctic sea ice thickness:

"Arctic sea ice age for the week of March 4 - 10 from 1985 to 2016. The oldest ice--at least 5 years or older--is at its smallest level in the satellite record, representing only 3 percent of the total ice cover. Image Credit: NSIDC, courtesy University of Colorado Boulder, M. Tschudi, C. Fowler, J. Maslanik, R. Stewart, W. Meier."
« Last Edit: April 23, 2016, 07:54:27 PM by AbruptSLR »
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #504 on: April 23, 2016, 08:18:13 PM »
As a follow-up to my last post, in the linked article Robert Scribbler makes the case that: "Record Global Heat — Huge Springtime Arctic Warm-up to Crush Sea Ice, Drive Extreme Jet Stream Dip into Europe"

https://robertscribbler.com/2016/04/22/record-global-heat-huge-springtime-arctic-warm-up-to-crush-sea-ice-drive-extreme-jet-stream-dip-into-europe/

Extract: "Likely increased rates of sea ice melt, a severe blow to record low snow packs around the Arctic and a likely freakish cold air and severe weather invasion of Europe are all a result of this extreme Arctic heat playing havoc with typical weather and seasonality. By the middle of next week, temperature anomalies for the entire Arctic may rise to as high as 5 C above the already much warmer than normal 1981 to 2010 average. In such a case, we could hardly expect weather or climate conditions to be normal and there appears to be a big helping of weirdness and extreme effects coming down the pipe over the next seven days."
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #505 on: April 23, 2016, 08:28:00 PM »
The linked reference indicates that there is no substantial inter-gyre surface current pathway communicating heat from the Gulf Steam to the Subpolar Gyre associated with the North Atlantic cold spot.  I take this to indicate that the North Atlantic cold spot is relatively stable and may well become colder with continued Greenland Ice Sheet melting (thus supporting Hansen et al (2016)'s findings about ice-climate interaction):

Nicholas P. Foukal & M. Susan Lozier (2016), "No inter-gyre pathway for sea-surface temperature anomalies in the North Atlantic", Nature Communications, Volume: 7, Article number: 11333, doi:10.1038/ncomms11333


http://www.nature.com/ncomms/2016/160422/ncomms11333/full/ncomms11333.html

Abstract: "Recent Lagrangian analyses of surface drifters have questioned the existence of a surface current connecting the Gulf Stream (GS) to the subpolar gyre (SPG) and have cast doubt on the mechanism underlying an apparent pathway for sea-surface temperature (SST) anomalies between the two regions. Here we use modelled Lagrangian trajectories to determine the fate of surface GS water and satellite SST data to analyse pathways of GS SST anomalies. Our results show that only a small fraction of the surface GS water reaches the SPG, the water that does so mainly travels below the surface mixed layer, and GS SST anomalies do not propagate into the SPG on interannual timescales. Instead, the inter-gyre heat transport as part of the Atlantic Meridional Overturning Circulation must be accomplished via subsurface pathways. We conclude that the SST in the SPG cannot be predicted by tracking SST anomalies along the GS."
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #506 on: April 25, 2016, 09:47:20 PM »
The linked (open access) reference concludes that: "Future darkening is likely underestimated because of known underestimates in modelled melting (as seen in hindcasts) and because the model albedo scheme does not currently include the effects of LAI, which have a positive feedback on albedo decline through increased melting, grain growth, and darkening." (where LAI is: light-absorbing impurities).  Obviously, the indicated increase in surface ice melting in Greenland will contribute to Hansen et al (2016)'s ice-climate feedback:

Tedesco, M., Doherty, S., Fettweis, X., Alexander, P., Jeyaratnam, J., and Stroeve, J.: The darkening of the Greenland ice sheet: trends, drivers, and projections (1981–2100), The Cryosphere, 10, 477-496, doi:10.5194/tc-10-477-2016, 2016.

http://www.the-cryosphere.net/10/477/2016/

Abstract. The surface energy balance and meltwater production of the Greenland ice sheet (GrIS) are modulated by snow and ice albedo through the amount of absorbed solar radiation. Here we show, using space-borne multispectral data collected during the 3 decades from 1981 to 2012, that summertime surface albedo over the GrIS decreased at a statistically significant (99 %) rate of 0.02 decade−1 between 1996 and 2012. Over the same period, albedo modelled by the Modèle Atmosphérique Régionale (MAR) also shows a decrease, though at a lower rate ( ∼ −0.01 decade−1) than that obtained from space-borne data. We suggest that the discrepancy between modelled and measured albedo trends can be explained by the absence in the model of processes associated with the presence of light-absorbing impurities. The negative trend in observed albedo is confined to the regions of the GrIS that undergo melting in summer, with the dry-snow zone showing no trend. The period 1981–1996 also showed no statistically significant trend over the whole GrIS. Analysis of MAR outputs indicates that the observed albedo decrease is attributable to the combined effects of increased near-surface air temperatures, which enhanced melt and promoted growth in snow grain size and the expansion of bare ice areas, and to trends in light-absorbing impurities (LAI) on the snow and ice surfaces. Neither aerosol models nor in situ and remote sensing observations indicate increasing trends in LAI in the atmosphere over Greenland. Similarly, an analysis of the number of fires and BC emissions from fires points to the absence of trends for such quantities. This suggests that the apparent increase of LAI in snow and ice might be related to the exposure of a "dark band" of dirty ice and to increased consolidation of LAI at the surface with melt, not to increased aerosol deposition. Albedo projections through to the end of the century under different warming scenarios consistently point to continued darkening, with albedo anomalies averaged over the whole ice sheet lower by 0.08 in 2100 than in 2000, driven solely by a warming climate. Future darkening is likely underestimated because of known underestimates in modelled melting (as seen in hindcasts) and because the model albedo scheme does not currently include the effects of LAI, which have a positive feedback on albedo decline through increased melting, grain growth, and darkening.


See also:
http://www.climatechangenews.com/2016/03/08/darkening-greenland-ice-sheet-melts-faster/

Extract: "Over the entire ice sheet, average albedo will fall by 8% over the rest of this century, and by as much as 10% on the western edge.
Professor Tedesco thinks these are conservative estimates. Global warming will mean more precipitation. As well as the winter snow, there will be more summer rain, which would also speed up melting. As average global temperatures creep up, higher altitudes are more likely to warm and melt.
“As warming continues, the feedback from declining albedo will add up,” he says. “It’s a train running downhill, and the hill is getting steeper.”"
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #507 on: April 27, 2016, 06:12:47 PM »
The linked (open access) NAS report entitled "Attribution of Extreme Weather Events in the Context of Climate Change" fully supports (see attached images and extract) Hansen's "Storms of my Grandchildren" concerns about changing extreme weather (which will be made more intense by the ice-climate feedback):

https://nas-sites.org/americasclimatechoices/other-reports-on-climate-change/2016-2/attribution-of-extreme-weather-events-in-the-context-of-climate-change/

http://nas-sites.org/americasclimatechoices/wp-content/blogs.dir/9/files/2016/03/EEAbriefingslides.pdf

Extract: "A report from the National Academies of Sciences, Engineering, and Medicine concludes it is now possible to estimate the influence of climate change on some types of extreme events. The science of extreme event attribution has advanced rapidly in recent years, giving new insight to the ways that human-caused climate change can influence the magnitude or frequency of some extreme weather events. This report examines the current state of science of extreme weather attribution, and identifies ways to move the science forward to improve attribution capabilities.
Confidence is strongest in attributing types of extreme events that are influenced by climate change through a well-understood physical mechanism, such as, the more frequent heat waves that are closely connected to human-caused global temperature increases, the report finds. Confidence is lower for other types of events, such as hurricanes, whose relationship to climate change is more complex and less understood at present. For any extreme event, the results of attribution studies hinge on how questions about the event’s causes are posed, and on the data, modeling approaches, and statistical tools chosen for the analysis."
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #508 on: April 27, 2016, 06:56:26 PM »
The linked reference indicates that surface meltwater from Southwestern and Southeastern Greenland end up in different parts of the North Atlantic & Labrador Sea, which could help refine the projections of future climate models that include hosing from the GIS:

Hao Luo, Renato M. Castelao, Asa K. Rennermalm, Marco Tedesco, Annalisa Bracco, Patricia L. Yager & Thomas L. Mote (2016), "Oceanic transport of surface meltwater from the southern Greenland ice sheet", Nature Geoscience, doi:10.1038/ngeo2708


http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2708.html

Abstract: "The Greenland ice sheet has undergone accelerating mass losses during recent decades. Freshwater runoff from ice melt can influence fjord circulation and dynamics and the delivery of bioavailable micronutrients to the ocean. It can also have climate implications, because stratification in the adjacent Labrador Sea may influence deep convection and the strength of the Atlantic meridional overturning circulation. Yet, the fate of the meltwater in the ocean remains unclear. Here, we use a high-resolution ocean model to show that only 1–15% of the surface meltwater runoff originating from southwest Greenland is transported westwards. In contrast, up to 50–60% of the meltwater runoff originating from southeast Greenland is transported westwards into the northern Labrador Sea, leading to significant salinity and stratification anomalies far from the coast. Doubling meltwater runoff, as predicted in future climate scenarios, results in a more-than-double increase in anomalies offshore that persists further into the winter. Interannual variability in offshore export of meltwater is tightly related to variability in wind forcing. The new insight that meltwaters originating from the west and east coasts have different fates indicates that future changes in mass loss rates and surface runoff will probably impact the ocean differently, depending on their Greenland origins."
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #509 on: April 28, 2016, 01:02:43 AM »
When thinking about the implications of Hansen et al 2016, it is a good idea to have some understanding of the recent sources of radiative forcing and how they compare to radiative forcing under RCP 8.5.

