The Sun - Driving Force for Climate

1. The Sun - Driving Force for Climate Physical Climate Systems Climate Change Atmospheric Physics/Dynamics Sun Ocean Dynamics Terrestrial Energy/Moisture Human Activities External Forcing Stratospheric Chemistry/Dynamics Human Forcing Soil CO2 Global Moisture Land Use Marine/ Biogeochemistry Terrestrial Ecosystems Volcanoes Tropospheric Chemistry CO2 Pollu- tants Biogeochemical Systems

2. The Sun - Driving Force for Climate Solar Radiation and Its Variability The Sun Solar Radiation Source Solar System Solar Radiation Variability Solar Output Variations Planet-to-Planet Variations Latitudinal Variations Seasonal Variations Long-Term Variations Milankovitch Cycles Science Concepts Nuclear Fusion Process Einstein’s E = m c2 Law Sun Spots 1/R2 Law Intensity Angle of Incidence Spherical Shape of Earth Axis of Rotation Orbital Plane Eccentricity Precession Obliquity The Earth System (Kump, Kastin & Crane) • Chap. 1 (pp. 14-15) • Chap. 4 (pp. 58-59; 66-68) • Chap. 15 (p. 303-306) • Chap. 14 (pp. 274-278)

3. The Sun - Driving Force for Climate The Sun • Introduction Science quotes of 5th and 6th graders - Most books now say our Sun is a star. But it still knows how to change back into a Sun in the daytime.

4. The Sun - Driving Force for Climate The Sun (Con’t) • Medium size star - Diameter = 1.39 x 10 6 km (109 times the diameter of Earth) - Mass = 2.0 x 10 30 kg (3.3 x 10 5 times the mass of Earth) • Rotation period = average ~27 days - Variable rotation; Equatorial regions (~25 days) faster than polar regions (~35 days) Extreme uv (30.4 nm) Image

5. The Sun - Driving Force for Climate http://sohowww.nascom.nasa.gov/ The Sun (Con’t) • Average temperature star - Interior temperature 15 x 10 6 K - Exterior skin temperature 6000 K • Interior pressure = 100 x 10 9 times the surface pressure of the Earth Coronal Mass Ejection over 8-h period 5-6 August 1999 http://sohowww.nascom.nasa.gov/ 171 10-10 m emission showing the solar corona at a temperature of about 1.3 million K X-Ray Image

6. The Sun - Driving Force for Climate The Sun (Con’t) • Plot of the relative number of stars vs absolute magnitude shows that fainter stars (large magnitudes) are much more numerous than brighter stars • The Sun is more luminous than the majority of stars

7. The Sun - Driving Force for Climate Solar Radiation • Energy Source - Nuclear “fusion” of hydrogen to make helium, i.e., H2 + H2 => He4 • Energy Amount - Converts 657 x 106 tons of H2 per s (596 x 109 kg / s) - Produces 653 x 106 tons of He2 per s (592 x 109 kg / s) - Thus, about 4 x 109 kg / s of mass is converted to energy - Using Einstein's formula, E = m c2 where E is Energy; m is Mass; c is Speed of light,3 x 108 m / s. Dividing by time, t, yields P = E / t = ( m c2 ) / t where P is Power - Substituting the values for the Sun yields about P = 3.6 x 1026 watts > Note a watt equals a cal / s Science quotes of 5th and 6th graders - When they broke open molecules, they found they were only stuffed with atoms. But when they broke open atoms, they found them stuffed with explosions. This is fission.

8. Solar Radiation Variability Solar Output Variability • Sunspots appear as dark spots where temperatures in the centers drop to about 3,700 K • Sunspots typically last several days; very large ones may last for several weeks • Sunspots are magnetic regions with magnetic field strengths thousands of times stronger than the Earth's magnetic field • Sunspots usually come in groups • Not many sunspots at this time, but sometimes monthly average is over a hundred http://spaceweather.com/ 2/25/04 http://science.msfc.nasa.gov/ssl/ pad/solar/feature1.htm#Sunspots

9. Solar Radiation Variability Solar Output Variability (Con’t) • Sunspot number • Note 11 year solar or sunspot cycle • Amount of energy emitted by the Sun is related to the sunspot cycle http://earthobservatory.nasa.gov/Study/VariableSun/

