Cosmic rays are a type of radiation that consist of highly energetic particles; specifically, they are composed mostly of protons, along with moderate amounts of alpha particles (helium nuclei), electrons, gamma rays (high-energy electromagnetic radiation), neutrinos (neutral elementary particles), and even smaller amounts of heavier atomic nuclei. While traveling through outer space some of them contact the Earth’s atmosphere. Cosmic rays can originate from many different sources, but the ones that come from the Sun affects the Earth the most. They have energies of about 100 exa-electron volts (EeV, where exa- stands for quintillion—that is, 1 followed by 18 zeros).
Because cosmic rays are not very dense they are able to travel easily through the near-emptiness of space. However, once they reach the dense atmosphere of the Earth, the particles that make up cosmic rays quickly interact with gaseous particles that make up the atmosphere. The interaction creates ions (electrically charged particles), which attracts water molecules. Over time, water molecules group together and, eventually, condense into droplets. Clouds are formed from this condensation process.
According to Svensmark, director of Sun-Climate Research at the Danish National Space Center in Copenhagen, the amount of cloud formation above the Earth is directly in response to the magnetic activity of the Sun. When solar magnetic activity is high, fewer cosmic rays are produced and fewer cosmic rays reach the Earth’s atmosphere, which produces fewer clouds and higher temperatures. (Conversely, during low periods of solar magnetic activity, more cosmic rays reach the Earth, which causes more clouds and lower temperatures.)
Svensmark remarks, “Evidence from ice cores show this [lower solar activity, high cosmic rays, and lower temperatures] happening long into the past. We have the highest solar activity we have had in at least 1,000 years.”
Svensmark’s theory counters the highly publicized report published last week from 2,500 scientists at the United Nations (UN) International Panel on Climate Change. He states that the UN report overlooks the affect of cosmic rays on global warming, which could mean humans are adversely affecting the Earth’s climate to a lesser degree than natural processes—specifically, naturally produced cosmic rays.
The five-year research project by Svensmark and collaborators is to be published later in 2007 as a journal article in the Proceedings of the Royal Society Journal A: Mathematical, Physical and Engineering Sciences and as a March 2007 book called “The Chilling Stars: A New Theory of Climate Change”. The book, co-authored by Nigel Calder, simulated the atmosphere of the Earth by placing atmospheric gases into a large reaction chamber with ultraviolet light. The experiment found that microscopic droplets formed in the chamber. Based on such experimentation, Svensmark says that cosmic rays create clouds that reflect solar energy back into space, which cools the Earth. When the Sun is more active, it protects the Earth from many cosmic rays, which causes fewer clouds, and the Earth warms due to more solar energy reaching the Earth’s surface.
Svensmark’s conclusions are not without controversy. Other scientists say that the relationship between cosmic rays and clouds is not as important as claimed by Svensmark. However, still other scientists are looking into Svensmark’s research as a genuine conclusion for global warming. For example, U.S. physicist S. Frederick Singer and U.S. economist Dennis T. Avery published in December 2006 the book “Unstoppable Global Warming Every 1500 Years”, which states global warming is due to a natural 1,500-year climate cycle on the Earth.
Another group of scientists is beginning an experiment to simulate cosmic rays impinging on the Earth’s atmosphere by using a particle accelerator (a device that uses an electric field to thrust charged particles to very high speeds) located in Geneva, Switzerland.
A majority of scientists currently believe that human produced carbon dioxide emissions are largely responsible for artificially produced global warming. Other scientists disagree, with many citing naturally occurring processes as the prime cause of naturally produced global warming.
The home Web page for the Danish National Space Center is: http://www.spacecenter.dk/.
The home Web page for The Royal Society is: http://www.pubs.royalsoc.ac.uk/index.cfm?page=1086.
The home Web page for the United Nations International Panel on Climate Change is: http://www.ipcc.ch/.