2011-06-25 18:49:58Milankovitch Cycle posting
Chris Colose

colose@wisc...
69.86.130.70

I just wrote this up today.  jg signed up for this topic but I offered my help, so if he (or anyone else) wants to make a contribution or turn things around, let me know.  For example, I left out all the historical stuff behind Milankovitch cycles (which as SteveBrown noted before, goes back before Milutin Milankovitch). 

Also, if someone can verify that Figures 6 and 7 are showing up fine, that would be appreciated (I had to upload them from my site since the SkS image uploader was not behaving for them)

http://skepticalscience.com/Milankovitch.html

2011-06-25 19:19:39
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.16.30

I get "file not found" clicking on your link.

2011-06-25 20:04:54
Chris Colose

colose@wisc...
69.86.130.70

Sometimes that happens to me if I somehow get kicked off, and need to login again.  Could that be the issue? Otherwise, I'll need someone to tell me what the issue is.  I uploaded it fine via "Add New Blog" at Author Admin and can preview it fine.

I'm signing off right now but will be back later...

2011-06-25 20:53:23
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.16.30

Hmm....I wonder what it is with your computer?, we've had issues before. Then again, could be something entirely different. 

2011-06-25 21:14:40File not found
John Cook

john@skepticalscience...
121.222.9.229
How blogs work is if they're unpublished, only SkS authors can view them. If you're not logged in, the site doesn't know you're an SkSer so it gives you the file not found error.

if you want your blog post to be visible to nonSkSers before it's published, set the status to embargoed. If you're a pending author and don't have access to that feature, email me at john@skepticalscience.com and I'll upgrade you to full author status.

2011-06-26 01:25:15
dana1981
Dana Nuccitelli
dana1981@yahoo...
71.137.108.93
I get file not found too...
2011-06-26 01:54:47
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Chris, this is a excellent post, and you've answered a few questions I had planned to ask you. I especially like how you expressed the uncertainty of the trigger for glacial changes in your summary.

I had a very different level and approach in mind when I started this topic. The topic has great illustrative potential that I wanted to explore .  For example, I haven't seen any explanation of climatic precesson on the web that captures the elegance of why it's a sine * eccentricity calculation, a great point at which to bridge ones intuitive spatial awareness with the math one should have learned in school; in otherwords, I wanted to take each of these components and make people think "why didn't I learn that in school", which was my reaction when I started studying this stuff.  -- of course, this assumes a different target audience.

It's probably best to show what I have in mind, which I'll do as I continue to work on Steve's Eemian illustrations, and Rob has giving me a suggestion too. This will take time, so don't let me hold up this post. However, I would like to rework some of the pixelated diagrams you've used, but  won't be able to get to that until tomorrow. Let me know what I can do.

thanks,

jg

2011-06-26 02:22:36
Chris Colose

colose@wisc...
69.86.130.70

I just emailed John.  Hopefully we'll get this sorted out.  I don't want this post viewable to the world yet, only to SkS admins/authors for review.  I didn't have problems that in my previous posts (just posting graphs and stuff).

2011-06-26 02:43:00
dana1981
Dana Nuccitelli
dana1981@yahoo...
71.137.108.93

Now I can see it.  Looks good to me after a quick skim.

2011-06-26 04:36:17
Riccardo

riccardoreitano@tiscali...
93.147.82.166

I coud read the post using the url http://www.skepticalscience.com/Milankovitch.html as opposed to the one without www at the begining.

The post looks good, I'd only add the label in fig. 1 to make the reading of the curves easier.

2011-06-27 08:44:43
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Chris,

would you like some less pixelated versions of the illustrastions in your post?

 

plane of Earth's orbit

2011-06-27 10:44:17Know thy audience...
John Hartz
John Hartz
john.hartz@hotmail...
98.122.98.161

Chris,

I have the same reaction to your draft as I did to Steve Brown's initial draft of Part I of his Last Interglacial article -- its way too much science-speak and consequently will not be understandable to the average person. You did not write this article for publication in a peer-reviewed scientific journal.

You lead sentence of the article is an example of what I mean:

It is now well accepted that astronomically-induced variations in the solar insolation that reaches Earth (with quasi-periodicities lying between tens and hundreds of thousands of years) have a strong impact on Earth’s climate, serving as the pacemaker for the glacial-interglacial cycles over the Quaternary.  

