#390, ya, that is telling Wili, Now I look for some shoreline ice forming along the coasts. From that moment the open water will shrink a little faster. Mean time that is not happening, Arctic Ocean simply warms the air immediately above -as ice cools the air above (even with no or the low sun- and forces the refreeze only about where there is sea ice. This guaranties a very slow refreeze.
Lorius´ carsays
Anybody knowledgeable care to comment on Lucia´s last version of how this and that trend is now “falsified”?
Chris at #388–Yes, it would be better to get to DEP 2.6 (or much lower), but we haven’t been following that path so far, and there is scant indication that we will start to any time soon. In any case, again, figure 3 shows that if we stop all emissions now (and yes, Jim, that means completely stop emitting any more CO2, not just stabilize the rate we are emitting at now, unless I’m missing something), with a climate sensitivity of 3 degrees C we will see atmospheric CO2 levels remain at current high levels for centuries.
And that is with including this one aspect of carbon feedback–we know that others are starting or are ‘waiting in the wings’ and they should change the trajectory of that dashed line from flat to an ever rising one (well, not forever, but presumably until all the carbon from accessible sources runs out or a negative forcing overcomes these positive feedbacks.)
I like your adaptations of the daisy world idea at 393. But does yarrow also do a good job of sequestering CO2 with a deep root system as well? Probably you want a mix of flowers and grasses. What you don’t want is bigger shrubs and trees that will lessen the albedo, making for a darker, less reflective surface that warms the immediate vicinity and feeds into the normal snow-loss albedo shift. But that is exactly what is already happening.
at #387 Jim Larsen said, “The work on north-of-Greenland ice coverage hints that we’re not quite as warm as it was in the Arctic”
I’m not quite sure what you meant by this. Could you elucidate?
Patrick 027says
Re 394 Chris Korda
“the economics of energy generation,” – perhaps (mis?)interpreted by some to allow the science of energy generation.
On that note:
heads up: my (P/PH/H)EV discussion ending at 104-105(+106) left some points and loose ends that I would have liked to have tied up/clarify, but anyone interested could probably figure it out anyway. If/when I have my own blog or see some other place it would fit I’ll put it there.
(and very very briefly, Re Chris Dudley 395 – see ‘solar ponds’. According to S2E1 of “How the Universe Works”, Triton’s geysers run on this ‘technology’ – it uses the greenhouse effect. (Then there’s luminescent concentration but no way to discuss that without being ~completely OT now.)
Of course if anyone brought up the non-CO2eq effects of various energy capturing technologies (for reasons other than just saying something good or bad about the technology?), that would be (or at least at times it has been) on topic (or I’ve infered it to have been so…(?):
(the albedo effect of solar power [see my 137,140,145, 219-221, and 223, and also 152,154 (MARodger, Kevin McKinney)] or the mixing/other effects of wind turbines (for example, https://www.realclimate.org/index.php/archives/2011/04/unforced-variations-apr-2011/comment-page-1/#comment-204418 – my 15, 57-58, and also others’ 7, 10, 42, 43, 44, 46, 54, 61 (some of those better than others) – but especially ***72***(author response) and *73* https://www.realclimate.org/index.php/archives/2011/04/unforced-variations-apr-2011/comment-page-2/#comment-204581 ); at times in the past the issue of climate change’s effects on energy resources has also been brought up,
(although that could degrade into a n_ vs. etc.).
ReCAPTCHA has anticipated what I was going to post later? luni-solar …
wilisays
Sorry to be such a pest, but I just found a great, short video of Steven Chu explaining the permafrost carbon feedback tipping point a while back:
My basic question is: Am I right in interpreting graph 3 of the Nature Geoscience article to mean that we have now crossed the tipping point described so clearly by Chu?
If I am right, why I do I seem to be the only one getting excited and concerned about it here? If I’m not right, please someone explain clearly why I’m not–what I’m missing, or what the authors of the article are missing?
Patrick 027says
‘solar ponds’ … actually (to a great extent?*) the Earth’s atmosphere ‘runs’ on that technology.
*because if there were no greenhouse effect there’d still be latitudinal heating gradients. But without radiational cooling in the atmosphere, I’d guess overturning in general would be at least somewhat inhibited.
I’ve been chipping away at the two questions I posed back at @289: if we were to realize the EIA’s IEO2011 scenario (equivalent to following RCP8.5 out to 2035), what would atmospheric CO2 be in 2035, and what average global temperature would likely result? Gavin pointed out that I need “to take into account the fraction of the emissions taken up by land and ocean very quickly (about 50%)”, so I made a new spreadsheet that does so. I started with the RCP8.5 Fossil and Industrial Emissions data in GtC/Yr. I multiplied each sample by 0.61 (about 50%, more on this below), divided by 2.12 (the conversion from Gt/C to ppm CO2), and plotted the running sum of the samples. Here’s the result.
While I was working this out, I discovered that the AR5 RCP scenario data download includes not only emissions and forcing data but also concentrations data. Duh! But that’s OK because the main point of the exercise was to learn a bit more about climate science. So I made another chart that plots my estimate of CO2 concentrations against the RCP8.5 concentrations data. I tried a few different values for Gavin’s “about 50%” and got the best fit at 61%. According to my estimate CO2 concentration would be 472 ppm by 2035, but RCP8.5 puts it a bit lower at 467 ppm.
That still leaves the question, how much would average global temperature increase as a result? So here’s my crass first approximation. According to WP, “The climate sensitivity specifically due to CO2 is often expressed as the temperature change in °C associated with a doubling of the concentration of carbon dioxide in Earth’s atmosphere”, and the consensus estimate of that sensitivity is ~3ºC. In other words doubling the pre-industrial 280 ppm should cause an increase of ~3ºC. 467 ppm is only 67% of a doubling, so we want to prorate the 3ºC, presumably using a log function, hence:
2 ^ 0.67 = 1.59
1.59 / 2 * 3ºC = 2.4ºC
So I estimate that if we followed IEO2011/RCP8.5 out to 2035, and then stabilized our forcing, we would eventually arrive at an average global temperature increase of 2.4ºC. Am I even close? I haven’t forgotten Gavin’s advice “that I have to account for the thermal inertia of the oceans”, I’m just not ready to deal with that yet. In case anyone wants my spreadsheet it’s here.
Jim Larsensays
403 wili, I was referring to the study which concluded that the Arctic Ocean used to have less ice than today. It used driftwood on Greenland’s northern shore as primary data.
“During the Holocene Climatic Optimum of 8,000 to 5,000 years ago, the Arctic sea ice was less than 50% (so less than 2.6 mln sq km) of the lowest extent on satellite record, the 2007 melting record, … during the HCO or HTM (Holocene Thermal Maximum) it was warmer than today – in the Arctic on average about 1.6 degrees Celsius.”
I was curious as to reactions to something I just stumbled across, which is skeptics using a “study” that cites a revision of standards for ground station siting by Michel Leroy of METEO France. How this really changes things when it comes to the validity of temperature records is never made clear and in addition the folks at WUWT who are trying to push this meme seem to me to be trying to confuse the issue by making references to Leroy 1999 and Leroy 2010 as though these were peer reviewed papers, which I can’t find any evidence of.
All of the silly journalism spin in the article aside, it would be nice if the RC folks could do a short post on this to put this in better context. My understanding from some of the climate model simulations was that 10 year “pauses” were fairly normal, but 15+ year pauses were quite rare in climate model simulations of GHG forcing…
Just curious. It’d be nice to know the broader context, as you can bet this will come up in many a Q&A on climate change talks and I would love to have a solid answer for it.
[Response: The funny thing is that the trend in HadCRUT4 from Jan 1997 to Aug 2012 is positive (0.047+/-0.038 deg C/decade – 95% CI, no adjustment for auto-correlation). See The Escalator for more. – gavin]
“… The dataset, from an unnamed UK submarine mission, is set to provide a snapshot of conditions under the ice and is said to be one of the few clues available for the last two decades on the changes taking place in the Arctic.
To process the information, the DSTL will work with the Natural Environment Research Council and the UK Hydrographic Office, which is based in Taunton, to prepare the data for researchers.
The information gathered will be handed over to academics at National Oceanography Centre, where researcher John Allen said it would provide clues on the impact of climate change in the Arctic….”
