To get the music out of the way at once, I first heard this George Harrison song when Nina Simone sang it. In fact, this post is about the influence of the Sun on the climate of the Earth, a subject I wrote about at the end of the year. The post received a good deal of comment, and some of the comments forced me to go and do much more reading and thinking. And the more I read the richer the subject became. So what I have written here is only a short and superficial guide to a major area of research.
No matter, even the IPCC is coming to the view, reluctantly and with some hedging, that it has underestimated the role of the Sun. The WG1 volume of the 5th Assessment report has this to say, in the context of the pause: The observed reduction in warming trend over the period 1998–2012 as compared to the period 1951–2012, is due in roughly equal measure to a cooling contribution from internal variability and a reduced trend in radiative forcing (medium confidence). The reduced trend in radiative forcing is primarily due to volcanic eruptions and the downward phase of the current solar cycle.
There is something odd about this, as we haven’t had much in the way of volcanic incidents in that 14 year period, and if solar activity (= sun-spots) are not of much power, as is the IPCC’s position(see the comments at the post I cited above) then how can they be a cause of the ‘pause’? If you want more of this, then go to Willis Eschenbach’s recent erudite post at WUWT, from which I took the IPCC quote.
I only saw that post a day or so ago, but the reading I have been doing has taken me to an excellent review article by Richard Mackey, ‘The Sun’s role in regulating the Earth’s climate’ published recently in the Journal of Energy and Environment paper (VOLUME 20 No. 1 2009). This is no quick read, because it is fifty pages long and refers to nearly 150 articles. But to read it, and I’ve now done so twice, is to enter a completely different world than the one in which carbon dioxide is thought to be the ‘control knob’ of the Earth’s climate.The solar physicists seem to be pretty sure that they can explain a good deal of the apparent warming over the last century, though you don’t hear about this in the mainstream media, and there’s nothing much about it in the IPCC reports.
What they are talking about is not simply sunshine, or ‘total solar irradiance’, but other aspects of the Sun/Earth relationship, including the movement of the planets and the Moon (the tides being the result of the joint effects of the Sun and the Moon), the effects of the Sun’s electro-magnetic field, the solar wind, the occasional burst of matter (mainly electrons or protons), and the inter-relationships between all these variables — which can be more significant still. We need to remember, because it is not obvious from the way we see the Sun, that it is incomparably larger than our planet: about 1,300,000 times bigger in terms of relative volume. Almost anything that happens in the Sun can have an effect on us, especially in terms of climate.
We can’t predict at all well, however. The relationships I mentioned are unstable over time. Yes, we can find patterns and regularities (and there are lots of them), but they do not work like clocks, and we do not by any means wholly understand them. Nonetheless, Gerard Bond, the American astronomer who gave his name to Bond events (see the great chart on human history since the ice age) has claimed that ‘The Earth’s climate system is highly sensitive to extremely weak perturbations in the Sun’s energy output …’
Others claim that ENSO events are largely regulated by total solar variability (sun-spots again) and that El Nino events occur twice in each solar cycle, one each in the ascending and descending phases of each cycle — and that solar wind variations precede El Nino events by 15/16 months. There seems no doubt that during solar maxima the Earth warms up and during solar minima it cools down — and the the planet does so everywhere.
Why is it so? There are hypotheses of all kinds. What we have are observations in need of explanation, not computer models offering confident answers. It is fascinating stuff. How about the Length of the Day, the measure of the Earth’s rotation around its axis? Every ten years or so the Earth rotates a little faster or slower –speeding up a little over one decade and slowing down a bit over the following one. Long ago, it was shown that the speeding-up brings on global warming after about six years; the slowing down brings on global-cooling. I’ve started on a new knowledge avenue in global warming, one that I knew nothing about whatever when I started to read about climate six years ago. And I’ll continue along it.
To finish: Mackey’s review article was published in 2009, and even then, five years ago, the consensus among the solar physicists was that we were pretty likely to experience a long period of cooling. Well, the evidence so far is that their conclusion was right —it is plain, at least, that average temperatures are not rising in harmony with carbon dioxide accumulations. I keep having to remember that the sun is really much more powerful than we think — and that, as with other aspects of ‘climate change’, we have a lot more to learn.[updated 23 January 2014 to provide a better link to Mackey’s paper, a copy of which any reader can get from me by emailing me at <firstname.lastname@example.org> — the journal wants a lot of money for it!]