Regular readers will know of my long-held scepticism concerning AGW (Anthropological Global Warming). Partly this arises from the nature of the people propagating it as a theory, and also, my instinct that our, meaning humanity's, effect on global temperatures is the equivalent of me pissing in my local reservoir and worrying about it overflowing! There is a constantly repeated cliche these days to the effect that some people 'ignore the elephant in the living-room'. In trying to guess (yes, I call it a 'guess' although the swots prefer to call it a 'theory' because it sounds better) as to what is likely to have the greatest influence on the world's temperature, I would point unhesitatingly at that great, big, bright thing in the sky that we call the sun. That monstrous creator and discharger of energy in all its forms is the equivalent of not just one elephant, but every elephant and every elephant's near relations, that has ever existed in the history of the world all crammed into your living-room! The difficulty is trying to decipher the information we have on the sun and its variable states and trying to guess/theorise as to their effects on earth.
One feature has been spotted (pun intended!) and regularly measured for some years and that is the frequency and strength of sunspots which follow a roughly 11-year cycle. There seems to be a correlation between their behaviour, in the sense of appearance or non-appearance, and subsequent effects on earth. This whole subject is densely 'swottish' and consequently I can only pick up the very vague gist of it all. However, in a comments thread to a recent post at the ever-excellent Watts Up With That site, an equally bemused reader begged for someone to provide a synopsis in language that a layman could understand. Shortly there-after, Mr. Rhys Jagger stepped forward and wrote this superb summary and I for one am deeply grateful to him. I have only cut his opening, introductory paragraph:
1. The sun has things called sunspots on its surface some of the time and the numbers of them have been shown to oscillate from a minimum through a maximum and back down to a minimum in a cycle whose length varies from cycle to cycle but is usually around 11 years.
2. Due to changes in the sun’s magnetic field, the solar cycles are usually grouped in pairs of ‘odd cycles’ and ‘even cycles’. One pair is called a Hale Cycle which is usually around 22 years.
3. It has been shown that certain features in the global weather patterns show cyclical patterns, some of which are linked to one solar cycle, others to the Hale cycle. There are other ‘footprints’ of shorter or longer duration which are also linked to interactions between solar and lunar variables; solar and big planet variables etc etc.
4. The effect of sunspots is to change the intensity of certain radiation emitted from the sun which reaches the earth. Occasionally, these can be major pertubations when features called ‘Coronal Mass Ejections’ or ‘Flares’ occur. These have effects on radio signals, satellites and other things orbiting our earth, so folks like NASA, the Hubble Telescope guys etc etc monitor these things carefully.
5. People have noticed that every few hundred years the sun ‘goes quieter’ or ‘very quiet’ for a few decades to several decades. These periods are called minima and are usually named after someone. The Maunder Minimum in the Middle Ages was particularly quiet, whereas a smaller minimum occurred in the early part of the 19th century and was called the Dalton Minimum.
6. Although understanding is still far from complete, researchers are now trying to link solar activity, specific solar output to weather patterns, either short-term or long-term. Piers Corbyn of Weather Action Ltd is someone who makes a living out of this, being particularly adept at predicting extreme weather events associated with solar/lunar pertubations several months ahead of time. His method continues to evolve, as he would freely admit both to his subscribers and those who read his website (www.weatheraction.com).
7. In general, also, the fewer the sunspots you get in an 11 year cycle, the greater the likelihood there is of cooling of the earth. Conversely a series of high sunspot cycles, as occurred in the 20th century, is postulated/believed to be associated with a warming climate. The Little Ice Age was associated with the Maunder Minimum, which was the quietest period of sunspot activity in the past 500 years.
8. Researchers are also wondering whether frequencies of volcanoes/earthquakes/tsunamis etc can be linked to the sunspot cycles. There is certainly no official scientific proof of this, but people are looking at it and having attempts at predicting such events. Time will tell whether they are accurate or not.
9. Of course, if scientists could predict how sunspot cycles would pan out a few decades in advance, this would be extremely valuable for mankind if our politicians, financial communities and farmers made good use of such information for the benefit of societies. In particular, if we were able to predict a marginalisation of yield in major growing areas like Canada, the Northern Mid West of the USA, Russia/Ukraine etc due to the onset of a mini ice age, then efforts would surely be made to evolve agricultural production through lower latitudes. It’s by no means clear that we are able to do this yet and it may take 100 years more of detailed research before it does become possible.
10. Really detailed monitoring of the Sun has only become possible in the era of satellites and telescopes and therefore data prior to about 1950 isn’t really as accurate as the measurements since 1979, when the first satellite data started coming through. As a result, true understanding of what sunspots looked like back in the 1700s, 1800s etc etc is never going to be as accurate as scientists would like. Nonetheless, data from 24 cycles of sunspot cycles since the end of the Maunder Minimum is what scientists use for their predictions for the future.
11. Currently, many scientists believe that the current cycle (24) and the next one (25) will be much weaker than those which have preceded them. There is a body of opinion which believes this points to cooling tendencies from the sun, although how any warming of oceans may compensate for that in terms of air temperatures and subsequent land temperatures is less clear. Scientists who believe that solar output is a major contributor to temperature fluctuations on earth are therefore somewhat skeptical about the ‘global warming’ scaremongering going on particular those who postulate increasing carbon dioxide as the major forcing mechanism.
12. It would not be considered ludicrous therefore for politicians to plan for little rise in temperatures for the next 30 years and they should certainly scenario plan for a possibility of significant cooling. Given, however, that the Dalton minimum in the early 19th century only lasted for 2 cycles before solar output increased again, until proven otherwise, it should be assumed that a return to potentially warmer fare may occur thereafter. Politicians will ask scientists, however, to be constantly looking out for signals that the sun may be going into a deeper sleep and they should be planning how to manage a Northern Hemisphere which might become dangerously short of food in the absence of the Sahara not becoming more fertile in response, should a Maunder-style minimum come to pass.
I wouldn’t expect anyone to take this as gospel truth, nonetheless, I reckon it’s probably a fair summary for non-experts and certainly doesn’t say anything which is clearly false.
The care with which Mr. Jagger avoids claiming certitude for what is, after all, still a theory, is excellent. I, for one, am deeply grateful to him for his superb explanation.