Wednesday, January 14, 2009

Read on the checkout line

The latest ignorance spreading through the denialsphere is a provocation published in Pravda by a 9-11 truther (he believes that George did it) with the handle Fegel. This is pretty much standard stuff, Al Gore is FAT* and introduced the now broken hockey stick curve**, CO2 lags warming coming out of an ice age***, etc. As Tim Lambert puts it, remember when right wingers didn't trust Pravda? Pravda appears to have made the jump from Communist Party rag to supermarket checkout line rag without stopping for a rest in the middle. The wonders of the market.


The bottom line in this provocation though is Fegel's propagation of ignorance

The main flaw in the AGW theory is that its proponents focus on evidence from only the past one thousand years at most, while ignoring the evidence from the past million years -- evidence which is essential for a true understanding of climatology. The data from paleoclimatology provides us with an alternative and more credible explanation for the recent global temperature spike, based on the natural cycle of Ice Age maximums and interglacials.
There is a chapter in every IPCC report on paleoclimate, which considers what we know about ice ages in detail. The AR4 chapter concludes (very long download, don't do this on your dial up line):
It is virtually certain that global temperatures during coming centuries will not be signifi cantly influenced by a natural orbitally induced cooling. It is very unlikely that the Earth would naturally enter another ice age for at least 30 kyr.
VIRTUALLY CERTAIN is reserved for such things as the sun will rise in the morning. Science bunnies are very cautious. Besides labeling Fegel for wingnut of the week, we need to dig a bit deeper into this. It has been covered a few places, in a somewhat indirect way, which assumes that the reader has some background. Two are a delicious comment in Deltoid by William Hyde, which ends with

So here we see a denialist using a rejected idea of the early 1970s, which other people in his camp use as an example of bad climate science, as good science which "refutes" AGW.

As it turns out this interglacial looks more like the anomalous stage eleven interglacial, which was of approximately double normal length. By one calculation the "on ramp" for the next ice age occurred 800 years ago, and we missed it. The next one isn't for eleven thousand years.

Come to think of it, that was also discussed in Imbrie and Imbrie. Guess he didn't get to the last chapter.

and Eli will find the other one soon (same point tho).

To really understand why this is such a sure thing (bet the bunnies on it if you can find a long lived sucker) the dedicated reader should go read Imbrie and Imbrie, maybe the last chaper, the AR4, TAR, etc. However, the classic Rabett take is that small orbital changes decrease the amount of sunlight striking the Earth and lead to summers in which ice persists over large areas of the Northern Hemisphere. Ice sheets can therefore grow over time driven by positive feedbacks including changes in the albedo. Taking all this into account the AR4 authors conclude.
6.4.1.8 When Will the Current Interglacial End?

There is no evidence of mechanisms that could mitigate the current global warming by a natural cooling trend. Only a strong reduction in summer insolation at high northern latitudes, along with associated feedbacks, can end the current interglacial.

Given that current low orbital eccentricity will persist over the next tens of thousand years, the effects of precession are minimised, and extremely cold northern summer orbital configurations like that of the last glacial initiation at 116 ka will not take place for at least 30 kyr (Box 6.1). Under a natural CO2 regime (i.e., with the global temperature-CO2 correlation continuing as in the Vostok and EPICA Dome C ice cores), the next glacial period would not be expected to start within the next 30 kyr (Loutre and Berger, 2000; Berger and Loutre, 2002; EPICA Community Members, 2004). Sustained high atmospheric greenhouse gas concentrations, comparable to a mid-range CO2 stabilisation scenario, may lead to a complete melting of the Greenland Ice Sheet (Church et al., 2001) and further delay the onset of the next glacial period (Loutre and Berger, 2000; Archer and Ganopolski, 2005).
Bottom line, we don't have a year 10K problem, we may have a year 30K problem assuming that there remains any ice in the Arctic. Don't bet on that the way things are being driven.

