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Cosmic rays and climate   jasper kirkby -cern - 4-6-2009
 

Cosmic rays and climate jasper kirkby -cern - 4-6-2009

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    Cosmic rays and climate   jasper kirkby -cern - 4-6-2009 Cosmic rays and climate jasper kirkby -cern - 4-6-2009 Presentation Transcript

    • Cosmic rays and climate Jasper Kirkby /CERN CERN Colloquium, 4 June 2009 1
    • 1. Present climate change 2
    • Climate forcings (IPCC 2007) Global Land-Ocean Temperature Index .6 GISS Annual Mean .4Temperature Anomaly (°C) 5-year Mean .2 .0 -.2 -.4 1880 1900 1920 1940 1960 1980 2000 • 0.7oC rise since 1900 (not uniform) • IPCC findings: ‣ Total anthropogenic 1.6 W/m2 (≅ 1 candle per 25 m2) ‣ Negligible natural (solar) contribution: 0.12 W/m2 ‣ Clouds poorly understood 3
    • Why clouds are important for climate change John Constable, Cloud study, 1821 • Clouds cover ~65% of globe, annual average • Net cooling of 30 W/m2 • c.f. 1.6 W/m2 total anthropogenic 4
    • NASA CERES satellite• Data from CERES satellite (Clouds and Earth’s Radiant Energy System)• Clouds (and oceans) are poorly simulated in climate models (finest grid sizes ~100 km x 100 km) 5
    • II. Evidence for pre-industrial solar-climate variability• Numerous palaeoclimatic reconstructions suggest that solar/GCR variability has an important influence on climate• However, there is no established physical mechanism, and so solar-climate variability is: ‣ Controversial subject ‣ Not included in current climate models 6
    • Little Ice Age and the sunspot record The frozen Thames, 1677 200 200Sunspot number Little Ice Age Dalton Minimum 100 100 Maunder Minimum 0 0 1600 1650 1700 1750 1800 1850 1900 1950 2000 Year • Inactive sun (low sunspot peak, long cycle length) cold climate • Active sun (high sunspot peak, short cycle length) 7 warm climate
    • 1000 1200 1400 1600 1800 2000 Global climate - last 2000yr Greenland surface temperature (oC) a) Northern hemisphere temperature 0.4 Medieval Warm Little Ice Age Temperature anomaly ( C) o instrumental • -32 GRIP -31 -20.6 Dye 3 -19 Little Ice Age and 0 hockey stick -0.4 multi-proxy Medieval Warm Period • (tree rings, pollen, shells, stalagmites, etc.) Greenland boreholes (rhs) Global observations -0.8 worldwide boreholes b) Galactic cosmic rays 10Be (Greenland) high GCR flux cool climate GCR change (% from 1950 value) -10 14C (rh scale) (arb. scale) -20 Carbon-14 anomaly (x 10-3) low GCR flux warm climate 0 10 increasing GCR 0 20 Austrian speleothem: 30 10Be (South Pole) 320 20 CO2 (lh scale) CO2 (ppm) 40 290 c) Tropical Andes glaciers -10 -8.0 0 GCRLake Mucubaji magneticsusceptibility (SI x10-6) !18O GCR/ 0 (‰) -7.5 "14C glacial advance 3 (‰) 10 1oC !18O 6 -7.0 Mangini et al., EPSL 235 (2005) 20 500 1000 1500 2000 Year (AD) 1000 1200 1400 1600 1800 2000 Year (AD) 8
    • Siberian climate - last 700 yr• Correlation recently reported between solar/GCR variability and temperature in Siberia from glacial ice core• 30 yr lag (ie. ocean currents may be part of response) Eichler et al. GRL 36 (2009) Siberia temperature (oC) solar/GCR (rhs): 10Be 2 14C 4 Solar modulation 1 temperature (lhs) 2 (! units) 0 0 -1 -2 1300 1400 1500 1600 1700 1800 1900 2000 Year 9
    • N. Atlantic ice rafted debris - last 10 kyr (Holocene) Bond et al, Science 294, 2001 Cosmic rays: Ice-rafted debris (%): Low cosmic -0.4 GCR -4 Less ray flux (10Be) ice 0.0 0 ice-rafted debris 0.4 4 High cosmic More ray flux ice Little Ice Age Low cosmic -0.1 Medieval Warm -4 Less ray flux ice 0.0 0haemetite-stained grains quartz grains 0.12 mm 0.1 GCR 4 High cosmic More ice-rafted debris (14C) ray flux ice 12 10 8 6 4 2 0 Calendar age (kyr BP) Icelandic glass grains foraminifera • LIA is merely the most recent of 10 around 10 such events in Holocene
