2010-08-11 02:56:08Basic rebuttal for 36: "It warmed before 1940 when CO2 was low" REVISED
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
80.42.213.135
It warmed before 1940 when CO2 was low

The climate at any one time is affected by several factors which can act independently or together. The main factors include solar variability, volcanic activity, atmospheric composition, the amount of sunlight reflected back into space, ocean currents and changes in the Earth's orbit.

Before 1940, the increase in temperature is believed to have been caused mainly by two factors:

  1. Increasing solar activity; and
  2. Low volcanic activity (as eruptions can have a cooling effect by blocking out the sun).

Other factors, including greenhouse gases, also contributed to the warming and regional factors played a significant role in increasing temperatures in some regions, most notably changes in ocean currents which led to warmer-than-average sea temperatures in the North Atlantic. Does this mean that solar activity is also primarily responsible for late 20th century warming? In short, no. Solar activity since the 1950s has been relatively stable and therefore cannot explain recent trends. Similarly, increased volcanic activity may actually have had a cooling effect in recent decades. On the other hand, greenhouse gas concentrations, which were relatively low pre-1940, have increased considerably and are now dominating the climate system. This highlights the need to look at all factors when determining which factors are likely to be affecting climate at any one time.

In short, there's no reason to assume that because the sun was responsible for early 20th century, it is responsible for all warming. The evidence strongly suggests that current warming is mainly the result of increasing greenhouse gas levels.

 

2010-08-11 03:19:51Notes of rebuttal
Robert Way

robert_way19@hotmail...
24.224.230.112
Hello,
I think it is important to note that the warming of the 1940s is also extremely well correlated with the atlantic multidecadal oscillation and that explains why north atlantic regions (such as greenland) had such large temperatures during that time.

Also although all the factors you say are indeed things which affect climate, you may need to think of different ways to say it as the general public don't know what things like milankovitch cycles are. Also note we are in a phase right now of an extremely positive AMO and it certainly plays a part in the current warming. I say best bet is to say early 1940s is natural and likely had the mechanims you indicated but that recent warming shows an ever increasing co2 contribution as well as natural contributions.
2010-08-11 18:47:32
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
80.42.213.135

Hi Robert,

 Thanks for the input. I agree on certain points - I need to try and explain the Milankovitch cycles (though I might just say that they affect incoming solar energy to keep it simple) and I need to make the combining of factors more clear.

 I'm not sure about including AMO since it is effectively a regional phenomenon. Also the intermediate rebuttal doesn't mention it, and the IPCC did conclude that solar activity was the most likely factor driving early 20th century change. I guess I'm trying to keep it consistent - does that make sense?

 

2010-08-12 04:06:38Hello again
Robert Way

robert_way19@hotmail...
24.224.230.112
Hello Bioluminescence

I addressed the AMO topic here
http://www.skepticalscience.com/thread.php?t=7

I think with respect to the milankovich cycles you could just say "changes in the earth's orbit"

"The main factors include solar radiation, volcanic activity, greenhouse gases, changes in the earth's orbit and changes in ocean currents. Many of these factors can act both independently or can be linked. "

Before 1940, the increase in temperature is believed to have been caused mainly by three factors:
1. Increasing incoming solar radiation
2. Less Volcanic Activity (Eruptions can block the sun causing cooling); and
3. Changes in ocean currents causing warmer sea surface temperatures in the North Atlantic

Early 20th century in now nearly certain to have been primarily caused by these natural contributors. Increasing solar radiation has become viewed as the most important of these contributors but doesn't that mean that late 20th century warming could be caused by solar as well? In short, no. Solar activity since the 1950s has been relatively stable and therefore cannot explain recent trends. Similarly, volcanic activity may actually have had a cooling effect in recent decades. On the other hand, greenhouse gas concentrations, which were relatively low pre-1940, have increased considerably and are dominating the climate system. This highlights the need to look at all factors when determining which factors are likely to be affecting climate at any one time.

Just an idea. Somewhere between the two we can surely find some compromise

2010-08-12 23:29:19Milankovitch cycles, AMO and editing Intermediate Rebuttals
John Cook

john@skepticalscience...
121.222.17.49

I second Robert's recommendation - for a basic rebuttal, I'd generally opt for "changes in Earth's orbit" whenever talking about Milankovitch cycles. That's all people need to know at the introductory level.

Re the AMO, I don't include any info about the AMO in my intermediate version. Robert, I don't suppose you'd be willing to write either a blog post on this or an amendment to my existing intermediate rebuttal?

And let me just say to all authors that my intermediate rebuttals are not off-limits. If you think they need to be edited, added to or just completely rewritten, I'm more than happy to look at it. Many of those rebuttals were written a few years ago and are in sore need of updating or rewriting but I just don't have the time. So my feelings won't be hurt if you want to tell me my rebuttal sucks and needs a serious overhaul. If you rewrite the whole thing, I'm happy to replace it and of course, you'd get credit for the rebuttal.

2010-08-13 00:51:25response to john
Robert Way

robert_way19@hotmail...
24.224.230.112
Hello John,

pertaining to the AMO... I'm a little hesitant to do a post on the AMO at this point. Not because I feel incapable but rather because I am working on a paper which analyzes climate forcings in a certain regions and i'm waiting to hear back about my results from a colleague. Once I get that finalized and hopefully accepted somewhere, then I will be feeling that the analysis has reached a sufficient level to put it up here. I've seen a lot of analysis though by other individuals who put together AMO, Solar and CO2 forcing and find that it explains 99% of the trends over the 20th century. Interesting work actually.

