Conservative Scientists & its Consequences

[AbruptSLR]

While Bjorn Stevens has publically tried to distance himself from denialists (like Nic Lewis), his publically announced efforts to influence policy makers to consider low climate sensitivity values, leaves his research open to manipulation and distortion by denalists.  Furthermore, the following linked reference by Mauritsen & Bjorn (2015), speculates that deep convective mixing in the dry and clear portions of the tropical atmosphere may (or may not) create cloud patterns that promote negative feedback, in an opposite manner to the possible mechanism cited by Sherwood et al (2014) who cites that near equatorial deep convective atmospheric mixing may create high altitude clouds [as observed by satellite records as noted by Marvel (2015)] that produce positive feedback and a possibly high climate sensitivity.  It will likely take some years before the confusion around this controversial topic is reduced sufficiently for policy makers to take appropriate action; and in the meantime society will continue to lean further in the BAU direction than may be advisable.

Thorsten Mauritsen & Bjorn Stevens (2015), "Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models", Nature Geoscience, doi:10.1038/ngeo2414


http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2414.html


Abstract: "Equilibrium climate sensitivity to a doubling of CO2 falls between 2.0 and 4.6 K in current climate models, and they suggest a weak increase in global mean precipitation. Inferences from the observational record, however, place climate sensitivity near the lower end of this range and indicate that models underestimate some of the changes in the hydrological cycle. These discrepancies raise the possibility that important feedbacks are missing from the models. A controversial hypothesis suggests that the dry and clear regions of the tropical atmosphere expand in a warming climate and thereby allow more infrared radiation to escape to space. This so-called iris effect could constitute a negative feedback that is not included in climate models. We find that inclusion of such an effect in a climate model moves the simulated responses of both temperature and the hydrological cycle to rising atmospheric greenhouse gas concentrations closer to observations. Alternative suggestions for shortcomings of models — such as aerosol cooling, volcanic eruptions or insufficient ocean heat uptake — may explain a slow observed transient warming relative to models, but not the observed enhancement of the hydrological cycle. We propose that, if precipitating convective clouds are more likely to cluster into larger clouds as temperatures rise, this process could constitute a plausible physical mechanism for an iris effect."

[AbruptSLR]

The extract from the linked article indicates that black carbon is responsible for more than 30 percent of recent warming the Arctic; which exceeds the black carbon radiative forcing contribution assumed in RCP 8.5.

http://thinkprogress.org/climate/2015/04/21/3648934/kerry-arctic-council/

Extract: "Scientists say black carbon pollution may be responsible for more than 30 percent of recent warming in the Arctic. Whether it is deposited by local sources or drifts in from lower latitudes black carbon pollution covers ice and snow with a sooty heat-trapping blanket. This accelerates warming by reducing the reflectivity of Arctic snow and ice, and by melting sea ice into the dark ocean waters that absorb more heat.
 
The United States is responsible for 61 percent of black carbon pollution from Arctic nations. Globally, the U.S. and other Arctic Council members and observer countries — including China, India, Japan, South Korea, Germany, and the United Kingdom — contribute more than 60 percent of black carbon pollution."

[AbruptSLR]

I was attributing it as a mistake to Beth Miller. Did Rajan Chakrabarty produce that phrase? If so I may be mis-attributing it by not tracing it far enough.


I took 'earth's land mass' to mean area of land on earth (in which case 3.8% wouldn't be right either) but perhaps mass really did mean soil mass as you suggest. I added a question mark to 'failed to apply common sense' making it a question and your answer would seem to indicate possibly not. That does seem to be a interpretation that looks rather charitable.

While it is plausible that Beth Miller misinterpreted Rajan Chakrabarty's work, and that she (& I by extension) implied to the reader that 75% of the existing soil mass of the earth was peat (for which your/my extant non-frozen peat surface area value of 3.8% would be more relevant in the short-term); I believe that in the long-term (centuries) it is important to consider all of the Earth's soil with "high-moisture-containing fuel", as the permafrost (both NH & SH with different timeframes) & the wetlands are even more important plausible sources of brown carbon emissions with continued global warming.

Per Schuur et al (2015) the carbon in the Arctic permafrost (see associated attached image & extract) may approach 2,000 billion tonnes, thus far exceeding the carbon in non-frozen peatlands (which jai cites as being around 600 billion tonnes.

E. A. G. Schuur, A. D. McGuire, C. Schädel, G. Grosse, J. W. Harden, D. J. Hayes, G. Hugelius, C. D. Koven, P. Kuhry, D. M. Lawrence, S. M. Natali, D. Olefeldt, V. E. Romanovsky, K. Schaefer, M. R. Turetsky, C. C. Treat & J. E. Vonk (09 April 2015), "Climate change and the permafrost carbon feedback", Nature, Volume: 520, Pages: 171–179, doi:10.1038/nature14338



http://www.nature.com/nature/journal/v480/n7375/full/480032a.html

Extract: "Taken together, the known pool of terrestrial permafrost carbon in the northern permafrost zone is 1,330–1,580 Pg carbon, accounting for surface carbon as well as deep carbon in the yedoma region and river deltas, with the potential for ~400 Pg carbon in other deep terrestrial permafrost sediments that, along with an additional quantity of subsea permafrost carbon, still remains largely unquantified."

[Sleepy]

Quote of week 16.

The public has been brainwashed and have stopped caring about reality.
Lennart Bengtsson

And oh, sea level rise is nothing to worry about. It's been steady and low for the last hundred years.

[AbruptSLR]

The linked reference shows that future changes to clouds will cause slightly more warming, which is a net positive feedback currently not accounted for by AR5.

Kevin Trenberth, Yongxin Zhang, John Fasullo, and Shoichi Taguchi (2015), "Climate variability and relationships between top-of-atmosphere radiation and temperatures on Earth", Journal of Geophysical Research Atmospheres, DOI: 10.1002/2014JD022887

http://onlinelibrary.wiley.com/doi/10.1002/2014JD022887/full

Abstract: "The monthly global and regional variability in Earth's radiation balance is examined using correlations and regressions between atmospheric temperatures and water vapor with top-of-atmosphere outgoing longwave (OLR), absorbed shortwave (ASR) and net radiation (RT=ASR-OLR). Anomalous global mean monthly variability in the net radiation is surprisingly large, often more than ±1 W m−2, and arises mainly from clouds and transient weather systems. Relationships are strongest and positive between OLR and temperatures, especially over land for tropospheric temperatures, except in the deep tropics where high sea surface temperatures are associated with deep convection, high cold cloud-tops and thus less OLR but also less ASR. Tropospheric vertically-averaged temperatures (surface-150 hPa) are thus negatively correlated globally with net radiation (−0.57), implying 2.18±0.10 W m−2 extra net radiation to space for 1°C increase in temperature. Water vapor is positively correlated with tropospheric temperatures and thus also negatively correlated with net radiation, however when the temperature dependency of water vapor is statistically removed, a significant positive feedback between water vapor and net radiation is revealed globally with 0.87 W m−2 less OLR to space per mm of total-column water vapor. The regression coefficient between global RT and tropospheric temperature becomes −2.98 W m−2K−1 if water vapor effects are removed, slightly less than expected from black-body radiation (−3.2 W m−2K−1), suggesting a positive feedback from clouds and other processes. Robust regional structures provide additional physical insights. The observational record is too short, weather noise too great and forcing too small to make reliable estimates of climate sensitivity."

Quote from Dr. Trenberth:
"So what we have done here is to look at feedbacks and relationships that relate to climate sensitivity. A number of studies have analyzed the observations, and recent changes in Earth’s temperature, to say something about climate sensitivity. We claim that none of them are really meaningful because there is too much variability in the short record (since 2000 when CERES became active). What we do find is that if one looks at tropospheric average temperature rather than surface temperature, then there is a much stronger relationship with energy flow at the top of the Earth’s atmosphere. We are able to find a water vapor signal that is clearly a positive feedback."

See also:
http://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/apr/23/changes-in-water-vapor-and-clouds-are-amplifying-global-warming

https://www.skepticalscience.com/changes-in-water-vapor-clouds-amplifying-warming.html

[Sleepy]

May I add a couple of things to my "Quote of week 16" above since this thread is about conservative scientists? Bengtsson doesn't share the view that clouds will cause more warming, they are the balancing factor. Unfortunately without further explanations. He did confirm that ECS is at least 2°C. He also noted that the participants at Ringberg were young and that 35% of them were females with excellent presentations.

Ah well, I'll drop that (him) now...

[AbruptSLR]

May I add a couple of things to my "Quote of week 16" above since this thread is about conservative scientists? Bengtsson doesn't share the view that clouds will cause more warming, they are the balancing factor. Unfortunately without further explanations. He did confirm that ECS is at least 2°C. He also noted that the participants at Ringberg were young and that 35% of them were females with excellent presentations.

Ah well, I'll drop that (him) now...

For those not aware of the controversy around Bengtsson's climate change skepticism, I provide a link to an Der Spiegel article explaining that he is out of step with the majority climate change scientists (who in my opinion all too frequently already err on the side of least drama):

http://www.spiegel.de/international/world/climate-scientists-mixed-over-controversy-surrounding-respected-researcher-a-971033.html

[Michael Hauber]

While Bjorn Stevens has publically tried to distance himself from denialists (like Nic Lewis), his publically announced efforts to influence policy makers to consider low climate sensitivity values, leaves his research open to manipulation and distortion by denalists.  Furthermore, the following linked reference by Mauritsen & Bjorn (2015), speculates that deep convective mixing in the dry and clear portions of the tropical atmosphere may (or may not) create cloud patterns that promote negative feedback, in an opposite manner to the possible mechanism cited by Sherwood et al (2014) who cites that near equatorial deep convective atmospheric mixing may create high altitude clouds [as observed by satellite records as noted by Marvel (2015)] that produce positive feedback and a possibly high climate sensitivity.  It will likely take some years before the confusion around this controversial topic is reduced sufficiently for policy makers to take appropriate action; and in the meantime society will continue to lean further in the BAU direction than may be advisable.