Patrick 027says
re 407 Hank Roberts – true, but I don’t think that was an issue in this case (we could all read his comment and understand how it applies to climate sensitivity; I do not think he was suggesting net positive feedback – except for Planck response (negative) – couldn’t exist without runaway, which is the usual problem we have with these differing definitions).
[second third try at posting; never got “could not open socket” before]
Steve Fishsays
Re- Comment by Patrick 027 — 14 Oct 2012 @ 12:53 PM:
You said- “[second third try at posting; never got “could not open socket” before]”
So, you are saying that this was not a wrenching or shocking experience? Steve
Patrick 027says
Re 405 wili – you may have mentioned this already but it’s discussed here http://www.skepticalscience.com/Macdougall.html – from fig 2 (which was a little hard to read without buying/etc.) it looks like permafrost C has already been set to release but not completely. It isn’t a single-switch, total release situation.
#407 “Engineers and musicians define “feedback” for their work. Climatology papers define “feedback” differently. Same word, different definition.”
The term feedback comes from the mathematical description of systems called system theory and in any case except probably musicians means pretty much the same:
I’ve studied control theory and you get to learn a lot about system theory there.
The term “acoustic feedback” http://en.wikipedia.org/wiki/Audio_feedback means something else, for that reason I took care to write “feedback” in the sense of system theory or “acoustic feedback” where I meant what musicians might name a “feedback”, because they are not much interested in feedbacks as long as the system stays stable.
Maybe you should read the target paper. An equilibrium sensitivity of 6 C per doubling is suggested there and this feedback would be only part of that slow response. Fortunately, while RC wants to keep off the topic that explores “approaches to climate change mitigation.” The IPCC is taking that on as a part of climate science. So, DEP 2.6 looks a lot like Hansen at al.’s recommendation for a concentration target and approach to it. And, the new paper makes clear that the feasibility of that does not seem to be drastically changed by their findings. So, perhaps the new paper needs the words “Don’t Panic” written in large friendly letters on the cover.
Re 416 Bernd Herd – in climate science, for global climate change, specifically a global (average surface) temperature change in response to a global (typically average net tropopause-level after stratospheric adjustment) radiative forcing (or other heat source – although on Earth those tend not to be so big), where the radiative forcing may be in units of W/m^2, so that equilibrium climate sensitivity is in K*m^2/W (it is often expressed as K/doubling CO2 as doubling CO2 has a certain amount of radiative forcing for given conditions). The feedback can be expressed as W/(K*m^2), a radiative feedback per unit temperature change, and in this form they add linearly. This includes the Planck response, which is just the increase in OLR (outgoing longwave radiation) in response to temperature according to the Planck function and the given optical properties. The Planck response is a negative feedback; including it, the total feedback is -(1/equilibrium climate sensitivity) and must be negative in order for equilibrium climate sensitivity to be finite. However, the Planck response is so fundamental that the feedback often refers to the other feedbacks, in which case the net feedback can be positive and the climate sensitivity, though it will be larger, is still finite (climate is stable). Also, the ratio of climate sensitivity to that with only a planck response may be considered.
The impression I’ve gotten is that some people, not knowing that ‘net positive feedback’ may exclude the Planck response, think that this must imply the climate is unstable – the funny thing is, this will be used to argue for a lower climate sensitivity, but one could see that something is wrong here because the higher climate sensitivity caused by the positive feedback is still finite.
To Patrick @ #415–Yes, I started with that useful Skeptical Science article (and yes, I did post a link to it above.) You write: “it looks like permafrost C has already been set to release but not completely. It isn’t a single-switch, total release situation.” I’d be curious to know what exactly in the article leads you to this conclusion. I do realize that they are not talking about all the CO2 coming out of the permafrost at once. I am concerned that we may already be committed to the eventual release of all the permafrost carbon.
Chris, I did read the original article, as might have been clear from the fact that I quoted from the middle of it. We seem to be getting different messages from it. Thanks for the link to the Hansen article, too.
Does anyone else reading the article–looking at the flat dashed line in figure three and putting that together with the fact that we know there will be other carbon feedbacks–come to my conclusion that this means we are now in a kind of runaway (not the Venusian kind, though)? If so, how long have we already been in it, and how steep is the slant of inevitable atmospheric CO2? If not, why not (as clearly and specifically as possible, if you would)?
Thanks for the responses and for the interesting conversation about different meanings of ‘feedback.’
I think my last post @408 didn’t have the math quite right, sorry! To calculate the change in average global surface temperature that would result from a given atmospheric CO2 concentration, assuming a given climate sensitivity, the function should be:
This assumes we’re interested in temperature change relative to the pre-industrial CO2 concentration of 280 ppm though that’s arbitrary of course. So for example if sensitivity is 3ºC the results are as follows:
Assuming the above makes sense, my next question is, what about the timing? My simplified model just says that if atmospheric CO2 reaches 467 ppm in 2035, and magically stabilizes there, temperature would eventually reach 2.21ºC. It doesn’t take into account the thermal inertia of the ocean and probably lots of other interesting details.
SecularAnimistsays
How often people struggle with the fact that words have quite different meanings in different contexts.
To me, “feedback” will always intuitively mean Jorma Kaukonen’s guitar at the beginning of “The Ballad of You and Me and Pooneil”.
Brian Dodgesays
@ Chris Dudley — 10 Oct 2012 @ 1:13 PM re Munich Re
“Atmospheric scientist Clifford Mass of the University of Washington also has a problem with Munich Re’s findings, saying that once the data are adjusted for population there is no recent upward trend…”
current US population 314.58e6 Munich Re reports recent losses 36e9; 1980 losses 9e9. Therefore 1980 population must have been 78.64e6, not the 203.18e6 that everybody thinks. Who woulda thunk the evil cabal of climate scientists could manipulate census data as well as the temperature record?
Pielke has a more defensible argument – “”Thirty years is not an appropriate length of time for a climate analysis, much less finding causal factors like climate change,” – and he’s bright enough to cherry pick data sets with a lot of noise and statistically infrequent occurrences that do require more than 30 years (look! here’s a squirrel!) to be statistically significant, and conflate that with all climate data sets. How many years are required to show statistical significance in the decline of Arctic sea ice summer minima, or accelerating glacial mass loss?
@ Lorius´ car — 13 Oct 2012 @ 3:41 PM re Lucia’s public mathturbation of model vs weather
Lucia says
“If we apply test whether the observation the trend associated with Global Mean Temperature computed starting in Jan 2000, we reject the ‘null’ hypothesis that the observation falls within the spread of “weather” characteristic of a particular model in (2,5,4) cases based on comparisons to (GISS, HadCRUT3 and NOAA) respectively.”
Will Roger Pielke show up to dismiss Lucia’s work, and by implication all climate “skeptics” because they are trying to make something out of meaningless short term noise, or does he think that Munich Re’s 30 years isn’t enough, but Lucia’s 12 years is just fine? Remember the kerfuffle over Phil Jones’ “no significant warming since 1995”?
What would Lucia see if she ran her analyses of models versus every possible 12 year span of observations, instead of just the last 12?
@ BA — 14 Oct 2012 @ 11:15 AM regarding trends (Speaking of which, Is it just my imagination, is it just my imagination, or is there a new trend from the denialoshpere to muddy the waters by misuse & misrepresentation of trends?)
I was writing too fast. By “target paper” I meant the Hansen et al. (2008) paper “Target atmospheric CO2: Where should humanity aim?” that I linked. I know you’ve read MacDougall et al. (2012). My point was that the new work has been anticipated in its basic points in the emissions trajectory proposed in the 2008 paper.
I’ve been looking at the WG I reference document for AR5 and have found this nice concise list of topics that I think should be considered on topic of RC unforced variations discussion. This does entail including scenarios as on topic, something Gavin wanted off topic. They are drawn in because they are tied to representative concentration pathways (RCPs), the basis for this chapter. RCP 2.6 is of particular interest because it includes reversibility through mitigation efforts, somewhat of a departure from AR 4.
Chapter 12: Long-term Climate Change: Projections, Commitments and Irreversibility
Executive Summary
• Scenario description
• Projections for the 21st
century
• Projections beyond the 21st
century
• Regional climate change, variability and extremes
• Forcing, response and climate sensitivity
• Climate change commitment and inertia
• Potential for abrupt change and irreversibility in the climate system
• Quantification of the range of climate change projections
Re #419 Patrick 027: Climate Science is just an application of system theory. For that reason they separate between forcings and feedbacks. Forcings do not depend from the actual temperature, feedbacks do. For that reason, CO2 from fossile fuels is not a feedback, but a forcing.
