How do you 'counter' something that is true? By making false claims, I suppose.

Comments in the latter part of this thread demonstrate that the rate of warming in the second half of the C20th was higher than in the first. It has *accelerated*.

Perhaps the most convincing and uncontroversial demonstration comes last - 3rd order polynomial fits (curved, not linear, trends) to:

BEST

GISTEMP

NOAA global

HADCRUT4

The false claim being made here is by Shub, who can only get the misleading result he 'likes' by using HADCRUT3. A now obsolete data set noted for showing less warming that all other GAT reconstructions.

The four examples above demonstrate that this is a false claim:

The rate of warming has not accelerated over the course of the C20th

If Shub wishes to continue to dispute this he will need to *demonstrate* that he is correct and everybody else is wrong.

*Demonstrate* means 'show by example'. It is not sufficient simply to repeat debunked claims endlessly.

That simply underlines the fact that you have lost the debate.

Martin A

Given a time series but lacking a model for what generated it, you can draw pretty much whatever conclusions you want, depending on what model you dream up (or which you don't even consciously dream up but is implicit in your arguments).

The increase in radiative forcing from the rising fraction of atmospheric CO2 has been exhaustively calculated. When this is used to force ensembles of climate models, they reproduce the general shape of C20th climate change. When it is removed, they do not. This is the iconic example from WG4.

What we do not have is *any evidence* that other, non-GHG forcings or natural variation are substantially responsible for modern warming. The parsimonious explanation is that the principal driver is CO2.

So it is deeply misleading to claim that we do not have a framework for interpreting observations. The 'we don't know - we can't know' meme is a dead 'un and I'm disappointed to see you drag its carcass onto the stage here.

Martin, I think the climate may be chaotic in detail, but the energy balance can't be - ultimately it is subject to the laws of thermodynamics. But energy can be stored, in the phase changes of water, in the varying volume of warm (or less cold) deep water currents, in the potential energy of ice at high altitude, in the kinetic energy of water currents... Compared to a GHG forcing of 2W/m2 the amounts of energy are very significant. The observed periodicities are suggestive.

The Hansen position is that observed warming over 1970 - 2000 must be due to GHG's, so that enables sensitivity to be calculated, and any downward kinks in the curve are attributed to volcanic events, e.g. Agung. (Of course the Agung eruption came towards the end of the mid-century cooling, but never mind. That still leaves the Great Climate Shift unexplained in Hansen's view - he thinks it doesn't affect the argument, nor in general do periodic fluctuations, even though they are unexplained: "It is likely that the fluctuations are dynamical." (Hansen 2002))

The Spencer position is that cloud feedbacks (or *forcings*) and the PDO account for the general changes in climate, in particular for the 1970 - 2000 warming (or most of it) and that cloud feedbacks guarantee that CAGW will not happen.

In between is a spectrum of views, from climate scientists who accept warming but do not endorse Hansen's extremism to Syun-Ichi Akasofu, who is convinced of the periodicities (as a fairly complete account of the temperature history) but are not committed to a particular mechanism. Akasofu has been strongly criticised on the grounds that he has no physical mechanism, and BBD and BitBucket use the same line here - no physical mechanism? then you haven't got a theory. That is against the grain of scientific history. Newton's Law of Universal Gravitation existed for centuries before Einstein's General Relativity (and we are still waiting for a quantum theory of gravity a hundred years on). Mendel's laws existed long before meiosis was understood, or chromosomes and genes even thought of. Kirchoff's Law, Ohm's Law... Basically, all laws in hard science begin as observations of numerical patterns, and the laws are important in elucidating the mechanism which comes later, maybe centuries later. Kepler's conclusion that Tycho Brahe's data on planetary motions were best explained by elliptical orbits with the Sun at one focus was a key starting point for Newton.

BOFA

Perhaps it would be a good idea to review the last dozen or so comments - at the very least - before saying more.

logico

The Spencer position is that cloud feedbacks (or *forcings*) and the PDO account for the general changes in climate, in particular for the 1970 - 2000 warming (or most of it) and that cloud feedbacks guarantee that CAGW will not happen.

The contradictory nature of the belief in a low climate sensitivity was discussed upthread (eg my response to you @ May 27, 2012 at 6:03 PM). It would be very helpful if you were to review comments so we can avoid repetition.

