Conservative Scientists & its Consequences

[AbruptSLR]

The 2017 AGU Fall Meeting will host a session (ID#: 23637) entitled: "Climate Sensitivity and Feedbacks: Advances and New Paradigms".  Hopefully, new paradigms will allow climate scientists to narrow the rather large range of 1.5 to 4.5 C give for ECS in AR5:

https://agu.confex.com/agu/fm17/preliminaryview.cgi/Session23637

Session description: "A major goal of current climate research is to reduce uncertainty in metrics of large-scale forced climate responses, such as the Equilibrium Climate Sensitivity of temperature (ECS). The ECS is estimated at 1.5—4.5 K, a range largely due to clouds and other moist processes. These processes are deeply intertwined and are linked to changes in societally important factors such as precipitation. This session explores recent advances in understanding large-scale climate response to climate forcings. We welcome submissions on theory, observations and modelling studies of climate feedbacks, climate sensitivity, and climate responses of precipitation and large-scale dynamics, especially those exploring novel evaluation techniques, and new ways of thinking about processes that govern climate's response to external forcing."

The current list of submitted abstracts for this session are as follows:

Radiative Effects of the Diurnal Cycle of Clouds and their Response to Climate Change (216076)
Jun Yin, Duke University, Durham, NC, United States and Amilcare M Porporato, Duke Univ, Durham, NC, United States

An assessment of tropospheric water vapor feedback using radiative kernels (218133)
Run Liu1, Hui Su2, Kuo-Nan Liou3, Jonathan H. Jiang2, Yu Gu3 and Shaw Chen Liu4, (1)Jinan University, Guangzhou, China, (2)Jet Propulsion Lab, Pasadena, CA, United States, (3)Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, United States, (4)Academia Sinica, Taipei, Taiwan

Relationships between lower tropospheric stability, low cloud cover, and water vapor isotopic composition in the subtropical Pacific (222065)
Joseph Galewsky, University of New Mexico Main Campus, Albuquerque, NM, United States

Low cloud feedback from A-Train sensors using the observation-based cloud radiative kernels (226729)
Qing Yue1, Eric J Fetzer2, Brian H Kahn3, Matthew D Lebsock1, Sun Wong4, Chen Zhou5 and Tao Wang4, (1)Jet Propulsion Laboratory, Pasadena, CA, United States, (2)Jet Propulsion Lab, Pasadena, CA, United States, (3)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (4)JPL / Caltech, Pasadena, CA, United States, (5)Lawrence Livermore National Laboratory, Livermore, CA, United States

Mean Precipitation Change From Invariant Radiative Cooling (227569)
Nadir Jeevanjee, Princeton University, Princeton, NJ, United States and David M Romps, University of California Berkeley, Berkeley, CA, United States

Relationship between changes in the upper and lower tropospheric water vapor: A revisit (232809)
Mengmiao Yang, Department of Earth System Science, Tsinghua University, Beijing, China, De-Zheng Sun, Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO, United States and Guang Jun Zhang, Scripps Institution of Oceanography, La Jolla, CA, United States

How large is Uncertainty in Calibrated Perturbed Physics Ensembles? (235205)
Simon FB Tett, University of Edinburgh, School of GeoSciences, Edinburgh, EH9, United Kingdom, Jonathan M Gregory, Met Office Hadley center for Climate Change, Exeter, United Kingdom, Nicolas Freychet, School of Geosciences, University of Edinburgh, Edinburgh, UK, Edinburgh, United Kingdom and Coralia Cartis, University of Oxford, Oxford, United Kingdom
Nonlinear equilibrium climate sensitivity in a perturbed physics ensemble (241957)
Jonah Bloch-Johnson1, Dorian S Abbot1, Eli Tziperman2 and Timothy Cronin3, (1)University of Chicago, Chicago, IL, United States, (2)Harvard University, Cambridge, MA, United States, (3)MIT, Cambridge, MA, United States

Understanding intermodel spread in the lapse rate feedback (244030)
Stephen Po-Chedley1, Kyle Armour2, Cecilia M Bitz3, Mark D Zelinka4 and Qiang Fu1, (1)University of Washington Seattle Campus, Seattle, WA, United States, (2)University of Washington, Seattle, Seattle, WA, United States, (3)University of Washington, Seattle, WA, United States, (4)Lawrence Livermore National Laboratory, Livermore, CA, United States
An assessment of surface radiative forcing and response in climate models (252622)
Ryan J. Kramer, University of Miami, Miami, FL, United States, Brian J. Soden, University of Miami, Rosenstiel School for Marine and Atmospheric Science, Miami, FL, United States and Angeline G Pendergrass, National Center for Atmospheric Research, Boulder, CO, United States

Mechanisms of fast atmospheric energetic equilibration following radiative forcing by Carbon Dioxide (254517)
Stephan Fueglistaler and Tra Dinh, Princeton University, Princeton, NJ, United States

Climate Sensitivity and Natural Variability: Theoretical Frameworks and the Bounding of Radiative Feedback Estimates (255400)
Hansi Alice Singh, Pacific Northwest National Laboratory, Atmospheric Sciences & Global Change, Richland, WA, United States, L. Ruby Leung, PNNL / Climate Physics, Richland, WA, United States, Philip J Rasch, Pacific Northwest National Lab, Richland, WA, United States, Jian Lu, Pacific Northwest National Laboratory, Richland, WA, United States and Oluwayemi Anne Garuba, George Mason University Fairfax, Fairfax, VA, United States

Combining observations and models to reduce uncertainty in the cloud response to global warming (258995)
Joel R Norris, University of California San Diego, La Jolla, CA, United States, Timothy Myers, University of California Los Angeles, Los Angeles, CA, United States and Seethala Chellappan, Scripps Institution of Oceanography, La Jolla, CA, United States

Externally forced patterns of multidecadal cloud change in observations and models (Invited) (259628)
Joel R Norris, University of California San Diego, La Jolla, CA, United States, Robert Allen, University of California Riverside, Riverside, CA, United States, Amato T Evan, Scripps Institute of Oceanography, La Jolla, CA, United States, Mark D Zelinka, Lawrence Livermore National Laboratory, Livermore, CA, United States, Chris O'Dell, Colorado State University, Fort Collins, CO, United States and Stephen A Klein, Lawrence Livermore Laboratory, Livermore, CA, United States

Projected Changes in the Annual Cycle of Precipitation over Central Asia by CMIP5 Models (267043)
Xiaojing Yu, Institute of Desert Meteorology, China Meteorological Administration, Urumqi, China and Yong Zhao, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu, China

Lidar Penetration Depth Observations for Constraining Cloud Longwave Feedbacks (273553)
Thibault Vaillant de Guelis1, Hélène Chepfer1, Vincent Noel2, Rodrigo Guzman1, David M Winker3, Jennifer E Kay4 and Marine Bonazzola5, (1)Laboratoire de Météorologie Dynamique Palaiseau, Palaiseau Cedex, France, (2)Laboratoire d'Aérologie, Toulouse, France, (3)NASA Langley Research Center, Hampton, VA, United States, (4)NCAR, Boulder, CO, United States, (5)Laboratoire de Météorologie Dynamique, Paris, France

SST Patterns, Atmospheric Variability, and Inferred Sensitivities in the CMIP5 Model Archive (279935)
Kate Marvel1, Robert Pincus2 and Gavin A Schmidt1, (1)NASA Goddard Institute for Space Studies, New York, NY, United States, (2)University of Colorado at Boulder, Boulder, CO, United States

Commensurate comparisons of models with energy budget observations reveal consistent climate sensitivities (Invited) (280055)
Kyle Armour, University of Washington, Seattle, Seattle, WA, United States

Improving Constraints on Climate System Properties with Additional Data and New Statistical and Sampling Methods (282095)
Chris E Forest, Pennsylvania State University Main Campus, University Park, PA, United States, Alex G Libardoni, Pennsylvania State University Main Campus, Meteorology, University Park, PA, United States, Andrei P Sokolov, MIT, Cambridge, MA, United States and Erwan Monier, MIT, Center for Global Change Science, Cambridge, MA, United States

Estimating radiative feedbacks from stochastic fluctuations in surface temperature and energy imbalance (282961)
Cristian Proistosescu1, Aaron Donohoe2, Kyle Armour3, Gerard Roe3, Malte F Stuecker3 and Cecilia M Bitz3, (1)Joint Institute for the Study of the Atmosphere and the Ocean, University of Washington, Seattle, Seattle, WA, United States, (2)Applied Physics Laboratory University of Washington, Seattle, WA, United States, (3)University of Washington, Seattle, Seattle, WA, United States

Atmospheric dynamics feedback: concept, simulations and climate implications (284242)
Michael Byrne, ETH Zurich, Zurich, Switzerland; Imperial College London, London, United Kingdom and Tapio Schneider, California Institute of Technology, Pasadena, CA, United States

A revised energy-balance framework for the Earth (292097)
Andrew E Dessler, Texas A&M Univ, College Station, TX, United States

Cloud Feedback Hypothesis Testing with a Data Driven Climate Model Ensemble (293794)
Benjamin M Wagman and Charles S Jackson, University of Texas at Austin, Austin, TX, United States

Extratropical trends in cloud amount, thermodynamic phase, liquid and ice water path (297081)
Brian H Kahn1, Qing Yue2, Matthew D Lebsock2, Daniel McCoy3, Catherine M Naud4, Mark Richardson2, Graeme L Stephens2 and Ivy Tan5, (1)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (2)Jet Propulsion Laboratory, Pasadena, CA, United States, (3)University of Washington, Department of Atmospheric Sciences, Seattle, WA, United States, (4)Columbia University in the City of New York, Palisades, NY, United States, (5)Universities Space Research Association Columbia, Columbia, MD, United States

The Influence of a Varying Precipitation Efficiency on Climate Sensitivity and Feedbacks (298270)
Ryan Li and Trude Storelvmo, Yale University, New Haven, CT, United States

The Diversity of Cloud Responses to Twentieth-Century Sea Surface Temperatures (299228)
Levi Glenn Silvers1,2, David Paynter1 and Ming Zhao1, (1)Geophysical Fluid Dynamics Laboratory, Princeton, NJ, United States, (2)Princeton University, Princeton, NJ, United States

[jai mitchell]

this one will be very useful

Combining observations and models to reduce uncertainty in the cloud response to global warming (258995)
Joel R Norris, University of California San Diego, La Jolla, CA, United States, Timothy Myers, University of California Los Angeles, Los Angeles, CA, United States and Seethala Chellappan, Scripps Institution of Oceanography, La Jolla, CA, United States

[AbruptSLR]

I agree that one should use a sufficiently large scale.  However, cherry picking that scale to show the maximum trend, does you no great service.  The net gain in the 30 years prior to the start of your posted graph was almost 1000 Gt.  Add that to this year's expected 500 Gt gain, and the trend over the past half century is only half that stated on your plot.  Potential ice loss from Greenland is a real concern.  However, we should strive to state the current situation as accurately as possible.

Perhaps you should criticize NASA for the scales of the ice mass plots, and I think that you are doing yourself 'no great service', by implying that you believe that this plot will show a 500 Gt mass gain for Greenland by the end of 2017, as that is a ludicrous suggestion.  Provide a post of the linked NASA's GRACE plot a year from now and we will see who is being reasonable.

Edit: I hope that you are considering runoff in your evaluation of Greenland's net ice mass loss this year.

The linked article confirms that total mass loss in Greenland in 2017 will be approximately neutral:

Title: "Guest post: How the Greenland ice sheet fared in 2017"

https://www.carbonbrief.org/guest-post-greenland-ice-sheet-2017

Extract: "So far we’ve only discussed the surface processes. Incorporating the losses from calving gives us the “total mass budget” for the year.

