scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Reconstructing solar activity with applications in climate change.
Solanki Sami K.
Max-Planck-Institute for Solar System Research
The Sun is a variable star, with all aspects of solar activity displaying a distinct cyclic
variation as well as changes on other time scales. E.g. since 1978 measurements have revealed
that the Sun varies in brightness on time scales from minutes to the solar cycles. With the
current minimum a new aspect has been revealed: the fact that the solar brightness is not
always the same at solar activity minimum, i.e. there irradiance also displays a secular
variation.
The magnetic field is most likely responsible for the variation of solar irradiance, just as it is
for other aspects of solar activity. Models have been increasingly successful in reproducing
the measured solar irradiance. In some respects, measurements have even lagged behind the
models, a rarity in solar physics. Thus, models have been predicting for years that solar
irradiance displays a significant secular variation. During the current activity minimum these
predictions have finally been borne out by measurements.
In order to detect the influence of solar variability on climate, longer time series than, e.g., the
solar irradiance record are needed to complement studies on shorter time-scales. This requires
models computing essential quantities, such as irradiance or open magnetic flux from sunspot
numbers (available since 1610). At earlier times, even sunspot numbers or other measures of
solar activity are not available and need to be reconstructed from cosmogenic isotopes.
Finally, reconstructed solar activity/irradiance can be compared with climate records either
directly, or via a GCM or other climate model.
This talk will give an introduction to such activities.