Thorsten Mauritsen & Bjorn Stevens (2015), "Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models", Nature Geoscience, doi:10.1038/ngeo2414


http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2414.html


Abstract: "Equilibrium climate sensitivity to a doubling of CO2 falls between 2.0 and 4.6 K in current climate models, and they suggest a weak increase in global mean precipitation. Inferences from the observational record, however, place climate sensitivity near the lower end of this range and indicate that models underestimate some of the changes in the hydrological cycle. These discrepancies raise the possibility that important feedbacks are missing from the models. A controversial hypothesis suggests that the dry and clear regions of the tropical atmosphere expand in a warming climate and thereby allow more infrared radiation to escape to space. This so-called iris effect could constitute a negative feedback that is not included in climate models. We find that inclusion of such an effect in a climate model moves the simulated responses of both temperature and the hydrological cycle to rising atmospheric greenhouse gas concentrations closer to observations. Alternative suggestions for shortcomings of models — such as aerosol cooling, volcanic eruptions or insufficient ocean heat uptake — may explain a slow observed transient warming relative to models, but not the observed enhancement of the hydrological cycle. We propose that, if precipitating convective clouds are more likely to cluster into larger clouds as temperatures rise, this process could constitute a plausible physical mechanism for an iris effect."

Sherwood et al find a higher positive feedback due to changes in low level clouds.  In particular they find that increased drying of lower levels will reduce the amount of low level cloud.  As low level cloud causes cooling, this will cause warming.  Sherwood does mention high cloud, but only to note that part of the positive feedback in current models is due to the fact that 'the temperature at the tops of the clouds do not increase much in warmer climates, which enhances their greenhouse effect.'.  Sherwood does not make any claim that the effect of high cloud should be higher or lower than what the models estimate.

Thorsten and Steven find that increased drying in the upper levels will reduce the amount of high cloud.  As Sherwood et al states, the models show this as a positive feedback, so this reduction in high cloud will cause a negative feedback.  The results of Sherwood et al and Thorsten and Steven are not incompatible.

The approach of Nic Lewis is to point to uncertainties in the model estimates as an excuse to dismiss the higher results he doesn't like and only focus on the lower results he does like.  You are using the same approach in reverse.  But the uncertainties that Nic points to are at least real - even as he ignores the fact that the results he does like have just as many uncertainties - whereas the excuses you use to ignore the results that are lower than you like are nonsense.

[wili]

rs covers that new Trenberth paper here: https://robertscribbler.wordpress.com/2015/04/23/new-study-finds-clouds-are-amplifying-human-warming/

[AbruptSLR]

The approach of Nic Lewis is to point to uncertainties in the model estimates as an excuse to dismiss the higher results he doesn't like and only focus on the lower results he does like.  You are using the same approach in reverse.  But the uncertainties that Nic points to are at least real - even as he ignores the fact that the results he does like have just as many uncertainties - whereas the excuses you use to ignore the results that are lower than you like are nonsense.

The only point of your post is to try to equate me to be a kind of negative Nic Lewis.  Why don't you spend your time trying to shine more light on the Trenberth et al 2015's latest findings like Robert Scribbler does in the link that wili provided.

[Sleepy]

May I add a couple of things to my "Quote of week 16" above since this thread is about conservative scientists? Bengtsson doesn't share the view that clouds will cause more warming, they are the balancing factor. Unfortunately without further explanations. He did confirm that ECS is at least 2°C. He also noted that the participants at Ringberg were young and that 35% of them were females with excellent presentations.

Ah well, I'll drop that (him) now...

For those not aware of the controversy around Bengtsson's climate change skepticism, I provide a link to an Der Spiegel article explaining that he is out of step with the majority climate change scientists (who in my opinion all too frequently already err on the side of least drama):

http://www.spiegel.de/international/world/climate-scientists-mixed-over-controversy-surrounding-respected-researcher-a-971033.html

Thanks, it's a bit easier for me to follow his ventriloquism here, since we share the same langage.

The world is full of real scientists. I don't fancy promoting any individual scientist, but here's one making a prediction that's hard to deny.

[jai mitchell]

Sherwood et al find a higher positive feedback due to changes in low level clouds.  In particular they find that increased drying of lower levels will reduce the amount of low level cloud.  As low level cloud causes cooling, this will cause warming. 

That's RIGHT!!!!  they do FIND that these things are happening, through precise observational techniques and rigorous data analysis, using the best scientific methods available today.

Thorsten and Steven find that increased drying in the upper levels will reduce the amount of high cloud.  As Sherwood et al states, the models show this as a positive feedback, so this reduction in high cloud will cause a negative feedback.  The results of Sherwood et al and Thorsten and Steven are not incompatible.

Haha! thats pretty funny mike.  You act like Thorsten and Stevens actually used observational science to derive a plausible argument for their hypothesis.  Here's a hint:  Thorsten and Steven didn't actually FIND anything!

From their abstract:

Inferences from the observational record, however, place climate sensitivity near the lower end of this range

and

We propose that, if precipitating convective clouds are more likely to cluster into larger clouds as temperatures rise, this process could constitute a plausible physical mechanism for an iris effect.

did you catch that?  They are basically proposing a re-animation of the zombie lie "Iris Effect" theory of Lindzen (2001) and through to Lindzen & Choi (2011).  This theory has been soundly debunked and Lindzen received considerable funding from Exxon during the formulation of this theory.

They also propose this theory of reanimation based on inference of the "pause" which has also been debunked and probably only made it through peer review by inserting the following discussion.

Alternative suggestions for shortcomings of models — such as aerosol cooling, volcanic eruptions or insufficient ocean heat uptake — may explain a slow observed transient warming relative to models

To assert that a conjectured hypothesis, based on simplistic denialist talking points is IN ANY WAY akin to real science based on observational data is ludicrous.   I am very surprised that you would give Thorsten and Stevens equal weight in comparison to other work in the field that is rigorous, thorough and based on actual science.

[wili]

That warmed-over-Lindzen Mauritsen and Stevens paper is discussed and dispatched nicely here by Andy Dessler himself:

http://www.realclimate.org/index.php/archives/2015/04/the-return-of-the-iris-effect/

The takeaway: "If the iris provided a strong negative feedback, then we would expect to see it in response to short-term climate fluctuations. Analysis of observations doesn’t show anything like that (Dessler, 2013)."

And there's this insightful note in the comments: "...given the paleoclimate evidence for abrupt climate changes... there is likely no strong negative feedback over any meaningful time scale..."

[AbruptSLR]

We should not forget that the IPCC directly states that what is acceptable risk for a "Carbon Budget" global mean surface temperature increase, GMT, goal is a political & not a scientific matter.  Thus in 2009 at CoP15 in Copenhagen, when researchers such as Smith et al (2009) suggested lowering the GMT goal from 2 C to 1.5 C, this was not (and has not yet been) accepted as a new definition of acceptable risk.  Furthermore, we should remember that Rogelj et al. 2012 (note Rogelj was one of the primary authors of the RCP scenarios) provided updates on equilibrium climate sensitivity, ECS, and on new higher Recommended Concentration Pathways shown in the attached image; thus indicating that actual risks of anthropogenic radiative forcing are higher than assumed by AR5.  Thus before AR5 was issued we had been adequately warned both the likely damage from radiative forcing was likely higher that the AR5 Carbon Budget assumed and that the rate of radiative forcing was also likely to be higher than the AR5 Carbon Budget assumed.  Since AR5 was issued we have also received adequate warning (from Sherwood, Trenberth, etc) that the climate sensitivity assumed by AR5's Carbon Budget is also likely to be too low.  To me this indicates that the AR5 scientists were likely influenced by politics to err on the side of least drama.

Smith Joel B., Stephen H. Schneider, Michael Oppenheimer, Gary W. Yohe, William Hare, Michael D. Mastrandrea, Anand Patwardhan, Ian Burton, Jan Corfee-Morlot, Chris. H. D. Magadza, Hans-Martin Füssel, A. Barrie Pittock, Atiq Rahman, Avelino Suarez, and Jean-Pascal van Ypersele, 2009. Assessing Dangerous Climate Change through an update of the Intergovernmental Panel on Climate Change (IPCC) “Reasons for Concern”. PNAS, 106(11), pp. 4133-4137
http://www.pnas.org/content/106/11/4133.full.pdf+html

Abstract: "Article 2 of the United Nations Framework Convention on Climate Change [United Nations (1992) http://unfccc.int/resource/docs/convkp/conveng.pdf. Accessed February 9, 2009] commits signatory nations to stabilizing greenhouse gas concentrations in the atmosphere at a level that ‘‘would prevent dangerous anthropogenic interference (DAI) with the climate system.’’ In an effort to provide some insight into impacts of climate change that might be considered DAI, authors of the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) identified 5 ‘‘reasons for concern’’ (RFCs). Relationships between various impacts reflected in each RFC and increases in global mean temperature (GMT) were portrayed in what has come to be called the ‘‘burning embers diagram.’’ In presenting the ‘‘embers’’ in the TAR,
IPCC authors did not assess whether any single RFC was more important than any other; nor did they conclude what level of impacts or what atmospheric concentrations of greenhouse gases would constitute DAI, a value judgment that would be policy prescriptive. Here, we describe revisions of the sensitivities of the RFCs to increases in GMT and a more thorough understanding of the concept of vulnerability that has evolved over the past 8 years.  This is based on our expert judgment about new findings in the growing literature since the publication of the TAR in 2001, including literature that was assessed in the IPCC Fourth Assessment Report (AR4), as well as additional research published since AR4. Compared with results reported in the TAR, smaller increases in GMT are now estimated to lead to significant or substantial consequences in the framework of the 5 ‘‘reasons for concern.’’"