Since at least 2002, the total mass budget has been substantially negative, with the Greenland ice sheet losing around 200-300bn tonnes of ice each year. This year, thanks partly to Nicole’s snow and partly to the relatively low amounts of melt in the summer, we estimate the total mass budget to be close to zero and possibly even positive.

We should emphasise that this is an educated estimate of the Greenland total mass budget. We will have to wait for further data to become available from various satellite datasets to estimate the actual calving losses. (Unfortunately, it’s not certain the ageing GRACE satellites, which show the trend in mass loss, will provide any more data. Their replacements are planned for launch later this year.)"

[AbruptSLR]

The linked reference confirms that AR5 significantly underestimated natural emissions of methane from wetlands worldwide, and recommends that policy makers shoulder the responsibility of taking corrective actions associated with AR5s shortcomings on this matter:

Zhen Zhang, et al (2017), "Emerging role of wetland methane emissions in driving 21st century climate change", PNAS, vol. 114 no. 36,  9647–9652, doi: 10.1073/pnas.1618765114

http://www.pnas.org/content/114/36/9647.short?utm_content=buffer165f2&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

"Significance
Conventional greenhouse gas mitigation policies ignore the role of global wetlands in emitting methane (CH4) from feedbacks associated with changing climate. Here we investigate wetland feedbacks and whether, and to what degree, wetlands will exceed anthropogenic 21st century CH4 emissions using an ensemble of climate projections and a biogeochemical methane model with dynamic wetland area and permafrost. Our results reveal an emerging contribution of global wetland CH4 emissions due to processes mainly related to the sensitivity of methane emissions to temperature and changing global wetland area. We highlight that climate-change and wetland CH4 feedbacks to radiative forcing are an important component of climate change and should be represented in policies aiming to mitigate global warming below 2°C."

Abstract: "Wetland methane (CH4) emissions are the largest natural source in the global CH4 budget, contributing to roughly one third of total natural and anthropogenic emissions. As the second most important anthropogenic greenhouse gas in the atmosphere after CO2, CH4 is strongly associated with climate feedbacks. However, due to the paucity of data, wetland CH4 feedbacks were not fully assessed in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The degree to which future expansion of wetlands and CH4 emissions will evolve and consequently drive climate feedbacks is thus a question of major concern. Here we present an ensemble estimate of wetland CH4 emissions driven by 38 general circulation models for the 21st century. We find that climate change-induced increases in boreal wetland extent and temperature-driven increases in tropical CH4 emissions will dominate anthropogenic CH4 emissions by 38 to 56% toward the end of the 21st century under the Representative Concentration Pathway (RCP2.6). Depending on scenarios, wetland CH4 feedbacks translate to an increase in additional global mean radiative forcing of 0.04 W·m−2 to 0.19 W·m−2 by the end of the 21st century. Under the “worst-case” RCP8.5 scenario, with no climate mitigation, boreal CH4 emissions are enhanced by 18.05 Tg to 41.69 Tg, due to thawing of inundated areas during the cold season (December to May) and rising temperature, while tropical CH4 emissions accelerate with a total increment of 48.36 Tg to 87.37 Tg by 2099. Our results suggest that climate mitigation policies must consider mitigation of wetland CH4 feedbacks to maintain average global warming below 2 °C."

[jai mitchell]

with no climate mitigation, boreal CH4 emissions are enhanced by 18.05 Tg to 41.69 Tg, due to thawing of inundated areas during the cold season (December to May) and rising temperature, while tropical CH4 emissions accelerate with a total increment of 48.36 Tg to 87.37 Tg by 2099. Our results suggest that climate mitigation policies must consider mitigation of wetland CH4 feedbacks to maintain average global warming below 2 °C."

Those Boreal estimates seem low by about 10X (by 2099) under RCP 8.5  The wetlands CH4 seems high, as changes in precipitation regimes in current peat and rainforest locations should lead to significant drying and fire, not increased CH4 production. 

[AbruptSLR]

The linked reference indicates that the proper definition of the pre-industrial baseline can add 0.2C to IPCC projections of GMSTA.  When one considers that CO2e (for a 100-year time frame) including the influence of ozone is currently over 530 ppm; and that the oceans have been stockpiling heat content since 1750 (which is has already triggered key slow response climate feedback mechanisms); one can appreciate that our situation is more dire than AR5 is indicating:

Schurer et al (2017), "Importance of the pre-industrial baseline for likelihood of exceeding Paris goals", Nature Climate Change 7, 563-567, doi:10.1038/nclimate3345

http://www.nature.com/nclimate/journal/v7/n8/full/nclimate3345.html?foxtrotcallback=true

[AbruptSLR]

It seems to me that the year round Arctic mountain glacier feed recharging of major aquifers and base flow of lowland rivers cannot help but to impact such related matters as: sea ice formation, Arctic Ocean circulation patterns and permafrost degradation rates; more than previously assumed:

A. K. Liljedahl, A. Gädeke, S. O'Neel, T. A. Gatesman & T. A. Douglas (15 July 2017), "Glacierized headwater streams as aquifer recharge corridors, subarctic Alaska", Geophysical Research Letters, DOI: 10.1002/2017GL073834

http://onlinelibrary.wiley.com/doi/10.1002/2017GL073834/abstract;jsessionid=1DA678D531D181E116272B09748AC70E.f04t04?systemMessage=Wiley+Online+Library+will+be+unavailable+on+Saturday+and+Sunday+i.e+16th+and+17th+September+at+3%3A00+EDT+%2F+8%3A00+BST+%2F+12%3A30+IST+%2F+15%3A00+SGT+for+5+hours+and+3hours+for+essential+maintenance.+Apologies+for+any+inconvenience+caused+.

Abstract: "Arctic river discharge has increased in recent decades although sources and mechanisms remain debated. Abundant literature documents permafrost thaw and mountain glacier shrinkage over the past decades. Here we link glacier runoff to aquifer recharge via a losing headwater stream in subarctic Interior Alaska. Field measurements in Jarvis Creek (634 km2), a subbasin of the Tanana and Yukon Rivers, show glacier meltwater runoff as a large component (15–28%) of total annual streamflow despite low glacier cover (3%). About half of annual headwater streamflow is lost to the aquifer (38 to 56%). The estimated long-term change in glacier-derived aquifer recharge exceeds the observed increase in Tanana River base flow. Our findings suggest a linkage between glacier wastage, aquifer recharge along the headwater stream corridor, and lowland winter discharge. Accordingly, glacierized headwater streambeds may serve as major aquifer recharge zones in semiarid climates and therefore contributing to year-round base flow of lowland rivers."

[AbruptSLR]

Per the following op/ed piece: "Earth’s energy imbalance (EEI): the difference between incoming solar radiation and outgoing longwave (thermal) radiation." Furthermore, ocean heat content, OHC, is the dominate measure of EEI, and therefore should be reported in the output of CMIP6 as per the second cited reference Cheng et al (2017) the measured OHC of the upper 2,000 m of ocean since 1960 is actually 13% higher than assumed in CMIP5 {& the increase in OHC (including ice melt) is 18% than that for the upper 2,000 m].

Given the vital importance of this OHC with regard to 'slow response' feedback mechanisms such as the ice-climate feedback mechanism, the ESLD assumptions of CMIP5 and AR5 will likely extract a heavy price from future generations.

Title: "Taking the Pulse of the Planet"

https://eos.org/opinions/taking-the-pulse-of-the-planet?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz091517

Extract: "Ocean heat content and sea level rise measurements may provide a more reliable answer than atmospheric measurements
…
Since 2006, the Argo program of autonomous profiling floats has provided near-global coverage of the upper 2,000 meters of the ocean over all seasons [Riser et al., 2016]. In addition, climate scientists have been able to quantify the ocean temperature changes back to 1960 on the basis of the much sparser historical instrument record [Cheng et al., 2017].

From these temperature measurements, scientists extract OHC. These analyses show that during 2015 and 2016, the heat stored in the upper 2,000 meters of the world ocean reached a new 57-year record high (Figure 1). This heat storage amounts to an increase of 30.4 × 1022 Joules (J) since 1960 [Cheng et al., 2017], equal to a heating rate of 0.33 Watts per square meter (W m−2) averaged over Earth’s entire surface—0.61 W m−2 after 1992. Improved measurements have revised these values upward by 13% compared with the results of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Rhein et al., 2013].

Studies show that taking the full ocean depth, ice melt, and other factors into account, Earth is estimated to have gained 0.40 ± 0.09 W m−2 since 1960 and 0.72 W m−2 since 1992 [Cheng et al., 2017]—18% higher than for the top 2,000-meter OHC alone.
…
The EEI has implications for the future and should be fundamental in guiding future energy policy and decisions; it is the heartbeat of the planet. Changes in OHC, the dominant measure of EEI, should be a fundamental metric along with SLR.

As we continue to scrutinize the fidelity of specific climate models, it is critical to validate their energetic imbalances as well as their depiction of GMST. The fact that the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble mean accurately represents observed global OHC changes [Cheng et al., 2016] is critical for establishing the reliability of climate models for long-term climate change projections.

Consequently, we recommend that both the EEI and OHC be listed as output variables in the CMIP6 models, in addition to SLR and GMST. This vital sign informs societal decisions about adaptation to and mitigation of climate change [Trenberth et al., 2016]."

See also the associated reference:

Lijing Cheng, Kevin E. Trenberth, John Fasullo, Tim Boyer, John Abraham & Jiang Zhu (10 Mar 2017), "Improved estimates of ocean heat content from 1960 to 2015", Science Advances, Vol. 3, no. 3, e1601545, DOI: 10.1126/sciadv.1601545

http://advances.sciencemag.org/content/3/3/e1601545

Abstract: "Earth’s energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the data-rich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and with variability on decadal and multidecadal time scales (signal) that can be reliably distinguished from sampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes in OHC are relatively small before about 1980; since then, OHC has increased fairly steadily and, since 1990, has increasingly involved deeper layers of the ocean. In addition, OHC changes in six major oceans are reliable on decadal time scales. All ocean basins examined have experienced significant warming since 1998, with the greatest warming in the southern oceans, the tropical/subtropical Pacific Ocean, and the tropical/subtropical Atlantic Ocean. This new look at OHC and EEI changes over time provides greater confidence than previously possible, and the data sets produced are a valuable resource for further study."

[AbruptSLR]

The linked open access reference indicates that following a BAU pathway through 2050 could pose existential risks to large portion of the Earth's population by the end of this century:

Ramanathan, V., Molina, M.J., Zaelke, D., Borgford-Parnell, N.,
Xu, Y., Alex, K., Auffhammer, M., Bledsoe, P., Collins, W., Croes, B., Forman, F., Gustafsson, Ö,
Haines, A., Harnish, R., Jacobson, M.Z., Kang, S., Lawrence, M., Leloup, D., Lenton, T., Morehouse, T., Munk, W., Picolotti, R., Prather, K., Raga, G., Rignot, E., Shindell, D., Singh, A.K., Steiner, A., Thiemens, M., Titley, D.W., Tucker, M.E., Tripathi, S., & Victor, D., Well Under 2 Degrees Celsius: Fast Action Policies to Protect People and the Planet from Extreme Climate Change, 2017. Available at: http://www-ramanathan.ucsd.edu/about/publications.php and www.igsd.org/publications/

http://www.igsd.org/wp-content/uploads/2017/09/Well-Under-2-Degrees-Celsius-Report-2017.pdf

Extract: "A massive effort will be needed to stop warming at 2°C, and time is of the essence. With unchecked business-as-usual emissions, global warming has a 50% likelihood of exceeding 4ºC and a 5% probability of exceeding 6ºC in this century, raising existential questions for most, but especially the poorest three billion people.  A 4ºC warming is likely to expose as many as 75% of the global population to deadly heat."

