In several Acts & Facts articles over the past few years, I have addressed Henrik Svensmark’s theory that modulated galactic cosmic radiation (GCR) from outer space may be one of the primary driving mechanisms for global warming.1-5 Industrialization may have contributed slightly to global warming, but natural mechanisms involving the sun are probably more important. Svensmark has presented evidence that when the sun is active (more solar flares, a strong solar wind, and more sunspots), its electromagnetic field envelopes the earth and shields it from GCR, producing low cosmic radiation, fewer clouds and a hot earth (see Figure 1).

Svensmark has also demonstrated that when the sun is inactive (fewer solar flares, a weak solar wind, and fewer sunspots), the earth is exposed to more GCR, which produces high cosmic radiation, more clouds, and a cool earth (see Figure 2). Various studies have shown a correlation between cosmic radiation and global temperature.

However, at least one key ingredient in Svensmark’s theory has prevented its wholesale adoption—the evidence that more cosmic radiation entering the earth’s atmosphere causes more nucleation of cloud droplets and the formation of more clouds that increase the albedo of the earth (the percentage of solar energy the earth reflects). If it can be shown that cosmic radiation increases the concentration of cloud droplets that lead to more clouds, the theory will be well on its way to being confirmed.

CLOUD Experiment

Jasper Kirkby at CERN (European Organization for Nuclear Research) in Geneva, Switzerland, took on the task of conducting experiments on the enhanced nucleation of cloud particles in a large cloud chamber that could be irradiated with a well-controlled beam of high-energy protons (see Figure 3). The beam of protons simulates galactic cosmic rays that nucleate cloud particles that continue to grow and form cloud droplets. Kirkby provided a video description of the chamber and the planned experiments at a lecture in Vancouver, Canada, on March 23, 2011.6

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