Home/BlogI am seeing increasing chatter about one or more papers that will (or already have) debunked my ideas on feedbacks in the climate system.
Yet, I cannot remember a climate issue of which I have ever been so certain.
I understand that most people interested in the climate debate will simply believe what their favorite science pundits at RealClimate tell them to believe, which is fine, and I can’t do anything about that.
But for those who want to investigate for themselves, I recommend reading only our latest and most comprehensive paper in Journal of Geophysical Research. It takes you from the very basics of feedback estimation — which I found I had to include because even the experts in the field apparently did not understand them — and for the first time explains why satellite observations of the climate system behave the way they do.
No one has ever done this before to anywhere near the level of detail we do.
[Unfortunately, our 2008 paper in Journal of Climate, I now realize, had insufficient evidence to make the case we were trying to make in 2008. I believe our claims were correct, but the evidence we presented could not unequivocally support those claims. Only after finishing our most recent 2010 paper did I realize the insufficiency of that previous work on the subject.]
Then, once you think you understand the main points we make in the new JGR paper, read any other critiques or criticisms that catch your fancy.
As a teaser, one of the clear conclusions the new paper supports is this: The only times that there is clear evidence of feedback in global satellite data, that feedback is strongly negative.
All I ask is that you evaluate whether anyone can come up with a better explanation than what we have given for the structures we see in the satellite observations of natural climate variations. Do not settle for others’ vague arm-waving dismissals based upon preconceived notions or what others have told them.
You engineers and scientists from other fields are capable of understanding this, and I am appealing to you to bring fresh eyes to a field where the research establishment has become hopelessly inbred and too beholden to special interests to see that which is staring them in the face.
This is the main reason why I wrote The Great Global Warming Blunder…the evidence is simple enough for the science-savvy public to understand. But the experts do not see the evidence because they refuse to open their eyes.
 |
The gauntlet is thrown!
Although you are to be commended on the paper, which I find compelling and, for a technical paper, relatively clear, I had hoped to find a supplemental-information link to the data and programs behind your graphs and tables so that interested parties would be able to crunch the numbers for themselves.
Such supplemental information would be helpful not only in dispelling evident ambiguities–which are almost inevitable in even the clearest papers–but also in revealing latent ambiguities.
As an example of latent ambiguity, I’ll observe that it was only by actually studying your simple-model spreadsheet (which antedates the paper) that I recognized your having used (in my opinion, harmlessly) a less-than-desirable smoothing operation. (Because you used a 30-year average for the smoothing, the pseudo-random radiative-anomaly signal you ended up with had a significant negative autocorrelation at a 30-year lag.)
In short, your audience would have greater confidence in, and a deeper understanding of, your paper’s results if you provided data and programs that enabled your audience to crunch the numbers for itself.
I’ve followed your work with interest. There is a way to allow your analysis to co-exist with others and it comes from my initial discipline, phase transitions and kinetics.
The way to understand it is an English anecdote “Three hot days then a thunderstorm”. In the tropics it’s a thunderstorm every day! And therein lies the clue.
Positive feedback is the process of greenhouse gas warming, evaporation increasing absolute water vapour concentration in turn triggering more IR trapping. Eventually the system enters an unstable equilibrium whereby even a small perturbation triggers negative feedback – weather. That’s a phase transition with its own kinetics. The water precipitates in various ways and the latent heat release triggers convection right the way to the stratosphere. It’s much faster in the tropics.
But there is another issue: how can the likes of a collapsed thermosphere [e.g. the 2009 fall in extreme UV output of the sun] and the arrival of solar flares from an active sun trigger significant changes of weather at the ground, and they do.
The clue here is the concept of the ‘heat valve’, an analogy with the grid in a vacuum tube which can modulate electronic charge transfer. Modify the radiative thermal impedance from the upper atmosphere and you change the heat transfer all the way to the ground. There may well be delays, but that modulation is the cause – a bit like tickling the scalp causing the toes to move…..
