Thursday, 17 July 2008

Global Warming and the Sun

Well there was an opinion piece in my local daily (well ok to be fair I don't know if it made the press version but it was front and centre on the webpage this morning) and it was about global warming, and while it was not outright denying it (nobody who is anybody does that any more not even George W. Bush) it takes a look at the solar influences and presents them as the dominant factor.

Before I say more about the article I would like to mention that one of my supervisors does research on Solar Flares and how they effect the atmosphere (in particular the ionosphere), and as solar flares are caused by sunspots, this leads to me have a pretty good idea of the solar cycle.

So when Professor Geoff Kearsley (of the Department of Media, Film and Communication, though to be fair according the article a geographer by training) claims that anthropocentric claims about climate change are "distorted by dogma" and the real driving forces such as the sun are being ignored. I want to scream and tear my hair out, both about those that claim the mantle of Climate skeptics (not so much driven by the article - but it is related) and about the relationship between temperature and solar activity (as defined in the usual way by sunspot number).

I will address the skeptics point first - anyone who claims to be a skeptic of something just because they disagree with it is should really be named as what they are contrarian. I suppose a lot of the general public get the wrong idea when all the media does with respect to skeptics is give them a brief quote anti to any of the journalists favourite quackery - such as psychics.

But a skeptic is one who looks at the evidence for any phenomena (and the quality of evidence which is very important) before making up his mind. So if there was concrete evidence for psychics, or for homeopathy, or what ever then the skeptics would be behind such things rather than against them.

As such I will proudly call my self a climate skeptic despite the fact that I am completely swayed by the facts that it is a man-made phenomenon. That is right I just said that we are causing climate change.

And my response to the good professor is has he seen the image at the top of this post. Ok it is old data now (from an article in 2004 - which should be available here but you will need a subscription - if you are desperate to see a copy just ask), but the point it makes (and I apologise if it may be a bit hard to make out some of it this was pinched out of one of my supervisors presentations and I will try and extract it anew from the original) is the the global temperature in recent times (the green and blue lines and the plot is over the last 300 years) follows reasonably (although with a little lag) the red line which is the smoothed trend for sunspot cycle length (orange line) up until approximately the 1950s at which point the temperature leaves the cycle of sunspots behind and increases.

This would tend to indicate that even if more recent data might show a slight dip in the trend in the past couple of years, that there has been a shift in the global temperature response to the solar cycle. More recent data may show (and I haven't seen any) a change in the trend but that does not deny the massive change in temperature compared to solar cycle activity that has occurred in the last 50 years, the point of this being if this abnormally long solar cycle (which has officially ended now) is visible in the temperature trend it is unlikely to have had a big effect as it would have without the effect of the industrialization of our planet.


Francis T. Manns, Ph.D. said...

The best advice I ever got as a doctoral student was, "The minute you believe your own hypothesis, you are a dead duck scientifically". That's the bottom line and puts Al Gore into perspective.

Fran Manns

mc2 said...

Well, it is not my hypothesis, and it all really depends on what the data shows.

The graph in the post is pretty unequivocal.

Francis T. Manns, Ph.D. said...

But have you read all the literature and put it into context? Friis-Christiensen and Lassen, (1991;Science) produced a 95% correlation between sunspot peak frequency and global warmiong and cooling. Svensmark et al (2006)describe experimental support for a cosmic interaction with clouds that could be the cause of the correlation. This is consistent with the Maunder Minimum. The Danes have an experiment coming up at CERN to test the hypothesis.

As I understand it, the hypothesis of the Danish National Space Center goes as follows:
‘Active’ sun → enhanced magnetic and thermal flux = solar wind → geomagnetic shield response → less low-level clouds → less albedo (less heat reflected) → warmer climate
Less active sun → reduced magnetic and thermal flux = reduced solar wind → geomagnetic shield drops → galactic cosmic ray flux → more low-level clouds and more snow → more albedo effect (more heat reflected) → colder climate
That is how the bulk of climate change might work, coupled with (modulated by) sunspot peak frequency there are cycles of global warming and cooling like waves in the ocean. When the waves are closely spaced, the planets warm; when the waves are spaced farther apart, the planets cool.

Does Al Gore have a test scheduled at CERN?

Francis T. Manns, Ph.D. said...

The subtlety is that the correlation is not with sunspot numbers. The correlation between heating and cooling is with sunspot peak frequency. Sunspot number is a mushy parameter, but peak frequency correlated well throughout the 20th century until Pinatubo erupted.

mc2 said...

I have read some but not all of the relevant literature. While you description of the Danish mechanism does make some sense and I would be interested in the results of said testing, you comment about Al Gore is nonsensical.

I am not basing any of my arguments or opinions on any thing Al Gore has said and I have not even watched his documentary. He is not a scientist and is not trying to test a hypothesis, his actions are about creating an awareness of what he thinks is going on and I congratulate him on his efforts.

Now you mentioned correctly that the correlation is with solar cycle length and not sunspot number (solar activity), this I tried to make clear in my post and is certainly what the graph is describing.

Both the temperature data sets shown in the figure are more recent than the 1991 Science article you mention. And as for the Maunder Minimum and the Little Ice Age, these happened before ~1950 where as you can see on the graph that Solar cycle length and global temperatures correlated well.