On Reading The Little Ice Age
Earlier this year I read the book Brian Fagan, The Little Ice Age : How Climate Made History 1300 – 1850, by Brian Fagan (New York : Basic Books, 2000; 246 pages). He takes a close look at the relatively cool period between the "Medieval Warm Period" and the current warming period, and considers in careful but fascinating detail the ways that global climate change affected European society and culture. I thoroughly enjoyed it. I think he did an excellent job assembling all of his facts and dates and locations and keeping them well sorted out and in line with his thesis. I gave it high marks in my book note.
Anyway, here's an excerpt that interested me. This was one of his many entertaining and enlightening asides, this one a nicely done short history of sunspots.
Sunspots are familiar phenomena. Today, the regular cycle of solar activity waxes and wanes about every eleven. years. No one has yet fully explained the intricate processes that fashion sunspot cycles, nor their maxima and minima. A typical minimum in the eleven-year cycle is about six sunspots, with some days, even weeks, passing without sunspot activity. Monthly readings of zero are very rare. Over the past two centuries, only the year 1810 has passed without any sunspot activity whatsoever. By an measure, the lack of sunspot activity during the height of the Little Ice Age was remarkable.
The seventeenth and early eighteenth centuries were times of great scientific advances and intense astronomical activity. The same astronomers who observed the sun discovered the first division in Saturn's ring and five of the planet's satellites. They observed transits of Venus and Mercury, recorded eclipses of the sun, and determined the velocity of light by observing the precise orbits of Jupiter's satellites. Seventeenth-century scholars published the first detailed studies of the sun and sunspots. In 1711, English astronomer William Derham commented on "great intervals" when no sunspots were observed between 1660 and 1684. He remarked rather charmingly: "Spots could hardly escape the sight of so many Observers of the sun, as were then perpetually peeping upon him with their Telescopes…all the world over." Unfortunately for modern scientists, sunspots were considered clouds on the sun until 1774 and deemed of little importance, so we have no means of knowing how continuously there were observed.
The period between 1645 and 1715 was remarkable for the rarity of aurora borealis and aurora australis, which were reported far less frequently than either before or afterward. Between 1645 and 1708, not a single aurora was observed in London's skies. When one appeared on March 15, 1716, none other than Astronomer Royal Edmund Halley wrote a paper about it, for he had never seen one in all his years as a scientist–and he was sixty years old at the time. On the other side of the world, naked eye sightings of sunspots from China, Korea, and Japan between 28 B.C. and A.D. 1743 provide an average of six sightings per century, presumably coinciding with solar maxima. There are no observations whatsoever between 1639 and 1700, nor were any aurora reported.
3 Responses
Subscribe to comments via RSS
Subscribe to comments via RSS
Leave a Reply
To thwart spam, comments by new people are held for moderation; give me a bit of time and your comment will show up.
I welcome comments -- even dissent -- but I will delete without notice irrelevant, rude, psychotic, or incomprehensible comments, particularly those that I deem homophobic, unless they are amusing. The same goes for commercial comments and trackbacks. Sorry, but it's my blog and my decisions are final.
on Thursday, 12 March 2009 at 20.40
Permalink
[I am approving the following comment so that we can keep it around for possible analysis later, since it exhibits so many of the characteristic elements of crank pseudoscience, such as a delight in obfuscating jargon and an appeal to scattershot "argument". However, none of the conclusions–if you can identify them–are scientifically credible. –jns]
There are some theories about the barycentre of the solar system modulating solar activity (sunspots).
Keeping in mind that windmills are hazardous to birds, be wary of the unintended consequences of believing and contributing to the all-knowing environmental lobby groups.
Climate and economy are being linked. Yes there has been warming since the Pleistocene. Climate is a multiple input, multiple loop, multiple output, complex system. The facts and the hypotheses do not support CO2 as a serious 'pollutant'. In fact it is plant fertilizer and seriously important to all life on the planet. It is the red herring used by the left to unwind our economy. That issue makes the science relevant.
Water vapour (0.4% overall by volume in air, but 1 – 4 % near the surface) is the most effective green house gas followed by methane (0.0001745%). The third ranking greenhouse gas is CO2 (0.0383%), and it does not correlate well with global warming or cooling either; in fact, CO2 in the atmosphere trails warming which is clear natural evidence for its well-studied inverse solubility in water: CO2 dissolves in cold water and bubbles out of warm water. The equilibrium in seawater is very high; making seawater a great 'sink'; CO2 is 34 times more soluble in water than air is soluble in water.
