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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #500 on: February 04, 2015, 04:57:32 PM »
As some would point out, for at least the past 50 years (when President LBJ first warned Congress about global warming risks) society has been well notified about climate change risks; however, in all those decades (as pointed out in the linked reference below) anthropogenic GHG emissions have tracked the high end of the current (AR5) RCP emission scenarios.  In any reasonably well constructed scientific investigation, the input radiative forcing scenarios should track the middle emissions track-record and not the high end.  With the world GDP estimated to grow at 3.5% in 2015, and with higher than average GDP growth rates in most of Africa and South Asia, societies chances of reducing (unlike our chances of accelerating) the growth in anthropogenic GHG emissions before 2020 are not good.  We need to recognize that the earlier and the stronger society pushes anthropogenic radiative forcing, the greater the chances that non-linear positive feedback mechanisms will activate well before 2100, thus compounding the problem of following the high end of the RCP scenarios:

P. Friedlingstein, R. M. Andrew, J. Rogelj, G. P. Peters, J. G. Canadell, R. Knutti, G. Luderer, M. R. Raupach, M. Schaeffer, D. P. van Vuuren & C. Le Quéré, (2014), "Persistent growth of CO2 emissions and implications for reaching climate targets", Nature Geoscience, Volume: 7, Pages: 709–715, doi:10.1038/ngeo2248


http://www.nature.com/ngeo/journal/v7/n10/full/ngeo2248.html

Abstract: "Efforts to limit climate change below a given temperature level require that global emissions of CO2 cumulated over time remain below a limited quota. This quota varies depending on the temperature level, the desired probability of staying below this level and the contributions of other gases. In spite of this restriction, global emissions of CO2 from fossil fuel combustion and cement production have continued to grow by 2.5% per year on average over the past decade. Two thirds of the CO2 emission quota consistent with a 2 °C temperature limit has already been used, and the total quota will likely be exhausted in a further 30 years at the 2014 emissions rates. We show that CO2 emissions track the high end of the latest generation of emissions scenarios, due to lower than anticipated carbon intensity improvements of emerging economies and higher global gross domestic product growth. In the absence of more stringent mitigation, these trends are set to continue and further reduce the remaining quota until the onset of a potential new climate agreement in 2020. Breaking current emission trends in the short term is key to retaining credible climate targets within a rapidly diminishing emission quota."
« Last Edit: February 04, 2015, 05:30:10 PM by AbruptSLR »
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Steven

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Re: Conservative Scientists & its Consequences
« Reply #501 on: February 04, 2015, 08:52:11 PM »
"the daily sea ice area data are weighted in such a way that their weight (i.e., their relative importance) has a peak at the summer solstice (21 December in the SH), and gradually decreases away from that date."

Is there latitude dependence in the weighting ? ie, a patch of sea ine at 50 S is not illuminated the same as one at 67S

sidd

Here is a graph showing the weights as a function of time, for the Southern Hem.  As mentioned, these weights are based on the (top-of-atmosphere) insolation at latitudes 65-70°S.  65°S was used for September, 70°S for February, and for the rest of the year a combination of these 2 latitudes, in line with the annual cycle of expansion/retreat of the sea ice.  For the Northern Hemisphere, 80°N and 75°N were used. 

Clearly this approach is a rough approximation, and could be further refined for the spatial distribution of the sea ice.  But as discussed, the results are in good agreement with Tamino's numbers.

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #502 on: February 04, 2015, 11:50:58 PM »
The linked reference indicates that Transient Climate Response to cumulative Emissions (TCRE) varies with the rate of radiative forcing, and that TCRE is largest for either very low or very high rates of radiative forcing (which is not a good thing if we continue following a BAU pathway).

Krasting, J. P., J. P. Dunne, E. Shevliakova, and R. J. Stouffer (2014), "Trajectory sensitivity of the transient climate response to cumulative carbon emissions", Geophys. Res. Lett., 41, 2520–2527, doi:10.1002/2013GL059141.

http://onlinelibrary.wiley.com/doi/10.1002/2013GL059141/abstract

Abstract: "The robustness of Transient Climate Response to cumulative Emissions (TCRE) is tested using an Earth System Model (Geophysical Fluid Dynamics Laboratory-ESM2G) forced with seven different constant rates of carbon emissions (2 GtC/yr to 25 GtC/yr), including low emission rates that have been largely unexplored in previous studies. We find the range of TCRE resulting from varying emission pathways to be 0.76 to 1.04°C/TtC. This range, however, is small compared to the uncertainty resulting from varying model physics across the Fifth Coupled Model Intercomparison Project ensemble. TCRE has a complex relationship with emission rates; TCRE is largest for both low (2 GtC/yr) and high (25 GtC/yr) emissions and smallest for present-day emissions (5–10 GtC/yr). Unforced climate variability hinders precise estimates of TCRE for periods shorter than 50 years for emission rates near or smaller than present day values. Even if carbon emissions would stop, the prior emissions pathways will affect the future climate responses."

Furthermore, I provide the following link to a pdf of a PowerPoint presentation that explains the IPCC AR5's official thinking about the carbon budget, which uses the concept of TCRE (which is lower than using equilibrium climate sensitivity.  Furthermore, the IPCC's carbon budget concept ignores methane emissions from permafrost degradation under RCP8.5, and it ignore what are traditionally considered slow response feedback mechanisms (such as the collapse of the WAIS) that could actually happen this century following a BAU pathway:

http://www.climatechange2013.org/images/uploads/7_knutti13sed2_v1.pdf
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #503 on: February 05, 2015, 12:16:45 AM »
For those you want to put the influence of emissions rates on TCRE as discussed in Reply #502 by Krasting, J. P., J. P. Dunne, E. Shevliakova, and R. J. Stouffer (2014), "Trajectory sensitivity of the transient climate response to cumulative carbon emissions", Geophys. Res. Lett., 41, 2520–2527, doi:10.1002/2013GL059141.

I provide the attached CO2 equiv. emissions/year plot for the RCP scenarios per Riahi et al 2011 (who developed the RCP 8.5 scenario for the IPCC).  While our current carbon emission rate is above 10 GtC per year (or above 36.7 CO2 equiv. per year), which per Krasting et al 2014 has a relatively low TCRE; by about 2060 following RCP 8.5 the carbon emissions per year will be about 25 GtC per year (or about 91.75 CO2 equiv. per year), which had the highest TCRE evaluated by Krasting et al 2014.  Thus we may be living in a Fool's Paradise now but in a few decades we could be very sorry if we follow a BAU pathway.


Riahi, K., Rao, S., Krey, V., Cho, C., Chirkov, V., Fischer, G., Kindermann, G., Nakicenovic, N., and Rafaj, P. (2011); "RCP 8.5 - A scenario of comparatively high greenhouse gas emissions", Climatic Change (2011) 109:33-57, doi: 10.1007/s10584-011-0149-y.
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #504 on: February 05, 2015, 12:55:39 AM »
In my last post I said that CO2 equivalent emissions are currently about 37 GtCO2 eq per year; however, the attached image shows that in 2010 emissions were about 45 GtCO2 equiv. per year, and by now (2015) are probably getting closer to 50 GtCO2 equiv. (13.6 GtC) per year.
« Last Edit: February 05, 2015, 05:43:32 PM by AbruptSLR »
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jai mitchell

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Re: Conservative Scientists & its Consequences
« Reply #505 on: February 05, 2015, 04:48:17 AM »
These estimates most likely rely on u.s. EPA data which has now been shown to underestimate oil and gas methane emissions by almost 600%.  There is significant work being done on categorizing regional trace emission data and the implications are absolutely shocking!  Something like 10-14% of total U.S. annual methane sales volumes being emitted at extraction and distribution points.  The EPA recently reduced their estimates to 1.5%.  This would hardly cover the leakages being detected in municipal pipelines.
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Re: Conservative Scientists & its Consequences
« Reply #506 on: February 05, 2015, 05:11:28 AM »
In any reasonably well constructed scientific investigation, the input radiative forcing scenarios should track the middle emissions track-record and not the high end. 

Very wrong.  If a scientist group makes multiple predictions/estimations etc, some should be near the middle, some should be near the high end and some in the low end, with a small amount outside the range.  If this is not the case then the error range is being overestimated.
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Re: Conservative Scientists & its Consequences
« Reply #507 on: February 05, 2015, 05:58:30 AM »
"As mentioned, these weights are based on the (top-of-atmosphere) insolation at latitudes 65-70°S.  65°S was used for September, 70°S for February, and for the rest of the year a combination of these 2 latitudes, in line with the annual cycle of expansion/retreat of the sea ice.  For the Northern Hemisphere, 80°N and 75°N were used."