In the microphone-amplifier-speaker analogy, this means the “forcing” is comparable to the guitar sound that you wanted to amplify.
The Permafrost Carbon Feedback PCF is a feedback, and not a forcing, because it depends on the temperature already reached. And until now I can’t see any difference between a “self-sustained” PCF and an unstable system for a short-time analysis. In a long-time analysis the unlinearity of the system will be too important to allow a linear approximation. I wouldn’t know how to apply a Bode Diagram here.
In sytem theory the planck response is just a negative feedback and for short time analysis can be approximated as nearly linear with some factor. If the sum of all positive and negative feedbacks becomes > 1, then the system is unstable. I know that this is only an approximation, for the system is non-linear. However I can’t see what aspect would contradict the idea that one could probably define a maximum CO2 climate sensitivity by appplying the PCF model to past temperatures, except maybe if the climate sensitivity itself would be non-linear?
#422 wili: “Does anyone else reading the article–looking at the flat dashed line in figure three and putting that together with the fact that we know there will be other carbon feedbacks–come to my conclusion that this means we are now in a kind of runaway (not the Venusian kind, though)? If so, how long have we already been in it, and how steep is the slant of inevitable atmospheric CO2? If not, why not (as clearly and specifically as possible, if you would)?”
The authors of the article show, that the answer to this question depends on the CO2 climate sensitivity. 3°C and more means that we already triggered that runaway effect, less than 3°C means it has not happened yet.
The best estimation from the 2007 IPCC report is 3°C, so we’ve got a 50% chance of not beeing doomed to this additional CO2 release to the atmosphere.
I mostly wonder, if the effect was obviously not triggered a long time ago, and it has been triggered now with 0.8°C warmer earth at 3.0°C climate sensitivity, if we continue to emit CO2, won’t 2.0°C climate sensitivity become sufficient if we continue CO2 emissions for some decades? And the 2007 IPCC report says a climate sensitivity below 2.0°C is very unlikely.
And obviously stopping CO2 emmissions immediatly is also very unlikely.
“If so, how long have we already been in it”? I guess since about 1900, for our actions, even our mere existance, is part of it. We cannot return into the state of mankind we had before 1900 without most of us dying for starvation.
James Hansen changed his mind in about 2004 and now states that the atmosphere must not remain beyond 350ppm CO2 for a long time and calculated that there are still chances of reaching that goal:
As part of his scenario he suggests to take away a part of the CO2 by intensive reforestation.
So according to the Permafrost Carbon Feedback article our actions are still part of the runaway scenario, we could still change our actions. But this might change in the future. The time remaining for actions might be short, even if the full consequences might take centuries to develop. But if there are additional feedbacks coming in, the time might not even be several centuries, see http://www.ameg.me/ . I can only hope that they are wrong.
Runaway is possible but it occurs at 10-25 W/m^2 higher or lower forcing than today. The supplementary materiel in this paper http://pubs.giss.nasa.gov/abs/ha00410c.html particularly surrounding fig. S3. provides a brief discussion. It should be noted that raypierre objects to the high end argument presented there and elsewhere.
World grain reserves are so dangerously low that severe weather in the United States or other food-exporting countries could trigger a major hunger crisis next year, the United Nations has warned.
Failing harvests in the US, Ukraine and other countries this year have eroded reserves to their lowest level since 1974. The US, which has experienced record heatwaves and droughts in 2012, now holds in reserve a historically low 6.5% of the maize that it expects to consume in the next year, says the UN.
“We’ve not been producing as much as we are consuming. That is why stocks are being run down. Supplies are now very tight across the world and reserves are at a very low level, leaving no room for unexpected events next year,” said Abdolreza Abbassian, a senior economist with the UN Food and Agriculture Organisation (FAO).
[…]
The figures come as one of the world’s leading environmentalists issued a warning that the global food supply system could collapse at any point, leaving hundreds of millions more people hungry, sparking widespread riots and bringing down governments. In a shocking new assessment of the prospects of meeting food needs, Lester Brown, president of the Earth Policy research centre in Washington, says that the climate is no longer reliable and the demands for food are growing so fast that a breakdown is inevitable, unless urgent action is taken.
I’m not sure that “unexpected events” is the right term anymore, given that we have every reason to expect widespread, severe, prolonged drought next year, and every year for the foreseeable future.
Predictions that AGW could cause agriculture to collapse world-wide by mid-century, once considered “alarmist”, may — like many other “alarmist” predictions — prove to have been optimistic.
Ric Merrittsays
Last word from me for now on this… I have attempted to recommend Tom Murphy’s blog Do The Math (possibly OT, but with the excuse that I am trying to point out one good venue for energy discussions), with a few responses here, mainly unreasonable, defamatory to Tom, and at a far lower level of thoughtfulness than Murphy’s blog itself. For the rest of you with possibly more open minds, give it a try, starting from the beginning. The posts make sense in order, and you can skim the ones of lesser interest to you. You will notice a certain open-endedness, which arises from the topic itself, in which much is unsettled.
Hint: if you really really want something, that doesn’t necessarily make a sentence starting with “I need [something]” more plausible. Applies very well to energy technologies.
Ric, kibitzers show up here (as everywhere online) making seemingly authoritative pronouncements without credentials or publicly known name or reputation. The regular readers here learn to check whether someone has anything behind their opinion.
SecularAnimistsays
Ric Merritt wrote: “I have attempted to recommend Tom Murphy’s blog Do The Math …”
I did peruse Tom Murphy’s blog. My comment about it here mentioned only his impressively detailed analysis of his own, equally impressive do-it-yourself home PV system — but by no means was that the only thing about it that I found valuable. As you (I think) mentioned earlier, his general discussions about energy consumption are, I think, very intelligent and important. I’ll be going back to read more, and I’m happy to second your recommendation.
Ric, the alternative energy system on his blog that some people are swooning over was worked out over thirty years ago by sailboaters and island dwellers. It’s great, but it won’t get you off the grid if you are still running compressors in a conventional home (or if you are already off it before you started building the system as most people are) and you’d have to scale it up immensely to satisfy the energy hunger of suburbia. I can only speak for myself but I’ve moved on, several decades ago actually. This is the third time you’ve recommended his blog here and the third time I’ve had to remind you that there is very little math there (I think I saw one post there using thermodynamic quantities) and he more or less uses it to push an obsolete worldview on people who don’t have the mathematical skills to challenge his beliefs. Our human problem has become so severe through extreme neglect and the unwillingness to engage in confrontational behavior that it’s more or less now going to take two dimensional an carbon based quantum simulators using a Manhattan style project and Apollo style national effort in reusable launch vehicles to even come close to solving it in the timeframes that will make any difference. Unfortunately in this country there are rabid Christian fundamentalists sitting on YOUR congressional and senate science and technology committees.
I know that offends you. That is my intent. I’m just getting the job done.
Steve Fishsays
Re- Comment by Ric Merritt — 15 Oct 2012 @ 11:47 AM:
On your recommendation I read quite a bit of Murphy’s blog. I enjoyed it. I passed it on.
Thomas Lee Elifritz wrote: “you’d have to scale it up immensely to satisfy the energy hunger of suburbia”
You know, the idea that the problem we need to solve with regard to phasing out fossil fuels is to find other ways to “satisfy the energy hunger of suburbia” has got to go. I think that’s one of the points that Tom Murphy makes on his blog.
A very tiny percentage of human beings have “enjoyed” that profligately wasteful, inefficient and downright stupid level of energy consumption for a tiny fraction of human history.
If saving the world means that they need to get their fat bottoms out of their SUVs and walk a bit, and perhaps read some books in modest but cozy homes instead of gazing at the giant plasma TV screens in each and every room of their McMansions, well, it’s not the end of the world.
I’m not dismissing Tom Murphy’s ‘work’, Hank, I’m dismissing his ‘blog’ as being relevant to the scale of the problem. For education, it’s just fine, but for actual solutions, I can recommend the peer reviewed literature. Educating the lay public about some simple arithmetical details of the radiation imbalance is not going to solve the problem created by the radiation imbalance, since the scale of the problem now exceeds even the most modest approaches to its solution. It will now require ‘big science’, bigger than anything heretofore accomplished including the bomb and the Apollo program.
In particular, since recommendations are being made, I can recommend this as indicative of the types of condensed matter physics breakthroughs necessary to solve a problem that I in particular have now known to exist for several decades now.