PS the IPCC’s predicted AGW forcing is based on an assumption about cloud albedo change by pollution which cannot be substantiated experimentally. The idea appears to have been based on extrapolating the ‘Twomey Effect’. Look at his theory, Mie scattering, and it breaks down for thick clouds. Also, it predicts a maximum albedo of 0.5 when measured values are greater. What is amusing, and possibly very serious, is that NASA literature claims ‘more smaller water droplets have higher surface area so reflect up to 90% of sunlight’. That completely false physics appears to be widely believed in climate science. The real explanation is that there are two optical process in clouds. The lidar people know it.
Take away the unproven cloud albedo cooling, known by 2004, and the IPCC’s predicted AGW forcing has to be halved.
RE: The Late President Eisenhower’s Second Warning
This passage from “The Farwell Address to American People”
follows the text where he mentions the familair “military-industrial complex.”
IIRC, this passage in part was based on his confrontations with the ruthless egomaniac Edward Teller who convined the Congress and American people to pursue the development of the H-bomb, which he recognized asa true weapon mass of destruction, and believed was unnecessary and would result in an extremely expensive weapons program and greatly increase then severity of the cold war with the Russians.
“Akin to, and largely responsible for the sweeping
changes in our industrial-military posture, has been
the technological revolution during recent decades.
In this revolution, research has become central; it
also becomes more formalized, complex, and costly. A steadily increasing share is conducted for, by, or at
the direction of, the Federal government.
Today, the solitary inventor, tinkering in his shop
has been overshadowed by task forces of scientists in laboratories and testing fields. In the same fashion,
the free university, historically the fountainhead of
free ideas and scientific discovery, has experienced a revolution in the conduct of research. Partly because
of the huge costs involved, a government contract becomes virtually a substitute for intellectual curiosity. For every old blackboard there are now hundreds of new electronic computers. The prospect of domination of
the nation’s scholars by Federal employment, project allocations, and the power of money is ever present
and is gravely to be regarded.
Yet, in holding scientific research and discovery in respect, as we should, we must also be alert to the
equal and opposite danger that public policy could
itself become the captive of a scientific-technological elite.”
I think you maybe over-estimate the average scientist’s understanding of this complex field. Whilst your paper seems consistent and well presented, I think a degree of familiarity with the data is necessary to have much chance of poking holes in it. Certainly, I will be interested to see if anyone attempts more than a hand-waving exercise to dismiss it (and I find it easier to evaluate the counter argument by how specific it is).
As a follow-up, some bounds on testability would be interesting. What is the shortest data-set which could be analysed in isolation and be shown to be consistent or not with your simple model? I have a feeling that the next step is to investigate the detailed alignment of the grown-up models with actual observations (and that seems very non-trivial). Without that step, your simple model remains just a possible approximation, and difficult to prove (seeing as it is hard to decide if surface temperatures are consistent with the current models).
Dr Roy
I’m probably not your ideal reader in that my science education aint the best and so I won’t be offended if you are not waiting with anxious anticipation for my perspective.
I simply want to point out that you really don’t need to over egg the significance of your argument. If it stands it will stand if it doesn’t …well I suppose that’s just the way science works.
You want an honest opinion of your paper but then you immediately say that you’d rather people didn’t swallow any real climate arm waving (please excuse the mixed metaphor).
This could lead to the uncomfortable conclusion that a negative critque of your paper (which is far from a foregone conclusion) will be dismissed as partisan posturing. Was that your response to the criticisms of your original paper which you now concede was flawed? Do you see what I’m getting at?
I enjoy your blog as you explain complex principles clearly and patiently. I also admire, for the most part, your good humored moderation of the debates that ensue.
The passions around the AGW debate are both understanable but limiting. From my reading once you concede that the increase in CO2 is predominantly anthropogenic, once you concede that CO2 as a greenhouse gas ‘warms’ the climate then the big issue to be resolved is the question of climate sensitivity? Am I wielding Ockhams razor carelessly?
