Cosmic Rays Influence Cloud Formation
September 5, 2013

Study Says Cosmic Rays May Influence Cloud Formation On Earth

John P. Millis, PhD for - Your Universe Online

Little more than a century ago Austrian-American physicist Victor Hess established that out in the Universe charged particles are accelerated to very high energies, some eventually making their way to Earth. While much of the research into the curiously named cosmic rays – they, in fact, are not rays at all – has focused on determining their origins, scientists have also devoted considerable effort to studying their effects on our planet.

About seven years ago, a team of Danish physicists began investigating the role that cosmic rays might play in cloud formation. They hypothesized that these charged particles entering our atmosphere would initiate the formation of small groups of molecules. Ultimately, this phenomenon could influence the formation of clouds.

However, numerical simulations of the atmospheric chemistry were inconsistent with this theory, and subsequent experiments performed with the SKY2 instrument seemed to doom the model. However, another set of experiments, also conducted with the SKY2, lent some credibility to the theory.

Prevailing wisdom is that the mixing of water molecules with sulphuric acid, created by the dissociation and recombination of sulphur dioxide, ozone and water vapor, creates clusters of molecules, driven by the ultraviolet radiation from the Sun. Once a critical density is reached, according to traditional atmospheric chemistry, the growth of the molecular clusters would cease, ending before clouds could form.

However, when natural cosmic rays and gamma rays are present to continually ionize the air, the clusters continue to grow. As a result, the presence of the high energy radiation and cosmic particle flux may be initiating a secondary chemical reaction which continues to drive the reaction.

“The result boosts our theory that cosmic rays coming from the Galaxy are directly involved in the Earth’s weather and climate,” says Henrik Svensmark, lead author of the new report. “In experiments over many years, we have shown that ionizing rays help to form small molecular clusters. Critics have argued that the clusters cannot grow large enough to affect cloud formation significantly."

"But our current research, of which the reported SKY2 experiment forms just one part, contradicts their conventional view. Now we want to close in on the details of the unexpected chemistry occurring in the air, at the end of the long journey that brought the cosmic rays here from exploded stars.”

Their paper, titled "Response of Cloud Condensation Nucelei (>50 nm) to Changes in Ion-Nucleation," appeared in the latest edition of the journal Physics Letters A.