《环境化学》课程PPT教学课件讲稿（英文版）Unit 7 Climate-Greenhouse Effect

Climate- Greenhouse Effect

Climate-Greenhouse Effect

Greenhouse Bus Glass, the material dative Reemitted longer-wavelength infrare adtion that greenhouse is hort-waveiength visible lighi 如: made of1) transmit short-wavelength visible light, 2) 62° absorbs and 图酚图签 redirects the longer wavelengths of energy. These two aspects make the greenhouse warmer Absorption of light energy (and reemission) at tonger wavelengths than outside air ainly carbon dioxide-do for the earth's atmosphere and temperature surface what the glass does for a greenhouse

Greenhouse Glass, the material that greenhouse is made of, 1) transmit short -wavelength visible light, 2) absorbs and redirects the longer wavelengths of energy. These two aspects make the greenhouse warmer than outside air temperature

Greenhouse effect of the atmosphere Light from the sun includes the entire visible region and smaller portions of the adjacent UV and infrared regions Sunlight penetrates the atmosphere and warms the earth's surface Longer wavelength infrared radiation is radiated from the earth's surface The gases in the atmosphere that act a considerable amount of the like glass in a outgoing IR radiation is absorbed by greenhouse are called gases in the atmosphere and greenhouse gases. reradiated back to earth

Greenhouse effect of the atmosphere • Light from the sun includes the entire visible region and smaller portions of the adjacent UV and infrared regions. • Sunlight penetrates the atmosphere and warms the earth’s surface. • Longer wavelength infrared radiation is radiated from the earth’s surface. • A considerable amount of the outgoing IR radiation is absorbed by gases in the atmosphere and reradiated back to earth. The gases in the atmosphere that act like glass in a greenhouse are called greenhouse gases

Natural greenhouse effect ATMOSPHERE Infrared Radiation Solar Radiation The natural greenhouse effect causes the mean temperature of the earth's surface to be about 3 3oc warmer than it would be if natural greenhouse gases were not present

Natural Greenhouse effect The natural greenhouse effect causes the mean temperature of the Earth's surface to be about 33oC warmer than it would be if natural greenhouse gases were not present

Enhanced greenhouse effect Outgoing infrared adagio rred actaeon Normal Incomin C Re-radiated radiation heat creased Earth's surfac Normal concentration Increased concentration When concentrations of greenhouse gases increase, more infrared radiation is returned toward the earth and the surface temperature rises

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

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 n2, 02 are not greenhouse gases

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 N2, O2 are not greenhouse gases

What are the major greenhouse gases? H20 CO2 CH4 N2O ·O3 CFCS SF6

What are the major greenhouse gases? • H2O • CO2 • CH4 • N2O • O3 • CFCs • SF6

Absorption of terrestrial radiation by H20 and CO2 Infrared radiation emitted from Earth's surface atmosphe Absorbed in window (unabsorbed atmosphere by H,O or cO, H,O absorption spectrum CO, absorption spectrum 4.000 8.000 12,000 16,000 20,00 Wavelength(nm Atmospheric window: 8000-12000nm

Absorption of terrestrial radiation by H2O and CO2 Atmospheric window: 8000-12000nm

What determines the contribution of a greenhouse gas to global warming? Concentrations H20 and Co2 are the two biggest contributors to the atmospheric warming because of their higher concentrations Lifetime The longer-live a gas is, the higher the contribution e g N20 contribution> CH4 Effectiveness as an infrared absorber For example, cFc-11 and CFC-12

What determines the contribution of a greenhouse gas to global warming? • Concentrations – H2O and CO2 are the two biggest contributors to the atmospheric warming because of their higher concentrations. • Lifetime – The longer-live a gas is, the higher the contribution. e.g. N2O contribution > CH4 • Effectiveness as an infrared absorber – For example, CFC-11 and CFC-12

Radiation emitted from Earth's surface CFC-11 and CFC-12 Region unabsorbed are effective by natural atmospheric gases infrared absorber CF CL absorption The absorption spectra of CFC-11 and CFC-12 coincides with the atmospheric window CFCL, absorption 8,000 10,00012,000 Wavelength(nm)

CFC-11 and CFC-12 are effective infrared absorber The absorption spectra of CFC-11 and CFC-12 coincides with the atmospheric window