10. Solar Radiation Variability Solar Output Variability (Con’t) • Variations in solar irradiance at the top of the Earth’s atmosphere over the last 120 years - Note 11-year solar or sunspot cycle - Very slight increase over this 100+ record Bulletin of American Meteorological Society, June 2003, p. 743 http://www.doc.mmu.ac.uk/aric/gccsg/2-5-3.html

11. The Solar System Percentage Mass of Components • Sun: 99.85% • Planets: 0.135% • Comets: 0.01% ? • Satellites: 0.00005% • Minor Planets: 0.0000002% ? • Meteoroids: 0.0000001% ? • Interplanetary Medium: 0.0000001% ? • Jupiter consists of more than twice the matter of all the other planets combined To be a planet, an object must meet three criteria: (1) It must have enough mass and gravity to gather itself into a ball. (2) It must orbit the sun. (3) It must reign supreme in its own orbit, having "cleared the neighborhood" of other competing bodies.

12. The Solar System Description • Sun and 8 planets and dwarf planets (Pluto and others) • Satellites of the planets, numerous comets, asteroids, meteoroids, and the interplanetary medium http://photojournal.jpl.nasa.gov/ Mercury Earth Pluto & other dwarf planets Jupiter Saturn Uranus Neptune Sun Venus Mars

13. The Solar System 10th Planet Discovered?? • 29 July 29 2005 - Astronomers discovered a new planet beyond Pluto, about 97 times farther from the Sun than Earth, i.e., 97 Astronomical Units (AU). • Scientists working to better estimate its size and its motions. They believe it is bigger than Pluto • Astronomers determine a planets size by measuring its brightness - Planets shine by reflecting sunlight - The bigger the planet, generally speaking, the more reflection • The planet's temporary name is 2003 UB313. A permanent name has been proposed to the International Astronomical Union http://science.nasa.gov/headlines/ y2005/29jul_planetx.htm?list159742

14. The Solar System 10th Planet Discovered?? (Con’t) • August 2006 - International Astronomical Union (IAU) General Assembly in Prague, stated that to be a planet an object must meet three criteria: - it must have enough mass and gravity to gather itself into a ball. - it must orbit the sun. - it must reign supreme in its own orbit, having "cleared the neighborhood" of other competing bodies. • Thus, Pluto and 2003 UB313 and several other objects circling the Sun in orbits similar to Pluto’s were defined as "dwarf planets”

15. The Solar System Planet Plus Pluto Statistical Information Dist = Distance to the Sun in AUs Radius = Radius in terms of the Earth’s Mass = Mass in terms of the Earth’s Rotate = Rotation rate in Earth days Sat = Number of associated satellites Incl = Orbital inclination in degrees Eccen = Orbital eccentricity Den = Density in g/m3 * Sun’s period of rotation at the surface varies from ~25 days at the equator to 36 days at the poles. Deep down, below the convective zone, the period of rotation appears to be 27 days.

16. Solar Radiation Variability Solar Radiation Intensity • Intensity = energy per unit time per unit area = power per unit area; power - Units > cal / s - m2 or watt / m2 ‡ watt = cal / s Solar Energy the Earth Receives • Sun’s energy is emitted in all directions • Intensity of the Sun’s energy decreases as the square of the distance from the Sun (radius of planet’s orbit) increases, i.e., referred to as the “One Over R 2 Law” I a 1 / (distance ) 2 or I a 1 / R 2

17. Solar Radiation Variability Solar Energy the Earth Receives (Con’t) • The Earth intercepts only a small portion of the Sun’s energy; about 1.62 x 10 17 watts • Solar power the Earth receives adds up to 18,000 times more energy than humankind consumes as fuel and commercial energy

18. Mercury Earth Jupiter Saturn Uranus Neptune Pluto Sun Venus Mars Solar Radiation Variability • Solar Energy the Planets Receive • Energy Received* • Name Dist (m) Radius (m) (watts) • Mercury 5.85 X 10 10 2.42 X 10 6 1.54 X 10 17 • Venus 1.08 X 10 11 6.05 X 10 6 2.83 X 10 17 • Earth 1.50 X 10 11 6.37 X 10 6 1.62 X 10 17 • Mars 2.25 X 10 11 3.38 X 10 6 2.03 X 10 16 • Jupiter 7.80 X 10 11 7.01 X 10 7 7.26 X 10 17 • Saturn 1.43 X 10 12 5.73 X 10 7 1.46 X 10 17 • Uranus 2.88 X 10 12 2.55 X 10 7 7.04 X 10 15 • Neptune 4.52 X 10 12 2.55 X 10 7 2.87 X 10 15 • Pluto 5.93 X 10 12 1.15 X 10 6 3.37 X 10 15 • Dist = Distance to the Sun • Radius = Planet’s radius • Energy Received = Energy received from the Sun • Calculations based on numbers from the class laboratory exercise. More precise numbers will yield • slightly different results.

