TinyCO2

Fag packet calculation. Marcott et al shows a decrease in temperature of 0.5C over the last 5000 years to 1910. If that continued, cooling would bring us to 5C cooler than the Holocene Optimum(full glacial period conditions) in another 45,000 years.

Entropic man, all indications are that once the global temperature passes a certain point, it falls off a cliff. I can't see why. It doesn't seem to be CO2 or insolation. It seems to be one of those unknowns.

Tiny CO2

It follows an s- curve.

This is typical of systems which switch between stable states. Such processes tend to start with a small trigger change. This is then amplified by feedbacks to a more rapid rate of change.

Past a certain point the feedbacks decrease and the system settles to a new equilibrium.

Think of recording the angle of a seesaw. Left to itself it sits with one end on the ground. As you walk up it no change happens until you pass the pivot, at which point it changes quickly until the other end is on the ground.

For interglacial and glacial periods the key figure is insolation at 65N, which changes as Earth's orbit changes (research Milankovich cycles)

TinyCO2
I think what EM is talking about is a well known electronic circuit The Astable Multivibrator, which flips between two states in a regular way. The difference is that multivibrators are fully understood in their electronic form, in their climatic form the mechanism for flipping between states and why the clock period is what it is are not well known at all, despite EM's claims there are some who claim Milankovich is only part of the story (see Skeptical Science wink), as you'll see if you do research Milankovich.

Couple of links below

Multivibrators
Why an ice age occurs every 100,000 years: Climate and feedback effects explained

Richard Lindzen, the well known skeptical professor from MIT, has also previously cited papers such as that by Roe, 2006 "In defense of Milankovitch".

If correct, this indicates that CO2 plays a minor role. Roe doesn't need CO2 to get impressive matches of Milankovitch cycles with temperature. This is quite consistent with CO2 lagging temperature throughout the glacial cycles, not driving it. If CO2 played little role then, then it seems reasonable to think it plays little role now.

We already know that the thing flips, the question is what triggers it other than insolation? If scentists knew what happened then there'd be a nice little model output. They'd know why previous intergalcials were spikey and this one was relatively flat. I can understand ocean phases putting a spanner in a decadal model and maybe even one over centuries but why can't they model the big stuff? Answer they still don't understand all the things that drive climate. You can't call yourself a baker just because you know cake involves flour, sugar and eggs.

Martin A, Tiny CO2, Michael hart, Sandy S

Glad to see that you know the Milankovich theory in such detail. The main question becomes- Are the forcings and feedbacks sufficient to produce the observed changes without CO2? Do you have numbers for this?

EM how many time do you miss the point? We say it's not possible to model climate yet, possible never. We have no super computer. We have no research departments. We are not being paid. Why on earth do you expect us to have the answers? But we don't need to be an expert to tell the other side doesn't have the answers either. Come on, show me a model that can roughly generate the last few ice ages and interglacials... No?

So it comes down to how much do you believe what's on the science table? Serious how much £££?

TinyCO2

"Come on, show me a model that can roughly generate the last few ice ages and interglacials... No?"

Try googling" modelling glacial periods"

Most of the search results are PDFs, which is why I have not provided links. Enjoy.

Tiny C2

If you have no information, why are you convinced that CO2 is not a factor?

Martin A, Tiny CO2, Michael hart, Sandy S

Glad to see that you know the Milankovich theory in such detail. The main question becomes- Are the forcings and feedbacks sufficient to produce the observed changes without CO2? Do you have numbers for this?

Jun 27, 2015 at 10:33 PM | Unregistered CommenterEntropic man

EM 'Try googling" modelling glacial periods"'

No, you google and find one where they succeed in matching the past 400,000 years or so, not one that can make up and down wiggles in a random pattern, or worse, just talk about how it's theoretically possible. Post a link or two. Hint, if it doesn't include a picture of the output it DOESN'T WORK. (michael hart, I'm afraid that applies to your paper too. I've fallen before for the theoretical papers that don't illustrate their ideas with plots. They may be true but I've lost patience with stuff that could be an opinion piece for all I can tell.)

EM "If you have no information, why are you convinced that CO2 is not a factor?"

