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Discussion > Feedbacks and Forcings

You can't read, can you? If your understanding of what is written here, of questions posed, of positions taken is so poor, then why would I trust you to read elsewhere with any prospect of success? And as for editorialising, I suppose that when it becomes too offensive his grace will be the one to warn me off.

Aug 14, 2012 at 5:54 PM | Registered Commenterrhoda

You are being ridiculous, again.

Aug 14, 2012 at 6:14 PM | Unregistered CommenterBBD

I'll stick with the mainstream scientific position that attribution for warming post-1950 is substantially anthropogenic.
"Mainstream" as in what and whom, exactly? Remember that the IPCC found no evidence that warming was "substantially anthropogenic" until Houghton and Santer got their dirty little fingers on the levers of power. That was just before it all blew up in their faces because it was found that CO2 is a lagging indicator of warming and not a cause — a point which you are determined not to address. So the "evidence" for what you call the "mainstream position" is sparse to say the least and any empirical evidence is non-existent.
I have seen *no evidence* that it could possibly be anything else - including natural variation.
And that's how we do science these days, is it? "I have seen no evidence that it could be anything else ..." How hard have you — or any other climate change enthusiast — actually looked for any?
I am still waiting for the evidence that it couldn't possibly be anything else. So that makes us equal.
And that's before we start on the concept of "mainstream" and "consensus" being the same thing as "right".
And you accuse rhoda of talking crap!

Aug 14, 2012 at 6:26 PM | Registered CommenterMike Jackson

Mike

That was just before it all blew up in their faces because it was found that CO2 is a lagging indicator of warming and not a cause — a point which you are determined not to address.

I've addressed this point repeatedly in comments in Discussion. As you would know if you took the trouble to read what I say, for example to you, directly, on Aug 7, 2012 at 9:05 PM.

I thought we'd sorted this out :-)

The CO2-warming lag during deglacials doesn't 'falsify' anything. CO2 is a feedback to the initial orbital forcing. Hence the lag. Its effect is to amplify the initial forcing (it's a positive feedback) which makes CO2 a necessary part of the process that leads from orbital forcing to interglacial. The process itself is a demonstration that feedbacks net positive.

One of the interesting things about orbitally forced deglaciation is that the total amount of solar energy reaching the earth's surface is barely increased. Yet it's enough to end an ice age. It's the *regional and seasonal* effect that triggers melting of the NH ice sheet which gets the feedback ball rolling. Just increased summer insolation at high Northern latitudes. How could this end an ice age unless feedbacks net positive?

Put another way, how can an insensitive climate system dominated by negative feedbacks behave like earth's climate system under these circumstances?

This is one of the many non-joys of 'debating' with 'sceptics'. You explain stuff, and five minutes later the same old crap comes round on the carousel again. Ad infinitum. Ad nauseam. And

Now do you understand this point, finally? Nobody argues that CO2 terminated glacials. That is a straw man. During deglaciation, CO2 is treated as a *feedback* to the initial orbital forcing. A feedback. Okay? So it *lags* the original forcing. Okay?

So the 'sceptic' argument about CO2 lagging T during deglaciation 'falsifying AGW' is a perversion of the actual scientific perspective. Aka complete crap.

Sorry Mike, but as for the rest of the tripe about 'Santer is evil' and 'what is the scientific mainstream?' and 'have they looked for anything else?' - it's not worth a response. If our roles were reversed, and this was a mainstream rather than a contrarian blog, I would suspect you of trolling.

Aug 14, 2012 at 6:55 PM | Unregistered CommenterBBD

I despair.
Not a single word of that quote is empirical evidence that CO2 causes warming. Your first paragraph is an assertion and contains no evidence that increased CO2 (from ocean out-gassing?) is anything other than a consequence of warming. You provide no evidence that it is anything else which makes your statement that it is a "necessary" part of the process just one more assertion.
I am not going to dispute your second paragraph because I don't know whether you are correct or not.
And neither do you.
There are several hypotheses as to what initiates the deglaciation but I see no reason from what you say to assume that CO2 is an essential part of the process.
In any case we are not discussing what causes the ends of ice ages. We are talking about the last 2000 years and the causes of the various warm and cool periods that have occurred during that time.
At no stage has anyone, on either side if this debate, suggested that CO2 has been the cause of any of the warm periods — until this one. The presumption ought to be that whatever caused the previous warm periods is most likely responsible for this one, absent any empirical and convincing evidence to the contrary which you consistently fail to provide.

... as for the rest of the tripe about 'Santer is evil' and 'what is the scientific mainstream?' and 'have they looked for anything else?' - it's not worth a response.
Cop out. Presumably because you don't have an answer.