The first two images regarding radiative forcing used in CMIP5 come from the linked NASA website and have the indicated caption.

http://data.giss.nasa.gov/modelforce/

Caption for first two attached image: Fig. Instantaneous radiative forcing at the tropopause (W/m2) in the E2-R NINT ensemble. (a) Individual forcings and (b) Total forcing, along with the separate sums of natural (solar, volcanic and orbital) and anthropogenic forcings. (Updated: 3/12/2016)"

The third image shows historical radiative forcing observed by NOAA for CO₂ compared with future radiative forcing for RCP 8.5.
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Laurent

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #510 on: April 28, 2016, 09:19:29 AM »
4 w/m2 ? jeeesss... that's a lot ! Where is the limit where are we heading ?

AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #511 on: April 28, 2016, 04:42:03 PM »
4 w/m2 ? jeeesss... that's a lot ! Where is the limit where are we heading ?

RCP 8.5 means 8.5 w/m2 by 2100.
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jai mitchell

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #512 on: April 28, 2016, 05:57:10 PM »
the RCP dataseries with individual component contributions of forcing for each scenario can be found here.

The data is pretty old by now and should be updated.  not sure if they will

http://www.pik-potsdam.de/~mmalte/rcps/

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #513 on: April 28, 2016, 07:27:58 PM »
4 w/m2 ? jeeesss... that's a lot ! Where is the limit where are we heading ?

If you want to play with other emission scenarios, then you can go to the following link and use the climate change calculator to consider other pathways:

http://blogs.ft.com/ftdata/2015/10/20/how-we-built-the-cop21-climate-change-calculator/
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Laurent

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #514 on: April 28, 2016, 08:15:54 PM »
Ok, that was already written in the forum but it takes time to enter my little head. Is it based on physical assumptions, that we may eventually see under estimated ? Do you know what was the value at the PETM ?

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #515 on: April 29, 2016, 03:36:41 AM »
Ok, that was already written in the forum but it takes time to enter my little head. Is it based on physical assumptions, that we may eventually see under estimated ? Do you know what was the value at the PETM ?

Laurent,

Yes, all of the RCP pathways are based on estimates/assumptions about uncertain GHG atmospheric concentration pathways and with estimates/assumptions about climate sensitivity/feedback mechanisms; and yes these assumptions may have erred on the side of least drama.  For example CO2-e in 2014 was 481ppm, which under RCP 8.5 50% CL was not expected to happen until about 2020.  Furthermore, methane emissions are currently accelerating (on a percentage basis) faster than carbon dioxide emissions; and as the linked Real Climate article indicates this will cause the radiative forcing pathway that we will follow for the next few years will at least exceed the RCP 8.5 90% to 95% pathway (see the first image showing comparable emission pathways for methane vs carbon dioxide for about 750ppm CO2-e emissions).

http://www.realclimate.org/index.php/archives/2012/01/an-online-model-of-methane-in-the-atmosphere/


The caption for the first image is: "The radiative forcings of CO2 and methane compared. The scenario is more-or-less comparable to 750 ppm CO2, as we thought."

That said, and assuming that ECS is 3C, the second image shows what might (or might not) happen in the future after 2020 if CoP21 and all assumed (but not negotiated) ratcheting phases are fully implemented.  Note that on this second, if we follow a BAU pathway (instead of CoP 21) we will be at a CO2-e of about 1250ppm by 2100; which per the third images showing paleo data (posted by yourself) is very close to the CO2 concentration during the PETM (about 55 million years ago).  Thus if the world makes a big effort we will never approach PETM conditions, but if CoP21 fails as badly as the Kyoto Protocol failed, then any one alive may experience PETM condition around 2100 (assuming that ECS is 3C; however, it may very well be between 4 to 5C).

Best,
ASLR
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #516 on: April 29, 2016, 08:31:16 AM »
By reading what you post, it seems you personally are more inclined toward assuming an ECS of 4 to 5°c, isn't it ? So what does happen at that levels ?

I note that your second figure shows 4.5°c for BAU with 910 ppm of CO2 and 1250 CO2e but my graph shows 12°c for around 1000 ppm of CO2 (what was the CO2e ? I am still waiting for the same graph but with CO2e)
« Last Edit: April 29, 2016, 08:36:51 AM by Laurent »

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #517 on: April 29, 2016, 05:22:56 PM »
To date decision makers have made poor use of preliminary climate model findings (e.g. in the 1960's President Johnson was advised of risks close to what has since occurred, but he choose to proceed with a BAU emissions pathway and to count on geoengineering as a climate fix); while the linked article (authored by people with ties to the Lawrence Berkeley National Lab, which is also working on the ACME project) discusses how climate risks identified by climate models can better be communicated (see attached image):

Jones, A., K. Calvin, and J.-F. Lamarque (2016), Climate modeling with decision makers in mind, Eos, 97, doi:10.1029/2016EO051111. Published on 27 April 2016

https://eos.org/meeting-reports/climate-modeling-with-decision-makers-in-mind

Extract: "The need for regional- and local-scale climate information is increasing rapidly as decision makers seek to anticipate and manage a variety of context-specific climate risks over the next several decades. However, global climate models are not developed with these user needs in mind, and they typically operate at resolutions that are too coarse to provide information that could be used to support regional and local decisions.
Emerging high-resolution global modeling capabilities and statistical or dynamical downscaling techniques have the potential to fill this need, but their relative strengths and weaknesses have not been systematically evaluated. Moreover, it is not clear which decision contexts require high-resolution information or how best to evaluate and communicate the degree to which relevant features of the climate are reliably represented in high-resolution data products."
« Last Edit: April 29, 2016, 05:42:01 PM by AbruptSLR »
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #518 on: April 29, 2016, 05:57:32 PM »
By reading what you post, it seems you personally are more inclined toward assuming an ECS of 4 to 5°c, isn't it ? So what does happen at that levels ?

I note that your second figure shows 4.5°c for BAU with 910 ppm of CO2 and 1250 CO2e but my graph shows 12°c for around 1000 ppm of CO2 (what was the CO2e ? I am still waiting for the same graph but with CO2e)

First, I am a little bit busy today, so I may provide more information over the coming weekend.  Nevertheless, here I point-out that your plot reflects climate response over periods of thousands to millions of years and thus: (a) the paleo CO2-e is essentially the same as CO2 concentrations (as any significant pulse of methane would convert to CO2 in relatively short period), and (b) the 12C temp would result from and Earth System Sensitivity of about 9C (see Pagani et al 2009 & the first image) rather than a ECS value.

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

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

Extract from Pagani et al 2009: "Data and modelling for the middle Pliocene (~3–3.3 Myr) indicate that the global mean temperature was 2.4–2.9 "C warmer than preindustrial conditions, and ~4 "C warmer during the early Pliocene (!4–4.2 Myr; ref. 5). If changes in carbon dioxide and associated feedbacks were the primary agents forcing climate over these timescales, and estimates of global temperatures are correct, then our results imply a very high Earth-system climate sensitivity for the middle (3.3 Myr) to early (4.2 Myr) Pliocene ranging between 7.1 ± 1.0 "C and 8.7 ± 1.3 "C per CO2 doubling, and 9.6±1.4 "C per CO2 doubling, respectively."

Caption for the first attached image: "Estimated CO2 trends considering probable oceanographic changes at each site. Each line represents a modified CO2slope for each site and the dashed green line (1012(alt)) represents an alternative nutrient scenario for Site 1012 (Supplementary Information). Vertical grey lines intersect CO2 concentrations at 3.0–3.3 and 4.0–4.2 Myr, the time intervals representing the Earth-system climate sensitivity estimates presented in the text."

Next, I attach the second image showing the GHG break-down for the RCP scenarios, for your ease of reference.

Lastly: (a) if ECS is 4.5C then for a BAU scenario the temp increase by 2100 might be around 6.75C; (b) if we add in early response of key positive Earth System feedbacks (e.g. permafrost emissions, etc.) and Hansen's ice-climate feedback then the effective ECS may be 6C (for a BAU scenario); which might give a temp increase by 2100 of about 9C; and (c) if you want to compare to the paleo data for the PETM then we should use an ESS value of about 9C, which would give an eventual (say 1000 years into the future) temp increase of about 13.5C (which roughly matches your PETM value) if we follow a BAU pathway until 2100 and then stop.
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #519 on: April 30, 2016, 06:21:21 PM »
As I am not an IGS member, I have not accessed the linked issue of the Annals of Glaciology with a theme on the: "Hydrology of glaciers and ice sheets".  While the entire issue looks interesting, I pick-out the two interrelated references cited below by Schild et al and Charalampidis et al.  These references combined highly how for tidewater glaciers (or marine terminating glaciers or marine glaciers) the dynamic interaction of the transit (& temporary accumulation) of surface meltwater can interact with warm ocean water near the ground line to promote calving (cliff failures) at a rate higher (in both Greenland and Antarctica) than currently expected by glaciologists.  If the implications of this is not clear, then I note that this increases the probability that within the next 20-years numerous marine terminating glaciers in Greenland may contribute about 10-mm of global SLR; which might result in about 14mm of abrupt RSLR in West Antarctica; which increases the probability that cliff failures & hydrofacturing of key portions of the WAIS may likely accelerate around 2035-2040 (see the Antarctic folder for background on this implications of this acceleration about this date):

