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3. Early atmosphere ~4.5 billion years ago Mostly Hydrogen and Helium Escaped into space Outgassing of water vapor and CO2 created a secondary atmosphere with some nitrogen As liquid water formed the oceans and CO2 was removed from atmosphere The atmosphere became dominated by nitrogen. ~ 2 billion years ago oxygen increased in the atmosphere because of plant life and photosynthesis. This allowed for the formation of the stratospheric ozone layer which further enhanced conditions for life on Earth.

4. 78 % Nitrogen N2 20.95 % Oxygen O2 0.93 % Argon Ar H2O 0 to 4 % Carbon Dioxide CO2 0 to .037 % (or 370 ppm) Methane CH4 1.8 ppm Nitrous Oxide N2O .3 ppm Ozone 0.04 ppm or 40 ppb) Aerosols (particles) highly variable Click to listen

5. Click to listen By far invisible water vapor is the most important atmospheric greenhouse gas. It is important to realize that water vapor is invisible. The clouds you see in this photo are compose of liquid water droplets formed as water vapor condenses into liquid. When we breathe out our breath contains lots of water vapor. This water vapor can becomes visible water drops if we breath onto a cool piece of glass.

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7. Carbon Dioxide is the second most significant greenhouse gas. Click to listen

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9. Click to listen Methane is another important greenhouse gas. Preindustrial levels were less than half of what they are today. In the early part of the past decade it looked as if methane was stabilizing. More recently is has started to increase again.

10. Low density Click to listen High density

11. Mass - quantity of matter Click to listen

12. Weight = mass x gravity Click to listen

13. Density = Mass/volume Click to listen

14. Pressure = Force/Area 300 lbs or 4 sq inches=75 psi 100 lbs or 0.25 sq inches=400 psi Click to listen

15. Standard Sea Level pressure is: 1 Atmosphere 14.7 psi 1013 milli bars Click to listen

16. Air Pressure (& density) drop by 1/2 for every 5.5 km altitude gain.

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19. Lapse Rate is the temperature drop per kilometer height increase Typically about 6 °C/km = 6 °C/1000m Or About 3 °F/1000 ft Click to listen

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23. Synoptic Weather map Click to listen

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27. Radio Sonde