Thanks for the graph and the explanation.

sidd

Michael Hauber

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Re: Conservative Scientists & its Consequences
« Reply #508 on: February 05, 2015, 06:10:41 AM »
There are many different versions/generations of Earth Systems Models.  Thus saying that an earlier version of the Community Earth System Model, was included in CMIP5 does not mean that we have the final answer in hand from AR5.  Indeed, the ACME project lead by the DOE (and which will not be complete for another 10 years) is based on (started from) the Community Earth System Model, but will be further developed for the DOE mission and computers.

I am hoping that ACME will provide sufficient guidance to allow decision makers to make reasonably well informed decisions.  Until then (& even after then) we will need to make the best decisions that we can with the information that we have; understanding that decision makers with a high tolerance for risk will push the envelope perhaps further than what is good for the global community/environment.

But the models will not have changed very much from where they were for CMIP 5. 

And if a model did make a small change in this timeframe that mattered for climate sensitivity, or for transient climate response over the next 100 years then, either the scientists writing up the research are incompetent or party to a conspiracy of silence, or there is no interesting change and the scientist writes up about a detail such as a change in the Jetstream position as the most interesting result of the recent modelling study.
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Michael Hauber

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Re: Conservative Scientists & its Consequences
« Reply #509 on: February 05, 2015, 06:25:28 AM »

I agree that dying from gangrene takes longer than dying directly from a fatal wound.  ;D


Isn't dying of gangrene usually just a form of dying of a fatal wound?  I'd rather die quick than slow.  Unless slow = 80 years of aging lol.....

I don't think the situation is so dire as to compare it to dieing.  More like the choice of having your arm chopped off or your eye poked out.  And hopefully losing all the fish is like having your eye poked out when you are half blind anyway (but which eye?  I'm not saying). 

Which means off course that I think everything is ok, and nothing bad is happening and I'm a denier.

:P
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Michael Hauber

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Re: Conservative Scientists & its Consequences
« Reply #510 on: February 05, 2015, 07:12:20 AM »

Furthermore, I provide the following link to a pdf of a PowerPoint presentation that explains the IPCC AR5's official thinking about the carbon budget,

Since when does IPCC have an official thinking about the carbon budget?  I find no discussion of what the carbon budget should be in the IPCC report.

which uses the concept of TCRE (which is lower than using equilibrium climate sensitivity. 
IPCC project climate change using TCRE because that is what is relevant to projections over the next century.  They still discuss equilibrium climate sensitivity and make projections for several hundred years in the future.  Full equilibrium sensitivity will likely take centuries to millennia to achieve.

Furthermore, the IPCC's carbon budget concept ignores methane emissions from permafrost degradation under RCP8.5,
One of only two places I find 'carbon budget' briefly mentioned in the IPCC report is on page 323 with the comment that permafrost emissions from the Arctic 'could substantially alter the carbon budget through the release of methane'

and it ignore what are traditionally considered slow response feedback mechanisms (such as the collapse of the WAIS) that could actually happen this century following a BAU pathway:

http://www.climatechange2013.org/images/uploads/7_knutti13sed2_v1.pdf

Do you refer to the recent ice sheet collapse research which finds that the onset of rapid (i.e. >1 mm a year or 1 metre/ centurey) sea level rise due to ice sheet melt will start within 200 to 900 years?
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Re: Conservative Scientists & its Consequences
« Reply #511 on: February 05, 2015, 12:02:09 PM »
Which means off course that I think everything is ok, and nothing bad is happening and I'm a denier.

:P

With all due respect, Michael, but that's the impression I get when you say something like: "More Co2 in the oceans means less in the atmosphere so this study is good news for us, and bad news for the sea life in the southern ocean."

But maybe that says more about me than about you.  ;)
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Re: Conservative Scientists & its Consequences
« Reply #512 on: February 05, 2015, 06:42:39 PM »
Do you refer to the recent ice sheet collapse research which finds that the onset of rapid (i.e. >1 mm a year or 1 metre/ centurey) sea level rise due to ice sheet melt will start within 200 to 900 years?

Joughin et al 2014 is one recent publication pointing to the risk of abrupt sea level rise starting this century, since it has some conservative assumptions. Another one is Rignot et al 2014:
http://onlinelibrary.wiley.com/doi/10.1002/2014GL060140/full

Rignot thinks one third of WAIS could be gone in 100-200 years.

Pollard et al 2015 is another recent paper which suggests WAIS could be gone within 100 years, once the collapse really gets going, which could be by the middle of this century:
http://www.sciencedirect.com/science/article/pii/S0012821X14007961

Co-author Alley said this may not be the "true worst worst-case" yet.

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Re: Conservative Scientists & its Consequences
« Reply #513 on: February 05, 2015, 06:52:13 PM »
In any reasonably well constructed scientific investigation, the input radiative forcing scenarios should track the middle emissions track-record and not the high end. 

Very wrong.  If a scientist group makes multiple predictions/estimations etc, some should be near the middle, some should be near the high end and some in the low end, with a small amount outside the range.  If this is not the case then the error range is being overestimated.

Frequentists (such as adopted by the IPCC process) can (and do) construct investigations anyway that they want and then do a frequency count of the out-coming and then declare that their frequency count represents the true probability; which is the truth behind the common saying: "There are lies, damn lies and statistics".  In other words if the investigation is not well-constructed its frequency count will not represent the true probability (ie "Garbage in, Garbage out").

IPCC has constructed a family of forcing scenarios from RCP 2.6 to RCP 8.5; following a frequentist approach.  However, frequentist methodology only works when their investigations are well-constructed, otherwise I would recommend using the Bayesian approach of developing a priori PDF based on the past fifty years of experience following a BAU pathway, and then change this PDF incrementally based on new observation.

Evidence that the IPCC RCP frequentist methodology is biased is easily seen by the fact that they give equal weighting to the out-comes of all of the RCP 2.6 thru 8.5 scenarios; while in-fact RCP 2.6 has less than a 1% chance of being achieved while we have been following essentially RCP 8.5 every year for the past 50-years but we give it equal weight to any of the other constructed scenarios.

Even worse, when the IPCC establishes their carbon budget of "840 GtC" with a 50 percent chance of staying below 2 C (as guidance to decision makers) they assume that RCP 2.6 is the only scenario being followed, and that there is no need to multiply the 50 percent chance number by the probability that RCP 2.6 will be followed (which by their own methodology should be 20%, while I believe that it should be 1%).  Furthermore, the IPCC only updates their guidance every six to seven years so when they tell decision makers that in 2011 GHG emission rates were around 10 GtC per year, they fail to point-out that this number is increasing every year and by 2015 to 2016 should be more like 13.7 GtC per year (especially when considering all of the methane gas leaks that jai points out)

http://www.c2es.org/science-impacts/ipcc-summaries/fifth-assessment-report-working-group-1

"Cumulative Carbon Budgets
The AR5 relates different carbon “budgets” – an accumulated amount of carbon emissions over time — to the chances of average warming exceeding 2 degrees above 1861-1880 levels. Governments have set an international goal of limiting average warming to 2 C. For the world to have a 50 percent chance of staying below 2 C of warming by 2100, the AR5 identifies a greenhouse gas emissions budget of 840Gt of carbon. More than half of that (over 531GtC) has already been emitted. At current emission rates (around 10 GtC per year), we will use up our carbon budget in just 30 years."
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Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #514 on: February 05, 2015, 06:53:48 PM »
Also see this non-technical explanation by Rignot in the Guardian:
http://www.theguardian.com/commentisfree/2014/may/17/climate-change-antarctica-glaciers-melting-global-warming-nasa

Quote
At the current rate, a large fraction of the basin will be gone in 200 years, but recent modelling studies indicate that the retreat rate will increase in the future. How did this happen? A clue is that all the glaciers reacted at the same time, which suggested a common force that can only be the ocean. Ocean heat is pushed by the westerly winds and the westerlies have changed around Antarctica in response to climate warming and the depletion of the ozone. The stronger winds are caused by a world warming faster than a cooling Antarctica. Stronger westerlies push more subsurface warm waters poleward to melt the glaciers, and push surface waters northward.