Chief Editor: Alexander H. Jarosch and Ian Hewitt (2016), "Theme: Hydrology of glaciers and ice sheets", Annals of Glaciology, 57(72)


http://www.igsoc.org/annals/57/72/accepted.html

1) Subglacial hydrology at Rink Isbræ, West Greenland, inferred from sediment plume appearance
Kristin M. SCHILD, Robert L. HAWLEY, Blaine F. MORRISS

2) Thermal tracing of retained meltwater in the lower accumulation area of the southwestern Greenland ice sheet
Charalampos CHARALAMPIDIS, Dirk VAN AS, William T. COLGAN, Robert S. FAUSTO, Michael MACFERRIN, Horst MACHGUTH

See also:
https://www.washingtonpost.com/news/energy-environment/wp/2016/04/30/another-typical-day-for-greenland-scientists-find-more-reasons-it-will-melt-faster/

Extract: " The latest exhibit: New research out of Greenland conducted by Dartmouth earth sciences Ph.D. student Kristin Schild and two university colleagues — work that has just been published in the Annals of Glaciology. The study examined the 5.5-kilometer-wide Rink Glacier of West Greenland, with particular focus on how meltwater on the ice sheet’s surface actually finds its way underneath Rink, pours out in the key undersea area described above and speeds up the glacier’s melt.
It’s a feedback process that, if it plays out across many other similarly situated glaciers, could greatly worsen Greenland’s overall ice loss. “These big tidewater outlet glaciers are the ones that are contributing these huge icebergs, they’re the ones that have rapidly, rapidly sped up in the last decade,” Schild said. This makes it critically important to learn “what are the main factors…that are leading to all these fast changes,” she added.

There are nearly 200 of these large outlet glaciers overall — and as Greenland goes, Rink is fairly large in size but far from the largest. It’s less than 1 kilometer tall as it extends from the seafloor deep in a west Greenland fjord up above the surface of the water, Schild said.
That’s hardly as massive as the nearby Jakobshavn Glacier, which has a base submerged well over a kilometer below sea level — and which is sending ice out into the ocean faster than any other in Greenland. But Rink, like Jakobshavn, touches the ocean across a wide, icy front, and is grounded deep below the surface of the fjord’s waters. Here is where all the action is — including spectacular calving events, in which enormous icebergs break off, tumble into the water and eventually float out of the fjords.
There’s growing concern that warming ocean waters are snaking into these fjords at depth and lapping at the glacier bases, making such breakups more likely. It doesn’t help matters that scientists studiously mapping the fjords are finding, over and over again, that they’re deeper than previously believed, creating more opportunities for the warm ocean to trigger melting.
But the situation is even more dynamic: Amid warmer atmospheric temperatures, Greenland is also melting on its surface, a process that forms vanishing lakes, ice-banked rivers and downward channels, called moulins, that carry meltwater deep beneath the ice sheet. This water then makes its way to the bases of outlet glaciers and, after traveling through complex passageways and, perhaps, being held up or stored in icy caverns, eventually flows out from beneath them and enters the sea.

The study resulted in three separate new findings about how meltwater from Greenland’s surface is making its way under Rink Glacier and speeding its ice loss — each of which suggests that not only Rink, but other glaciers like it, could lose their ice faster than previously thought.
First of all, the satellite and time-lapse images revealed that meltwater is pouring out from beneath Rink Glacier in not just one but four separate locations. That’s bad news, because it means more overall melting of the glacier is possible. “Previously that has not been observed, to have more than one ocean location for a plume,” Schild said.
Each individual plume could be causing additional melting, Schild said. Here’s how it works: As the cold, fresh water rushes out from beneath the glacier, it cascades into ocean water that is saltier and warmer. So the cold water, being lighter, rises toward the surface hundreds of meters away — pulling the salty, warm water inward to fill the void that it leaves behind as it rises.
This doesn’t just bring more warm water toward the glacier — it does so in a turbulent way. “As it’s going up the front of the glacier, it kind of goes up in a corkscrew fashion,” Schild says. “It kind of creates a tornado as it goes up the front of this glacier, it’s bringing in that warm ocean water that then is hitting the terminus of the glacier.” This creates much more melting than would occur if the warm ocean water simply pressed steadily against the glacier front.
And that’s just one effect. The study also found that these meltwater plumes destabilize glacier fronts in another way. Over the winter in Greenland, the waters in front of glaciers develop a thick covering made up of sea ice and chunks of icebergs. This ice “melange,” as the researchers put it, freezes against the front of the glacier and acts to stabilize it.
But the meltwater plumes, the study showed, rise up early in the Greenland melt season and take chunks out of the ice melange. And no wonder — they mix with warm water as they rise to the surface, and so both their velocity and also their temperature helps break up the ice and set the stage for the glacier to start calving new icebergs.
And as if that’s not enough, the plume observations also led to yet another conclusion: There appear to be significant pockets of liquid water stored beneath Rink Glacier — water that does not freeze because of the incredible pressure that it’s under. And these pockets should also speed the glacier’s flow toward the sea — glaciers move much more rapidly atop water than they do when grinding against bedrock.
The scientists were able to infer the existence of these subglacial storage chambers based on the timing of the plumes, which continued to form more than 20 days after Greenland’s surface melting itself had ceased as summer came to a close. “As soon as it stops melting on the surface, we still see plumes up to almost a month later, coming out of the glacier,” Schild said. “And so that water is getting stuck, and it’s getting trapped underneath the glacier.”
The presumption, of course, is that while every glacier is different, similar processes could be playing out at many other glaciers besides Rink — including monsters like Jakobshavn.
If you put all these pieces together, then, you can begin to see why global warming can be so devastating to Greenland. It warms the ocean, allowing warmer seas to come visit marine glaciers — but it also warms the atmosphere, leading to melting high atop Greenland’s surface.
Each of these elements, on its own, is bad enough. But their combination is even more dastardly. In fjords at the base of glaciers, the cold water actually acts in concert with the warm to speed up total glacial loss. They’re kind of a dynamic duo."

Caption for the attached image: "Photograph of Torsukatat Avannarleq, a tidewater glacier in West Greenland, with 2 visible sediment plumes at its terminus. These plumes are made up of glacier meltwater that has traveled under the glacier, gathering eroded material, and buoyantly floated to the surface after entering the ocean. This photograph was taken in July 2014 by Adam LeWinter, US Army Corps of Engineers, Cold Regions Research and Engineering Laboratory."
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #520 on: April 30, 2016, 11:28:05 PM »
The linked reference presents both observations and modeling results that indicate that snow/ice accumulation in the upper elevations of the GIS is promoted by a local atmospheric "thermal lid"; however, there are indications that this thermal lid is beginning to leak.  If so, this would mean that prior model projections of surface ice mass loss from the GIS may well be erring on the side of least drama; and that the future acceleration of ice mass contribution to SLR will come both from accelerated calving of marine terminating glaciers and also from increasing surface ice mass loss:

M. Berkelhammer, D. C. Noone, H. C. Steen-Larsen, A. Bailey, C. J. Cox, M. S. ONeill, D. Schneider, K. Steffen, J. W. C. White. Surface-atmosphere decoupling limits accumulation at Summit, Greenland. Science Advances, 2016; 2 (4): e1501704 DOI: 10.1126/sciadv.1501704

http://advances.sciencemag.org/content/2/4/e1501704

Extract: "Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland."

See also:
http://oregonstate.edu/ua/ncs/archives/2016/apr/study-finds-limit-evaporation-ice-sheets-may-change
Extract:"Although the coastal regions of the Greenland Ice Sheet are experiencing rapid melting, a significant portion of the interior of that ice sheet has remained stable – but a new study suggests that stability may not continue.
Researchers found that very little of the snow and ice on the vast interior of the ice sheet is lost to the atmosphere through evaporation because of a strong thermal “lid” that essentially traps the moisture and returns it to the surface where it refreezes.
However, there are signs that this lid is becoming leaky as global temperatures increase. The researchers say there may be a threshold at which warming becomes sufficient to turn on a switch that will destabilize the snow surface.
Results of the study, which was funded by the National Science Foundation, are being published in Science Advances. New measurements from a research tower atop the Greenland ice sheet helped uncovered the mystery of how much snow piles up on this ice sheet.
“Normally, the air temperature goes down as you climb, but near the surface in Greenland, it gets warmer,” said David Noone, an Oregon State University professor who is an atmospheric scientist and principal investigator on the study. “The surface is very cold, but it can be as much as 20 degrees warmer just 30 to 40 feet up in the air. It’s enough that you can feel the difference between your nose and your toes.”
“The temperature difference effectively forms a lid so that there is hardly any evaporation. Warm air likes to rise, but if it is already warmer up above the air is trapped nearer the ground. One consequence is that layers of fog form from water that had recently evaporated. Eventually the small fog water-drops drift back down to the very cold surface where it refreezes onto the ice sheet.”

