Family Homecoming Special Event "Can Climate Engineering Serve as a Complementary Step to Aggressive Mitigation?"

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Family Homecoming Special Event"Can Climate
Engineering Serve as a Complementary Step to
Aggressive Mitigation?"

• Dr. Michael MacCracken, The Climate Institute,
  Washington, DC
• Friday, Sept. 25 at 400 pm in Olin 1, with
  cookies

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Hydrologic Cycle
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Annual Precipitation, Washington State
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The Atmospheres Energy

• Read Anthes chapter 3

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Energy is the ability to do work

• Units are mass x distance2 / time2
• Potential energy E mgh
• Kinetic energy E 1/2 mv2
• Heat energy sensible and latent
• Radiant energy visible and infrared

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Laws of Thermodynamics

• 1. Conservation of energy Energy is neither
  created nor destroyed it is transformed.
• you can't take out of a system more than you put
  in.
• you can't win
• 2. The entropy of the universe is continually
  increasing.
• perpetual motion and a heat engine with 100
  efficiency are both impossible.
• you can't break even
• 3. It is impossible to attain absolute zero or
  absolute 0 entropy.
• you can't even get out of the game

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Energy transformation exampleHydroelectric
power plant
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More complete picture
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• Solar power (drives hydrologic cycle)
• Potential energy (water stored in reservoir)
• Kinetic energy (spillway)
• Mechanical energy (spinning turbines)
• Electrical energy (transmitted over wires)
• Lightbulbs (converts energy to light)
• Waste heat (IR) is lost to space

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Transfer of Energy

• Conduction -- Molecular motion
• Convection -- Mass transfer vertical
• Advection -- Mass transfer horizontal
• Latent heat -- Ice and liquid phases
• Radiation -- SW and LW photons

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Conduction (molecular motion)

• Thermal conductivity is the ability of a
  substance to transfer heat via molecular motion.
• Measured in units of cal/sec/cm/oC
• Conductivity of solids gt liquids gt gases.
• Silver (good conductor) 1.0
• Water (1000 times worse) 1.4 x 10-3
• Ice 5.3 x 10-3
• Air (good insulator) 6.1 x 10-5

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Convection and Advection (mass transfer)

• Rising air currents (thermals) carry sensible
  heat and latent heat from the surface into the
  upper air.
• Winds (advection) carry sensible heat and latent
  heat (moisture) into northern latitudes.
• Ocean currents transfer warmer waters to northern
  latitudes and vice-versa.

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The Electromagnetic Radiation

• Every object in the universe emits radiation.
• From 1012 cm radio waves to 10-12 cm gamma rays

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Stefan-Boltzmann Law

• Hotter bodies emit more total energy than colder
  bodies.
• The total energy of a blackbody is proportional
  to the fourth power of temperature.
• Etot ?T4

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• Compare energy emitted by Sun? and Earth?
• Energy emitted per unit of surface area
• E? / E? ?T4? / ?T4? (6000 / 300)4 204 1.6
  x 105
• Energy emitted by the entire surface
• Multiply by R2?/ R2? (100/1)2 104
• So Sun emits 1.6 x 109 more energy than Earth

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Power in watts

• Sun 3.6 1026
• Total human consumption, global 1.3 1013
• Total human consumption, US 3.2 1012
• Large commercial power plant 109 to 1010
• human, daily average from diet 100 (one light
  bulb)
• per capita world 2 x 103 (20 lightbulbs)
• per capita US 104 (100 lightbulbs)

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Planck energy distribution curve (energy
density per unit time per unit wavelength)
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Weins Law

• The wavelength of maximum emission depends
  inversely on a bodys Kelvin temperature.
• ?max 2897/T (microns)
• Emission from hotter bodies peaks at shorter
  wavelengths.
• What is ?max for the Sun?
• ?max? C/T 2897/ 6000 0.48 microns yellow
  visible light
• What is ?max for the Earth?
• ?max? C/T 2897/ 300 10,1 microns infrared

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Trace gases absorb radiation at selected
wavelenghts.Atmosphere is transparent to
sunlight at 0.5mm and to IR at 10mm
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Net result
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Make a heat budget at the top and bottom of the
atmosphere
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\

• Top of atmosphere Gains Losses 100 SW -
  31.3 SW - 68.7 LW 0

Surface 7.6 SW 43.2 SW 98 LW - 7.6 SW - 4.4
C - 22.8 E - 114 LW 0 This is the average
balance sheet -- Dynamic balance is never
achieved!