When two Englishmen meet the first thing they talk about is the weather Dr Johnson

1. Weather and the Environment When two Englishmen meet the first thing they talk about is the weather Dr Johnson David Leadley P544

3. Weather and Climate Weather / meteorology – study of atmosphere and atmospheric processes, daily variation Climate / climatology – seasonal average of weather at some location Climate change – long term variation in climate … and the environment Environment – conditions for life or growth Sustainability – ability of the environment to function indefinitely, despite stresses imposed by human society

4. Non-sustainable Human behaviour • Using non-renewable resources as if supplies were unlimited eg. fossile fuels • Using renewable resources faster than they can be replenished eg. fresh water • Polluting the environment as if its capacity were unlimited eg. CFCs, CO2, acid rain • Increasing population, despite Earth’s finite ability to support us

5. Earth from the Space Shuttle “For the first time in my life I saw the horizon as a curved line. It was accentuated by a thin seam of dark blue light – our atmosphere. I was terrified by its fragile appearance.” Ulf Merbold, astronaut

6. Components of the climate system Atmosphere Greek for vapour ball Hydrosphere oceans Cryosphere snow and ice fields Biosphere life and human influence

9. Gas Chemicalcomposition Percent(by volume of dry air) Nitrogen N2 78.08 Oxygen O2 20.95 Argon Ar 0.93 Neon Ne 0.0018 Helium He 0.0005 Hydrogen H2 0.00005 Xenon Xe 0.000009 Composition of the Atmosphere(1) Permanent Gases

10. Substance Chemicalcomposition Percent(by volume of dry air) ppm(parts per million) Water vapour H2O 0 to 4 ------- Carbon dioxide CO2 0.035 350 Methane CH4 0.00017 1.7 Nitrous oxide N2O 0.00003 0.3 Ozone O3 0.000004 0.04 Particulate matter ------- 0.000001 0.01 Chlorofluorocarbons (CFCs) ------- 0.00000001 0.0001 Composition of the Atmosphere(2) Variable Gases

11. Origin of the atmosphere • Earth formed 4.6 billion years ago, without atmosphere • Outgassing from volcanoes of N2, CO2, H2O, H2, Cl2, SO2, CH4 , but not oxygen • Water condensed in oceans, H2 escaped, acid rain weathered rocks.CO2 at 100 times present level – larger greenhouse effect kept the atmosphere warmer and compensated for a 30% weaker Sun • Emergence of life in oceans produced O2and sequestered CO2 in rocks • Once O2 was present O3could be formed,giving UV protection and allowing life to expand its range

12. Atmospheric Oxygen

14. Surface Albedo (%) Surface Albedo (%) Snow 79-95 Dark Soil 5-15 Ice 30-40 Grassy Field 10-30 Thick Clouds 60-90 Forest 5-15 Thin Clouds 30-50 Water 10 (avg.) Wet Sand 20-30 Venus 78 Dry Sand 35-45 Mars 17 Concrete 17-27 Moon 7 Tarmac 5-10 Earth 30 Albedo from various surfaces

16. Planetary temperature profiles

17. Atmospheric profile of Venus At surface Ts=740 K ps=92 bar

18. Atmospheres of Gas Giants

19. Nitrogen 90-97 % Hydrocarbons Methane 2-10 % Acetylene 2.2 ppm Ethylene 10.1 ppm Ethane 13 ppm Propane 0.7 ppm Nitriles Hydrogen cyanide 160 ppb Cyanoacetylene 1.5 ppb Titan’s Atmosphere

21. Summary of Lecture 1 • Introduction to Earth’s atmosphere • origin • composition • structure • comparison with other planets • Stefan’s law