Rogelj, J., Meinshausen, M. and Knutti, R., (2012), "Global warming under old and new scenarios using IPCC climate sensitivity range estimates", Nature Climate Change - Letters, doi: 10.1038/NCLIMATE1385.

[Michael Hauber]

The approach of Nic Lewis is to point to uncertainties in the model estimates as an excuse to dismiss the higher results he doesn't like and only focus on the lower results he does like.  You are using the same approach in reverse.  But the uncertainties that Nic points to are at least real - even as he ignores the fact that the results he does like have just as many uncertainties - whereas the excuses you use to ignore the results that are lower than you like are nonsense.

The only point of your post is to try to equate me to be a kind of negative Nic Lewis.  Why don't you spend your time trying to shine more light on the Trenberth et al 2015's latest findings like Robert Scribbler does in the link that wili provided.

There was also the point that the Thorsten paper is consistent with Sherwood paper, in contrast to your claim that they are inconsistent. 

As for the Trenberth finding - read the paper.  It calculates a climate sensitivty of 1.62, which is lower than what Thorsten finds (2.2).  Of course Trenberth sensitivity is a short term sensitivity that cannot be directly compared with Thorsten, but the point is obvious that Trenberth does not contradict Thorsten, or provide any evidence for a higher climate sensitivity than the IPCC range (2..

[Michael Hauber]

Sherwood et al find a higher positive feedback due to changes in low level clouds.  In particular they find that increased drying of lower levels will reduce the amount of low level cloud.  As low level cloud causes cooling, this will cause warming. 

That's RIGHT!!!!  they do FIND that these things are happening, through precise observational techniques and rigorous data analysis, using the best scientific methods available today.

Have you read the paper?  Or are you just making stuff up based on reading the abstract only?  Thorsten et al back up their analysis with just as much observation of changes in cloudiness as Sherwood et al.  Sherwood et al has just as much speculation about the implications and causes of the observed changes as Thorsten.

did you catch that?  They are basically proposing a re-animation of the zombie lie "Iris Effect" theory of Lindzen (2001) and through to Lindzen & Choi (2011).  This theory has been soundly debunked and Lindzen received considerable funding from Exxon during the formulation of this theory.

They also propose this theory of reanimation based on inference of the "pause" which has also been debunked and probably only made it through peer review by inserting the following discussion.

Alternative suggestions for shortcomings of models — such as aerosol cooling, volcanic eruptions or insufficient ocean heat uptake — may explain a slow observed transient warming relative to models

To assert that a conjectured hypothesis, based on simplistic denialist talking points is IN ANY WAY akin to real science based on observational data is ludicrous.   I am very surprised that you would give Thorsten and Stevens equal weight in comparison to other work in the field that is rigorous, thorough and based on actual science.

Lindzen said it first so it must be wrong?  Again if you read the whole paper you will see that Thorsten does enough observation to find that Lindzen seriously overestimated the IRIS effect by assuming that certain cloud changes that offset the IRIS effect only happen in the same location as tropical convection.  Whereas observations show that Lindzen failed to take into account the fact that the offsetting changes happen throughout the tropics, resulting in a far weaker IRIS effect than Lindzen originally proposed.

[Michael Hauber]

That warmed-over-Lindzen Mauritsen and Stevens paper is discussed and dispatched nicely here by Andy Dessler himself:

http://www.realclimate.org/index.php/archives/2015/04/the-return-of-the-iris-effect/

The takeaway: "If the iris provided a strong negative feedback, then we would expect to see it in response to short-term climate fluctuations. Analysis of observations doesn’t show anything like that (Dessler, 2013)."

And there's this insightful note in the comments: "...given the paleoclimate evidence for abrupt climate changes... there is likely no strong negative feedback over any meaningful time scale..."

Andy says nothing to disprove the paper.  He does state that there is no evidence for a strong negative feedback as Lindzen originally found.  But the Thorsten paper does not find a strong negative feedback, but a much weaker effect, which reduces climate sensitivity slightly.  As Andy himself says this study does not support Lindzen, but does the opposite and finds a much higher climate sensitivity than Lindzen finds.

And Desslers final comment 'Future research may validate this, or it may not', and 'Overall, I think the debate over the iris hypothesis is a testament to the efforts the scientific community '  A real climate scientist with expertise and a current publication obviously considers the paper to be interesting and useful work.  Members of this thread are far too quick to dismiss this as  zombie like resurrection of denier talking points that has nothing in common with real science.

[AbruptSLR]

The approach of Nic Lewis is to point to uncertainties in the model estimates as an excuse to dismiss the higher results he doesn't like and only focus on the lower results he does like.  You are using the same approach in reverse.  But the uncertainties that Nic points to are at least real - even as he ignores the fact that the results he does like have just as many uncertainties - whereas the excuses you use to ignore the results that are lower than you like are nonsense.

The only point of your post is to try to equate me to be a kind of negative Nic Lewis.  Why don't you spend your time trying to shine more light on the Trenberth et al 2015's latest findings like Robert Scribbler does in the link that wili provided.

There was also the point that the Thorsten paper is consistent with Sherwood paper, in contrast to your claim that they are inconsistent. 

As for the Trenberth finding - read the paper.  It calculates a climate sensitivty of 1.62, which is lower than what Thorsten finds (2.2).  Of course Trenberth sensitivity is a short term sensitivity that cannot be directly compared with Thorsten, but the point is obvious that Trenberth does not contradict Thorsten, or provide any evidence for a higher climate sensitivity than the IPCC range (2..

The following quote from Trenberth raises both the questions of: (a) whether the short-term observational data cited by Mauritsen & Stevens (2015) is too variable (PDO, ENSO, AMO, volcanic eruptions, aerosols, etc.) to support their claims; and (b) if Trenberth et al (2015) clearly identify a positive feedback associated with the vapor signal; then is the postulated weak negative iris feedback reasonable?

Furthermore, I find your comparison of two different types of climate sensitivities, and then drawing sweeping general conclusions that are not supported by any premise that you have stated.  Indeed, if Trenberth et al (2015) identify that the vapor signal provides a newly identified positive feedback, then when this new positive feedback is incorporated into the next generation of Earth System Models (say ACME) then the emergent climate sensitivity from such models will most plausibly be greater than the CMIP5 projections.

Quote from Dr. Trenberth:
"So what we have done here is to look at feedbacks and relationships that relate to climate sensitivity. A number of studies have analyzed the observations, and recent changes in Earth’s temperature, to say something about climate sensitivity. We claim that none of them are really meaningful because there is too much variability in the short record (since 2000 when CERES became active). What we do find is that if one looks at tropospheric average temperature rather than surface temperature, then there is a much stronger relationship with energy flow at the top of the Earth’s atmosphere. We are able to find a water vapor signal that is clearly a positive feedback."

[Michael Hauber]

The following quote from Trenberth raises both the questions of: (a) whether the short-term observational data cited by Mauritsen & Stevens (2015) is too variable (PDO, ENSO, AMO, volcanic eruptions, aerosols, etc.) to support their claims;

It is the same data that the studies you quote relies on.  There is the same effect of variability on the studies you quote as supporting a higher sensitivity.

and (b) if Trenberth et al (2015) clearly identify a positive feedback associated with the vapor signal; then is the postulated weak negative iris feedback reasonable?

The Thorsten version of the IRIS estimates climate sensitivity at 2.2.  Climate sensitivity without feedbacks is about 1.  Plenty of room for positive feedback such as water vapor and other feedbacks.  As the Iris is a negative feedback, then that is even more room for the negative and positives cancel out to reach 2.2.

Furthermore, I find your comparison of two different types of climate sensitivities, and then drawing sweeping general conclusions that are not supported by any premise that you have stated. 

My point is that the comparison cannot be made between the two papers.  It is you that wants to compare the 'high' feedbacks (enough for 1.6 sensitivity) in Trenberth to invalidate the 'low' feedbacks in Thorsten (enough for 2.2 sensitivity).

Indeed, if Trenberth et al (2015) identify that the vapor signal provides a newly identified positive feedback, then when this new positive feedback is incorporated into the next generation of Earth System Models (say ACME) then the emergent climate sensitivity from such models will most plausibly be greater than the CMIP5 projections.

The water vapor feedback was discovered over a century ago.  If you think it is new you do not understand one of the most basic facts in climate sensitivity.

Quote from Dr. Trenberth:
"So what we have done here is to look at feedbacks and relationships that relate to climate sensitivity. A number of studies have analyzed the observations, and recent changes in Earth’s temperature, to say something about climate sensitivity. We claim that none of them are really meaningful because there is too much variability in the short record (since 2000 when CERES became active). What we do find is that if one looks at tropospheric average temperature rather than surface temperature, then there is a much stronger relationship with energy flow at the top of the Earth’s atmosphere. We are able to find a water vapor signal that is clearly a positive feedback."

Which of course means that the studies that say what ASLR wants them to say are valid, and the ones that say something different are rubbish even though both studies are based on the same length of record.  Note that the Thorsten result does not analyse recent changes in temperature to say something about climate sensitivity.  Rather it finds in observations evidence that high clouds change as temperature change.  The models are then tweaked to reflect this relationship, and two things happen.  First climate sensitivity is reduced.  And second changes to the hydrological cycle become more intense.  This results in a better match between models and reality for both temperature and the hydrological cycle.