“Climate models suggest that as temperatures increase, more precipitation may actually fall in Greenland because warmer air can hold more water. Taken by itself, that could indicate that parts of the ice sheet may grow. However, if the lid becomes increasingly leaky, the evaporation process has become more effective and moisture will escape to the atmosphere.
“The fate of the ice sheet is in the balance,” Noone said. “It becomes a question of which influence is stronger.”"
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #521 on: April 30, 2016, 11:55:35 PM »
Laurent,
While you are kind enough to entertain the possibility of following a RCP 8.5 radiative forcing scenario; many others assume that even though we have consistently exceeded RCP 8.5 50%CL since before the scenario was published; nevertheless, this scenario must have a very unlikely probability of occurrence otherwise the IPCC would never have constructed RCP 6, 4.5 or 3/2.6.  However, the first linked article describes how the construction of RCP 4.5 and 3/2.6 (& for that matter all of the "ratcheting" phases envisioned by possible future stages of CoP21) required the use of "magical thinking" on the part of IPCC scientists who were using the tactic of “Fake it ‘til you make it”; which has proven to be an inadvisable message to pass on to decision makers.  Even if CoP21 is fully implemented (which is not certain), the best that can realistically be assumed is that RCP 6.0 may be roughly followed.  That said, the second linked article describes how America's current policy of using natural gas as an energy bridge to the future may make it very difficult for the US to meet its commitment to CoP21, even if Obama's interpretation of the Clean Air Act and if the Clean Power Plan are implemented.  The third link discussed political difficulties with fully implementing CoP21.  In my next two posts, I plan to evaluate the prospect that even if anthropogenic GHG emissions follow a CoP21/RCP 6.0 scenario that nevertheless, we might following a radiative forcing pathway that equals or exceeds RCP 8.5 50%CL until at least 2100.

Best,
ASLR

https://www.theguardian.com/science/political-science/2016/apr/26/abandon-hype-in-climate-models

Extract: "The IPCC’s own scenario database suggests that the ambition of the Paris Agreement cannot be achieved without negative emissions technologies. Even with rapid decarbonisation, there will be a need to achieve net negative emissions during the second half of this century. That objective cannot be achieved from a standing start. Well-functioning methods would need to be developed and rolled out at a rate unprecedented in human history. Yet to model what you want to happen, rather than what there is evidence could happen, is to lose the thread of reality. It is redolent of a defeated leader issuing orders to armies that have long since ceased to exist – not so much vision, as delusion.

… it is hazardous to rely on science fiction in the development of the scenarios that are used to inform policymakers. To include scenarios for avoiding dangerous climate change that employ entirely speculative approaches seems reckless in the extreme.
Some will defend the use of these technological imaginaries in IPCC scenarios by arguing that without them hopes of avoiding dangerous climate change are forlorn and that this would generate a degree of despair that would undermine the will to act.
But that is not the role of models. “Fake it ‘til you make it” may work as a tactic, but it is a lousy strategy.  As the dust settles on the Paris Agreement and policymakers face up to the challenge of achieving the ambition set out by their leaders, we need to reflect on what actually needs to happen. Policymakers can only hope to develop realistic plans, if the basis on which they are making those plans is itself realistic. While the boundary between ambition and delusion may be not be entirely sharp, the inclusion of negative emissions amounting to 600-800 billion tonnes of carbon dioxide (equivalent to 15-20 years of current annual emissions) is clearly more than a stretch goal. For this reason, negative emission techniques should be excluded from the mitigation scenarios used by the IPCC unless and until there is sufficient evidence to warrant their inclusion and then only on a scale that is demonstrably realistic.

Policymakers cannot be allowed to hide behind the vague language of the Paris Agreement (“achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases”).
In the absence of comprehensive research and indications of political feasibility, it seems prudent to exclude from the models what is currently magical thinking. Only by undertaking research will it be possible to determine whether today’s science fiction could be transformed into tomorrow’s science reality."

For the second link, see:
https://news.vice.com/article/this-could-be-one-of-the-greatest-hurdles-for-cutting-greenhouse-gas-emissions-in-the-us
Extract: "Methane emissions are among the greatest hurdles to the United States reducing its global carbon footprint.
And one of the greatest hurdles to reducing methane emissions is plugging leaks in the storage tanks, pipes, and other equipment that drillers and frackers use to extract and transport oil and gas."

For the third link, see:
http://www.commondreams.org/news/2016/04/22/global-elites-theater-paris-deal-mere-starting-point-climate-justice
« Last Edit: May 01, 2016, 12:01:31 AM by AbruptSLR »
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #522 on: May 01, 2016, 12:49:20 AM »
The first two images come from the linked Climate Interactive Scoreboard April 20 2016 evaluation of the likely increase in GMST (above pre-industrial) by 2100 following the current CoP21 pledges; which indicate roughly a 50%CL of about a 3.8C increase and about an 85% CL of about a 5C increase, assuming that ECS is 3C.  First, I note that no rational person would accept such risk given the stakes and our degree of understanding of the one-time global climate change experiment that we are currently conducting.  Second, in the "Conservative Scientists & its Consequences" thread I have presented numerous high-quality peer-reviewed references (which I will not re-post here) indicating that ECS may likely be in the 4 to 5C range; however, the impact of such a high ECS may have been masked by higher than assumed negative aerosol (& aerosol feedback) forcing, and by the multi-decadal sequestering of extra heat into the oceans during the faux hiatus.  Lastly, I provide some limited indications that these two masking phenomena are now being removed (due both to the rapid reduction in coal-fired power plants around the world and due to recent changes in multi-decadal ocean-atmosphere cycles like the PDO): (a) as indicated by the re-post of third image showing Schmidt's projection of the GMST increase through December 2016 indicating the possibility that a 1.53C increase; and (b) as the 12-month running average LOTI thru June 2015 was 1.05C this would imply a potential increase of (1.53-1.05) 0.48C by Dec 2016; however, the fourth image showing Schmidt's comparison of observed GMST (w.r.t. 1980-1999) vs his CMIP5 projection thru June 2015 shows good correlation, but when one add the 0.48C through Dec 2016 one see that we may likely exceed the 99% percentile CMIP5 projection within a few month; which indicates that the masking factors that were previously hiding the impact of having ECS be in the 4 to 5C range are now being removed and that the energy already stored in the oceans are being released and that the impacts of removing aerosols are being quickly felt (no matter what Climate Interactive projects for the current CoP21 pledges).

https://www.climateinteractive.org/programs/scoreboard/
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #523 on: May 01, 2016, 01:13:35 AM »
This is the last of three posts on the topic of why one should take the RCP 8.5 scenario seriously when evaluating Hansen et al (2016) projections.  In my last post I provided evidence that if one assumes the high end of Schmidt's GMST anom projection (based on data through the end of March 2016 while estimates of the GISS through the end of April 2016 indicate above the projected mean increase in GMST) through the end of 2016 one will be well above the 99% CL range of the CMIP5 projections that use a ECS of 3C.  While I cannot prove that we will follow the high end of Schmidt's projection (we will soon see what actually happens), if I am correct then we may well be following the curve marked RCP 8.5 (with ECS = 4.5C) in the attached image, which indicates a GMSTA of about 2C by about 2030 [again due to heat coming out of the ocean during the 20 to 30-year duration of a typical positive PDO phase, the rapid reduction of aerosols (both anthropogenic & natural) and our current dependence on methane]; which would be sufficient to trigger Hansen et al (2016)'s ice-climate feedback per DeConto & Pollard (2016) projection of WAIS ice mass loss; which would increase the effective ECS to at least 6C through 2100, and which would effective ensure that we follow the radiative forcing of RCP 8.5 through 2100 even if CoP21 pledges are strictly enforced.  However, it is possible that 8.5 watts/sq m of radiative forcing by 2100 might cause the Hadley Cell in the NH to expand to the Arctic; which then might drive the world rapidly towards a PETM type of climate with the Hadley Cell expanding in the SH to the Antarctic well before 2200.  Again, while none of this is certain, it clearly indicates that by delaying effective climate change action since the Kyoto Protocol, which have substantially increased our collective changes of tipping into a full equable climate (with an effective ECS of over 9C) largely due to our own limited psychological ability to deal effectively with uncertainty.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #524 on: May 01, 2016, 08:23:39 AM »
ASLR
Thanks so much for these posts.
The link to the Guardian article was an eye opener. I hadn't realized that 'magic' carbon sequestration was needed for their under 2 degree outcomes.
Terry

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #525 on: May 01, 2016, 10:46:40 AM »
The linked article indicates that the remaining carbon budget from 2015 may be as low as 590 GtCO2; and as CO₂-e emissions are around 50GtCO2, it is easy to see that we could readily exceed the 2C limit by around 2030 (or earlier depending on the actual ECS value); which could then trigger DeConto & Pollard (2016)'s cliff failures and hydrofracturing (most significantly in the WAIS but also meaningfully in the GIS).  Furthermore, in the way of additional positive feedbacks that Hansen did not include in his ice-climate feedback mechanism, I remind the reading that: (a) the bottom layer of marine glaciers typically contain methane hydrates that can be rapidly be decomposed as icebergs are calved & roll to the surface during cliff failures (as is frequently currently observed for the Jakobshavn Glacier); (b) as ice sheets lose large amounts of mass, isostatic rebound can raise the seafloor that was previously beneath the calved portions of marine glaciers by hundreds of meters (particularly in the Byrd Subglacial Basin area of the West Antarctic), which can destabilized methane hydrates within the raised seafloor; and (c) the multiple meters of global SLR can trigger seismic activity in coastal areas around the world, which could cause submarine landslides in the continental slope areas; which again could release methane from hydrates around the world.  Obviously, as NOAA has warned of a potential 3m global SLR between 2050-2060, these methane hydrate feedback mechanisms could possibly drive radiative forcing above the RCP 8.5 level before the end of the century, if they were to occur in combination with other potential sources of natural methane emissions from the Arctic and degrading (but periodically submerged) tropical rainforests:

Joeri Rogelj, Michiel Schaeffer, Pierre Friedlingstein, Nathan P. Gillett, Detlef P. van Vuuren, Keywan Riahi, Myles Allen & Reto Knutti (2016) "Differences between carbon budget estimates unravelled", Nature Climate Change, Volume: 6, Pages: 245–252, doi:10.1038/nclimate2868

http://www.nature.com/nclimate/journal/v6/n3/full/nclimate2868.html

Abstract: "Several methods exist to estimate the cumulative carbon emissions that would keep global warming to below a given temperature limit. Here we review estimates reported by the IPCC and the recent literature, and discuss the reasons underlying their differences. The most scientifically robust number — the carbon budget for CO2-induced warming only — is also the least relevant for real-world policy. Including all greenhouse gases and using methods based on scenarios that avoid instead of exceed a given temperature limit results in lower carbon budgets. For a >66% chance of limiting warming below the internationally agreed temperature limit of 2 °C relative to pre-industrial levels, the most appropriate carbon budget estimate is 590–1,240 GtCO2 from 2015 onwards. Variations within this range depend on the probability of staying below 2 °C and on end-of-century non-CO2 warming. Current CO2 emissions are about 40 GtCO2 yr−1, and global CO2 emissions thus have to be reduced urgently to keep within a 2 °C-compatible budget."