But since you bring it up, a quick recap: low sensitivity is incompatible with observed climate variability in response to minor changes in forcing. There would have been no MWP, no LIA and most importantly, it would not be possible for orbital (Milankovitch) forcing to cause the onset of deglaciations. That's how we know Spencer and Lindzen are wrong.

Unsurprisingly, neither has published anything supporting their views on low CS which has withstood scrutiny. As a consequence, both are professionally isolated by their failure to make a case.

Anyone interested in understanding just how badly flawed Spencer's PDO/cloud/climate claim is can follow it up here. It's a long and detailed article but ably summarised by this quote:

The take-home message here is that Spencer’s curve-fitting enterprise could (and did!) give him essentially any answer he wanted, as long as he didn’t mind using parameters that don’t make any physical sense.

Finally, what you personalise as 'Hansen's view' is actually the standard scientific position arising from a global and interdisciplinary scientific consensus.

BOFA

Perhaps it would be a good idea to review the last dozen or so comments - at the very least - before saying more.

May 29, 2012 at 1:28 PM | BBD

I will post what I like when I like as long as it is within the Blog rules, if you want to dictate what gets posted setup your own blog.

Fine. Cut and paste material that is irrelevant to the present state of the conversation. I will ignore it.

BBD:

" 'The Spencer position is that cloud feedbacks (or *forcings*) and the PDO account for the general changes in climate, in particular for the 1970 - 2000 warming (or most of it) and that cloud feedbacks guarantee that CAGW will not happen.' The contradictory nature of the belief in a low climate sensitivity was discussed upthread (eg my response to you @ May 27, 2012 at 6:03 PM). It would be very helpful if you were to review comments so we can avoid repetition." Actually, it would be both helpful and polite if you were to read my response addressed to you on may 28 at 12:32 AM. It would have rendered your next paragraph redundant. [To wit: "But since you bring it up, a quick recap: low sensitivity is incompatible with observed climate variability in response to minor changes in forcing. There would have been no MWP, no LIA and most importantly, it would not be possible for orbital (Milankovitch) forcing to cause the onset of deglaciations. That's how we know Spencer and Lindzen are wrong."]

"Anyone interested in understanding just how badly flawed Spencer's PDO/cloud/climate claim is can follow it up..." No doubt - but since I mentioned him as holding an extreme view which I do not share, so what? I do believe that the net feedbacks from water in its various phases are negative, otherwise the Earth would probably be a dead planet.

My own view is less extreme than Akasofu's. I don't expect cyclical variations to account for every detail of the temperature record, and I fully expect that fossil fuel CO2 emissions will have a detectable effect on temperatures. The line you take seems to be the IPCC's - i.e. the politicised Summary for Policy Makers. Peter Taylor expresses this well: "As we shall see, the signal of [anthropogenic] global warming - whether it stands out from normal variability - has always been uncertain. Between IPCC's 2001 Assessment Report and that in 2007, confidence that there was a real signal increased from 90% to 95%. However, the Panel were only agreeing the nature of the signal, not its cause, and they actually narrowed the period over which the signal could be regarded as unusual. When it comes to considering causes (the Summary report talks naively of natural OR human rather than the reality of multiplicity), the 2001 assessment left a large probability of 33% that the cause was natural." We could add that the 2001 Report predicted an accelerating rise in temperature which the planet has spectacularly failed to deliver; in the real (as opposed to modelled) sciences a failed prediction is reckoned to invalidate a theory, but IPCC continue to suggest that the theory is MORE strongly supported by the evidence... However, the point is that I and many other sceptics believe that some AGW is inevitable, but there is also a clear natural signal, with natural causes. Quoting Taylor again, "It is very obvious that they are cyclic in nature, yet these cycles are all but ignored in the interests of a simple message."

"Finally, what you personalise as 'Hansen's view' is actually the standard scientific position arising from a global and interdisciplinary scientific consensus." Hansen is a rabid fanatic. This is from a well circulated New York Times article, quoting JH:

