Cosmic rays, clouds and climate change

• Cosmic rays and climate – Definitions

– Empirical evidence

• Experimental efforts and results– Microphysical mechanism?

• Impact on the real atmosphere– Natural experiments with Earth (Forbush decreases)

– Ocean heat content (1950 – 2010)

Henrik Svensmark, Center for Sun Climate Research

Space, DTU

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

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

Strong coherence between solar variability and the monsoon in Omanbetween 9 and 6 kyr ago

The formation of stalagmites in northern Oman has recorded past northwardshifts of the intertropical convergence zone3, whose northward migration stops near the southern shoreline of Arabia in thepresent climate

U. Neff et al., Nature 411, 290 - 293 (2001)

”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

Solar irradiance too small, amplification needed!

How can STARS influence Climate?

Net effect of clouds is to cool the Earth by about 30 W/m2

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

If the link is between cosmic rays and clouds, what would the mechanism be?

Empirical evidence for a relation between cosmic rays and climate

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

H2SO4 &

Water&

OrganicVapors

Possible link between clouds and cosmic rays

Nucleation processis unsolved

An aerosol is a small cluster of molecules floating in the air

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

H2SO4 &

Water

Vapors

What is the importance of IONS ?

-

+

Cosmic Ray Ionization &

Gamma source Gamma source

Muon detector Radon detectorSO2

O3

H2O

Atmospheric conditions!SKY experiment2002 - 2006

Steady state experiment

0 10 20 30 40 50 60 q (cm-3 s-1)

H2SO4 concentration ~ 2*108 (cm-3)

O3 ~ 25 ppbSO2 ~ 300 pptRH ~ 35%

Svensmark et al. Proc. R. Soc. A (2007) 463, 385–396

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.

Coronal Mass EjectionsNatural experiments for testing the GCR-atmosphere link

SOHO satellite, one month of observation

Haloween event 2003

A Classic Forbush Decrease

AERONET, SSM/I, MODIS and ISCCP data for 5 strongest Forbush decreases

Aerosols Clouds

Liquid water Liquid cloud fraction Low Clouds

Svensmark, Bondo and Svensmark, GRL

Cloud Drop

CCN(Cloud Condensation Nuclei)

CN(Condensation Nuclei)

UCN(Ultra Fine Condensation Nuclei)

0.1 m 10 m0.01 m0.001 mSize

H2SO4 &

Water

Vapors

Ion induced formation of aerosols

-

+

Typical gas phase Aerosol Cloud formation and growth

From solar activity to cosmic ray ionization to aerosols and liquid-water clouds, a causal chain appears to operate on a global scale

Ocean Heat Content 1950 – 2010 (0-700m)

Levitus et al.Domingues et al.Ishii and M. Kimoto

Ocean Heat Content

1) Volcanoes, (aerosol index)

2) Solar Activity, (cosmic ray variation)

3) Regime shift in 1977, (natural variability)

4) Net antropogenic, (residual)

H (Heat Content)

FSimple Model

Modelled forcings

Ocean Heat Content

Svensmark

Volcanoes

Solar influence

Year

Solar cycle amplitude consistent with the findings of Nir Shaviv

Forcing

Heat Content

Svensmark

Regime Shift in 1977

HadAT2 tropospheric temperatures (0 – 10 km)

Regime shift

850hPa 700hPa 500hPa 300hPa 200hPa

Ocean Heat ContentDomingues et al.

Levitus et al.

Ishii & Kimoto

If solar activity and the regime shift is ignored the net anthropogeniccontribution increases with a factor 2-5

Conclusion

Variation in cosmic rays are associated with changes in Earths Variation in cosmic rays are associated with changes in Earths climate. Strong empirical evidence. (not discussed: long time scales climate. Strong empirical evidence. (not discussed: long time scales e.g. million of years)e.g. million of years)

Evidence suggest that clouds are the key player.Evidence suggest that clouds are the key player.

New insight to the physical mechanism has been demonstrated New insight to the physical mechanism has been demonstrated experimentally and observationallyexperimentally and observationally• Involving ions and aerosol formationInvolving ions and aerosol formation• Linking to clouds and thereby the energy budget of the EarthLinking to clouds and thereby the energy budget of the Earth•Observations further suggest that a large fraction of clouds are Observations further suggest that a large fraction of clouds are influenced by ionization. (6% change in liquid water for a 10 % influenced by ionization. (6% change in liquid water for a 10 % change in ionization)change in ionization)

A large fraction of the recent increase in ocean heat content could be A large fraction of the recent increase in ocean heat content could be due to natural causes: Solar influence and a regime shift in 1977due to natural causes: Solar influence and a regime shift in 1977

The theory ”cosmic rays and climate” is alive and strong The theory ”cosmic rays and climate” is alive and strong