stars cause climate change

I contributed to this research see my posts from August 11, 2003

Danish National Space Center
Copenhagen, Denmark


For further information, please contact:


Sune Nordentoft Lauritsen
Danish National Space Center
Tel: +45 35325700


2007-02-26


Cosmoclimatology: A new theory of climate change


Remarkable results of research on cosmic rays and climate at the
Danish
National Space Center are summarized this month in a review for the
Royal
Astronomical Society in London.


The leader of Sun-climate research at the Danish National Space
Center,
Henrik Svensmark, puts together the findings reported by him and his
colleagues in a dozen scientific papers, to tell how the climate is
governed
by atomic particles coming from exploded stars. These cosmic rays help
to
make ordinary clouds. High levels of cosmic rays and cloudiness cool
the
world, while milder intervals occur when cosmic rays and cloud cover
diminish.


The review paper entitled 'Cosmoclimatology: a new theory emerges'
appears
in the February issue of Astronomy & Geophysics. Here are some of its
salient points.


For more than 20 years, satellite records of low-altitude clouds have
closely followed variations in cosmic rays. Just how cosmic rays take
part
in cloud-making appeared in the SKY experiment
[http://www.spacecenter.dk/research/sun-climate/sky], conducted in
the
basement of the Danish National Space Center. Electrons set free in
the air
by passing cosmic rays help to assemble the building blocks for cloud
condensation nuclei on which water vapour condenses to make clouds.


Cosmic ray intensities -- and therefore cloudiness -- keep changing
because
the Sun's magnetic field varies in its ability to repel cosmic rays
coming
from the Galaxy, before they can reach the Earth. Radioactive
carbon-14 and
other unusual atoms made in the atmosphere by cosmic rays provide a
record
of how cosmic-ray intensities have varied in the past. They explain
repeated
alternations between cold and warm periods during the past 12,000
years.
Whenever the Sun was feeble and cosmic-ray intensities were high,
cold
conditions ensued, most recently in the Little Ace Age that climaxed
300
years ago.


On long timescales the intensity of cosmic rays varies more
emphatically
because the influx from the Galaxy changes. During the past 500
million
years the Earth has passed through four 'hothouse' episodes, free of
ice and
with high sea levels, and four 'icehouse' episodes like the one we
live in
now, with ice-sheets, glaciers and relatively low sea levels.


Nir Shaviv of the Hebrew University in Jerusalem, together with J
Veizer of
the Ruhr University and the University of Ottawa, links these changes
to the
journey of the Sun and the Earth through the Milky Way Galaxy. They
blame
the icehouse episodes on encounters with bright spiral arms, where
cosmic
rays are most intense. More frequent chilling events, every 34 million
years
or so, occur whenever the solar system passes through with the mid-
plane of
the Galaxy.


In Snowball Earth episodes around 700 and 2300 million years ago, even
the
Equator was icy. At those times the birth-rate of stars in the Galaxy
was
unusually high, which would have also meant a large number of
exploding
stars and intense cosmic rays. Earlier still, the theory of cosmic
rays and
clouds helps to explain why the Earth did not freeze solid when it was
very
young. The Sun was much fainter than it is now, but also more vigorous
in
repelling cosmic rays, so the Earth would not have had much cloud
cover.


While calculating the changing influx since life began about 3.8
billion
years ago, Dr Svensmark discovered a surprising connection between
cosmic-ray intensities and a variability of the productivity of life.
The
biggest fluctuations in productivity coincided with high star
formation
rates and cool periods in the Earth's climate. Conversely, during a
billion
years when star formation was slow, cosmic rays were less intense and
the
Earth's climate was warmer, the biosphere was almost unchanging in
its
productivity.


Near the end of his review Dr Svensmark writes: "The past 10 years
have seen
the reconnaissance of a new area of research by a small number of
investigators. The multidisciplinary nature of cosmoclimatology is
both a
challenge and an opportunity for many lines of inquiry." Even the
search for
alien life is affected, because it should now take into account of the
need
for the right magnetic environment, if life is to originate and
survive on
the planets of other stars.


'Cosmoclimatology: a new theory emerges', Henrik Svensmark, Astronomy
&
Geophysics, Vol. 48, Issue 1, pages 1.18-1.24, February 2007


Notes for Editor


Dr Svensmark has also written a plain-language book on the same
theme,
jointly with the British science writer Nigel Calder. Entitled The
Chilling
Stars: A New Theory of Climate Change, it is published in the UK this
week
by Icon Books : www.iconbooks.co.uk/book.cfm?isbn=1-84046-815-7