"Canada’s tar sands, deposits of sand saturated with bitumen, contain twice the amount of carbon dioxide emitted by global oil use in our entire history. If we were to fully exploit this new oil source, and continue to burn our conventional oil, gas and coal supplies, concentrations of carbon dioxide in the atmosphere eventually would reach levels higher than in the Pliocene era, more than 2.5 million years ago, when sea level was at least 50 feet higher than it is now. That level of heat-trapping gases would assure that the disintegration of the ice sheets would accelerate out of control. Sea levels would rise and destroy coastal cities. Global temperatures would become intolerable. Twenty to 50 percent of the planet’s species would be driven to extinction. Civilization would be at risk." And again: "We can say with high confidence that the recent heat waves in Texas and Russia, and the one in Europe in 2003, which killed tens of thousands, were not natural events — they were caused by human-induced climate change."We have known since the 1800s that carbon dioxide traps heat in the atmosphere. The right amount keeps the climate conducive to human life. But add too much, as we are doing now, and temperatures will inevitably rise too high. This is not the result of natural variability, as some argue. The earth is currently in the part of its long-term orbit cycle where temperatures would normally be cooling." I don't think you would find another scientist of note who would agree with half of those statements; and h has made many more, equally extreme.

The issue of curve-fitting is also interesting. The link you gave a couple of posts back to show that CO2 accounts for the temperature record in the 20th century gives a graphic originating, I think, with Hansen. The nice upward curve is kinked by volcanic events. The most significant deviation is the midcentury cooling, from the mid-40's to the mid-70's, the one which caused so many scientists and ecologists to predict a coming ice age. I was born in the bitter winter of 1947, and I well remember the extremely severe winter of 1962. Hansen links this to the eruption of Mt Agung, in 1963. The more notable eruptions of Mt St Helen's in 1980 coupled with El Cichon in 1982, and the even more spectacular conjunction of Pinatubo and Mt Hudson in 1991, caused relatively minor blips. There is no convenient eruption to explain the 21st century divergence from the IPCC prophecy. Conversely, the major paired eruptions of 1912 (Novarupta - biggest of the century) and 1913 (Colima) are linked with no significant cooling; nor are the 1932 (Cerro Azul) and 1933 (Kharimkotan) - they are just ignored. If you can just chuck away inconvenient data, curve-fitting is a breeze.

logico...there was an interesting post on WUWT by Willis a month or so ago, trying to find the evidence of the "year without a summer" - 1812 0r 13. the recorded facts do not suggest that temperatures were abnormally low during those years, despite the anecdotal evidence of the lack of Summer warming. The serious point is that there were supposedly major volcanic eruptions then...and they had no effect on the climate. which kind of suggests that volcanic activity does not really matter for the climate.

waits for BBD to cite 30 academic papers.

logico

From your May 28, 2012 at 12:32 AM

One answer is that MWP, LIA etc might indeed have been much *more* pronounced without the negative feedback = low sensitivity. That's an experiment we can't perform. (Personally I have never believed in the Milankovitch theory, which seems to rely on an inadequate but convenient cause. I also think there's considerable recent doubt about the fit of orbital cycles to the glacial series.) Another answer, given already in my previous post, is that with positive feedbacks the earth would quite probably have drifted long ago to a completely frozen state or, conversely, a torrid desert.

This is inherently contradictory. If negative feedbacks lower CS and muted the MWP/LIA, then
how does a *very small change* in orbital forcing initiate a deglaciation? Your doubts about Milankovitch theory are noted, but do not constitute an argument. What we need is a well-supported counter hypothesis and it is lacking.

There have been Snowball Earth events, see
here and there have been Hothouse climates eg Eocene 55Ma. It's worth remembering in passing how the climate got itself out of an albedo-locked icehouse. The generally accepted hypothesis is that a combination of volcanism and hugely reduced natural carbon sinks (frozen ocean surface; very low biological activity) caused CO2 build-up and an increasingly radiative atmosphere initiated melting. Once the ice-albedo feedback reversed, the process accelerated. The more you look at paleoclimate the more positive feedbacks you see.

But... there's never been a runaway greenhouse because the climate system ultimately self-
limits. When you think of feedback the standard model is an amplifier with its output fed back into its input. The loop amplifies until it saturates (reaches the limits of the system).

Climate feedbacks are different. The increase in output is *not* proportional to the increase in input. It is less than the increase in input so over time the response attenuates rather than amplifies to saturation.

I do believe that the net feedbacks from water in its various phases are negative,
otherwise the Earth would probably be a dead planet.

