『Abstract
The Sun has an obvious effect on climate since its radiation
is the main energy source for the outer envelopes of our planet.
Nevertheless, there is a long-standing controversy on whether
solar variability can significantly generate climate change, and
how this might occur. This is a crucial issue not only in the
field of paleoclimatology, but also for predicting the future
of the Earth's climate, which will be subject to perturbations
by anthropogenic greenhouse gases. Indeed, if climate changes
due to the Sun were large and rapid, this would make it more difficult
to extract the anthropogenic effects from precise records of instrumental
data over the past century. Hence, Sun-climate relationships have
never been so controversial as today, forming a debate that often
escapes the scientific arena.
Here, we provide a review of this problem by considering changes
on different time scales, from the last million years up to recent
decades. In doing so, we also critically assess recent claims
that the variability of the Sun has had a significant impact on
global climate. The different studied record also illustrate the
multi-disciplinary nature of this difficult problem, requiring
knowledge in several fields such as astronomy and astrophysics,
atmospheric dynamics and microphysics, isotope geochemistry and
geochronology, as well as geophysics, paleoceanography and glaciology.
Overall, the roll of solar activity in climate changes - such
as the Quaternary glaciations or the present global warming -
remains unproven and most probably represents a second-order effect.
Although we still require even more and better data, the weight
of evidence suggests that solar changes have contributed to small
climate oscillations occurring on time scales of a few centuries,
similar in type to the fluctuations classically described for
the last millennium: The so-called Medieval Warm Period (900-1400
A.D.) followed on by the Little Ice Age (1500-1800 A.D.).
Keywords: solar activity; climate forcing; cosmogenic isotopes;
geomagnetic field』
1. Introduction
2. Has the warming observed during the past decades been partly
linked to solar variability?
3. Has solar forcing been the main cause of climate change over
the past few centuries?
4. Was there any solar modulation of climate during the Holocene
period?
5. Solar variability and climate on orbital time scales
6. Conclusions
Acknowledgments
References