See also:

Title: "Scripps says climate change may represent "existential" threat to humanity"

http://www.sandiegouniontribune.com/news/science/

[AbruptSLR]

The linked article discusses the timing and outline for AR6.  It is my opinion that it will be 'a day late and a dollar short' w.r.t. to helping society to prevent a socio-economic collapse in the 2050-2060 timeframe:

Title: "Guest post: What will be in the next IPCC climate change assessment"

https://www.carbonbrief.org/guest-post-what-will-be-in-the-next-ipcc-climate-change-assessment

Extract: "At a meeting in Montreal last week, the member countries of the United Nations reached an important decision about the next few years of the IPCC – the scientific body that assesses climate change. All countries agreed on the outlines for the three main components of the next major report, due in 2021-22, which is the vital groundwork that will now guide the contributions of climate change researchers from all over the world.
…
A final important aspect of our new outline is that it is designed to complement and build on the three special reports that are already underway.

The idea of special reports is that they are smaller than the main assessment reports and focus on a specific topic of interest. The first one is on global warming of 1.5C (the first draft of which is currently out for expert review). The second special report is on the oceans and cryosphere in a changing climate and the third is on climate change and land. AR6 will revisit the findings of these special reports and update them on the basis of new lines of evidence. New results from climate model simulations performed under the sixth phase of the Climate Model Intercomparison Project (CMIP6) will be available by the time of AR6, for example."

[Archimid]

Parkinson's law:  "work expands so as to fill the time available for its completion"

The IPCC is too slow to keep up with climate change. They need to set shorter deadlines but at the same time iterate more than before.

[rboyd]

That they are even discussing 1.5 degrees shows how out of touch they are from the reality of climate change. By 2022 we may already be pretty damn close to 1.5 degrees. Perhaps an early breach of that will allow for a reconnection with reality? I wont hold my breath ....

[AbruptSLR]

That they are even discussing 1.5 degrees shows how out of touch they are from the reality of climate change. By 2022 we may already be pretty damn close to 1.5 degrees. Perhaps an early breach of that will allow for a reconnection with reality? I wont hold my breath ....

In the linked article, Beck & Mahony (2017) question the role of science/politics w.r.t. the IPCC in monitoring/regulating the Paris Agreement.  For example the scientists are being asked to vouchsafe that countries will actually implement BECCS (bio-energy with carbon capture and storage) to suck CO₂ from the sky so that the 1.5C target is still possible.

Beck, S. & Mahony, M. (2017), "The IPCC and the politics of anticipation", Nat. Clim. Change 7, 311–313

http://www.nature.com/nclimate/journal/v7/n5/full/nclimate3264.html

See also:
http://www.nature.com/nclimate/journal/v7/n9/full/nclimate3379.html

[AbruptSLR]

The following is an example of how scientists are being asked by the US DOE management to include subroutines in their climate model (here ACME) that allow human control of the biosphere to suck CO₂ out of the atmosphere after 2050 (see second image).  I doubt that humans will implement sufficient BECCS by 2050 to start sucking CO₂ out of the air.

Peter E. Thornton et al, Biospheric feedback effects in a synchronously coupled model of human and Earth systems, Nature Climate Change (2017). DOI: 10.1038/nclimate3310

http://www.nature.com/nclimate/journal/v7/n7/full/nclimate3310.html?foxtrotcallback=true

Abstract: "Fossil fuel combustion and land-use change are the two largest contributors to industrial-era increases in atmospheric CO 2 concentration. Projections of these are thus fundamental inputs for coupled Earth system models (ESMs) used to estimate the physical and biological consequences of future climate system forcing. While historical data sets are available to inform past and current climate analyses, assessments of future climate change have relied on projections of energy and land use from energy–economic models, constrained by assumptions about future policy, land-use patterns and socio-economic development trajectories. Here we show that the climatic impacts on land ecosystems drive significant feedbacks in energy, agriculture, land use and carbon cycle projections for the twenty-first century. We find that exposure of human-appropriated land ecosystem productivity to biospheric change results in reductions of land area used for crops; increases in managed forest area and carbon stocks; decreases in global crop prices; and reduction in fossil fuel emissions for a low–mid-range forcing scenario. The feedbacks between climate-induced biospheric change and human system forcings to the climate system—demonstrated here—are handled inconsistently, or excluded altogether, in the one-way asynchronous coupling of energy–economic models to ESMs used to date."

See also the associated linked article entitled:  Titan simulations show importance of close two-way coupling between human and Earth systems"

https://phys.org/news/2017-07-titan-simulations-importance-two-way-coupling.html

Extract: "Through the Advanced Scientific Computing Research Leadership Computing Challenge program, Thornton's team was awarded 85 million compute hours to improve the Accelerated Climate Modeling for Energy (ACME) effort, a project sponsored by the Earth System Modeling program within DOE's Office of Biological and Environmental Research. Currently, ACME collaborators are focused on developing an advanced climate model capable of simulating 80 years of historic and future climate variability and change in 3 weeks or less of computing effort.

Now in its third year, the project has achieved several milestones—notably the development of ACME version 1 and the successful inclusion of human factors in one of its component models, the iESM.

"What's unique about ACME is that it's pushing the system to a higher resolution than has been attempted before," Thornton said. "It's also pushing toward a more comprehensive simulation capability by including human dimensions and other advances, yielding the most detailed Earth system models to date.
…
The development of iESM started before the ACME initiative when a multilaboratory team aimed to add new human dimensions—such as how people affect the planet to produce and consume energy—to Earth system models. The model—now a part of the ACME human dimensions component—is being merged with ACME in preparation for ACME version 2.
…
ACME version 1 will be publicly released in late-2017 for analysis and use by other researchers. Results from the model will also contribute to the Coupled Model Intercomparison Project, which provides foundational material for climate change assessment reports."

[AbruptSLR]

As a follow-on to my last post, and in an attempt to be clearer, when I state that consensus climate scientists err on the side of least drama, ESLD, I mean that consensus climate science as expressed in AR5 is biased.  More specifically, I mean that applications of the scientific method (as opposed to IPCC processes) should deal with uncertainty by examining a range of values from the lower to the upper bounds for all climate change issues in an unbiased manner.

For those who believe that the IPCC process is unbiased I offer the following counter arguments:
1. Regarding anthropogenic radiative forcing, since FAR (first assessment report) actual emissions have followed BAU pathways near the upper bounds of the SRES (Special Report on Emissions Scenarios) and RCP (Representative Concentration Pathways) families of scenarios.  If these scenarios were constructed in a nonbiased manner we would have followed a median scenario.  Furthermore, scientists decreased the ranges of uncertainties of emissions in SRES scenarios when they constructed RCP, yielding to pressure from policies maker to accept that emission regulations would limit the range of uncertainties; however, this has not consistently been the case (e.g. the Trump Administration & methane leaks from both fracking and agriculture).  Now for AR6 some scientists are trying to resist political pressure to include hypothetical negative emissions technology into the lower bounds of future emission scenarios.

2. Given that radiative forcing rates currently many times higher than during the PETM, IPCC should be reporting measures of dynamical climate sensitivity rather than reporting their 'canonical' range for equilibrium climate sensitivity, ECS, and also rather than using transient climate response, TCR, to calculate our carbon budget.  Also, I note the fact that the 'canonical' range for ECS has largely not changed for decades hints that the IPCC process in thwarting the scientific method from narrowing down this range of uncertainty.  Furthermore, IPCC inappropriately mixes together several different definitions of ECS [e.g. see Proistosescu and Huybers (2017)], which is just bad science.

3.  The paleo record contains numerous cases of abrupt climate change within periods of several decades, say due to hosing events, which are excluded from AR5 projections.  In unbiased analysis cases would be presented both with and without such short-term forcings (such as the abrupt collapse of the WAIS within the next several decades).

4.  Not only does the IPCC process ignore short-term dynamical forcing, but it also ignores numerous 'slow-response' feedback mechanisms (such as carbon emissions from permafrost degradation this century).  An unbiased process would examine cases both with and without such 'slow response' feedback mechanism.

These are just a few examples of how the IPCC process caveats their projections in a manner that introduces bias due to ESLD.

[AbruptSLR]

The linked reference indicates that Arctic permafrost regions may change from a carbon sink to a carbon source sooner than conventional scientists are assuming:

Parazoo, N. C., Koven, C. D., Lawrence, D. M., Romanovsky, V., and Miller, C. E.: Detecting the permafrost carbon feedback: Talik formation and increased cold-season respiration as precursors to sink-to-source transitions, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-189, in review, 2017.

https://www.the-cryosphere-discuss.net/tc-2017-189/

Abstract. Thaw and release of permafrost carbon (C) due to climate change is likely to offset increased vegetation C uptake in Northern High Latitude (NHL) terrestrial ecosystems. Models project that this permafrost C feedback may act as a slow leak, in which case detection and attribution of the feedback may be difficult. The formation of talik, a sub-surface layer of perennially thawed soil, can accelerate permafrost degradation and soil respiration, ultimately shifting the C balance of permafrost affected ecosystems from long-term C sinks to long-term C sources. It is imperative to understand and characterize mechanistic links between talik, permafrost thaw, and respiration of deep soil C to detect and quantify the permafrost C feedback. Here, we use the Community Land Model (CLM) version 4.5, a permafrost and biogeochemistry model, in comparison to long term deep borehole data along North American and Siberian transects, to investigate thaw driven C sources in NHL (> 55° N) from 2000–2300. Widespread talik at depth IS projected across most of the NHL permafrost region (14 million km2) by 2300, correlated to increased cold season warming, earlier spring thaw, and growing active layers. Talik formation peaks in the 2050s in warm permafrost regions in the sub-Arctic. Comparison to borehole data suggests talik formation may even occur sooner. Accelerated decomposition of deep soil C following talik onset shifts the surface balance of photosynthetic uptake and litter respiration into long-term C sources across 3.2 million km2 of permafrost. Talik driven sources occur predominantly in warm permafrost, but sink-to-source transition dates are delayed by decades to centuries due to high ecosystem productivity. In contrast, most of the cold permafrost region in the northern Arctic (3 million km2) shifts to a net source by the end of the 21st century in the absence of talik due to the high decomposition rates of shallow, young C in organic rich soils coupled with low productivity. Our results provide important clues signaling imminent talik onset and C source transition including: (1) late cold season (Jan–Feb) soil warming at depth (~ 2 m), (2) increasing cold season emissions (Nov–Apr), (3) enhanced respiration of deep, old C in warm permafrost and young, shallow C in organic rich cold permafrost soils. Our results suggest a mosaic of processes that govern carbon source-to-sink transitions at high latitudes, and emphasize the urgency of monitoring soil thermal profiles, organic C age and content, cold season CO2 emissions, and atmospheric 14CO2 as key indicators of the permafrost C feedback.

[AbruptSLR]

The linked reference states: "… subtropical mode water has warmed over the past six decades in both the North Pacific and North Atlantic.  The rate of the warming is twice as large in the mode waters than at the surface."  This indicates that the equatorial warm water pools on the western side of these oceans are rapidly advecting warm water into the mode water circulation; which will impact both carbon dioxide uptake into these oceans and impact ocean circulation patterns more than previously assumed:

Sugimoto et al (2017), "Enhanced warming of the subtropical mode water in the North Pacific and North Atlantic", Nature Climate Change, doi: 1038/nclimate3371

http://www.nature.com/nclimate/journal/v7/n9/full/nclimate3371.html

See also: "Mode Water"

http://www.nature.com/nclimate/journal/v7/n9/full/nclimate3371.html

Extract: "Mode waters have a big impact on nutrients distribution as they prevent deep-ocean nutrients from upwelling to the euphotic zone. Further more, they will control the biological pump, which plays an important role in carbon dioxide uptake. Dynamically, mode waters also control potential vorticity and baroclinic in the subtropical North Atlantic."