    • GCR influence on ITCZ/monsoon in Little Ice Age? high GCR flux southerly ITCZ shift low GCR flux northerly ITCZ shift Drier in LIA Wetter in LIA ITCZ displacement D11 during LIA D7 July ITCZ D5 D8 D10 D13 D12 D6 D9 W0 Equator W2 January ITCZ W4 W3 W1 11
    • Indian Ocean monsoon - 6.5-9.5 kyr ago U. Neff et al. (Nature 411, 2001)high a 14C (GCR intensity) dry 510 ± 30 1400 ± 30GCR 10 3010 ± 60 3740 ± 130 –3.5 3790 ± 140 5 4380 ± 260 IT C Z O (‰ VPDB) –4.0 4370 ± 100 0 C (‰) 4900 ± 140 –5 –4.5 5750 ± 100 Jun-Aug 14 6540 ± 180 monsoons 18 –10 –5.0 6960 ± 50 7910 ± 210 8880 ± 90 8870 ± 230 –15 –5.5low 9760 ± 150 10 cm 18 O (rainfall) 10,060 ± 210GCR wet High pres s ure 10,470 ± 170 6.500 7.000 7.500 8.000 8.500 9.000 9.500 Age (kyr BP)high 10 dry b 14C (GCR intensity)GCR 5 • Solar/GCR forcing of Indian –4.0 0 –5 –4.5 O (‰ VPDB) Ocean monsoons (ITCZ C (‰) –10 migration) on centennial—even 14 –5.0 decadel—timescales 18 –15 –20 18 O (rainfall)low –5.5GCR wet 7.900 8.000 8.100 8.200 8.300 Age (kyr BP) 12
    • Solar-climate mechanisms• Candidates for Global mean temperature (0C) 0.15 solar-climate variability: 0.10 solar irradiance estimated forcing Lean et al. (1995) (MAGICC GCM) ‣ direct effect: 0.05 ✦ total solar irradiance 0 -0.05 Lean et al. (2002) ✦ solar UV -0.10 ‣ indirect effect: 1600 1650 1700 1750 1800 1850 1900 1950 2000 Year ✦ galactic cosmic rays (GCRs) /ionising particles• Can be resolved in principle since GCRs are, in addition to 11-year solar cycle, modulated by: ‣ solar magnetic disturbances (esp. high latitude effects) ‣ geomagnetic field (low latitude effects) ‣ galactic environment 13
    • Asian monsoon and geomagnetic field East Asian monsoon instensity; Wang et al., Nature 451, 2008 440 Monsoon intensity –12 N. Hemisphere summer 2! U-Th dating errors 18 O (‰, VPDB) insolation (W m-2) –11 420 –10 400 –9 380 –8 –7 360 Sanbao/Hulu caves, China 0 20 40 60 80 100 120 140 160 180 200 220 Age (kyr BP) Knudsen & Riisager, GSA 2009 Geomagnetic dipole moment (1021Am2) 0.4 monsoon intensity –7.0 120 residuals for last 5000yr 20 geomagnetic field Asian monsoon Summer insolation, 30N (W m-2) dipole moment (1021Am2) 460 0.2 (± 2! band) (‰ VPDB) –7.4 10 10018 O (‰ VPDB) 0.0 –7.8 470 0 summer 80 monsoon intensity 18O –8.2 insolation –0.2 geomagnetic field 480 –10 Asian monsoon –8.6 60 –0.4 (Dongge Cave, China) –20 490 r (0–5000 BP) = 0.86 r (0–5000 BP) = 0.71 –9.0 40 –0.6 –30 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 0 1000 2000 3000 4000 5000 Age (yr B.P.) Age (yr B.P.) • Asian monsoon controlled by orbital insolation - with strong millennial-scale variability • Possible influence of geomagnetic field on Asian monsoon? • Opposite sign of effect: lower B field → increased GCR → increased monsoon intensity, which could result from latitudinal differences of solar- and geomagnetic modulations 14
    • Galactic modulation of climate? - 500 Myr CO2 GCR icehouse greenhouse Shaviv & Veizer, GSA Today, 2003• Orbital period of Sun/Earth around Milky Way ~550Myr• High GCR flux in spiral arms => 140 Myr period• Same period and phase found in benthic sea temperature (4oC amplitude) and ice age epochs (icehouse/greenhouse) 15
    • III. Solar variability in the 20th century 16
    • Sun (photosphere) seen in visible (677nm) at solar max (2001) NASA/ESA SOHO 17
    • Sun (corona) seen with extreme UV eyes (20nm) NASA/ESA SOHO 18