UPDATE: Inel has attracted the Fegel hisself

* Al Gore is stout
** The hockey stick curve was introduced by Mann, Bradley and Hughes in 1998, and since then, although the statistical methodology has been challenged, every other paleoclimate study has shown a similar behavior with improved statistic.
*** The way it works is that orbital changes(Milankovitch cycle) lead to a small amount of warming coming out of the ice ages (that is a so called forcing, something external to the Earth's climate that affects it). The system responds by releasing more greenhouse gases, CO2 (fizzy coke effect) and higher water vapor and melting ice which changes the albedo. If you do it nature's way this takes a couple of thousand years. In that case the CO2 functions as a positive feedback which complete the warming.

Although the primary causes are different, this is completely consistent with increasing CO2 concentrations by any means leading to a warmer atmosphere and surface. The only difference is that we have forced, a ~33% increase in CO2 over 100 years, very fast for geological processes. This is a forcing, because it came from outside the climate system, but the effect is the same. It's very basic stuff. As a matter of fact you expect that CO2 will lag warming coming out of an ice age, because ice ages end not because of initiating CO2 increases, they are accelerated by them

Real Climate goes into more detail

Figure is from the AR4 paleoclimate chapter Box 6.1
Comments?

17 comments:

Anonymous said...

Eli: forgive me for perhaps going a little off topic, but here is a question? Milankovitch cycles consist of 3 main components. Two of those components (the precession of teh equinoxes and the axial tilt) will not change the amount of sunlight striking the earth, but rather where the sunlight strikes.

I am not so sure about the third (the eccentricity). If the eccentricity only consisted of a change in the time of the year for perihelion and aphelion it would again not change the amount of the sunlight striking the earth - just where and when it was most intense. However the actual eccentricity of the orbit changes as well from nearly circular to mildly (very mildly) elliptical. Will this change in eccentricity give rise to a change in the total amount of sunlight striking the earth (taking into account the distance from the sun at different times and the speed at which the earth moves at different parts of the ellipse)? If so will there be more sunlight striking the earth in its near circular stage or its more elliptical stage?

Thanks,
John Cross

EliRabett said...

John, The AR4 Chapter (follow link above) has a reasonably good explanation of what each type of wiggle does. Learned a lot from it Eli did. My understanding is that the key thing is the insolation of the northern hemisphere during summer. If this gets low enough that snow can last thru the summer ice sheets can build

Mike Bantom said...

John,

Tamino in his usual precise style tackles all the cycles. Here is his math on eccentricity.

http://tamino.wordpress.com/2007/11/19/wobbles-part-1/

Eccentricity has a small effect on overall incoming solar radiation, 0.43 W/m^2 between the maximum and minimum eccentricity.

As Eli points out the main effect of eccentricity is the change of insolation on the North Hemisphere, hotter summers and colder winters trigger deglaciation.

jg said...

Professor Rabbet,
Thanks for this post, mainly because it gives me (an amateur) a chance to say that I enjoy your blog.

In my community, people still need to be convinced that climatology is a legitimate science.

I've found that people open up to the concept of orbital changes and ice ages whereas leading with CO2 provokes a politicized debate. (Many local media have pandered to global warming denialism; so a lot of damage needs to be undone).

I'm eager to hear any more you have to share on orbital forcing, and I'll be reading the IPCC
chapter you provided. Also, I've tried to illustrate orbital changes that you or some of your readers may enjoy looking at here:

http://brightstarstemeculavalley.org/animations/earthOrbitAndClimate.html


Thank you,
JohnG

Arthur said...

Al Gore is stoat! That explains a lot. But wait, maybe not. Oh, I misread, oh dear :-)

jg said...

Sorry. My first post, and I botched it. Here's the link I intended to share:

http://brightstarstemeculavalley.org/animations/earthOrbitAndClimate.html

Your tolerance is greatly appreciated.

JohnG

Steve Bloom said...

Weasels will rip your flesh for that, Arthur!

JohnG, the persistence of the CO2 lag zombie lie is interesting. IMHO any slightly reasonable person who's stepped through the logic will abandon it forthwith. The following may be useful:

1) No scientist has ever been confused on this point; i.e. it is entirely an invention of propagandists.