[AbruptSLR]

The linked reference indicates that BAU forcing will produce more carbon emissions from the pan-Arctic region than was previously appreciated:

Chaudhary, N., Miller, P. A., and Smith, B.: Modelling past, present and future peatland carbon accumulation across the pan-Arctic region, Biogeosciences, 14, 4023-4044, https://doi.org/10.5194/bg-14-4023-2017, 2017.

https://www.biogeosciences.net/14/4023/2017/
https://www.biogeosciences.net/14/4023/2017/bg-14-4023-2017.pdf

Abstract. Most northern peatlands developed during the Holocene, sequestering large amounts of carbon in terrestrial ecosystems. However, recent syntheses have highlighted the gaps in our understanding of peatland carbon accumulation. Assessments of the long-term carbon accumulation rate and possible warming-driven changes in these accumulation rates can therefore benefit from process-based modelling studies. We employed an individual-based dynamic global ecosystem model with dynamic peatland and permafrost functionalities and patch-based vegetation dynamics to quantify long-term carbon accumulation rates and to assess the effects of historical and projected climate change on peatland carbon balances across the pan-Arctic region. Our results are broadly consistent with published regional and global carbon accumulation estimates. A majority of modelled peatland sites in Scandinavia, Europe, Russia and central and eastern Canada change from carbon sinks through the Holocene to potential carbon sources in the coming century. In contrast, the carbon sink capacity of modelled sites in Siberia, far eastern Russia, Alaska and western and northern Canada was predicted to increase in the coming century. The greatest changes were evident in eastern Siberia, north-western Canada and in Alaska, where peat production hampered by permafrost and low productivity due the cold climate in these regions in the past was simulated to increase greatly due to warming, a wetter climate and higher CO2 levels by the year 2100. In contrast, our model predicts that sites that are expected to experience reduced precipitation rates and are currently permafrost free will lose more carbon in the future.

[AbruptSLR]

I believe that the linked reference contains a reasonable discussion, for the public, of many of the risks of abrupt sea level rise this century (see the attached extracts and images with associated captions).  Nevertheless, as it is doubtful that any state-of-the-art Earth System climate models (like ACME) with state-of-the-art marine glacier sub-models and associated freshwater hosing, will be adequate for characterizing the risks of abrupt sea level rise this century, for at least 10 to 20 years; I provide the following comments:

1. In the attached Figure 10 for the WAIS, the right panel roughly represents an ice cliff face retreat rate of about 1 km/year; while the left panel roughly represents an ice cliff retreat roughly 5km/year; however, Greenland marine glaciers have exhibited ice cliff retreat rates of over 10 km/year.  Thus while it is laudable that DeConto et. al. have a paper in the publishing process that will examine the WAIS with ice cliff retreat rates of roughly 10 km/year; we do not know that 10 km/year is the upper limit for such a retreat rate for key WAIS marine glaciers like the Thwaites Glacier.  In this regards, I note that DeConto & Pollard 2016 report an upper bound for sea level rise by 2100 of 2.5 +/- 0.15m; Hansen indicates that there is a risk that global mean sea level rise might reach 5 m SLR by 2100.

2.  While model makers need to do the best that they can; policy makers should conduct probable failure mode analyses, PFMA, to try to attempt to characterize the risks not captured by current climate models.  In this regards, I note that the paleo record for the MIS 11 (Holsteinian) era indicates a climate sensitivity much higher than current ESMs can match, and this many well be because they do not adequately model Hansen's ice-climate feedback mechanism.

3.  Examples of mechanism's not yet adequately characterized by  current state of the art WAIS ice sheet models (besides the 10km/year ice cliff retreat rate, yet to be published by DeConto et. al) include: (a) possible ice cliff retreat rates higher than 10km/year; (b) the influence of the high geothermal heat flux beneath all WAIS marine glaciers; (c) potential abrupt ice mass loss triggered local earthquakes, volcanic eruptions and methane emissions from seafloor hydrates; d) bipolar interactions between the GIS and the AIS; and (d) the influence of increased local storm activity associated with Hansen's ice-climate interaction.  Also, I note that the Antarctic folder identifies numerous other possible positive feedback mechanisms not yet addressed by current ESM projections (including high values of ECS):

Griggs, G, Arvai, J, Cayan, D, DeConto, R, Fox, J, Fricker, HA, Kopp, RE, Tebaldi, C, Whiteman, EA (California Ocean Protection Council Science Advisory Team Working Group). Rising Seas in California: An Update on Sea-Level Rise Science. California Ocean Science Trust, April 2017.

http://www.opc.ca.gov/webmaster/ftp/pdf/docs/rising-seas-in-california-an-update-on-sea-level-rise-science.pdf

Extract: "In the future ice-sheet ensembles shown in Figure 10, a range of maximum cliff-failure rates are used, ranging between one and five km per year. At the tallest vertical ice cliffs observed today (e.g., Helheim and Jakobsavn glaciers in Greenland), the horizontal rate of cliff retreat is as high as 10-14km per year (Joughin et al., 2010; 2012). This is quite remarkable, considering these outlet glaciers rest in narrow fjords 5 to 12 km wide, choked with dense melange as seen in Figure 9. 

In Antarctica, the cliff faces that could appear in the future will be much taller and wider than those in Greenland, where melange can clog seaways. For example, Thwaites Glacier is >120 km wide and its terminus ends in open ocean rather than a narrow fjord, so it might be reasonable to assume cliff collapse in open settings like Thwaites could approach the rates observed in narrow Greenland fjord settings where melange is presumably providing some back pressure at the grounding line. Increasing the model’s maximum cliff retreat values closer to those observed in Greenland (~10 km per year) increases Antarctica’s simulated contribution to GMSL to more than 2m by 2100 in the RCP8.5 scenario (DeConto et al., in preparation)."

Captions:  "Figure 8. A similar ice sheet margin as shown in Figure 6, but feeling the effects of both sub iceshelf oceanic warming and atmospheric warming. Meltwater and rainwater accumulating on the iceshelf surface can fill crevasses (a), which deepens the crevasses, potentially leading to hydrofracturing (b). If the newly exposed grounding line is thick enough to have a tall subaerial ice cliff (c), the terminus would fail structurally. If the rate of structural failure outpaces the seaward flow of ice, the ice margin would back into the deep basin (after Pollard et al., 2015; DeConto and Pollard, 2016), resulting in amassive loss of ice."

"Figure 10. Ensembles of Antarctic’s future contribution to sea level, using paleo-calibrated ice-model physics, high resolution atmospheric climatologies from a regional atmospheric model, and time-evolving ocean model temperatures (from DeConto and Pollard, 2016). The inset at right shows time-evolving CO2 concentrations (RCPs) used to force the ice sheet simulations (from van Vuuren et al., 2011). Note that different colors are used to represent the RCPs and ice sheet ensembles. The difference between the ensembles at left versus right lies in the assumptions used in the model calibration (based on geological sea-level reconstructions). These differences demonstrate the large uncertainty remaining in current projections. The timing when Antarctica begins major retreat in RCP4.5 and 8.5 (after ~2060) also remains uncertain. In addition to greenhouse-gas forcing, the onset of major retreat will be dependent on the trajectory of Antarctic warming in response to a complex combination of factors including recovery of the ozone hole, linkages with tropical dynamics, and feedbacks between the ice-sheet, solid-Earth, ocean, and sea ice which are not accounted for here. Addressing these shortcomings and uncertainties will be the focus of future work."

"Figure 12. Porous firn (a, left) can absorb seasonal meltwater and delay water flow into underlying crevasses (b, right), delaying hydrofacturing and ice-shelf breakup. Better treatments of these processes in ice sheet models will be critical for predicting the precise timing of the ice sheet’s response to a warming climate (figure source: Munneke, et al., 2014)."

[jai mitchell]

it appears to me at the point of transition from seafloor highstand to inner deep recess that the loss of the ice sheet buttress would promote increased rates of flow from grounded glacier above sea level through plastic deformation. 

It seems that the transition here is really dependent on whether this increased surface flow/deformation has a limiting speed and if the rate of deep water undercutting once the seafloor rise is past is working faster than this surface flow outwards. 

IF it is not fast enough, then the increased collapse will move at a much faster rate and sea level rise will grow significantly through calving.

Much more, the potential increase in surface melt and rainfall events in WAIS under a much warmer world (guessing ~+4.0C here) would lead to additional structural weakening, increased internal heat and faster flows & slumping at the grounding line as it regresses back into the deep cavity.  This will work to prevent rapid undercutting, and reduce the cliff height.

[AbruptSLR]

it appears to me at the point of transition from seafloor highstand to inner deep recess that the loss of the ice sheet buttress would promote increased rates of flow from grounded glacier above sea level through plastic deformation. 

It seems that the transition here is really dependent on whether this increased surface flow/deformation has a limiting speed and if the rate of deep water undercutting once the seafloor rise is past is working faster than this surface flow outwards. 

IF it is not fast enough, then the increased collapse will move at a much faster rate and sea level rise will grow significantly through calving.

Much more, the potential increase in surface melt and rainfall events in WAIS under a much warmer world (guessing ~+4.0C here) would lead to additional structural weakening, increased internal heat and faster flows & slumping at the grounding line as it regresses back into the deep cavity.  This will work to prevent rapid undercutting, and reduce the cliff height.

Obviously, this topic is a complex one and it can be difficult to conceptualize the mechanisms that DeConto, Pollard et al are trying to convey so I provide the link that leads to a April 2016 EGU General Assembly press conference 8 video clip that includes a talk by DeConto; and I provide four images to provide some idea of the scales that we are considering:

http://client.cntv.at/egu2016/press-conference-8

[AbruptSLR]

The linked article indicates that observations indicate that that tropical rainforests are already changing from carbon sinks to carbon sources.  As Paris projections do not account for this response, this can either be viewed as an opportunity for third world governments to try harder to protect the rainforests, or one can be concerned that this observed trend may continue and/or accelerate:

A. Baccini, W. Walker, L. Carvalho, M. Farina, D. Sulla-Menashe & R. A. Houghton (28 Sep 2017), "Tropical forests are a net carbon source based on aboveground measurements of gain and loss", Science, eaam5962, DOI: 10.1126/science.aam5962

http://science.sciencemag.org/content/early/2017/09/27/science.aam5962

Abstract: "The carbon balance of tropical ecosystems remains uncertain, with top-down atmospheric studies suggesting an overall sink and bottom-up ecological approaches indicating a modest net source. Here we use 12 years (2003–2014) of MODIS pantropical satellite data to quantify net annual changes in the aboveground carbon density of tropical woody live vegetation, providing direct, measurement-based evidence that the world’s tropical forests are a net carbon source of 425.2 ± 92.0 Tg C yr–1. This net release of carbon consists of losses of 861.7 ± 80.2 Tg C yr–1 and gains of 436.5 ± 31.0 Tg C yr–1. Gains result from forest growth; losses result from deforestation and from reductions in carbon density within standing forests (degradation/disturbance), with the latter accounting for 68.9% of overall losses."

See also:

Title: "Alarm as study reveals world’s tropical forests are huge carbon emission source"

https://www.theguardian.com/environment/2017/sep/28/alarm-as-study-reveals-worlds-tropical-forests-are-huge-carbon-emission-source

Extract: "Forests globally are so degraded that instead of absorbing emissions they now release more carbon annually than all the traffic in the US, say researchers
…
Researchers found that forest areas in South America, Africa and Asia – which have until recently played a key role in absorbing greenhouse gases – are now releasing 425 teragrams of carbon annually, which is more than all the traffic in the United States."

