Useful piece in the Independent today.
The only alternative to man made GHGs as the explanation for the the global warming that we observe is the solar theory.
A study in 1991 by Friis-Christensen which showed a correlation between earth temperatures and the length of sunspot cycles. However, sunspots only increase solar intensity by 0.1%, so Christensen and Svensmark wrote a further paper in 1998 that added in an hypothetical effect of cosmic rays, which they argued would seed clouds, leading to cooling by increased reflectivity.
Peter Laut reworked their data, and pointed up mathematical flaws in their work. Other climate scientists endorse his criticisms. It is now agreed that sunspot activity is falling rather than rising, while temperatures continue to rise. This leaves CO2 as the only explanation for the continued rise.
Christensen now accepts that the 1991 study is now invalid, according to the Independent (paper version, 14th Dec 2009), although this is not certain. The link between cosmic rays and clouds is being studied, but latest data shows that cosmic rays are going up while cloudiness is going down - which contradicts Christensen's hypothesis.
More links provided by Student on the Daily Mail debate:
Lockwood and Frohlich: "we conclude there is no credible way that the recent rise in air surface temperature can be attributed to solar effects"
Erlykin, Sloane and Wolfendale: "we deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to this activity is ~<14%>
Useful BBC summary of recent work which refutes the cosmic ray/cloud hypothesis here.
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4 comments:
The Independent article says:-
"Messrs Svensmark and Friis-Christensen stand by their studies and continue to believe there is evidence to support their sunspot theory of global warming, despite the doubts first raised by Laut."
You write:-"Christensen now accepts that the 1991 study is now invalid."
Can you point me to where Friis-Christensen accepts the 1991 study is invalid?
All I can find are rebuttals of the Peter Laut analysis.One is by Svensmark and the other by Friis-Christensen&Svensmark together. (I think they are both at the website of the Danish Space Research Institute).
I am not as good with the internet as perhaps I could be, so maybe I am looking in the wrong places.
If those rebuttals still represent those authors views are you going to link to them in your blog post in the interests of fairness?
JMac.
JMac
(I have a feeling that I should know you)
the statement is in the Indie, Mon 14 Dec. p 9, by Steve Connor; i cannot find it in the on-line version:
"F-C now accepts that any correlation between sunspots and GW that he may have identified in the 1991 study has since broken down. There is he says a "clear divergence" between sunspots and global temps after 1986, which shows that the present warming period cannot be explained by solar activity alone".
It's in a newspaper, so it could be wrong.
If you have the link, I will post it.
So when composing this post in which you mention two scientists who are continuing to publish peer-reviewed papers relating to the role that the Sun plays in influencing the Earth's climate, didn't it occur to you (in the interests of the fairness, neutrality and rationality that you claim to try to achieve)to see if they have anything to say about the situation.
(I don't know if this link will work, but this is the relevant URL).
http://www.space.dtu.dk
/English/Research/Research_divisions/
Sun_Climate/Publications_full_text_SC.aspx
JMac
When using Peter Laut as a source one should be aware that he was for many years a paid lobbyist for the Danish government:
http://www.pepke.dk/BerlingskeTidende.pdf
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