An important point in Thorsten is that if the Iris effect works the way that Thorsten finds, then it may not necessarily be good news.  On one hand we get less warming, but on the other hand we get more drying in the subtropics, and more intense rainfall in the tropics.  And if I guess right then the increased tendency of tropical convection to gather into larger clusters will also lead to more intense hurricanes.  And possibly intensification of the ENSO cycle as larger convective clusters would drive an intensified MJO, resulting in a larger push on the ENSO cycle.

[AbruptSLR]

Michael,

In general terms you are like a one-trick-pony; where all that you can do is point to overly-simplified studies that rely too heavily on observational data dominated by the hiatus period (thus essentially cherry-picking their data as well as their model assumptions), and do not adequately account for issues like aerosols, ocean heat uptake and long-period oscillations.

In Reply #804, I link to the Trenberth et al 2015 paper from which the following extract comes from:

Extract: "The observational record is too short, weather noise too great and forcing too small to make reliable estimates of climate sensitivity."

What I pointed out is that Trenberth et al 2015 have identified a positive feedback that when added to a state-of-the-art ESM (like ACME) will project a higher climate sensitivity than without the positive feedback.

As I do not trust the cherry-picked, overly-simplistic, models & data that you point to, we will likely need to wait another two & a half years until the more meaningful ACME projections are available.

ASLR

[jai mitchell]

  Whereas observations show that Lindzen failed to take into account the fact that the offsetting changes happen throughout the tropics, resulting in a far weaker IRIS effect than Lindzen originally proposed.

oh really???

What were their observations based on?

Don't you find it a little disingenuous to assert these things when they are absolutely not true?

[Steven]

Indeed, if Trenberth et al (2015) identify that the vapor signal provides a newly identified positive feedback, then when this new positive feedback is incorporated into the next generation of Earth System Models (say ACME) then the emergent climate sensitivity from such models will most plausibly be greater than the CMIP5 projections.

Er, it's well-known that the water vapor feedback is positive.  That is not a "new" result.  E.g. see Fig. 9.43(a) of the AR5 report, shown below (WV stands for water vapor feedback).  From my cursory reading of the Trenberth et al. 2015 paper, it's not clear to me whether or not that paper would suggest higher climate sensitivity than the CMIP5 models.

[AbruptSLR]

Indeed, if Trenberth et al (2015) identify that the vapor signal provides a newly identified positive feedback, then when this new positive feedback is incorporated into the next generation of Earth System Models (say ACME) then the emergent climate sensitivity from such models will most plausibly be greater than the CMIP5 projections.

Er, it's well-known that the water vapor feedback is positive.  That is not a "new" result.  E.g. see Fig. 9.43(a) of the AR5 report, shown below (WV stands for water vapor feedback).  From my cursory reading of the Trenberth et al. 2015 paper, it's not clear to me whether or not that paper would suggest higher climate sensitivity than the CMIP5 models.

Er, to state the more than obvious, the well-know water vapor feedback that you are referencing is different than the signal that Trenberth points-out in his & his co-author's 2015 paper.  Both you and MH seem to be very insistent on mixing different time-scales and size-scales in order to compare apples to oranges.  If I did not think that some readers would be confused by your misdirections I would not both to respond.

[Csnavywx]

There is little to no support for any "Iris effect". This paper merely shows that if it did exist, the effect would be pretty weak. That's kind of the point of the paper.

The key point is that the paper itself did not show any iris effect or indeed any physical mechanisms to create one. They merely (effectively) changed condensation and precipitation efficiency by artificially enhancing the rate of cloud condensation to rain inside of a convective parameterization scheme.

Even at the maximum setting used (where the effective iris effect is maximized), it reduced ECS from 2.8K to 2.2K.

Trenberth et. al's conclusions merely include room for a positive cloud feedback. I believe on the order of (up to) 0.3 W/m2*K.

[AbruptSLR]

Indeed, if Trenberth et al (2015) identify that the vapor signal provides a newly identified positive feedback, then when this new positive feedback is incorporated into the next generation of Earth System Models (say ACME) then the emergent climate sensitivity from such models will most plausibly be greater than the CMIP5 projections.

Er, it's well-known that the water vapor feedback is positive.  That is not a "new" result.  E.g. see Fig. 9.43(a) of the AR5 report, shown below (WV stands for water vapor feedback).  From my cursory reading of the Trenberth et al. 2015 paper, it's not clear to me whether or not that paper would suggest higher climate sensitivity than the CMIP5 models.

Er, to state the more than obvious, the well-know water vapor feedback that you are referencing is different than the signal that Trenberth points-out in his & his co-author's 2015 paper.  Both you and MH seem to be very insistent on mixing different time-scales and size-scales in order to compare apples to oranges.  If I did not think that some readers would be confused by your misdirections I would not both to respond.

For those who don't want to click around for discussion on Trenbreth et al (2015), I provide the following extracts from Skeptical Science indicating both that: (a) the vapor signal that Trenberth identifies is occurring on short-term weather timeframes like weeks to a month; and (b) with continuing anthropogenic radiative forcing this positive feedback will lead to increased global warming.

https://www.skepticalscience.com/changes-in-water-vapor-clouds-amplifying-warming.html

Extract: "What the authors then asked is, how does this imbalance change? It turns out, the imbalance changes a lot over time. On a monthly basis the balance might change 1 Watt per square meter of surface area. The changes are caused principally by changes to clouds and water vapor, and other short-term weather patterns. Clouds have the ability to reflect sunlight back to space; however, clouds also have the ability to trap more heat within the Earth’s atmosphere. So, short-term fluctuations in clouds have large impacts on the net rate of heat gain by the Earth.
The authors also correlated the observed temperatures, the amount of water vapor in the atmosphere, and the flow of radiant energy to explore how they affect each other. They found a strong relationship between the outgoing long wavelength radiation (infrared energy) and temperature; however, this relationship varies substantially across the planet. In fact, the relationship switches sign in some regions, such as the tropics. Measurements of the absorbed incoming radiation from the sun provided direct indications of the effects of clouds on that quantity.

…
What the present paper shows is that future changes to clouds will cause slightly more warming. Scientists describe clouds as a “positive feedback” on global warming."

[Steven]

Trenberth et. al's conclusions merely include room for a positive cloud feedback. I believe on the order of (up to) 0.3 W/m2*K.

Yes, and this is consistent with the results from CMIP3/CMIP5 climate models.  Cloud feedback is positive for practically all the CMIP3/CMIP5 models, as also shown in the IPCC graph that I posted upthread (in which the 'C' on the horizontal axis stands for cloud feedback):

[AbruptSLR]

Trenberth et. al's conclusions merely include room for a positive cloud feedback. I believe on the order of (up to) 0.3 W/m2*K.

Yes, and this is consistent with the results from CMIP3/CMIP5 climate models.  Cloud feedback is positive for practically all the CMIP3/CMIP5 models, as also shown in the IPCC graph that I posted upthread (in which the 'C' on the horizontal axis stands for cloud feedback):

Not to be the master of the obvious, but the positive cloud feedback for this CMIP3/CMIP5 graph illustrates that the Thorsten Mauritsen & Bjorn Stevens (2015) paper is only presenting the findings of a thought experiment to see what would happen if an iris effect existed; while in actuality there is very little support for a weak negative iris effect (as previously pointed out by Csnavywx).

Edit: Furthermore, as noted by Steven in his Reply #761: "The CMIP5 model spread in Equilibrium Climate Sensitivity ranges from 2.1°C to 4.7°C, e.g. see here, page 745."  Thus the Trenberth et al 2015 findings likely exclude ECS values below 2.1 C while supporting ECS values of at least up to 4.7 C; with a mean value of 3.4 C which is well above that AR5's Carbon Budget is based on.

[AbruptSLR]

The linked reference (with an open access pdf) notes that the AR5 SLR projections do not include the very significant albedo reduction observed for the Greenland Ice Sheet.  Therefore, AR5 once again errs on the side of least drama (i.e. its projections transfers risk to the public what encouraging policy makers to spend less money on safeguarding the common good).


Goelles, T., Bøggild, C. E., and Greve, R. (2015), "Ice sheet mass loss caused by dust and black carbon accumulation", The Cryosphere Discuss., 9, 2563-2596, doi:10.5194/tcd-9-2563-2015.

http://www.the-cryosphere-discuss.net/9/2563/2015/tcd-9-2563-2015.pdf

Abstract: "Albedo is the dominating factor governing surface melt variability in the ablation area of ice sheets and glaciers. Aerosols such as mineral dust and black carbon (soot) accumulate on the ice surface and cause a darker surface and therefore a lower albedo. The dominant source of these aerosols in the ablation area is melt-out of englacial material which has been transported via ice flow. The darkening effect on the ice surface is currently not included in sea level projections, and the effect is unknown. We present a model framework which includes ice dynamics, aerosol transport, aerosol accumulation and the darkening effect on ice albedo and its consequences for surface melt. The model is applied to a simplified geometry resembling the conditions of the Greenland ice sheet, and it is forced by several temperature scenarios to quantify the darkening effect of aerosols on future mass loss. The effect of aerosols depends non-linearly on the temperature rise due to the feedback between aerosol accumulation and surface melt. The effect of aerosols in the year 3000 is up to 12% of additional ice sheet volume loss in the warmest scenario."

[Michael Hauber]

  Whereas observations show that Lindzen failed to take into account the fact that the offsetting changes happen throughout the tropics, resulting in a far weaker IRIS effect than Lindzen originally proposed.

oh really???

What were their observations based on?

Don't you find it a little disingenuous to assert these things when they are absolutely not true?

