How are humans contributing to the amount of greenhouse gases and global warming?
Human beings are contributing to greenhouse gas levels, and to global warming, through the burning of fossil fuels; the cutting and burning of forests; through various agricultural processes, that lead to the build-up of methane and nitrous oxide; through some of the chemicals which are substitutes for Freons, which are now used in air conditioners and refrigerators; and through the production of smog, because smog contains ozone, which itself is a greenhouse gas.
