Exploding Stars Influence Climate Of Earth
- May explain part of the the small bump in global temperatures during
the 2nd quarter of the the 20th century. Pat N
Exploding Stars Influence Climate Of Earth
Cosmic radiation entering Earth's atmosphere. Credit: Danish
National Space Center.
by Staff Writers
Copenhagen, Denmark (SPX) Oct 06, 2006
A team at the Danish National Space Center has discovered how cosmic
rays from exploding stars can help to make clouds in the atmosphere.
The results support the theory that cosmic rays influence Earth's
An essential role for remote stars in everyday weather on Earth has
been revealed by an experiment at the Danish National Space Center
It is already well-established that when cosmic rays, which are high-
speed atomic particles originating in exploded stars far away in the
Milky Way, penetrate Earth's atmosphere they produce substantial
amounts of ions and release free electrons.
Now, results from the Danish experiment show that the released
electrons significantly promote the formation of building blocks for
cloud condensation nuclei on which water vapour condenses to make
Hence, a causal mechanism by which cosmic rays can facilitate the
production of clouds in Earth's atmosphere has been experimentally
identified for the first time.
The Danish team officially announced their discovery on Wednesday in
Proceedings of the Royal Society A, published by the Royal Society,
the British national academy of science.
The experiment called SKY (Danish for "cloud") took place in a large
reaction chamber which contained a mixture of gases at realistic
concentrations to imitate the chemistry of the lower atmosphere.
Ultraviolet lamps mimicked the action of the Sun's rays. During
experimental runs, instruments traced the chemical action of the
penetrating cosmic rays in the reaction chamber.
The data revealed that electrons released by cosmic rays act as
catalysts, which significantly accelerate the formation of stable,
ultra-small clusters of sulphuric acid and water molecules which are
building blocks for the cloud condensation nuclei. A vast numbers of
such microscopic droplets appeared, floating in the air in the
"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 team leader Henrik Svensmark, who is
Director of the Center for Sun-Climate Research within the Danish
National Space Center. "This is a completely new result within
A missing link in climate theory
The experimental results lend strong empirical support to the theory
proposed a decade ago by Henrik Svensmark and Eigil Friis-
Christensen that cosmic rays influence Earth's climate through their
effect on cloud formation.
The original theory rested on data showing a strong correlation
between variation in the intensity of cosmic radiation penetrating
the atmosphere and the amount of low-altitude clouds. Cloud cover
increases when the intensity of cosmic rays grows and decreases when
the intensity declines.
It is known that low-altitude clouds have an overall cooling effect
on the Earth's surface. Hence, variations in cloud cover caused by
cosmic rays can change the surface temperature. The existence of
such a cosmic connection to Earth's climate might thus help to
explain past and present variations in Earth's climate.
Interestingly, during the 20th Century, the Sun's magnetic field
which shields Earth from cosmic rays more than doubled, thereby
reducing the average influx of cosmic rays.
The resulting reduction in cloudiness, especially of low-altitude
clouds, may be a significant factor in the global warming Earth has
undergone during the last century. However, until now, there has
been no experimental evidence of how the causal mechanism linking
cosmic rays and cloud formation may work.
"Many climate scientists have considered the linkages from cosmic
rays to clouds to climate as unproven," comments Eigil Friis-
Christensen, who is now Director of the Danish National Space Center.
"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."