CO2 has been rising and Earth has been warming. However, the correlation trails. Correlation, moreover, is not causation. The causation is being studied, however, and while the radiation from the sun varies only in the fourth decimal place, the magnetism is awesome.
“Using a box of air in a Copenhagen lab, physicists traced the growth of clusters of molecules of the kind that build cloud condensation nuclei. These are specks of sulphuric acid on which cloud droplets form. High-energy particles driven through the laboratory ceiling by exploded stars far away in the Galaxy – the cosmic rays – liberate electrons in the air, which help the molecular clusters to form much faster than climate scientists have modeled in the atmosphere. That may explain the link between cosmic rays, cloudiness and climate change.”
As I understand it, the hypothesis of the Danish National Space Center goes as follows:
Quiet 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
Active sun → enhanced magnetic and thermal flux = solar wind → geomagnetic shield response → less low-level clouds → less albedo (less heat reflected) → warmer 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.
The ultimate cause of the solar magnetic cycle may be cyclicity in the Sun-Jupiter centre of gravity. We await more on that.
Although the post 60s warming period appears to be over, it has allowed the principal green house gas, water vapour, to kick in with more humidity, clouds, rain and snow depending on where you live to provide the negative feedback that scientists use to explain the existence of complex life on Earth for 550 million years. Ancient sedimentary rocks and paleontological evidence indicate the planet has had abundant liquid water over the entire span. The planet heats and cools naturally and our gasses are the thermostat.
Check the web site of the Danish National Space Center.
http://www.space.dtu.dk/English/Research/Research_divisions/Sun_Climate/Experiments_SC/SKY.aspx
on Friday, 13 March 2009 at 14.51
Permalink
Interesting, isn't it, what constitutes great and inexplicable events? Thanks for the recommendation – I have reason to do some book ordering.
From what I've read before though, there seems little doubt that the sun's behavior was really quite different for a number of years in the 17th century, in terms of sunspots and the visual effects that accompany them, and has not been seen since. (I'll let alone the Little Ice Age aspect, since it may have well been local rather than global, and therefore not associated with solar anomalies.)
BTW – do you remember Rob B…. can't remember his last name, Bernard?, RobBear, from soc.motss? In the early 90s he emailed me several times on the unlikelihood of global warming, since the sun was clearly not getting hotter. I recall that he was an astrophysicist.
But you're a rocket scientist! What do you think?
on Thursday, 26 March 2009 at 11.21
Permalink
I do remember Rob Bernardo; I didn't remember him as an astrophysicist.
Indeed, there was the odd time from mid-1600 to early 1700, called the "Maunder Minimum", when sunspot activity virtually disappeared. Some of it coincides more or less with the period of the "little ice age", giving great encouragement to those folks desperate for any natural explanation to twentieth century warming trends other than anthropogenic ones.
I've been a reasonably skeptical scientist on the topic, more so twenty years ago, but I think it's pretty well established now that we have seen an undeniable warming trend since the beginning of the Industrial Revolution, and that it is linked to increasing carbon-dioxide concentrations in the atmosphere.
Of course, the question is "what are the consequences?" What has become clearer, and more alarming, in recent years is that a gentle increase in CO2 with a gentle increase in temperature is not the consequence of consequence. Rather, there are large-scale systems in the Earth, such as the "north-atlantic conveyor" or CO2 storage in carboniferous rocks–that operate on very long timescales and that interact with the atmosphere and oceans nonlinearly. That last is the scary bit: nonlinear in this context means that small changes (e.g., in atmospheric CO2 concentrations) can lead to big climatic shifts, e.g., by shutting down the North-Atlantic conveyor for several thousand years. We don't know where the thresholds are for that to happen, but deep history has shown that it has happened and that it may have been responding to shifts in CO2 concentration.
Focusing on the "warming" in "global warming" is naive. The concern is the nonlinear response of these major circulatory and storage systems in the Earth that we don't understand terribly well. Shutting down one of those or throwing another into a major oscillation would likely cause a major response in global climate that would be very unpleasant. They've happened before. They're happened naturally, but we may be in a position now to trigger one anthropogenically, and it seems very prudent to me to do what we can to learn about it and avoid it.
I think my favorite recently-read books for creating a lot of understanding on the question have been this one, The Little Ice Age, and The Two-Mile Time Machine.