Updating The Chilling Stars and Magic Universe
When cosmic rays freeze the world, you’d better evolve
Transforming the story of life on the Earth is a report in Nature today about multicellular creatures more than 2 billion years old, at a time when single-celled bacteria supposedly reigned supreme. Fossils you can pick up with your fingers, found in Gabon, West Africa, are far, far older than the multicellular animals that become detectable about 600 million years ago (Ediacaran period) and conspicuous 542 million years in the “Cambrian explosion”. The age is fixed with remarkable precision at 2070 to 2130 million years.
A team of 21 experts from France, Sweden, Denmark, Canada, Germany and Belgium make the report. The lead author is Abderrazak El Albani, at the University of Poitiers, France. He tells Agence France Press that “More than 250 specimens have been found so far. They have different body shapes, and vary in size from one to 12 centimetres.”
What excites me about the discovery is that here was a far-reaching evolutionary response to the rise of oxygen in the Earth’s atmosphere beginning more than 2000 million years ago. It occurred in the aftermath of a planet-wide freeze for which there is a cosmic explanation.
Chapter 6 in The Chilling Stars includes the story of “Snowball Earth” events. Here are some extracts.
In 1986, George Williams and Brian Embleton in Australia used the magnetism in grains of iron oxide dropped from ancient ice to show that they were released within a few degrees of the Equator. A few years later, Joseph Kirschvink of the California Institute of Technology confirmed this result in magnetism associated with other rock formations in Australia produced by ice action, and well dated as 700 million years old. He called it ‘bullet-proof evidence’.
“It now seems clear that these extensive, sea-level deposits … were formed by widespread continental glaciers which were within a few degrees of the equator. The data are difficult to interpret in any fashion other than that of a widespread, equatorial glaciation.”
Kirschvink invented the name Snowball Earth for that dire climatic state. You have to visualise ice sheets, glaciers and frozen seas even at the Equator itself. The degree of ocean freezing is still debated. Some investigators imagine vistas of ice a kilometre thick or more, others prefer a ‘slushball’picture with drifting sea ice and icebergs. Either way the impact on life was severe.
Evidence from all the world’s continents unpacks into about three separate snowball episodes in the interval 750 to 580 million years ago. Worms that survived by scavenging the sea-bed detritus evolved the body-plans that made possible the explosion of animal life mentioned in the previous chapter, when the world became reliably warmer again in the Cambrian Period that started 542 million years ago.
Those cold Neo-Proterozoic times, as geologists call them, were not the only occasion of such radical events involving ice and evolution. By the end of the 20th century, geologists had amassed evidence from South Africa, Canada and Finland that confirmed two Snowball Earth episodes between 2,400 and 2,200 million years ago, in Palaeo-Proterozoic times. Our planet was then only half its present age.
Sun still sulks
20/06/2010Pick of the pics and Climate Change: News and Comments
The Sun still sulks
Two magnetograms from the ESA-NASA SOHO spacecraft contrast the Sun’s liveliness of exactly 10 years ago (20 June 2000) on the left with its feeble performance today (20 June 2010) on the right. In these images made with Stanford’s Michelson Doppler Interferometer, north magnetic polarity is white, south magnetic polarity is black.
Solstice sunrise over Stonehenge 2005. Credit: User: Solipsist.
In the current issue of the Royal Astronomical Society’s magazine Astronomy and Geophysics, Nigel Weiss of Cambridge considers the long-term variability of the Sun and alternative theories about it, especially concerning “grand maxima” in activity like that in the 20th Century, and “grand minima” like the Maunder Minimum of 300 years ago associated with the Little Ice Age. Weiss’s conclusion is that there’s a 40 % chance the current grand maximum will be followed by a grand minimum.
As for the climatic implications, Weiss and I agreed to differ some years ago. Although we both say that the Intergovernmental Panel on Climate Change underestimates the influence of the Sun, Weiss thinks it can’t compete with man-made global warming. His article ends:
Even if the Sun does enter a new Maunder-like grand minimum, any cooling effect will be small compared with the warming produced by anthropogenic greenhouse gases.
Contrast that with Henrik Svensmark’s conclusion in an article for the Danish newspaper Jyllands-Posten.
That the Sun might now fall asleep in a deep minimum was suggested by solar scientists at a meeting in Kiruna in Sweden two years ago. So when Nigel Calder and I updated our book The Chilling Stars, we wrote a little provocatively that “we are advising our friends to enjoy global warming while it lasts.”
In fact global warming has stopped and a cooling is beginning. Mojib Latif from the University of Kiel argued at the recent UN World Climate Conference in Geneva that the cooling may continue through the next 10 to 20 years. His explanation was a natural change in the North Atlantic circulation, not in solar activity. But no matter how you interpret them, natural variations in climate are making a comeback.
The outcome may be that the Sun itself will demonstrate its importance for climate and so challenge the theories of global warming. No climate model has predicted a cooling of the Earth – quite the contrary. And this means that the projections of future climate are unreliable. A forecast saying it may be either warmer or colder for 50 years is not very useful, and science is not yet able to predict solar activity.
So in many ways we stand at a crossroads. The near future will be extremely interesting. I think it is important to accept that Nature pays no heed to what we humans think about it. Will the greenhouse theory survive a significant cooling of the Earth? Not in its current dominant form. Unfortunately, tomorrow’s climate challenges will be quite different from the greenhouse theory’s predictions. Perhaps it will become fashionable again to investigate the Sun’s impact on our climate.
References
N. Weiss, “Modulation of the Sunspot Cycle”, Astronomy and Geophysics, Vol. 51, pp. 3.9-3.15, 2010
H. Svensmark: “While the Sun sleeps” (in Danish), Jyllands-Posten, 9 September, 2009
For a related post on this blog see https://calderup.wordpress.com/2010/05/12/puzzling-sun/
Postscript on the Song of the Sun
I see that Sheffield solar physicists now generate music from observations of the magnetic coronal loops. Read about it (and hear it): http://www.telegraph.co.uk/science/space/7840201/Music-of-the-sun-recorded-by-scientists.html
For an earlier Song of the Sun, using its internal vibrations seen by SOHO’s MDI, click on the second item here (but beware – it’s about 18 MB with visuals) http://www.esa.int/esaSC/SEMLAJWO4HD_index_0.html