2nd PAGES Solar Forcing Workshop: Constraining Solar Forcing by “Detection and Attribution” for the Holocene

20.05 - 23.05.2014
Davos, Switzerland
Contact person:
Juerg Beer & Werner Schmutz, This email address is being protected from spambots. You need JavaScript enabled to view it.
Workshop report: 
> Access


During the first workshop of PAGES Solar Forcing Working Group in Sep 2012 in Davos, it became clear that a direct approach to reconstruct past solar forcing is extremely difficult. There is general agreement that solar forcing is related to the magnetic activity on the solar surface and is lower during grand minima such as the Maunder Minimum. However, it is not known how much lower the Total Solar Irradiance (TSI) was.

Sophisticated models reproduce the recent short-term changes in TSI observed by satellite-based radiometers for recent times. However, it is unclear whether these models can also reproduce centennial changes. In addition, these models require a large amount of information about the solar magnetic activity which is not available for pre-instrumental times.

Finally, even for the satellite period there is no agreement on how to combine the raw data into a composite. (A group consisting of authors of three composites is currently trying to sort out their discrepancies at ISSI in Bern.)

The situation may improve in the future. Important information is expected from evidence that the period of high solar activity comes to an end and approaches a new grand minimum before the end of this century. The last solar cycle minimum (2009) was already very low, the next will probably be even lower and may allow us to study the Sun in a state considerably different from anything we have seen for a century.

Workshop aims

As a consequence, we want to explore estimating the change in TSI between solar maximum and solar minimum from climate records. The Holocene is characterized by about 25 grand minima. Studying these minima should help us to estimate the range of solar forcing. However, this approach is hampered by interferences with volcanic forcing, and feedback mechanisms. Therefore we plan with a detection attribution approach to select the most promising grand solar minima which then can be used to better constrain the solar forcing.

The ultimate goal of the Solar Forcing Working Group is to provide more accurate, longer and better resolved forcing records. While the relative changes of the forcing are rather well known, the absolute changes are highly uncertain. Starting from the observed climate change and working out the necessary forcing backwards is an attempt to reduce this uncertainty.

Planned products

The main product this workshop will be a review paper integrating the conclusions from the first workshop (held in Davos, Sep 2012). After a review of the present status the main emphasis will be to present strategies how to reduce the uncertainty in solar forcing for the Holocene.


Tuesday 20 

Wednesday 21

 Thursday 22

Friday 23 

Saturday 24




 Solar Forcing











The following keynote speakers have already confirmed their participation. Three are still pending:
Bradley, R., Fleitmann, D., Hegerl, G., Luterbacher, J., Muscheler, R., Raible, C., Rozanov, E., Shapiro, A.I., Wanner, H., Woods, T., Zorita, E.


The workshop starts on Tuesday, May 20 at 9 am in the pmod/wrc observatory in Davos ( On Saturday there will be an excursion/hike. The details depend on the local weather/snow conditions and will be communicated during the workshop.

Post-meeting material

> Presentations and posters