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.