Saturday, November 28, 2009
Post Corrections in Comments
Some of our readers have been kind enough to write to us with corrections to our humble document, Climate Analysis. We'd like to receive further corrections and answer further questions here at this blog. We invite you to send both to the comments instead of to my e-mail address. Instead of sending large files directly to me, please post links to the files into the comments section.
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I don't think Kevan has made it clear what the opposing (orthodox and heterodox) positions (or theories) are regarding the glacial/interglacial interaction of temperature and CO2.
ReplyDeleteBoth theories attribute the primary impetus for the onsets of both glaciations and deglaciations to regular variations in the earth's orbit and in the tilt of its rotational axis. These regular variations are known as Milankovich cycles after the Serbian astrophysicist and geologist who explained in the early 20th century how they could affect the earth's climate.
There is no dispute between orthodox and heterodox climate scientists that Milankovich cycles are the initial drivers of climate change between glacial and interglacial periods. This is made clear by evidence from ice cores which indicate that there is always a delay of approximately 800 years after a change in atmospheric temperature (T) before the corresponding change in atmospheric carbon dioxide (CO2) content.
How then do the opposing theories differ?
The orthodox theory, which is supported by the International Panel on Climate Change (IPCC), maintains that the Milankovich-driven temperature changes merely start the ball rolling, and that as soon as the CO2 content of the atmosphere has increased (or decreased) this increases (or decreases) the natural greenhouse effect and thus causes a further increase (or decrease) in temperature, which leads (with the appropriate delay) to further increase (or decrease) in CO2 and so on and so on.
According to the orthodox theory, a significant part of the warming and cooling associated with glacial-interglacial transitions should thus be attributed to CO2 variations, and the Milankovich cycles act merely act as a 'pacemaker'. Such a process is an example of 'feedback'.
Mathematically the postulated feedback process is feasible, and physically one would certainly expect some finite feedback as CO2 is without doubt a natural greenhouse gas. However this is not the same as saying that the feedback was necessarily significant.
The heterodox theory, which is more prominent on the internet rather than in print literature, is that one needs no significant feedback to account for the CO2 changes; the Milankovich-driven T changes are sufficient to account for all the variation in atmospheric CO2; as the T rises the oceans slowly warm up and as all gases are less soluble in warmer water CO2 is expelled from the oceans into the atmosphere. During cooling episodes the reverse process occurs, drawing CO2 from the atmosphere back into the oceans.
The heterodox theory does not exclude CO2 feedback from involvement in glacial-interglacial transitions. It simply sees no need to allocate CO2 feedback a significant role
That's the position as I see it at this moment, anyway. I'm still learning about climate science, having been introduced to it only a little over 3 years ago. As a newcomer I must admit to being surprised at the depth of scientific disagreement even regarding fundamentals, as well as by the apparently weak grasp - even by many scientists who I would expect to know better- of the scientific issues involved.
The dog ate global warming! (or was it Phil 'The Shred' Jones?)
ReplyDeleteDr Phil Jones, head of the Climate Research Unit at University of East Anglia, has been in the news recently after the hacking of his e-mails. It seems Phil has been busy with his shredder and deleted a lot of raw data. Not really best practice, Phil!
From http://pielkeclimatesci.wordpress.com (the blog of Colorado climate scientist Roger A Pielke Snr) November 28, 2009
News Release In The Sunday Times By Jonathan Leake – Climate Change Data Dumped
There is a news release in the Sunday Times by Jonathan Leake titled “Climate change data dumped” [Note: the Roger Pielke referred to in the article is Pielke Jr]. This startling disclosure means that climate scientists will be unable to assess the mathematical methodology that CRU has used to convert the raw temperature data to the adjusted temperature data that were reported (at least up to the 1980s) in the 2007 IPCC assessment.
The article includes the text
“SCIENTISTS at the University of East Anglia (UEA) have admitted throwing away much of the raw temperature data on which their predictions of global warming are based.
It means that other academics are not able to check basic calculations said to show a long-term rise in temperature over the past 150 years.
The UEA’s Climatic Research Unit (CRU) was forced to reveal the loss following requests for the data under Freedom of Information legislation. “
The data were gathered from weather stations around the world and then adjusted to take account of variables in the way they were collected. The revised figures were kept, but the originals — stored on paper and magnetic tape — were dumped to save space when the CRU moved to a new building.”
As also written in the news article “In a statement on its website, the CRU said: “We do not hold the original raw data but only the value-added (quality controlled and homogenised) data.”
This is an absurd claim that the new data is “value-added”. Indeed, we document a number of unresolved issues with the surface temperature data, which CRU now prevents anyone from assessing[,] in our paper:
Pielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res., 112, D24S08, doi:10.1029/2006JD008229.
The claim in the article [regarding] elimination of the data up to the 1980s, however, suggests that raw data since that time period is available. This data needs to be independently scrutinized (i.e. not by GISS or NCDC) and each step of their “quality control” and “homogenization” quantitatively assessed [of course, GISS and NCDC should have the raw data prior to the 1980s].
Dear Hugh, Thank you for your explanation of the Milankovich Cycles. I have added a link to your comment from my brief aside on the subject in Climate Analysis. I can't think of an experiment we could perform in the lab to measure the size of this positive feedback. A theory that cannot be disproved in the lab is not much fun, so far as I'm concerned. Now, the theory that CO2 comes out of warm water is an entertaining one, easily demonstrated to one's children in the kitchen. That's my kind of theory.
ReplyDeleteDear Hugh,
ReplyDeleteWith respect to your post on Climategate, I'll write a short post on that in a moment. In future, you can save yourself the trouble of copying the text of an article into the comments by placing a link to the text in the comment. Like this:
<a href="http://pielkeclimatesci.wordpress.com">link</a>
which will come out like this:
link
A bit cryptic, but the most reliable way to insert links.
Kevan
Dear Kevan,
ReplyDeleteA disadvantage with using this link is that such a link leads not to the article of interest but to the most recent article posted on the blog. As Roger Pielke Snr posts 1 or 2 articles almost every day the article of interest rapidly becomes inaccessible without prolonged search. That is why I copied the whole content. It is also quicker and less error-prone than typing out the whole URL.
Hugh
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ReplyDelete