Chefio: D.O. Ride My See-Saw, Mr. Bond

[Amatør1]

ConTraris rotte-tråd Smutthull -the rat hole  fikk meg til å returnere til Monckton's WUWT-tråd Bethlehem and the rat-hole problem, for å se om det var kommet til noe vesentlig nytt.

Det viste seg at kommentarene var mange, og noen av dem var interessante. Hver gang jeg ser E.M.Smith (også kjent som "Chefio") sitt navn, pleier jeg å være litt ekstra oppmerksom, for derfra har det en tendens til å komme interessante og tankevekkende observasjoner. Denne gangen kommenterer Chefio LazyTeenagers uttalelser om 'stabilt klima', kommentaren er her.

Det hele var såpass interessant, at jeg tar meg friheten til å gjengi Chefio's kommentar her, da det ellers lett vil forsvinne i den store massen av kommentarer. Uthevningene er mine + jeg har lagt inn diagrammet han linket til på Wikipedia.



I hope you find this useful in seeing how 'stability' works in the climate system of Earth.

in this article:
http://chiefio.wordpress.com/2012/12/15/d-o-ride-my-see-saw-mr-bond/

I explore some of the oscillatory events in our climate history. Along the way, I found a paper that points out some rather interesting things. In particular, it bears heavily on the question of "Tipping points" and stability. (homeostasis vs instability vs hysteresis or 'bi-stable' oscillator).

In fact, the climate undergoes changes from a stable form, to a hysteresis form, and then onto a new nearly stable form. Unfortunately, it becomes less stable as you cool (from our present state), and more stable as you warm (from our present state). Cool enough from our present state, you end in the only really stable mode available; an Ice Age Glacial.

I say 'unfortunately', because at the resent levels of insolation, we are now leaving the hysteresis stage where we can be 'flipped' to either the warm side, or the cold side. As we are already at the limit case of the "warm side", the only climate catastrophe we can have is a flip to the cold side. That is, we can fall off the Holocene warmth and back into a glacial. (In a glacial, you become highly stable in cold, only occasionally meta-stable with a warm spike, then fall back to cold).

http://www.pik-potsdam.de/~stefan/Publications/Nature/rapid.pdf

    Abrupt changes in climate, termed Dansgaard-Oeschger and Heinrich events, have punctuated the last glacial period (~100 – 10 kyr ago) but not the Holocene (the past 10 kyr). Here we use an intermediate-complexity climate model to investigate the stability of glacial climate, and we find that only one mode of Atlantic Ocean circulation is stable: a cold mode with deep water formation in the Atlantic Ocean south of Iceland. However, a `warm' circulation mode similar to the present-day Atlantic Ocean is only marginally unstable, and temporary transitions to this warm mode can easily be triggered.

I'll translate for LazyT:

That says that the glacial OMG Cold and frozen state is the only stable one. BUT, sometimes, you can get a bit of a kick into a warmer state (like we are having now). The warmth just is not very stable, and the "tipping point" is back to cold.

(The orbital mechanics that make it possible to have an interglacial are rare, only happening about once every 100,000 years. We are now exiting that regime and the present W/m^2 above 65 N or so is below that which leads to stable warmth. )

    Two main types of abrupt climate changes have punctuated the last glacial period: Dansgaard-Oeschger (D/O) events and Heinrich events. D/O events typically start with an abrupt warming of Greenland by 5-10 °C over a few decades or less, followed by gradual cooling over several hundred or several thousand years. This cooling phase often ends with an abrupt final reduction of temperature back to cold (`stadial') conditions.

The basic driver for the D.O. warming events still exists. Notice that Greenland gets a bit warmer in a few decades, then over a long period of time things cool? That it can plunge back to the only really stable state, a cold "stadial" (LazyT: that means glacial ice and frozen as in Ice Age frozen) conditions.

So what have we had? A modest warming in Greenland and a sudden downturn in the sun, with the return of lots of snow over the N. Hemisphere. (We are now 'coloring outside the lines' of the climatology on the N.H. snow map from FSU.EDU here:

http://moe.met.fsu.edu/snow/

I looked at it a bit earlier here: http://chiefio.wordpress.com/2012/12/18/about-that-snow-cover/
when it was about at the green 'climatology' line.

So where we are at is that the orbital mechanics have already left the very brief warm state that can cause an 'inter-glacial' excursion. We are now 'on the cusp' of a return of the glacial conditions. There is a single highly stable state, and that is glacial / frozen. There is no "tipping point" to the upside (only a hysteresis halt to warming overshoot via the water cycle) but there is a "tipping point" to the downside (as we are warm right now and the other end of the hysteresis is the cold end... the "light switch" can only be on, or off, and we're presently "on", so can only swap to "off".)