If the reader doesn't know what the word "insolation" means, the entire sentence is incomprehensible.

Other phrases/words that the average person will likely not understand are "astronomically-induced variations," "quasi-periodicities," and Quatenary.

That's just way too much jargon for a lead sentence.  Break it up into smaller junks and use plain English. Every scientific term used should be defined the first time it appears.

I also suggest that the phrase, "it is now well accepted that..." is not a particularly good way to start a sentence. 

Short declarative sentences are much easier to understand than long complex sentences.

In addition, avoid using the word "that" more than once in a single sentence. 

2011-06-27 14:40:46
Chris Colose

colose@wisc...
69.86.130.70

jg,

 

Thanks, I like your graphs.  I'll probably modify the third graph just a bit to include the line that cuts vertically through the center of the Earth (as in my image).  By the way, where do you create your images? I usually use Paint for those kind of things, but yours look like better quality.

Badger, your point is well taken, and I'll try to play with wording a bit. Sometimes though, the "jargon" is unavoidable, especially when communicating more of the physical science rather than the politics (presumably scientists created the jargon so that they wouldn't have to say things in two sentences what could take two words).  I did define "insolation" in the article but I could do it earlier.  I also linked to an article explaining what the Quaternary is, but I can put dates in parantheses.  If you have other advice I'll think about changing some stuff around.  I don't have the best perspective on what is readable to the "lay person" here because I've been looking at this kind of writing for years.  I suppose that is the problem in our field though.

I'm also not one to sacrifice accuracy, although I completely agree that the more readable it is, the better.

2011-06-27 19:22:44
nealjking

nealjking@gmail...
84.151.47.226

The last time we had a general discussion on style and level, the general feeling was to aim for an 8th-grade reading level: That's what PR folks generally aim for. It's difficult, but if we just write what's scientifically precise, our message will zing off the upper atmosphere.

A useful tool (there are others) can be found at:

http://www.standards-schmandards.com/exhibits/rix/index.php

2011-06-28 00:16:11Re: illustrations
jg
John Garrett
garrjohn@gmail...
108.23.2.2

Hi Chris,

I updated the illustration of the orbit's plane to include the lines I omitted. My illustrations are in Adobe Illustrator format, and corrections are easy to make. Feel free to ask me to make any corrections, or do any modifications you wish on your own. I can provide pieces to work with. Also, if you have any custom illustrations in mind, please ask.

jg

 

2011-06-28 01:45:18Chris
John Hartz
John Hartz
john.hartz@hotmail...
98.122.98.161

Thanks for the positive feedback. I was concerned about how you would perceive my crtique.  I purposely didn't pull any punches.

I know from personal experience how difficault it is to transform technical stuff into something that the average person can easily comprehened. It took me years to master it.  

In this case, just pretend that you're writting the article for posting on the Discovery Channel or Climate Central.

2011-06-28 06:19:04
Steve Brown

brownsg@gmail...
80.177.115.133

Chris - This is a good draft.  I like how you've placed emphasis on the other planets too.  As Badger says, some of the jargon should be softened.  I'm wondering if it's worth doing a "simple" version and an "advanced" version in the same way that rebuttals have been done.  Another suggestion would be to include a mention of how we can "see" Milankovitch cycles at work with spectral analysis of ice cores and varved sediments.

I'm also wondering if we should actually work on an ongoing series of posts on core subjects in climate science to back up the regular posts and rebuttals.

2011-06-28 06:36:54
nealjking

nealjking@gmail...
84.151.47.226

The leading paragraph has reading level of grade 17: very very stiff.

2011-06-28 07:42:05
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.6.15

The content of this post is excellent despite the language. A simple and advanced version, as suggested, would be the go. You gonna have a crack at the basic version Steve?

2011-07-06 12:08:11
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Chris,

I did a basic post on this topic here: Orbital Forcing. My draft is not complete but I think there's enough there to assess whether we use it or use pieces of it (e.g., some illustrations in current or modified form) in your post.

thanks

jg

2011-07-10 05:22:05
Chris Colose

colose@wisc...
69.86.130.70

Guys, I have updated the Milankovitch post, to clean up the first couple paragraphs and put in new images (thanks to jg).

jg-- I like the idea of a "simple post," although yours may actually still be too technical for that purpose, but others can judge that.  This is a hard topic to do any judtice to while still keeping it "basic" and readable (especially with the precession cycle I find).  I haven't read through it with a fine-toothed comb, but it looked pretty good.

