2010-09-12 03:46:57ADVANCED 33: It cooled mid-century
dana1981
Dana Nuccitelli
dana1981@yahoo...
71.137.148.215
I put together an advanced rebuttal for "mid-century cooling".  I tried to quantify how much cooling aerosols caused during the period in question, but it was tough because aerosols have such a complex and not particularly well understood effect on the climate and global temperatures.  So I had to make some hand-waiving assumptions, but came up with a ballpark number.  Let me know what you think.
2010-09-12 05:10:37There's a nice graph
nealjking

nealjking@gmail...
84.151.46.1

I like to point people to, to show that the mid-century stall is not a failure of the theory but a confirmation:

http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/figspm-4.htm

It's from the 3rd IPCC report: I'm not sure if they reproduced it in the 4th report or not.

It shows the expected results assuming a) Only natural forcings; b) only anthropogenic forcings; and c) with both. Graph c) has a much better match to the observations than the other two.

2010-09-12 05:25:52good point
dana1981
Dana Nuccitelli
dana1981@yahoo...
71.137.148.215
Good point Neal.  I had actually thought about including a very simllar figure from Meehl et al. (2004), but decided just to link to the study.  It's easy enough to include the figure though, i'll do that right now.
2010-09-13 21:33:04Two possible inclusions in the advanced rebuttal
John Cook

john@skepticalscience...
121.222.93.62

Dana, this is entirely a judgement call but I've done two blog posts pertaining to mid-century cooling. Whether you want to include these depends on whether you think they add to the narrative or distract from it.

Firstly, the intriguing finding that nighttime temperatures actually rose during mid-century cooling, showing that "greenhouse warming was percolating away while we slept". Very telling study by Wild:

http://www.skepticalscience.com/What-happened-to-greenhouse-warming-during-mid-century-cooling.html

Secondly, the finding that ocean temperatures were slightly overestimated in the 1940s, exacerbating the subsequent cooling trend:

http://www.skepticalscience.com/A-new-twist-on-mid-century-cooling.html


 

I'd say the second bit of info is less important - regardless whether the cooling was partly a measurement artifact, the fact is, it was still a real phenomenon and global dimming was measured over this time. But the first result, warming nighttime, is a fascinating result (read the comments to that blog post).

2010-09-14 05:16:22good point
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.249
That's a good point - I'll add something about the nighttime warming.  The measurement artifiact is a good piece of information, but it's hard to fit into the article the way I wrote it.  It only makes a small difference in the overall trend during the period in question, and the trend is what I'm discussing.
2010-09-14 05:41:58Charlson 1991
Riccardo

riccardoreitano@tiscali...
93.147.82.69

There's a good old article on scattering by sulfate aerosol that might be of interest. I'm not sure it can be of any use to come up with a simplified enough treatment of scattering but ... you have choosen such an intricate topic ...  ;)

 

http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0870.1991.00013.x/pdf

2010-09-15 04:24:47nice article
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.249
Thanks Riccardo, that's actually a very helpful paper which will allow me to be a little less hand-waiving and more precise.  Much appreciated!
2010-09-15 11:36:09Let me know when you're happy for this to go live
John Cook

john@skepticalscience...
121.222.93.62
When you're ready, give the word and I'll blog post this one.
2010-09-15 17:01:20Small corrections
nealjking

nealjking@gmail...
84.151.32.54

- Figure 2 is a bit fuzzy: Can you find a crisper version?

- caption for Figure 2: "aerosols radiative mechanisms"

=> "aerosols' radiative mechanisms" [add apostrophe]

- "the total (direct + indirect) anthropogenic aerosol radiative forcing"

=> "the total (direct + indirect) anthropogenic radiative forcing due to aerosols" [too many adjectives strung along without a break]

- "Where FR is reflected solar flux,"

=> "where FR is reflected solar flux,"

- "∂ is the optical thickness"

=> "δ is the optical thickness" [you can get Greek letters using Insert/Symbol in MS Word]

- "FR is approximately 32 times the optical thickness ∂."

a) First, the units are wrong: FR has the units Watts/m2, whereas optical thickness is dimensionless. What do you really mean?

b) Secondly, "∂" => "δ"

- "Despite this uncertainty, they remain the likely dominant cause of slight the mid-20th century cooling."

=> "Despite this uncertainty, they remain the likely dominant cause of the slight mid-20th century cooling."

 

dana1981: It occurs to me that the language in the "Empirically observed fingerprints of anthropogenic global warming" could be altered to emphasize that the warming in the night persisted through the cooling period of the mid-century. (Try explaining that with cosmic rays!)

 

2010-09-16 04:28:08thanks neal
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.249

Thanks neal, good comments, which I incorporated.

Unfortunately I can't make Figure 2 any clearer.  It's a very wide image, and we're supposed to keep it down to 500 pixels in width.  I took it straight out of the referenced IPCC report though, so people could click the link if they want to see a clearer version.  Maybe JC can work his magic and see if he can improve it.

As for FR, the '32' isn't unitless.  That's just the approximate value that comes out when inputting the empirical numbers for the other variables in the formula.  I could say "32 W/m2 times the optical thickness," but that seems more confusing to me than just leaving it as '32'.

Good point on the empirical evidence cross-reference.  I'll go back and add that point when I get a chance.

John, I'm happy with it at this point whenever you want to blog it.

2010-09-16 04:47:09OK
nealjking

nealjking@gmail...
84.151.32.54
go for it
2010-09-16 10:11:01Published
John Cook

john@skepticalscience...
121.222.93.62
Thanks Dana, great resource, this one. Nice seeing those sulfate emission graphs (hmm, never thought I'd hear myself say those words).
2010-09-16 14:31:20thanks
dana1981
Dana Nuccitelli
dana1981@yahoo...
71.137.148.215

Haha, thanks John.  This was a tough one but turned out pretty good.  So far the only negative comments are that I didn't talk about PDO, which I expected (skeptics are obsessed with 'natural cycles').  I just can't cover everything in one rebuttal, and PDO is pretty minor.  The title you gave the blog post was helpful since it did focus on aerosols.

Next up, Hansen '88, which should be pretty interesting too.

By the way, how do you decide which blog posts get onto Facebook?

2010-09-16 23:02:15
Riccardo

riccardoreitano@tiscali...
93.147.82.101

"This was a tough one but turned out pretty good."

I agree. And once more quoting your own words :)

2010-09-17 01:35:23thanks
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.249
Thanks Riccardo, and thanks again for that reference.  It was a significant improvement.
2010-09-17 06:48:22Facebook
John Cook

john@skepticalscience...
121.222.93.62
All the blog posts go on facebook. But it wasn't working when I posted yours so I had to wait till later.