2) CO2 leading would be inconsistent with our basic physical understanding of how climate woks. That CO2 must lag was predicted long before the ice cores proved that it was the case. For CO2 to lead, there would have to have been a reservoir of it somewhere that was injected into the atmosphere by yet some other factor (since CO2, being a relatively non-reactive gas, can't just push itself around).

3) How the lagging CO2 got into the atmosphere was a mystery for a long time (and this may help explain the persistence of the zombie lie). Much has been learned of late, though. See this recent article, written to be understandable by the relatively uninformed.

There are other resources, e.g. at Skeptical Science.

Arthur said...

I would recommend David Archer's new book, "The Long Thaw", which I just finished. It goes over the long-term Milankovitch cycle and longer term geological processes under which the planet breathes CO2 in and out, to some degree. There actually are reasons why CO2 would "lead" on geological scales: changes in exposed land features and volcanism can bring about large ups and downs in CO2 levels, with consequent impacts on climate, apart from any orbital forcing. Anyway, pretty interesting.

And Archer's main point in the book is a good portion of fossil CO2 will be there for hundreds of thousands of years after the present "spike" is finished.

Steve Bloom said...

Just to be clear, everything I said pertained to the ice age cycles. Re the longer term Arthur is of course completely right, although I've never heard a denialist attempt to make an argument based on that.

EliRabett said...

Wait

John Mashey said...

Arthur:
so, put a review at Amazon.
My review there is a little lonesome by itself.

Anonymous said...

About the Milankovich picture, it looks wrong: the Earth orbit is an ellipse with the Sun at one focus, not at the centre.

As it looks now, you would think there are two perihelia and two aphelia...

:wq

Anonymous said...

wq

The earth's orbit is very close to a circle (just slightly elliptical), so for all intents, the sun is at the center. The center of mass of the earth-sun system is actually inside the sun.

If the elliptical orbit of the earth were drawn to scale, I doubt you would even be able to tell it was not a circle.

It has been exaggerated for effect in that picture, since the elliptical nature of the orbit is critical to milankovich cycles.

jg said...

Professor Rabett,
Please allow me one last chance to fix my first impression.
1. I meant to share an interactive illustration that is related to the theme of this topic. It shows the three major orbital changes over time. My intention is to create an illustration that allows lay people to easily visualize the effect of orbital changes which in turn should lead to a demonstration of CO2 and feedbacks. I failed miserably at posting a link, but learning from others, here's my last try: illustration.

2. I thank Arthur and Steve for their comments and will be buying David Archer's book, but I didn't mean to cite the "Warming leads CO2" myth. Rather, I meant to say that I often try to correct writers in local media and industry trade journals who tout common denialist themes, and if I "lead" that is "start" with global warming, CO2, or greenhouse gases, it creates an obstacle. So I'm hoping to explore a more neutral approach with the astronomy angle, hence my interest in this post and my gratitude for the link to the IPCC chapter.

Again, I'm grateful for the time you and others put into these blogs.

JohnG

Anonymous said...

Pravda appears to have made the jump from Communist Party rag to supermarket checkout line rag"

The really sad part is this: compared to some of the stuff coming out of the "most respected" mainstream media in this country (Washington Post, NY Times) over the last 8 years -- eg, pre-war reports on Iraqi WMD, based on impeccable sources like "Curveball" (and his twin brother "Screwball"), Pravda does look like the Truth.

if Pravda is right there next to the national Enquirer in the supermarket checkout stand, then so are most of the newspapers in this country.

Sad, but pravda.

Anonymous said...

Anonymous,

but there is only one perihelion right? Not two as I see in the picture. Exaggerate all you want, but Kepler Was Right(tm).

Anonymous said...

...and anyway, the quantity 'E' isn't actually the eccentricity, which is e=sqrt(a^2 - b^2)/a. In the picture it looks like (but isn't actually said I grant) E = a - b.

:wq