Ok I shouldn't have gone on memory on this point, Thorsten's claim that Lindzen fails to take into account high cloud reductions throughout the tropics is based on modelling not observations.

However on the point of the study being based on observations, quoted directly from the paper:

'We approach the question differently, and instead investigate whether the presence of an iris effect would lead to other physical changes that might be more readily observed.'

The detection of the IRIS effect is not as you claim based only on the fact that putting it into climate model makes a better fit - although this is one of the significant arguments made in the paper, but it is based on observations, albeit indirect.  In particular Thorsten analyses changes how radiation changes with temperature in general, and compares this with the changes in radiation vs temperature for cloud free regions.  Thorsten also references previous papers which do make direct observations of cloud changes as part of his argument.

Lindzen's original paper does find direct observational evidence for a reduction in high cloud with a rise in temperature.  Other scientists who have studied the IRIS effect and found it not significant did not challenge this aspect.  Rather Lin et al 2002  found that as the clouds had a different radiative profile to what Lindzen used that the effect was a small positive feedback, and Fu et al 2002 also accepted the reduction in high cloud, but found Lindzen underestimated water vapor feedback and overestimated the high cloud feedback, and found an effect roughly 1/3rd the size - which would probably put ECS close to what Thorsten finds.

[Michael Hauber]

Michael,

In general terms you are like a one-trick-pony; where all that you can do is point to overly-simplified studies that rely too heavily on observational data dominated by the hiatus period (thus essentially cherry-picking their data as well as their model assumptions), and do not adequately account for issues like aerosols, ocean heat uptake and long-period oscillations.

In Reply #804, I link to the Trenberth et al 2015 paper from which the following extract comes from:

Extract: "The observational record is too short, weather noise too great and forcing too small to make reliable estimates of climate sensitivity."

Thorsten does not estimate climate sensitivity using the observational record.  They infer changes in cloud properties from the observational record.  They then calculate climate sensitivity from a model based on the infered changes in cloud properties. 

And as I said before the studies that you hold up in evidence of a high climate sensitivity, are based on the same time period.  Will you explain why you think the time period impacts on Thorsten et al, but does not impact on Trenberth et al?  Or will you turn a blind eye to this fact as it is inconvenient?

What I pointed out is that Trenberth et al 2015 have identified a positive feedback that when added to a state-of-the-art ESM (like ACME) will project a higher climate sensitivity than without the positive feedback.

Do you think climate scientists are idiots and will add the water vapor feedback to their models twice?  Or do you think Trenberth has discovered a new water vapor feedback that is different to the water vapor feedback known for over one hundred years?

As I do not trust the cherry-picked, overly-simplistic, models & data that you point to, we will likely need to wait another two & a half years until the more meaningful ACME projections are available.

ASLR

Nothing in cherry-picked - Thorsten et al use the entire data record.  And in what way is the study simplistic?  And how would that make it wrong even if it was?

[Michael Hauber]

There is little to no support for any "Iris effect". This paper merely shows that if it did exist, the effect would be pretty weak. That's kind of the point of the paper.

The key point is that the paper itself did not show any iris effect or indeed any physical mechanisms to create one. They merely (effectively) changed condensation and precipitation efficiency by artificially enhancing the rate of cloud condensation to rain inside of a convective parameterization scheme.

See my previous response to see that they did more than artifically tweak a model.  The paper also does discuss a mechanism - convective clustering.

Even at the maximum setting used (where the effective iris effect is maximized), it reduced ECS from 2.8K to 2.2K.

A maximised IRIS effect according to the paper actually gives a climate sensitivity of between 1.2 and 1.6 degrees.  It is after various weakening effects are added that the climate sensitivity is increased to 2.2 degrees.

[AbruptSLR]

One-trick-ponies point over-and-over again to the modern observational record that is dominated by the faux hiatus period from say 1999 to say 2013 to promote low values of climate sensitivity.  Clearly this record is not long enough to get a clear (low noise) climate sensitivity signal that accounts for such factors as the PDO cycle (we have just entered a positive phase of this cycle & thus do not yet have the benefit of data from the full positive phase of this cycle, while the faux hiatus period does include a full negative phase of the PDO cycle), anthropogenic aerosols, ocean heat uptake & ocean thermal inertia, volcanoes, incomplete instrument coverage (particularly in the polar regions as indicated by Cowtan & Way).  This is why since the beginning of this thread I have recommended focusing on improving state-of-the-art ESMs in order to get an appropriately inclusive estimate of climate sensitivity (note that the AR5 Carbon Budget does not use climate sensitivity values based on the CMIP5 projections (with a mean ECS of 3.4C) but rather uses its "process" that is subject to manipulation by one-trick-ponies to reduce this down into ECS values in the 3 to 3.2C range).

In this light while Goddard Space Center (headed by Gavin Schmidt) was heavily involved in the CMIP5 modeling effort, and thus one would expect Gavin Schmidt to support the likely 2.1 to 4.7C ECS range reported for the CMIP5 projections; nevertheless, after the Ringberg workshop at the linked RealClimate web article below; after considering all of the extant evidence Schmidt increased this likely range for ECS to 2 to 5C (with a mean value of 3.5C).  I note that Gavin Schmidt's increased likely ECS range includes his evaluation of recent input from Sherwood, Fasullo, Marvel, Geoffroy, Stevens, Lewis, etc; but many not have included consideration of the Trenbreth et al (2015) finding as Trenbreth & his co-authors did not present at the Ringberg workshop.  Furthermore, one-trick-ponies too frequently hide behind the uncertainties remaining about the impact of aerosols, while Shindell & others are working to cut this uncertainty in half by 2030.


http://www.realclimate.org/index.php/archives/2015/04/reflections-on-ringberg/


Turning to the weather related positive feedback vapor signal identified by Trenberth et al (2015) no CMIP5 model had a sufficiently fine model mesh resolution to appropriately account for the impact of this weather related vapor signal positive feedback (that is likely connected to tropical deep atmospheric convection that can only be properly modeled by use of a high resolution mesh); which is why I suspect that the ACME program (with higher resolution) will demonstrate a still higher climate sensitivity than that emergent from the CMIP5 projections.  In this regard, I remind the readers that while the ACME program runs 10-days, the company Kitware has been hired by the DOE to focus, in the first 3-year phase, on three key goals [focused on water cycle, biochemistry, and cryosphere systems].

http://www.prweb.com/releases/2015/02/prweb12539509.htm

Extract: "For each science driver, a question was selected to be answered in a three-year time range. Further questions will be answered over the course of the 10-year project. Questions to be answered in the next three years include: How will more realistic portrayals of features important to the water cycle (resolution, clouds, aerosols, snowpack, river routing, and land use) affect river flow and associated freshwater supplies at the watershed scale? How do carbon, nitrogen, and phosphorus cycles regulate climate system feedback, and how sensitive are these feedback to model structural uncertainty? Could a dynamical instability in the Antarctic Ice Sheet be triggered within the next 40 years?

In regards to the water cycle, ACME’s Project Strategy and Initial Implementation Plan states that changes in river flow over the last 40 years have been dominated primarily by land management, water management, and climate change associated with aerosol forcing. During the next 40 years, greenhouse gas (GHG) emissions in a business-as-usual scenario will produce changes to river flow.
 
As the plan states, a goal of ACME is to simulate the changes in the hydrological cycle, with a specific focus on precipitation and surface water in orographically complex regions such as the western United States and the headwaters of the Amazon.

To address biogeochemistry, ACME researchers will examine how more complete treatments of nutrient cycles affect carbon-climate system feedback, with a focus on tropical systems, and investigate the influence of alternative model structures for below-ground reaction networks on global-scale biogeochemistry-climate feedback.

For cyrosphere, the team will examine the near-term risks of initiating the dynamic instability and onset of the collapse of the Antarctic Ice Sheet due to rapid melting by warming waters adjacent to the ice sheet grounding lines.

The experiment would be the first fully-coupled global simulation to include dynamic ice shelf-ocean interactions for addressing the potential instability associated with grounding line dynamics in marine ice sheets around Antarctica."

[jai mitchell]

although this is one of the significant arguments made in the paper, but it is based on observations, albeit indirect.  In particular Thorsten analyses changes how radiation changes with temperature in general, and compares this with the changes in radiation vs temperature for cloud free regions. 

But the uncertainties that Michael Hauber points to are at least real - even as he ignores the fact that the results he does like have just as many uncertainties.

Using CERES radiation data and attempting to correlate it in the tropics is an exercise in frivolity.   Just looking at the regression analysis shows that even if ALL inputs were properly identified and paramaterized there would only be the barest of correlations.  How much do you want to bet that he underestimated the impact of burning peat in Indonesia, a process that we already know puts more aerosols into the environment than other types of fires AND was responsible for 13% to 40% of ALL anthropogenic Carbon Dioxide emissions in the year 1998.