SecularAnimistsays
Hank, with regard to your fist link to Murphy’s blog — “Recipe For Climate Change” — unfortunately, I have to say that his introduction shows that he really doesn’t get it when it comes to global warming:
“I view climate change as a genuine challenge to the stability of our coexistence with the planet. But it is not my primary concern. A far more dangerous threat to the human endeavor is, in my mind, our reliance on finite resources and the difficulty our economic systems will have coping with a decline in the availability of cheap energy.”
Um, no.
A “decline in the availability of cheap energy” — i.e. peak oil, and more generally peak fossil fuels, could — if we handle it very stupidly — cause some very serious economic and social disruptions to human society.
But it won’t melt the polar ice caps, and kill the forests, and turn the world’s most productive croplands to deserts, and acidify the oceans, and cause the mass extinction of most life on Earth. Unmitigated global warming could easily do all of those things.
Chris Dudley @426: Re 2011 Hansen et al, there’s enough material there for three papers! And it ends disappointingly with a whimper. But never mind, my take-away is that they’re asserting a three-phase approximation of climate response as follows:
40% after 5 years (the “fast” response)
75% after 100 years (the “slow” response: as opposed to 60% currently used by most models)
and 100% after a millennium (the “recalcitrant” remainder)
Would you agree with this summary? I’m working on a numerical model that emulates it. Input will be a CO2 concentrations time series, e.g. from an RCP scenario, and output will be a temperature change time series. Presumably the output will look very different from this: Temperature increase from RCP8.5 CO2 concentrations (instantaneous climate response), which is just a straightforward application of the “naive” calculation I introduced at @423, with sensitivity = 3.
Patrick 027says
Re 434 Ric Merritt – I like it (Tom Murphy’s blog). (When reading through the comments I saw this mentioned alongside ~’Mott electronic lattice frustration’ so initially I expected some quantum physics, but that was just a mix-up. I agree there’s math there.)
Re 422 wili – I was looking at figure 2 (as best I could in the little version you get from behind paywall) – it looks like, for the DEP 4.5 emissions ((DEP refers to forcing (from anthropogenic emissions, I think) W/m^2 in 2100) a bit more than doubling CO2 by 2100, setting aside other GHGs), if sensitivity is 3 K/doubling, the permafrost reservoir declines but starts to level off significantly before reaching 0 (I believe that’s 0 % of the permafrost reservoir?). For the higher sensitivity of 4.5 K/doubling, the decline slows before reaching 0 but still looks like it’s approaching 0 – this is similar to the DEP 8.5 at 2 K/doubling sensitivity; the higher sensitivies at DEP 8.5 lead to more of a quasi/pseudo-‘hard landing’ for permafrost C (rapid approach to 0 and only ‘slowing down at the last minute’). Also, from http://www.skepticalscience.com/Macdougall.html, under “Counter-intuitive results“,
…
the amount of permafrost carbon released on the most pessimistic pathways is larger (39, 58, 67 and 101 ppm CO2 respectively for the four DEP’s), and occurs sooner.
…
Also counter intuitively, the uncertainty of the permafrost feedback is reduced in the higher emission scenarios. In these scenarios, there is less uncertainty that we will unleash all of the permafrost, and quickly.
…
So it should become more likely that some permafrost C remains indefinitely, as well as more for any given short time period, if there is less forcing.
And, even after dropping aerosol cooling, we still have to add CO2 (or other GHGs) to the atmosphere to complete a DEP 4.5 scenario (setting aside perturbation time (of CH4, for example), it occurs to me that it is best to have it all as CO2 as this would reduce the radiative impact of the permafrost CO2. On the other hand, anthro-CH4 would partly reduce the impact of feedback CH4 (how much, I have no idea) … oh well).
On the other hand, that’s assuming all permafrost C is emitted as CO2. So our room to avoid permafrost runaway will be smaller, but I couldn’t say by how much.
Re 430-431 Bernd Herd – I’m comfortable with the guitar-microphone-amplifier analogy.
There is a concept called ‘Charney sensitivity’, which generally includes feedbacks that act fast (faster than the climate can equilibrate to any forcing) (and perhaps it might be said, are more obvious and easy to understand, generally abiotic?)… I think it includes H2O vapor, clouds, seasonal snow and sea ice (I’ve been over this before but I always find myself questioning whether it does include those last two or not; I’d expect it does). I don’t think it includes vegetation albedo or aerosol feedback; it definitely does not include biogeochemical feedbacks that could add CO2 or CH4 to the atmosphere; it also exludes ice sheet albedo feedback, which is generally slower than the climate response time. There is something called ‘Earth system sensitivity’ –
see: http://www.skepticalscience.com/hansen-and-sato-2012-climate-sensitivity.html
… to be cont.
flxiblesays
Odd how so many here go on about energy and CO2 when in fact our problem, as Tom ‘Do the Math’ really points out, is the unsustainable nature of human impact on the planets resources …. ultimately meaning the sheer numbers of consumers and would-be consumers as much as their level of consumption. I think he’s right to be concerned with the impact of our over-consumption of all resources, including, but not at all limited to, fossil fuels. Our economic and social systems are already showing the strain of the “techno-fix” attitude expressed by some here regarding planetary limits.
The arctic will not be planted with Yarrow to improve its albedo in anyones lifetime, especially not the arctic ocean. Drylands and deserts will not be planted to trees to draw down carbon when ever decreasing water supplies are needed to grow our food. The “smart grid” won’t smarten up as long as there’s cheap coal to burn. Coal and petroleum won’t get too expensive to use as long as the money derived from them elects your governments.
SA@433 points to the warning of food production problems [link], with the shortage of stockpiles said to be the lowest since 1974 – when there was “only” 4 billion of us on the planet. Yes, “breakdown is inevitable, unless urgent action is taken”, but the only urgent action likely to change things is a drastic reduction in population, which the planet may well be about to implement for us.
Patrick 027says
Correction?
– re my re wili 422 – from the skeptical science post: “Note that a self-sustaining feedback is not the same thing as a runaway greenhouse effect.”
– so it may be that the threshold forcing for releasing all permafrost C is not a threshold for permafrost C runaway but simply the point at which the source of the feedback has been exhausted. Thus our room to avoid ‘runaway’ that I stated earlier would then be the room we have to keep some nonzero C amount in the permafrost. Running out of permafrost C would then be like running out of surface water to feed the water vapor feedback, of the ocean were sufficiently shallow (to stay out of H2O-runaway territory).
That sounds like one of the things they tried. I noticed when I implemented their Green’s function approach to a sudden end to emissions, that the temperature began to fall as soon as emissions dropped while the forcing should still have been causing the temperature to increase. I also tried to implement their function as a lag that finishes quick for small changes in forcing but drags for larger changes, but the functional form made that delay a long time to get any temperature rise at all with a BAU type emissions profile. I think we can say that the response function represents the response to a step function doubling in concentration but working backwards from that to a response to a different forcing profile (other than high frequency volcanic forcing it has also been tuned to) may not be so easy.
But it may also be the best tool available so far to do approximations without full model runs.
The article is a little ambiguous, but when they give units is is in days of consumption. Might it not be that population growth and improved nutrition has been factored into the statement about 1974?
And, wasn’t 1974 just after the Soviet crop failure? Not too surprising if carryover stocks were low then as now.
#390, ya, that is telling Wili, Now I look for some shoreline ice forming along the coasts. From that moment the open water will shrink a little faster. Mean time that is not happening, Arctic Ocean simply warms the air immediately above -as ice cools the air above (even with no or the low sun- and forces the refreeze only about where there is sea ice. This guaranties a very slow refreeze.
Anybody knowledgeable care to comment on Lucia´s last version of how this and that trend is now “falsified”?
http://rankexploits.com/musings/2012/observations-v-models-model-weather/
Is this something one should pay attention to?
Chris at #388–Yes, it would be better to get to DEP 2.6 (or much lower), but we haven’t been following that path so far, and there is scant indication that we will start to any time soon. In any case, again, figure 3 shows that if we stop all emissions now (and yes, Jim, that means completely stop emitting any more CO2, not just stabilize the rate we are emitting at now, unless I’m missing something), with a climate sensitivity of 3 degrees C we will see atmospheric CO2 levels remain at current high levels for centuries.
