What are greenhouse gases and where do they come from?
Greenhouse gases are gases which trap infrared radiation from clouds and from the warm earth. Examples are carbon dioxide, and methane. Carbon dioxide occurs naturally through the carbon cycle but it is also now being added by burning fossil fuels and from deforestation, where trees no longer absorb and store the carbon.
Methane comes from melting swamps, tundra and lakes, as well as from cattle farming.