So who is latching onto the results that they like now mike?

http://www.ncbi.nlm.nih.gov/pubmed/12422213
The amount of carbon released from peat and forest fires in Indonesia during 1997
Page et. al. (2002)

Tropical peatlands are one of the largest near-surface reserves of terrestrial organic carbon, and hence their stability has important implications for climate change. In their natural state, lowland tropical peatlands support a luxuriant growth of peat swamp forest overlying peat deposits up to 20 metres thick. Persistent environmental change-in particular, drainage and forest clearing-threatens their stability, and makes them susceptible to fire. This was demonstrated by the occurrence of widespread fires throughout the forested peatlands of Indonesia during the 1997 El Niño event. Here, using satellite images of a 2.5 million hectare study area in Central Kalimantan, Borneo, from before and after the 1997 fires, we calculate that 32% (0.79 Mha) of the area had burned, of which peatland accounted for 91.5% (0.73 Mha). Using ground measurements of the burn depth of peat, we estimate that 0.19-0.23 gigatonnes (Gt) of carbon were released to the atmosphere through peat combustion, with a further 0.05 Gt released from burning of the overlying vegetation. Extrapolating these estimates to Indonesia as a whole, we estimate that between 0.81 and 2.57 Gt of carbon were released to the atmosphere in 1997 as a result of burning peat and vegetation in Indonesia. This is equivalent to 13-40% of the mean annual global carbon emissions from fossil fuels, and contributed greatly to the largest annual increase in atmospheric CO(2) concentration detected since records began in 1957 (ref. 1).

see also:

Indonesian wildfires of 1997: Impact on tropospheric chemistry
Duncan et. al. (2003)
http://onlinelibrary.wiley.com/doi/10.1029/2002JD003195/pdf

The net direct, shortwave radiative forcing at the top of the atmosphere of OC and BC
aerosols from the fires was relatively small, as their forcings were similar, but of opposite
signs. The net forcing at the surface, however, was large, about 10 W m2 over most
of the tropical Indian Ocean and as low as 150 W m2 over the burning regions in
Indonesia, indicating that aerosols from the fires significantly perturbed the tropical
radiative budget. The calculated forcing of O3 was minor relative to those of BC and OC
aerosols. IND

so tell me again how the CERES radiative budget indicates how warming temperature reduces tropical high cloud densities again?

[Michael Hauber]

One-trick-ponies point over-and-over again to the modern observational record that is dominated by the faux hiatus period from say 1999 to say 2013 to promote low values of climate sensitivity.  Clearly this record is not long enough to get a clear (low noise) climate sensitivity signal that accounts for such factors as the PDO cycle (we have just entered a positive phase of this cycle & thus do not yet have the benefit of data from the full positive phase of this cycle, while the faux hiatus period does include a full negative phase of the PDO cycle), anthropogenic aerosols, ocean heat uptake & ocean thermal inertia, volcanoes, incomplete instrument coverage (particularly in the polar regions as indicated by Cowtan & Way).  This is why since the beginning of this thread I have recommended focusing on improving state-of-the-art ESMs in order to get an appropriately inclusive estimate of climate sensitivity (note that the AR5 Carbon Budget does not use climate sensitivity values based on the CMIP5 projections (with a mean ECS of 3.4C) but rather uses its "process" that is subject to manipulation by one-trick-ponies to reduce this down into ECS values in the 3 to 3.2C range).

The Iris effect does not diagnose climate sensitivity from this time period.  It diagnoses changes in cloudiness that occur with changes in temperature, and then uses this rerlationship to estimate climate sensitivity using a climate model.

Turning to the weather related positive feedback vapor signal identified by Trenberth et al (2015)

Which he diagnosed using the observational record you claim is too short.

[Michael Hauber]

Using CERES radiation data and attempting to correlate it in the tropics is an exercise in frivolity.   Just looking at the regression analysis shows that even if ALL inputs were properly identified and paramaterized there would only be the barest of correlations. 

The correlation was good enough to pass peer review in Nature geosciences.  And Andrew Desler, an expert in radiative feedback and cloud issues reviewed this paper on Realclimate, who considered this paper unproven, but a valuable contribution to the debate (both of which I agree with).

How much do you want to bet that he underestimated the impact of burning peat in Indonesia, a process that we already know puts more aerosols into the environment than other types of fires AND was responsible for 13% to 40% of ALL anthropogenic Carbon Dioxide emissions in the year 1998.



So who is latching onto the results that they like now mike?

http://www.ncbi.nlm.nih.gov/pubmed/12422213
The amount of carbon released from peat and forest fires in Indonesia during 1997
Page et. al. (2002)

Tropical peatlands are one of the largest near-surface reserves of terrestrial organic carbon, and hence their stability has important implications for climate change. In their natural state, lowland tropical peatlands support a luxuriant growth of peat swamp forest overlying peat deposits up to 20 metres thick. Persistent environmental change-in particular, drainage and forest clearing-threatens their stability, and makes them susceptible to fire. This was demonstrated by the occurrence of widespread fires throughout the forested peatlands of Indonesia during the 1997 El Niño event. Here, using satellite images of a 2.5 million hectare study area in Central Kalimantan, Borneo, from before and after the 1997 fires, we calculate that 32% (0.79 Mha) of the area had burned, of which peatland accounted for 91.5% (0.73 Mha). Using ground measurements of the burn depth of peat, we estimate that 0.19-0.23 gigatonnes (Gt) of carbon were released to the atmosphere through peat combustion, with a further 0.05 Gt released from burning of the overlying vegetation. Extrapolating these estimates to Indonesia as a whole, we estimate that between 0.81 and 2.57 Gt of carbon were released to the atmosphere in 1997 as a result of burning peat and vegetation in Indonesia. This is equivalent to 13-40% of the mean annual global carbon emissions from fossil fuels, and contributed greatly to the largest annual increase in atmospheric CO(2) concentration detected since records began in 1957 (ref. 1).

see also:

Indonesian wildfires of 1997: Impact on tropospheric chemistry
Duncan et. al. (2003)
http://onlinelibrary.wiley.com/doi/10.1029/2002JD003195/pdf

The net direct, shortwave radiative forcing at the top of the atmosphere of OC and BC
aerosols from the fires was relatively small, as their forcings were similar, but of opposite
signs. The net forcing at the surface, however, was large, about 10 W m2 over most
of the tropical Indian Ocean and as low as 150 W m2 over the burning regions in
Indonesia, indicating that aerosols from the fires significantly perturbed the tropical
radiative budget. The calculated forcing of O3 was minor relative to those of BC and OC
aerosols. IND

The idea of a correlation is that such factors become back ground noise.  There is only a problem if there is also a correlation between the factors you are analyzing and a factor you have missed out.

so tell me again how the CERES radiative budget indicates how warming temperature reduces tropical high cloud densities again?

If you dont' understand it don't ask me as I don't understand it either.  If you have a valid reason why this should not work (and I note that Andy Desler seems to have no problem with this aspect) then I would be interested in hearing it.

So who is latching onto the results that they like now mike?

I am not latching onto anything.  My viewpoint is that there are both studies showing higher and lower climate sensitivity.  And that most of these studies are generally good science.  It is my view that the IPCC is correct in their estimate of climate sensitivity, and that many of the posters on this thread are cherry picking the papers that support higher sensitivity and dismissing other papers for nonsense reasons.

[jai mitchell]

  It is my view that the IPCC is correct in their estimate of climate sensitivity, and that many of the posters on this thread are cherry picking the papers that support higher sensitivity and dismissing other papers for nonsense reasons.

and when you are shown valid points why the lower sensitivity papers are seriously flawed (as in this case) you claim not to have the scientific discernment to make a determination one way or the other. 

ASLR has shown SIGNIFICANT feedback parameters that are not included in the RCP temperature scenarios.  I have shown you how the carbon cycle feedback parameters have as much variance in emissions as there is difference between the RCP 2.6 and RCP 8.5 emission scenarios.  The entirety of the CMIP5 model datasets rely on Arctic Sea Ice lasting through the summer of 2040.

And for some reason you want to claim that we are not already entering into a regime of massive and catastrophic climate anomalies that are going to wreak devastation to population centers all over the globe.

why would you do that?

Here's a hint.  The droughts of sao paulo, the middle east and california/u.s. southwest are not going away, they will only get worse with time as the hadley cell continues to shift further northward.  The rate of arctic ice loss is going to continue to increase and as china continues to reduce its smokestack pollution we will begin to see rapid temperature rise with associated cumulative impacts on agriculture and extreme weather all over the world.

Within the next 10 years, if we don't engage with a significant portion of our global gross economic output to mitigate and adapt to climate change, if we DON'T do that, then when the time comes that we realize that we MUST do that, it will be far too late for us to do anything about it.

[AbruptSLR]

Turning to the weather related positive feedback vapor signal identified by Trenberth et al (2015)

Which he diagnosed using the observational record you claim is too short.

Trenberth et al 2015 were analyzing vapor signals associated with weather related events, of which there are hundreds of such events per year; thus increasing the significance of their signal; while the climate model used to estimate the influence of a theoretical iris effect cannot correctly evaluate such weather related vapor signals.  Thus once again you are comparing apples to oranges.

[Michael Hauber]

Turning to the weather related positive feedback vapor signal identified by Trenberth et al (2015)

Which he diagnosed using the observational record you claim is too short.

Trenberth et al 2015 were analyzing vapor signals associated with weather related events, of which there are hundreds of such events per year; thus increasing the significance of their signal; while the climate model used to estimate the influence of a theoretical iris effect cannot correctly evaluate such weather related vapor signals.  Thus once again you are comparing apples to oranges.

Water vapor changes are weather and cloud changes are not?

Both Trenberth and the Iris effect correlate changes in radiation with temperature, based on the same CERES dataset.

[Michael Hauber]

and when you are shown valid points why the lower sensitivity papers are seriously flawed (as in this case) you claim not to have the scientific discernment to make a determination one way or the other. 

No serious flaws have been pointed out in the Iris paper (yet)

ASLR has shown SIGNIFICANT feedback parameters that are not included in the RCP temperature scenarios.

No he hasn't.  He has made claims that water vapor feedback is new, which is absolute nonsense.

I have shown you how the carbon cycle feedback parameters have as much variance in emissions as there is difference between the RCP 2.6 and RCP 8.5 emission scenarios. 

If I remember correctly inclusion of methane permafrost carbon feedbacks were predicted to add something like 0.3 degrees to the next century of warming.

The entirety of the CMIP5 model datasets rely on Arctic Sea Ice lasting through the summer of 2040.

