Without a layer of greenhouse gases the earth would experience huge extremes of temperature and would be a hostile place to live. We depend upon greenhouse gases for our survival.
However, long-term measurements of atmospheric carbon dioxide (CO2) concentration have been made at the Mauna Loa Observatory in Hawaii. These data show that the carbon dioxide concentration in the atmosphere is increasing.
This graph is known as the Keeling curve.
The graph below, showing the steady rise in CO2 concentration, is from CO2 Now. (by the way ppm is 'parts per million', a unit of concentration).
This steady rise in CO2 is worrying many people.
Carbon dioxide is not the only greenhouse gas that is increasing in the earth's atmosphere. Concentrations of methane and nitrous oxide are also rising. You can read about the combined warming effect of the earth's greenhouse gases (an index called the Annual Greenhouse Gas Index or AGGI) on the National Oceanic and Atmospheric Administration's website.
This video from NASA shows the output from a high resolution computer model of carbon dioxide in the Earth's atmosphere. It clearly shows how CO2 emissions change during the course of a single year, how emissions are carried around the planet and how plants absorb carbon dioxide through photosynthesis.