Where did I say it wasn't? Clealy lots of things are a factor, the principle one being Milankovitch cycles. But like I wrote, just because you know some of the ingredients, doesn't mean you know how much of an effect comes from each item or if there are a load of unknowns that have a significant role in the final glaciation cake. In terms of CO2, the effect even varies as atmospheric content changes.

To draw in Stewgreen's comment, I behave in a way that is consistent with how afraid I am of CO2 ghosts. Most people who ignore AGW seem to be doing the same. What about your side EM? Which side is in denial and which side genuinely doesn't believe the science very much? How scared of CO2 are you and what % of your income are you prepared to wager on it? Or how much per year? How much intereferance in your life are you happy to experience? If you won the lottery would you live in a small flat or a small estate? Have you put those dream holiday plans in the bin? Those are the only true measurements of how convincing you find CAGW science.

TinyCO2

Certainly, if I knew how.

Could you show me how to reliably link to a pdf.

I already have. I am a biologist. As a biologist the greatest sacrifice I can make is reducing the number of copies of my genes in future generations, by limiting the sixe of my family.

Entropic Man
Do you mean a PDF link like this PDF to specific page if the answer is yes then just replace these brackets {} with these < > in the string below.

{a href="http://partners.adobe.com/public/developer/en/acrobat/sdk/AcroJS_DesignerJS.pdf#page=24"}PDF to specific page{/a}

You can use the Preview Post button to check functionality. We're always glad to help biologists struggling with technical issues they don't understand (Just to return a teachers sarcastic humour, which doesn't work on adults).

I didn't say I had a full and comprehensive knowledge of Milankovich just that there is a degree of doubt in the scientific community that they are a total explanation. I would have thought the link to SkepSci would have been enough for you.

EM "by limiting the size of my family"

Not impressed, not even if you have no kids. People limit the size of their families for all sorts of reasons that have nothing to do with AGW. If not having m/any kids was ok to set off against emissions then almost the entire western world is doing its bit with small or falling birthrates. They're even more successful than China with its one child policy. Only immigration is keeping most western populations from falling. If we ban immigration can we forget about reducing CO2? No?

Like every other warmist, you're prepared to give up very little for your cause.

Tiny-CO2, unlike EM, I did at least take the trouble to insert a few caveats by using the if word. My main point was that while EM blithely asserted in his usual way what he appears to consider unassailable fact about how Milankovitch regulates glacial cycles, Roe shows this would leave little scope for significant effects of CO2 during glacial cycles. Roe may, or may not, be correct, but neither outcome lends support to EM's CO2-centric vision.

I'm not having a go at you michael but I thought I'd get in before EM said he didn't need to provide visuals if you didn't. Frankly too much of science is about theory and not about demonstrable proof. The continuous slurry of poor science press releases has made me very tired of science as a legitimate profession. They need to find a better way of showing their employers that they are working hard than publishing trivia or worse.

Fag packet calculation.

Temperature difference between Holocene Optimum and last glacial period is 5C.

At 3.7W/C that is a total forcing+feedbacks of 18.5W/m2.

Orbital forcing 3.7W/m2

Trace gas forcing 2.76W/m2 ( of which CO2 is 1.45)

Ice-albedo feedback 2.36W/m2

Dust feedback -1.0W/m2

Other feedbacks 18.5 - 8.82 +1.0 =10.58W/m2.

This would require climate sensitivity of 10.58 +3.7+2.76 / 3.7+2.76 = 2.68

Most of these figures come from Burt et al .

This looks like a reasonable approximation of the energy change required to drive a glacial to interglacial transition with minimal computer modelling required. I think you overestimate our ignorance.

PS Thanks, Sandy S. I tying found the problem. The language is the same as I use for other links. My problem was in transferring the PDF address into the post without my tablet sending me to my downloads.
43 pages of IT jargon was no help at all. Methinks engineers humour is just as unfunny as teachers humour. ☺

MartinA

Hopefully tonight.

EM,
The link was to a pdf near the top of my history, it wasn't really meant as homework.

MartinA

Hopefully tonight.

I take something more important came along?

Sandy S

My wife is in hospital and life just got a lot more complicated.