TAILIEUCHUNG - Lecture Environmental science - Chapter 20: Atmosphere, climate, ozone

This lecture introduces you to atmosphere, climate, ozone. The main contents of this chapter include all of the following: Layers of the atmosphere, composition of the troposphere, structure & temp of atmosphere, global warming, build up of greenhouse gases, nitrous oxides,.and other contents. | Chapter 20 Atmosphere Climate Ozone Layers of the Atmosphere Troposphere (lowest layer) ---------Tropopause Stratosphere --------- Stratopause Mesosphere --------- Mesopause Thermosphere (highest layer @100 km) Composition of the troposphere 78% N2 20% O2 Less than 2% H2O vapor (.01%-4%) Argon gas (1%) CO2 () Trace gases Structure & Temp of Atmosphere Look at Fig. 20-2 and Table 20-1 Troposphere = lowest layer; tropics 10 miles (16km); higher altitudes 5 miles (8km) Water vapor & clouds Greenhouse gases Colder w/ altitude (generally) Pollutants reach top w/in a few days Structure & Temp of Atmosphere cont. Tropopause ---- separate Troposphere from stratosphere Stratosphere - temp increases w/ altitude 40 miles - contains the ozone shield - Ozone absorbs UV radiation from the sun & filters the rays - No precipitation Global warming Global warming occurs when humans contribute too much of these greenhouse gases leading to a small (1-3 degree C) but significant rise in the global average temperature. Analogy – Car on a sunny day The greenhouse effect is natural and important to keep the earth warm enough for life to exist Build up of Greenhouse gases: CO2 Fossil Fuel use Deforestation Methane (CH4) Microbial fermentation (Landfill) Coal and oil deposits Natural gas pipelines Cows (manure) Methane is the second most important green house gas (next to CO2) Nitrous Oxides Biomass burning Chemical fertilizers Fossil Fuel Burning CFC-Chlorofluorocarbons Refrigerants Solvents Pesticides Aerosols (Old) Ozone (O3) Stratospheric ozone is GOOD It shields us from the harmful UVB rays of the sun. Ozone depletion is the thinning of the stratospheric ozone shield (mostly over the South Pole) Analogy – Stratospheric O3 is like sunscreen for the earth. Tropospheric ozone is BAD If we breath it, it causes lung damage It is also a greenhouse gas The Making of Ozone O2 + UVB (280 – 320 nm more energetic) O + O The free O bonds to existing O2 (O + O2) Ozone is made (O3) O2 + UVB O + O ; O + O2 O3 The Destruction of Ozone O3 CFC – chlorofluorocarbons Cl – FC (UV rays breaks bond) The free Cl “attacks ozone” O3 + Cl O2 + (Cl – O) Cl – O is unstable so the bond will break and the Cl will “attack” another ozone molecule Greenhouse Effect Troposphere Traps heat near the Earth’s surface Water vapor, carbon dioxide, methane Globing warming Ozone shield Stratosphere filters UV radiation Oxygen gas, Ozone gas Ozone depletion more UV cancer Where? What Happens? Which gases? Problem? The End

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