COSMOS 2013: Aerosols, Clouds, and Climate

Transcription

1 7/9/13 About Me Stanford University COSMOS 2013: Aerosols, Clouds, and Climate A.B. 1991, Interna7onal Rela7ons B.S. 1991, Chemical Engineering California Ins7tute of Technology M.S. 1995, Chemical Engineering Ph.D. 1995, Chemical Engineering Na7onal Center for Atmospheric Research Advanced Studies Postdoc Princeton University Lecturer: Lynn Russell Scripps Ins7tu7on of Oceanography University of California, San Diego Chemical Engineering Faculty Scripps Ins7tu7on of Oceanography, UCSD Climate Sciences Faculty 116 peer- reviewed publica1ons on aerosols 2003 Kenneth Whitby Award Thiele Lectureship in Chemical Engineering 2002 James S. McDonnell Founda7on 21st Century Science Research Award 2002 MIT Technology Review Magazine s Outstanding Young Innovators Award Global Warming Introduc7on to Climate and Aerosols What s in the Textbook Model? Textbook Energy Balance Energy In = Energy Out + Sources - Sinks Energy Balance (equivalent to the First Law of Thermodynamics, ca. 1850) Radia7on (the Stefan- Boltzman Equa7on, ca. 1880) Greenhouse Effect (for CO2, Tyndall 1858; also for clouds and water) White House Effect (for clouds, ca. 1950; also for aerosols) FL FS = FL FS Sun Earth How do we know this? First Law of Thermodynamics Rudolf Clausius 1850 William Thompson (Lord Kelvin) 188 1

2 7/9/13 Energy Balance Simplified Electromagne7c Spectrum Any System In 10nm=10µm +Sources - Sinks Out SW Shortwave FL = σte Earth Longwave Earth System Infrared- cause stretching and vibra7ng of molecular bonds Visible- cause low energy electronic transi7ons in atoms and molecules Ultraviolet radia7on- cause higher energy electronic transi7ons Energy In = Energy Out + Sources - Sinks 500nm=0.5µm As a 1st approxima7on, there are no con7nuous sources or sinks of energy on Earth (only temporary storage, e.g. ocean) Energy In (Shortwave) = Energy Out (Longwave) Thermal Equilibrium is the name of this assump7on Solar Constant Simplified Climate Model Incoming shortwave = Outgoing longwave Energy absorbed = Energy emiled Luminosity of the sun Irradiance at earth S0 = L0/(πd2) = 1.x103 W/m2 L0 ~ 3.9x1026 W (p. 331) Area = πd 2 FS = 0.25*S0(1- αp) FL = σte F d = m (p.37) F S Incident on projected disc πr2 L Emi,ed from sphere surface πr2 FS = F L Together these laws give us the atmosphere s Tbb With just a li,le geometry: FS = FL 0.25*S0(1- αp) = σtbb Tbb = [0.25*S0(1- αp)/σ]0.25 Tbb 255 K Sunlight shines on one side But infrared energy is emiled in all direc7ons Ra7o of area of circle- to- sphere is 0.25 FS to 1*πr2 FL from *πr2 Textbook Radiation More Infrared Radiation = Higher Temperature FL= σtsurf It s the same law that night vision goggles use! How do we know this? Stefan- Boltzmann Law Josef Stefan 187 Ludwig Boltzmann 188 Max Planck

3 7/9/13 Balance & Radiation FL FS = FL FS Sun Earth absorbing infrared energy emimng heat FS = 239 W m-2 That s too cold! What did we forget? H2O and CO2 in the atmosphere act like the glass windows FL FS = σtsurf Tsurf -18 C or 0 F Greenhouse gasses Earth s can bbe lanket: The Greenhouse Effect thought of as a How a greenhouse Carbon works Blanket Tsurf Textbook Greenhouse Effect FL F + Fghg= σtsurf Tsurf or 59 F S Tyndall measured how with CO (and H2O). CO2+ + Aerosols FS increases Fghg Tsurf How do we know this? The Greenhouse Effect of CO2 Joseph Fourier 182 John Tyndall 1858 Svante Arrhenius 1896 The Textbook Equations Greenhouse Effect FS + Fghg= σtsurf T or 59 F 2 = W Mo ar re m G er HG Pl an et surf What s in the Textbook Model? Energy Balance (equivalent to the First Law of Thermodynamics, ca. 1850) Radia7on (the Stefan- Boltzman Equa7on, ca. 1880) Greenhouse Effect (for CO2, Tyndall 1858; also for clouds and water) White House Effect (for clouds, ca. 1950; also for aerosols) 3

4 7/9/13 Atmospheric Composition What are Aerosol Particles? The atmosphere has many layers. Most of the atmosphere consists of 78% nitrogen (N 2 ) and 21% oxygen (O 2 ). Trace gases include water (0-%), which is very variable, and argon (1%). Carbon dioxide (CO 2 ) makes up only 0.0%. The other trace gases and particles constitute less than 0.1% of the mass of the atmosphere. Aerosol Spray Cans What are Aerosols? Aerosol ParVcles How long do par7cles stay in the atmosphere? Rain is big enough to fall 20 μm to 5 mm Aerosol parvcles are too small to fall one- millionth of a meter <1 μm ~100 μm Rain" Husar and Shu, 1976" Compare: Human hair" Los Angeles Smog Terpenes (C 5 H 8 ) n! Andino et al., 2000 photochemical smog +O 3! no par7cles sun! sun! par7cles atmosphere! polluted atmosphere!

5 7/9/13 Which one would you like to sit in on a hot day? White Reflects Energy We call this the white house effect Black Absorbs Energy The less black, the less absorp7on Now, imagine the Earth is a big car with different colors Clouds and Aerosols act like the white car reflect energy back to space 31 March 2005 How Aerosols Keep Planet Cool White House Effect The Textbook Model White House Effect Greenhouse Effect T bb 2 S 0 (1- α p ) + F ghg = σt surf T surf or 59 F 2 S 0 (1- α p ) + F ghg = σt surf T surf 2 or 59 F More Aerosol = Cooler Planet Now α p is about 0.31 If we increase aerosols More sunlight is reflected Less infrared is emiled Temperature decreases More Aerosol = Cooler Planet More GHG = Warmer Planet α p Global Warming and Climate What we know CO 2 traps sunlight energy like a blanket Atmospheric CO 2 has increased in the 20 th century, like a thicker blanket Earth s T surf increases like a person under blanket Aerosols cause cooling could it be enough to offset warming? What we don t know Will temperature increase In 20 years? In 100 years? In California? In Siberia? Will sea level rise? Less sea ice? Which species will adapt? What migra7ons will result? Will aerosol changes cause Less rain? Less snow? 5