Nerilie Abram and others have just confirmed that the westerlies are stronger now than at any other time in the past 1,000 years and their strengthening has been particularly prominent since the 1970s as a result of human-induced climate warming. Model predictions also show that the trend will continue in a warming climate.

What this means is that we may be ultimately responsible for triggering the fast retreat of West Antarctica. This part of the continent was likely to retreat anyway, but we probably pushed it there faster. It remains difficult to put a timescale on it, because the computer models are not good enough yet, but it could be within a couple of centuries, as I noted. There is also a bigger picture than West Antarctica. The Amundsen sea sector is not the only vulnerable part of the continent. East Antarctica includes marine-based sectors that hold more ice. One of them, Totten glacier, holds the equivalent of seven metres of global sea level.

Controlling climate warming may ultimately make a difference not only about how fast West Antarctic ice will melt to sea, but also whether other parts of Antarctica will take their turn. Several "candidates" are lined up, and we seem to have figured a way to push them out of equilibrium even before warming of air temperature is strong enough to melt snow and ice at the surface.

Unabated climate warming of several degrees over the next century is likely to speed up the collapse of West Antarctica, but it could also trigger irreversible retreat of marine-based sectors of East Antarctica. Whether we should do something about it is simply a matter of common sense. And the time to act is now; Antarctica is not waiting for us.

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Re: Conservative Scientists & its Consequences
« Reply #515 on: February 05, 2015, 06:58:11 PM »
And Rignot again in the Washington Post:
http://www.washingtonpost.com/national/health-science/research-casts-alarming-light-on-decline-of-west-antarctic-ice-sheets/2014/12/04/19efd3e4-7bbe-11e4-84d4-7c896b90abdc_story.html

Quote
how fast could the loss of West Antarctica unfold? Velicogna’s co-author, Eric Rignot of UC-Irvine, suggested that in his view, within 100 to 200 years, one-third of West Antarctica could be gone. Rignot noted that the scientific community “still balks at this” — particularly the 100-year projection — but said he thinks observational studies are showing that ice sheets can melt at a faster pace than model-based projections take into account.

Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #516 on: February 05, 2015, 07:01:21 PM »
Alley's comments to his paper with Pollard and DeConto:
http://arstechnica.com/science/2015/01/updated-ice-sheet-model-matches-wild-swings-in-past-sea-levels/

"Step-application of the [warming] is too extreme, clearly…  but, it is within the realm of possibility that for the time-scale of collapse, the true worst worst-case scenario could be even a bit faster than modeled here"

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Re: Conservative Scientists & its Consequences
« Reply #517 on: February 05, 2015, 07:10:17 PM »
There are many different versions/generations of Earth Systems Models.  Thus saying that an earlier version of the Community Earth System Model, was included in CMIP5 does not mean that we have the final answer in hand from AR5.  Indeed, the ACME project lead by the DOE (and which will not be complete for another 10 years) is based on (started from) the Community Earth System Model, but will be further developed for the DOE mission and computers.

I am hoping that ACME will provide sufficient guidance to allow decision makers to make reasonably well informed decisions.  Until then (& even after then) we will need to make the best decisions that we can with the information that we have; understanding that decision makers with a high tolerance for risk will push the envelope perhaps further than what is good for the global community/environment.

But the models will not have changed very much from where they were for CMIP 5. 

And if a model did make a small change in this timeframe that mattered for climate sensitivity, or for transient climate response over the next 100 years then, either the scientists writing up the research are incompetent or party to a conspiracy of silence, or there is no interesting change and the scientist writes up about a detail such as a change in the Jetstream position as the most interesting result of the recent modelling study.

You are wrong, as the linked information confirms that ACME will make major changes to CESM:

http://newscenter.lbl.gov/2014/08/25/acme/
http://climatemodeling.science.energy.gov/
http://climatemodeling.science.energy.gov/sites/default/files/publications/acme-project-strategy-plan_0.pdf
http://climatemodeling.science.energy.gov/sites/default/files/publications/acme-project-strategy-plan.pdf
http://science.energy.gov/~/media/sc-1/pdf/2012/Dehmer_2016_Budget_Presentation.pdf
http://crf.sandia.gov/acme-climate-modeling-powered-by-doe-supercomputers-tamed-by-uncertainty-quantification/
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #518 on: February 05, 2015, 07:43:43 PM »

Furthermore, I provide the following link to a pdf of a PowerPoint presentation that explains the IPCC AR5's official thinking about the carbon budget,

Since when does IPCC have an official thinking about the carbon budget?  I find no discussion of what the carbon budget should be in the IPCC report.

AR5 was the first time that the IPCC introduced a carbon budget, and in your comment below you admit that you found a reference to this carbon budget, so your comment here is nothing more than a red herring, wasting everyone's time. ASLR

which uses the concept of TCRE (which is lower than using equilibrium climate sensitivity. 
IPCC project climate change using TCRE because that is what is relevant to projections over the next century.  They still discuss equilibrium climate sensitivity and make projections for several hundred years in the future.  Full equilibrium sensitivity will likely take centuries to millennia to achieve.

If applying the TCRE to the RCP forcing scenarios were the final answer then there would be no need to run any Earth Systems Models, because you are ready have the answer.  However, this is not the case as: (a) in Replies 502 thru 504 I show that in scenarios highly out of equilibrium such as RCP 8.5, TCRE is non-linear and would increase markedly. by 2060; and (b) as Lennart has shown at least the ice sheet feedback mechanism for the WAIS could be accelerated to be effective in 21st Century. ASLR

Furthermore, the IPCC's carbon budget concept ignores methane emissions from permafrost degradation under RCP8.5,
One of only two places I find 'carbon budget' briefly mentioned in the IPCC report is on page 323 with the comment that permafrost emissions from the Arctic 'could substantially alter the carbon budget through the release of methane'

Thanks for confirming my comment. ASLR

and it ignore what are traditionally considered slow response feedback mechanisms (such as the collapse of the WAIS) that could actually happen this century following a BAU pathway:

http://www.climatechange2013.org/images/uploads/7_knutti13sed2_v1.pdf

Do you refer to the recent ice sheet collapse research which finds that the onset of rapid (i.e. >1 mm a year or 1 metre/ centurey) sea level rise due to ice sheet melt will start within 200 to 900 years?

Again, Lennart provides a lot of evidence that you are out-of-date with your information, and I will add the following reference:

DeConto R, and Pollard D., (2014), "Antarctica's potential contribution to future sea-level rise", SCAR - COMNAP Symposium

http://www.scar2014.com/assets/SCAR_and_COMNAP_2014_Abstract_Document.pdf

Abstract: "A hybrid ice sheet-shelf model with freely migrating grounding lines is improved by accounting for 1) surface meltwater enhancement of ice shelf calving; and 2) the structural stability of thick (>800 m), marine-terminating (tidewater) grounding lines. When coupled to a high-resolution atmospheric model with imposed or simulated ocean temperatures, the new model is demonstrated to do a good job simulating past geologic intervals with high (albeit uncertain) sea levels including the Pliocene (3Ma; +20 ±10m) and the Last Interglacial (130-115ka; +4-9m).  When applied to future IPCC CMIP5 RCP greenhouse gas forcing scenarios with ocean temperatures provided by the NCAR CCSM4, the same model shows the potential for massive ice and freshwater discharge beginning in the second half of this century. In both RCP2.6 and 8.5 scenarios considerable retreat begins in the Pine Island Bay region of West Antarctica. In the more aggressive (and arguably more likely) RCP8.5 scenario, Pine Island Bay retreat is followed by more massive retreat of the entire WAIS, and eventual ice retreat into deep East Antarctic basins. During peak rates of retreat, freshwater discharge exceeds 1 Sv and exceeds 0.2 Sv for several centuries with potential to disrupt ocean circulation in addition to contributing between 2m and 9m sea level rise within the next 500 years. Here, we demonstrate that large portions of the Antarctic Ice Sheet (in West and East Antarctica) can retreat on relatively short (decadal to centennial) timescales, posing a serious threat to global populations."

