Cosmic rays and climate change Henrik Svensmark Center

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

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

Evolution of SN 1993 J VLBI. III. The Evolution of the Radio Shell M. F. Bietenholz , N. Bartel , and M. P. Rupen The Astrophysical Journal, 597: 374 -398, 2003 5000 AU 8. 4 GHz, from t = 50 d to t = 2787 d

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

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

Cosmic rays and climate over the last 10. 000 years Bond et al, Science 294, 2001 According to icecores CO 2 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 6 the last 10. 000 years Adapted from Kirkby

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 zone 3, whose northward migration stops near the southern shoreline of Arabia in the present climate U. Neff et al. , Nature 411, 290 - 293 (2001)

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

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

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

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

Aerosol formation and growth Possible link between clouds and cosmic rays H 2 SO 4 & Water & Organic Vapors CN Cloud Drop (Condensation Nuclei) UCN CCN (Ultra Fine Condensation Nuclei) (Cloud Condensation Nuclei) Size 0. 001 mm Nucleation process is unsolved 0. 01 mm 0. 1 mm 10 mm

Cosmic Ray Ionization & Aerosol formation and growth + H 2 SO 4 & Water CN - Cloud Drop (Condensation Nuclei) Vapors UCN CCN (Ultra Fine Condensation Nuclei) (Cloud Condensation Nuclei) Size 0. 001 mm What is the importance of IONS ? 0. 01 mm 0. 1 mm 10 mm

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

Steady state experiment q (cm-3 s-1) 0 10 20 30 40 50 60 H 2 SO 4 concentration ~ 2*108 (cm-3) O 3 ~ 25 ppb SO 2 ~ 300 ppt RH ~ 35% Svensmark et al. Proc. R. Soc. A (2007) 463, 385– 396

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

Coronal Mass Ejections Natural experiments for testing the GCR-atmosphere link

A Classic Forbush Decrease

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

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 Ge. V 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

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

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 d. M ~ 3 Gton

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

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.

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. Angström exponent 5 strongest events Fewer small particles Svensmark, Bondo and Svensmark 2008

Typical gas phase Aerosol Cloud formation and growth + H 2 SO 4 & Water CN - Cloud Drop (Condensation Nuclei) Vapors UCN CCN (Ultra Fine Condensation Nuclei) (Cloud Condensation Nuclei) Size 0. 001 mm Ion induced formation of aerosols 0. 01 mm 0. 1 mm 10 mm

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

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

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