And that is with including this one aspect of carbon feedback–we know that others are starting or are ‘waiting in the wings’ and they should change the trajectory of that dashed line from flat to an ever rising one (well, not forever, but presumably until all the carbon from accessible sources runs out or a negative forcing overcomes these positive feedbacks.)
I like your adaptations of the daisy world idea at 393. But does yarrow also do a good job of sequestering CO2 with a deep root system as well? Probably you want a mix of flowers and grasses. What you don’t want is bigger shrubs and trees that will lessen the albedo, making for a darker, less reflective surface that warms the immediate vicinity and feeds into the normal snow-loss albedo shift. But that is exactly what is already happening.
at #387 Jim Larsen said, “The work on north-of-Greenland ice coverage hints that we’re not quite as warm as it was in the Arctic”
I’m not quite sure what you meant by this. Could you elucidate?
Re 394 Chris Korda
“the economics of energy generation,” – perhaps (mis?)interpreted by some to allow the science of energy generation.
On that note:
heads up: my (P/PH/H)EV discussion ending at 104-105(+106) left some points and loose ends that I would have liked to have tied up/clarify, but anyone interested could probably figure it out anyway. If/when I have my own blog or see some other place it would fit I’ll put it there.
(and very very briefly, Re Chris Dudley 395 – see ‘solar ponds’. According to S2E1 of “How the Universe Works”, Triton’s geysers run on this ‘technology’ – it uses the greenhouse effect. (Then there’s luminescent concentration but no way to discuss that without being ~completely OT now.)
Of course if anyone brought up the non-CO2eq effects of various energy capturing technologies (for reasons other than just saying something good or bad about the technology?), that would be (or at least at times it has been) on topic (or I’ve infered it to have been so…(?):
(the albedo effect of solar power [see my 137,140,145, 219-221, and 223, and also 152,154 (MARodger, Kevin McKinney)] or the mixing/other effects of wind turbines (for example, https://www.realclimate.org/index.php/archives/2011/04/unforced-variations-apr-2011/comment-page-1/#comment-204418 – my 15, 57-58, and also others’ 7, 10, 42, 43, 44, 46, 54, 61 (some of those better than others) – but especially ***72***(author response) and *73*
https://www.realclimate.org/index.php/archives/2011/04/unforced-variations-apr-2011/comment-page-2/#comment-204581 ); at times in the past the issue of climate change’s effects on energy resources has also been brought up,
(although that could degrade into a n_ vs. etc.).
ReCAPTCHA has anticipated what I was going to post later? luni-solar …
Sorry to be such a pest, but I just found a great, short video of Steven Chu explaining the permafrost carbon feedback tipping point a while back:
http://www.youtube.com/watch?v=oHqKxWvcBdg
My basic question is: Am I right in interpreting graph 3 of the Nature Geoscience article to mean that we have now crossed the tipping point described so clearly by Chu?
http://www.nature.com/ngeo/journal/v5/n10/full/ngeo1573.html
If I am right, why I do I seem to be the only one getting excited and concerned about it here? If I’m not right, please someone explain clearly why I’m not–what I’m missing, or what the authors of the article are missing?
‘solar ponds’ … actually (to a great extent?*) the Earth’s atmosphere ‘runs’ on that technology.
*because if there were no greenhouse effect there’d still be latitudinal heating gradients. But without radiational cooling in the atmosphere, I’d guess overturning in general would be at least somewhat inhibited.
Bernd Herd says: “….In the microphone-amplifier-speaker correspondence …”
Engineers and musicians define “feedback” for their work.
Climatology papers define “feedback” differently.
Same word, different definition.
I’ve been chipping away at the two questions I posed back at @289: if we were to realize the EIA’s IEO2011 scenario (equivalent to following RCP8.5 out to 2035), what would atmospheric CO2 be in 2035, and what average global temperature would likely result? Gavin pointed out that I need “to take into account the fraction of the emissions taken up by land and ocean very quickly (about 50%)”, so I made a new spreadsheet that does so. I started with the RCP8.5 Fossil and Industrial Emissions data in GtC/Yr. I multiplied each sample by 0.61 (about 50%, more on this below), divided by 2.12 (the conversion from Gt/C to ppm CO2), and plotted the running sum of the samples. Here’s the result.
While I was working this out, I discovered that the AR5 RCP scenario data download includes not only emissions and forcing data but also concentrations data. Duh! But that’s OK because the main point of the exercise was to learn a bit more about climate science. So I made another chart that plots my estimate of CO2 concentrations against the RCP8.5 concentrations data. I tried a few different values for Gavin’s “about 50%” and got the best fit at 61%. According to my estimate CO2 concentration would be 472 ppm by 2035, but RCP8.5 puts it a bit lower at 467 ppm.
That still leaves the question, how much would average global temperature increase as a result? So here’s my crass first approximation. According to WP, “The climate sensitivity specifically due to CO2 is often expressed as the temperature change in °C associated with a doubling of the concentration of carbon dioxide in Earth’s atmosphere”, and the consensus estimate of that sensitivity is ~3ºC. In other words doubling the pre-industrial 280 ppm should cause an increase of ~3ºC. 467 ppm is only 67% of a doubling, so we want to prorate the 3ºC, presumably using a log function, hence:
2 ^ 0.67 = 1.59
1.59 / 2 * 3ºC = 2.4ºC
So I estimate that if we followed IEO2011/RCP8.5 out to 2035, and then stabilized our forcing, we would eventually arrive at an average global temperature increase of 2.4ºC. Am I even close? I haven’t forgotten Gavin’s advice “that I have to account for the thermal inertia of the oceans”, I’m just not ready to deal with that yet. In case anyone wants my spreadsheet it’s here.
403 wili, I was referring to the study which concluded that the Arctic Ocean used to have less ice than today. It used driftwood on Greenland’s northern shore as primary data.
“During the Holocene Climatic Optimum of 8,000 to 5,000 years ago, the Arctic sea ice was less than 50% (so less than 2.6 mln sq km) of the lowest extent on satellite record, the 2007 melting record, … during the HCO or HTM (Holocene Thermal Maximum) it was warmer than today – in the Arctic on average about 1.6 degrees Celsius.”
http://www.bitsofscience.org/arctic-sea-ice-holocene-2614/
I was curious as to reactions to something I just stumbled across, which is skeptics using a “study” that cites a revision of standards for ground station siting by Michel Leroy of METEO France. How this really changes things when it comes to the validity of temperature records is never made clear and in addition the folks at WUWT who are trying to push this meme seem to me to be trying to confuse the issue by making references to Leroy 1999 and Leroy 2010 as though these were peer reviewed papers, which I can’t find any evidence of.
What do people think of this?
http://www.dailymail.co.uk/sciencetech/article-2217286/Global-warming-stopped-16-years-ago-reveals-Met-Office-report-quietly-released–chart-prove-it.html
All of the silly journalism spin in the article aside, it would be nice if the RC folks could do a short post on this to put this in better context. My understanding from some of the climate model simulations was that 10 year “pauses” were fairly normal, but 15+ year pauses were quite rare in climate model simulations of GHG forcing…
Just curious. It’d be nice to know the broader context, as you can bet this will come up in many a Q&A on climate change talks and I would love to have a solid answer for it.
[Response: The funny thing is that the trend in HadCRUT4 from Jan 1997 to Aug 2012 is positive (0.047+/-0.038 deg C/decade – 95% CI, no adjustment for auto-correlation). See The Escalator for more. – gavin]
[Further Response: From the Met Office. – gavin]
Rather old, just came across this at the MET Office website:
http://www.thisisnorthdevon.co.uk/Royal-Navy-subs-supply-data-climate-change/story-15332781-detail/story.html
“… The dataset, from an unnamed UK submarine mission, is set to provide a snapshot of conditions under the ice and is said to be one of the few clues available for the last two decades on the changes taking place in the Arctic.
To process the information, the DSTL will work with the Natural Environment Research Council and the UK Hydrographic Office, which is based in Taunton, to prepare the data for researchers.
The information gathered will be handed over to academics at National Oceanography Centre, where researcher John Allen said it would provide clues on the impact of climate change in the Arctic….”
re 407 Hank Roberts – true, but I don’t think that was an issue in this case (we could all read his comment and understand how it applies to climate sensitivity; I do not think he was suggesting net positive feedback – except for Planck response (negative) – couldn’t exist without runaway, which is the usual problem we have with these differing definitions).