2011-07-10 07:23:12
Andy S

skucea@telus...
66.183.187.28

Excellent post, Chris and fantastic graphics jg.

I like the draft of jg's post, too. Different words and new graphics are always a help in improving understanding. I appreciated the historical comments.

I, too, get justifiably criticized here for using  too much science-speak and I find it really tough to simplify my language. I appreciate the feedback from other people here, especially when it's specific.

2011-07-11 01:20:52
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Chris, 

I'm going through your post, and I'll post comments as I encounter questions. First one: I don't understand the graph of insolation values. If 60N is red and 60S is orange, why don't the two cross over each other as the precession cycle changes which hemisphere's summer gets closer to perihelion? Is June a fixed value such that June always means solstice for the Northern Hemisphere (and therefore Dec always means solstice for the south)?

jg

2011-07-11 02:17:43
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Chris,

While reading the part on extreme tilt, and that such a tilt would create dual summers for the tropics, I had to sketch a picture to understand what you said. Since I did that, maybe others would like a picture too (the hypothetical planet shown here is pangea, though no one would notice as this size):

extreme tilt

2011-07-11 03:10:53
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Additional comments:

Comment 1) I'd move things around in your first Precession paragraph so the figure follows the North star comment and then lead into the precession/season description

"Precession: Precession does not describe how tilted the Earth’s axis is, but rather the direction of its axis.  This changes what star is the “North Star” over time (today it is Polaris, but near the end of the last deglaciation it was Vega)"

[Fig 4]

"More important to climate, precession governs the timing of the seasons as described below."

Comment 2) Regarding the paragraph preceding figure 5 that begins with "There are two key precession effects": The paragraph describes two motions that are different from motion shown in figure 5, so I'd insert a paragraph break and then describe what is going on in figure 5. As is, it may be easy to confuse precession of the semimajor axis with the swaying up and down of Earth's orbit shown in Figure 5. (Or, I may misunderstand this; Fig 5 is different from elliptical precession, correct?)

Comment 3) Typo: "perpendicular to he spin axis..." should read "the spin axis of the top" in this sentence:

"Obliquity and precession variations arise due to the torque exerted by gravity (i.e., a force that acts perpendicular to he spin axis of the top)"

Question) So, the variation of the precessional period (19k vs 23k) due to that tilt in the orbit shown in Figure 5? If yes, thank you for explaining it to me. Suggest that you add the "fig5" note:

Precession also varies due to the tilting of the Earth’s orbital plane, as shown above (Fig 5).

 

 

 

2011-07-11 03:23:18
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Comment 1) Just before figure 8, you say this: "in reality water vapor would help a lot too"

Could you clarify what you mean by this?

comment 2) typo: "so it the planet swings" should be "so if the planet swings"'

comment 3) Typo in last paragraph:"quesrions"

 

Your acknowledgement was very generous. Please tap me for additional illustrations, so I'll feel certain I earned such praise.

I love this post, especially in the paragraphs at figures 6 and 7. Fascinating.

Also, your comments (and those from Andy, Rob, and Steve) have encouraged to try again on the basic level post of this topic. I'll keep you apprised.

jg

 

2011-07-11 03:33:10
Steve Brown

brownsg@gmail...
80.177.115.133

You've done a great job on this Chris & jg.  If you were to flesh it out into several posts I could easily see it becoming a standard reference for Earth Science students.

2011-07-11 04:25:39
jg
John Garrett
garrjohn@gmail...
96.229.221.76

I like Steve's idea. What do you say Chris? The definitive series on this with lots of pictures. Here's another illustration to consider of a hypothetical high-tilt Earth:

super winter in N.H.

2011-07-11 04:58:00
Chris Colose

colose@wisc...
69.86.130.70

Thanks jg,

Concerning the insolation graph, keep in mind that the months are defined by seasons and so winter in the Northern hemisphere will never occur during June (sometimes I see that quoted); it's just that the months will correspond to different positions around the orbit over time.  This page has a decent, simplified discussion, and I might pull in another graph to show that.  Chapter 8 from this book has some good visuals which I might think about using, or that you can play with, let me know what you think

On the water vapor comment, I guess I assumed the reader would realize that it is a positive feedback, which reinforces warming or cooling.  The lack of virtually any water vapor when you get cold enough to be in a Snowball makes it difficult to get out of that state.  I'll modify that remark.