I'm going to send you a very interesting post by David Benson over at real climate. He did some analysis that is extremely interesting and weirdly hasn't been followed up on much. One of the links he shows is here :

http://bartonpaullevenson.com/Correlation.html


but the main post i'll send via email.


Back to what we were talking about. I will in the future try to become more active with this stuff however. I think it is something that is important to work at and some of the intermediate explanations have subsequently been re-affirmed in later posts but updates have not been done to the original. One in particular I can think of is that the surface temperature record is unreliable, which is addressed by the post which compares all the different methods and reconstructions of temperature that all show the same claims.


2010-08-13 03:42:47
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
80.42.222.121

How about I stick to two main factors and add something along the line \"In addition, other factors played a significant role in increasing temperatures at a regional level, most notably the AMO which in its positive phase caused the Arctic and North Atlantic to be particularly warm\".

My thinking here is that it is effectively a regional effect - if I start specifying one regional effect I have to go over all of them. Also, interestingly - unless I'm mistaking the meaning of the article you, Robert, link to on the bipolar seesaw of the Arctic and Antarctic surface air temperatures - a positive AMO is linked with a cooling effect on temperatures in the Antarctic. I'm going to see whether I can get access to this article somehow - it's actually quite interesting.

I still can't copy and paste on here using Firefox - am I being particularly thick? - so I'll be typing my amended rebuttal in a bit. Thanks for the input :)

2010-08-13 03:47:42
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
80.42.222.121
I've just seen the Edit button - hurrah! The original post has now been edited.
2010-08-13 05:47:41Bioluminescence
Robert Way

robert_way19@hotmail...
142.162.181.139
If you want the article I can send it to you. my email address is rway019@gmail.com

With respect to the AMO comment, yeah you can add what you just said in except revise it to be \"In addition, other factors played a significant role in increasing temperatures at a regional level including warmer than average North Atlantic sea surface temperatures due to ocean currents\"

Yeah according to the article the AMO causes a seesaw between the two. But the thing is that this is not necessarily a matter of just redistribution of warmth because there are positive feedback mechanisms and so on. One interesting thing I saw and noted was that Mann et al. 2009 show that there was a positive phase of the AMO predominantly during the Medieval warming period. That to me explains how the north atlantic sector was so warm during that time. That all being said he grazed over it and talked about another indices instead... I think one thing that might be true (and I say might) is that the AMO probably affects the north more than the south somehow. Who knows though.   By the way you can copy with firefox... just press control c  to copy and control v to paste

If you ever need any other articles. I probably have them haha... Some of us hoard different things I guess.
2010-08-13 07:21:17
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
80.42.222.121
Excellent, I'll be dropping a line very soon. Thanks again.
2010-08-15 16:26:35On duplication
gpwayne
Graham Wayne
graham@gpwayne...
81.152.239.255

Hi Bio - I just made a commment on your entry for No. 33 - 'It cooled mid-century' and when I read this again, I was struck by the apparent duplication. This comes about, I believe, because two arguments in the original list refer to much the same phenomena.

Thing is - and this is just a suggestion for discussion - considering that what you wrote here applies to No. 33, and vice versa if we are not too strict with ourselves, would it be useful to write one basic rebuttal for both items and post it twice? After all, both denialist arguments are based on the same faulty premises.

2010-08-15 19:37:21
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
212.139.87.36
Hello again Graham - aye, there is some duplication I guess, but the focus of each post is different from the other. I see where you're coming from though, I guess that's going to be John's decision. I'm going to work on my rebuttals today - I've been concentrating on some translating but I'm going to try to finish both the rebuttals today (before subjecting myself to the probable pain of a new season). Thanks for the input :)
2010-08-17 02:41:51
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
80.42.219.219
Updated. I think I've taken everyone's comments on board.
2010-08-17 15:05:50Ready
doug_bostrom

dbostrom@clearwire...
184.77.83.151
Ready to release from captivity.
2010-08-17 17:16:47Open the cage
gpwayne
Graham Wayne
graham@gpwayne...
86.156.59.156
Oops - picked up on Doug's wildlife analogy...but thumbs up from me Anne-Marie. Good job!
2010-08-18 01:23:32Comment
Robert Way

robert_way19@hotmail...
24.224.230.22
Good to go
2010-08-18 17:54:48
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
80.42.219.219
Shameless bump.
2010-08-19 16:50:49
Ari Jokimäki

arijmaki@yahoo...
192.100.112.211
Go ahead.
2010-08-19 17:04:57Great stuff
John Cook

john@skepticalscience...
121.222.17.49
Great work, Anne-Marie and everyone with feedbacks. Will post it shortly, the 5 thumbers are coming so quickly, hard to keep up! It's really warming my heart seeing this fantastic collaboration, it's so effective and efficient, I'm just amazed at how well this forum is working :-)
2010-08-20 12:30:40Typographical error
James Wight

jameswight@southernphone.com...
58.105.164.221
I think you meant to say “In short, there’s no reason to assume that because the sun was responsible for early 20th century warming, it is responsible for all warming.” Otherwise it's well written.
2010-08-20 18:48:04Twitter title suggestion
gpwayne
Graham Wayne
graham@gpwayne...
217.44.86.17
A century of two halves: heat before 1940 caused by energetic sun or lazy volcanoes?