See also:
http://www.truthdig.com/report/item/the_worlds_carbon_budget_is_only_half_as_big_as_previously_thought_20160225

Extract: "There is general agreement that a limit of 590 billion tons would safely keep the world from overheating in ways that would impose ever greater strains on human society. The argument is about the upper limit of such estimates.
Dr Rogelj says: “In order to have a reasonable chance of keeping global warming below 2°C, we can only emit a certain amount of carbon dioxide, ever. That’s our carbon budget.
“This has been understood for about a decade, and the physics behind this concept are well understood, but many different factors can lead to carbon budgets that are either slightly smaller or slightly larger. We wanted to understand these differences, and to provide clarity on the issue for policy-makers and the public.
“This study shows that, in some cases, we have been overestimating the budget by 50 to more than 200%. At the high end, this is a difference of more than 1,000 billion tons of carbon dioxide.”"
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #526 on: May 01, 2016, 11:18:53 AM »
The linked NOAA ESRL Annual Greenhouse Gas Index (AGGI) website has now been updated in the Spring of 2016 with data through the end of 2015.  The linked data (& attached image) indicate that: (a) the 2015 radiative forcing was 2.974 watts/sq m; (b) AGGI (2015) was 1.374; and (c) CO₂-e was 485ppm.  These all indicate that in 2015 we continued on a BAU pathway:

http://www.esrl.noaa.gov/gmd/aggi/aggi.html

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #527 on: May 01, 2016, 01:21:12 PM »
ASLR
Thanks so much for these posts.

I second that. A lot of words, but with very high signal-to-noise ratio. Impressiv and scary reading.

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #528 on: May 01, 2016, 05:03:41 PM »
However, it is possible that 8.5 watts/sq m of radiative forcing by 2100 might cause the Hadley Cell in the NH to expand to the Arctic; which then might drive the world rapidly towards a PETM type of climate with the Hadley Cell expanding in the SH to the Antarctic well before 2200.

I would not be shocked to see the northern hemisphere atmospheric circulation quickly transform into a single cell in the next century. I actually believe the dramatically slowing and increasingly erratic jet stream as well as the polar cold breakouts into the mid latitudes and the huge incursions of mid latitude heat and moisture into the Arctic are emerging evidence of just how close we are to this. Once this single cell has established itself, there is no going back as the dramatic incursion of heat from the equator racing to the poles will reduce the temperature gradient so dramatically as to effectively prevent this from happening. The northern hemisphere will enter into an equable climate regime which not only means less variation in temperatures between the pole and the equator but less seasonal variation as well.

I don't however believe this will happen in the southern hemisphere for a very long time, if ever. Much of the Antarctic ice cap will be here for thousands of years. This will serve to maintain the temperature gradient from the equator to the south pole. There is actually paleoclimate evidence showing that the planet has experienced long periods where an equable climate driven by a single atmospheric cell existed in the northern hemisphere while the southern hemisphere maintained a stable three cell circulation. If I recall correctly, the evidence suggests that this has happened for a time period in excess of 10,000 years.

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #529 on: May 01, 2016, 05:50:14 PM »
However, it is possible that 8.5 watts/sq m of radiative forcing by 2100 might cause the Hadley Cell in the NH to expand to the Arctic; which then might drive the world rapidly towards a PETM type of climate with the Hadley Cell expanding in the SH to the Antarctic well before 2200.

I would not be shocked to see the northern hemisphere atmospheric circulation quickly transform into a single cell in the next century. I actually believe the dramatically slowing and increasingly erratic jet stream as well as the polar cold breakouts into the mid latitudes and the huge incursions of mid latitude heat and moisture into the Arctic are emerging evidence of just how close we are to this. Once this single cell has established itself, there is no going back as the dramatic incursion of heat from the equator racing to the poles will reduce the temperature gradient so dramatically as to effectively prevent this from happening. The northern hemisphere will enter into an equable climate regime which not only means less variation in temperatures between the pole and the equator but less seasonal variation as well.

I don't however believe this will happen in the southern hemisphere for a very long time, if ever. Much of the Antarctic ice cap will be here for thousands of years. This will serve to maintain the temperature gradient from the equator to the south pole. There is actually paleoclimate evidence showing that the planet has experienced long periods where an equable climate driven by a single atmospheric cell existed in the northern hemisphere while the southern hemisphere maintained a stable three cell circulation. If I recall correctly, the evidence suggests that this has happened for a time period in excess of 10,000 years.

Per the first linked reference/pdf, 50 million years ago was the Early Eocene when Earth had an equable climate.  The findings of Sagoo et al (2013) seem to match the second linked reference by Jagniecki et al. (2015).  Combined, these studies indicate that: (a) with enough refinements Earth Systems Models like FAMOUS may soon be able to project the modern risks of entering an equable climate (including how long it would take the SH to follow an equable atmospheric pattern given that we are forcing the environment at a rate of over ten times faster now than in the PETM); and (b) the Earth System climate Sensitivity (ESS) could be much higher than previously assumed:


Sagoo N, Valdes P, Flecker R, Gregoire LJ. (2013), "The Early Eocene equableclimate problem: can perturbations of climate model parameters identify possible solutions?", Phil Trans R Soc A 371: 20130123., http://dx.doi.org/10.1098/rsta.2013.0123

http://royalsocietypublishing.org/content/roypta/371/2001/20130123.full.pdf

Jagniecki,Elliot A. et al. (2015), "Eocene atmospheric CO2from the nahcolite proxy", Geology, http://dx.doi.org/10.1130/G36886.1


http://geology.gsapubs.org/content/early/2015/10/23/G36886.1

ftp://rock.geosociety.org/pub/reposit/2015/2015357.pdf


Abstract: "Estimates of the atmospheric concentration of CO2, [CO2]atm, for the "hothouse" climate of the early Eocene climatic optimum (EECO) vary for different proxies. Extensive beds of the mineral nahcolite (NaHCO3) in evaporite deposits of the Green River Formation, Piceance Creek Basin, Colorado, USA, previously established [CO2]atm for the EECO to be >1125 ppm by volume (ppm). Here, we present experimental data that revise the sodium carbonate mineral equilibria as a function of [CO2] and temperature. Co-precipitation of nahcolite and halite (NaCl) now establishes a well-constrained lower [CO2]atm limit of 680 ppm for the EECO. Paleotemperature estimates from leaf fossils and fluid inclusions in halite suggest an upper limit for [CO2]atm in the EECO from the nahcolite proxy of ∼1260 ppm. These data support a causal connection between elevated [CO2]atm and early Eocene global warmth, but at significantly lower [CO2]atm than previously thought, which suggests that ancient climates on Earth may have been more sensitive to a doubling of [CO2]atm than is currently assumed."

See also:
http://www.scienceworldreport.com/articles/33096/20151116/climate-change-earth-more-sensitive-carbon-dioxide-previously-thought.htm

Extract: ""Take notice that carbon dioxide 50 million years ago may not have been as high as we once thought it was. We may reach that level in the next century and so the climate change from that increase could be pretty severe, pretty dramatic. CO2 and other climate forcings may be more important for global warming than we realized."
The findings reveal that carbon dioxide may be more potent than we first expected. This could have major implications for future climate warming as carbon dioxide levels continue to rise over time."
« Last Edit: May 01, 2016, 06:08:31 PM by AbruptSLR »
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #530 on: May 01, 2016, 06:03:09 PM »
ASLR
Thanks so much for these posts.

I second that. A lot of words, but with very high signal-to-noise ratio. Impressiv and scary reading.

Thank you, & Terry, for taking the time to read so many words.  The real question is when/whether [in time for AR6 projections?] the IPCC will update their radiative forcing scenarios to include not only the numerous feedback mechanisms that they ignored as discussed in Bodman et al (2016) [which projected higher values of GMST, with wider ranges of uncertainty, as illustrated by the attached plot with the caption cited below], but also such considerations as: (a) studies indicating higher values of TCR & ECS; (b) Hansen's ice-climate feedback; (c) the higher world's population forecasts; (d) the heat energy stored in the oceans during the recent faux hiatus; (e) potentially higher negative forcing & feedbacks for anthropogenic & natural aerosols; (f) the recent surge in methane emissions and the fact that CO2-e was at 485ppm at the end of 2015, which exceeds RCP 8.5 90%CL radiative forcing levels; (g) the potential future release (by soil microbes) of carbon currently being sequestered into the soil by the recent surge in CO2-driven plant growth; etc.

