The greenhouse effect is the heating of the surface of a planet or moon due to the presence of an atmosphere containing gases that absorb and emit

Transcription

1 The greenhouse effect is the heating of the surface of a planet or moon due to the presence of an atmosphere containing gases that absorb and emit infrared radiation

2 The Greenhouse Effect The Met Office Hadley Centre for Climate Prediction and Research

3 electromagnetic spectrum

4 Laws of radiation 1. All objects emit radiant energy 2. Hotter objects radiate more energy per unit area than cooler objects 3. The hotter the radiating body, the shorter the wavelength of maximum radiation

5 Stefan Boltzmann law irradiance = constant x temperature to the 4 th power E* = σt 4 The Stefan Boltzmann law states that the total energy radiated per unit surface area of a black body in unit time (known variously as the blackbody irradiance, energy flux density, radiant flux, or the emissive power) E* is directly proportional to the fourth power of the black body's thermodynamic temperature T (also called absolute temperature)

6 Joseph Stefan Published nearly 80 scientific articles, mostly in the Bulletins of the Vienna Academy of Sciences. He is best known for originating a physical power law in 1879 stating that the total radiation from a black body j* is proportional to the fourth power of its thermodynamic temperature T

7 Ludwig Boltzmann Austrian physicist famous for his founding contributions in the fields of statistical mechanics and statistical thermodynamics. He was one of the most important advocates for atomic theory at a time when that scientific model was still highly controversial.

8 blackbody curves

9 solar constant (S) Solar luminosity divided by the area of a sphere with the radius of the distance between the Sun and Earth solar luminosity = 3.8 x Watts Earth-Sun distance = 1.49 x 10 8 km S = 3.8 x π (1.49 x ) W/m 2

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11 effective, or blackbody, temperature? applying the laws of radiation E* = σt e 4 T e = (E*/σ) 1/4 = (223 / 5.67 x 10-8 ) 1/4 = 251 K = -22 C Present-day global average temperature = 288 K = 15 C

12 the greenhouse effect

13 energy balance

14 near-surface temperature

15 Global Mean Energy Balance

16 lower atmosphere is warmed

17 absorption by greenhouse gases

18 composition of the atmosphere

19 composition of the atmosphere

20 What makes a gas greenhouse gas? Able to absorb infrared light Must have molecular vibration(s) This excludes monoatomic gases as greenhouse gases. (That is why argon, the third most abundant atmospheric constituents is transparent to infrared irradiation) The molecular vibrations must be non-symmetric, i.e. infrared active Homonuclear diatomic molecules only have symmetric vibrations. That s why N 2, O 2 are not greenhouse gases.

21 Major greenhouse gases H 2 O CO 2 CH 4 N 2 O O 3 CFCs SF6

22 Enhanced greenhouse effect When concentrations of greenhouse gases increase, more infrared radiation is returned toward Earth and the surface temperature rises.

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26 IPCC

27 CO 2 Concentrations at Mauna Loa, Hawaii

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34 model sensitivity study

35 Joseph Fourier The greenhouse effect was discovered by Joseph Fourier in the 1820s

36 Remarques générales sur les Temperatures du globe terrestre et des espaces planétaires Fourier's observation that the ground temperature of the Earth is increased because of the existence of the atmosphere; a phenomenon that would become known as "the greenhouse effect". Often considered the foundation of climate change science. Annales de Chimie et de Physique, pp , Tome XXVII, Octobre Paris: Crochard, 1824.

37 John Tyndall measured the infrared absorptive powers of the gases nitrogen, oxygen, water vapor, carbon dioxide, ozone, methane, etc. He concluded that water vapor is the strongest absorber of radiant heat in the atmosphere and is the principal gas controlling air temperature. Prior to Tyndall it was widely surmised, but he was first to prove, that the Earth's atmosphere has a Greenhouse Effect.

38 John Tyndall 1861 John Tyndall, "On the Absorption and Radiation of Heat by Gases and Vapours..." Philosophical Magazine ser. 4, 22: , John Tyndall, "On Radiation through the Earth's Atmosphere." Philosophical Magazine ser. 4, 25: John Tyndall, "On the Relation of Radiant Heat to Aqueous Vapor." Philosophical Magazine ser. 4, 26:

39 Svante Arrhenius In 1896, when he published his greenhouse calculation, Arrhenius was Professor of Physics and Rector at the Stockholm Högskola. He was already famous for showing how dissolved salts separate into charged particles ("ions"). In 1903 he was awarded the Nobel Prize in Chemistry for "the extraordinary services he has rendered to the advancement of chemistry by his electrolytic theory of dissociation."

40 Guy Stewart Callendar From Quarterly J. Royal Meteorological Society 64, 223 (1938).

41 From Quarterly J. Royal Meteorological Society 64, 223 (1938).

42 Gilbert N. Plass

43 Barry Saltzman