Note that as 1 Sv = 86mm of SLR per year, this research indicates that the WAIS might plausibly contribute over 0.86 meters per decade to SLR before the end of this century. In addition to other SLR sources, this could resulting in over 3m of SLR, and over 4m of Regional SLR for the Continental U.S.A. for a RCP 8.5 pathway.
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Re: Conservative Scientists & its Consequences
« Reply #519 on: February 05, 2015, 10:07:45 PM »
The linked article contains many good points (see the extract below), supporting the position that there may be no budget available for more carbon emissions if society wants to take a responsible approach towards climate change risks:

http://www.climatecodered.org/2014/06/carbon-budgets-climate-sensitivity-and.html

Extract: "… preliminary results by scientists at the California Institute of Technology Jet Propulsion Laboratory presented at the 2013 AGU meeting showed that higher sensitivity models do the best job simulating observed cloud changes. These results are also consistent with Lauer et al. (2010) and Clement et al. (2009), which looked at cloud changes in the Pacific, finding the observations consistent with a positive cloud feedback" (4).

If indeed ECS is more likely at the higher end of the range, this would diminish the remaining carbon budget.  Quantifying a carbon budget for a ~4°C mid-point ECS has not been done as far as I can ascertain.

Long-term earth system sensitivity

Paleoclimatology (study of past climates) suggests that if longer-term feedbacks of "slow" factors are taken into account, such as the decay of large ice sheets, changes in the carbon cycle (changed efficiency of carbon sinks such as permafrost and methane clathrate stores, as well as biosphere stores such as peatlands and forests), and changes in vegetation coverage and reflectivity (albedo), then the Earth's sensitivity to a doubling of CO2 could itself be double that of the "fast" climate sensitivity predicted by most climate models, or around 6°C (5). These "slow" feedbacks amplify the initial warming burst. A measure of these effects for a doubling of CO2 is known as Earth System Sensitivity (ESS).

Longer-term ESS is generally considered to come into play over periods from centuries to several millennia, depending on how fast is the rate of change in greenhouse gas levels and temperature.

The problem is that rate of climate change now being driven by human actions may be as fast as any extended warming period over the past 65 million years, and it is projected to accelerate in the coming decades. This means that longer-term "slow" events associated with ESS – such as loss of large ice sheets, and changes in Arctic and biosphere carbon stores – are starting to occur now, are happening much more quickly than expected, and likely will proceed at a significant scale in the current hundred years. We face an event unprecedented in the last 65 million years of "fast" short-term and "slow" long-term climate sensitivity events occurring alongside one another in parallel, rather than one after the other in series as is usually the case. Thus, even as some of the "fast" warming is still to be realised due to thermal inertia, some of the "slow" feedbacks are already coming into play:

Evidence from Earth’s history suggests that slower surface albedo feedbacks due to vegetation change and melting of Greenland and Antarctica can come into play on the timescales of interest to humans, which could increase the sensitivity to significantly higher values, as much as 6°C … the slow feedback climate sensitivity has relevance in the Anthropocene era, since ice sheet/vegetation feedback may become significant on decadal-to-centennial timescales of interest to humans (6).
and
Unfortunately, slow feedbacks are amplifying on time scales that humans care about: decades, centuries, even millennia. As the planet warms, for example, ice sheets melt, exposing a darker surface that increases warming. Also warming causes a net release of long-lived greenhouse gases from the ocean and soil. Vegetation changes that occur as climate warms from today's situation will also have a significant amplifying effect, as forests move into tundra regions in North America and Eurasia (7).

The problem is that the IPCC carbon budget analysis assumes that none of these longer-term feedbacks will be materially relevant before 2°C of warming, and so exclude the possibility of large-scale permafrost, methane clathrate or less efficient biological stores (Amazon, tundra etc) making contributions to atmospheric greenhouse gas levels and impacting on the carbon budget.

Thus the IPCC 2013 report notes that "Accounting for ... the release of greenhouse gases from permafrost will also lower..." the target, and that the CMIP5 modelling used for the IPCC's carbon budgets does not include "explicit representation of permafrost soil carbon decomposition in response to future warming". It also notes that "the climate sensitivity of a model may... not reflect the sensitivity of the full Earth system because those feedback processes ["slow feedbacks associated associated with vegetation changes and ice sheets"] are not considered".

Several lines of evidence suggest theses assumptions are not robust. Recent research shows that the Amazon may often be releasing huge quantities of CO2 to the atmosphere, acting not as a carbon sink but as a source (8); and that the seafloor off the coast of Northern Siberia is releasing more than twice the amount of methane as previously estimated and is now on par with the methane being released from the Arctic tundra (9).

In February 2013, scientists using radiometric dating techniques on Russian cave formations to measure historic melting rates warned that a +1.5ºC global rise in temperature compared to pre-industrial was enough to start a general permafrost melt. They found that “global climates only slightly warmer than today are sufficient to thaw extensive regions of permafrost.” Lead researcher Anton Vaks says that: “1.5ºC appears to be something of a tipping point” (10).

In 2011, Schaefer, Zhang et al. warned: "The thaw and release of carbon currently frozen in permafrost will increase atmospheric CO2 concentrations and amplify surface warming to initiate a positive permafrost carbon feedback (PCF) on climate…. [Our] estimate may be low because it does not account for amplified surface warming due to the PCF itself….We predict that the PCF will change the Arctic from a carbon sink to a source after the mid-2020s and is strong enough to cancel 42-88% of the total global land sink. The thaw and decay of permafrost carbon is irreversible and accounting for the PCF will require larger reductions in fossil fuel emissions to reach a target atmospheric CO2 concentration" (11).

This very strong and disturbing finding – that permafrost decay is "irreversible" and requires a lower carbon budget – is not reflected in the IPCC's figuring.

Conclusion

Climate change with its non-linear events, tipping points and irreversible events –  such as mass extinctions, destruction of ecosystems, the loss of large ice sheets and the triggering of large-scale releases of greenhouse gases from carbon stores such as permafrost and methane clathrates – contains many possibilities for catastrophic failure. 

If climate sensitivity is, in reality, at the high end of the range used for the IPCC's carbon budgets, then as a consequence that means that we must adopt a very low-risk of exceeding the target.   As the previous post explained, If a risk-averse (pro-safety) approach is applied – say, of less than 10% probability of exceeding the 2°C target – to carbon budgeting, there is simply no budget available, because it has already been used up. The notion that there is still "burnable carbon" is a myth."
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Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #520 on: February 05, 2015, 10:36:15 PM »

You think they're cherry picking, but you only give one example of potential over-estimation from 1990. Is that enough for you to dismiss Brysse et al? Their paper seems much more convincing than your (potential) counter-example.

- methane emissions
- Australian rainfall reductions (as a whole Australian rainfall has increased - however reductions have been in the more heavily populated and farmed southern areas)
- US temperature increases (regional effect - but then so really is Arctic sea ice reduction)

Can you give sources? Brysse et al say over-estimation is less common than under-estimation:
https://www.wageningenur.nl/upload_mm/2/0/b/f2601035-3fa4-41cb-b0f5-77de713695fc_erring.pdf

And Anderegg et al conclude:
http://journals.ametsoc.org/doi/full/10.1175/BAMS-D-13-00115.1

"Both in paradigm and procedure, the scientific method and culture prioritize type 1 error aversion (Hansson 2013) and “erring on the side of least drama” (O'Reilly et al. 2011) or “scientific reticence” (Hansen 2007), and this can be amplified by both publication bias and scientific assessment (Freudenburg and Muselli 2010; Lemons et al. 1997; O'Reilly et al. 2011). Thus, the high consequence and tails of the distribution of climate impacts, where experts may disagree on likelihood or where understanding is still limited, can often be left out or understated in the assessment process (Oppenheimer et al. 2007; Socolow 2011)... the balance of evidence indicates that potential type 2 errors may be more prevalent in assessments, such as the IPCC."

Do you know of any peer-reviewed papers that refute or contest these conclusions?

Anderegg et al then say:
"This asymmetry of treatment of error has unintended consequences. Type 2 errors can hinder communication of the full range of possible climate risks to the media, the public, and decision makers who have to justify the basis of their analyses. Thus, such errors have the potential to lead to unnecessary loss of lives, livelihoods, or economic damages. Yet, as Stephen Schneider eloquently highlighted throughout his work, high-consequence, controversial, uncertain impacts are exactly what policy makers and other stakeholders would like to know to perform risk management (National Research Council 2011; Schneider et al. 1998; Socolow 2011).