19. Solar Radiation Variability Radiation Balance Assumption Temp with Name Temp (K) Albedo (K) Mercury 438. Venus 322. 228. (75%) Earth 274. 250. (30%) Mars 223. 215. (15%) Jupiter 120. Saturn 89. Uranus 62. Neptune 50. Pluto 44. Temp = Planet’s average temperature assuming planet is a solid globe with no atmosphere and no albedo Temp with Albedo = Planet’s average temperature assuming planet is a solid globe with no atmosphere, but with an albedo Incoming Solar Radiation Solid Planet Outgoing Radiation

20. Solar Radiation Variability Solar Angle and Intensity • Area of a flashlight beam spreads over a larger area as the flashlight moves from directly overhead to a more glancing angle • Intensity decreases as the angle between the light’s rays and the surface decreases Directly Overhead Glancing Angle Side View Overhead View

21. Solar Radiation Variability Solar Angle and Intensity (Con’t) • Global variability - Tilt of axis effect on solar intensity http://svs.gsfc.nasa.gov/vis/a000000/a000000/a000077/index.html

22. Solar Radiation Variability Axis of Rotation Solar Angle and Intensity (Con’t) • Intensity decreases as the angle between the Sun's rays and the Earth's surface decreases > Angle increases as move away from tropics Glancing Angle Directly Overhead

23. Solar Radiation Variability Axis of Rotation Solar Angle and Intensity (Con’t) • Intensity decreases as the depth of atmosphere penetrated increases Solar Rays Penetration Depth Solar Rays Penetration Depth Atmospheric Layer

24. Solar Radiation Variability Solar Angle and Intensity (Con’t) • Global variability - Spherical shape of the Earth • Local variability - Mountains > Southside for wine in NY > North side for ski slopes in NY Solar Radiation Intensity Received 400 300 Radiation Intensity ( W / m 2 ) 200 100 90N 50N 30N 10N 0 10S 30S 50S 90S Latitude

25. Solar Radiation Variability Earth’s Orbit • Note: Orbit is elliptical; it has an eccentricity 152 x 106 km 147 x 106 km

26. Solar Radiation Variability Seasons • Caused by the tilt of the Earth's axis with respect to the plane of the Earth's orbit - Changes both the angle between the Sun's rays and the Earth's surface and the depth of atmospheric penetration - Changes the length of daylight - Example: December solstice (Northern Hemisphere Winter solstice) Factoids - A planet’s rotation and tilt are result of collisions. Uranus axis is tilted 90°. Venus rotates east to west instead of west to east like the Earth.

27. Solar Radiation Variability Seasons (Con’t) • Earth’s annual trip around the Sun http://svs.gsfc.nasa.gov/vis/a000000/a000000/a000077/index.html

28. Solar Radiation Variability Seasons (Con’t) • Satellite view looking down on the North Pole

29. Solar Radiation Variability Seasons (Con’t) • Satellite view looking up at the South Pole

30. Solar Radiation Variability Universal Time d h d h m d h m 2006 Perihelion Jan 4 15 Equinoxes Mar 20 18 26 Sep 23 04 03 Aphelion Jul 3 23 Solstices Jun 21 12 26 Dec 22 00 22 2007 Perihelion Jan 3 20 Equinoxes Mar 21 00 07 Sep 23 09 51 Aphelion Jul 7 00 Solstices Jun 21 18 06 Dec 22 06 08 2008 Perihelion Jan 3 00 Equinoxes Mar 20 5 48 Sep 22 15 44 Aphelion Jul 4 08 Solstices Jun 20 23 59 Dec 21 12 04 2009 Perihelion Jan 4 15 Equinoxes Mar 20 11 44 Sep 22 21 18 Aphelion Jul 4 02 Solstices Jun 21 5 45 Dec 21 17 47 2010 Perihelion Jan 3 00 Equinoxes Mar 20 17 32 Sep 23 03 09 Aphelion Jul 6 11 Solstices Jun 21 11 28 Dec 21 23 38 2011 Perihelion Jan 3 19 Equinoxes Mar 20 23 21 Sep 23 09 04 Aphelion Jul 4 15 Solstices Jun 21 17 16 Dec 22 05 30 http://aa.usno.navy.mil/data/docs/EarthSeasons.html

