The connection between cosmic rays, clouds and climate

Transcription

1 The connection between cosmic rays, clouds and climate Martin Enghoff, Jacob Svensmark, Nir Shaviv* and Henrik Svensmark, National Space Institute of Denmark *University of Jerusalem

2 The connection between cosmic rays, clouds and climate 1. Cosmic Rays and climate Empirical evidence Cosmic rays and clouds A serious problem for the theory 2. The final piece of the puzzle The microphysical mechanism, theoretically and experimentally How relevant is cosmic rays for climate in the real atmosphere? 3. Conclusion

3 Cosmic Rays Super Nova Remnant Acceleration of cosmic rays Solar system

4 Heliosphere, Cosmic Rays and Solar Activity Cosmic Rays [%] Cosmic rays Sunspot number Sunspot Number Year 0

5 Cosmic rays in the atmosphere 20 km Incoming proton of 100 GeV Ionizes the atmosphere Produces new isotopes, e.g. 14 C, 26 Al, 10 Be 0 km ICE

6 Temperatures over the last 1000 years T anomalies - [ o C] Temperatures Medieval Warm Period Moberg et al Huang et al Morice et al Mann & Jones 2003 Little Ice Age C [%] Oort min. Wolf min. Solar activity Year Sporer min. 14 C 10 Be (Delaygue & Bard 2011) 10 Be (Beer et al. 1994) Maunder min. Dalton min Be [arbitrary units]

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

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

9 Ocean Heat Content Sea Surface Temperature Sea Level Change Altimetry Data Quantifying Solar Forcing over 11 years CLOUDS Require an amplification mechanism Total Solar Irradiance Shaviv, 2008

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

11 Precurser to clouds: Aerosols Cosmic Ray Ionization Growth CLOUD 1-2 nm stable aerosols CCN > 50 nm

12 Aerosols and microphysics of clouds Satellite observations of ship tracks Visible: 0.9 mm

13 Experimental challenges 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% ? 1-2 nm stable aerosols Svensmark et al. Proc. R. Soc. A (2007) 463,

14 So experimentally there is good evidence for the generation of ultrafine aerosols by ions ~ 1-3 nm An important remaining question: Will the small aerosols grow to Cloud Condensation Nuclei (~ 50 nm)? Nucleation If not no impact on clouds. CCN

15 RESULTS FROM GEO-CHEM-TOMAS Global Circulation Model (No ion-effects on growth) Solar cycle response Aerosols Relative change [%] NUCLEATION Expected range to explain observations CCN Diameter [nm] Data from: Snow-Kropla et al. 2011

16 Modeling says NO to an effect of ions on CCN

17 Is the theory dead again?

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

20 AERONET, SSM/I, MODIS and ISCCP data for 5 strongest Forbush decreases Aerosols Clouds Liquid water Liquid cloud fraction Low Clouds Svensmark, Bondo, Svensmark, Geo. Phys. Lett., 2009 Svensmark, Enghoff, Shaviv, Svensmark, J. Geophys Res., 2016

21 Back to our experiments

22 Experimental and theoretical challenges We spent two years on a wrong theory Experiments ruled it out GROWTH? Mainly from H 2 SO 4 H 2 O gas CLOUD 1-2 nm stable aerosols CCN > 50 nm

23 Cosmic Rays The theoretical breakthrough Ions Aerosols Ions Aerosol M aerosol +m ion - - m ion M aerosol M aerosol +m ion A so far ignored effect

24 A few numbers Growth from neutral molecules H 2 SO 4 -H 2 O ~ n 0 ~ 10 6 molecules/cm 3 Sulphuric acid-water molecule Growth from ions Ions + ~ 10 3 ions/cm 3 Aerosol Naively: GR ion /GR 0 ~ n ion / n 0 ~ 10-3 ~ 0.1% 1. Coulomb forces 2. Mirror forces 3. Van der Waals forces 4. Viscous forces Enhanced interactions GR ion /GR 0 = G(n 0, n ion, m 0, m ion,d) ~ 70 n ion n 0 ~ 10% atm. 1% exp.