If this characterisation is correct then all the attention your paper garners may not be because the establishment wants to bring you down but perhaps simply because it is the biggest question which needs to be addressed and as such not only requires intense scruitiny but demands it.
But it would be lovely if we could all concede to the other good faith but at the same time when that good faith is lacking remain a little indulgent for in these matters regardless of our passions science has the habit of rendering them innocuous.
Please forgive any presumption if it appears a puppy is trying to teach granny to suck eggs.
All I am saying is ask for the evidence if someone claims to have refuted our ideas…don’t settle for just arm waving.
And, to answer your question, when we saw a written critique of our first (2008 J. Climate) paper, we looked into it and verified that the objection was valid…that we had NOT adequately demonstrated that feedback diagnoses lead to a bias in the direction of high climate sensitivity. When I am wrong, I admit it and move on. That’s science.
Plants can’t grow without carbon.
When the climate warms, more plants grow (feeding more animals and people).
When the climate cools, fewer plants grow (starving animals and people and causing starvation and epidemics of plague and such-like).
Pray for global warming and enough carbon in the atmosphere to make plants grow well and lushly.
If reduction of atmospheric carbon is possible, we don’t want it because we want to continue to eat. Less carbon, less food. Eliminate politicians who continue to prattle about this. They are dangerous because they hold pursestrings that can cause very bad things to happen.
Dr. Spencer –
Does the chatter have any discussion of a basis for the debunking your ideas, or are they just general statements that the paper will be debunked?
I have yet to see any basis…except for my aforementioned agreement that out 2008 J. Climate paper did not adequately demonstrate what we were claiming. Beyond that, I have seen nothing that would refute anything in our new (2010) JGR paper.
Let me emphasise what Sean Houlihane wrote “I have a feeling that the next step is to investigate the detailed alignment of the grown-up models with actual observations (and that seems very non-trivial). Without that step, your simple model remains just a possible approximation, and difficult to prove (seeing as it is hard to decide if surface temperatures are consistent with the current models).”
No model has much meaning until it has been validated. The way you validate models is to accurately and quantitatively predict the future. Surely the next step is to predict what some future experimental data will be. And then let us see whether it turns out to be accurate.
Jim, what you suggest has yet to be done in the climate arena. And it is not clear what kind of forecast would even validate a climate prediction. Warming could continue for 20 years, as the IPCC predicts, but that doesn’t mean they have the correct reason why it warmed.
I can flip a coin to predict whether the stock market will be higher or lower tomorrow, and I will on average be right 50% of the time. Doesn’t that make my coin-based model pretty good? 🙂
Christopher Game commenting on Dr Spencer’s article On the Debunking of Spencer’s Feedback Ideas: An Appeal to Physical Scientists Everywhere, posted 2010 Sep 1.
I would like to take this opportunity to say something about feedbacks, especially since I think that perhaps Dr Spencer thinks I am opposed to the use of the idea of feedback in the study of climate dynamics.
No fear! I am keen on the idea of feedback in the study of climate dynamics. There is no other way. I think Drs Spencer and Braswell are right to work on feedbacks in climate dynamics. I applaud them for their work in this.
I have attacked the IPCC’s meretricious and seductive “forcing and feedbacks” formalism, not because it works on “feedbacks”, but because it is structured about the confounding notion of “forcings” and because it works its “feedbacks” in unphysical ways, and because it does not use explicit system-independent driving functions. The IPCC formalism’s “forcings” are really feedbacks dressed up as if they were driving functions. This makes them practically impossible to interpret in terms of cause and effect. I interpret Drs Spencer and Braswell’s 2010 JGR paper as evidence in support of my attack on the IPCC formalism. I have also other reasons for finding the IPCC formalism hopelessly flawed, but I will not detail those reasons here.