    • Cosmic ray changes during 20th century 0 galactic cosmic solar magnetic flux Lebedev balloon GCR data: Solar magnetic flux (x1014 Wb) rays 3.5 5 a) Murmansk 1.6 1010Be concentration (x104 g-1) 3.0 Cosmic ray intensity (cm-2s-1) Mirny 1.2 15 0.8 2.5 Moscow 0.4 10Be (GCR) weaker solar 2.0 modulation at low latitudes, 0 due to geomagnetic shielding 1700 1750 1800 1850 1900 1950 2000 Year Alma-Ata • 1.5 Solar open magnetic flux increased by x2.3 in 20th century • b) GCR net decrease by ~20% 200 Sunpot number (mostly in 1st half of century) 100 • Largely only solar cycle variations 0 cycle 19 cycle 20 cycle 21 cycle 22 cycle 23 of GCR flux in 2nd half 1960 1970 1980 1990 2000 Year 19
    • Sea-level change in 20th century Year 1920 1940 1960 1980 2000 8 sea-level rate: 9 stations sunspot number Holgate, GRL (2007) 177 stations <TOPEX 150 6 satellite> Rate of sea level change (mm/yr) 200Cumulative sea level change (mm) Sunspot number (smoothed) 4 150 100 2 100 50 50 0 0 0 -2 1900 1920 1940 1960 1980 2000 Year -4 1920 1940 1960 1980 2000 Year (decade mid-point) • Steady rise of sea-level; mean rate = 1.7 mm/yr • No increase in rate during recent decades • Thermal expansion of oceans (mainly) + land ice melting • Rate of sea-level rise is strongly modulated solar modulation? (but solar irradiance variation is too small) 20
    • Sea-level positive feedback 21
    • Recent global temperatures - last 30 yr 1.0 1.0 surface temperatures; thermometers 0.8 (Hadley and GISS) 0.8Temperature anomaly (oC) 0.6 0.6 0.4 0.4 0.2 0.2 0 0 -0.2 -0.2 tropospheric temperatures; -0.4 satellite microwaves (UAH) -0.4 -0.6 -0.6 1980 1985 1990 1995 2000 2005 Year • Most of ~2 yr fluctuations due to El Niño-Southern Oscillation (eg 1997-98) + volcanoes (El Chichon 1982, Pinatubo 1991) • Satellite and radiosonde (tropospheric) data show ‣ less warming than thermometer measurements of surface ‣ no enhanced upper tropospheric warming, expected from GHG • Mean global temperatures flat over last 8 years. Cause not known but CO2 increasing, so must be natural forcing 22
    • Pacific Decadel Oscillation• PDO (Hare 1996) is similar to ENSO (temperature anomalies and surface winds), except for long (30 yr) periodicity and primary effect on Pacific NW• PDO transitions coincide with gradient changes of global temperatures• PDO may be shifting to negative phase 23
    • Sunspot weakening Livingston and Penn, National Solar Observatory, Tucson, AZ "Sunspots may vanish by 2015", submitted 2005 (rejected for publication) Livingston and Penn, 2005 example measurements:Sunspot magnetic field (G) 3000 0.0 Normalised central depth Fe 1564.8 magnetic spliting 0.1 CN 2500 OH 0.2 2015 Fe I 1564.8 0.3 2000 Jan 2002 0.4 Jun 1991 OH minimum B field for visible sunspots 0.5 1500 OH 1565.3 2000 2005 2010 2015 0.6 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Year ! Wavelength (+1564 nm) 1.0 (Sunspot / photospheric) intensity Sunspot contrast ‣ Temperature-sensitive molecular lines (1.0 = invisible) 0.9 ‣ Zeeman splitting of Fe I line 0.8 2014 ‣ Continuum brightness of sunspot umbrae • Sunspot umbrae warming at 45K /yr 0.7 • Sunspot magnetic fields decreasing at 77 G/yr 0.6 • Independent of sunspot cycle 2000 2005 2010 2015 • Linear extrapolation sunspots vanish after Year 2015 (like Maunder Minimum) 24
    • Current very low solar activity • Galactic cosmic rays (Oulu neutron monitor) Counting rate change (%) 10 Currently one sunspot on 0 Sun, and GCRs high • Next sunspot cycle 24 is -10 very late -20 • Mean sunspot cycle length 1980 1990 2000 2010 is 11.1 yr Year • Length of cycle 23 is now Total solar irradiance (World Radiation Center, Davos) >13.1 yrSolar Irradiance (Wm!2) 1368 cycle 21 cycle 22 cycle 23 0.1% • Last time such a long cycle occurred was cycle 4 1366 (1784-1798) just before the Dalton minimum - 1364 coincided with notable 1975 1980 1985 1990 1995 2000 2005 2010 cold period of few decades Year • We live in interesting 200 200 times for the Sun... Sunspot number Little Ice Age Dalton Minimum 100 Maunder Minimum 100 (hopefully a blessing not a 0 0 curse) 1600 1650 1700 1750 1800 1850 1900 1950 2000 Year 25
