The Intergovernmental Panel on Climate Change (IPCC) has stated that: Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations, mainly carbon dioxide. This conclusion is based on output from global climate computer models known as General Circulation Models (GCM).
David Douglass and John Christy, in a paper recently accepted for publication and already available on the internet, have come to a different conclusion. By considering observed, as opposed to modelled, temperature changes and at different latitude bands they conclude that:
1. El Nino and La Nina effects in the tropics have a more significant affect on global temperature anomalies than carbon dioxide, in particular it was an El Nino event that drove the 1998 global temperature maximum.
2. Variations in global temperatures since 1978 have mostly been due to climate effects in the northern hemisphere (northern extratropics) and these effects cannot be attributed to carbon dioxide.
3. Carbon dioxide has contributed a small amount to an increase in global temperatures but without what is commonly referred to as feed-back.
David Douglas and John Christy are practicing climate scientists from the Department of Physics and Astronomy, University of Rochester, and Department of Atmospheric Science and Earth System Science Center, University of Alabama, respectively. Their paper entitled ‘Limits on CO2 Climate Forcing from Recent Temperature Data of Earth’, was recently accepted for publication in Energy and Environment.
A regular at this blog, Cohenite, comments on the Douglass-Christy paper in a fairly technical note already posted at the community webpage of this blog, and entitled ‘Temperature Trends and Carbon Dioxide’, suggests that there is no evidence for a contribution from carbon dioxide to global temperatures and that the role of the sun has been underestimated.
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Robin and Gordon: " It’s good to know that the Loehle data are reliable, and collected by an expert. Thanks."
I think the important thing about Loelhe's data is that the proxies have been validated as actual temperature proxies. Tree rings are uncertain to be temperature proxies as there is a band where temperature is optimum above which there is slow growth.
Robin Edwards said..."I did try once, with “Weather” the journal of the Royal Meteorological Society... but the referee clearly didn’t like my conclusions..."
Peer review sucks. It's initial motivation was to keep nutcases out of scientific journals but it has now focused on supporting popular paradigms. Of course, Einstein would be rejected out of hand these days.
I've looked at your post, Jeff, and replied there. Really great stuff. Surely there must be a case for trying to construct something publishable in a mainstream climatological journal. If not, E & E would surely be pleased with it.
I've often contemplated writing something about the tendency of climate to change in steps from one regime to another. I did try once, with "Weather" the journal of the Royal Meteorological Society - must have been about 8 years ago, I suppose, but the referee clearly didn't like my conclusions, though the editor did! I don't think the ref understood what I was doing. Must use smaller words next time.
Cheers, Robin
Me too. I don't think that even Craig Loehle had access to that though. (Just guessing)
BTW: I just did a post which I used Mann's favorite CPS method to extract positive and negative hockey sticks from his groups own proxies.
I also demonstrated temp rises and falls in historic points as well as sine waves just for fun. All of it used the M08 group math and data sets.
http://noconsensus.wordpress.com/2008/10/11/will-the-real-hockey-stick-please-stand-up/
Thanks for your comment Jeff. It's good to know that the Loehle data are reliable, and collected by an expert. Thanks.
No doubt the true main signal is coming through after smoothing, tho' I'd still really like to see the untouched data!
Cheers, Robin
Robin Edwards and Gordon Robertson,
I also have checked some of Loehles work out. The difference between his papers on climate and others is that he isn't doing any post data sorting. Therefore smoothing just makes it easier for your eyes to see trends.
Not that smoothing is correct, all I'm saying is that smoothing hasn't affected the overall trend as in a Mann paper. The data were pre-calibrated and therefore scale was unaffected by smoothing.
His approach is pretty minimalist as far as typical data molestation in this field. Craig is a forester by trade so he has an excellent handle on tree growth. He has also recently issued papers on the non-linearity of tree response to temp.
As far as my two cents, these are the best representations of climate I can find. The number of proxies is not complete enough to draw conclusions from and the calibration was done by other scientists so I couldn't review that.
Gordon Robertson wrote "I'd be interested in your take on Loehle's work".