They predict this, and while it is possible the sea ice may disappear earlier, its also possible it will last longer.  CMIP5 model data set also includes a reduction in Antarctic sea ice.  And although the current increase in Arctic is something like 5 times bigger, most of the Arctic decrease is included in the models.  The error in the Arctic is only a fraction of the current Arctic loss trend, and the error in the Antarctic is bigger than the current Antarctic increase trend.

And for some reason you want to claim that we are not already entering into a regime of massive and catastrophic climate anomalies that are going to wreak devastation to population centers all over the globe.

why would you do that?

No I haven't. 

Here's a hint.  The droughts of sao paulo, the middle east and california/u.s. southwest are not going away, they will only get worse with time as the hadley cell continues to shift further northward.  The rate of arctic ice loss is going to continue to increase and as china continues to reduce its smokestack pollution we will begin to see rapid temperature rise with associated cumulative impacts on agriculture and extreme weather all over the world.[/quote]

The droughts will go away.  And then come back again.  Its called natural variation.  The drought in California is so extreme that I have no doubt that we will see better years in the future.  But the trend will probably be towards more and worse droughts.  California may never see moisture as high as what was average several decades ago.  Or perhaps the main drought will be somewhere else.  Climate projections seem to show the worst droughts happening around the Mediterranean.  Hadley cell expansion has already reached values expected by the end of the century.  Is this because IPCC drastically underestimated Hadley cell expansion?  Or is the current expansion mostly natural variation and it won't get much worse for the next century?  Or a mix of both?

Within the next 10 years, if we don't engage with a significant portion of our global gross economic output to mitigate and adapt to climate change, if we DON'T do that, then when the time comes that we realize that we MUST do that, it will be far too late for us to do anything about it.

Ten years will make little difference.  Maybe about 0.2 degrees on current trends.  Of course that is not an argument to delay action, otherwise we could keep delaying another 10 years until we have added together enough 10 year periods to get to several degrees of extra warming.

[AbruptSLR]

Turning to the weather related positive feedback vapor signal identified by Trenberth et al (2015)

Which he diagnosed using the observational record you claim is too short.

Trenberth et al 2015 were analyzing vapor signals associated with weather related events, of which there are hundreds of such events per year; thus increasing the significance of their signal; while the climate model used to estimate the influence of a theoretical iris effect cannot correctly evaluate such weather related vapor signals.  Thus once again you are comparing apples to oranges.

Water vapor changes are weather and cloud changes are not?

Both Trenberth and the Iris effect correlate changes in radiation with temperature, based on the same CERES dataset.

vapor changes cause the cloud changes, so both are related weather effects.

[AbruptSLR]

The linked research indicates it will not be until approximately 2040 before natural multi-decadal oscillations even-out the bias introduced to short-term observational based estimates of climate sensitivity by the recent faux hiatus period.  Thus many of the peer reviewed climate sensitivity studies incorporated into the AR5 Carbon Budget likely contain bias that is guiding policy makers to accept unnecessary climate change risks.

England, M. H., J. B. Kajtar, N. Maher (2015), "Robust warming projections despite the recent hiatus", Nature Climate Change, 5, 394-396, doi:10.1038/nclimate2575

http://www.nature.com/nclimate/journal/v5/n5/full/nclimate2575.html

Summary: "The hiatus in warming has led to questions about the reliability of long-term projections, yet here we show they are statistically unchanged when considering only ensemble members that capture the recent hiatus. This demonstrates the robust nature of twenty-first century warming projections."

See also:
http://www.inferse.com/30406/scientists-project-5c-increase-global-warming-emissions-curbed/

[Michael Hauber]

The linked research indicates it will not be until approximately 2040 before natural multi-decadal oscillations even-out the bias introduced to short-term observational based estimates of climate sensitivity by the recent faux hiatus period.  Thus many of the peer reviewed climate sensitivity studies incorporated into the AR5 Carbon Budget likely contain bias that is guiding policy makers to accept unnecessary climate change risks.

England, M. H., J. B. Kajtar, N. Maher (2015), "Robust warming projections despite the recent hiatus", Nature Climate Change, 5, 394-396, doi:10.1038/nclimate2575

http://www.nature.com/nclimate/journal/v5/n5/full/nclimate2575.html

Summary: "The hiatus in warming has led to questions about the reliability of long-term projections, yet here we show they are statistically unchanged when considering only ensemble members that capture the recent hiatus. This demonstrates the robust nature of twenty-first century warming projections."

See also:
http://www.inferse.com/30406/scientists-project-5c-increase-global-warming-emissions-curbed/

As I said already, the estimate of climate sensitivity in Mauritsen et al is not calculated based on observations.  An estimate of the relationship between temperature and cloud properties is calculated based on observations.  The climate sensitivity in Mauritsen et al is calculated by a model and is not influenced by the hiatus period (although Mauritsen et al does note that the climate sensitivity so calculated nicely matches up with observational estimates of climate sensitivity).

And as for the hiatus period - the trend in GISS from 1975 to 1998 is 0.163/year.  The trend from 1975 to now is 0.167/year.  The hiatus period actually caused a slight acceleration in the global warming rate.  The fact that overall warming trends in the complete modern global warming period from 1975 at 0.167/year is lower than the model trend of 0.22 per year cannot be blamed on the hiatus.

Also climate studies since the hiatus period consistently show a similar climate sensitivity to studies performed before the hiatus period started.  Claims that the hiatus period has biased climate scientists assessment of climate sensitivity are nonsense.

[Michael Hauber]

vapor changes cause the cloud changes, so both are related weather effects.

So Mauritsen's analysis of cloud changes to support the IRIS is just as valid as Trenberth's analysis of water vapor changes.

[jai mitchell]

and when you are shown valid points why the lower sensitivity papers are seriously flawed (as in this case) you claim not to have the scientific discernment to make a determination one way or the other. 

No serious flaws have been pointed out in the Iris paper (yet)

ASLR has shown SIGNIFICANT feedback parameters that are not included in the RCP temperature scenarios.

No he hasn't.  He has made claims that water vapor feedback is new, which is absolute nonsense.

I have shown you how the carbon cycle feedback parameters have as much variance in emissions as there is difference between the RCP 2.6 and RCP 8.5 emission scenarios. 

If I remember correctly inclusion of methane permafrost carbon feedbacks were predicted to add something like 0.3 degrees to the next century of warming.

The entirety of the CMIP5 model datasets rely on Arctic Sea Ice lasting through the summer of 2040.

They predict this, and while it is possible the sea ice may disappear earlier, its also possible it will last longer.  CMIP5 model data set also includes a reduction in Antarctic sea ice.  And although the current increase in Arctic is something like 5 times bigger, most of the Arctic decrease is included in the models.  The error in the Arctic is only a fraction of the current Arctic loss trend, and the error in the Antarctic is bigger than the current Antarctic increase trend.

And for some reason you want to claim that we are not already entering into a regime of massive and catastrophic climate anomalies that are going to wreak devastation to population centers all over the globe.

why would you do that?

No I haven't. 

Here's a hint.  The droughts of sao paulo, the middle east and california/u.s. southwest are not going away, they will only get worse with time as the hadley cell continues to shift further northward.  The rate of arctic ice loss is going to continue to increase and as china continues to reduce its smokestack pollution we will begin to see rapid temperature rise with associated cumulative impacts on agriculture and extreme weather all over the world.

The droughts will go away.  And then come back again.  Its called natural variation.  The drought in California is so extreme that I have no doubt that we will see better years in the future.  But the trend will probably be towards more and worse droughts.  California may never see moisture as high as what was average several decades ago.  Or perhaps the main drought will be somewhere else.  Climate projections seem to show the worst droughts happening around the Mediterranean.  Hadley cell expansion has already reached values expected by the end of the century.  Is this because IPCC drastically underestimated Hadley cell expansion?  Or is the current expansion mostly natural variation and it won't get much worse for the next century?  Or a mix of both?

Within the next 10 years, if we don't engage with a significant portion of our global gross economic output to mitigate and adapt to climate change, if we DON'T do that, then when the time comes that we realize that we MUST do that, it will be far too late for us to do anything about it.

Ten years will make little difference.  Maybe about 0.2 degrees on current trends.  Of course that is not an argument to delay action, otherwise we could keep delaying another 10 years until we have added together enough 10 year periods to get to several degrees of extra warming.
[/quote]

*
you don't even understand what I mean by carbon cycle feedbacks, you don't remember what kind of feedback parameters ASLR has shown you and you don't have a clue what I am talking about with regard to waiting 10 years before mitigation actions are taken.

I understand you don't really understand this stuff.

The 10-year comment isn't about how much the earth might warm between now and then, it is about how much more locked-in warming we will secure by the time we make adequate emissions reduction cuts.  The earth operates on a 10-year lag of warming just due to thermal inertia, the water vapor feedbacks associated with today's co2 emissions won't kick in for another 10 years.  Add onto that the negative forcing of anthropogenic aerosols and you find that the water vapor feedback has not even begun for all of the co2 emissions that have been released since about the mid 1990s.

so we have about 2.5 C of additional warming locked in at current atmospheric abundances.

[AbruptSLR]

vapor changes cause the cloud changes, so both are related weather effects.

So Mauritsen's analysis of cloud changes to support the IRIS is just as valid as Trenberth's analysis of water vapor changes.

The behavior in your posts reminds me of the proverbial automobile driver who prefers his half in the middle of the road, no make who else is endangered.