    • IV. Physical mechanism• GCRs/ionising radiation may affect cloud amount via: ‣ CCN number concentration, and/or ‣ ice particle formation in clouds 26
    • Radiative forcing from aerosols cloud dropletaerosol (CCN) scattering and unperturbed cloud 1. increased cloud 2. increased cloud lifetime absorption of albedo (drizzle suppression) solar radiation “direct effect” “indirect effect” (more cloud droplets) cloud droplet (~10-20 m)• All cloud droplets form on aerosol “seeds” known as cloud condensation nuclei - CCN• Cloud properties are sensitive to number of droplets• More aerosols/CCN => brighter clouds, with longer lifetimes cloud condensation nucleus (CCN) (~100 nm) 27
    • Seeds for cloud formation contrails ship tracks off N.America• Aerosol particles = condensation seeds• Charged particles = condensation seeds (at very high supersaturations) + - + - + - + - - +• Can cosmic rays, under natural conditions, influence aerosols, clouds and climate? bubble chamber 28
    • Possible mechanism • Important source of cloud condensation nuclei is gas-to-particle tion critical cluster ! Gibbs free energy ora spo conversion: p neutral nucleation a ev barrier nta cluster trace gas → CN → CCN neo 0 us spo • n gro tan Ion-induced nucleation pathway is eou sg wth row th energetically favoured but limited by charged cluster the ion production rate and ion lifetime 0 5 10 No. H2SO4 molecules 0.3 nm 1 nm 100 nm > 10 µm galactic cluster critical cosmic ion cluster H 2O H 2O H 2O rays H2SO4 HSO4¯ H2SO4 - H2SO4 - H2SO4 - cloud NO3¯ cloud droplet aerosol condensation O2¯ neutral critical particle, nucleus, CCN CN H3O+ cluster cluster H 2O H 2Oion pairs H 2O H2SO4 SO42- N 2+ H3O+ 29
    • Is ion-induced nucleation globally important? F. Yu et al., ACP 2008 Ratio of ion-induced nucleation rates to all primay aerosol sources (dust, sea salt, black carbon, organic carbon) - for lowest 3km altitude .001 .01 .1 1 3 10 30 100 300 1000 10000• Modeling studies: ‣ Kazil et al. ACP 2006: “No” ‣ Pierce & Adams GRL 2009: “No” ‣ Yu et al., ACP 2008: “Yes”• All modeling studies depend on uncertain experimental parameters• Atmospheric observations over land (boreal forest) suggest ~10-20% of new particles are ion-induced (Laakso et al, 2007), but alternative model interpretation of same dataset (Yu and Turco, 2008) find much higher fraction, ~80%• Ion-induced nucleation likely to be more important over oceans and at high altitudes (lower background aerosols, trace gas concentrations and temperatures) - but few measurements exist 30
    • Aerosol production by solar cosmic rays Mironova et al, GRL 2008 •Aerosol Index (norm. variation) Solar proton event 20 Jan 2005 (GLE) highest SPE intensity sites (6 stars) • TOMS satellite measurement of optical depth/Aerosol Index (AI) • Increase of sulphate/nitrate aerosol • Further satellite/LIDAR observations have been made of increased aerosol production in atmosphere due to ionising particles 31
    • Cloud observations• Original GCR-cloud correlation made by Svensmark & Friis-Christensen, 1997• Many studies since then supporting or disputing solar/GCR - cloud correlation• Not independent - most use the same ISCCP satellite cloud dataset• No firm conclusion yet - requires more data - but, if there is an effect, it is likely to be restricted to certain regions of globe and at certain altitudes & conditions• Eg. correlation (>90% sig.) of low cloud amount and solar UV/GCR,1984-2004: Usoskin et al, GRL 2006 32