31. Solar Radiation Variability Seasons (Con’t) • View of Earth from the Sun throughout the year • North and South poles are denoted by June Solstice June 21-22 Sun Vertical at Latitude 23.5°N September Equinox September 21-22 Sun Vertical at Latitude 0° December Solstice December 21-22 Sun Vertical at Latitude 23.5°S March Equinox March 21-22 Sun Vertical at Latitude 0°

32. Solar Radiation Variability Seasons (Con’t) • Earth year animation from the Sun’s point of view

33. Global Radiation Budget Variations Seasons (Con’t) Summer - 6/21 23:00 UTC From 0° Winter - 12/21 23:00 UTC http://www.fourmilab.ch/cgi-bin/Earth Sun’s Rays Circle of illumination

34. Global Radiation Budget Variations Seasons (Con’t) Summer - 6/21 23:00 UTC From 45°S Winter - 12/21 23:00 UTC http://www.fourmilab.ch/cgi-bin/Earth Arctic Circle

35. Solar Radiation Variability Special Latitudes • Based on the Sun’s angle with the Earth’s surface

36. Solar Radiation Variability Seasons (Con’t) • Antarctic Daylight

37. Solar Radiation Variability Solstice Shadows at Local Noon June 21, '02 Dec. 22, '02 Shaq's (7’ 1”) Shadow Where Length of shadow Length of shadow Max - Min (ft, in) Your height Your height North Pole (90°N) 2.3 no shadow 16' 4" Los Angeles (34°N) 0.19 1.6 1' 4” - 11' 4 Huntsville (34°N) 0.19 1.6 1' 4” - 11' 4 New York (41°N) 0.31 2.1 2' 2” - 14' 11" Buenos Aires (34°S) 1.6 0.19 1' 4” - 11' 4" Johannesburg (26°S) 1.2 0.05 0' 4” - 8' 5” South Pole (90°S) no shadow 2.3 16' 4" The ratio of your height and the length of your shadow at local noon on Jun 21st and Dec 22nd. To calculate how long your shadow would be on the first day of summer in N.Y., multiply your height by 0.31 -- the ratio listed for N.Y. on Jun 21. Length of shadow = Your height * tan (90° - Sun elevation @ local noon) Sun elevation @ local noon = 90° - (Location’s latitude ± 23.5°) where you use - if Sun is in your hemisphere and + if sun in alternate hemisphere

38. Global Radiation Budget Variations Seasons (Con’t) Solar Parameters for: Huntsville, AL Philadelphia, PA (Latitude: 34.4°N)(Latitude: 40.0°N) • June Solstice (Northern Hemisphere Summer) - Maximum solar altitude angle: 79.1° 73.5° - Longest day: 14.5 hours 15 hours - Shortest night: 9.5 hours 9 hours • September Equinox (Northern Hemisphere Fall) - Solar altitude angle: 55.6° 50.0° - Day: 12 hours 12 hours - Night: 12 hours 12 hours • December Solstice (Northern Hemisphere Winter) - Minimum solar altitude angle: 32.1° 26.5° - Shortest day: 9.5 hours 9 hours - Longest night: 14.5 hours 15 hours • March Equinox (Northern Hemisphere Spring) - Solar altitude angle: 55.6° 50.0° - Day: 12 hours 12 hours - Night: 12 hours 12 hours

39. Global Radiation Budget Variations Seasons (Con’t) All's Right With The World
 by Robert Browning (1812 - 1889) The years at the spring The day's at the morn Morning's at seven The hill-side's dew-pearled The lark's on the wing The snail's on the throne God's in his heaven... All's right with the world! Great poem but does the science seem correct?

40. Solar Radiation Variability Science quotes of 5th and 6th graders - South America has cold summers and hot winters, but somehow they still manage. Seasons (Con’t) • Insolation - Incoming solar radiation - Solar energy per unit area at the Earth’s surface • Same as solar energy intensity • Annual variation • Note: Southern Hemisphere receives more radiation during its summer (January) than does the Northern Hemisphere during its summer (July) - Remember Earth is closer to the Sun in July than January

