1. Cosmic rays and climate change Henrik Svensmark, Center for Sun Climate Research Space DTU

2. Cosmic rays and climate change Cosmic rays and climate –Definitions –Empirical evidence Experimental efforts and results Does is work in the real atmosphere?

3. Evolution of SN1993J SN 1993J VLBI. III. The Evolution of the Radio Shell M. F. Bietenholz, N. Bartel, and M. P. Rupen The Astrophysical Journal, 597:374-398, 2003 8.4 GHz, from t = 50d to t = 2787d 5000 AU

4. What are Cosmic Rays? Heliosphere, Cosmic Rays and Solar Activity

5. Cosmic ray shower (Movie) About 70 muons/s /m 2 at the Earths surface In 24 hours about 12 million muons goes through a human body

6. 6 Cosmic rays and climate over the last 10.000 years Bond et al, Science 294, 2001 Last 1000 years Little Ice Age Little Ice Age is merely the most recent of a dozen such events during the last 10.000 years Adapted from Kirkby According to icecores CO 2 levels has been constant ~280 ppm

7. Strong coherence between solar variability and the monsoon in Oman between 9 and 6 kyr ago The formation of stalagmites in northern Oman has recorded past northward shifts of the intertropical convergence zone3, whose northward migration stops near the southern shoreline of Arabia in the present climate U. Neff et al., Nature 411, 290 - 293 (2001)

8. ”Since everybody thought that the continous crop faliure was caused by witches from devilish hate, the whole contry stood up for their eradication” Johann Linden Travis ca. 1590 Cosmic rays and climate over the last millennium

9. How can STARS influence Climate? Net effect of clouds is to cool the Earth by about 30 W/m 2

10. Svensmark & Friis-Christensen, JASTP 1997, Svensmark, PRL 1998, Marsh & Svensmark, PRL, 2000. (update 2005) Link between Low Cloud Cover and Galactic Cosmic Rays? Solar cycle variation ISCCP IR Low cloud data Calibration? 10 0 -10 -20

11. If the link is between cosmic rays and clouds, what would the mechanism be? Empirical evidence for a relation between cosmic rays and climate

12. Cloud Drop CCN (Cloud Condensation Nuclei) CN (Condensation Nuclei) UCN (Ultra Fine Condensation Nuclei) 0.1  m 10  m0.01  m0.001  m Aerosol formation and growth Size H 2 SO 4 & Water & Organic Vapors Possible link between clouds and cosmic rays Nucleation process is unsolved

13. Cloud Drop CCN (Cloud Condensation Nuclei) CN (Condensation Nuclei) UCN (Ultra Fine Condensation Nuclei) 0.1  m 10  m0.01  m0.001  m Aerosol formation and growth Size H 2 SO 4 & Water Vapors What is the importance of IONS ? - + Cosmic Ray Ionization &

14. Gamma source Muon detector Radon detector SO 2 O 3 H 2 O Atmospheric conditions! SKY experiment 2002 - 2006

15. Steady state experiment 0 10 20 30 40 50 60 q (cm -3 s -1 ) H 2 SO 4 concentration ~ 2*10 8 (cm -3 ) O 3 ~ 25 ppb SO 2 ~ 300 ppt RH ~ 35% Svensmark et al. Proc. R. Soc. A (2007) 463, 385–396

16. Does it work in the real atmosphere? Statements 1.There are always plenty of CCN in the atmosphere a few more will not matter. 2.It is not important.

17. Coronal Mass Ejections N atural experiments for testing the GCR-atmosphere link

18. A Classic Forbush Decrease

19. Cosmic ray energy change during Forbush Decrease Local interstellar Spectrum Heliosphere Forbush decrease Neutron monitors South Pole Climax Huncayo

20. 120 Neutron monitors ( P m range 10 GV – 47 GV) Nagoya Muon monitors ( P m range 60 GV – 119 GV) Change in COSMIC RAY Spectrum 0- 120 GeV at 1 AU (Distance of Earth) Monte Carlo Simulation with CORSIKA of 10 4 Cosmic ray Showers in the atmosphere. Change in IONIZATION 0-3 km Ranking the Forbush events For each Forbush decrease Ranking

21. Twenty-six FD events in the period 1987-2007 Ranked according to their depression of ionization in the Earth’s lower atmosphere (< 3 km) Svensmark, Bondo and Svensmark 2008

22. 5 strongest Forbush decreases: SSM/I data Liquid water content of clouds over oceans NOTE: SSM/I data Ionization change ~ 10% Liquid water change ~ 6% Suggest that a large fraction of clouds are influenced by ionization  M ~ 3 Gton

23. AERONET, SSM/I, MODIS and ISCCP data for 5 strongest Forbush decreases Aerosols Clouds Liquid water Liquid cloud fraction Low Clouds

24. The presence of aerosols in the atmosphere affect the color of the sun as seen from the ground. A hint from observations of a mechanism

25. AERONET data Angström exponent: is the aerosol optical thickness dependence of wavelength. The Angström exponent is inversely related to the average size of the particles: the smaller the particles, the larger the exponent. For shorter wave lengths (340,380,440,500 nm) a decrease will mean fewer small particles. 5 strongest events Fewer small particles Angström exponent Svensmark, Bondo and Svensmark 2008

26. Cloud Drop CCN (Cloud Condensation Nuclei) CN (Condensation Nuclei) UCN (Ultra Fine Condensation Nuclei) 0.1  m 10  m0.01  m0.001  m Size H 2 SO 4 & Water Vapors Ion induced formation of aerosols - + Typical gas phase Aerosol Cloud formation and growth

27. Prediction The near future: Cooling The sun will show how important it is

28. Conclusion Variation in cosmic rays are associated with changes in Earths climate. Strong empirical evidence. (not discussed: long time scales e.g. million of years) Evidence suggest that clouds are the key player. New insight to the physical mechanism has been demonstrated experimentally and observationally Involving ions and aerosol formation Involving ions and aerosol formation Linking to clouds and thereby the energy budget of the Earth Linking to clouds and thereby the energy budget of the Earth Observations further suggest that a large fraction of clouds are influenced by ionization. (6% change in liquid water for a 10 % change in ionization)Observations further suggest that a large fraction of clouds are influenced by ionization. (6% change in liquid water for a 10 % change in ionization) Understanding the cosmic ray climate link could have large implications in our understanding of climate changes. The theory ”Cosmic rays and climate” is alive and strong

29. Thanks: Torsten Bondo Jacob Svensmark Martin Enghoff Nigel D. Marsh Nigel Calder Jens Olaf Pedersen Ulrik I. Uggerhøj Sean Paling Center for Sun-Climate Research DTU-space