    • Global electrical circuit ionosphere (>90 km altitude) +250 kV + + + + + + + + + + + + + + + + + fair weather current fair weather ~ 2 pA m -2 field ~105 ! (fair weather + _ bipolar ion- fair weather _ _ environment value) + + + current highly charged _ _ cloud-perturbed ~1400A (J ~ 2.7 pA/m2) +_ aerosols + + + _+ field region of net - + _ + +_+ _ + + positive charge + + + + + ++ + + ++ + + + + + + + + + + + + + + + + + charge accumulation cloud layer thunderstorm (low conductivity) ~200 ! 0.7 F ___ _ _ __ _ current generators aerosol _ _ _ _ _ _ + + __ region of net - (40 flashes /s) scavenging _ + _ " = RC ~2min _ 250 m negative charge bipolar ion- environment surface 0V Electric field• Cosmic rays ionise atmosphere and control Earth-ionosphere conductivity• Large aerosol charges at cloud boundaries => unipolar space charge region• Can be entrained inside clouds and may affect: ‣ Rate of aerosol accretion by cloud droplets ‣ Ice particle formation ‣ Atmospheric dynamics• Largest ionisation in polar regions; many observations of cloud and T/P changes caused by Forbush decreases, solar disturbances, magnetic sector crossings... 33
    • V. CLOUD experiment at CERN 34
    • CLOUD collaboration CLOUD Collaboration 31 May 2009 Austria: University of Innsbruck, Institute of Ion Physics and Applied Physics University of Vienna, Institute for Experimental Physics cloud Bulgaria: Institute for Nuclear Research and Nuclear Energy, Sofia Estonia: University of Tartu, Department of Environmental Physics• 19 institutes from Europe, Finland: Helsinki Institute of Physics and University of Helsinki, Department of Physics Russia and USA Finnish Meteorological Institute, Helsinki• University of Kuopio, Department of Physics 14 atmospheric institutes Tampere University of Technology, Department of Physics + 5 space/CR/particle physics Germany:• Goethe-University of Frankfurt, Institute for Atmospheric and Environmental Sciences CLOUD-ITN network of 10 Leibniz Institute for Tropospheric Research, Leipzig Marie Curie fellows: 8 PhD Portugal: University of Lisbon, Department of Physics students + 2 postdocs Russia: Lebedev Physical Institute, Solar and Cosmic Ray Research Laboratory, Moscow Switzerland: CERN, Physics Department Fachhochschule Nordwestschweiz (FHNW), Institute of Aerosol and Sensor Technology, Brugg Paul Scherrer Institute, Laboratory of Atmospheric Chemistry United Kingdom: University of Leeds, School of Earth and Environment University of Reading, Department of Meteorology Rutherford Appleton Laboratory, Space Science Department United States: California Institute of Technology, Division of Chemistry and Chemical Engineering 35
    • Cloud observational scales observational scale 1 nm 1 µm 1 mm 1m 1 km 1000 km satellite CLOUD ground/aircraft cloud system cloud scale laboratory microphysical scalemolecule CCN raindrop cloud parcel /ion critical cloud droplet cluster /ice particle 36
    • CLOUD method P. Minginette • aerosol chamber + state-of-the-art analysing instruments in CERN PS beamline • laboratory expts. under precisely controlled conditions (T, trace gases, aerosols, ions) • study aerosol nucleation & growth; and cloud droplet & ice particle microphysics - with and without beam 37
    • CLOUD-06 liq.N2 liq.O2 air dewar dewar mixing SO2 (500 l) (500 l) station 03 generator ultrapure air system humidifier electrostatic precipitatorUV collimator +HV (0-20kV) 4kV condensation particle counter (CPC) battery scanning mobility particle sizer (SMPS) 2m aerosol chamber atmospheric ion spectrometer(AIS) sampling chemical ionisation mass probes spectrometer (CIMS;H2SO4) Gerdien condenser field cage SO2, O3 analysers HV electrode T, P, UV, H20 measurements -HV (0-20kV)UV lamparray (254nm) beam hodoscope 3.5 GeV/c !+• Beam tests of pilot CLOUD experiment at CERN PS in Oct/Nov 2006• Aims: ‣ Technical input for CLOUD design ‣ First physics measurements (H2SO4 ion-induced nucleation) 38