[AbruptSLR]

jai,

While pointing at paleo information is tricky, I note that Pollard et al. (2015) calibrated their model (with cliff failure and hydrofracturing) to match the observed Pliocene paleo condition of the WAIS, and when they did so they found that once the tipping point was reached for the WAIS the subsequent WAIS contribution to SLR was indicated by the first attached plot.  This plot indicates much more aggressive ice mass loss from the WAIS than projected by DeConto & Pollard (2016) for various future RCP scenarios.  Furthermore, I attach the second image to make it clear that David Pollard and Robert DeConto's model includes not only ice flow, bottom topography but also ocean-ice interaction for the WAIS.

Thus if you believe that we are moving rapidly towards Pliocene conditions then you may want to be concerned that DeConto & Pollard (2016) upper bound projection of global mean sea level rise by 2100 of 2.5 +/- 0.15m, by err on the side of least drama:

DavidPollard, Robert M.DeConto and Richard B.Alley (15 February 2015), "Potential Antarctic Ice Sheet retreat driven by hydrofracturing and ice cliff failure", Earth and Planetary Science Letters, Volume 412, Pages 112-121, https://doi.org/10.1016/j.epsl.2014.12.035

http://www.sciencedirect.com/science/article/pii/S0012821X14007961
&
http://www.sciencedirect.com/science/article/pii/S0012821X14007961/pdfft?md5=f698e5b95bf63f112844d84d8749c259&pid=1-s2.0-S0012821X14007961-main.pdf

Extract: "Geological data indicate that global mean sea level has fluctuated on 10³ to 10⁶ yr time scales during the last ∼25 million years, at times reaching 20 m or more above modern. If correct, this implies substantial variations in the size of the East Antarctic Ice Sheet (EAIS). However, most climate and ice sheet models have not been able to simulate significant EAIS retreat from continental size, given that atmospheric CO₂ levels were relatively low throughout this period. Here, we use a continental ice sheet model to show that mechanisms based on recent observations and analysis have the potential to resolve this model–data conflict. In response to atmospheric and ocean temperatures typical of past warm periods, floating ice shelves may be drastically reduced or removed completely by increased oceanic melting, and by hydrofracturing due to surface melt draining into crevasses. Ice at deep grounding lines may be weakened by hydrofracturing and reduced buttressing, and may fail structurally if stresses exceed the ice yield strength, producing rapid retreat. Incorporating these mechanisms in our ice-sheet model accelerates the expected collapse of the West Antarctic Ice Sheet to decadal time scales, and also causes retreat into major East Antarctic subglacial basins, producing ∼17 m global sea-level rise within a few thousand years. The mechanisms are highly parameterized and should be tested by further process studies. But if accurate, they offer one explanation for past sea-level high stands, and suggest that Antarctica may be more vulnerable to warm climates than in most previous studies."

Best,
ASLR

Edit, with a hat-tip to yourself (jai), I provide the third attached image of a 'close-up' of the first image, where in the Antarctic folder you noted:

"3 meters in 35 to 45 years"

Edit 2, for those who want the plan view for the third image in Reply #1919, I provide it here as my fourth attachment:

[AbruptSLR]

The linked reference indicates that the IPCC underestimated methane emissions from livestock:

Julie Wolf, Ghassem R. Asrar and Tristram O. West (2017), "Revised methane emissions factors and spatially distributed annual carbon fluxes for global livestock", Carbon Balance and Management, 12:16, https://doi.org/10.1186/s13021-017-0084-y

https://cbmjournal.springeropen.com/articles/10.1186/s13021-017-0084-y

Abstract: "Background
Livestock play an important role in carbon cycling through consumption of biomass and emissions of methane. Recent research suggests that existing bottom-up inventories of livestock methane emissions in the US, such as those made using 2006 IPCC Tier 1 livestock emissions factors, are too low. This may be due to outdated information used to develop these emissions factors. In this study, we update information for cattle and swine by region, based on reported recent changes in animal body mass, feed quality and quantity, milk productivity, and management of animals and manure. We then use this updated information to calculate new livestock methane emissions factors for enteric fermentation in cattle, and for manure management in cattle and swine.

Results
Using the new emissions factors, we estimate global livestock emissions of 119.1 ± 18.2 Tg methane in 2011; this quantity is 11% greater than that obtained using the IPCC 2006 emissions factors, encompassing an 8.4% increase in enteric fermentation methane, a 36.7% increase in manure management methane, and notable variability among regions and sources. For example, revised manure management methane emissions for 2011 in the US increased by 71.8%. For years through 2013, we present (a) annual livestock methane emissions, (b) complete annual livestock carbon budgets, including carbon dioxide emissions, and (c) spatial distributions of livestock methane and other carbon fluxes, downscaled to 0.05 × 0.05 degree resolution.

Conclusions
Our revised bottom-up estimates of global livestock methane emissions are comparable to recently reported top-down global estimates for recent years, and account for a significant part of the increase in annual methane emissions since 2007. Our results suggest that livestock methane emissions, while not the dominant overall source of global methane emissions, may be a major contributor to the observed annual emissions increases over the 2000s to 2010s. Differences at regional and local scales may help distinguish livestock methane emissions from those of other sectors in future top-down studies. The revised estimates allow improved reconciliation of top-down and bottom-up estimates of methane emissions, will facilitate the development and evaluation of Earth system models, and provide consistent regional and global Tier 1 estimates for environmental assessments."

See also:
Title: "Methane emissions from cattle are 11% higher than estimated"

[AbruptSLR]

For those who want more paleo information on potential sea level rise contribution from the WAIS I provide the following linked reference and four attached images.  The first two images are from the reference while I provide the last two for background information:

The linked (open access) article indicates, based on physical evidence, that for the past 1.4 million years the WAIS contribution to global sea level during interglacial periods has been limited to 3.3m.  The first image shows the location of the location of the study area, and the second image shows the minimum WAIS ice sheet extend over that duration:

Andrew S. Hein, John Woodward, Shasta M. Marrero, Stuart A. Dunning, Eric J. Steig, Stewart P. H. T. Freeman, Finlay M. Stuart, Kate Winter, Matthew J. Westoby & David E. Sugden (2016), "Evidence for the stability of the West Antarctic Ice Sheet divide for 1.4 million years", Nature Communications, Volume: 7, Article number: 10325, doi:10.1038/ncomms10325


http://www.nature.com/ncomms/2016/160203/ncomms10325/full/ncomms10325.html

Abstract: "Past fluctuations of the West Antarctic Ice Sheet (WAIS) are of fundamental interest because of the possibility of WAIS collapse in the future and a consequent rise in global sea level. However, the configuration and stability of the ice sheet during past interglacial periods remains uncertain. Here we present geomorphological evidence and multiple cosmogenic nuclide data from the southern Ellsworth Mountains to suggest that the divide of the WAIS has fluctuated only modestly in location and thickness for at least the last 1.4 million years. Fluctuations during glacial–interglacial cycles appear superimposed on a long-term trajectory of ice-surface lowering relative to the mountains. This implies that as a minimum, a regional ice sheet centred on the Ellsworth-Whitmore uplands may have survived Pleistocene warm periods. If so, it constrains the WAIS contribution to global sea level rise during interglacials to about 3.3 m above present."

[AbruptSLR]

The following abstract is from the Fall 2015 AGU conference in San Francisco, clearly indicates that periodic collapses of the WAIS contributes to bipolar superinterglacials with exceptionally high climate sensitivities:

Julie Brigham-Grette (2015), "Thin Ice -- Bipolar Super Interglacials and our Possible Future"

Abstract: "Evidence of exceptionally warm Arctic interglacials from Lake El’gygytgyn NE Russia, combined with the periodic collapse of the West Antarctic Ice Sheet (ANDRILL) suggests the need to reassess climate sensitivity and cryospheric dynamics on many timescales. It may be easier to melt significant portions of large sheets and drive large ecosystem changes in the high latitudes than we thought! Elevated global temperatures of only a few degrees (or less) combined with polar amplification seems to have repeatedly caused large changes in the cryosphere and global sea level, still under investigation given the present knowledge and complexity of glacio-isostatic adjustments. But increasing evidence of a forested Arctic and smaller polar ice sheets in the Pliocene when CO2 was around 400 ppm (like today) and during several more recent super interglacials (under Milankovitch forcing) most likely presages a warming future, partially hidden in recent years by the lagged response of the oceans, atmosphere, and cryosphere to anthropogenic influences. The future will depend on the ability of societies to recognize and respond to the consequences of significant environmental change. The challenge to the science community is to communicate this data-driven reality effectively and without politics."

See also:

Gregory A. De Wet, Isla S. Castañeda, Robert M. DeConto & Julie Brigham-Grette  (February 2016), “A high-resolution mid-Pleistocene temperature record from Arctic Lake El'gygytgyn: A 50 kyr super interglacial from MIS 33 to MIS 31?”Earth and Planetary Science Letters 436:56-63 DOI: 10.1016/j.epsl.2015.12.021 

http://blogs.umass.edu/biogeochem/files/2016/01/de-Wet-et-al.-2016.pdf

Abstract: “Previous periods of extreme warmth in Earth's history are of great interest in light of current and predicted anthropogenic warming. Numerous so called "super interglacial" intervals, with summer temperatures significantly warmer than today, have been identified in the 3.6 million year (Ma) sediment record from Lake El'gygytgyn, northeast Russia. To date, however, a high-resolution paleotemperature reconstruction from any of these super interglacials is lacking. Here we present a paleotemperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) from Marine Isotope Stages (MIS) 35 to MIS 29, including super interglacial MIS 31. To investigate this period in detail, samples were analyzed with an unprecedented average sample resolution of 500 yrs from MIS 33 to MIS 30. Our results suggest the entire period currently defined as MIS 33-31 (~1114-1062 kyr BP) was characterized by generally warm and highly variable conditions at the lake, at times out of phase with Northern Hemisphere summer insolation, and that cold "glacial" conditions during MIS 32 lasted only a few thousand years. Close similarities are seen with coeval records from high southern latitudes, supporting the suggestion that the interval from MIS 33 to MIS 31 was an exceptionally long interglacial (Teitler et al., 2015). Based on brGDGT temperatures from Lake El'gygytgyn (this study and unpublished results), warming in the western Arctic during MIS 31 was matched only by MIS 11 during the Pleistocene.


Coletti, A. J., DeConto, R. M., Brigham-Grette, J., and Melles, M.: A GCM comparison of Pleistocene super-interglacial periods in relation to Lake El'gygytgyn, NE Arctic Russia, Clim. Past, 11, 979-989, doi:10.5194/cp-11-979-2015, 2015.

http://www.clim-past.net/11/979/2015/cp-11-979-2015.pdf
http://www.clim-past.net/11/979/2015/cp-11-979-2015.html

Abstract: "Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stages (MISs) 1 (9 ka), 5e (127 ka), 11c (409 ka) and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the mean temperature of the warmest month (MTWM) indicate conditions up to 0.4, 2.1, 0.5 and 3.1 °C warmer than today during MIS 1, 5e, 11c and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer (JJA) orbital forcing, the extraordinary warmth of MIS 11c compared to the other interglacials in the Lake El'gygytgyn temperature proxy reconstructions remains difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice and circum-Arctic land ice feedbacks on the modeled climate of the Beringian interior. Simulations accounting for climate–vegetation–land-surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on northeast Asian temperature during the warmth of stages 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic Ocean does have some effect on Lake El'gygytgyn's regional climate, but the exceptional warmth of MIS 11c remains enigmatic compared to the modest orbital and greenhouse gas forcing during that interglacial."

Extract: "The timing of significant warming in the circum-Arctic can be linked to major deglaciation events in Antarctica, demonstrating possible interhemispheric linkages between the Arctic and Antarctic climate on glacial–interglacial timescales, which have yet to be explained."


