Depends on a lot of factors such as the number of trees and plants the number of people and animals on the planet changes in the environment (whether it natural or manufactured many other....
y dont u google atmosphere composition. its mostly hydrogen and oxygen if i remember correctly. if your doing green house effects then just google green house gas. i donno much about it. p.s. oops its nitrogen and oxygen not hydrogen xD
here i googled it and wikipedia gives me these. Nitrogen (N2) 780,840 ppmv (78.084%) Oxygen (O2) 209,460 ppmv (20.946%) Argon (Ar) 9,340 ppmv (0.9340%) Carbon dioxide (CO2) 387 ppmv (0.0387%) Neon (Ne) 18.18 ppmv (0.001818%) Helium (He) 5.24 ppmv (0.000524%) Methane (CH4) 1.79 ppmv (0.000179%) Krypton (Kr) 1.14 ppmv (0.000114%) Hydrogen (H2) 0.55 ppmv (0.000055%) Nitrous oxide (N2O) 0.3 ppmv (0.00003%) Xenon (Xe) 0.09 ppmv (9x10−6%) Ozone (O3) 0.0 to 0.07 ppmv (0% to 7x10−6%) Nitrogen dioxide (NO2) 0.02 ppmv (2x10−6%) Iodine (I) 0.01 ppmv (1x10−6%) Carbon monoxide (CO) 0.1 ppmv Ammonia (NH3) trace
