Cosmic Rays and Climate Change: Empirical Evidence and Experimental Findings

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 SN1993JSN 1993J VLBI. III. The Evolution of the Radio ShellM. F. Bietenholz , N. Bartel , and M. P. RupenThe Astrophysical Journal, 597:374-398, 2003 5000 AU 8.4 GHz, from t = 50d to t = 2787d

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

5. Cosmic ray shower (Movie) About 70 muons/s /m2 at the Earths surface In 24 hours about 12 million muons goes through a human body

6. Cosmic rays and climate over the last 10.000 years Bond et al, Science 294, 2001 According to icecores CO2 levels has been constant ~280 ppm 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

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. Cosmic rays and climate over the last millennium ”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

9. How can STARS influence Climate? Net effect of clouds is to cool the Earth by about 30 W/m2

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

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

12. Aerosol formation and growth Possible link between clouds and cosmic rays CN (Condensation Nuclei) Cloud Drop H2SO4 & Water & Organic Vapors UCN (Ultra Fine Condensation Nuclei) CCN (Cloud Condensation Nuclei) Size 0.1 mm 0.001 mm 0.01 mm 10 mm Nucleation process is unsolved

13. - + Cosmic Ray Ionization & Aerosol formation and growth CN (Condensation Nuclei) Cloud Drop H2SO4 & Water Vapors UCN (Ultra Fine Condensation Nuclei) CCN (Cloud Condensation Nuclei) Size 0.1 mm 0.001 mm 0.01 mm 10 mm What is the importance of IONS ?

14. Atmospheric conditions! SKY experiment 2002 - 2006 Gamma source Gamma source Muon detector Radon detector SO2 O3 H2O

15. q (cm-3 s-1) 0 10 20 30 40 50 60 Steady state experiment H2SO4 concentration ~ 2*108 (cm-3) O3 ~ 25 ppb SO2 ~ 300 ppt RH ~ 35% Svensmark et al. Proc. R. Soc. A (2007) 463, 385–396

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

17. Coronal Mass EjectionsNatural experiments for testing the GCR-atmosphere link

18. A Classic Forbush Decrease

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

20. Ranking the Forbush events For each Forbush decrease 120 Neutron monitors ( Pm range 10 GV – 47 GV) Nagoya Muon monitors ( Pm 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 104 Cosmic ray Showers in the atmosphere. Change in IONIZATION 0-3 km 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 dM ~ 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. A hint from observations of a mechanism The presence of aerosols in the atmosphere affect the color of the sun as seen from the ground.

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. - + Typical gas phase Aerosol Cloud formation and growth CN (Condensation Nuclei) Cloud Drop H2SO4 & Water Vapors UCN (Ultra Fine Condensation Nuclei) CCN (Cloud Condensation Nuclei) Size 0.1 mm 0.001 mm 0.01 mm 10 mm Ion induced formation of aerosols

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