The purpose of my attack on the IPCC formalism is to alert people to its flaws, so as to stimulate people to try to invent, and to use instead, simple tailor-made physically based theories for the study of the physics of the effects of CO2 on the energy transport process of the earth’s atmosphere.
Careful.
If climate scientists agree that anthropogenic climate change isn’t dangerous, then the public will be convinced that it is and CO2 policy will be passed.
good point…hadn’t thought of that.
Dr. Spencer,
It is not a wonder that the journalists don’t get your paper or those of others when they are like this one: you need two, not one. The first is dry-as-a-bone, non-contentious, so that it passes the editors. The second that says, “We established X in our paper. The IPCC claim Y, and others say Z. Because X trumps Y and Z, the following fails and the subsequent is going to happen.”
But that would be having an opinion. Stats are inviolable, but conclusions can be challenged. The odd thing is that “science” is all about conclusions. I’m a geologist faced with a lot of data coming from others. Data is only useful when it combined with context, when it becomes “information”. Information then leads to conclusions. The non-science based observer doesn’t understand this process. He thinks data is hard and leads to unique solutions. The simpler, the better (misunderstanding Occam’s Razor along the way).
I hope your work gets translated into something that a RealClimate reader can understand, otherwise other number-crunchers can ignore it.
Recently, using the brain that my mother told us God gave us for the purpose of figuring things out for ourselves, I looked into the simple depiction of how the TOA insolation was broken down into its warming and non-warming parts. I was shocked to see the annual variation of 6.8%, or +/- 47 W/m2. A post of yours mentioned that the global temperatures, however, were backwards to the aphelion and perihelion positions by about 2.3C*. The IPCC claims that a doubling of pCO2 from 384 ppmv generates 5.6W/m2 of radiative forcing, yet the annual variation in TOA insolation is almost 8X that, and still a 2.3C* reverse differnce exists. The difference is, by IPCC pCO2 extimates, about 2.8 W/m2 of forcing. Amazing. 47 extra and the world is 2.8 COOLER.
The buffering of the global temperature is very strong. The land/sea geometry (you pointed out) creates the greater warming when orbital characteristics say the world should be cooler. Geometry is obviously extremely important, and yet the IPCC claim that the cloud cover variation is unimportant (as it averages out). Only a slight variation in reflective geometry creates the same forcing as changes in pCO2, yet it can be dismissed. Only a slight change in how the thermal energy is being distributed would equal the power of pCO2 increases, but that, too, is dismissed. The TOA “natural” variation is so great that the idea that we are in equilibrium is bizarre: unless you think that running rapidly back and forth on a seesaw without falling off means the seesaw is in an equilibrium position. We are in a dynamic equilibrum, not static, situation. As such, any slight miscalculation in our speed of movement means the seesaw sags down at one end or rises precipitously at the other. This does not mean we are sensitive (though we can be to the main drivder, the sun) but that we live within a somewhat chaotic system. To say that we are responsible for such a tiny temperature rise is to assume a tremendous equilibrium that does not exist.
Roy, Many thanks for taking note of my message. You write “Jim, what you suggest has yet to be done in the climate arena.”
When I learned basics physics as an undergraduate, I was taught that physics is based on experimental data. A hypothesis is an idea with no experimental data to support it; a theory is an idea with some experimental data to support it; a law is an idea with overwhelming experimental data to support it. What I observe with AGW is an almost complete lack of experimental data. We cannot do a controlled experiment to add CO2 to the atmopshere, and measure how much the global temperature rises. AGW is a hypothesis. What I am waiting for is an experiment like Michelson/Morley on this issue. I was hoping your paper was a step in this direction.
In the meanwhile I am left with my opinion that, when it comes to AGW, the physics is not good enough to tell what is happening. We just dont know.
“I simply want to point out that you really don’t need to over egg the significance of your argument. If it stands it will stand if it doesn’t …well I suppose that’s just the way science works.”