Well, I've downloaded it all, thanks to your link, and have to say I'm a mite disappointed! I can of course reproduce his conclusions about the MWP ad LIA by simply looking at the plot of his data. They look quite reasonably spiky, as one expects from anything related to climate, but when I looked at the cusum plot it was /instantly/ obvious that the data were not "as found", but heavily smoothed. This pretreatment is always recognisable from cusum plots merely from /their/ lack of spikiness. Then I read the summary of his paper - can't get at the whole thing - and saw that the data had all been treated by using a 30 year smoother. Unfortunately, this ruins what can be deduced from cusums about sudden change. That of course is what smoothing of any sort is all about! It is used to disguise unpalatable amounts of noise, disregarding completely the fact that the most interesting signal may be in the noise that the smoothing system takes out, and that we cannot know what the cause of the noise is. It could be old-fashioned iid "gaussian" with mean zero, but it could be a reflection of the vicissitudes of the complex and unforecastable things that are caused by the drivers of climate. Further, the more you smooth the greater are the problems with the start and end of the series. Inevitably you have to resort to guessing.
Another problem is "outliers". No doubt you've addressed this one, probably without reaching an acceptable conclusion. Again, in my software I've implemented a couple of procedures, but in reality the only reason for discarding data is knowing that it is in error from sources other than the data values themselves. A typical scenario is the transposing of digits, which happens to result in a "strange value", say 28 instead of a more reasonable 82. This stranger may indeed by picked up by suitable outlier detection techniques but if you don't contact the owner of the data with your suspicions you really have no proper grounds for rejecting it.
You'll guess that smoothing frustrates me. If I need it I can do it myself, but with a heavy heart. Simplification of real data for the convenience of those who choose not to try to understand that nature is not all smooth curves or linear models is an unwelcome aspect of current popular science, in my opinion. It tries to gear things to the level of science correspondents of newspapers, whose editors further manipulate them to form headlines, or to make them "understandable" to politicians, who are very seldom proper scientists.
So, where are the original data, I wonder. Those are what I'd really like to see.
Cheers, Robin
I would like to tip my hat and acknowledge that Cohenite has addressed my complaint over at Deltoid:
http://scienceblogs.com/deltoid/2008/10/the_australians_war_on_science_21.php
It seems that both he and I have a deficit of irony-detection at times, because my French revolution metaphor was taken by him in a way that I hadn't intended it to be taken, just as he was apparently being somewhat Socratic with his 'beacon' statement.
I withdraw my comment about mendaciousness, but I continue to think that Cohenite was being somewhat mischievous in his post above in not explaining the context of my comment. To be expected from a lawyer I guess, although I would have thought that the context of my comment would be passed on in any reference to my Deltoid post.
I would not have ever guessed that anyone would seriously suggest from reading my post that I was countenancing beheading and pass this message on to others, especially as in my mind I was referring to Monckton perhaps being tapped on the shoulder and told to be a little more circumspect in how he draws unfavourable attention to the UK peerage.
However I admit that my allusion to guillotines was a metaphor that could easily be misconstrued even by people not being mischievous, and that I should have been more explicit in the tenor of my intended meaning.
For future reference though, I do not support violence, and if anyone ever imputes such from any comment I make, whether clearly ironic or not, I suggest that they do so with reference to the context of any statement.
This is my Deltoid response:
-----------------
Cohenite.
Well spotted, but I was actually referring to the aristocracy dissociating themselves from their colleague lest they lose favour with the commoners and find a republic is a serious attraction to the UK public.
My very bad though for picking a metaphor that included the French revolution and 'beheading'. However, as a wise man once said, I thought my revolution comment "would be taken with the necessary grain of ironic salt; I stand corrected."
Seasoning aside, if the British blue-bloods persist in allowing such muddled-thinking amongst their 'best', the weight of history may one day not be able to prevent a dissolution of the country's current sociopolitical structure.
Comment from cohenite
Time October 6, 2008 at 8:59 am
"Bernard J, I see, over at Deltoid, is calling for Monckton to be beheaded"
Cohenite.
I have never suggested that Monckton be beheaded, nor have I implied any other violent act be perpretrated on Monckton. Nor have I described myself as "beacon of civilised discourse".
You are promoting mendacious lies.