Brussels, 18 October 2006
Adding another ingredient to the recipe for global warming, Danish researches have published findings indicating that cosmic rays play a role cloud formation, which in turn influences ground temperatures. The results were first published in the UK's Proceedings of the Royal Society A.
Specifically, scientists observed the effects of electrons released by cosmic rays after they hit the Earth's atmosphere. The project SKY, which means 'cloud' in Danish, created a chamber with an mix of particles to mirror the Earth's atmosphere minus the pollution. They added UV lamps to mimic the suns effects and then observed what happened when cosmic rays naturally entered the chamber.
Cosmic rays are made up of high energy particles released when a star explodes, and when mixed with the Earth's atmosphere they emit free electrons.
The Danish researchers observed that the released electrons significantly promote the formation of stable, ultra-small clusters of sulphuric acid and water molecules that constitute the building blocks of clouds.
"We were amazed by the speed and efficiency with which the electrons do their work of creating the building blocks for the cloud condensation nuclei," says Henrik Svensmark, Director of the Center for Sun-Climate Research within the Danish National Space Center. "This is a completely new result within climate science."
The findings lend support to a theory proposed by Mr Svensmark and Danish National Space Center Director Eigil Friis-Christensen ten years ago. They noticed a relationship between the intensity of cosmic rays penetrating the atmosphere and the prevalence of low altitude clouds, but lacked empirical evidence to corroborate their suspicions.
Researchers have recorded in increase throughout the 20th century of the Sun's magnetic field around the Earth which deflects such cosmic rays. Clouds can themselves deflect the suns rays resulting in a cooling effect for the planet. If there has been a decrease in cloud cover due to a decrease in cosmic rays, as SKY suggests, that may explain a rise in overall temperatures experienced on Earth.
"Many climate scientists have considered the linkages from cosmic rays to clouds to climate as unproven," says Mr Friis-Christensen. "Some said there was no conceivable way in which cosmic rays could influence cloud cover. The SKY experiment now shows how they do so, and should help to put the cosmic-ray connection firmly onto the agenda of international climate research."
It remains to be seen exactly how climatologists will interpret SKY's results.