25 Aerosol formation in a forest in Finland Time of day M. Boy, M. Kulmala, Atmos.Chem. Phys. 2 (2002) 1 16.

26 Experimental challenge To measure changes in aerosol growth rate of < 1% Svensmark, Enghoff, Shaviv, and Svensmark, Nature Comm. 8:2199, 2017

27 Svensmark, Enghoff, Shaviv, and Svensmark, Nature Comm. 8:2199, a) 2.0 Diameter [nm] Diameter [nm] Time [Hours] b) Profile 2 Profile 1Profile 1 Profile Time [Hours]

28 After 3100 Hours of measurements we get: Growth rate [%] T [min] v 9 v 5 v 6 v 8 v 10 v 11 q = 45 ion-pairs cm -3 s -1 q = 186 ion-pairs cm -3 s -1 v 4 v 7 v 3 v 1 v (dr/dt) ion [%] H 2 SO 4 [molecules/cm 3 ] Theory and experiments are consistent! Svensmark, Enghoff, Shaviv, and Svensmark, Nature Comm. 8:2199, 2017

29 Even the details in the theory fits the experiment a) b) c) ΔT [min] 4 2 ΔT [min] 2 0 ΔT [min] d [nm] d [nm] d [nm] Svensmark, Enghoff, Shaviv, and Svensmark, Nature Comm. 8:2199, 2017

30 Jasmin Tröstl et al. doi: /nature18271 WHY IT IS IMPORTANT IN THE ATMOSPHERE Growth rates of aerosols are small => low H2SO4 concentrations H2SO4 ~ 10 6 molecules/cm 3 nm/hour

31 Svensmark, Enghoff, Shaviv, and Svensmark, Nature Comm. 8:2199, 2017 [H 2 SO 4 ] ~ 10 6 molecules/cm 3

32 Consequences Experimental growth of aerosols to large sizes under the influence of cosmic rays 1. Consistent with Forbush decreases (days to weeks) 2. Consistent with Solar cycle impact on energy changes in the oceans ~ 1.5 W/m 2 (11 years cycle) 3. Consistent with climate changes over the Holocene (10 4 years) 4. Consistent with climate change over geological times 5-10 o C ( years)

33 Cosmic ray, aerosol, cloud link

34 Conclusion Cosmic rays, high-energy particles raining down from exploded stars, knock electrons out of air molecules. This produces ions, that is, positive and negative molecules in the atmosphere. The ions help the formation clusters of mainly sulphuric acid and water molecules to form and become stable against evaporation. This process is called nucleation and results in small clusters (aerosols). These small aerosols need to grow nearly a million times in mass in order to have an effect on clouds. The second role of ions is that they accelerate the growth of small aerosols into cloud condensation nuclei seeds on which liquid water droplets form to make clouds. The more ions the more aerosols become cloud condensation nuclei. IMPLICATIONS When the Sun is lazy, magnetically speaking, there are more cosmic rays and more low clouds, and the world is cooler. When the Sun is active fewer cosmic rays reach the Earth and, with fewer low clouds, the world warms up. The Sun became unusually active during the 20th Century and as a result part of the global warming observed. Cooling s and warmings of around 2 o C have occurred repeatedly over the past 10,000 years, as the Sun s activity and the cosmic ray influx have varied. Over many millions of years, much larger variations of up to 10 o C occur as the Sun and Earth, travelling through the Galaxy, visit regions with more or fewer exploding stars.

35 Summery of Mechanism Cosmic ray ionization Nucleation Growth Droplet formation Cloud

36 TESTING THE GROWTH OF AEROSOLS EXPERIMENTALY Addition of neutral aerosols CCN More particles compeating for the same gas, therefore slower growth and larger losses, as also seen in model results. Svensmark, Enghoff, Pepke Pedersen, 2012

37 Addition of aerosols using ionization CCN Contradicts the model results Svensmark, Enghoff, Pepke Pedersen, 2012

38 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, (2001)

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

40 Carbon 13 and super nova activity SN(t)/SN(0) δ 13 C [per mill] Time [Myr] Svensmark, Mon. Not. R. Astron. Soc., 423, (2012)

41 Even the details in the theory fits the experiment a) b) c) ΔT [min] 4 2 ΔT [min] 2 0 ΔT [min] d [nm] d [nm] d [nm]

42 Cosmic rays and climate over the last 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 the last years Adapted from Kirkby 42

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44 Supernova Remnant Atmospheric Relevance HADLEY CIRCULATION n H2So4 ~ cm -3 Time of growth 5-7 days GCR Solar Wind Sun Solar Wind GCR ITCZ Equator 40 South 40 North OCEAN

45 C o m p o n e n t ) P r i n c i p a l ( F i r s t C l o u d s Days ( % ) C o s m i c R a y s Aerosol and cloud response to changes in ionization