Julie Brigham-Grette et. al. (2013), “Pliocene Warmth, Polar Amplification, and Stepped Pleistocene Cooling Recorded in NE Arctic Russia”,  Science, Page 1 / 10.1126/science.1233137

https://dl.dropboxusercontent.com/u/75831381/Brigham-Grette.pdf


Abstract: “Understanding the evolution of Arctic polar climate from the protracted warmth of the middle Pliocene into the earliest glacial cycles in the Northern Hemisphere has been hindered by the lack of continuous, highly resolved Arctic time series. Evidence from Lake El’gygytgyn, NE Arctic Russia, shows that 3.6-3.4 million years ago, summer temperatures were ~8°C warmer than today when pCO2 was ~400 ppm. Multiproxy evidence suggests extreme warmth and polar amplification during the middle Pliocene, sudden stepped cooling events during the Pliocene-Pleistocene transition, and warmer than present Arctic summers until ~2.2 Ma, after the onset of Northern Hemispheric glaciation. Our data are consistent with sea-level records and other proxies indicating that Arctic cooling was insufficient to support large-scale ice sheets until the early Pleistocene.”

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The linked reference address how the collapse of the WAIS can alter oceanic and atmospheric patterns, leading to Super Interglacial conditions:

Flavio Justino, Douglas Lindemann, Fred Kucharski, Aaron Wilson, David Bromwich, and Frode Stordal (2017), "Oceanic response to changes in the WAIS and astronomical forcing during the MIS31 superinterglacial", Clim. Past, 13, 1081–1095, https://doi.org/10.5194/cp-13-1081-2017

https://www.clim-past.net/13/1081/2017/cp-13-1081-2017.pdf

Abstract: "Marine Isotope Stage 31 (MIS31, between 1085 and 1055 ka) was characterized by higher extratropical air temperatures and a substantial recession of polar glaciers compared to today.  Paleoreconstructions and model simulations have increased the understanding of the MIS31 interval, but questions remain regarding the role of the Atlantic and Pacific oceans in modifying the climate associated with the variations in Earth’s orbital parameters. Multi-century coupled climate simulations, with the astronomical configuration of the MIS31 and modified West Antarctic Ice Sheet (WAIS) topography, show an increase in the thermohaline flux and northward oceanic heat transport (OHT) in the Pacific Ocean.  These oceanic changes are driven by anomalous atmospheric circulation and increased surface salinity in concert with a stronger meridional overturning circulation (MOC). The intensified northward OHT is responsible for up to 85% of the global OHT anomalies and contributes to the overall reduction in sea ice in the Northern Hemisphere (NH) due to Earth’s astronomical configuration. The relative contributions of the Atlantic Ocean to global OHT and MOC anomalies are minor compared to those of the Pacific.  However, sea ice changes are remarkable, highlighted by decreased (increased) cover in the Ross (Weddell) Sea but widespread reductions in sea ice across the NH."

Extract: "Based on coupled climate simulations performed under present day and boundary conditions representative of Marine Isotope Stage 31 (MIS31), our analyses provide evidence that under MIS31 climate conditions there was a remarkable reduction in sea ice distribution across the NH due to the astronomical configuration of that epoch. This contrasts with increases in sea ice area across the SH. The climate response to collapsing the WAIS is prominent in the vicinity of the Antarctic continent, whereas the effect of modification in the Earth orbital configuration extends worldwide.

It has furthermore been demonstrated that the MIS31 interglacial experienced significant changes in the Meridional Overturning Circulation (MOC). In the Atlantic, increases in the MOC are related to an intensified westerly atmospheric flow in the northern North Atlantic, leading to strong convective mixing. The main convection sites in MIS31 have also been shifted poleward compared to the control simulation (CTR) in concert with changes in the position of the meridional thermal gradient."

Also, it would be nice if anyone attending the Fall AGU Meeting in New Orleans could report back on:

Julie Brigham-Grette, Robert M Deconto, Rajarshi Roychowdhury, Greg de Wet, Benjamin Andrew Keisling, Martin Melles and Pavel Minyuk (2017), "Too Warm, Two Poles: Super Interglacial Teleconnections and Possible Dual Pole Ice Sheet Stability", AGU Fall Meeting

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The linked references all provides evidence supporting Hansen's ice-climate interaction mechanism associated with ice mass loss from the WAIS:

Pepijn Bakker et al, Centennial-scale Holocene climate variations amplified by Antarctic Ice Sheet discharge, Nature (2016). DOI: 10.1038/nature20582

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature20582.html

Abstract: "Proxy-based indicators of past climate change show that current global climate models systematically underestimate Holocene-epoch climate variability on centennial to multi-millennial timescales, with the mismatch increasing for longer periods. Proposed explanations for the discrepancy include ocean–atmosphere coupling that is too weak in models, insufficient energy cascades from smaller to larger spatial and temporal scales, or that global climate models do not consider slow climate feedbacks related to the carbon cycle or interactions between ice sheets and climate. Such interactions, however, are known to have strongly affected centennial- to orbital-scale climate variability during past glaciations, and are likely to be important in future climate change. Here we show that fluctuations in Antarctic Ice Sheet discharge caused by relatively small changes in subsurface ocean temperature can amplify multi-centennial climate variability regionally and globally, suggesting that a dynamic Antarctic Ice Sheet may have driven climate fluctuations during the Holocene. We analysed high-temporal-resolution records of iceberg-rafted debris derived from the Antarctic Ice Sheet, and performed both high-spatial-resolution ice-sheet modelling of the Antarctic Ice Sheet and multi-millennial global climate model simulations. Ice-sheet responses to decadal-scale ocean forcing appear to be less important, possibly indicating that the future response of the Antarctic Ice Sheet will be governed more by long-term anthropogenic warming combined with multi-centennial natural variability than by annual or decadal climate oscillations."

&

Johannes Sutter, Paul Gierz, Klaus Grosfeld, Malte Thoma, Gerrit Lohmann (2016), "Ocean temperature thresholds for Last Interglacial West Antarctic Ice Sheet collapse", Geophysical Research Letters, DOI: 10.1002/2016GL067818

http://onlinelibrary.wiley.com/doi/10.1002/2016GL067818/full

Abstract: "The West Antarctic Ice Sheet (WAIS) is considered the major contributor to global sea level rise in the Last Interglacial (LIG) and potentially in the future. Exposed fossil reef terraces suggest sea levels in excess of 7 m in the last warm era, of which probably not much more than 2 m are considered to originate from melting of the Greenland Ice Sheet. We simulate the evolution of the Antarctic Ice Sheet during the LIG with a 3-D thermomechanical ice sheet model forced by an atmosphere-ocean general circulation model (AOGCM). Our results show that high LIG sea levels cannot be reproduced with the atmosphere-ocean forcing delivered by current AOGCMs. However, when taking reconstructed Southern Ocean temperature anomalies of several degrees, sensitivity studies indicate a Southern Ocean temperature anomaly threshold for total WAIS collapse of 2–3°C, accounting for a sea level rise of 3–4 m during the LIG. Potential future Antarctic Ice Sheet dynamics range from a moderate retreat to a complete collapse, depending on rate and amplitude of warming."

&

Julien P. Nicolas et. al. (2017), "January 2016 extensive summer melt in West Antarctica favoured by strong El Nino", Nature Communications, DOI: 10.1038/ncomms15799

http://www.ccpo.odu.edu/~klinck/Reprints/PDF/nicolasNatComm17.pdf

Abstract: "Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Nino event. The increase in the number of extreme El Nino events projected for the twenty-first century could expose the WAIS to more frequent major melt events."

See also
William R. Frey & Jennifer E. Kay (2017), "The influence of extratropical cloud phase and amount feedbacks on climate sensitivity", Climate Dynamics; pp 1–20, doi:10.1007/s00382-017-3796-5

https://link.springer.com/article/10.1007%2Fs00382-017-3796-5?utm_content=bufferfdbc0&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Global coupled climate models have large long-standing cloud and radiation biases, calling into question their ability to simulate climate and climate change. This study assesses the impact of reducing shortwave radiation biases on climate sensitivity within the Community Earth System Model (CESM). The model is modified by increasing supercooled cloud liquid to better match absorbed shortwave radiation observations over the Southern Ocean while tuning to reduce a compensating tropical shortwave bias. With a thermodynamic mixed-layer ocean, equilibrium warming in response to doubled CO2 increases from 4.1 K in the control to 5.6 K in the modified model. This 1.5 K increase in equilibrium climate sensitivity is caused by changes in two extratropical shortwave cloud feedbacks. First, reduced conversion of cloud ice to liquid at high southern latitudes decreases the magnitude of a negative cloud phase feedback. Second, warming is amplified in the mid-latitudes by a larger positive shortwave cloud feedback. The positive cloud feedback, usually associated with the subtropics, arises when sea surface warming increases the moisture gradient between the boundary layer and free troposphere. The increased moisture gradient enhances the effectiveness of mixing to dry the boundary layer, which decreases cloud amount and optical depth. When a full-depth ocean with dynamics and thermodynamics is included, ocean heat uptake preferentially cools the mid-latitude Southern Ocean, partially inhibiting the positive cloud feedback and slowing warming. Overall, the results highlight strong connections between Southern Ocean mixed-phase cloud partitioning, cloud feedbacks, and ocean heat uptake in a climate forced by greenhouse gas changes."

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Regarding potential impacts of Hansen's ice-climate feedback and abrupt SLR this century, in recent posts I have cited a good amount of paleo evidence that ice-climate feedback can contribute to bipolar super interglacials (with high climate sensitivity) and that DeConto & Pollard 2016's model have demonstrated the possibility of up to 2.65 m SLR this century and they are working to publish finding of even higher levels of ASLR.  Furthermore, as DeConto & Pollard have demonstrated that the WAIS's potential contributions to SLR this century are highly influence by the potential increases in GMSTA due to hydrofracturing, in my last post I cited that William R. Frey & Jennifer E. Kay (2017) indicates the potential impact if current ESMs have the ice content of clouds wrong and that Julien P. Nicolas et. al. (2017) demonstrate that periods of strong El Nino like conditions favor strong surface ice melting in the WAIS (see the first attached image, while the second attached image indicates how combinations of SAM and ENSO work to telecommunicate atmospheric energy from the Tropical Pacific to West Antarctica).  Furthermore, Graeme Stephens et. al. (2017), "CloudSat and CALIPSO within the A-Train: Ten years of actively observing the Earth system", BAMS, https://doi.org/10.1175/BAMS-D-16-0324.1, indicates that the observed net cloud feedback is higher than previously assumed.

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-16-0324.1?utm_content=bufferebbb9&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer
or
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-16-0324.1

Also, the linked reference studies dynamical cloud response to aerosol forcing and concludes: "The dynamical cloud response is closely linked to the meridional displacement of the Hadley Cell that, in turn, is driven by changes in the cross-equatorial energy transport. In this way, the dynamical cloud changes act as a positive feedback on the meridional displacement of the Hadley Cell, roughly doubling the projected changes in cross-equatorial energy transport compared to that from the microphysical changes alone."