Bodman, R. W., Rayner, P. J. and Jones, R. N. (2016), "How do carbon cycle uncertainties affect IPCC temperature projections?",  Atmosph. Sci. Lett., doi: 10.1002/asl.648

http://onlinelibrary.wiley.com/doi/10.1002/asl.648/abstract

Abstract: "Carbon cycle uncertainties associated with the Intergovernmental Panel on Climate Change temperature-change projections were treated differently between the Fourth and Fifth Assessment Reports as the latter focused on concentration- rather than emission-driven experiments. Carbon cycle feedbacks then relate to the emissions consistent with a particular concentration. A valuable alternative is to include all uncertainties in a single step from emissions to temperatures. We use a simple climate model with an observationally constrained parameter distribution to explore the carbon cycle and temperature-change projections, simulating the emission-driven Representative Concentration Pathways. The resulting range of uncertainty is a somewhat wider and asymmetric likely range (biased high)."

Caption: "Plume plots for ΔGMT change projections 2000–2100, ∘C relative to 1986–2005. MAGICC results with carbon cycle temperature feedbacks on (CC-on) and switched off (CC-off) (a) RCP2.6, (b) RCP4.5, (c) RCP6.0 and (d) RCP8.5. Shaded regions indicate the 67% confidence interval for CC-on (green) and CC-off (blue), with median results as solid green and dashed blue lines, respectively."
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #531 on: May 01, 2016, 07:09:18 PM »
While I very much appreciate the techniques cited in the linked article w.r.t. expert judgement and the quantification of uncertainty for climate change projections; nevertheless, I note that Michael Oppenheimer is one of the IPCC old guard who are prone to both "magical thinking" and erring of the side of least drama, as can readily be seen by the two attached images associated with the authors efforts to quantify the uncertainty of Antarctic contribution to future sea level rise; which totally ignores Hansen et al (2016)'s ice-climate feedback and DeConto & Pollard (2016)'s cliff failures and hydrofracturing.  Oppenheimer's "Fake it 'til you make it" approach to catering to policy makers desires will potentially result in trillions of dollars of worldwide property losses if NOAA is correct that sea levels might rise by up to 3m by 2050-2060, and this consideration is ignored by the statistical approaches used by Oppenheimer et al.  It is important to realize that statistical techniques should not supersede physics (say calibrated to paleo findings ala DeConto & Pollard) when making projections suitable for policy making (i.e. get the physic right first and then apply the statics):

Michael Oppenheimer, Christopher M. Little & Roger M. Cooke (2016), "Expert judgement and uncertainty quantification for climate change", Nature Climate Change, Volume: 6, Pages: 445–451, DOI: 10.1038/nclimate2959


http://www.nature.com/nclimate/journal/v6/n5/full/nclimate2959.html

Abstract: "Expert judgement is an unavoidable element of the process-based numerical models used for climate change projections, and the statistical approaches used to characterize uncertainty across model ensembles. Here, we highlight the need for formalized approaches to unifying numerical modelling with expert judgement in order to facilitate characterization of uncertainty in a reproducible, consistent and transparent fashion. As an example, we use probabilistic inversion, a well-established technique used in many other applications outside of climate change, to fuse two recent analyses of twenty-first century Antarctic ice loss. Probabilistic inversion is but one of many possible approaches to formalizing the role of expert judgement, and the Antarctic ice sheet is only one possible climate-related application. We recommend indicators or signposts that characterize successful science-based uncertainty quantification."

See also:
http://phys.org/news/2016-04-tool-experts-uncertainty-climate.html

Extract: "Science can flourish when experts disagree, but in the governmental realm uncertainty can lead to inadequate policy and preparedness. When it comes to climate change, it can be OK for computational models to differ on what future sea levels will be. The same flexibility does not exist for determining the height of a seawall needed to protect people from devastating floods.
For the first time in the climate field, a Princeton University researcher and collaborators have combined two techniques long used in fields where uncertainty is coupled with a crucial need for accurate risk-assessment—such as nuclear energy—in order to bridge the gap between projections of Earth's future climate and the need to prepare for it. Reported in the journal Nature Climate Change, the resulting method consolidates climate models and the range of opinions that leading scientists have about them into a single, consistent set of probabilities for future sea-level rise.
"Scientists working in climate change know that the models used throughout climate research have shortcomings. At the same time policymakers need to know the future of sea-level rise, and they need as robust a prediction as we can give," said Michael Oppenheimer, Princeton's Albert G. Milbank Professor of Geosciences and International Affairs and the Princeton Environmental Institute and first author of the paper."
« Last Edit: May 01, 2016, 07:14:59 PM by AbruptSLR »
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #532 on: May 02, 2016, 07:33:51 PM »
The linked reference confirms my belief that too much "magical thinking" (including "Fake it 'til you make it" actions by IPCC contributing scientists, like Oppenheimer et al 2016's estimates of  ice sheet mass contribution to SLR), ESDL by mainstream climate scientists and Polyannaish Happy Talk by the media is slowing the fight again climate change.  James Hansen has been correct that scientist should overcome their reticence to acknowledge that the current pathway that society is following is dangerous and that active steps (like carbon pricing & regulations & investment in sustainable energy research) needs to be taken quickly:

Matthew J. Hornsey & Kelly S. Fielding (2016), "A cautionary note about messages of hope: Focusing on progress in reducing carbon emissions weakens mitigation motivation", Global Environmental Change, Volume 39 , Pages 26–34, doi:10.1016/j.gloenvcha.2016.04.003

http://www.sciencedirect.com/science/article/pii/S0959378016300450

Abstract: "For the first time this millennium, growth in carbon emissions has slowed. Indeed, the year 2014 was the first time in 40 years that the planet saw zero growth in emissions. We examine whether this message of progress can be effective in motivating people to engage in mitigation efforts. This question dovetails with commentary suggesting that gloomy messages about climate change risk fatiguing the population, and that alternative approaches are necessary. It is also informed by work suggesting that hope is a motivating force in terms of engaging in collective action and social change. Study 1 (N = 574) showed that negative emotions were strongly related to mitigation motivation and feelings of efficacy, but hope-related emotions had a much weaker relationship with these constructs. In the main experiment (Study 2: N = 431) participants read an optimistic, pessimistic, or neutral message about the rate of progress in reducing global carbon emissions. Relative to the pessimistic message, the optimistic message reduced participants’ sense that climate change represented a risk to them, and the associated feelings of distress. Consequently, the optimistic message was less successful in increasing mitigation motivation than the pessimistic message. In sum, predictions that the optimistic message would increase efficacy did not transpire; concerns that the optimistic message would increase complacency did transpire. Recent progress in curbing global carbon emissions is welcome, but we found no evidence that messages focusing on this progress constitute an effective communication strategy."
« Last Edit: May 02, 2016, 09:24:52 PM by AbruptSLR »
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #533 on: May 02, 2016, 08:05:19 PM »
The linked reference discusses the relationship of ECS and dynamical sensitivity of climate models.  With Hansen et al (2016), observation that ice sheet melting can temporarily reduce SSTA in the Southern Ocean and North Atlantic, it is important to consider parameters such a dynamical sensitivity and Earth Energy Imbalance (EEI):

Kevin M. Grise & Lorenzo M. Polvani (28 April 2016), "Is climate sensitivity related to dynamical sensitivity?", Journal of Geophysical Research Atmospheres, DOI: 10.1002/2015JD024687


http://onlinelibrary.wiley.com/doi/10.1002/2015JD024687/abstract

Abstract: "The atmospheric response to increasing CO2 concentrations is often described in terms of the equilibrium climate sensitivity (ECS). Yet, the response to CO2 forcing in global climate models is not limited to an increase in global-mean surface temperature: for example, the mid-latitude jets shift poleward, the Hadley circulation expands, and the subtropical dry zones are altered. These changes, which are referred to here as “dynamical sensitivity,” may be more important in practice than the global-mean surface temperature.
This study examines to what degree the inter-model spread in the dynamical sensitivity of 23 CMIP5 models is captured by ECS. In the Southern Hemisphere, inter-model differences in the value of ECS explain ~60% of the inter-model variance in the annual-mean Hadley cell expansion, but just ~20% of the variance in the annual-mean mid-latitude jet response. In the Northern Hemisphere (NH), models with larger values of ECS significantly expand the Hadley circulation more during winter months, but contract the Hadley circulation more during summer months. Inter-model differences in ECS provide little significant information about the behavior of the Northern Hemisphere subtropical dry zones or mid-latitude jets.
The components of dynamical sensitivity correlated with ECS appear to be driven largely by increasing sea surface temperatures, whereas the components of dynamical sensitivity independent of ECS are related in part to changes in surface temperature gradients. These results suggest that efforts to narrow the spread in dynamical sensitivity across global climate models must also consider factors that are independent of global-mean surface temperature."
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #534 on: May 05, 2016, 05:58:57 PM »
The linked article provides a nice summary of recent thinking on the risk of abrupt sea level rise, and the implications of such risk ala Hansen et al 2016:

http://e360.yale.edu/feature/abrupt_sea_level_rise_realistic_greenland_antarctica/2990/

Extract: "Turning their model to the future, DeConto and Pollard project more than three feet of sea level rise from Antarctica alone by 2100 — assuming growing greenhouse gas emissions that boost the planet’s temperature by about 4 degrees C (7 degrees F). That is far more than the last IPCC estimate in 2013, which projected less than eight inches of sea level rise from a melting Antarctic by 2100, with a possibility for inches more from the dramatic collapse of Antarctic glaciers.

