The Chilling Stars: A Cosmic View of Climate Change [Englisch] [Taschenbuch]

A very readable book that makes strong case for effects of cosmic rays on cloud formation and hence on climate change. Because the basic theory is that fluctuations in the sun's magnetic field affect cosmic ray intensity on earth, there is considerable material on astronomy (cosmic rays, supernovas etc.) which provides the background needed to understand the discussion. In essence, more solar magnetic storms strengthen the sun's magnetic field which divert cosmic rays from earth. Cosmic rate create ions that provide nuclei for cloud formation. More nuclei mean more low clouds and more reflective clouds which in turn cool the earth, (except over Anartica and other ice covered areas, since snow and ice actually reflect even more sunlight than clouds).
The author (a Danish scientists who did much of the key work in this area) has been able to produce the effect in the laboratory and has documented the statistical relationship with low level clouds and surface temperatures. Many climate episodes over millions of years appear to be explained by cosmic ray effects. The theory also explains how differing number of sun spots come to affect year to year climate change on earth.

The later makes this a key book for those interested in the global warming debates, especially since so much of the research is recent. This makes it a must read since the evidence is not yet in most other popular discussions of climate change.

Henrik Svensmark, director of the Centre of Sun-Climate Research at the Danish National Space Centre, and Nigel Calder, the well-known science writer, have produced a challenging book on climate change.

When stars die, they do so in supernova explosions that emit cosmic rays, which create ions, which form clouds. Low clouds - less than 3000 metres above the surface - keep the planet cool. The less active the sun is, the more cosmic rays get through to the earth, and so the more clouds there are to cool the earth.

The Danish National Space Centre's SKY experiment showed how cosmic rays set free electrons which then catalysed the clubbing together of sulphuric acid molecules, the most important source of condensation nuclei. These cosmic rays have varied since the world began; their influx depends largely on where the earth is in the galaxy in our orbit around the centre of the Milky Way. When the earth is in dark regions with few stars where the rays are scarce, the climate is warm. When the earth is in bright regions where the rays are intense, the climate is cool.

The medieval warm period of 1000-1300 was followed by the cool periods of 1300-60 and 1450-1540, and a worse one, the little ice age of 1645-1715, then another cool period in 1790-1820. The peak of the little ice age was 1700, which coincided with the Maunder Minimum, when the sun's magnetic activity was very low, reducing its ability to shield the earth from cosmic rays.

In the last century, the sun's magnetic field doubled in strength, reducing the cosmic rays and so the clouds, thus heating up the earth by 0.70C from 1900 to 2005, 70% of the 20th century's warming. The authors predict that global warming in this century is likely to be at the low end of the Intergovernmental Panel on Climate Change's forecast of a 1.80C-40C rise by 2100.

Indeed, temperatures have not risen since 2001, even though global CO2 emissions have been rising faster than ever. Also, the Antarctic's area of sea ice grew by 8% between 1978 and 2005.

The theory presented in this book sounds a bit suspect when one first hears it. So the explanation for climate change is cosmic rays from outer space, give me a break.

But the climate on planet Earth has been changing for roundly 4 billion years, within quite wide limits. There have been periods when most of the land surface was covered by ice caps, periods when even the polar areas were semi-tropical, and just about every state in between. There must be something big driving the system, the theories based on manmade carbon emissions (a recent phenomenon) do not seem to have much to offer, and the cosmic ray theory starts sounding better when it is broken down step by step.

#The starting point is low-lying clouds, which serve to deflect incoming solar energy and thereby cool things down. Caveat: the massive and intensely white ice cap of Antarctica is even more reflective than the clouds, so in that one area (but not Greenland, Siberia, etc.) clouds warm things up.

#Water vapor in the atmosphere will produce more clouds if there are nuclei (or specks) in the air to facilitate the process. The formation of nuclei is in turn facilitated by cosmic rays (high energy, charged particles that bombard our solar system from outer space). Hey, remember how energetic atomic particles were detected at one time with cloud chambers that would display vapor trails triggered by their passage.

#Cosmic rays originate from the explosion of dying stars; they are not equally spread through the universe nor constant over time. As our sun makes it way around the Milky Way galaxy, the volume of cosmic rays encountered waxes and wanes. The time periods involved are so long (think millions of years), however, that human beings with their limited time span are unlikely to notice.

#Affecting the volume of cosmic rays on earth in a much more immediate way is the sun's magnetic field, which deflects many incoming cosmic rays. Fluctuations in this magnetic field go hand and hand with the level of sunspot activity, which over the past several years has declined to practically zero. If the level of sunspot activity remains low, the volume of cosmic rays striking earth will be high and a global cooling trend can be expected. There have been recent signs that a cooling trend is indeed getting started, such as has not been seen since the early 1970s.

Is the cosmic ray theory true? I am hardly qualified to make such a judgment, but it does seem that the authors have set forth their evidence in a convincing fashion. There is no apparent reason to believe that the scientists participating this line of inquiry (collectively there are quite a few of them) have any ulterior motive, by the way, such as being "in the pay of the oil companies." Indeed, the authors go out of their way to say that they are not interested in promoting a bonfire of fossil fuels just because the importance of CO2 in the recent warming trend may have been exaggerated.

Let the testing of the cosmic rays, manmade carbon emissions, and other theories continue, with the objective of arriving at a clearer understanding of what kind of climate change we can expect for this planet and why.

The debate is called scientific inquiry, and that is a good thing.