Brian Soden and Eui-Seok Chung (2017), "The Large Scale Dynamical Response of Clouds to Aerosol Forcing" Journal of Climate", https://doi.org/10.1175/JCLI-D-17-0050.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0050.1?utm_content=bufferaa6b0&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "We use radiative kernels to quantify the instantaneous radiative forcing of aerosols and the aerosol-mediated cloud response in coupled ocean-atmosphere model simulations under both historical and future emission scenarios. The method is evaluated using matching pairs of historical climate change experiments with and without aerosol forcing and accurately captures the spatial pattern and global mean effects of aerosol forcing. We show that aerosol-driven changes in the atmospheric circulation induce additional cloud changes. Thus, the total aerosol-mediated cloud response consists of both local microphysical changes and non-local dynamical changes that are driven by hemispheric asymmetries in aerosol forcing. By comparing coupled and fixed-SST (sea surface temperature) simulations with identical aerosol forcing we isolate the relative contributions of these two components, exploiting the ability of prescribed SSTs to also suppress changes in the atmospheric circulation. The radiative impact of the dynamical cloud changes are found to be comparable in magnitude to that of the microphysical cloud changes, and act to further amplify the inter-hemispheric asymmetry of the aerosol radiative forcing. The dynamical cloud response is closely linked to the meridional displacement of the Hadley Cell that, in turn, is driven by changes in the cross-equatorial energy transport. In this way, the dynamical cloud changes act as a positive feedback on the meridional displacement of the Hadley Cell, roughly doubling the projected changes in cross-equatorial energy transport compared to that from the microphysical changes alone."

In this regards, I provide the third image that shows how increased Equatorial Energy can move the Hadley Cells poleward thus increasing ECS; and the fourth image that indicates that since the recent series of strong El Ninos in 1982-83 and 1997-98 (not to mention 2015-16), Arctic Amplification has been increasing rapidly.

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As deep convective clouds (DCC) are a significant positive feedback mechanism, the fact that they increase rapidly with warming of the tropical ocean, is a major consideration of Hansen's ice-climate feedback mechanism, because freshwater hosing of the Southern Ocean will slow the thermohaline circulation of the great ocean conveyor-belt current circulation; which will back-up ocean surface heat in the tropical oceans (see also, the "Hansen et al paper 3+ meters SLR by 2100" thread).

In this regards, the first two attached images by Sherwood et al 2014 shows how deep atmospheric convection in the Equatorial Pacific might mean that ECS is between 3 & 5C.  The middle panel of the third image shows findings from Andrew's 2015 Ringberg presentation that support Sherwood's findings on ECS.  Finally, the fourth attached image from Hansen et al 2011 indicates how climate response rates that are traditionally assumed to be slow (frequently as they are associated with ocean responses) can act in a fast mode due to such considerations as ENSO climate attractors and the fact that the oceans have absorbed about 90% of all anthropogenic heat since 1750 and are thus already warmer than previously assumed.

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My recent posts raise the question of whether NOAA's current SLR guidance errs on the side of least drama by assuming that the WAIS may not begin its main phase collapse too soon, and that its collapse may not proceed too fast.

In this regards, the first image shows NOAA's prior official guidance (from Parris et al. December 2014) for SLR through 2100; where the curve marked Highest - 2m was appropriate for use in the design of new coastal infrastructure with a design life of comparable age.  However, approximately 2 years later, in January 2017, NOAA increased (from 2.0 meters) their upper bound for the design of significant coastal infrastructures for sea level rise by 2100 up to 2.5 +/- 0.15m (it is primarily because of their concern about WAIS stability), indicated by the second attached image.

Sweet, W.V., R.E. Kopp, C.P. Weaver, J. Obeysekera, R.M. Horton, E.R. Thieler and C. Zervas (2017) "Global and Regional Sea Level Rise Scenarios for the United States".



https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf

Such SLR design guidance for coastal infrastructure assumes a 'fat-tailed' PDF as indicated by Richard Alley's third attached image, which in-turn assumes that the 'ice plug' illustrated in panels 2 and 3 of the fourth attached image does not fail before the 2050 to 2060 timeframe, and that the cliff failure illustrated in the 5th panel of the fourth image does not proceed faster than assumed by DeConto & Pollard 2016.

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As a follow-on to my last post, the first three attached images come from an analysis of the consequences of the loss of the 'ice plug' for the Wilkes Basin in East Antarctica, w.r.t. to potential contributions to future SLR.  However, as the EAIS is projected to provide relatively small contributions to SLR by 2100, for the next several posts I will focus primarily on potential reasons why the marine glaciers in the critical Amundsen Sea Embayment, ASE (see the fourth attached image), might lose their 'ice plugs' sooner than the 2050-2060 timeframe as assumed by DeConto & Pollard (2016)

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The first image indicates how quickly the ASE ice shelves have retreated in recent years due primarily to oceanic basal ice melting, without any contribution from DeConto & Pollards hydrofracturing mechanism.  The second & third images illustrate how the Thwaites Eastern Ice Shell is still pinned by two offshore pinnacles, and that at the base of the old Thwaite Ice Tongue (now largely degraded) there is a relatively deep trough in the seafloor that communicates directly to the Byrd Subglacial Basin, BSB, and the subglacial network of drainage channels and interconnected subglacial lakes.  The fourth image shows that sometime between January 2012 and January 2013 the underwater cavity in the deep trough in the seafloor leading to the BSB, collapsed and the adjoining subglacial lakes drained, causing the Thwaites Ice Tongue to degrade and the ice surface above the cavity to drop by about 6m in one year.

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The first image shows the surface of the ice above the collapsed cavity in the trough leading to the BSB in 2013, indicating that the 6m drop in surface elevation created a network of crevasses that sub-divided small icebergs that are waiting to float away as soon as the pinned (on pinnacle 2) ice mélange (that used to be the Thwaites Ice Tongue) is sufficiently cleared (say due to basal ice melting).  The second image shows ice surface depressions caused by the drainage of upstream Thwaites subglacial lakes between June 2013 and January 2014, that contributed meltwater flow through the trough (leading to the BSB) that has accelerated the degradation of the ice mélange.  The third image illustrate how before 2013 many 'experts' were hoping that pinning points in the Thwaites Gateway would slow ice mass loss in this area; however, the fourth image from the end of 2013 indicates that the assumed pinning points in the Thwaites Gateway were about 100m deeper than previously assumed; which meant that they would not act as effective pinning points (say for the small icebergs in the trough leading to the BSB).

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The first attached image shows the location of the four subglacial lakes that drained from June 2013 to January 2014 in the second image of my last post.  The second and third attached images, in this current post, show how channelized the basal drainage network is in the Thwaites Gateway and how swamp-like it is for most of the BSB.  This nature of the basal drainage system may lead to an accelerated clearing of the small icebergs in the trough within the next 20-years (by 2037) when the lakes fill back up and discharge again directly into the trough.  Once the trough is cleared of icebergs the exposed cliff face will be subject to buoyancy driven convection that can help destabilize the cliff face as illustrated the fourth attached image.

See also:

Smith et. al. (2017), "Connected subglacial lake drainage beneath Thwaites Glacier, West Antarctica", The Cryosphere, 11, 451–467, doi:10.5194/tc-11-451-2017

http://www.the-cryosphere.net/11/451/2017/tc-11-451-2017.pdf

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The first accompanying figure 4a (from Purkey & Johnson 2013) warm, circumpolar deep water, CDW, has (prior to 2013) surged from the north southward toward the Antarctic continental shelves.  This is due both to an increased in the volume of CDW and due to an increase in the circumpolar westerly wind velocities due to the anthropogenically created ozone hole over Antartica.

The second image shows that in addition to the Antarctic Circumpolar Current in the Southern Ocean, there are three major gyres that can help direct warm CDW towards various continental shelves around Antarctica including into the ASE (as indicated by the last two attached images, that show warm CDW advected through deep seafloor channels in the ASE continental shelf and among other places directly beneath both the Pine Island Ice Shelf and the Thwaites Ice Shelf/Tongue).  This advection of oceanic heat content into the ASE is amplified during strong El Nino events due to interactions of currents with the Amundsen Sea Low, ASL (and I note that global warming is increasing the frequency of strong El Nino events faster than previously assumed).

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The first attached image illustrates conceptually how the warm CDW can accelerate the progressive collapse of ASE ice shelfs such as the recent calving of the Pine Island Ice Shelf shown in the second attached image.  This second image also shows how the Southwest Tributary Ice Shelf looks like it is susceptible to a major calving soon, which could accelerate the ice flow in the Southwest Tributary Glacier, which in turn could accelerate ice flow in the Thwaites Glacier by reducing shear on its eastern shear margin.

The third image comes from an analysis of the rate of cliff face retreat for the Jakobshavn Glacier, in Greenland, in it illustrates that cliff failures can be accelerated by low basal drag, low ice viscosity, and high gravitational driving force.  This is highly relevant to cliff failures in the WAIS and particularly for Thwaites Glacier where both the basal drag and the basal ice viscocity are low in the BSB due to high geothermal heat flux, and the gravitational driving force can be sustained in the next few decades by projected high snowfall rates over the high elevations in Western Antarctica.  Finally, the fourth attached image shows a profile view through the Thwaites Glacier (from 2006).  This image shows that when the current grounding line retreats by about 70km, an assumed vertical ice cliff face would extend from -1km to +1km; which would be very susceptible to a cliff failure.  This is particularly relevant to the stability of the ice in the trough leading to the BSB which may have unbuttressed ice cliffs as early as 2040, even without any hydrofracturing as postulated by DeConto and Pollard 2016.

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As cliff failures inducing increasing ice mass loss from the WAIS and from the BSB in particular, glacial isostatic adjustment, GIA, will cause the local seafloor to rebound first due to elastic rebound and more slowly due to mantle flow.  Here I note that the lithosphere in West Antarctica is particularly thin, and the magma in the mantle have particularly low viscosity, and there is a pre-existing subglacial, West Antarctic Rift System, WARS, as indicated in the second attached image.  Furthermore, scientists recently discovered 91 new volcanoes in WARS that are in addition to 47 volanoes already known about in WARS.

https://www.theguardian.com/world/2017/aug/12/scientists-discover-91-volcanos-antarctica

Also I note that the linked reference discusses a paleo event where synchronous halogen-rich volcanic eruptions in West Antarctica about 17.7 kya abruptly changed global climate by causing a stratospheric ozone depletion over Antarctica, in a manner not dissimilar to the ozone hole created over Antarctica circa the 1970's due to anthropogenic HFC emissions.  This shows not only the importance of accounting for the geographic distribution of changes in atmospheric ozone concentrations; but also that we have already triggered Hansen's ice-climate feedback mechanism that can cause abrupt climate change within decades of being triggered:

Joseph R. McConnell et al (2017), "Synchronous volcanic eruptions and abrupt climate change ∼17.7 ka plausibly linked by stratospheric ozone depletion", PNAS, vol. 114 no. 38 10035–10040, doi: 10.1073/pnas.1705595114

http://www.pnas.org/content/114/38/10035.short?utm_content=bufferc48cb&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Glacial-state greenhouse gas concentrations and Southern Hemisphere climate conditions persisted until ∼17.7 ka, when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the Southern Hemisphere, with many changes ascribed to a sudden poleward shift in the Southern Hemisphere westerlies and subsequent climate impacts. We used high-resolution chemical measurements in the West Antarctic Ice Sheet Divide, Byrd, and other ice cores to document a unique, ∼192-y series of halogen-rich volcanic eruptions exactly at the start of accelerated deglaciation, with tephra identifying the nearby Mount Takahe volcano as the source. Extensive fallout from these massive eruptions has been found >2,800 km from Mount Takahe. Sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface UV radiation indicate that the eruptions led to stratospheric ozone depletion. Rather than a highly improbable coincidence, circulation and climate changes extending from the Antarctic Peninsula to the subtropics—similar to those associated with modern stratospheric ozone depletion over Antarctica—plausibly link the Mount Takahe eruptions to the onset of accelerated Southern Hemisphere deglaciation ∼17.7 ka."

The third image shows that ice mass loss from the WAIS results in a SLR fingerprint with greater sea level rises near the Bering Strait and less sea level rise near the Barents Sea; which will flush warm Pacific water through the Bering Strait where it will further drive Arctic Amplification; as will a projected increase of ocean heat flux from the North Atlantic into the Arctic Sea due to a projected anthropogenic increase in the AMOC circa 2035 to 2040.