    • Aerosol bursts Kulmala et al: Fiedler, Arnold, Kulmala et al, ACP 2005 (Hyytiälä, Finland) H2SO4 vapour aerosol no. concentration concentration (3-6 nm diameter) 2000 /cm3 0.1 pptv H2SO4 90 min delay CLOUD-06 measurements: • Bursts of aerosol particle production growing to CCN size in few hours observed log(dN/dlog(Dp) [cm ]) AIS (-) Mobility diameter [nm] 10 3.5 3.0 2.5 throughout troposphere • 1 Associated with H2S04 2.0 AIS (+) 1.5 10 1.0 -3 production, but at very low 1 concentrations • 10000 CPC threshold Conc. [cm ] Not yet understood:-3 8000 3 nm 6000 3 nm ‣ Extra vapours (NH3,VOC)? 4000 5 nm 2000 7 nm 0 9 nm 0 2 4 6 Time [hr] 8 10 12 ‣ Ion-induced nucleation? 39
    • Beam intensity CLOUD-06 results 200 run 35 [kHz] 100 0 0 8 10 7 3 Nucleation rate, J3 [cm s ] 5 6 -1 CPC threshold [nm] 4 3Particle concentration [cm-3] -1 6000 10 -3 2 3 SO2 [ppb] 5000 -2 0.3-0.6 1 5 10 4000 1.5 7 6 -3 3000 10 2000 9 -4 10 1000 -5 0 10 -8 -4 0 4 8 0 50 100 150 200 250 Time [h] Beam intensity [kHz] • Results of pilot CLOUD run: ‣ validated the basic experimental concept of CLOUD ‣ suggestive evidence for ion-induced nucleation of H2SO4-H2O under atmospheric conditions ‣ provided important technical input for CLOUD design 40
    • CLOUD-09 design requirements• Large chamber: ‣ Diffusion lifetime of aerosols/trace gases to walls ~L2 ‣ Dilution lifetime of makeup gases ~L3 => 3m chamber has typically 5-10 hr lifetimes• Ultra-clean conditions: ‣ Condensable vapours, eg. [H2SO4] ~0.1 pptv ‣ Ultrapure air supply from cryogenic liquids ‣ UHV procedures for inner surfaces, no plastics 50 100• Temperature stability and wide T range 40 80 CPC 3010 [# cm ] -3 CPC 3025 [# cm ] 3 nm CPC 3025 30 7 nm CPC 3010 60 ‣ 0.1oC stability 20 40 ‣ Fibre-optic UV system for photochemistry -3 10 20 ‣ -90C → +100C range 0 0 Temperature [°C] 27• Field cage up to 30 kV/m: 26 ‣ Zero residual field 25 40 1.2 SO2 [ppb]• O3 [ppb] 30 0.8 Particle beam 20 40 RH [%] 0.4 10 20 0 0.0 0 ‣ Wide beam for ~uniform exposure 0 4 8 12 Time [hrs] Time [hrs] 16 20 24• Comprehensive analysers (measure “everything”, as for collider detectors...) ‣ Mass spectrometers for H2SO4, organics, aerosol composition 41
    • CLOUD-09 chamber at CERN P. Minginette 42
    • CLOUD plans• 2009: ‣ commission CLOUD-09 ‣ study H2SO4-H2O nucleation with and without beam ‣ reproducibility of nucleation events ‣ PTR-Mass Spect. to measure organics at 10 pptv level ‣ new ion-TOF Mass Spect. for ion characterisation• 2010: ‣ commission thermal system (-90C → +100C) ‣ study H2SO4/water + volatile organic compounds with and without beam ‣ temperature dependence (effect of altitude)• 2011-2013: ‣ extend studies to other trace vapours, and to cloud droplets & ice particles (adiabatic expansions in chamber) 43
    • Conclusions• Climate has continually varied in the past, and the causes are not well understood - especially on the 100 year timescale relevant for today’s climate change• Strong evidence for solar-climate variability, but no established mechanism. A cosmic ray influence on clouds is a leading candidate• CLOUD at CERN aims to study and quantify the cosmic ray- cloud mechanism in a controlled laboratory experiment• The question of whether - and to what extent - the climate is influenced by solar/cosmic ray variability remains central to our understanding of anthropogenic climate change 44