Naturally, varying situations and contexts apply different decision rules in considering type 1 versus type 2 errors, and type 1 error aversion is beneficial in certain circumstances. Moreover, uncertainty must be recognized as multifaceted and textured. As such, Brian Wynne described four kinds of uncertainty: 1) “risk”—where we know the odds, system behavior, and outcomes can be defined as well as quantified through probabilities; 2) “uncertainty”—where system parameters are known, but not the odds or probability distributions; 3) “ignorance”—risks that escape recognition; and 4) “indeterminacy”—which captures elements of the conditionality of knowledge and contextual scientific, social, and political factors (Wynne 1992). Thus, the risks through uncertainty in these conditions of postnormal science have material implications. Incomplete presentation of the full possibilities of outcomes (likelihood compounded by consequence) can lead to a lack of preparedness, loss of livelihoods or lives, and economic damage."

Do you think all this is nonsense or irrelevant, or could it make at least some sense?

If there's a chance that IPCC under-estimates risks we better be aware of that. If it turns out their best estimates were about right after all, so much the better. Would you agree with this conclusion, or not, and if not, why?

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Re: Conservative Scientists & its Consequences
« Reply #521 on: February 05, 2015, 11:59:06 PM »

Joughin et al 2014 is one recent publication pointing to the risk of abrupt sea level rise starting this century, since it has some conservative assumptions. Another one is Rignot et al 2014:
http://onlinelibrary.wiley.com/doi/10.1002/2014GL060140/full

Rignot thinks one third of WAIS could be gone in 100-200 years.

Nothing in the linked paper seems to support that, although he has been quoted in media releases as saying that.

Pollard et al 2015 is another recent paper which suggests WAIS could be gone within 100 years, once the collapse really gets going, which could be by the middle of this century:
http://www.sciencedirect.com/science/article/pii/S0012821X14007961

Co-author Alley said this may not be the "true worst worst-case" yet.

This is the most aggressive paper, and both ends of the range need to be considered (I posted the less aggressive paper because that was the one I found).  Note that this paper is talking about volume which relates to sea level rise which is a separate issue to what I am debating.  The issue under debate is Antarctic albedo and the idea that there will be a major acceleration in warming due to Antarctic albedo loss.  Antarctica happens to be very close in size to the Arctic sea ice at maximum.  Just eyeballing his future charts it looks like the loss of Antarctic ice sheet area in the next 100 years may be something like 20%, which is 500k sq km per decade.   This looks slower than the Arctic area loss witnessed in the last 10 or so years, which hardly set the world on fire as we've seen the hiatus (however minor and statistically insignificant it may be) in recent warming at the same time.  Basic physics does say it will have to provide some warming, but until someone puts some hard numbers on it, I'm not convinced it will be enough to make much difference.
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Michael Hauber

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Re: Conservative Scientists & its Consequences
« Reply #522 on: February 06, 2015, 12:10:01 AM »

Frequentists (such as adopted by the IPCC process) can (and do) construct investigations anyway that they want and then do a frequency count of the out-coming and then declare that their frequency count represents the true probability; which is the truth behind the common saying: "There are lies, damn lies and statistics".  In other words if the investigation is not well-constructed its frequency count will not represent the true probability (ie "Garbage in, Garbage out").
Frequentists measure the probability of something by measuring the frequency that something occurs in a sample set and assuming this is the probability.  This contrasts to Bayesians who also consider 'prior' probabilities based on other logic and then blend this with the measured frequency to create and adjusted probability function.

IPCC has constructed a family of forcing scenarios from RCP 2.6 to RCP 8.5; following a frequentist approach.  However, frequentist methodology only works when their investigations are well-constructed, otherwise I would recommend using the Bayesian approach of developing a priori PDF based on the past fifty years of experience following a BAU pathway, and then change this PDF incrementally based on new observation.

Evidence that the IPCC RCP frequentist methodology is biased is easily seen by the fact that they give equal weighting to the out-comes of all of the RCP 2.6 thru 8.5 scenarios; while in-fact RCP 2.6 has less than a 1% chance of being achieved while we have been following essentially RCP 8.5 every year for the past 50-years but we give it equal weight to any of the other constructed scenarios.

The IPCC do not make any probabilistic statements on RCP2.6 vs 8.5.  They do not use frequentist (or any other statistical) methods, but rather define the scenarios around meeting several pre-defined target for final radiative forcing value. 


http://www.c2es.org/science-impacts/ipcc-summaries/fifth-assessment-report-working-group-1

"Cumulative Carbon Budgets
The AR5 relates different carbon “budgets” – an accumulated amount of carbon emissions over time — to the chances of average warming exceeding 2 degrees above 1861-1880 levels. Governments have set an international goal of limiting average warming to 2 C. For the world to have a 50 percent chance of staying below 2 C of warming by 2100, the AR5 identifies a greenhouse gas emissions budget of 840Gt of carbon. More than half of that (over 531GtC) has already been emitted. At current emission rates (around 10 GtC per year), we will use up our carbon budget in just 30 years."

The centre for climate and energy solutions talk about an IPCC carbon budget, but I can find no such thing when searching the IPCC reports.
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Re: Conservative Scientists & its Consequences
« Reply #523 on: February 06, 2015, 12:25:50 AM »
An additional point on 'frequentist' issues.  James Annan criticises the IPCC for using a Bayesian (i.e. opposite of frequentist) technique for estimating climate sensitivity, and using it incorrectly.  James shows that the IPCC's improper use of a uniform prior provides a more alarming estimate of climate sensitivity then the prior that he considers most appropriate.  Note this predates the latest assessment report so may not be relevant to the fifth assessment report.
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Re: Conservative Scientists & its Consequences
« Reply #524 on: February 06, 2015, 12:30:21 AM »
Quote
Furthermore, the IPCC's carbon budget concept ignores methane emissions from permafrost degradation under RCP8.5,
One of only two places I find 'carbon budget' briefly mentioned in the IPCC report is on page 323 with the comment that permafrost emissions from the Arctic 'could substantially alter the carbon budget through the release of methane'
Thanks for confirming my comment. ASLR


You have that totally backward.  The IPCC do not have a carbon budget, and have pointed out that permafrost emissions will have a significant impact on the carbon budget.
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Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #525 on: February 06, 2015, 01:13:42 AM »
The issue under debate is Antarctic albedo and the idea that there will be a major acceleration in warming due to Antarctic albedo loss.  Antarctica happens to be very close in size to the Arctic sea ice at maximum.  Just eyeballing his future charts it looks like the loss of Antarctic ice sheet area in the next 100 years may be something like 20%, which is 500k sq km per decade. This looks slower than the Arctic area loss witnessed in the last 10 or so years, which hardly set the world on fire as we've seen the hiatus (however minor and statistically insignificant it may be) in recent warming at the same time.  Basic physics does say it will have to provide some warming, but until someone puts some hard numbers on it, I'm not convinced it will be enough to make much difference.

Caldeira & Cvijanovic 2014 conclude loss of Arctic sea ice will make much difference:
http://journals.ametsoc.org/doi/full/10.1175/JCLI-D-14-00042.1

"Results obtained here indicate that in this configuration of CESM (CAM4 coupled to a slab ocean and the dynamic–thermodynamic sea ice model CICE4), approximately 3 × 1012 m2 of sea ice is lost for each kelvin of global mean warming and approximately 0.1 W m−2 of “sea ice radiative forcing” is produced by each 1012 m2 of sea ice loss, yielding a value of −0.3 W m−2 K−1 for the sea ice contribution to the overall climate feedback parameter. Because sea ice area in the 1×CO2 control simulation is approximately 30 × 1012 m2, this suggests that complete loss of all sea ice from the 1×CO2 state would produce a radiative forcing of about 3 W m−2, which is somewhat less than, but of the same order of magnitude as, the regressed radiative forcing from a doubling of atmospheric CO2."

And you may not be convinced, but did you read the posts above on the risk of making type 2 errors?

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Re: Conservative Scientists & its Consequences
« Reply #526 on: February 06, 2015, 01:51:47 AM »
The issue under debate is Antarctic albedo and the idea that there will be a major acceleration in warming due to Antarctic albedo loss.  Antarctica happens to be very close in size to the Arctic sea ice at maximum.  Just eyeballing his future charts it looks like the loss of Antarctic ice sheet area in the next 100 years may be something like 20%, which is 500k sq km per decade. This looks slower than the Arctic area loss witnessed in the last 10 or so years, which hardly set the world on fire as we've seen the hiatus (however minor and statistically insignificant it may be) in recent warming at the same time.  Basic physics does say it will have to provide some warming, but until someone puts some hard numbers on it, I'm not convinced it will be enough to make much difference.