Aug 14, 2012 at 7:45 PM | Registered CommenterMike Jackson

Not a single word of that quote is empirical evidence that CO2 causes warming.

You might want to go back to the discussions upthread and on the 'best evidence revisited' thread about the relationship between CO2 and T over deep time (eg the entire Cenozoic).

As I said to Philip earlier, it all fits together.

Aug 14, 2012 at 8:00 PM | Unregistered CommenterBBD

Another evasion.
"It all fits together" is not empirical evidence. It's hand-waving.

Aug 14, 2012 at 8:34 PM | Registered CommenterMike Jackson

"It all fits together" is not empirical evidence. It's hand-waving.

And you are doing what, exactly?

:-)

If you know of any evidence that the major change in forcing over the Cenozoic *wasn't* CO2, please share it.

Aug 14, 2012 at 8:54 PM | Unregistered CommenterBBD

Mike

I am not going to dispute your second paragraph because I don't know whether you are correct or not.
And neither do you.

Here's what I take it we are talking about:

One of the interesting things about orbitally forced deglaciation is that the total amount of solar energy reaching the earth's surface is barely increased. Yet it's enough to end an ice age. It's the *regional and seasonal* effect that triggers melting of the NH ice sheet which gets the feedback ball rolling. Just increased summer insolation at high Northern latitudes. How could this end an ice age unless feedbacks net positive?

Put another way, how can an insensitive climate system dominated by negative feedbacks behave like earth's climate system under these circumstances?

It's like holding one of those little geography class globes near a desk light. If you tilt the axis a bit you can increase the intensity of light up near the top without increasing the *total amount* of light falling on the globe as a whole.

The key thing here is that the degree of axial tilt varies slowly but cyclically over time (the obliquity cycle).

The earth's orbit around the sun also gradually varies between circular and slightly elliptical, but again the cycle is regular (orbital eccentricity).

Put the two consistently repeating but different cycles together and roughly every 100,000 years summer insolation at high northern latitudes peaks. But *total* global insolation rises only slightly.

The peak summer orbital forcing at high NH latitude apparently initiates glacial terminations by melting and destabilising the NH ice sheet. But it is not sufficient to account for the full warming that occurs during deglaciation. This requires a synergy of positive feedbacks - or a healthy peck of fair dust. Otherwise, nothing much could happen and the climate system would have got stuck in a glacial state.

Orbital dynamics is pretty iron-clad, which leaves us with positive feedbacks and a moderately sensitive climate system.

I can see that I haven't yet explained this to your satisfaction, so I hope this helps.

Aug 14, 2012 at 10:30 PM | Unregistered CommenterBBD

Oh boy! Is this ever getting tedious.

If you know of any evidence that the major change in forcing over the Cenozoic *wasn't* CO2, please share it.
Just how many more times do I have to ask you to show the empirical evidence that it was?
And as I said before, since no-one has yet claimed that CO2 was responsible for initiating the Minoan Warm Period or the Roman Warm Period or the Mediaeval Warm Period will you please provide me with the empirical evidence that it was responsible for the Modern Warm Period?
And talking about ice ages and orbital dynamics does not address the point; that is merely another diversionary tactic on you part. Try to concentrate on the actual question I am asking.
On the basis of Occam if nothing else the onus of proof that the Modern Warm Period was caused by CO2 when there is no evidence that any of the preceding three similar periods were so caused (and evidence that they weren't) lies with those who are making the claim.
Where is the evidence?

Aug 14, 2012 at 11:04 PM | Registered CommenterMike Jackson

Odd. You skipped a whole comment there. See Aug 14, 2012 at 10:30 PM.

Just how many more times do I have to ask you to show the empirical evidence that it was?

Follow the references in HS12. Are those reconstructions of paleoatmospheric CO2 wrong? Why? Where's the evidence?

Aug 14, 2012 at 11:55 PM | Unregistered CommenterBBD

"It's like holding one of those little geography class globes near a desk light. If you tilt the axis a bit you can increase the intensity of light up near the top without increasing the *total amount* of light falling on the globe as a whole."

It is the same crap propaganda from science communicators. Don't recycle them.

Got any examples of your own?

Philip, here is a example in relation to my earlier question.

If the earth tilts a 'little' - just as our friend here quotes from his catechism - does that produce a 'small' change in forcing?

Aug 15, 2012 at 3:38 AM | Registered Commentershub

This whole discussion is the one of the insane ones I've read - not counting sane participants.

The evidence from paleoclimatic reconstructions spanning periods encompassing millions of years a stretch, is used as the basis for firm predictions of what will happen in the coming few years. This is the definition of madness.

