Why is the composition of Earth's atmosphere still changing?

The composition of the atmosphere is changing today as it has been changing since the earth began to cool and atmosphere formed, just as the climate has gone through periods of heating and cooling. There have been multiple "ice ages", and multiple thawings. Ocean levels have gone up and down. Carbon dioxide has been absorbed by plants and buried for centuries, and carbon dioxide levels have gone back up following volcanic eruptions.

Lately, (in the last hundred years) the levels of carbon dioxide has gone up. Scientists believe that pollution from human activity is changing the atmosphere.

  • Burning of fossil fuels (coal, oil and natural gas) in industry, transport and the generation of electricity, which releases carbon dioxide (CO2).
  • Bad agricultural practices emit methane (CH4), a powerful greenhouse gas.
  • Deforestation has removed the trees that used to take carbon dioxide from the atmosphere.