What you say is very puzzling. Look at ice and at water vapour. Ice-albedo feedback is strongly positive: large ice sheet = more reflected DSW = cooling. Small ice sheet = more absorption of DSW = warming. Water vapour feedback is strongly positive because tropospheric WV absorbs and re-radiates OLR but is largely transparent to DSW. Surely you've read that WV is an important contributor to the terrestrial GHE? Forcings operating on the global ocean ultimately determine the size of ice sheets and the amount of atmospheric WV - so however you look at it, water is a source of positive feedbacks. (Remember: there's a lot more to atmospheric WV than just clouds, and that clouds are likely weakly positive or neutral feedbacks as they reflect above but trap below).

Very briefly, I think Hansen would have done better to state that at the very point when we
should be moving rapidly away from dependency on fossil fuels, gearing up to exploit unconventional deposits is a definitive step in the wrong direction.

As for the heatwaves, Hansen has just demonstrated the reality of this claim empirically. See Hansen et al. (2012) Public Perception of Climate Change and the New Climate Dice:

We show that the odds of an unusually warm season have increased greatly over the past three decades, but also the shape of the frequency distribution has changed so as to enhance the likelihood of extreme events. A new category of hot summertime outliers, more than three standard deviations (3σ) warmer than climatology, has emerged, with the occurrence of these outliers having increased 1-2 orders of magnitude in the past three decades. Thus we can state with a high degree of confidence that extreme summers, such as those in Texas and Oklahoma in 2011 and Moscow in 2010, are a consequence of global warming, because global warming has dramatically increased their likelihood of occurrence.

There's a useful discussion of this finding here. Hansen's not a 'rabid fanatic'. He just knows more about this than most of us and it's making him anxious. As well it might.

The link you gave a couple of posts back to show that CO2 accounts for the temperature record in the 20th century gives a graphic originating, I think, with Hansen.

Nope. Read the caption (these are model ensembles btw. Nothing to do with 'curve fitting').

I've dealt with the misrepresentation of quasi-periodic oscillations already. It just doesn't work the way you claim. You might want to do a literature search on '60 year PDO cycle' or similar focussing only on the published scientific literature. The results are going to
surprise you. Even Bob Tisdale, a sceptic to his toes, is having none of it.

If you can just chuck away inconvenient data, curve-fitting is a breeze.

First, we're still not talking about curve fitting. Second, *you* can't just make sweeping statements like this. Low latitude eruptions have different effects to high latitude eruptions. The altitude reached by the sulphate aerosol cloud is also a key factor. The amount of sulphates produced during the eruption is another. Your claim is baseless.

That's it - out of time! Back to work.

Please reassure Mrs Shub that I don't need the money and this is entirely pro bono. Do note, however, that I find your bringing this up here offensive but entirely in tune with your usual character assassination tactics. I am reminded, forcefully, that when you have nothing else, flinging ordure is all that is left.

Neither of your most recent comments addresses anything concrete in my last, so I shall ignore them both.

Best of luck.

Anybody

Why is the following correct and uncontentious statement by Hansen a 'wholesale laundering of ignorance', 'worse than creationism' and 'disgusting'?

Natural ecosystems are adapted to the stable climate of the Holocene.

Should natural ecosystems perhaps be adapted to the Eocene? Or the conditions of equatorial Mars?

BBD.

Thank you for a very detailed response.

You counter my "MWP, LIA etc might indeed have been much *more* pronounced without... negative feedback..." by writing that feedbacks must be large or the very small Milankovitch effect could not cause recent glaciations. "This is inherently contradictory... Your doubts about Milankovitch theory are noted, but do not constitute an argument. What we need is a well-supported counter hypothesis and it is lacking." That's not logical. The Milankovitch theory is dubious for various reasons - dubious matching of dates and inability to explain rapid climate transitions are obvious, and perhaps low latitude glaciation. (It used to be argued that the process implies alternate NH and SH glacials, which contradicted the evidence; I'm not up-to-date on that, so I can't really comment.) Problems with the Milankovitch theory imply that there are other causes. Personally I have zero expertise, so I don't endorse any theory, merely noting that there have been many, from Cosmic Winters to solar variations; as you'll see in a previous post, I am attracted to the idea that there is considerable internal fluctuation involving energy stored in the climatic system (and the tectonic system).

"There have been Snowball Earth events..." long, long ago - not too relevant now, perhaps, but interesting of course.