Aug 15, 2012 at 3:52 AM | Registered Commentershub

This whole discussion is the one of the insane ones I've read - not counting sane participants.

The evidence from paleoclimatic reconstructions spanning periods encompassing millions of years a stretch, is used as the basis for firm predictions of what will happen in the coming few years. This is the definition of madness.

Aug 15, 2012 at 3:52 AM | shub>>>>>

We should be used to BBD's trolling techniques by now.

There is NO empirical evidence for any of his assertions repeated ad nauseum.

He just likes to make a lot of noise and arguing with him just encourages him further, as with his new best friend Philip - who I don't recall seeing till a couple of weeks ago.

Everything BBD says is pure speculative garbage. He calls himself a sceptic regarding climate discussions and then plays chief groupy to his hero Hansen.

In fact, he'll say anything at all to get the response his narcissistic ego so craves - ignore him, he's just another version of ZDB.

Aug 15, 2012 at 4:30 AM | Unregistered CommenterRKS

Aug 15, 2012 at 3:38 AM | shub

If you mean the forcing due to Milankovitch effect, it is small. See for example,

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

As I've tried to point out several times, it is not plausible that the Milankovitch effect is directly responsible
for the glacial transitions, with or without help from CO2.

Aug 15, 2012 at 9:30 AM | Registered CommenterPhilip Richens

Shub,

This one may also be helpful.

http://www.clim-past.net/5/481/2009/cp-5-481-2009.pdf

At the end, "If the glacial cycles are chaotic, or almost so, the implied sensitivity to initial conditions – in conjunction with the inevitable stochastic influences upon glaciation – renders predictions of future glacial cycles highly uncertain."

Aug 15, 2012 at 9:48 AM | Registered CommenterPhilip Richens

As I've tried to point out several times, it is not plausible that the Milankovitch effect is directly responsible
for the glacial transitions, with or without help from CO2.

Aug 15, 2012 at 9:30 AM | Philip Richens>>>>

So what do you suggest IS responsible?

Aug 15, 2012 at 9:54 AM | Unregistered CommenterRKS

Aug 15, 2012 at 9:54 AM | RKS

This is a large part of what I've been trying to discuss with BBD in earlier comments on this thread. The glacial cycles mostly represent the internal dynamic behaviour of the climate system - chaotic slooshing about if you like. Orbital and other forcings must surely have some impact (e.g. by pumping the system, orbital effects seem to cause transitions to occasionally synchronize with the orbital periods), but when you look at the spectrum (i.e. Fourier transform) of ice core reconstructions, the various Milankovitch periods scarcely register at all. This is why the naïve invocation of orbitals is certainly incorrect.

Aug 15, 2012 at 10:22 AM | Registered CommenterPhilip Richens

You skipped a whole comment there.
No, I didn't skip it, BBD; I ignored it for the very simple reason that it is not answering the question that I am asking, as you well know.
I really should go and get a life but I'm a persistent bugger so I'll try again.
This is the question which you chose to "skip"
since no-one has yet claimed that CO2 was responsible for initiating the Minoan Warm Period or the Roman Warm Period or the Mediaeval Warm Period will you please provide me with the empirical evidence that it was responsible for the Modern Warm Period?
Simple question, no? Nothing to do with your 10.30 contribution; everything to do with what is happening now
Shub understands what I'm asking; RKS understands what I'm asking. You understand what I'm asking (unless you're stupid and that I have never accused you of). So either give us the answer or admit you don't know.

PS If your answer includes the words 'Hansen' or 'Sato' I shall probably throw myself off a high building. As far as I'm concerned (and I'm by no means alone) Hansen has lost any credibility as a scientist that he might have especially looking at his latest offerings. I view him the way you view Willie Soon.

Aug 15, 2012 at 11:21 AM | Registered CommenterMike Jackson

Philip
I was interested in something that Singer and Avery wrote about in their Unstoppable Global Warming - Every 1500 Years. (No, BBD, I'm not saying I agree with their hypotheses; I haven't even finished the book yet. Just before you jump down my throat!)
There appears to be a fairly wide variation in that 1500 year figure — like +/- 500 years! — and there is no solar or other cycle that they could find of that length.On the other hand they identified two cycles which were prime factors of 1500 (approx) and speculated that the conjunction of those two cycles might be what causes the apparent 1500-year cycle.
A bit like 5-year and 3-year cycles reinforcing each other every 15 years. If both the component parts of that 15 have a variation of only 0.2 that would give a variation of 1.6 purely on simple maths (which is as far as I go, I'm afraid). Sorry if I'm spelling this out; it's mainly for my benefit!!
I just wondered if some of these cycles we're discussing weren't actually cycles in themselves but a "collision" of other cycles which is why they don't quite seem to behave as we think they should. It looks like just one more reason to doubt that we can ever really understand climate or what it gets up to.