Caldeira & Cvijanovic 2014 conclude loss of Arctic sea ice will make much difference:
http://journals.ametsoc.org/doi/full/10.1175/JCLI-D-14-00042.1

"Results obtained here indicate that in this configuration of CESM (CAM4 coupled to a slab ocean and the dynamic–thermodynamic sea ice model CICE4), approximately 3 × 1012 m2 of sea ice is lost for each kelvin of global mean warming and approximately 0.1 W m−2 of “sea ice radiative forcing” is produced by each 1012 m2 of sea ice loss, yielding a value of −0.3 W m−2 K−1 for the sea ice contribution to the overall climate feedback parameter. Because sea ice area in the 1×CO2 control simulation is approximately 30 × 1012 m2, this suggests that complete loss of all sea ice from the 1×CO2 state would produce a radiative forcing of about 3 W m−2, which is somewhat less than, but of the same order of magnitude as, the regressed radiative forcing from a doubling of atmospheric CO2."

And you may not be convinced, but did you read the posts above on the risk of making type 2 errors?

So if my eyeball estimate is right that loss of Antarctica area will be roughly 20%, this corresponds to a 0.6 w m-2 feedback (with further water vapour and cloud feedbacks compounded on top), which compares to an RCP 8.5 scenario forcing of about 8.5 w m-2. with total feedbacks of something like 15 w m-2 (including water vapour and cloud feedbacks) to get to a midrange climate sensitivity estimate.
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Re: Conservative Scientists & its Consequences
« Reply #527 on: February 06, 2015, 02:11:34 AM »
Which means off course that I think everything is ok, and nothing bad is happening and I'm a denier.

:P

With all due respect, Michael, but that's the impression I get when you say something like: "More Co2 in the oceans means less in the atmosphere so this study is good news for us, and bad news for the sea life in the southern ocean."

But maybe that says more about me than about you.  ;)

Neven,

You may want to consider that "where there is smoke there is fire", and where there is troll-like behavior, there may well be a troll.

Best,
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Michael Hauber

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Re: Conservative Scientists & its Consequences
« Reply #528 on: February 06, 2015, 02:22:12 AM »

You think they're cherry picking, but you only give one example of potential over-estimation from 1990. Is that enough for you to dismiss Brysse et al? Their paper seems much more convincing than your (potential) counter-example.

- methane emissions
- Australian rainfall reductions (as a whole Australian rainfall has increased - however reductions have been in the more heavily populated and farmed southern areas)
- US temperature increases (regional effect - but then so really is Arctic sea ice reduction)

Can you give sources?

Methane:  I cannot find the specific emissions allowed for in early IPCC scenarios, however looking at the history which shows  a rapid decline in growth of methane concentrations after 1990 (and an increase again in the last few years - which the linked chart omits most of, but I can't find a complete chart that shows further back than 1980 and more recently than that).  Given the size of this decline, and a lack of any hint in discussions of methane in the IPCC reports of a possible mechanism that could have predicted such a decline it seems a safe bet that methane scenarios in early IPCC reports were a significant overestimate.

US temperature - It used to be a favourite denier trick to create an analysis of temperature trends in the US for stations selected as 'good quality' and without adjustment, point to the lack of warming trend and claim that the measured warming was due to the adjustments and/or poor quality of the stations.  This ignored the fact that sources such as GISS also showed little warming.  However looking at the GISS US chart much of this lack of trend is due to the very warm years around 1930, so it isn't really fair to claim that this reflects an overestimate of US warming rates in the IPCC reports which were produced from 1990 on, during which period the US has warmed at a significant rate.  An investigation of regional trends using GISS mapping tool for the period from 1990 does show that much of Russia has shown very little warming over recent years, which is a roughly equivalent regional effect.

Australian rainfall:  Official Australian Bureau of Meteorology statistics show a clear increase in total rainfall for Australia.  However note the increase is in the almost unpopulated northwest of the country (Darwin pop 100k, a couple 10k towns are the major population centers for 1000s of kilometres of coastline).   This hides declines in the southern part of the country which is where the greater part of our population and agriculture is found, and drought is definitely a serious concern for Australia.
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Re: Conservative Scientists & its Consequences
« Reply #529 on: February 06, 2015, 03:58:41 AM »
Do you refer to the recent ice sheet collapse research which finds that the onset of rapid (i.e. >1 mm a year or 1 metre/ centurey) sea level rise due to ice sheet melt will start within 200 to 900 years?

Joughin et al 2014 is one recent publication pointing to the risk of abrupt sea level rise starting this century, since it has some conservative assumptions. Another one is Rignot et al 2014:
http://onlinelibrary.wiley.com/doi/10.1002/2014GL060140/full

Rignot thinks one third of WAIS could be gone in 100-200 years.

Pollard et al 2015 is another recent paper which suggests WAIS could be gone within 100 years, once the collapse really gets going, which could be by the middle of this century:
http://www.sciencedirect.com/science/article/pii/S0012821X14007961

Co-author Alley said this may not be the "true worst worst-case" yet.

Don't worry, he has already seen these studies in depth presented here and in other threads. Yet, he will be sure to provide the same conclusions.  This is where his 'blind spot' exists.  Even though he is shown the concrete studies that indicate, nay, assert that the current projections are severely undserstated.  He will continue to wanely pass them over and post his cherry picked research.  Just like any intentional climate denier would.

Mike is a warmist.  just get over him.
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Re: Conservative Scientists & its Consequences
« Reply #530 on: February 06, 2015, 08:51:58 AM »
"where there is troll-like behavior, there may well be a troll."
+1

"Mike is a warmist.  just get over him."

+2
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Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #531 on: February 06, 2015, 09:16:04 AM »
"where there is troll-like behavior, there may well be a troll."
+1

"Mike is a warmist.  just get over him."

+2

I may be wrong, but he seems to accept IPCC's conclusions. What he does not seem to recognize is the risk and likelihood that IPCC under-estimates important climate risks. So he joins many scientists in a preference to rather err on the side of least drama than to worry about fat tails. I would not call this 'troll-like' or 'warmist', but 'conservative' or 'risky' or 'confused' or 'stubborn'.

But I may be wrong.

Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #532 on: February 06, 2015, 09:17:46 AM »
I forgot 'frustrating'. It certainly is frustrating :)

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Re: Conservative Scientists & its Consequences
« Reply #533 on: February 06, 2015, 10:06:10 AM »
I believe that the IPCC is accurate in their conclusions.

I believe they are imperfect and will be a mix of overestimates and underestimates.

I believe that considering only the middle case underestimates potential risks - the small chance of very large impacts at the high end of IPCC estimates outweigh the small chance of milder impacts at the low end.  Very roughly - 10% chance of low impacts cost = 1, 80% chance of moderate impacts cost = 10, 10% chance of high impacts, cost = 100.  Expected cost = 10%*100+80%*10+10%*1 = 18.1, which is much higher than the expected cost of the middle impact.

I believe that any claim that the high range estimates have more scientific support for being likely than the mid range impacts is ignorant.
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jai mitchell

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Re: Conservative Scientists & its Consequences
« Reply #534 on: February 06, 2015, 01:39:01 PM »
I believe that any claim that the high range estimates have more scientific support for being likely than the mid range impacts is ignorant.

Ignorance is when you *ignore* the significant body of new science that has been done since the recent IPCC cutoff date that indicates a significantly higher risk than has been previously asserted.  Ignorance is when you assert that all of the emissions reductions likely for the energy generation sector will also magically spread to the industrial and transport sector and when you confuse the RCP 4.5 with the RCP 2.6 scenarios, thinking that 2.6 is even remotely possible, when RCP 6.0 is now our most likely optimistic scenario.  Ignorance is when you repeat the falsehood that the IPCC included frozen soils in its projections (it didn't) and that the Carbon cycle feedbacks were included (they were but only for RCP 8.5, not the more likely scenarios).

Ignorance is asserting that the Antarctica sea ice growth somehow balances out the arctic sea ice growth. 

I guess it is fine to have someone to argue with, however, constantly asserting your *truth* with complete disregard to the evidence that is presented to you, often times by many different people using multiple sources, makes you appear either dull or operating on an agenda of misinformation. 
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Re: Conservative Scientists & its Consequences
« Reply #535 on: February 06, 2015, 07:55:50 PM »
I believe that the IPCC is accurate in their conclusions.

