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1 Solar Sources of Cosmogenic Radionuclide Variations R. Muscheler, J. Beer, M. Vonmoos, F. Joos, S.A. Müller, I. Snowball Background Solar Third modulation level during the last 1000 years Solar modulation during the last 11,500 years Outlook & Conclusion 1

2 Background - The Production 2

3 Background - The Production Are earlier Second results level by Masarik & Beer (JGR 1999) or Lal (1988) outdated? 3

4 Background - The Production -> results do not depend on the production model 4

5 Background - The Radionculide Systems 5

6 Solar modulation during the last 1000 years Bard et al., Tellus 2000 A shorter period is centered at about 1200 yr AD, with irradiance slightly higher or similar to present day values Based on 10 Be from the South Pole Usoskin et al., PRL 2003 The reconstruction shows reliably that the period of high solar activity during the last 60 years is unique throughout the past 1150 years Based on sunspots & 10 Be from Southern Greenland 6

7 Solar modulation during the last 1000 years An alternative approach based on 14 C Suess effect bomb tests 7

8 Solar modulation during the last 1000 years 14 C production rate (sun) versus 14 C (measurements) 8

9 Solar modulation during the last 1000 years An alternative approach based on 14 C constant carbon cycle fossil CO 2 emissions prescribed after 1850 yr AD 13 C changes as independent test northern and southern hemisphere 14 C in 3-D model runs included Monte-Carlo simulations to assess the errors systematic variations of the most uncertain parameters in the model Muscheler et al., Nature

10 Solar modulation during the last 1000 years 14 C production rate Muscheler et al. ESR, submitted 10

11 Solar modulation during the last 1000 years How can we connect the 14 C record to present day values? 11

12 Solar modulation during the last 1000 years How can we connect the 14 C record to present day values? 12

13 Solar modulation during the last 1000 years How can we connect the 14 C record to present day values? 13

14 Solar modulation during the last 1000 years How Click can we connect to edit the 14 Master C record to present title style day values? The sunspot record as a test for the quality of our approach? 14

15 Solar modulation during the last 1000 years How can we correct for the geomagnetic field influence? 15

16 Solar modulation during the last 1000 years How can we correct for the geomagnetic field influence? 16

17 Solar modulation during the last 1000 years Muscheler et al. submitted NH 14 C data, Cheltenham normalisation & Yang geomagnetic record 17

18 Solar modulation during the last 1000 years Muscheler et al. submitted global 14 C data, Cheltenham normalisation & Yang geomagnetic record 18

19 Solar modulation during the last 1000 years Muscheler et al. submitted NH 14 C data, Cheltenham normalisation & Korte&Constable geomagnetic record 19

20 Solar modulation during the last 1000 years Muscheler et al. submitted Balloon-borne normalisation 20

21 1 0 B e Solar modulation during the last 1000 years Several records for the last 1000 years from Greenland & Antarctica 3 records that cover the last 100 years Records from Greenland indicate strong increase in the 2. half of the 20 th century Records from Antarctica do not show this increase 21

22 Solar modulation during the last 1000 years Muscheler et al. submitted 22

23 Independent estimates Click to edit Ti in meteorites Master title style Castagnoli et al.,

24 Independent estimates Click to edit Ti in meteorites Master title style 24

25 Solar modulation during the last years Are there long-term changes in solar activity and can we reliably reconstruct them? Solanki et al., Nature

26 Solar modulation during the last years tree-ring 14 C measurements Stuiver et al.,

27 Solar modulation during the last years 14 C production rate Stuiver et al., 1998 Muscheler et al., QSR

28 Solar modulation during the last years Geomagnetic Field Comparison Muscheler et al.,qsr

29 Solar modulation during the last years Solar Modulation estimates: 10 Be & Yang geomagnetic field record indicate a different long-term trend; Vonmoos et al., submitted 14 C & alternative geomagnetic field estimates indicate a different long-term trend Snowball et al., submitted based on 14 C & Yang geomagnetic field record Long-term changes within the errors of Yang et al.,

30 Solar modulation during the last years Long-term (T> years) changes are very uncertain! What are the robust features in the estimates of past solar forcing? 30

31 Solar modulation during the last years Short-term changes (on time scales shorter than approx. Second 1000 level years) indicated by ice core 10 Be and treering 14 C records agree well. Independent geomagnetic field estimates cannot explain these short-term changes 31

32 Solar modulation during the last years Spectrum: 10 Be & 14 C Holocene relative intensity yr cycle 88 yr cycle 14 C 10 Be frequency [years -1 ] 32

33 Solar modulation during the last years 33

34 Conclusions Comparison of different radionuclide records is crucial to obtain reliable estimates of solar forcing Long-term changes are not well constrained due geomagnetic field uncertainties and potential changes in the radionuclide systems Short-term changes in solar modulation are well constrained Today s levels of solar magnetic modulation are high but not exceptional compared to the last 1000 years and before 34