Aug 15, 2012 at 11:42 AM | Registered CommenterMike Jackson

Philip

As I've tried to point out several times, it is not plausible that the Milankovitch effect is directly responsible for the glacial transitions, with or without help from CO2.

See Shakun et al. (2012). Warning: people who insist that CO2 lags T during deglaciation are going to have an unpleasant surprise. Those with open minds simply wondering *how* high-latitude NH forcing triggers deglaciation will find much of interest.

This is why the naïve invocation of orbitals is certainly incorrect.

You are in the minority there, so a little less certainty would be appropriate. It's interesting to see the rise of 'Milankovitch denial' hand in hand with elephant blindness though.

Aug 15, 2012 at 2:00 PM | Unregistered CommenterBBD

Mike

The point here is not what caused warm periods (which were probably not globally synchronous anyway) this side of the Holocene Thermal Maximum. The problem is what happens when you increase CO2 forcing in a demonstrably sensitive climate system.

Energy begins to accumulate, both in the oceans and the atmosphere. Natural variability continues, as does negative forcing from anthropogenic sulphate aerosols, but the CO2 signal slowly begins to emerge. The results look like this.

This discussion has taken in three general things: the relationship between CO2 and T over *deep time*; the demonstration that the climate system is at least moderately sensitive (which *requires* that feedbacks net positive) and the implications this has if CO2 forcing is substantially increased.

Argue with the physics all you like; it's foolish and it changes nothing. You are surrounded by empirical evidence that CO2 forcing is causing energy to accumulate - slowly at present - in the climate system. Have a look at Arctic ice, or the latest about the Greenland Ice Sheet, or check up on permafrost melt - google is your friend. The evidence - solid, empirical evidence - is everywhere. Only you refuse to see it. And I can't help you with elephant blindness I'm afraid.

Aug 15, 2012 at 2:21 PM | Unregistered CommenterBBD

Mike,

Whilst I haven't read their book, I think the kind of relationship you mention sounds quite plausible. You may also like to ponder the beautiful colour diagrams in this paper. They are near the end, starting with figure 5. Note that the figure caption appears below the diagram. They are created using a type of spectral analysis that shows up how the spectrum changes over time. So the x-axis is time, whilst the y-axis shows the strength of the oscillations of different periods. For example in the top right of figure 5 there is a powerful 1500 yr cycle going back for 6000 years - just 4 cycles, mind.

A homespun way to visualize the kind of thing that is going on, is to imagine that the interactions between the different components of the climate system create a wrinkled surface over which a billiard ball travels. The position of the ball represents the state of the climate system and the path of the ball represents how it changes over time. The ball never comes to rest because the surface is constantly jiggling. Dimples in the surface create the possibility of temporary cycles, but the ball can easily be knocked away either to a different dimple or to a more aimless wandering around. There may also be severe dips in the surface, even holes, that can cause sudden large changes to the ball's path. Forcings - e.g. orbital, solar, CO2 - will then modify the position and height of the wrinkles and also help to push the ball around.

This Rial/Pielke paper is rather good if you haven't already read it. It not only describes the kinds of processes that are involved, it also spells out the implications in terms of the likely impacts of climate change.

Aug 15, 2012 at 2:24 PM | Registered CommenterPhilip Richens

BBD,

I apologise if the discussion on this thread has pushed you outside your comfort zone, but to be honest when you get into "fortress mainstream" mode, it is pointless trying to talk to you (although I admit that the addition of the zoo is a new feature). Why not give it a rest for now, and let’s resume again when you're prepared to make an effort to say something interesting.

Aug 15, 2012 at 2:33 PM | Registered CommenterPhilip Richens

shub

It is the same crap propaganda from science communicators. Don't recycle them.

Got any examples of your own?

Eh? This *was* my own example. If you have an example of it being used elsewhere, please link. I'd be interested to see. You aren't by any chance just saying *anything you can think of* in an attempt to delegitimise me, are you? I'm shocked, I tell you, shocked.

Although not as much as I was by this:

If the earth tilts a 'little' - just as our friend here quotes from his catechism - does that produce a 'small' change in forcing?

That's *proof* that you have completely failed to understand Milankovitch forcing, despite repeated explanations. You should be embarrassed.

Aug 15, 2012 at 2:43 PM | Unregistered CommenterBBD