I believe they are imperfect and will be a mix of overestimates and underestimates.

I believe that considering only the middle case underestimates potential risks - the small chance of very large impacts at the high end of IPCC estimates outweigh the small chance of milder impacts at the low end.  Very roughly - 10% chance of low impacts cost = 1, 80% chance of moderate impacts cost = 10, 10% chance of high impacts, cost = 100.  Expected cost = 10%*100+80%*10+10%*1 = 18.1, which is much higher than the expected cost of the middle impact.

I believe that any claim that the high range estimates have more scientific support for being likely than the mid range impacts is ignorant.

So with these four beliefs, what is in your view an appropriate mitigation target and carbon budget?

Hansen et al 2013 (PlosOne) argue we've only 130 GtC left to burn and think that could keep warming below 1.2 degrees C, while Bill McKibben thinks this would give an 80% chance of keeping warming below 2 degrees C (under some different assumptions):
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081648

To what extent do you or don't you agree with Hansen et al, and why?

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #536 on: February 06, 2015, 08:20:27 PM »
While some deny that the AR5 officially discusses a carbon budget to stay below 2 C, the following link leads to an official IPCC cite discussing the carbon budget:

http://www.ipcc.ch/pdf/presentations/WMO_EC/2%20plattner14wmo_exec_council_prelim.pdf

See also:
http://www.ipcc.ch/news_and_events/outreach.shtml

More specifically, Reto Knutti is one of the lead authors for the AR5 WG1 report and the ClimateChange2013 website is an official IPCC website, there can be no doubt that the linked R. Knutti PowerPoint represents official IPCC guidance regarding a carbon budget:

http://www.climatechange2013.org/images/uploads/7_knutti13sed2_v1.pdf

See also:
http://www.climatechange2013.org/

Authors of WGI report:
 Lisa V. Alexander (Australia), Simon K. Allen (Switzerland/New Zealand), Nathaniel L. Bindoff (Australia), François-Marie Bréon (France), John A. Church (Australia), Ulrich Cubasch (Germany), Seita Emori (Japan), Piers Forster (UK), Pierre Friedlingstein (UK/Belgium), Nathan Gillett (Canada), Jonathan M. Gregory (UK), Dennis L. Hartmann (USA), Eystein Jansen (Norway), Ben Kirtman (USA), Reto Knutti (Switzerland), Krishna Kumar Kanikicharla (India), Peter Lemke (Germany), Jochem Marotzke (Germany), Valérie Masson-Delmotte (France), Gerald A. Meehl (USA), Igor I. Mokhov (Russian Federation), Shilong Piao (China), Gian-Kasper Plattner (Switzerland), Qin Dahe (China), Venkatachalam Ramaswamy (USA), David Randall (USA), Monika Rhein (Germany), Maisa Rojas (Chile), Christopher Sabine (USA), Drew Shindell (USA), Thomas F. Stocker (Switzerland), Lynne D. Talley (USA), David G. Vaughan (UK), Shang- Ping Xie (USA)
« Last Edit: February 06, 2015, 09:03:34 PM by AbruptSLR »
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #537 on: February 06, 2015, 09:06:07 PM »
The linked reference (with a free access pdf) and associated tables elaborate on the carbon budget issue (with the authors presenting assumptions in line with IPCC thinking, while I am concerned that other developing nations beside China will likely soon accelerate their carbon emissions):

Friedlingstein, P., R. M. Andrew, J. Rogelj, G. P. Peters, J. G. Canadell, R. Knutti, G. Luderer, M. R. Raupach, M. Schaeffer, D. P. van Vuuren and C. Le Quéré, 2014, Persistent growth of CO2 emissions and implications for reaching climate targets, doi: 10.1038/NGEO2248

http://www.iac.ethz.ch/people/knuttir/papers/friedlingstein14natgeo.pdf

Abstract: "Efforts to limit climate change below a given temperature level require that global emissions of CO2 cumulated over time remain below a limited quota. This quota varies depending on the temperature level, the desired probability of staying below this level and the contributions of other gases. In spite of this restriction, global emissions of CO2 from fossil fuel combustion and cement production have continued to grow by 2.5% per year on average over the past decade. Two thirds of the CO2 emission quota consistent with a 2 °C temperature limit has already been used, and the total quota will likely be exhausted in a further 30 years at the 2014 emissions rates. We show that CO2 emissions track the high end of the latest generation of emissions scenarios, due to lower than anticipated carbon intensity improvements of emerging economies and higher global gross domestic product growth. In the absence of more stringent mitigation, these trends are set to continue and further reduce the remaining quota until the onset of a potential new climate agreement in 2020. Breaking current emission trends in the short term is key to retaining credible climate targets within a rapidly diminishing emission quota."
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Steven

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Re: Conservative Scientists & its Consequences
« Reply #538 on: February 06, 2015, 09:56:17 PM »
New paper on climate sensitivity for Pliocene-Pleistocene.  See the following blog post:

http://www.carbonbrief.org/blog/2015/02/what-a-three-million-year-fossil-record-tells-us-about-climate-sensitivity


Quote
the researchers... found that the climate responded to changing carbon dioxide in the same way during both the warm Pliocene and the cold Pleistocene.  Foster says:

"At least for climates up to three degrees warmer than the pre-industrial, and four degrees cooler than pre-industrial, no extra feedbacks operated."

The results are likely to translate to a climate sensitivity [ECS] of between two and three degrees, says Prof David Lea from the University of California, in an accompanying News and Views article.  This is consistent with the range of climate sensitivity the IPCC gives, Foster adds:

"This suggests that the IPCC range is adequate to explain the response of the system in the Pliocene to climate forcing, and so, by extension, is likely adequate to explain the climate response in the near future as we approach Pliocene-like conditions."

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #539 on: February 06, 2015, 11:09:39 PM »
New paper on climate sensitivity for Pliocene-Pleistocene.  See the following blog post:

http://www.carbonbrief.org/blog/2015/02/what-a-three-million-year-fossil-record-tells-us-about-climate-sensitivity


Quote
the researchers... found that the climate responded to changing carbon dioxide in the same way during both the warm Pliocene and the cold Pleistocene.  Foster says:

"At least for climates up to three degrees warmer than the pre-industrial, and four degrees cooler than pre-industrial, no extra feedbacks operated."

The results are likely to translate to a climate sensitivity [ECS] of between two and three degrees, says Prof David Lea from the University of California, in an accompanying News and Views article.  This is consistent with the range of climate sensitivity the IPCC gives, Foster adds:

"This suggests that the IPCC range is adequate to explain the response of the system in the Pliocene to climate forcing, and so, by extension, is likely adequate to explain the climate response in the near future as we approach Pliocene-like conditions."

I concur that this paper represents good science; however, we should all remember that paleo investigations only address relatively slowly changing near-equilibrium conditions.  Furthermore, we should all remember that James Hansen has said the same thing that ECS is near 3 C and is the same for both warm and cold near equilibrium conditions; but it is important to note that Hansen is honest enough to advocate that rapidly changing global temperatures (due to strong anthropogenic forcing) can increase the effective climate sensitivity well above an ECS of nearly 3 C for reasoning including rapid changes in albedo, and/or one-shot degradation of the permafrost (and/or methane hydrates in the ESS).


Indeed, in no uncertain terms the following reference states that TCRE would increase markedly if global emissions (both anthropogenic & natural feedbacks) reach 25 GtC per year (which would occur by 2060 following an RCP 8.5 pathway):

Krasting, J. P., J. P. Dunne, E. Shevliakova, and R. J. Stouffer (2014), Trajectory sensitivity of the transient climate response to cumulative carbon emissions, Geophys. Res. Lett., 41, 2520–2527, doi:10.1002/2013GL059141.

http://onlinelibrary.wiley.com/doi/10.1002/2013GL059141/abstract

Abstract: "The robustness of Transient Climate Response to cumulative Emissions (TCRE) is tested using an Earth System Model (Geophysical Fluid Dynamics Laboratory-ESM2G) forced with seven different constant rates of carbon emissions (2 GtC/yr to 25 GtC/yr), including low emission rates that have been largely unexplored in previous studies. We find the range of TCRE resulting from varying emission pathways to be 0.76 to 1.04°C/TtC. This range, however, is small compared to the uncertainty resulting from varying model physics across the Fifth Coupled Model Intercomparison Project ensemble. TCRE has a complex relationship with emission rates; TCRE is largest for both low (2 GtC/yr) and high (25 GtC/yr) emissions and smallest for present-day emissions (5–10 GtC/yr). Unforced climate variability hinders precise estimates of TCRE for periods shorter than 50 years for emission rates near or smaller than present day values. Even if carbon emissions would stop, the prior emissions pathways will affect the future climate responses."