Even DeConto admits that, under the model used in his paper, the timing and pace of Antarctica’s ice loss is “really uncertain” — it could be a decade or two, or three or four, before these dramatic processes start to kick in, he says. “The paper just shows the potentials, which are really big and really scary,” says DeConto. But Scambos and other observers call DeConto’s numbers “perfectly plausible.”"
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #535 on: May 06, 2016, 11:40:05 PM »
The linked reference finds that the influence of the continental shelf bathymetry predisposes the Antarctic Ice Sheet to gradual advance, and abrupt retreat, of ice grounding lines in response to changes in climate forcing:

Dan Mullally, Philip J. Bart & Nicholas Golledge (2016), "The influence of continental shelf bathymetry on Antarctic Ice Sheet response to climate forcing", Global and Planetary Change


http://www.sciencedirect.com/science/article/pii/S0921818115300916


Abstract: "We investigated whether shelf-depth changes would have influenced Antarctic Ice Sheet (AIS) response to climate forcing using the Parallel Ice Sheet Model (PISM). The simulations confirm that this would have indeed been the case. For the last-glacial-cycle (LGC) type forcing we prescribed, a modern-like polar AIS surrounded by shallow and intermediate bathymetries experiences rapid grounding-line advance early during the transition from interglacial to glacial forcing. This is in contrast to our baseline simulation of AIS response on the currently overdeepened bathymetry, which showed the expected gradual advance of grounding lines to the same climatic forcing. In the simulation, the more-positive mass balance for the shallower bathymetry is primarily a result of significantly lower calving fluxes from smaller-area ice shelves. On the basis of these results, we suggest that shelf bathymetry is an important boundary condition that should be considered when reconstructing AIS behavior since at least the middle Miocene. We note that caution should be used when applying these concepts because the particular way in which AIS mass balance is altered by shelf depth changes depends on how the changes in accumulation and ablation at the marine terminations combine with accumulation and ablation on land."
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #536 on: May 09, 2016, 06:02:58 PM »
First, the linked first reference finds that the recently observed increase in freshwater (ice meltwater) flux into the Southern Ocean leads to:
(a) a decrease in upper-ocean temperature,
(b) an increase in sea ice formation, and
(c) a decrease in AABW formation.

These findings all confirm the ice-climate feedback mechanism identified by Hansen et al 2016:

Kate Snow, Andrew McC. Hogg, Bernadette M. Sloyan and Stephanie M. Downes (2016), "Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes", Journal of Climate, DOI: http://dx.doi.org/10.1175/JCLI-D-15-0467.1


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0467.1

Abstract: "The influence of freshwater and heat flux changes on Antarctic Bottom Water (AABW) properties are investigated within a realistic bathymetry coupled ocean–ice sector model of the Atlantic Ocean. The model simulations are conducted at eddy-permitting resolution where dense shelf water production dominates over open ocean convection in forming AABW. Freshwater and heat flux perturbations are applied independently and have contradictory surface responses, with increased upper-ocean temperature and reduced ice formation under heating and the opposite under increased freshwater fluxes. AABW transport into the abyssal ocean reduces under both flux changes, with the reduction in transport being proportional to the net buoyancy flux anomaly south of 60°S.
Through inclusion of shelf-sourced AABW, a process absent from most current generation climate models, cooling and freshening of dense source water is facilitated via reduced on-shelf/off-shelf exchange flow. Such cooling is propagated to the abyssal ocean, while compensating warming in the deep ocean under heating introduces a decadal-scale variability of the abyssal water masses. This study emphasizes the fundamental role buoyancy plays in controlling AABW, as well as the importance of the inclusion of shelf-sourced AABW within climate models in order to attain the complete spectrum of possible climate change responses."

Second, per the following linked peer reviewed reference Pauling et al (2016): "The freshwater flux from ice sheet and ice shelf mass imbalance is largely missing in models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5). However, on average, precipitation minus evaporation (P − E) reaching the Southern Ocean has increased in CMIP5 models to a present value that is about 2600 Gt/yr greater than preindustrial times and 5–22 times larger than estimates of the mass imbalance of Antarctic ice sheets and shelves (119–544 Gt/yr)."

http://journals.ametsoc.org/doi/10.1175/JCLI-D-15-0501.1

Finally, I provide the following comparison between the Global, NH & SH temperature departure values for: (a) the 2015 Mean values, (b) the approximate force adjusted CMIP5 2016 RCP 8.5 (and 95% CL range) and (c) the Jan./Feb./March 2016 12-month running average GISS temp departures (from 1951-1980).  This data shows that as compared to the RCP 8.5 CMIP5 2016 average mean value the March 2016 12-month running average is running hot in the NH, and cold in the SH, as would be expected if Hansen et al 2016 are correct and Antarctic glacial ice melting is cooling the air temperature 2m above the Southern Ocean. 

GISS Land & Ocean Temp Departure degrees Celsius, base period: 1951-1980

Year                              Global        NHem              SHem
2015 Mean   :                   0.86           1.13                0.60 
2016 RCP 8.5/CMIP5:       0.85            1.05              0.65
RCP 8.5 95% CL Range:  (0.5–1.2)     (0.6–1.5)         (0.3–1.0)

12-mo.running ave.
March 2016:                    0.90             1.27               0.61
Febr. 2016:                     0.87               1.22              0.60
Jan. 2016:                       0.83              1.16               0.58

(The concert 1951-1980 temp departures to pre-industrial add: + 0.256 Celsius)
« Last Edit: May 09, 2016, 06:27:34 PM by AbruptSLR »
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #537 on: May 09, 2016, 09:11:25 PM »
As I previously explained, when extrapolating the abrupt growth in ice sheet mass loss, it is important to sub-divide then source of ice mass loss first before extrapolating (and then to re-aggregate the various sources).  To this end the Technische Universitaet Dresden provides the following very useful website that documents Antarctic Ice Sheet mass change per the GRACE satellite, as updated every month.  The first image shows the spatial distribution of ice mass loss (from 2002-2008 thru Jan 2016) across Antarctica.  The second image provides a key to the GRACE mass change basins, from which it can be seen that for the WAIS ice mass loss comes primarily from basins 20, 21, 22 and 23 (which will be detailed in my next post).

Technische Universitaet Dresden,
Gravimetric mass balance: Antarctic Ice Sheet project ESA Climate Change Initiative

https://data1.geo.tu-dresden.de/ais_gmb/

See also:
https://www.sciencedaily.com/releases/2016/05/160509085744.htm

Extract: "The Antarctic ice sheet, with a thickness of up to 4800 meter, has lost mass in the recent years. This was confirmed by a variety of scientific studies. Scientists now visualize the ice-mass loss: The interested public and scientific community can follow the Antarctic ice-mass changes month by month and divided by regions."
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #538 on: May 09, 2016, 09:15:32 PM »
The four attached plots from Dresden detail the cumulative (from August 16 2002 to Jan 16 2016) ice mass loss from the AIS basins 20, 21, 22 and 23.  These are all basins to watch to see whether ice mass loss from these areas increase non-linearly as/when GMST departures exceed 2C above pre-industrial:
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #539 on: May 10, 2016, 05:06:23 PM »
In my opinion, the most likely reason that NOAA warned the insurance industry that the world might experience up to 3m of SLR in the 2050-2060 timeframe, is that their coupled oceanic-atmospheric model for the Southern Ocean may be showing that the upwelling of warm deep water into the Amundsen Sea Embayment, ASE, (& adjoining areas) induced by local ice-climate interaction is already occurring (while the first attached image from Fogwill et al (2015) shows model projections the impact after about 100-years of such hosing).  My two immediately prior posts show that the GRACE satellite confirms substantial sustaining land-based ice melting is occurring in this area and to this land-based ice melt one needs to add ice melt from local ice-shelf basal melting as indicated in the second attached image.  The third attached image shows a hydraulic model projection of the deep (700m deep) water temperature (left panel) and the associated water velocities in the ASE area; which indicates that once this water deep water melts the glacial ice in this area the associated freshwater floats near the surface and is advected westward towards the Ross Sea where the fourth image shows generates significant amounts of sea ice (which inhibits polyana formation, which inhibits AABW formation, which slows the thermohaline circulation; which is a clear ice-climate positive feedback ala Hansen et al 2016).  In my next post, I will post some circumstantial evidence that this projected upwelling of warm deep water into the ASE (& adjoining regions) may already be occurring and may promote the occurrence of local cliff failures and hydrofracturing in the timeframe postulated by NOAA.





C. J. Fogwill, S. J. Phipps, C. S. M. Turney & N. R. Golledge (2015), "Sensitivity of the Southern Ocean to enhanced regional Antarctic ice sheet meltwater input", Earth's Future, Volume 3, Issue 10, Pages 317–329, DOI: 10.1002/2015EF000306

http://onlinelibrary.wiley.com/doi/10.1002/2015EF000306/full

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #540 on: May 10, 2016, 05:25:27 PM »
As a follow-up to my last post: (a) the first image shows that the 2m air temp anom offshore of the Amundsen Sea Embayment, ASE, is warmer than usual; while the temp anom offshore of the Ross Ice Shelf is atypically cool; which might mean that warm deep water is upwelling into the ASE which is displacing fresh meltwater into the Ross Sea where (b) it is making extra sea ice as indicated in the second attached image; and (c) is suppressing Antarctic Bottom Water, AABW, formation which then slows the input into the thermohaline circulation as shown in the third attached image (which is an ice-climate positive feedback ala Hansen et al 2016).
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #541 on: May 10, 2016, 08:43:41 PM »
Here is a gif I made of the area mentioned by ASLR from Apr 27 to May 9.  I left it full size because the changes are quite subtle with the large area shown.

Originals:
http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20160509T051611_882F_S_1.final.jpg

and S1A_EW_GRDM_1SSH_20160427T051610_E96B_S_1.final
FNORD

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #542 on: May 10, 2016, 09:26:12 PM »
Here is a gif I made of the area mentioned by ASLR from Apr 27 to May 9.  I left it full size because the changes are quite subtle with the large area shown.