[
secondthird try at posting; never got “could not open socket” before]Re- Comment by Patrick 027 — 14 Oct 2012 @ 12:53 PM:
You said- “[second third try at posting; never got “could not open socket” before]”
So, you are saying that this was not a wrenching or shocking experience? Steve
Re 405 wili – you may have mentioned this already but it’s discussed here http://www.skepticalscience.com/Macdougall.html – from fig 2 (which was a little hard to read without buying/etc.) it looks like permafrost C has already been set to release but not completely. It isn’t a single-switch, total release situation.
#407 “Engineers and musicians define “feedback” for their work. Climatology papers define “feedback” differently. Same word, different definition.”
The term feedback comes from the mathematical description of systems called system theory and in any case except probably musicians means pretty much the same:
http://en.wikipedia.org/wiki/Feedback
I’ve studied control theory and you get to learn a lot about system theory there.
The term “acoustic feedback” http://en.wikipedia.org/wiki/Audio_feedback means something else, for that reason I took care to write “feedback” in the sense of system theory or “acoustic feedback” where I meant what musicians might name a “feedback”, because they are not much interested in feedbacks as long as the system stays stable.
#411 here is what the Met office thinks of it
http://metofficenews.wordpress.com/
wili (#405),
Maybe you should read the target paper. An equilibrium sensitivity of 6 C per doubling is suggested there and this feedback would be only part of that slow response. Fortunately, while RC wants to keep off the topic that explores “approaches to climate change mitigation.” The IPCC is taking that on as a part of climate science. So, DEP 2.6 looks a lot like Hansen at al.’s recommendation for a concentration target and approach to it. And, the new paper makes clear that the feasibility of that does not seem to be drastically changed by their findings. So, perhaps the new paper needs the words “Don’t Panic” written in large friendly letters on the cover.
http://pubs.giss.nasa.gov/abs/ha00410c.html
Re 416 Bernd Herd – in climate science, for global climate change, specifically a global (average surface) temperature change in response to a global (typically average net tropopause-level after stratospheric adjustment) radiative forcing (or other heat source – although on Earth those tend not to be so big), where the radiative forcing may be in units of W/m^2, so that equilibrium climate sensitivity is in K*m^2/W (it is often expressed as K/doubling CO2 as doubling CO2 has a certain amount of radiative forcing for given conditions). The feedback can be expressed as W/(K*m^2), a radiative feedback per unit temperature change, and in this form they add linearly. This includes the Planck response, which is just the increase in OLR (outgoing longwave radiation) in response to temperature according to the Planck function and the given optical properties. The Planck response is a negative feedback; including it, the total feedback is -(1/equilibrium climate sensitivity) and must be negative in order for equilibrium climate sensitivity to be finite. However, the Planck response is so fundamental that the feedback often refers to the other feedbacks, in which case the net feedback can be positive and the climate sensitivity, though it will be larger, is still finite (climate is stable). Also, the ratio of climate sensitivity to that with only a planck response may be considered.
The impression I’ve gotten is that some people, not knowing that ‘net positive feedback’ may exclude the Planck response, think that this must imply the climate is unstable – the funny thing is, this will be used to argue for a lower climate sensitivity, but one could see that something is wrong here because the higher climate sensitivity caused by the positive feedback is still finite.
In electrical engineering there’s Bode…
also helpful:
http://en.wikipedia.org/wiki/Feedback_%28disambiguation%29
and
http://en.wikipedia.org/wiki/Climate_change_feedback
http://www.ucsusa.org/scientific_integrity/science_idol/2012-cartoon-contest-contestants.html
To Patrick @ #415–Yes, I started with that useful Skeptical Science article (and yes, I did post a link to it above.) You write: “it looks like permafrost C has already been set to release but not completely. It isn’t a single-switch, total release situation.” I’d be curious to know what exactly in the article leads you to this conclusion. I do realize that they are not talking about all the CO2 coming out of the permafrost at once. I am concerned that we may already be committed to the eventual release of all the permafrost carbon.
Chris, I did read the original article, as might have been clear from the fact that I quoted from the middle of it. We seem to be getting different messages from it. Thanks for the link to the Hansen article, too.
Does anyone else reading the article–looking at the flat dashed line in figure three and putting that together with the fact that we know there will be other carbon feedbacks–come to my conclusion that this means we are now in a kind of runaway (not the Venusian kind, though)? If so, how long have we already been in it, and how steep is the slant of inevitable atmospheric CO2? If not, why not (as clearly and specifically as possible, if you would)?
Thanks for the responses and for the interesting conversation about different meanings of ‘feedback.’
(Oh oh, reCaptcha comments: ‘groans’)
I think my last post @408 didn’t have the math quite right, sorry! To calculate the change in average global surface temperature that would result from a given atmospheric CO2 concentration, assuming a given climate sensitivity, the function should be:
temp = log(concentration / 280) / log(2) * sensitivity
This assumes we’re interested in temperature change relative to the pre-industrial CO2 concentration of 280 ppm though that’s arbitrary of course. So for example if sensitivity is 3ºC the results are as follows:
280 ppm = 0ºC
560 ppm = 3ºC
1120 ppm = 6ºC
…
and 467 ppm = 2.21ºC, a bit less than my previous estimate of 2.4. Here’s a little PHP calculator script: calculate average global temperature change from atmospheric CO2 concentration
Assuming the above makes sense, my next question is, what about the timing? My simplified model just says that if atmospheric CO2 reaches 467 ppm in 2035, and magically stabilizes there, temperature would eventually reach 2.21ºC. It doesn’t take into account the thermal inertia of the ocean and probably lots of other interesting details.
How often people struggle with the fact that words have quite different meanings in different contexts.
To me, “feedback” will always intuitively mean Jorma Kaukonen’s guitar at the beginning of “The Ballad of You and Me and Pooneil”.
@ Chris Dudley — 10 Oct 2012 @ 1:13 PM re Munich Re
“Atmospheric scientist Clifford Mass of the University of Washington also has a problem with Munich Re’s findings, saying that once the data are adjusted for population there is no recent upward trend…”
current US population 314.58e6 Munich Re reports recent losses 36e9; 1980 losses 9e9. Therefore 1980 population must have been 78.64e6, not the 203.18e6 that everybody thinks. Who woulda thunk the evil cabal of climate scientists could manipulate census data as well as the temperature record?
Pielke has a more defensible argument – “”Thirty years is not an appropriate length of time for a climate analysis, much less finding causal factors like climate change,” – and he’s bright enough to cherry pick data sets with a lot of noise and statistically infrequent occurrences that do require more than 30 years (look! here’s a squirrel!) to be statistically significant, and conflate that with all climate data sets. How many years are required to show statistical significance in the decline of Arctic sea ice summer minima, or accelerating glacial mass loss?
@ Lorius´ car — 13 Oct 2012 @ 3:41 PM re Lucia’s public mathturbation of model vs weather
Lucia says
“If we apply test whether the observation the trend associated with Global Mean Temperature computed starting in Jan 2000, we reject the ‘null’ hypothesis that the observation falls within the spread of “weather” characteristic of a particular model in (2,5,4) cases based on comparisons to (GISS, HadCRUT3 and NOAA) respectively.”
Will Roger Pielke show up to dismiss Lucia’s work, and by implication all climate “skeptics” because they are trying to make something out of meaningless short term noise, or does he think that Munich Re’s 30 years isn’t enough, but Lucia’s 12 years is just fine? Remember the kerfuffle over Phil Jones’ “no significant warming since 1995”?
What would Lucia see if she ran her analyses of models versus every possible 12 year span of observations, instead of just the last 12?
@ BA — 14 Oct 2012 @ 11:15 AM regarding trends (Speaking of which, Is it just my imagination, is it just my imagination, or is there a new trend from the denialoshpere to muddy the waters by misuse & misrepresentation of trends?)
Endpoints do not equal trends – http://www.woodfortrees.org/plot/hadcrut4gl/from:1997.75/plot/hadcrut4gl/from:1997.75/trend
for deeper background see http://tamino.wordpress.com/2012/07/06/how-long/ http://www.skepticalscience.com/trend.php and http://www.skepticalscience.com/global-warming-stopped-in-1998.htm
Chris (#423),
You can look at the climate response functions I mentioned back here:
https://www.realclimate.org/index.php/archives/2012/10/unforced-variations-oct-2012/comment-page-7/#comment-264341
wili (#422),
I was writing too fast. By “target paper” I meant the Hansen et al. (2008) paper “Target atmospheric CO2: Where should humanity aim?” that I linked. I know you’ve read MacDougall et al. (2012). My point was that the new work has been anticipated in its basic points in the emissions trajectory proposed in the 2008 paper.