Certainly all researchers (Stevens, Trenberth or otherwise) are entitled to use the CERES dataset as appropriate, but driving down the middle of the road because you say that you are entitled to half of the road is inappropriate.  Trenberth et al (2015) appropriately limit their findings to identification of a vapor signal based on weather driven fluctuations indicating weak positive feedback mechanism (which serves as a lower bound signal as further CERES data in the coming decades may indicate a stronger positive feedback as it gathers data during a positive PDO phase, with reduced Asian aerosol input & with continued strong anthropogenic radiative forcing), which then needs to be re-combined (preferably using a state-of-the-art ESM) with all other feedback mechanisms (both positive & negative) as determined from the full record of paleo and modern data, and physics, in order to estimate climate sensitivity.  Mauritsen & Stevens (2015) take the CERES data and run it through a climate model that filters out weather driven signals [such as Trenberth et al (2015) identified] and then inappropriately derive a biased climate sensitivity.

This bias is one of the primary reasons that the ACME program is developing state-of-the-art hardware and software, so that the fine-scale tropical atmospheric deep convection signal is not filtered out by the model.  With the first three months of 2015 being the warmest first three months on record, we may likely see a much higher climate response for the next few decades; which will further help to calibrate & verify the ACME projections as/when they are reported.

[AbruptSLR]

Claims that the hiatus period has biased climate scientists assessment of climate sensitivity are nonsense.

Likely AR5 values (with a high confidence) for ECS ranged from 1.5 to 4.5C, from which AR5 provided Carbon Budget guidance to policy makers.  Since AR5 the 1.5C values for ECS have been found to be biased (largely due to simplistic misinterpretation of modern instrument observations).  Again, as we are now in a positive PDO phase, China is actively reducing its sulfate aerosol emissions and as there is a high probability that there will be a strong El Nino event this year, modern instrument observations will soon help reduce the uncertainties associated with climate sensitivity estimating that you are using to confuse the true risks that society is facing from climate change, both now and in the future.

Edit: I remind readers that subsequent to the Ringberg workshop (which included Stevens' latest thinking) that Gavin Schmidt believes that the likely range for ECS is 2 to 5C (with a mean of 3.5C) and is not 1.5 to 4.5C (with a mean of 3C).

[crandles]

Ten years will make little difference.  Maybe about 0.2 degrees on current trends.  Of course that is not an argument to delay action, otherwise we could keep delaying another 10 years until we have added together enough 10 year periods to get to several degrees of extra warming.

*
you don't even understand what I mean by carbon cycle feedbacks, you don't remember what kind of feedback parameters ASLR has shown you and you don't have a clue what I am talking about with regard to waiting 10 years before mitigation actions are taken.

I understand you don't really understand this stuff.

The 10-year comment isn't about how much the earth might warm between now and then, it is about how much more locked-in warming we will secure by the time we make adequate emissions reduction cuts.  The earth operates on a 10-year lag of warming just due to thermal inertia, the water vapor feedbacks associated with today's co2 emissions won't kick in for another 10 years.  Add onto that the negative forcing of anthropogenic aerosols and you find that the water vapor feedback has not even begun for all of the co2 emissions that have been released since about the mid 1990s.

so we have about 2.5 C of additional warming locked in at current atmospheric abundances.

This suggests 2.5+.85 = 3.35C (occurred and locked in) warming from 80% of a doubling (CO2e of 485 vs 280) which suggests you believe climate sensitivity is about 3.35/0.8=4.2C. Ten years time will get us to about 85% of a doubling 0.85*4.2C gives total warming (occurred and locked in) of 3.57C

So the extra decade gives total warming that is greater by 0.22C assuming climate sensitivity as is implicit in your figures of 4.2C. Given the uncertainty I suggest that should be rounded to 0.2C. Michael Hauber suggested 0.2C and you complain about him not understanding. Seems more like you just don't want to believe he is right.

[jai mitchell]

This suggests 2.5+.85 = 3.35C (occurred and locked in) warming from 80% of a doubling (CO2e of 485 vs 280) which suggests you believe climate sensitivity is about 3.35/0.8=4.2C. Ten years time will get us to about 85% of a doubling 0.85*4.2C gives total warming (occurred and locked in) of 3.57C

So the extra decade gives total warming that is greater by 0.22C assuming climate sensitivity as is implicit in your figures of 4.2C. Given the uncertainty I suggest that should be rounded to 0.2C. Michael Hauber suggested 0.2C and you complain about him not understanding. Seems more like you just don't want to believe he is right.

The 2.5C value includes carbon cycle and frozen soil feedbacks as well as decreased albedo and decreased DMS production from acidified oceans and deforested land cover.    It is an estimate of what we would experience if we went immediately to zero emissions today.

However, we cannot do that.  So, we have a 40 year window for zero emissions (at the best)  This includes the need for negative emissions tech by 2030.

under any reasonable decarbonization strategy, we are now approaching the limit whereby we have locked in 4+C of warming by 2100 under these strategies. 

this is where we are right now.

If we wait 10 more years before we start to aggressively decarbonize, we will overshoot, by a significant margin.  Sometime around 2065 natural feedback parameters will take over and become a self-reinforcing mechanism, eventually leading to massive clathrate destabilization as the earth approaches 6C sometime around 2100.

to see another statement to this regard, visit here:  http://forum.arctic-sea-ice.net/index.php/topic,874.msg42949.html#msg42949

Crandles,

What your misunderstanding shows is a fundamental difference in the way you and I look at these things.  I look at the entire system at once, the "sticky problem" and how it interrelates.  My understanding is predicated on a higher-end ECS value and the realization that aerosols are underrepresented in the models and we will see < 1000km^2 summer sea ice within the next 10 years, and possibly within the next 3.  With SIGNIFICANT feedback shifts at that time.

You look at ECS as though it represents the actual temperature trend.  it is absolutely not!  This is a common misunderstanding when looking at the simplistic scientific problem of the physics of CO2 emissions.  (it is also how the press reports the issue, another downplaying of the risks of climate change)  However, you must realize now that each Gt of CO2 emitted today is the equivalent of 1.3 Gt due to these feeedback parameters and as we warm beyond cumulative tipping points the single Gt of CO2 will become 2.5 Gt equivalent.

At that point we will find our climate future to be predetermined by the natural environmental response.

capice?

[jai mitchell]

In a similar way, the idea that future emissions will have a larger impact on the overall health of society is backed by the Integrated Assessment Models which, even with a large (grossly large and completely unethical) discount rate, show that the economic impact of GHG emissions on society, called the Social Cost of Carbon grows at a significant rate over the coming decades.

Now, I have looked into these models and I have reviewed some of the most recent revisions, they ALL limit sea level rise below 1 meter and non of them show an arctic ice loss before 2060.  In addition, they do not include multiple feedback parameters like frozen soils and Dymethyl Sulfide loss from ocean acidification.  Indeed, their economic impacts of acidification are non-existent as well.

So, even with these paltry analyses adopted by the current administration (see:  http://www.epa.gov/climatechange/EPAactivities/economics/scc.html )  The damage of emissions in 2050 are over 200% more than the same emissions damage produced in 2015. 

Ultimately, ,the correct way to look at mitigation scenarios have been ultimately laid down, though, to my knowledge only Stanton and Ackerman at Stockholm have done it correctly.  Even so, they SHOULD be using a negative discount rate which would push the damage loss estimate of a single unit of carbon to over 500% more damaging by 2050.

http://frankackerman.com/publications/climatechange/Climate_Risks_Carbon_Prices.pdf

Climate Risks and Carbon Prices:
Revising the Social Cost of Carbon
Ackerman & Stanton (2012)

Abstract The social cost of carbon – or marginal damage caused by an additional ton of
carbon dioxide emissions – has been estimated by a U.S. government working group at
$21/tCO2 in 2010. That calculation, however, omits many of the biggest risks associated with
climate change, and downplays the impact of current emissions on future generations. Our
reanalysis explores the effects of uncertainty about climate sensitivity, the shape of the damage
function, and the discount rate. We show that the social cost of carbon is uncertain across a
broad range, and could be much higher than $21/tCO2. In our case combining high climate
sensitivity, high damages, and a low discount rate, the social cost of carbon could be almost
$900/tCO2 in 2010, rising to $1,500/tCO2 in 2050.  (note this is at 3% discount rate should be negative)

The most ambitious scenarios for eliminating carbon dioxide emissions as rapidly as
technologically feasible (reaching zero or negative net global emissions by the end of this
century) require spending up to $150 to $500 per ton of reductions of carbon dioxide emissions
by 2050. Using a reasonable set of alternative assumptions, therefore, the damages from a ton
of carbon dioxide emissions in 2050 could exceed the cost of reducing emissions at the
maximum technically feasible rate. Once this is the case, the exact value of the social cost of
carbon loses importance: the clear policy prescription is to reduce emissions as rapidly as
possible, and cost-effectiveness analysis offers better insights for climate policy than cost benefit
analysis.

So, when looking at the value of mitigation scenarios, one must look at the AVOIDED DAMAGE  and this is done by considering the emissions that are avoided at the end of the period after the work is done, not at the beginning of the period.  So looking at .2C of warming gained in 2025 doesn't show the impact of 1.5C of warming gained in 2080 on top of the warming that has been experienced to that date.

[Michael Hauber]

  Mauritsen & Stevens (2015) take the CERES data and run it through a climate model that filters out weather driven signals [such as Trenberth et al (2015) identified] and then inappropriately derive a biased climate sensitivity.

They run the CERES data through a linear regression.  They do not run it through a climate model.

And what do you mean a weather driven signal and how is it not included in climate models?  Climate models certainly include 'weather' as I understand it.

What climate models do not include is detailed simulation of clouds.  Trenberth does not address this issue at all (not the purpose of his paper).  Mauritsen references a new model that performs detailed simulation of convection, and finds that this model shows evidence of convective clustering that can contribute to this IRIS effect.