Cosmoclimatology: A new theory of climate change (Forwarded)

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 Ján 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

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

Astronomy & Geophysics is published for the Royal Astronomical Society by
Blackwell Synergy:
http://www.blackwell-synergy.com/toc/aag/48/1

*****

Danish National Space Center
Copenhagen, Denmark

2007-03-19

Global warming and cosmic radiation

What does cosmic radiation have to do with global warming? Read more about
what researchers at the DNSC think.

The Earth's climate is always changing. This has been the case in the
geological and historical time and even during the last 150 years, where
systematic climate measurements have been made, we have seen clear climate
changes.

Climate changes have both a scientific and a social perspective. The
social perspective is associated with the range of climate change that can
be attributed to the increasing human induced contribution. The scientific
perspective is an endeavour to understand the full complex system of the
various sources of climate change and their mutual interactions.

The Danish National Space Center, DNSC, comprises the country's largest
collected expertise in the scientific disciplines that play a major and
documented role in the understanding of climate change both in geological
and historical time, namely variations in solar activity. DNSC regards it
essential that this collected expertise is being used in an attempt to
understand the natural causes of climate change in order to evaluate the
contribution of natural causes to global change. Taking into account the
large uncertainty associated with the estimated human contribution, a good
research based estimate of the range of natural climate variations is an
essential information.

DNSC is basing its effort in this area on own scientific results --
observational, experimental, and theoretical. The scientific results have
been published internationally and indicate that the varying activity of
the Sun is indeed the largest and most systematic contributor to natural
climate variations. The effect goes through solar modulation of the cosmic
radiation, which affects the formation of aerosols and thereby also the
formation of clouds. Even though a physical mechanism connecting cosmic
rays to aerosol formation has been found experimentally, no climate model
has yet made an attempt to include such an effect.

That there exists a significant contribution from solar activity
variations to global temperature increase does not, however, exclude other
contributions to the rising global temperature, natural as well as human.
DNSC, however, is focused on establishing the best possible and
scientifically based evaluation of the size of solar induced effects on
climate.