41. Milankovitch Cycles Earth’s Orbit • Orbit changes with time in three ways Eccentricity • Defined as e = (a2 - b2)1/2 / a where a is the semi-major axis and b is the semi-minor axis • Currently e = 0.0167 Milankovitch (Serbian astronomer) 1943 http://www.ngdc.noaa.gov/paleo/slides/images/base/iceage11.gif http://earthobservatory.nasa.gov/ Library/Giants/Milankovitch/ milankovitch.html b a Sun Earth http://earthobservatory.nasa.gov/Library/ Giants/Milankovitch/milankovitch_2.html

42. Milankovitch Cycles Eccentricity (Con’t) • Jupiter’s gravitational force results in Earth’s orbit varying from nearly circular with eccentricity near 0.0 to about 0.06 • Current difference in distance to the Sun at perihelion and aphelion is 3-4% • Period - Dominate period of 413,000 and minor period of 100,000 years http://www.museum.state.il.us/exhibits/ ice_ages/eccentricity_graph.html 413,000 years 100,000 years Eccentricity of the Earth's orbit over the last 750,000 years Blue line traces the eccentricity of the elliptical orbit as it varies from circular (0.0); red line shows today's value for comparison. Berger and Loutre (1991)

43. Milankovitch Cycles Obliquity • Change in the tilt of the Earth's axis • Period — 41,000 years • Changes between ~22.1° and ~24.5° - Moon helps stabilize the obliquity; without the Moon this variation in the tilt could range much larger. The obliquity angle could reach 85° • Less tilt implies - More snow at poles because more moisture - Cooler summers, thus less snow melt - Therefore, good conditions for initiation of glaciers Current tilt of axis is 23.5° but tilt varies from 22.1° to 24.5° 23.5° Orbital Plane Sun http://earthobservatory.nasa.gov/Library/Giants/Milankovitch/milankovitch_2.html

44. Milankovitch Cycles Obliquity • Variation in the tilt of the Earth's axis over the last 750,000 years Blue line traces the tilt in degrees; red line shows today's value for comparison Berger and Loutre (1991) http://www.museum.state.il.us/exhibits/ice_ages/tilt_graph.html

45. Milankovitch Cycles Obliquity (Con’t) • Change in Ice for past 21,000 years (1/2 period) • Matches change in obliquity from 22.1° to 23.5° http://geochange.er.usgs.gov/pub/sea_level/Core/raw/quaternary/ images/gif/ice_age.gif

46. Milankovitch Cycles Precession • Wobble in the tilt of the Earth's axis • Period — 22,000 years • Like spinning top • Changes hemispheric climate not whole Earth Planetary axes would not precess or change obliquity if the planets were perfect spheres. However planetary rotation causes the equators to bulge. This gives a “handle” that the gravity of the other planets “grabs onto”, and twists the planetary spin. This causes precession and obliquity changes. http://earthobservatory.nasa.gov/Library/Giants/ Milankovitch/milankovitch_2.html

47. Milankovitch Cycles Precession (Con’t) • Precession of the equinox over the last 750,000 years Blue line traces the precession; red line shows today's value Berger and Loutre (1991) http://www.museum.state.il.us/exhibits/ice_ages/precession_graph.html

48. Milankovitch Cycles Precession (Con’t) • Current • 11,000 years from now September December June Sun March September December June Sun March

49. Milankovitch Cycles Precession (Con’t) • Stars that Earth’s axis of rotation point as the axis precesses • Note this means the pole star changes with time • Currently Earth’s axis points toward “Polaris” Past, Present & Future Pole Stars Year Constellation Closest Star c. 3,000BC Draco Thuban c. 1,000BC Usra Minor Kochab Present Usra Minor Polaris c. 4,000AD Cassiopeia Alrai c. 7,500AD Cepheus Aldera min c. 14,000AD Lyra Vega http://inkido.indiana.edu/a100/celestialsphere2.html

50. Milankovitch Cycles http://www.ukexpert.co.uk/photopost/ data/588/7the-pyramids.jpg Precession (Con’t) • Dating the Pyramids - Egyptian pyramids at Giza were built roughly 4,500 years ago. How do we know? > By determining how long each individual Pharaoh held power, adding all the years and working backwards ‡ Not very accurate > Carbon dating ‡ Provides dates for the pyramids plus or minus 100 years > Astronomical dating The Ancient Egyptians aligned the sides of their pyramids to the points of the compass, with extraordinary accuracy. The most accurate is the Pyramid of Khufu, called the Great Pyramid. The east and west sides miss True North by less than three minutes of arc (roughly one tenth the diameter of the full moon). It took over 4,000 years before the astronomer, Tycho Brahe, was able to take astronomical measurements to a greater accuracy.