1. The Earth’s Atmosphere

2. GasPercent Nitrogen78% Oxygen21% Argon0.93% Carbon Dioxide (CO 2 ) 0.037% Neon, helium methane, ozone… ~0.04% Also water vapor (most near the surface of the earth), dust and pollutants (e.g. sulfur dioxide)

3. 0.039% means 390 ppm (“ppm” = parts per million) Pre-industrial CO 2 level: 275 ppm Present CO 2 level: 390 ppm Safe (?) CO 2 level: 350 ppm A Special Note on Carbon Dioxide present in trace amounts, but important in its effects: a greenhouse gas (GHG) – a gas that is very effective at absorbing (trapping) and emitting radiation as heat (infrared radiation)

4. Why is the atmosphere important? 1.Natural Greenhouse Effect, temperature extremes: warms Earth’s surface, reduces day/night extremes; 2.Ozone layer: protects against damaging ultraviolet (UV) radiation from the Sun; 3.Water Cycle: movement of water - evaporation, transpiration from plants, precipitation - provides for life;

5. Convection cells: Warm moist air rises at equator; Cold dry air sinks at the poles; Gives rise to winds; Heat Energy and moisture: Transfers heat and moisture around the globe, to the poles; Atmospheric Circulation

6. Atmospheric Layers