"Climate feedbacks [positive ones] are different. The increase in output is *not* proportional to the increase in input. It is less than the increase in input so over time the response attenuates rather than amplifies to saturation." That's right, the earth eventually reaches a new balance with the same radiation output in the models, but not before Hansen's Apocalypse. But the models do not allow that increased evaporation may have large negative feedback effects. Even a small increase in the amount of condensation higher in the atmosphere would greatly increase the radiation escaping; and then there are clouds... The crucial water vapour feedbacks are "poorly understood" according to IPCC.

" 'I do believe that the net feedbacks from water in its various phases are negative,
otherwise the Earth would probably be a dead planet.' What you say is very puzzling. Water vapour feedback is strongly positive because tropospheric WV absorbs and re-radiates OLR but is largely transparent to DSW. Surely you've read that WV is an important contributor to the terrestrial GHE?" Indeed I have. And surely you've read that the convection-condensation or evapotranspiration mechanism is a massive negative feedback, preventing a runaway greenhouse effect - how is it affected by global warming?

"Very briefly, I think Hansen would have done better to state that at the very point when we
should be moving rapidly away from dependency on fossil fuels, gearing up to exploit unconventional deposits is a definitive step in the wrong direction." But the question is: HOW WRONG? Hansen suggests that the climate will be wrecked, billions of people and millions of species are at risk...

"As for the heatwaves, Hansen has just demonstrated the reality of this claim empirically. See Hansen et al. (2012)" Thanks. I downloaded this. I haven't read it yet, but I was expecting to find Hansen's explanation of how AGW impacts on blocking highs and the jet stream. So I did a search in this paper for "blocking high" - no result. "Jet stream"? No result.

"'The link you gave a couple of posts back to show that CO2 accounts for the temperature record in the 20th century gives a graphic originating, I think, with Hansen.' Nope. Read the caption..." Thank you. I only thought it - it doesn't affect the discussion.

"I've dealt with the misrepresentation of quasi-periodic oscillations already. It just doesn't work the way you claim. You might want to do a literature search on '60 year PDO cycle'..." But I don't claim any mechanism nor any close periodicity. All I claim is that there are apparently cyclical variations in temperature/climate on all scales from a day to perhaps 250My. They won't be exact periodicities, and even if they were, their interactions would no doubt be hard to disentangle. That's what this whole discussion is about. You wrote that the climate is not a bouncing ball, but many processes in the climate are just that: colloquially, "What goes up must come down." I can imagine the IPCC faithful looking at a guitar string or a pendulum and trying to assign some "external forcing" to account for its movement, now to the left, now to the right. (That's just an analogy - you don't need to tell me that Mann or Hansen or whoever wrote a paper on SHM.)

"If you can just chuck away inconvenient data, curve-fitting is a breeze... Low latitude eruptions have different effects to high latitude eruptions. The altitude reached by the sulphate aerosol cloud is also a key factor. The amount of sulphates produced during the eruption is another. Your claim is baseless." Point taken - but will you take my point. Agung was reassessed by modern analysis of ground observations (as I'm sure you knew) - specifically, it appears (roughly = "I think"), to stick a volcano in the midcentury cooling. To me, that is some sort of curve-fitting. But it's in the wrong place on the curve.

Really, the "inconvenient data chucked away" is the cooling itself, 30 or 40 years' worth; and you have done it, too. You gave 4 curves (May 25, 9:45 AM) to prove that warming had accelerated in the late 20th century. That was achieved by ignoring the midcentury cooling. Here is another analogy: I drive 50 miles down the motorway before leaving it (40 minutes); I stop at the services to fill my tank with fossil fuel and eat a burger (another 40 minutes); I drive another 80 miles along winding country roads to visit my old mum (120 minutes); I do a third order polynomial thingy to give a best fit curve to my speed for the journey, and discover that I actually accelerated during the latter part...

To summarise:

Looking back at the climate record, recent, medium and long term, I see a lot of variability. I don't see any particular "forcings" operating at every stage, and I'm rather tempted to compare (for example) the "rebounding" temperatures after cooling events with the isostatic recovery of the once-glaciated land. I don't look for exact periodicities, but I do think there are cyclical processes at work. I'm not stupid - I've done my physics - and I expect some minor extra warming due to additional anthropogenic CO2; but I absolutely refuse to believe that at some magic moment natural variability stopped, and AGW took over. If you look around, you'll find scientists like Akasofu who wait until they have retired before they express the same view. Why is that:

The IPCC faithful, on the other hand, think that every change is freshly forced. It's an honest view - though it's rather obvious that the Green Religion has made industry ( whether fossil- or nuclear-fuelled) as its Original Sin; carbon cutbacks, taxes, etc are the new self-flagellation; and the pronouncements of IPCC and Saint Jim Hansen are the new Bible. Heretics will be burned at the academic stake, or at least tortured by the academic Inquisition... (This is paralleled by the materialism of Soviet Russia, which similarly pressurised scientists into dubious positions, and believed that world government and universal

I don't expect you to see it that way, or even to understand that the new materialism has left a moral vacuum that apparently needs to be filled. But here is one mre analogy. When I was a nipper, TV often had variety shows. One of the standard turns was the juggler, and often he or perhaps she would spin plates. Each plate was placed on top of a fixed cane, which was set vibrating in a circular pattern. If the cane lost too much energy, the plate would fall. It looked amazing when the juggler had a dozen, maybe a score, of plates spinning; but I was just a kid, and didn't understand gyroscopes. I think that Jim Hansen and his disciples believe that the climate must be continually "forced" to stay where it is. On the other hand, the climate has done pretty well without planned "forcing". Maybe it's more like a lot of gyroscopes, or pendulums. Past (non-catastophic) variation supports that view.

[Please excuse any errors of spelling or grammar or courstesy. I have imbibed a nice bottle of CNDP as I typed this. lAso the on-screen keyboard on my iPad is not vino-friendly.]

CNDP?

Gotit. "New castle of the pope"

Logico

You might want to open another bottle. This will take some time :-)

That's not logical. The Milankovitch theory is dubious for various reasons - dubious matching of dates and inability to explain rapid climate transitions are obvious, and perhaps low latitude glaciation.

Milankovitch theory (not hypothesis, note) is routinely misunderstood. The problem is that people (including myself) tend to talk about the '100ka cycle' when there is in fact no such thing. The variables are eccentricity (~100ka period), obliquity (~41ka period) and precession (~26ka period). The 100ka eccentricity period *is itself* variable over a ~400ka period. The head-exploding combination of these four variables is that eccentricity modulates and amplifies the effects of obliquity and precession and does so differently over time. The complex and shifting interplay results in the 82 - 123ka range of spacing between late Pleistocene interglacial peaks.

Now is a good time to go back to your May 23, 2012 at 4:40 PM on the questions raised by Archer and the role played by CO2 as a feedback to Milankovitch forcing. I've expanded your original quote from Archer p77 (emphasis added):

...in the clearest climate transitions, which are the deglaciations, CO2 goes up before the ice sheets melt. How can CO2 be some kind of me-too amplifier if it starts to change first? [Archer continues:] It's a vexing mystery, all right. I envision the ice sheets and the CO2 intertwined in a feedback loop of cause and effect, like two figure skaters twirling and throwing each other around on the rink. It would be very confusing to try to analyze the physics of the trajectory of either skater without considering the other.

The key may well be changes in ocean circulation and so heat transport triggered by NH Milankovitch forcing right at the end of the LGM (21.5 - 19ka). This is what the much-misrepresented Shakun et al. (2012) study is all about. There's a good discussion at RC here.

Teaser:

The last deglaciation occurred as a long process between peak glacial conditions (from ~26-20,000 years ago) to the Holocene (~10,000 years ago). Explaining this evolution is not trivial. Variations in the orbit cause opposite changes in the intensity of solar radiation during the summer between the Northern and Southern hemisphere, yet ice age terminations seem synchronous between hemispheres. This could be explained by the role of the greenhouse gas CO2, which varies in abundance in the atmosphere in sync with the glacial cycles and thus acts as a “globaliser” of glacial cycles, as it is well-mixed throughout the atmosphere. However, if CO2 plays this role it is surprising that climatic proxies indicate that Antarctica seems to have warmed prior to the Northern Hemisphere, yet glacial cycles follow in phase with Northern insolation (“INcoming SOLar radiATION”) patterns, raising questions as to what communication mechanism links the hemispheres.

It's an interesting half-bottle article on a paleoclimate puzzle - enjoy :-)

Logico

Personally I have zero expertise, so I don't endorse any theory, merely noting that there have been many, from Cosmic Winters to solar variations; as you'll see in a previous post, I am attracted to the idea that there is considerable internal fluctuation involving energy stored in the climatic system (and the tectonic system).