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The linked reference uses New Orleans as a 'canary in a coal mine' to evaluate coastal flooding risk associated with deep uncertainties from abrupt ice mass loss from the WAIS, and they find that for the next fifty years the biggest risks come from increased storm surge from more frequent strong hurricanes (see Hansen's 'Storms of My Grandchildren'); however, this research does not evaluate the risks of flooding from increased hurricane rainfall such as occurred during Hurricane Harvey.

Tony E. Wong & Klaus Keller (20 September 2017), "Deep Uncertainty Surrounding Coastal Flood Risk Projections: A Case Study for New Orleans", Earth's Future, DOI: 10.1002/2017EF000607

http://onlinelibrary.wiley.com/doi/10.1002/2017EF000607/abstract

In this regards, the first attached image indicates that the frequency of strong hurricanes (of Katrina magnitude or greater) will increase two to seven fold for a 1C increase in GMSTA.

The second attached image present field observations for the correlation of ice mass loss events in the SH and NH that support the bipolar seesaw over the past 140,000 years; which further validates Hansen's ice-climate feedback mechanism, as does the third attached image that shows how during the faux hiatus period the over flow of warm water from the Western Tropical Pacific Warm Water Pool, flowed past Western Australia to feed more warm water into the Southern Ocean's Circumpolar Current.

Finally, the fourth attached image shows that the WAIS is currently contributing to 0.38 mm/yr of SLR per the GRACE satellite, indicating that oceanic driven melting is actively melting various ice plugs in West Antarctica, thus actively setting up conditions to support possible future ice cliff failures of WAIS marine glaciers.

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Needless to say, most over my recent series of posts on the stability of the WAIS assume BAU forcing thru at least 2040 and an ECS of about 3.1C.  If ECS is between 4 & 5C, and if deforestation and agriculture change bio carbon sinks into carbon sources then GMSTA might reach 2C by 2035 and DeConto & Pollard's 2016 projections might indicated hyrofracturing of the key ASE ice shelves starting circa 2040; thus increasing the probability of a 3m contribution to SLR from the WAIS by 2100.

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The linked article indicates that in the past the Earth's climate has changed abruptly (i.e. changed within a few years, particularly during periods of freshwater hosing into the ocean at high latitudes), and we acting like test rats in a one of a kind anthropogenic test on the climate:

Title: "Humans experimenting with climate's 'playing nice'"

https://www.yaleclimateconnections.org/2017/10/humans-experimenting-with-climates-playing-nice/

Extract: "But he is concerned that human activities could be “tipping the climate into an intermediate period of climate changes…. We can face a climate change that happens just as fast as the financial crisis,” Steffensen says. In that case, agricultural activity worldwide could be adversely affected … “the weather will change, and it will not change back” quickly.

“We don’t know where the threshold is,” Steffensen says of the ongoing human “experiment” with climate change. “But we are rats inside the experiment.”"

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The linked reference concludes: "... the specific equilibrium climate sensitivity which considers radiative forcing of CO2 and land ice sheet (LI) albedo, S[CO2,LI], is larger during interglacial states than during glacial conditions by more than a factor two."  This is not good news:

Peter Koehler, Lennert Stap, Anna von der Heydt, Bas de Boer, Roderik, S. W. van de Wal & Jonah Bloch-Johnson (4 October 2017), "A state-dependent quantification of climate sensitivity based on paleo data of the last 2.1 million years", Paleoceanography, DOI: 10.1002/2017PA003190

http://onlinelibrary.wiley.com/doi/10.1002/2017PA003190/abstract?utm_content=bufferc4dad&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "The evidence from both data and models indicates that specific equilibrium climate sensitivity S[X] — the global annual mean surface temperature change (ΔTg) as a response to a change in radiative forcing X (ΔR[X]) — is state-dependent. Such a state dependency implies that the best fit in the scatter plot of ΔTg versus ΔR[X] is not a linear regression, but can be some non-linear or even non-smooth function. While for the conventional linear case the slope (gradient) of the regression is correctly interpreted as the specific equilibrium climate sensitivity S[X], the interpretation is not straightforward in the non-linear case. We here explain how such a state-dependent scatter plot needs to be interpreted, and provide a theoretical understanding — or generalization — how to quantify S[X] in the non-linear case. Finally, from data covering the last 2.1 Myr we show that — due to state dependency — the specific equilibrium climate sensitivity which considers radiative forcing of CO2 and land ice sheet (LI) albedo, S[CO2,LI], is larger during interglacial states than during glacial conditions by more than a factor two."

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Here is an Australian op/ed piece on the scientific understatement of climate change risks:

Title: "Hostage to myopic self-interest: climate science is watered down under political scrutiny"

https://www.theguardian.com/commentisfree/2017/sep/11/hostage-to-myopic-self-interest-climate-science-is-watered-down-under-political-scrutiny

Extract: "Today, despite the diplomatic triumph of the Paris climate agreement, debate around climate change policy has never been more dysfunctional, indeed Orwellian, particularly in Australia.

In his book Nineteen Eighty-Four, George Orwell describes a double-speak totalitarian state where most of the population accepts “the most flagrant violations of reality, because they never fully grasped the enormity of what was demanded of them, and were not sufficiently interested in public events to notice what was happening. By lack of understanding they remained sane.”

Orwell could have been writing about climate change and policymaking."

[jai mitchell]

I posted this over at forcing but wanted to share it here as well, it shows the impact that SO2 uncertainty has on potential ECS ranges and the resulting temperatures that would occur if we held forcing (GHG abundances) at today's values, also the potential warming that would occur due to SO2 emissions halting (see how high up the red line goes. . .) then other impacts of SLCP reduction centiennial forcing, not sure what that is exactly and carbon capture of the oceans, of course they do not include carbon cycle or arctic albedo feedbacks in these projections.

The big note here is the uncertainty in SO2 impacts on global temperatures and that, at today's forcing values, and in the absence of SO2 we could be locked in well over 3C of warming, though this is an outlier.

[AbruptSLR]

While I appreciate climate scientist's fight against distorted climate news reports; the reality that policymakers need to accept is that this situation contributes to the ESLD information presented by consensus climate science.  However, as policymakers seem to show little inclination to address the reality of the current ESLD situation (perhaps because the current global economy is currently so dependent on fossil fuels and big agriculture); I recommend that common citizens should prepare for a climate change triggered socio-economic collapse in the approximately the 2045 to 2060 timeframe:

Title: "Rise of Distorted News Puts Climate Scientists on Their Guard"

https://eos.org/features/rise-of-distorted-news-puts-climate-scientists-on-their-guard?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz100617

Extract: "Wary of misleading coverage, some climate researchers are avoiding publicizing results. Others prepare countermeasures to anticipate and combat skewed media reports."

[AbruptSLR]

jai posted this in the Carbon Cycle thread, but I think that it is also relevant to this thread:

Melillo, J.M. et al (2017) Long-Term Pattern and Magnitude of Soil Carbon Feedback to the Climate System in a Warming World. Science, http://science.sciencemag.org/content/358/6359/101

https://scienmag.com/carbon-feedback-from-forest-soils-will-accelerate-global-warming-26-year-study-projects/

WOODS HOLE, Mass. — After 26 years, the world's longest-running experiment to discover how warming temperatures affect forest soils has revealed a surprising, cyclical response: Soil warming stimulates periods of abundant carbon release from the soil to the atmosphere alternating with periods of no detectable loss in soil carbon stores. Overall, the results indicate that in a warming world, a self-reinforcing and perhaps uncontrollable carbon feedback will occur between forest soils and the climate system, adding to the build-up of atmospheric carbon dioxide caused by burning fossil fuels and accelerating global warming. The study, led by Jerry Melillo, Distinguished Scientist at the Marine Biological Laboratory (MBL), appears in the October 6 issue of Science.

Edit, see also: Title: "There’s a Climate Bomb Under Your Feet"

https://www.bloomberg.com/news/articles/2017-10-06/there-s-a-climate-change-bomb-under-your-feet

[AbruptSLR]

The linked reference concludes: "An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train".  This research confirms that a fresh water hosing event from the WAIS can impact the Northern Hemisphere within months, via the bipolar seesaw mechanism.

Turney et al (2017), "Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial", Nature Communications, doi:20.2038/s41467-017-00577-6

https://www.nature.com/articles/s41467-017-00577-6

[AbruptSLR]

The linked reference concludes: "An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train".  This research confirms that a fresh water hosing event from the WAIS can impact the Northern Hemisphere within months, via the bipolar seesaw mechanism.

Turney et al (2017), "Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial", Nature Communications, doi:20.2038/s41467-017-00577-6

https://www.nature.com/articles/s41467-017-00577-6

See also:

https://theconversation.com/how-antarctic-ice-melt-can-be-a-tipping-point-for-the-whole-planets-climate-83776

[AbruptSLR]

The linked reference discusses the Ross Sea Dipole, which can contribute to abrupt changes in surface temperature, precipitation and sea ice extent in the Ross, Amundsen and Bellingshausen seas.  CMIP5 projections do not account very well for the influence of the Ross Sea Dipole, thus raising climate risks and uncertainties especially with regard to the potential for abrupt ice mass loss from the WAIS.

For example, the Southern Annular Mode, SAM recently shifted to a strongly negative condition, which when combined with El Nino conditions (such as the 2015-16 Super El Nino event) work together with the Amundsen Sea Low, ASL, to advect warm circumpolar deep water, CDW, into the Amundsen Sea Embayment, ASE; which, can accelerate the degradation of the ice shelves for the critical marine glaciers in this area.

Bertler et al (2017), "The Ross Sea Dipole - Temperature, Snow Accumulation and Sea Ice Variability in the Ross Sea Region, Antarctica, over the Past 2,700 Years", Clim. Past Discuss., https://doi.org/10.5194/cp-2017-95

https://www.clim-past-discuss.net/cp-2017-95/cp-2017-95.pdf

Abstract: "High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979-2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with increased snow accumulation and perhaps decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings."

Extract: "The Ross Sea region is a climatologically sensitive region that is exposed to tropical and mid-latitude climate drivers. In recent decades, SAM and PSA2 teleconnections lead to opposing effects in the eastern and western Ross Sea region with respect to meridional heat flux, surface wind fields (Marshall and Thompson, 2016), and sea ice extent (Stammerjohn et al., 2008)
exhibiting a Ross Sea Dipole. The ASL deepens during combined positive SAM and La Niña events, and weakens during negative SAM and El Niño events. Such interactions have far reaching implications on the regional atmospheric and ocean circulations and sea ice (Turner et al., 2015, Raphael et al., 2016). Additionally, a negative (positive) IPO leads to cooler (warmer) SSTs in the Ross, Amundsen and Bellingshausen seas and has the potential to strengthen (in phase) or weaken (out of phase) the ENSO teleconnection (Henley et al., 2015). Furthermore, the phasing and strength of ENSO events and SAM have been shown to be dependent (Fogt and Bromwich, 2006).

Our data suggest that these dynamically linked climate patterns led to significant and abrupt changes in the past with implications for regional interpretations of trends, including temperature, mass balance and SIE."

[AbruptSLR]

The linked commentary concludes that recent findings indicate that: "… global cloud feedback is likely positive".  The attached image shows the global average cloud feedbacks and their impact on climate sensitivity; which I note that Hansen's ice-climate feedback is not included in this assessment, and thus the most valid conclusion from this study is that ECS currently is mostly likely not less than 3C.

Zelinka et al (2017), "Clearing clouds of uncertainty', Nature Climate Change, doi: 10.1038/nclimate3402

http://www.nature.com/nclimate/journal/v7/n10/full/nclimate3402.html