Sadly, that’s often not the way science works. As Dr Spencer says, scientists are affected by their biases and often don’t see good arguments and evidence right in front of their faces. History is filled with examples of majority scientific views hanging on long after they have been refuted.
Part of our job as truth seekers, beyond presenting good argument and evidence, is the communication of those arguments and evidence in better and better ways to help them prevail.
Dr Spencer,
I’ve read counters to the notion of a strong negative feedback that point to global temperature increases of 5 – 6C during the ~5k year glacial terminations – that insolation changes are too small to make such a large impact.
How do you see the biosphere altering so significantly through ice age shifts under the provisions of the theory of strong negative feed backs to forcings? And how is it that the warming is global, rather than localised at the particular pole that receives more sunlight during Milankovitch cycles?
I do not think we know what caused the main glaciation events. They are not well correlated with the Milankovitch cycles.
Sorry, neglected to fill in the bars. That last post was from me.
Barry.
Thank you for the reply, Dr Spencer, but it doesn’t really answer my query. I’ll try to be clearer.
There is ample evidence of a global temperature change of 5 – 6C during ice age cycles. The global climate clearly responded to some kind of forcing that warmed/cooled it. There must be a reason why the great ice sheets melted away and reformed.
1) Does your calculation of a strong negative feed back to forcing permit such shifts?
2) If so, what would be the magnitude of forcing for a 5C change in global temperature, taking into account your estimated climate sensitivity?
3) Have you speculated on what mechanism(s) may have been strong enough to alter the global temperature so greatly in the face of strong negative feed backs?
@ barry
Try:
Roe, G. (2006), In defense of Milankovitch, Geophys. Res. Lett., 33, L24703, doi:10.1029/2006GL027817.
Thanks Dominic. I’m not eager to delve too deeply into paleoclimate (and stray too far from the topic), but while the Roe paper posits summertime insolation being the primary driver of ice sheet reduction in the Northern Hemisphere, temperature change (and ice sheet reduction) is global through the ~100k deglaciations. Thus, I’m wondering how Dr. Spencer’s theory of strong negative feed backs fits within this regime.
If we were to consider the NH only, then the polar temperature change from trough to peak is 10 – 12C during deglaciation, and ~3C in the tropics. Whether the radiative forcing comes from GHGs or solar variance, strong negative feed backs would be in play. My query would still apply here. If climate sensitivity is low, how does orbital variance, with a fairly weak insolation change in the NH (or SH), result in such profound shifts?
I don’t know if Dr Spencer has considered his theory WRT to ice age shifts, but it is one of the primary rebuttals to the notion of a low climate sensitivity. Hence my curiosity here.
“100k”
should be;
100k year
@barry
You say:
‘the Roe paper posits summertime insolation being the primary driver of ice sheet reduction in the Northern Hemisphere, temperature change (and ice sheet reduction) is global through the ~100k deglaciations.’
June insolation at 65N is indeed very much an NH phenomenon(!) BUT, to paraphrase Roe, ~85% of the ice during the last glacial maximum ~21ka ago was in the NH [Peltier 2004].
NH ice melt introduces fresh water into the high latitude oceans and global-scale climate change gets under way. The NH versus global climate change problem is resolved.
The large, rapid deglaciation that occurred at the end of some ice age cycles may be attributable to the internal dynamics of ice sheets. Rapid collapse may occur if a threshold size is exceeded [Imbrie & Imbrie, 1980; Paillard, 2001]. [I’m still just paraphrasing Roe here BTW].
Speaking for myself, I suspect that climate sensitivity itself varies depending on the forcings involved and the dominant climate state (ie ice age or temperate).
Excursions from temperate to ice-age conditions and back again are obviously the defining characteristic of the Quaternary. Powerful positive feedbacks associated with the EXTENT of NH ICE COVER utterly dominate.