You mention various unsupported hypotheses, to which I can only say: Occam! And then quietly remind that Milankovitch is now accorded the status of theory.

I wonder about the mechanism for an internal fluctuation involving energy stored in the climate system. Consider the period between the Eemian and Holocene: ~100ka of cooling culminating in the LGM. Positive ice albedo feedback increasing. Land surface temperature falling, SSTs falling, deep ocean temperatures falling.

How (and where) does the climate system *store energy* over this period of demonstrable energetic depletion (aka 'cooling' and 'ice age')? And even if it could (which I must say I sincerely doubt), what prompts the sudden emergence of this hypothetically stored energy after 100ka of hiding away in the depths?

One final physics check: if the energy was stored in the deep ocean, which is the only possible reservoir, why does the deep ocean not *cool* during the onset of deglaciation?

But the models do not allow that increased evaporation may have large negative feedback effects.

Reference?

Even a small increase in the amount of condensation higher in the atmosphere would greatly increase the radiation escaping; and then there are clouds...

You have to be very careful with this. The impact of WV on radiative balance is greatest in the upper troposphere and the upper troposphere is moistening in line with modeled projections. Hence the positive water vapour feedback. There's a useful discussion of this
here, entitled How not to discuss the water vapour feedback...

BBD:

Just a first impression.

I wrote: "The Milankovitch theory is dubious for various reasons - dubious matching of dates and inability to explain rapid climate transitions are obvious, and perhaps low latitude glaciation." You firstly note that there are complex interactions of several orbital components (as Croll, Milankovitch...) leading to "complex and shifting interplay results in the 82 - 123ka range of spacing between late Pleistocene interglacial peaks." This seems to be a bit of an alibi for my reason 1, rather than a clear support of Milankovitch. For an expert contrary view on the timing issue (among others) see:

http://www.seas.harvard.edu/climate/pdf/wunsch_2004.pdf

Next you turn to my earlier criticism of Archer. You give this quote from his book:

"...in the clearest climate transitions, which are the deglaciations, CO2 goes up before the ice sheets melt. How can CO2 be some kind of me-too amplifier if it starts to change first? [Archer continues:] It's a vexing mystery, all right. I envision the ice sheets and the CO2 intertwined in a feedback loop of cause and effect, like two figure skaters twirling and throwing each other around on the rink. It would be very confusing to try to analyze the physics of the trajectory of either skater without considering the other." That entirely misses two points - the original point against Archer, that he considers melting rather than temperature change and this hides the fact that temp change leads CO2 change. I'm not generally outspoken, but he doesn't even hint at this, and I see that as bloody dishonest. (I've read IPCC WG1 thoroughly over the years, and I'm well aware that significant ice sheet melting may take a millennium or so after the temp upturn.) The second point is the swiftness of the deglaciations ("clear" = rapid). The Milankovitch effect is an imbalance of a few percent in solar heating of the two hemispheres, but the total insolation remains the same. How could such a tiny irregularity drive an ice age?

Only by eyewateringly humongous feedback, but is even that adequate? I mentioned a fourth Milankovitch problem, the fact that it ought to lead (and was originally believed to lead) to out of phase NH and SH glaciations. You mention CO2 as a feedback for deglaciation in your final chunk, but (as your text indicates) that is an hypothesis comlete with its own suicide note - if the unbalanced heat is redistributed, the Milankovitch forcing disappears.

You continue: "The key may well be changes in ocean circulation and so heat transport triggered by NH Milankovitch forcing..." But if it is merely a trigger in some unknown way (mechanism? not even a convincing hypothesis) and if the pattern of cycles is too complex/blurred to implicate it clearly, then how can you proudly trumpet its Theory status? The Wunsch paper (link above) identifies various ways in which the Milankovitch effect is dependent on unproven hypotheses.

Over 30 years ago a number of researchers suggested that though the mechanism is inadequate, nevertheless a Milankovitch signal modulating the details of the glaciation was perfectly possible: a detectable Milankovitch fingerprint does not prove that it caused glaciation any more than my text here proves that I invented the internet. Nevertheless, It's not inconceivable that the stochastic process described by Wunsch could take the climate system so close to a transition that a tiny trigger could influence the timing. Does that qua
ify it as a cause? In philosophical parlance, it isn't clear that itbis even an INUS condition.

