FORCING = Heat in – Heat out

Table 2.1: A Summary of Key Greenhouse Gases Affected by Human Activities

Carbon Dioxide CO2 Methane (CH4) Nitrous Oxide (N2O) Chloro-Flouro Carbon (CFC-12)

Pre-Industrial 280 ppmv 700 ppbv 275 ppbv zero

Concentration

Concentration in 355 ppmv 1,714 ppbv 311 ppbv 503 pptv

in 1995

Recent rate of 1.5 13 0.75 18-20

concentration ppmv/yr ppbv/yr ppbv/yr pptv/yr

change per year

(over 1980s) 0.4%/yr 0.8%/yr 0.25%/yr 4%/yr

Atmospheric 50-200 12-17 120 102

lifetime (yrs)