Brian (#425),
I’m still looking for the Munich Re report. If you have a link please post it. In your loss numbers, have you adjusted for inflation?
I’ve been looking at the WG I reference document for AR5 and have found this nice concise list of topics that I think should be considered on topic of RC unforced variations discussion. This does entail including scenarios as on topic, something Gavin wanted off topic. They are drawn in because they are tied to representative concentration pathways (RCPs), the basis for this chapter. RCP 2.6 is of particular interest because it includes reversibility through mitigation efforts, somewhat of a departure from AR 4.
http://www.ipcc.ch/pdf/ar5/ar5-outline-compilation.pdf
Chapter 12: Long-term Climate Change: Projections, Commitments and Irreversibility
Executive Summary
• Scenario description
• Projections for the 21st
century
• Projections beyond the 21st
century
• Regional climate change, variability and extremes
• Forcing, response and climate sensitivity
• Climate change commitment and inertia
• Potential for abrupt change and irreversibility in the climate system
• Quantification of the range of climate change projections
Re #419 Patrick 027: Climate Science is just an application of system theory. For that reason they separate between forcings and feedbacks. Forcings do not depend from the actual temperature, feedbacks do. For that reason, CO2 from fossile fuels is not a feedback, but a forcing.
In the microphone-amplifier-speaker analogy, this means the “forcing” is comparable to the guitar sound that you wanted to amplify.
The Permafrost Carbon Feedback PCF is a feedback, and not a forcing, because it depends on the temperature already reached. And until now I can’t see any difference between a “self-sustained” PCF and an unstable system for a short-time analysis. In a long-time analysis the unlinearity of the system will be too important to allow a linear approximation. I wouldn’t know how to apply a Bode Diagram here.
In sytem theory the planck response is just a negative feedback and for short time analysis can be approximated as nearly linear with some factor. If the sum of all positive and negative feedbacks becomes > 1, then the system is unstable. I know that this is only an approximation, for the system is non-linear. However I can’t see what aspect would contradict the idea that one could probably define a maximum CO2 climate sensitivity by appplying the PCF model to past temperatures, except maybe if the climate sensitivity itself would be non-linear?
#422 wili: “Does anyone else reading the article–looking at the flat dashed line in figure three and putting that together with the fact that we know there will be other carbon feedbacks–come to my conclusion that this means we are now in a kind of runaway (not the Venusian kind, though)? If so, how long have we already been in it, and how steep is the slant of inevitable atmospheric CO2? If not, why not (as clearly and specifically as possible, if you would)?”
The authors of the article show, that the answer to this question depends on the CO2 climate sensitivity. 3°C and more means that we already triggered that runaway effect, less than 3°C means it has not happened yet.
The best estimation from the 2007 IPCC report is 3°C, so we’ve got a 50% chance of not beeing doomed to this additional CO2 release to the atmosphere.
I mostly wonder, if the effect was obviously not triggered a long time ago, and it has been triggered now with 0.8°C warmer earth at 3.0°C climate sensitivity, if we continue to emit CO2, won’t 2.0°C climate sensitivity become sufficient if we continue CO2 emissions for some decades? And the 2007 IPCC report says a climate sensitivity below 2.0°C is very unlikely.
See also “uncertainty is not your friend”:
http://www.shapingtomorrowsworld.org/lewandowskyUncertainty_I.html
And obviously stopping CO2 emmissions immediatly is also very unlikely.
“If so, how long have we already been in it”? I guess since about 1900, for our actions, even our mere existance, is part of it. We cannot return into the state of mankind we had before 1900 without most of us dying for starvation.
James Hansen changed his mind in about 2004 and now states that the atmosphere must not remain beyond 350ppm CO2 for a long time and calculated that there are still chances of reaching that goal:
http://www.columbia.edu/~jeh1/2008/TargetCO2_20080407.pdf: “An initial CO2 target of 350 ppm, to be reassessed as the effect on ice sheet mass balance is observed, is suggested.”
As part of his scenario he suggests to take away a part of the CO2 by intensive reforestation.
So according to the Permafrost Carbon Feedback article our actions are still part of the runaway scenario, we could still change our actions. But this might change in the future. The time remaining for actions might be short, even if the full consequences might take centuries to develop. But if there are additional feedbacks coming in, the time might not even be several centuries, see http://www.ameg.me/ . I can only hope that they are wrong.
Note: I’m not a Climate Scientist.
Bernd (#430),
Runaway is possible but it occurs at 10-25 W/m^2 higher or lower forcing than today. The supplementary materiel in this paper http://pubs.giss.nasa.gov/abs/ha00410c.html particularly surrounding fig. S3. provides a brief discussion. It should be noted that raypierre objects to the high end argument presented there and elsewhere.
Here it comes:
I’m not sure that “unexpected events” is the right term anymore, given that we have every reason to expect widespread, severe, prolonged drought next year, and every year for the foreseeable future.
Predictions that AGW could cause agriculture to collapse world-wide by mid-century, once considered “alarmist”, may — like many other “alarmist” predictions — prove to have been optimistic.
Last word from me for now on this… I have attempted to recommend Tom Murphy’s blog Do The Math (possibly OT, but with the excuse that I am trying to point out one good venue for energy discussions), with a few responses here, mainly unreasonable, defamatory to Tom, and at a far lower level of thoughtfulness than Murphy’s blog itself. For the rest of you with possibly more open minds, give it a try, starting from the beginning. The posts make sense in order, and you can skim the ones of lesser interest to you. You will notice a certain open-endedness, which arises from the topic itself, in which much is unsettled.
Hint: if you really really want something, that doesn’t necessarily make a sentence starting with “I need [something]” more plausible. Applies very well to energy technologies.
Bernd, search ‘ameg’ here and at
http://scienceblogs.com/stoat/?s=ameg
Ric, kibitzers show up here (as everywhere online) making seemingly authoritative pronouncements without credentials or publicly known name or reputation. The regular readers here learn to check whether someone has anything behind their opinion.
Ric Merritt wrote: “I have attempted to recommend Tom Murphy’s blog Do The Math …”
I did peruse Tom Murphy’s blog. My comment about it here mentioned only his impressively detailed analysis of his own, equally impressive do-it-yourself home PV system — but by no means was that the only thing about it that I found valuable. As you (I think) mentioned earlier, his general discussions about energy consumption are, I think, very intelligent and important. I’ll be going back to read more, and I’m happy to second your recommendation.
#434 Tom Murphy’s blog
Ric, the alternative energy system on his blog that some people are swooning over was worked out over thirty years ago by sailboaters and island dwellers. It’s great, but it won’t get you off the grid if you are still running compressors in a conventional home (or if you are already off it before you started building the system as most people are) and you’d have to scale it up immensely to satisfy the energy hunger of suburbia. I can only speak for myself but I’ve moved on, several decades ago actually. This is the third time you’ve recommended his blog here and the third time I’ve had to remind you that there is very little math there (I think I saw one post there using thermodynamic quantities) and he more or less uses it to push an obsolete worldview on people who don’t have the mathematical skills to challenge his beliefs. Our human problem has become so severe through extreme neglect and the unwillingness to engage in confrontational behavior that it’s more or less now going to take two dimensional an carbon based quantum simulators using a Manhattan style project and Apollo style national effort in reusable launch vehicles to even come close to solving it in the timeframes that will make any difference. Unfortunately in this country there are rabid Christian fundamentalists sitting on YOUR congressional and senate science and technology committees.
I know that offends you. That is my intent. I’m just getting the job done.
Re- Comment by Ric Merritt — 15 Oct 2012 @ 11:47 AM:
On your recommendation I read quite a bit of Murphy’s blog. I enjoyed it. I passed it on.
Steve
ps for Ric — earlier some newly-arrived guy claimed he found no math on the “Do The Math” blog.
Serious readers here learn to be skeptical of broad-brush dismissals of scientists’ work by self-proclaimed experts.