But does this mean that temperate climates are protected from significant WARMING by negative feedbacks?
Put another way – is it misleading to treat the dynamics of climate sensitivity that control the onset and end of ice ages with the way negative feedbacks might inhibit warming caused by CO2 in a temperate climate?
I’m not sure that there is a definitive answer to this question as yet. So I’m equally unsure that it is safe to assume that Dr Spencer’s argument is invalid on the grounds of ‘conflict of sensitivities’.
You raise an interesting point and this is merely my tuppence-worth. I do not claim to be right or that you are wrong.
Apologies for the gibberish in my comment above. It’s obviously been a long week. Perhaps what I meant to say was:
Speaking for myself, I suspect that climate sensitivity may vary dependent on the forcings involved and the dominant climate state (ice age/temperate).
Excursions from temperate to ice-age conditions and back again are the defining characteristic of the Quaternary. Powerful positive feedbacks associated with the EXTENT of NH ice cover appear to drive major climate change.
But are the dynamics of climate sensitivity that control the onset and end of ice ages distinct from negative feedbacks that may inhibit warming caused by CO2 in a temperate climate?
I’m not sure that we actually know. A ‘conflict of sensitivities’ may not exist between Dr Spencer’s position and paleoclimatic change.
With regard to the glaciation cycle arguments: The cases of Milankovitch forcing and CO2 forcing are NOT analogous. Many people are mislead by the focus on a particular latitude at a particular time of year insolation figures into think that this is the quantitative, global effect, that’s the same everywhere. If we were talking about CO2, then the forcing would be spatially uniform, almost entirely so in fact. But Milankovitch “forcing” varies strongly with latitude and season. Indeed, there is a reversal of many of the effects in the Southern Hemisphere. From an energy balance point of view of an Earth which is just a watery rock ball, Milankovitch being a global forcing is nonsense. Fortunately the real Earth has all kinds of asymmetries of terrain, it has oceans and continents, ice sheets deserts and forests all over the place. But crucially, there is also heat transport from one location to another, and with Milankovitch, differential solar heating of the atmosphere/ ocean system by latitude/season changes from it’s normal behavior. So the atmospheric and ocean circulations also change. This in turn might cause changes in cloudiness, which, well, you’ve been reading this site, right? But it turns out, also, that if the equator to pole heat transport is altered, and a strong negative feedback occurs in the tropics, tightly constraining them, then a large change in mean temperature can occur from that irregular forcing, even if it’s TOA average was small (Lindzen and Pan, 1994). Also, no one, to my knowledge, has seriously questioned the idea of a positive ice albedo feedback, which would further amplify such changes in the high latitudes. That’s how, I think, you can get these large changes with low sensitivity.
yes, ice albedo feedback is positive…but it never has a chance to occur if strong negative feedbacks in the atmosphere prevent warming. Remember, also, a good part of the energy at the poles is transported there from lower latitudes.
It is not easy to read your paper. If you want a lot of people to read it, have somebody rewrite it to make it easier to read. The Resilient Earth guys would do a great job of this and I’m sure they would be thrilled to work with you.
I am reading your conclusions and find that much easier to read.
yes, the JGR paper will be comfortable only to a subset of engineers and scientists. That’s why I wrote The Great Global Warming Blunder…to explain it in lay terms. This paper is the science meat behind the book.
Roy,
Have you seen Michael D. Lemonick’s article over at Yale Environment 360?
“The Effect of Clouds on Climate:
A Key Mystery for Researchers”
“As climate scientists wrestle with the complexities of how the planet will react to rising greenhouse-gas levels, no variable is more difficult to decipher than the impact of clouds. But thanks to new satellite data and other technologies, clues are emerging that may help solve the puzzle.”
Full article:
http://e360.yale.edu/feature/the_effect_of_clouds_on_climate_a_key_mystery_for_researchers/2313/
… Apologies if this has been posted here before. DP
Disregard my previous comment.