If it is not obvious from the image, all of the floating ice/icebergs are melting from below the waterline and thus are contributing to ice-climate feedback even if they are not contributing to sea level rise.
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #543 on: May 10, 2016, 09:53:39 PM »
With regard to East Antarctic ice mass changes, I would like to point out that most of the mass gain in East Antarctica occurred during a very unusual series of atmospheric river events from 2010 thru 2012; which may not re-occur for many decades; while the ice mass loss due to calving in Basins AIS 13, AIS 14 and AIS 15 (see attached images, respectively) will likely continue to accelerate with continuing global warming (& ocean warming) as indicated by DeConto & Pollard 2016.
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #544 on: May 11, 2016, 04:37:05 PM »
As a follow-up to the statement in my last post that most of the mass gain in East Antarctica was due to a series of relatively rare atmospheric river events; the authors of the linked reference about atmospheric river events in Antarctica found that:

(a) The nine atmospheric rivers that hit East Antarctica between 2009 and 2011 accounted for 80 per cent of the exceptional snow accumulation at Princess Elisabeth station; and
(b) "The unusually high snow accumulation in Dronning Maud Land in 2009 that we attributed to atmospheric rivers added around 200 gigatons of mass to Antarctica, which alone offset 15 per cent of the recent 20-year ice sheet mass loss," see the attach image and associated caption below.

Also, I point-out:
 
(a) First, that atmospheric river events have been historically rare and to have nine such events hit Dronning Maud Land between 2009 and 2011 indicates that extreme weather is becoming more common in the Southern Ocean; and
(b) Second, as global warming continues future atmospheric events may more frequenctly drop rain instead of snow on Antarctica; which would be a positive feedback for ice mass loss & SLR:

Finally, I point-out that modeling such future atmospheric river events represents a significant challenge for regional modelers to get right:

Gorodetskaya, I. V., M. Tsukernik, K. Claes, M. F. Ralph, W. D. Neff, and N. P. M. Van Lipzig, (2014), "The role of atmospheric rivers in anomalous snow accumulation in East Antarctica", Geophys. Res. Lett., 41, 6199–6206, doi:10.1002/2014GL060881.


http://onlinelibrary.wiley.com/doi/10.1002/2014GL060881/abstract
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #545 on: May 11, 2016, 04:50:48 PM »
If Hansen et al (2016)'s ice-climate feedback mechanism is correct then one would expect to observe a contraction of AABW in the Southern Ocean, and this is precisely what Purkey et al (2012) show in the linked paper; which also indicates that the changes in AABW formation change the patterns of the circumpolar deep water, CDW as indicated in the attached image (in a manner that draws this warm CDW closer to several critical Antarctic marine glaciers).

SARAH G. PURKEY and GREGORY C. JOHNSON (2012) "Global contraction of Antarctic Bottom Water between the 1980s and 2000s", Climate Journal

http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-11-00612.1
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #546 on: May 12, 2016, 08:43:18 PM »
The linked reference confirms that most (67 to 98%) of the Earth's Energy Imbalance, EEI, is going into the Southern Hemisphere extratropical ocean; however, the attached image showing Karsten Haustein's global surface air temp anom forecast from May 12 to 19 2016, indicates that the surface temperatures in the SH are atypically low which probably indicates that ice meltwater is cooling the surface of the Southern Ocean as projected by Hansen et al 2016.

Dean Roemmich, John Church, John Gilson, Didier Monselesan, Philip Sutton & Susan Wijffels (2015), "Unabated planetary warming and its ocean structure since 2006", Nature Climate Change, Volume: 5, Pages: 240–245, doi:10.1038/nclimate2513

http://www.nature.com/nclimate/journal/v5/n3/full/nclimate2513.html

Abstract: "Increasing heat content of the global ocean dominates the energy imbalance in the climate system. Here we show that ocean heat gain over the 0–2,000 m layer continued at a rate of 0.4–0.6 W m−2 during 2006–2013. The depth dependence and spatial structure of temperature changes are described on the basis of the Argo Program's accurate and spatially homogeneous data set, through comparison of three Argo-only analyses. Heat gain was divided equally between upper ocean, 0–500 m and 500–2,000 m components. Surface temperature and upper 100 m heat content tracked interannual El Niño/Southern Oscillation fluctuations, but were offset by opposing variability from 100–500 m. The net 0–500 m global average temperature warmed by 0.005 °C yr−1. Between 500 and 2,000 m steadier warming averaged 0.002 °C yr−1 with a broad intermediate-depth maximum between 700 and 1,400 m. Most of the heat gain (67 to 98%) occurred in the Southern Hemisphere extratropical ocean. Although this hemispheric asymmetry is consistent with inhomogeneity of radiative forcing4 and the greater area of the Southern Hemisphere ocean, ocean dynamics also influence regional patterns of heat gain."
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #547 on: May 13, 2016, 12:25:08 AM »
I note that currently essentially no aspect of Hansen et al (2016) is recognized as a risk for this century by the IPCC.  Unfortunately, almost all responsible civil authorities look to the IPCC for guidance on adaptation requirements.  So unless a lot of peer reviewed references are published by 2018, per the linked IPCC schedule the ice-climate feedback documented by Hansen et al (2016) will not be recognized by AR6, and thus would likely need to wait until about 2027 before being recognized.  However, preparations to deal with abrupt sea level rise would require at least 30-years of advance notice, so if NOAA's worse case of 3m of SLR by 2050 were to occur; all nations (including the most modern nations) could not prepare adequate adaptive measures:

http://www.ictsd.org/bridges-news/biores/news/ipcc-sets-plans-for-next-major-report-cycle-15-degree-study

Extract: "The IPCC also set out the next steps and timeframe for releasing its “Sixth Assessment Report,” or AR6 – particularly in relationship to the expected entry into force of the Paris Agreement.

The IPCC releases a special report every six to seven years which assesses the state of the climate and the effect that manmade actions have in this area. The previous IPCC report, AR5, was issued in 2014 and called for a 40-70 percent emissions cut over the next four decades, compared to 2010 levels, with a view to reaching zero by century’s end to ward off the worst effects of climate change. (See Bridges Weekly, 6 November 2014)

The newest report will be released in stages, according to the IPCC. Three working group reports on topics surrounding physical science, adaptation, and mitigation will be published between 2020 and 2021, with the synthesis report linking all three areas being published in 2022."
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AbruptSLR

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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #548 on: May 17, 2016, 05:58:44 PM »
In view of the importance of real-time monitoring of Earth's Energy Imbalance (with regards to Hansen et al (2016)'s ice-climate feedback), I provide the linked (open access) reference by Trenberth et al (2014) on this topic:

KEVIN E. TRENBERTH, JOHN T. FASULLO & MAGDALENA A. BALMASEDA (2014), "Earth’s Energy Imbalance", Journal of Climate; DOI: 10.1175/JCLI-D-13-00294.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00294.1

http://www.cgd.ucar.edu/staff/trenbert/trenberth.papers/T_F_B_energyImb_JCLI_14.pdf

Abstract: "Climate change from increased greenhouse gases arises from a global energy imbalance at the top of the atmosphere (TOA). TOA measurements of radiation from space can track changes over time but lack absolute accuracy. An inventory of energy storage changes shows that over 90% of the imbalance is manifested as a rise in ocean heat content (OHC). Data from the Ocean Reanalysis System, version 4 (ORAS4), and other OHC-estimated rates of change are used to compare with model-based estimates of TOA energy imbalance [from the Community Climate System Model, version 4 (CCSM4)] and with TOA satellite measurements for the year 2000 onward. Most ocean-only OHC analyses extend to only 700-m depth, have large discrepancies among the rates of change of OHC, and do not resolve interannual variability adequately to capture ENSO and volcanic eruption effects, all aspects that are improved with assimilation of multivariate data. ORAS4 rates of change of OHC quantitatively agree with the radiative forcing estimates of impacts of the three major volcanic eruptions since 1960 (Mt. Agung, 1963; El Chich_on, 1982; and Mt. Pinatubo, 1991). The natural variability of the energy imbalance is substantial from month to month, associated with cloud and weather variations, and interannually mainly associated with ENSO, while the sun affects 15% of the climate change signal on decadal time scales. All estimates (OHC and TOA) show that over the past decade the energy imbalance ranges between about 0.5 and 1Wm22. By using the full-depth ocean, there is a better overall accounting for energy, but discrepancies remain at interannual time scales between OHC- and TOA-based estimates, notably in 2008/09."

Edit: The attached image from Trenberth et al 2014 shows that the trend line for the net TOA radiation has been positive since the 1960's, but I am concerned that with ice-climate interaction and with a reduction in aerosol emissions (and if GHG, with high GWP, emissions remain high) that these values could likely become still more positive relatively soon.
« Last Edit: May 17, 2016, 07:07:57 PM by AbruptSLR »
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Re: Hansen et al paper: 3+ meters SLR by 2100
« Reply #549 on: May 17, 2016, 10:09:57 PM »
The linked Aquarius satellite data provides various maps of observed data, such as the attached image of the sea surface density for April 2015, indicating how fresh both the North Atlantic and the Southern Ocean are becoming relative to the other oceans of the world; which is a clear sign that the Hansen et al (2016) ice-climate feedback mechanism has already begun:

http://aquarius.umaine.edu/cgi/gal_density.htm

http://aquarius.umaine.edu/cgi/gal_latitudes_sss.htm

http://aquarius.umaine.edu/cgi/gal_salinity.htm
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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