2010-10-11 05:52:00The sun upside down


This is about Haigh et al. paper. It's my first try of such short posts, I almost just collated a few quotes from her and a few words on the background knowledge. As you will see, the intention is to provoke some discussions.


A recently published paper from J. Haigh et al. made it through the media (EurekAlert, CNN) and for a good reason. Indeed, using the data from the new Spectral Irradiance Monitor (SIM) instrument on the SORCE satellite they may have found that the influence of the sun on earth climate is upside down. Scientists and common sense agree that increasing the total solar irradiance warms the earth. On the contrary, the data presented in this paper seem to indicate otherwise.

Before going any further, it is important to quote J. Haigh herself:

"We cannot jump to any conclusions based on what we have found during this comparatively short period and we need to carry out further studies to explore the Sun's activity, and the patterns that we have uncovered, on longer timescales."

Keeping this important caveat in mind, let me summarize their results.

During the 11-years solar cycle, the total solar irradiance varies of about 1 W/m2 (Watts per square meter). It is also known that it does not vary proportionally throughout the spectrum (Lean 2000), i.e the amplititude of the change is different at different wavelengths. What this new paper finds is that the change in the ultraviolet (UV) part of the spectrum is 10 times larger than previously thought and, even more importantly, the change in the visible part has the opposite sign. This means that during solar maxima there's less visible light reaching the earth surface, thus producing less warming. The opposite is true for UV light, which is absorbed in the stratosphere by ozone molecules without reaching the surface. The implications for the earth climate-sun connection should be clear, it works upside down.

Up to this point, one may think that even if confirmed this effect should not have an impact on the long term trends because of the cyclic behaviour. But what if this behaviour proves to be general and not just related to the 11 years cycle? Given that, for example, part of the warming during the first half of the 20th century has been attributed to an increased sun activity,

"[...] if further studies find the same pattern over a longer period of time, this could suggest that we may have overestimated the Sun's role in warming the planet, rather than underestimating it."
Dr Haigh has been very cautious and open to the possibility that it all happened by coincidence::
"The sun has been behaving very strangely. Its magnetic activity is lower than it has been for several hundred years, perhaps. And so the fact that it's doing strange things in its spectrum is perhaps not that unexpected"
One may ask why they published so uncertain results. Haigh gives the answer: "our findings could be too important to not publish them now."

My personal (irrelevant) opinion? I don't know if it's just a coincidence or not, but I'm happy to see our sun doing something interesting, lately.
2010-10-11 07:24:09couple suggestions
Dana Nuccitelli

It would be good in the first paragraph to explain what you mean by "the connection between earth climate and sun activity is upside down."

In the second paragraph define W/m2 (Watts per square meter) and UV (ultraviolet).

It might be worthwhile to give Gavin Schmidt's take.

"While it does seem clear that the overall trend from 2003 to 2009 is an increase, closer inspection suggests that this anti-phase behaviour only lasts for the first few years, and that subsequently the trends are much closer to expectation. It is conceivable, for instance, that there was some undetected or unexpected instrument drift in the first few years. The proof of the pudding will come in the next couple of years."

2010-10-11 08:31:51



I do not think of this post as a rebuttal, I'd rather leave the question open. Gavin Schmidt says it's unlikely and I agree, Haigh herself said it possibly is just a weird period for the sun. But skeptics love the sun so much that it may be interesting to look at their take. In some sense, i've tried to be like a news agency, tell just the facts and let people discuss the issue.

My approach is definitely questionable and including Gavin Schmidt's take adds value, but I will wait for more opinions.

2010-10-11 13:24:11Good idea for a post
John Cook


Good to encourage discussion. I would suggest emphasing early on that the data is only from 2003 to 2009 - a very short period so this could be just some short-term weird behaviour. Without specifying that early on, one can come up with the impression that this upside down behaviour has been observed over a longer period.

The take-home from this paper if there's anything to take from it is if its' true, then we may have overestimated the contribution to 20th Century warming from the sun. Often I end my opening paragraph with the take-home point, then I unpack and reinforce the results in subsequent paragraphs (and usually end with the take-home point again - you can't be too repetitive when you're trying to knock a truth into a stubborn person's skull). It's up to you whether you want to drive this point home harder or not.

Also, I hope you don't mind, I grabbed the pic from Haigh's paper and inserted it into your article, save you the legwork :-)

2010-10-11 18:47:48Upgrade to full author
John Cook

BTW, Riccardo, I've upgraded your account to 'full author' so as soon as you're happy with your blog post, feel free to post it in Author Admin and go live with it (am hoping to wake up tomorrow morning to lots of interesting solar discussion :-)
2010-10-12 04:07:07

Gone live. My bet is that we'll get a lot of comments :)
2010-10-12 23:36:45


I started worrying that picking a few sentences out of context I might have misinterpreted Haigh's thoughts, a well known problem with the media. I sent her a email asking for her eventual corrections. She kindly replied that it's ok. It was kind of relief for me :)

Just to let you know that we were not off the mark.

2010-10-13 16:20:09couple of images
Otto Lehikoinen

max solar effect from (sunspots vs. temp)http://www.woodfortrees.org/plot/hadcrut3vgl/from:1957/to:1967/trend/plot/hadcrut3vgl/from:1962/to:1972/trend/plot/hadcrut3vnh/from:1967/to:1977/trend/plot/hadcrut3vgl/from:1972/to:1983/trend/plot/hadcrut3vgl/from:1977/to:1988/trend/plot/hadcrut3vgl/from:1983/to:1993/trend/plot/hadcrut3vgl/from:1988/to:1997/trend/plot/hadcrut3vgl/from:1993/to:2004/trend/plot/hadcrut3vgl/from:1997/to:2009/trend/plot/sidc-ssn/from:1945/normalise/plot/hadcrut3vgl/from:1951/to:1962/trend/plot/hadcrut3vgl/from:1947/to:1957/trend

spectrograph on photosynthetic frequencies (incomplete, there are whole bunch of other molecules participating) http://www.peoi.org/Courses/Coursesen/bot/Resources/image802.jpg

The interesting bit of this is, it seems to me the spectral variation (presuming it obeys the standard ~11 year cycle) can increase the relative effect of the sun for the plants may increase their activity in parts of the solar cycle (effecting the activitiy of carbon sinks). Anyway the as most of the TSI gets absorbed by the earth this result shouldn't alter the relative effects of the greenhouse gases and direct radiative sun heating.