Variations in atmospheric composition
Concentration of H2O is highly variable
[H2O] controlled by tropospheric processes
- Evaporation from sea surface
- Condensation leading to precipitation
Concentration of CO2 is varying rapidly
[CO2] affected by many natural processes; human activity led to significant, rapid change in [CO2]
- Prior to industrialization & significant human population growth, [CO2] _ 260 ppm
- In 1958, [CO2] = 315 ppm
- In 1980, [CO2] = 338 ppm
- In 1999, [CO2] = 367 ppm