I see that you addressed the Yale 360 article in your response called:
“The Persistence of Paradigms”
“ice albedo feedback is positive…but it never has a chance to occur if strong negative feedbacks in the atmosphere prevent warming.”
Yes.
If insolation increase in the NH melts the ice during deglaciation, then the global heating from decreased albedo should be minimal. Yet temperatures in the Antarctic increase by ~10C, much the same as the Northern high latitudes and at virtually the same time. I’m not sure how this can work with a low climate sensitivity.
“Speaking for myself, I suspect that climate sensitivity itself varies depending on the forcings involved and the dominant climate state (ie ice age or temperate).”
A low climate sensitivity (strong negative feed backs) works equally for cooling as well as heating. Moderate temps like the Holocene have occurred periodically in the late quaternary, yet the globe has cooled as much as it has warmed (5 – 6C). The starting conditions don’t seem to be the issue here.
I’d agree that climate sensitivity would be different at further extremes, or if the global landmass configuration was very different as it was millions of years ago.
Explaining the lack of correlation between forcing and SST is easy: heat capacity of water. Because of the heat capacity the two are not supposed to correlate. The correlation is between forcing and SST change, or between the integral of the forcing and SST if you like.
Or, since I don’t have your data, between forcing (the SW from that other post) and the derivative of SST: http://virakkraft.com/SW-SST-deriv.png
+1 W SW to the surface for 1 month gives appr. +0.05 C SST
Dr Spencer,
Thinking about your phase diagrams, it seems to me that the apparent sensitivity would depend on the statistics of cloud coverage at a given latitude. For example, if c is cloudy and S is sunny, a
ccccccccSSSSSSSSccccccccccSSSSSSSSScccccccccccc
long stretch latitude (LS latitude)
would have different statistics from a SS latitude like
ccSSccSccccSSSccccSSSScccSSSSccc
and furthermore LS latitudes with S predominant would differ from LS latitudes where c predominates.
The response of surface temperature to a step change in insolation would be exponential; a sigmoid function, responding slowly at first, then more rapidly, then slowly again as a new equilibrium is approached. So apparent sensitivity might depend on what portion of the sigmoid curve is effective given the statistics at the latitude (or season, etc.) in question.
FWIW
barry says:
‘A low climate sensitivity (strong negative feed backs) works equally for cooling as well as heating. Moderate temps like the Holocene have occurred periodically in the late quaternary, yet the globe has cooled as much as it has warmed (5 – 6C). The starting conditions don’t seem to be the issue here.’
So, we have reduced insolation at 65N for centuries. NH ice sheets extend into lower latitudes. Albedo rises, OHC falls,synergies deepen between feedbacks, ice age results. This isn’t just a nudge that tips an unstable climate into a new equilibrium; it’s a long process that eventually crosses a threshold that triggers massive change.
Then something (perhaps simply increased polar summer insolation; perhaps something else) happens, and reverses the whole process. A thousand years of solar forcing plus global cloud albedo change plus who knows what else might be enough to start a cascade of ICE-RELATED feedbacks that trigger massive deglaciation and abrupt warming.
Remember, if Milankovitch was right, although the changes in insolation are small, they go on for a long time. Even a relatively low climate sensitivity could eventually be overwhelmed by powerful ice-related positive feedbacks (primarily albedo increase) once the ice sheets have extended far enough south.
Is there a clear, demonstrable link (as you assume) between these dynamics of climate sensitivity to NH ice sheet extent, and the processes described in S&B 2010?
I’m not sure that there is. And I’m not sure that it’s safe to state that ‘the starting conditions don’t seem to be the issue here’.
Dominic
Dominic, the point is that strong negative feed backs should tightly restrict any process that leads to massive changes in the ice (unless underwater volcanoes erupt en masse every 100k years or so). The ice does not melt of it own volition.