E.g. see http://physics.ucsd.edu/do-the-math/2011/08/recipe-for-climate-change/ or http://physics.ucsd.edu/do-the-math/2012/09/blow-by-blow-pv-system-efficiency/
Any reactions to this yet (which a denier friend sent me today)?
http://www.dailymail.co.uk/sciencetech/article-2217286/Global-warming-stopped-16-years-ago-reveals-Met-Office-report-quietly-released–chart-prove-it.html#ixzz29N4dARKF
Thomas Lee Elifritz wrote: “you’d have to scale it up immensely to satisfy the energy hunger of suburbia”
You know, the idea that the problem we need to solve with regard to phasing out fossil fuels is to find other ways to “satisfy the energy hunger of suburbia” has got to go. I think that’s one of the points that Tom Murphy makes on his blog.
A very tiny percentage of human beings have “enjoyed” that profligately wasteful, inefficient and downright stupid level of energy consumption for a tiny fraction of human history.
If saving the world means that they need to get their fat bottoms out of their SUVs and walk a bit, and perhaps read some books in modest but cozy homes instead of gazing at the giant plasma TV screens in each and every room of their McMansions, well, it’s not the end of the world.
broad-brush dismissals of scientists’ work
I’m not dismissing Tom Murphy’s ‘work’, Hank, I’m dismissing his ‘blog’ as being relevant to the scale of the problem. For education, it’s just fine, but for actual solutions, I can recommend the peer reviewed literature. Educating the lay public about some simple arithmetical details of the radiation imbalance is not going to solve the problem created by the radiation imbalance, since the scale of the problem now exceeds even the most modest approaches to its solution. It will now require ‘big science’, bigger than anything heretofore accomplished including the bomb and the Apollo program.
In particular, since recommendations are being made, I can recommend this as indicative of the types of condensed matter physics breakthroughs necessary to solve a problem that I in particular have now known to exist for several decades now.
Hank, with regard to your fist link to Murphy’s blog — “Recipe For Climate Change” — unfortunately, I have to say that his introduction shows that he really doesn’t get it when it comes to global warming:
Um, no.
A “decline in the availability of cheap energy” — i.e. peak oil, and more generally peak fossil fuels, could — if we handle it very stupidly — cause some very serious economic and social disruptions to human society.
But it won’t melt the polar ice caps, and kill the forests, and turn the world’s most productive croplands to deserts, and acidify the oceans, and cause the mass extinction of most life on Earth. Unmitigated global warming could easily do all of those things.
Chris Dudley @426: Re 2011 Hansen et al, there’s enough material there for three papers! And it ends disappointingly with a whimper. But never mind, my take-away is that they’re asserting a three-phase approximation of climate response as follows:
40% after 5 years (the “fast” response)
75% after 100 years (the “slow” response: as opposed to 60% currently used by most models)
and 100% after a millennium (the “recalcitrant” remainder)
Would you agree with this summary? I’m working on a numerical model that emulates it. Input will be a CO2 concentrations time series, e.g. from an RCP scenario, and output will be a temperature change time series. Presumably the output will look very different from this: Temperature increase from RCP8.5 CO2 concentrations (instantaneous climate response), which is just a straightforward application of the “naive” calculation I introduced at @423, with sensitivity = 3.
Re 434 Ric Merritt – I like it (Tom Murphy’s blog). (When reading through the comments I saw this mentioned alongside ~’Mott electronic lattice frustration’ so initially I expected some quantum physics, but that was just a mix-up. I agree there’s math there.)
Re 422 wili – I was looking at figure 2 (as best I could in the little version you get from behind paywall) – it looks like, for the DEP 4.5 emissions ((DEP refers to forcing (from anthropogenic emissions, I think) W/m^2 in 2100) a bit more than doubling CO2 by 2100, setting aside other GHGs), if sensitivity is 3 K/doubling, the permafrost reservoir declines but starts to level off significantly before reaching 0 (I believe that’s 0 % of the permafrost reservoir?). For the higher sensitivity of 4.5 K/doubling, the decline slows before reaching 0 but still looks like it’s approaching 0 – this is similar to the DEP 8.5 at 2 K/doubling sensitivity; the higher sensitivies at DEP 8.5 lead to more of a quasi/pseudo-‘hard landing’ for permafrost C (rapid approach to 0 and only ‘slowing down at the last minute’). Also, from http://www.skepticalscience.com/Macdougall.html, under “Counter-intuitive results“,
…
…
…
So it should become more likely that some permafrost C remains indefinitely, as well as more for any given short time period, if there is less forcing.
And, even after dropping aerosol cooling, we still have to add CO2 (or other GHGs) to the atmosphere to complete a DEP 4.5 scenario (setting aside perturbation time (of CH4, for example), it occurs to me that it is best to have it all as CO2 as this would reduce the radiative impact of the permafrost CO2. On the other hand, anthro-CH4 would partly reduce the impact of feedback CH4 (how much, I have no idea) … oh well).
On the other hand, that’s assuming all permafrost C is emitted as CO2. So our room to avoid permafrost runaway will be smaller, but I couldn’t say by how much.
(An author response at skeptical science: http://www.skepticalscience.com/Macdougall.html#86182
I don’t know if the author is still responding; I haven’t followed the thread)
Re 430-431 Bernd Herd – I’m comfortable with the guitar-microphone-amplifier analogy.
There is a concept called ‘Charney sensitivity’, which generally includes feedbacks that act fast (faster than the climate can equilibrate to any forcing) (and perhaps it might be said, are more obvious and easy to understand, generally abiotic?)… I think it includes H2O vapor, clouds, seasonal snow and sea ice (I’ve been over this before but I always find myself questioning whether it does include those last two or not; I’d expect it does). I don’t think it includes vegetation albedo or aerosol feedback; it definitely does not include biogeochemical feedbacks that could add CO2 or CH4 to the atmosphere; it also exludes ice sheet albedo feedback, which is generally slower than the climate response time. There is something called ‘Earth system sensitivity’ –
see:
http://www.skepticalscience.com/hansen-and-sato-2012-climate-sensitivity.html
… to be cont.
Odd how so many here go on about energy and CO2 when in fact our problem, as Tom ‘Do the Math’ really points out, is the unsustainable nature of human impact on the planets resources …. ultimately meaning the sheer numbers of consumers and would-be consumers as much as their level of consumption. I think he’s right to be concerned with the impact of our over-consumption of all resources, including, but not at all limited to, fossil fuels. Our economic and social systems are already showing the strain of the “techno-fix” attitude expressed by some here regarding planetary limits.
The arctic will not be planted with Yarrow to improve its albedo in anyones lifetime, especially not the arctic ocean. Drylands and deserts will not be planted to trees to draw down carbon when ever decreasing water supplies are needed to grow our food. The “smart grid” won’t smarten up as long as there’s cheap coal to burn. Coal and petroleum won’t get too expensive to use as long as the money derived from them elects your governments.
SA@433 points to the warning of food production problems [link], with the shortage of stockpiles said to be the lowest since 1974 – when there was “only” 4 billion of us on the planet. Yes, “breakdown is inevitable, unless urgent action is taken”, but the only urgent action likely to change things is a drastic reduction in population, which the planet may well be about to implement for us.
Correction?
– re my re wili 422 – from the skeptical science post: “Note that a self-sustaining feedback is not the same thing as a runaway greenhouse effect.”
– so it may be that the threshold forcing for releasing all permafrost C is not a threshold for permafrost C runaway but simply the point at which the source of the feedback has been exhausted. Thus our room to avoid ‘runaway’ that I stated earlier would then be the room we have to keep some nonzero C amount in the permafrost. Running out of permafrost C would then be like running out of surface water to feed the water vapor feedback, of the ocean were sufficiently shallow (to stay out of H2O-runaway territory).
Chris (#445),
That sounds like one of the things they tried. I noticed when I implemented their Green’s function approach to a sudden end to emissions, that the temperature began to fall as soon as emissions dropped while the forcing should still have been causing the temperature to increase. I also tried to implement their function as a lag that finishes quick for small changes in forcing but drags for larger changes, but the functional form made that delay a long time to get any temperature rise at all with a BAU type emissions profile. I think we can say that the response function represents the response to a step function doubling in concentration but working backwards from that to a response to a different forcing profile (other than high frequency volcanic forcing it has also been tuned to) may not be so easy.
But it may also be the best tool available so far to do approximations without full model runs.
fixible (#477),
The article is a little ambiguous, but when they give units is is in days of consumption. Might it not be that population growth and improved nutrition has been factored into the statement about 1974?
And, wasn’t 1974 just after the Soviet crop failure? Not too surprising if carryover stocks were low then as now.