Furthermore, the following quote from the linked article by Joe Romm entitled: "Of Course Paris Climate Talks Won’t Keep Warming Below The Dangerous 2°C Limit", the representatives for the Paris Climate Talks are already backing away from RCP 2.6:

http://thinkprogress.org/climate/2015/02/05/3619717/paris-climate-talks-2c/

Quote from EU climate chief Miguel Arias Canete: “2C is an objective. If we have an ongoing process you cannot say it is a failure if the mitigation commitments do not reach 2C.”

Also, per the attached plot (from the Joe Romm article) society will be very lucky to follow an RCP 6.0 pathway.

Nero fiddled while Rome burned, and the last time I checked anthropogenic GHG emissions (yesterday) we are still following a BAU pathway (not RCP 6 nor RCP 4.5).  Therefore, until I actually see our radiative forcing footprint drop down to RCP 4.5, or preferable below, I am not going to accept that near-equilibrium paleo-evidence provides any proof that we are safe as we approach Pliocene conditions.
« Last Edit: February 06, 2015, 11:18:04 PM by AbruptSLR »
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Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #540 on: February 06, 2015, 11:18:48 PM »
Also let's not forget MacDougall et al 2012 on potential permafrost feedback:
http://www.nature.com/ngeo/journal/v5/n10/full/ngeo1573.html

"According to our simulations, permafrost soils will release between 68 and 508 Pg carbon by 2100. We show that the additional surface warming generated by the feedback between permafrost carbon and climate is independent of the pathway of anthropogenic emissions followed in the twenty-first century. We estimate that this feedback could result in an additional warming of 0.13–1.69 °C by 2300. We further show that the upper bound for the strength of the feedback is reached under the less intensive emissions pathways. We suggest that permafrost carbon release could lead to significant warming, even under less intensive emissions trajectories."

So, indeed, there may be no budget left, even for a quite risky 66% chance of staying below 2 degrees C.

This paper, however, was not taken very seriously by IPCC (yet), probably because it was so recent. But what if MacDougall et al are right?

Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #541 on: February 06, 2015, 11:22:19 PM »
Don't panick. We're safe on Spaceship Titanic.

jai mitchell

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Re: Conservative Scientists & its Consequences
« Reply #542 on: February 07, 2015, 12:57:58 AM »
Interestingly, the abstract from Steven's referenced article says the following.

http://www.nature.com/nature/journal/v518/n7537/full/nature14145.html

it seems that they attribute a significant ECS value to the gradual loss of surface ice in transition from partial and inter stadial to equitable climate regimes.

Quote
We find that Earth’s climate sensitivity to CO2-based radiative forcing (Earth system sensitivity) was half as strong during the warm Pliocene as during the cold late Pleistocene epoch (0.8 to 0.01 million years ago).

and

predictions of equilibrium climate sensitivity (excluding long-term ice-albedo feedbacks) for our Pliocene-like future (with CO2 levels up to maximum Pliocene levels of 450 parts per million) are well described by the currently accepted range of an increase of 1.5 K to 4.5 K per doubling of CO2.
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #543 on: February 07, 2015, 02:11:20 AM »
Interestingly, the abstract from Steven's referenced article says the following.

http://www.nature.com/nature/journal/v518/n7537/full/nature14145.html

it seems that they attribute a significant ECS value to the gradual loss of surface ice in transition from partial and inter stadial to equitable climate regimes.

Quote
We find that Earth’s climate sensitivity to CO2-based radiative forcing (Earth system sensitivity) was half as strong during the warm Pliocene as during the cold late Pleistocene epoch (0.8 to 0.01 million years ago).

and

predictions of equilibrium climate sensitivity (excluding long-term ice-albedo feedbacks) for our Pliocene-like future (with CO2 levels up to maximum Pliocene levels of 450 parts per million) are well described by the currently accepted range of an increase of 1.5 K to 4.5 K per doubling of CO2.

I find it very telling that they particularly exclude long-term ice-albedo feedbacks from their statements about ECS, while the ice-albedo feedback could readily be accelerated by modern issues such as: (a) abrupt collapse of marine terminating glaciers in Greenland and marine glaciers in Antarctica; (b) changes in snow/ice albedo from wildfires; (c) darkening of surface glacial ice due to successive seasons of surface melting such as in the GIS; (d) rapid reductions in Arctic and Antarctic sea ice extents; and (e) reductions of albedo in the tundra both due to accelerated growth of shrubs and reductions in the length of the snow cover seasons (due to early Springs and late Falls).

Edit: If ice-albedo is the major feedback change of an equable climate, this would account for the finding of the paper.
« Last Edit: February 07, 2015, 03:50:39 AM by AbruptSLR »
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wili

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Re: Conservative Scientists & its Consequences
« Reply #544 on: February 07, 2015, 07:10:03 AM »
LvdL +1
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

wili

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Re: Conservative Scientists & its Consequences
« Reply #545 on: February 07, 2015, 07:10:27 AM »
LvdL +2
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #546 on: February 07, 2015, 01:12:39 PM »
More from David Spratt on why 2 degrees could be reached within 20 years:
http://www.climatecodered.org/2015/02/two-degrees-of-warming-closer-than-you.html

Largely based on Michael Mann.

dorlomin

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Re: Conservative Scientists & its Consequences
« Reply #547 on: February 07, 2015, 01:42:56 PM »
You may want to consider that "where there is smoke there is fire", and where there is troll-like behavior, there may well be a troll.
Wow...... disagreeing with you is "trolling"?
Take it for granted you are wrong.
Just try to work out what about and why.

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Re: Conservative Scientists & its Consequences
« Reply #548 on: February 07, 2015, 04:06:09 PM »
Don't panick. We're safe on Spaceship Titanic.

Need I point out the depressing fact that we are already on spaceship Titantic.   :-[

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #549 on: February 07, 2015, 04:06:55 PM »
You may want to consider that "where there is smoke there is fire", and where there is troll-like behavior, there may well be a troll.
Wow...... disagreeing with you is "trolling"?

First, Michael Hauber has previously posted that he was "entering troll-mode" for his response.  Thus if he is sensitive to the use of such language then he should not use it himself (To quote Teddy Roosevelt:  "If you can't stand the heat, get out of the kitchen."

Second, I would like to point out that AR5 contains so many caveats that in a non-stationary (changing) Earth Systems and analysis situation it is difficult for anyone (particularly Michael Hauber) to speak with any authority as to exactly what AR5 does or doesn't indicate/imply about the future.  For example:

(a) To clarify the meaning of AR5, the IPCC issued guidance regarding the carbon budget required to stay below a 2 C, and when I provided discussion indicating how conservative (erring on the side of least drama) the IPCC was in creating this carbon budget (e.g. using the RCP 2.6 rate of emissions rather than the actual BAU rate of emissions that we have been following since the IPCC created its carbon budget guidance, etc), Michael distorted the IPCC's statements on this matter; and

(b) When I indicated that the IPCC used frequency counts to characterize the probabilities the RCP scenarios represent, Michael distorted this fundamental aspect of the IPCC's process as indicated in the following linked IPCC documents related to how the RCP scenarios were created.  This documentation indicates that while the scenarios were chosen to map a broad range of climate outcomes (see extract below), at a minimum, RCP 8.5 and RCP 2.6 would constructed to represent the 90th and the 10th percentile of the post-SRES literature (see attached associated figures) available on climate forcing scenarios when the RCP pathways were developed. 

http://www.ipcc.ch/pdf/supporting-material/expert-meeting-ts-scenarios.pdf

http://www.webpages.uidaho.edu/envs501/downloads/Moss%20et%20al.%202010.pdf

Extract: "The RCPs provide a starting point for new and wide-ranging research. However, it is important to recognize their uses and limits.  They are neither forecasts nor policy recommendations, but were chosen to map a broad range of climate outcomes. The RCPs cannot be treated as a set with consistent internal logic. For example, RCP8.5 cannot be used as a no-climate-policy reference scenario for the other RCPs because RCP8.5’s socioeconomic, technology and biophysical assumptions differ from those of the other RCPs."
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