The earth’s atmosphere and biosphere evolved together over time, the one affecting the other, such that the composition of the atmosphere was strongly influenced by the exchange of gases among them, lithosphere, and hydrosphere. Green plants, through photosynthesis and respiration, have had significant influence on the carbon dioxide, oxygen, and water budgets of the atmosphere. The carbon cycle of the earth according to our current understanding suggests that a near equilibrium existed among sources and sinks for carbon involving the atmosphere, soils, vegetation, animals, oceans, and sediments prior to the industrial age in about 1860. Since that time there has been a rapidly increasing amount of CO2 in the atmosphere, released from storage reservoirs by the propensity of mankind for burning fossil fuels (oil, gas, and coal), cutting of forests, plowing of soils, and manufacturing of cement from limestone.