I will probably add a bit more detail to the precession discussion, to bring in some remarks about the solstice's and so forth.  As I said, I think precession is the most difficult to explain-- eccentricity and obliquity tend to be more intuitive for most readers, I find (including me). 

This topic could be expanded into two or three parts, although I'm not sure what subjects would be the natural dividing line between one post and another.

2011-07-11 05:08:32
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Hi Chris,

I'll look at the chapters later, as the rest of my day is tied up, but a quick thanks for sorting out my confusion on the june insolation graph.

jg

2011-07-11 05:10:10Chris
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
97.83.150.37

Still getting a "File Not Found" error message on your link at the top.  Do you have a different one than that?

2011-07-11 06:01:32
Chris Colose

colose@wisc...
69.86.130.70

Riccardo said http://www.skepticalscience.com/Milankovitch.html worked for him.  From John's comment before, if you are logged in as a SkS author, it should work...

2011-07-11 06:14:31
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
97.83.150.37

That one works.  The one at top lacks the www

2011-07-11 06:30:23www versus no www
John Cook

john@skepticalscience...
121.222.9.229

There are two things you need to understand about how SkS works:

  1. If a blog post hasn't gone live yet (and not set to embargoed), only logged in SkS authors can view it
  2. If you login at www.skepticalscience.com, you will not be logged in at skepticalscience.com. This is a little technical glitch - maybe when I get time I'll fix it (don't hold your breath, lots of higher priorities). So keep that in mind if you ever get the file not found error when viewing a yet-to-be-published blog post

If you want the ability to set your own blog posts to Embargoed, I can always upgrade your SkS account from Pending Author to Full Author. This gives you the ability to go live with your own posts - I always start SkS authors as Pending by default to give them a chance to get used to the blogging admin system.

2011-07-11 07:09:18
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.99.60

Give me a heads-up when you're ready to post this one, Chris.

2011-07-17 07:52:16
Chris Colose

colose@wisc...
69.86.130.70

I have just updated the Milankovitch post.

jg-- Do you have a good figure to show the axial wobble (the axial precessional variation)?  I think I want to split up Figure 5 into a 5a and 5b

Otherwise, this should be good to go, unless I made typos.  Please let me know.

2011-07-18 02:52:06
Steve Brown

brownsg@gmail...
80.177.115.133

Chris - jg is travelling and may not be able to respond for the next week.

2011-07-18 07:49:05
Chris Colose

colose@wisc...
69.86.130.70

That's fine, I'll tweek it...

2011-07-18 09:10:40
Chris Colose

colose@wisc...
69.86.130.70

Dana, I just updated everything, so it should be good now...

2011-07-21 02:57:09
logicman

logicman_alf@yahoo.co...
109.150.152.199

I like this article.

 

Suggestion:

Changes in the Earth's orbit brought about by astronomical variations have a strong impact on Earth’s climate.  These variations had been known for some time, but their influence had been generally discounted before Milankovitch formulated his theories.   They These changes serve as the pacemaker for ...

 

I suggest this change because the cycles were known about long before Arrhenius published his paper on CO2 in 1896.  I think the fact is important: the investigations which led to the determination that CO2 was the major driver of climate change were undertaken after scientists had come to believe that changes in orbital cycles were insufficient to explain the substantial climate changes that had been deduced from evidence of ice ages.  Many deniers seem to think that since Milankovitch's ideas came after those of Arrhenius, the CO2 theory is refuted.  The history of the science shows it to be the true case that the theory that orbital cycles might affect climate came before CO2 theory.

 

btw, the link is still broken.  This one should work:

http://www.skepticalscience.com/Milankovitch.html

2011-07-21 07:57:25
Chris Colose

colose@wisc...
128.183.2.130

logicman,

I think I am going to leave the history out of this one, but I can add a link to a relevant piece (perhaps one of Spencer Weart´s articles); I don´t really know of any skeptic arguments that focus on the one you stated, so it might just come off as a strawman, but I´ll throw in a few sentences about how orbital variations themselves are insufficient. 

2011-07-21 08:11:32
logicman

logicman_alf@yahoo.co...
109.150.152.199

Chris: that's fine - you already had my thumbsup.  :-)