“Remember, if Milankovitch was right, although the changes in insolation are small, they go on for a long time.”
Then the feed backs are strong but slow-moving.
“…plus who knows what else might be enough to start a cascade of ICE-RELATED feedbacks that trigger massive deglaciation and abrupt warming”
As Dr Spencer said just above, ice-albedo changes should not produce large effects if feed backs are strongly negative. You seem to be advancing the notion that positive feed backs are not required to explain ice ages transitions, while at the same time suggesting potential but unknown positive feed backs that somehow operate independently of the atmosphere (and therefore independently of Dr Spencer’s model) can produce major change.
I’m not sure if you’re exploring my query with me or trying to defend something. I’m here with questions.
Barry says:
You seem to be advancing the notion that positive feed backs are not required to explain ice ages transitions, while at the same time suggesting potential but unknown positive feed backs that somehow operate independently of the atmosphere (and therefore independently of Dr Spencer’s model) can produce major change.’
Sorry Barry. Not playing. You have either not read my previous comments carefully, or you are deliberately distorting what I have said.
Barry says:
‘I’m not sure if you’re exploring my query with me or trying to defend something. I’m here with questions.’
Disingenuous.
Barry, you do not mention the points set out by Andrew (above at Sept 03, 10:41am).
Please also read that comment again carefully. Andrew explains in better detail than I have what is at issue here.
For the record, I’m not actually at all clear why Dr Spencer made the response to Andrew’s comment that he did.
Dominic
I want to clarify something: I specifically meant to suggest that the feedbacks would be latitude dependent, in that, for one thing, Ice Albedo feedback is highly localized to the margin of the polar sea ice. If the tropical half of the world sees negligible change, and the extratropics see large changes, the global change is half that. So I meant to say that I think that the suppression of changes by feedbacks is great in the tropics, and diminishes toward the poles. Incidentally, because the great differences in insolation with latitude, I would expect that the magnitude of cloud and ice albedo feedbacks would vary greatly with the latitude at which they occur. For that, and another reason, I do not think that Barry’s suggestion, if I understand it, that feedbacks should linearly interact with temperature regardless of the inital state of the climate, can possibly be correct. The other reason is that, in sufficiently “extreme” climate states, certain feedbacks totally cease to be relevant. If all the ice were melted by the planet getting sufficiently warm, there would be no further ice albedo feedback toward warming, only in the other direct. In a Snowball Earth, there would be no further ice albedo feedback toward cooling, as all the water is already ice. So I think that the ice albedo feedback is very important when going from a state of a lot of ice to a warmer climate, and from a climate with little ice to one that is cooler, but in the case of AGW, we are already a planet with relatively little ice, as this is already an interglacial. So initial conditions and the direction of change, considered together, do, I think, matter.
Hello, I have two comments.
First, I must admit an issue of mine with the differences in presentation between your website and that of NASA-Goddard when it comes to disseminating information and figures. This is because I warm to websites presenting the information in a context that is professional, relevant (sensu stricto) and formal, given that I think this is a serious debate. Whereas I am mindful that yours is a blog, with the intention of taking liberties to be informal, it is nonetheless a little jarring when comparing numbers from NASA and then to your site to note this contrast. That you attended an awards ceremony is one thing, but the details of it and references to other attendees such as Ann Coulter (an expert on climate I’m sure) are a little excessive.
There is a way to present your case, and make it simple and transparent, without trying to give me the impression that you are doing something on the line of trying to bring Christians into the fold by having a party serving Sangria. And that leads to my Second. Your work on cloud feedback is a very good reason to reconsider the IPCC standard on climate change, and it is something to become familiar with and watch closely, the one area my skepticism has not wavered from. Wikipedia is very much on their side when explaining this, so it is remarkable that they haven’t pilloried your work on this–yet. The fourth paragraph under “Climate Change research” under your entry provides a ready summary of what you have done, unless you find it inaccurate. I did not write it.