    Once the system is in the `warm' mode with convection in latitudes north of Iceland, it becomes insensitive to the applied, weak 1,500-year forcing cycle (this experiment was performed but is not detailed here). The freshwater budget of the Nordic Seas is then dominated by the vigorous circulation; anomalies in surface forcing cannot accumulate to create noticeable salinity anomalies as in the stratified `cold' mode. For this reason, the Holocene climate in our model is stable with respect to the 1,500-year forcing cycle, while the glacial climate is not. We can thus explain the large fluctuations of Greenland temperature during the glacial climate in terms of ocean circulation instability, requiring only a weak trigger but not necessarily any major ice-sheet instability. In the Holocene, the 1,500-year cycle is still present but is not amplified by ocean circulation instability, so that its signature is only weak.

Got that, LazyT? Holocene is STABLE to the upside and does not warm beyond present. Ice Age Glacial is STABLE, but it CAN have ocean oscillations that cause brief (Pleasant!) warming to near present state.

However, we are not at the beginning, nor even the middle, nor even the last 3/5 point of the Holocene. We're in the final stages. The amount of 'extra solar warmth' available at the N. Pole is lower every century than the one before, and we've reached the point where a "tip" can happen. But not to the warmer side. Only to the cold and frozen side.

Look at the chart / graph here:

https://en.wikipedia.org/wiki/File:MilankovitchCyclesOrbitandCores.png



The 3rd line up from the bottom. The black one. Compare it to the two bottom lines (benthic forams and Vostok.

That black line is how much of the energy needed to cause a Holocene like interglacial is being handed to us. Now look at the peaks on the prior 3 interglacials. Notice interglacials are triggered to happen at a much higher level of the black line. Notice that the present level of the black line is completely compatible with the glacial state (there are cold glacial conditions at other times when the black line is at our present level). Look very carefully at the black line where the vertical 'you are here' crosses it...

We've left the peak energy state, we've dropped to the median, and we're now able to plunge into a cold glacial at any time. But we can not go the other way. (Most obviously because we're already in the warm mode, thermal limited by convection and thunderstorms; but secondly due to not enough warming far enough north any more. That black line says so.). Now look to the right on the black line. We get a small chance of coming out of the next glacial in about 100,000 years, but the only really good one is in 200,000 years.

Now the "good news" is that there are not a lot of 'low going' dips for the next 100,000 years either. If we are Really Really Lucky (and do some things to help keep the N. Hemisphere from freezing up, which triggers the glacial...) we have a small chance of holding off the cold plunge into the next glacial. We just barely dodged that bullet in the Little Ice Age.

That means any added warming we can get is a Very Good Thing. Because those periodic 1500 year 'excursions' still happen. And one 'dip' to the cold side ( or one giant volcanic event or one really big rock from space or...) and we go back to the stable glaciated state.

So despite my efforts to show Global Warming is a crock: I really do hope, with all my soul, that the Greenhouse Gas Theory is correct. If it isn't, there is nothing much to stop New York going back under a mile of ice... (Germany and Sweden / Norway would not be very well treated either, nor would Scotland. Best polish up those Spanish Language skills if the snows come, and don't leave fast.)

At any rate, the paper looks to be reasonably well done, and the historical data / context are well attested. Our orbital mechanics are about as solid and things can be. The ice cores and benthic forams record clearly what events happen, and in what order. This puzzle fits together "one way". And it answers the question of climate stability.

Limited to the upside by increasing evaporation, thunderstorms, etc. at a Holocene Optimum like level. (About 2 C more than now, peak). Most stable in an Ice Age Glacial (but can have brief excursions to conditions like now – that are unstable). Only a specific set of orbital conditions let that unstable warm state last longer (an 'interglacial'), and we've left that set of conditions behind.

The next flip to cold, switches us to the glacial regime, where we stay for at least 100,000 years; modulo the occasional Heinrich Event of incredibly short duration.

That is the nature of our climate 'stability'. We are stable when frozen. Everything else is a short duration gift.


Hva synes dere? Er dette istids-alarmisme, eller er det en realistisk vurdering av hva vi står overfor i de nærmeste århundredene som kommer?

[ConTrari]

"We are stable when frozen"  høres ut som et rimelig trygt utsagn.

Men hva de neste århundrer vil bringe, vil vi først få se om noen århundrer.

Men en ny istid på det tidspunktet, hvis den får samme utstrekning som dcen forrige, behøver ikke å bli noen katastrofe. Bare tenk på alle de supereffektive norske skatteinnkreverne som vil få jobb i Hellas og Burkina Faso