You wrote: "The last deglaciation occurred as a long process between peak glacial conditions (from ~26-20,000 years ago) to the Holocene (~10,000 years ago)..." I think there is a cosy suggestion here of gradualism, which would suit Milankovitch and Archer, but is totally wrong. There were swift and drastic shifts in temperature.

Bottom line: I don't think that your defence of the Milankovitch effect cuts any ice - so to speak - BUT that was only a minor issue in my last posting. All the points I really wanted to make are unanswered. I understand that accepting the Milankovitch effect as The Cause of glaciation would - precisely because it is so inadequate - bolster the claim of high climate sensitivity, so I can see why you would want to go there. Ultimately it is at best peripheral, and I would rather be discussing (quoting my previous):

1) "Looking back at the climate record, recent, medium and long term, I see a lot of variability. I don't see any particular "forcings" operating at every stage, and I'm rather tempted to compare (for example) the "rebounding" temperatures after cooling events with the isostatic recovery of the once-glaciated land. I don't look for exact periodicities, but I do think there are cyclical processes at work. I'm not stupid - I've done my physics - and I expect some minor extra warming due to additional anthropogenic CO2; but I absolutely refuse to believe that at some magic moment natural variability stopped, and AGW took over." In particular, the failed IPCC 21st century projection for temperature change acceleration.

2) "If you look around, you'll find scientists like Akasofu who wait until they have retired before they express the same view. Why is that? The IPCC faithful, on the other hand, think that every change is freshly forced. It's an honest view - though it's rather obvious that the Green Religion has made industry ( whether fossil- or nuclear-fuelled) as its Original Sin; carbon cutbacks, taxes, etc are the new self-flagellation; and the pronouncements of IPCC and Saint Jim Hansen are the new Bible. Heretics will be burned at the academic stake, or at least tortured by the academic Inquisition..." For a further example, see:

http://www.physicsforums.com/archive/index.php/t-109844.html

- which, incidentally, addresses BitBucket's unfounded assertion that there was no global MWP evidence, and also various suggestions to the effect that if one has a better idea than Messrs Mann, Hansen and the rest, one has only to get it published in a peer reviewed journal. (Also, who would fund the research? And, perhaps reading Shaopeng Huang's mind in *1998*, who would fund your *next* piece of research...) Huang and Pollack's paper is a model of clarity - it's hard to imagine what sort of rewrite the editors envisaged.

http://www-personal.umich.edu/~shaopeng/97GL01846.pdf

Why do you never hear of this paper? In 1998 Huang *himself*, writing a followup study, didn't even cite his own 1997 paper. It's buried.

BBD:

I read the "How not to discuss..." link. The author mentions transport of latent heat as being irrelevant to radiative balance. If that is so, then I have been mistaken for most of my life. Bummer or what!

I always believed that around 80W/sqm of the reradiated 240-ish (ignoring the 100 or so simply reflected) was transported high into the atmosphere as the latent heat of water vapour. Once there, above most of the GHG's, it changes to ice crystals, releasing immense amounts of heat to be radiated away. That's 1/3 of all the surface heat bypassing the GHG trap. Even a small percentage change in such a large climate component would be important.

Comment?

Logico

I can imagine the IPCC faithful looking at a guitar string or a pendulum and trying to assign some "external forcing" to account for its movement, now to the left, now to the right.

This is unfortunately misleading.

- A pendulum swings both to the left and to the right because it is impelled by an external forcing (energy input). This may be a simple manual push, or the stored kinetic energy of a clock spring or weight.

- A guitar string oscillates because it has been plucked. Again the *whole oscillation* is a response to an external forcing (energy input).

The climate system responds to an external forcing (energy input) by heating up. It is huge and complex, and there's lots of minor internal variability, but over time, the general warming trend will emerge.

Really, the "inconvenient data chucked away" is the cooling itself, 30 or 40 years' worth; and you have done it, too. You gave 4 curves (May 25, 9:45 AM) to prove that warming had accelerated in the late 20th century. That was achieved by ignoring the midcentury cooling.

Not at all. The whole point of using a third order polynomial is that it *doesn't* 'chuck away' data. It is the best fit for the time-series as a whole. The slight mid-century cooling is revealed for what it is - a much less significant contributor to centennial climate change than the two warming periods. And the most recent warming is shown to have been more rapid than the 1910 - 1940 episode.

I know you don't mean to be offensive, but the one thing that does anger me particularly is any suggestion of graph-cooking. I leave that to others.